This paper investigates the effects of crosslinking methods on the incorporation of graphene oxide (GO) in carboxylated nitrile butadiene rubber (XNBR) in the process of producing nanocomposites for chemical-resistant protective clothing and gloves. The novel aspect of the study is a comprehensive approach involving both unmodified GO as well as GO that was carboxylated to increase its affinity to XNBR and to facilitate its application. The nanostructure of XNBR composites was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Fourier transform infrared spectroscopy (FTIR) was used to elucidate the chemical structure of the composites. Thermal stability studies were performed using differential scanning calorimetry (DSC). The barrier properties of the composites were determined based on swelling, crosslinking density, and permeation by mineral oils. The mechanical tests included resistance to puncture and abrasion, stress at strain, and tensile strength. Contact angle was measured to determine the degree of hydrophobicity of the obtained composites. AFM and SEM images revealed the effects of different curing agents (sulfur, magnesium oxide, or a hybrid system) as well as GO type on the surface morphology of XNBR composites. The type of curing agent was found to affect the kind of crosslinks formed and their spatial network structure, as confirmed by FTIR. The DSC curves showed that the crosslinking methods of XNBR did not affect glass transition temperature, but led to large changes observed in the temperature range of 130–220 °C. The type of crosslinking method affected the degree of swelling. It was found that the incorporation of carbon nanofillers led to an improvement in the abrasion and puncture resistance as well as tensile strength of XNBR composites. The water contact angle of the composites indicated hydrophobicity. The properties of XNBR composites containing GO revealed their substantial application potential in protective clothing.

A new method has been proposed and verified to measure the viscoelastic properties of polymers by nanoindentation tests. With the mechanical response of load–displacement curves at different loading rates, the parameters of creep compliance and relaxation modulus are calculated through the viscoelastic contact model. Dynamic thermomechanical analysis (DMA) tests are conducted to compare the results by the proposed technique. The results show that the correlation coefficients between DMA tests and the new method are above 0.9 in the entire range, which verified the feasibility of the method. The loading curves fitted by the model are identical to the experimental curves within the discrete points and so it shows that this technique is more suitable for general linear viscoelastic materials. Numerical creep tests are carried out to examine the effectiveness of the proposed method by input the Prony series calculated by the three-element Maxwell model and the viscoelastic contact model. The good agreement shows that the proposed technique can be applied in practice.

Torsion testing machines are widely used either to measure the strength, stiffness and stress-strain properties of materials or to replicate real-life service conditions. In this paper, a novel experimental method is presented, based on the development of a dedicated steel structure to be used in conjunction with a universal testing machine. This equipment allows applying cyclic in-plane torsion loads on disk-shaped components. The proposed approach aims to enable the assessment of stiffness and damping properties on specimens enabling the application of higher loads in comparison with the traditional machines. Specifically, dynamic trials were performed by attaching the composite specimens and the steel structure to the testing machine, such that the uniaxial controlled displacements can be used to exert the desired cyclic loads onto the specimen. Both torsional stiffness and energy loss were measured from the steady-state load-displacement hysteresis cycles. Amplitudes of sine signals, from 0.05 to 0.2 mm, and a frequency ranging between 1 and 20 Hz, were used in the experiments. The results are presented comparing the behaviour of two polymer matrix composites, with the same number of identical laminae, but characterized by different stacking sequences, namely unidirectional and quasi-isotropic configurations.

New materials are currently being developed for applications in transformer design. With the useful life of transformers now determined by solid insulation conditions, a better understanding of aging kinetics is important in order to improve electrical system management and planning from the technical and economic points of view. This paper summarizes an investigation of the effects of impregnating aramid and cellulose/aramid papers (Nomex 410 and 910) with insulation fluids (Nynas Polaris and Luminol Tri) at thermally accelerated conditions (170 °C) on their mechanical properties. It was found that Nomex 410 (100% aramid) showed only a small change in tensile strength (∼5% decrease) after accelerated aging (around 7,500 h). However, its elongation capacity was significantly reduced (∼45–70% decrease for dry and wet Nomex 410, respectively) by the end of the aging process, probably due to hydrolysis. In addition, the interaction between water and aramid hydrogen bonds at high temperatures produced the rupture and then, the randomly rebuilt of these bonds in meta-aramid fibres, thereby reducing its plastic deformation capacity. In the case of Nomex 910 (aramid enhanced cellulose), its mechanical properties were maintained for a longer time than those of thermally upgraded Kraft paper (TUK), as measured by the retained percentage of tensile index. However, when the tensile index was used instead of the retained percentage, TUK showed a higher tensile index value than Nomex 910 during the initial stage, while the values for both papers became similar during the second stage. It is only at the end of the aging process that Nomex 910 presented an advantage over TUK paper due to the addition of the aramid fibres. It was also found that the inception fractures in Nomex 910, as a fibrous layered composite paper, start in the weakest part of the composite, probably in the central cellulose layer. The fracture line follows the weakest path, avoiding the aramid fibres. The results presented in this paper can be used as a benchmark for improving our understanding of aging and changes in the mechanical properties of these relatively new materials used in the solid insulation of power transformers. A better understanding of the aging characteristics (thermal degradation) of aramid-based papers should help better assess the condition of the new generation of power transformer fleets.

In additive manufacturing, polymer composites are used for setting tailored properties. Short glass fibers can be used as fillers for polyamide 12 for enhancing stiffness or tensile strength as well as for reducing shrinkage. In this paper, the effects of short glass fibers on polyamide 12 concerning powder properties, process behavior and part properties in laser beam melting of polymers (SLS) are investigated. It could be shown that by increasing the short glass fiber content powder properties as well as part properties are immensely affected. By adding glass fibers, powder properties, like flowability and diffuse reflection decrease. The isothermal crystallization changes resulting in a narrower processing window. Concerning mechanical properties, short glass fibers allow for a higher stiffness until a critical limit of filler concentration within this study is reached, after which the tensile strength decreases. The elongation of break decreases by rising the filler content.

The low velocity impact behavior of basalt/epoxy composites, seen as an eco-friendly replacement of glass-epoxy composites, has not been studied systematically so far. Here, the elastic elasto-plastic properties, strengths, intralaminar and interlaminar fracture energies were determined. The intralaminar energies were determined using compact tension and compression tests. The elasto-plastic properties needed in the plastic potential were determined using off-axis test. These properties are used in Finite Element (FE) code with an elasto-plastic damage model developed earlier to simulate the impact response of cross-ply laminates basalt/epoxy laminates. Low velocity impact (LVI) experiments at 10 J, 20 J and 30 J are performed on these composites. The FE simulation is successful in capturing force, energy, deflection histories and damage zones showing a close match to the experiments. A comparison of impact force history and damage area (ultrasonic C-scan) of basalt-epoxy laminates with glass epoxy laminates having same volume fraction shows nearly similar peak forces but the major axis of the ellipsoidal damage zone was bigger in glass/epoxy laminates.

In this study, poly (ε‐caprolactone) (PCL) scaffolds were printed and reinforced, simultaneously, with biodegradable poly glycolic acid (PGA) suture yarn, as a continuous reinforcing fiber, in the Fused Deposition Modeling (FDM) 3D printing process. Albeit PCL is a suitable material for biomedical applications, its low mechanical properties, and low degradation rate have limited its usage. A biocompatible suture yarn was used as the reinforcing material to enhance the mechanical properties and biodegradation characteristics, via an innovative method of continuous fiber embedding in the FDM process. The reinforced PCL samples were 3D printed with the setting porosity value of 60% and 0°/60°/120° lay-down pattern. The mechanical and biological properties of the scaffolds were tested to prove the effectiveness of the produced scaffolds for bone substitute purposes. Mechanical properties assessments showed that with a 22 wt % suture yarn content in the 3D printed PCL scaffolds, the tensile strength, and elastic modulus remarkably increased up to 374% and 775%, respectively. The degradation of the reinforced PCL was 20 times higher than that of the non-reinforced PCL samples, after ten weeks, dominated by the fiber degradation phenomenon. After three days of cell culture, the proliferation assay of the built scaffovd the non-toxicity of the reinforced PCL.

Multi-walled carbon nanotube (MWCNT) reinforced polylactide (PLA) nanocomposites were injected molded into a mold with micro needle patterns. In order to alleviate the hesitation effect caused by an increased melt viscositgy of PLA/CNT nanocomposites, the effects of the injection speed and holding pressure on the replication property were investigated. The effects of MWCNTs on the crystallization, thermal behavior, replication properties, replication and surface properties of micro injection molded PLA/CNT nanocomposites were investigated. An analysis of crystallinity and thermal behavior indicated that the MWCNTs promoted the unique α’ to α crystal transition of PLA, leading to an enhancement of surface modulus and hardness, as measured using a nanoindentation technique. The specific interaction between PLA and MWCNTs was characterized using an equilibrium melting point depression technique. Furthermore, the MWCNTs increased the activation energy for thermal degradation of PLA due to the physical barrier effect. The improved replication quality of the microfeatures in the PLA/MWCNT nanocomposites has been achieved by elevating injection speed and holding pressure, which enhances the polymer filling ability within the micro cavity. A replication ratio greater than 96% for the micro injection molded PLA/CNT nanocomposites were achieved at holding pressure of 100 MPa and injection speed of 120 mm/s. This study shows that processing conditions significantly influence the replication and surface properties of micro injection molded PLA/CNT nanocomposites.

Vibration welding technique has been widely used to weld molded surfaces parts produced by injection or compression molding techniques. However, the majority of early studies used machined surfaces to eliminate the complication associated with molded surfaces. Different process parameters such as the welding pressure, frequency, and amplitude have been investigated to determine their optimal values that maximize the welding strength. However, some other parameters such as joint design and the welding interface preparation were leftover for real application test or for technology transfer studies. Most of molded parts from semi-crystalline materials and their composites usually have skin layer that was exposed to thermal history differs from that of the core. Moreover, the amount and the orientation of fibers in the skin layer differ from that of core and shell regions. Therefore, this work investigates and explores the effect of the molded surfaces with skin on tensile strength of vibration welded butt joints made from polybutylene terephthalate reinforced with 30% glass fiber (PBT GF30). The effect of fibers orientation on the welded joint strength has been also investigated.

Supramolecular structure can be formed using noncovalent interactions based on the self-assembly processes. DNA is a good example for supramolecular materials because it is able to form supramolecular structure by forming specific hydrogen bonds between its base pairs. Moreover, DNA as an anionic medium can bind with oppositely charged materials to form complex structures of various shapes and properties. This work is focused on a foam complex that is formed between negatively charged DNA and positive chitosan. Various characterizations —Fourier transformed infrared spectroscopy (FTIR), Small and Wide-angle X-ray scattering (SAXS and WAXS), scanning electron microscope (SEM), texture analyzer and differential scanning calorimetry (DSC) — are used to study the properties of this dried scaffold. The FTIR spectra presented the chemical structure of DNA and chitosan. While the SAXS power law decay has revealed that an increasing of chitosan content smoothens the surface of the structure, on the other hand, the roughness is much higher when the DNA content is increased. The melting point of the foam from the DSC scan has been identified. The mechanical property of foam is suitable for the application of scaffold, and there is no cytotoxicity of foam to the cell. It is expected that this type of biomaterial could be used in several applications such as functional material and as a drug delivery material.

In the process of waterflooding development, it is of great importance to prevent the clay from hydration swelling and migration dispersion for protecting the formation and improving the water flooding efficiency. For those reasons, we successfully synthesized a cationic clay stabilizer (HBP-QAT) through melting polycondensation and cationic modification with maleic anhydride, diethanolamine, epichlorohydrin, triethylamine, and trimethylolpropane as monomers and p-toluene sulfonic acid as a catalyst. The chemical structure, cation degree, and molecular weight of HBP-QAT were studied by using FTIR, 1H NMR, sodium tetraphenylborate (STBP) back titration, and gel permeation chromatography (GPC). The obtained results showed that HBP-QAT was a hyperbranched unsaturated polyester amide with a low molecular weight and a high cation degree, with corresponding values of 28400, and 44.2%, respectively. The clay stability and durability of HBP-QAT were evaluated by linear anti-swelling, water flushing, and cutting rolling recovery tests. The obtained results showed that HBP-QAT has an excellent anti-washing capacity and a long-term inhibition effect. The initial anti-swelling rate of 1.0 wt% HBP-QAT reached 92.37%, and the anti-swelling rate of 1.0 wt% HBP-QAT also remained at 85% after flushing 10 times with water. Besides, the two cutting rolling recoveries exceed 72%. Most importantly, the inhibition mechanism of HBP-QAT was studied by FTIR, zeta potential, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and contact angles analyses, and thus we proposed an inhibition mechanism, presenting as follows. HBP-QAT inhibited the clay hydration swelling by neutralizing negative charges on the surface of the clay particles to compress the electric double layer, strongly adsorbing on the surface of the clay particle, and forming a waterproof polymer membrane, restraining water of intrusion into the clay interlayer.

The purpose of this research was to develop a novel, multifunctional apparatus that makes possible to carry out two common tests of woven fabrics and flexible sheet-like materials, namely the shear and the yarn-pull out test. We designed an apparatus that can be mounted on a universal load machine and makes possible to test the materials rapidly and precisely. In this paper we introduce the apparatus and the related simple shear and yarn pull-out test methods, as well as the accuracy and reproducibility of the test results obtained. We carried out cyclic shear and yarn pull-out tests on plain and panama weave materials. We found that the relative deviations of the common shear (G, 2HG, 2HG5) and yarn pull-out parameters were around 5–9% in most cases that confirms the repeatability of the test method. With our method, one can carry out these tests without an expensive, dedicated test device.

Two main issues are essential nowadays for practitioners in the field of polymeric materials: how a polymer will behave under dynamic loading conditions and for how long a polymer is reliable. In this sense, the time-temperature superposition principle was applied to the main viscoelastic properties (E′, E″ and tan δ) of a series of polyurethane coatings (PU-DEG-TMP) tested for mechatronic devices. Polyurethanes are derived from an ester glycol (poly(ethylene adipate) glycol), an aromatic diisocyanate (4,4′-dibenzyldiisocyanate) and di/trifunctional chain extenders - diethylene glycol (DEG) and trimethylol propane (TMP). Despite polyurethane intrinsic rheologic complexity, the moduli/loss factor curves superimpose well over several decades of reduced frequency at the glass transition temperature (Tg), 0 °C and 15 °C, the last temperature being considered the midpoint of the practical testing range. Three criteria were for checking the applicability of the time-temperature superposition: the Cole-Cole plot, the similarity between the aT calculated from both moduli (E′, E″) and the visual appearance of the final master curve. The presence of both hydrogen bonding and chemical joint points, along with some dangling chains put in a broader context the discussion of the microstructural features resulted from the application of the William-Landell-Ferry (WLF) equation.

The main objective of our research was development of a modified poly glutamic acid (PG) films by polylysine (PL) at different PL content (0, 2, 4 and 6%) as a microbioreactor to growth and protect Gamma-aminobutyric acid (GABA) producing bacteria. The addition of PL groups between the PG backbones was completely corroborated using FTIR analysis. Scanning electron micrographs confirmed the high changes in the microstructure of PG films by PL. Density, thickness, moisture content, L* (lightness), b*(yellowness-blueness), WI (whiteness index), opacity, and elongation at break were increased with increasing the PL content. Whereas ΔE (Total color difference) and tensile strength were decreased, simultaneously. The change of water vapor permeability and a* (redness-greenness) value of PG-PL were independent from PL content. The PG-PL films were active packaging material against food borne pathogens (i.e. Bacillus cereus and Escherichia coli). But they had not any side effects on viability of probiotic bacterium (i.e. Lactobacillus brevis G42) after drying process. It is inferable that PG-PL is a suitable candidate for the development of edible coating and film with high antimicrobial properties against food borne pathogen without any side effect on probiotic viability.

In this study ab initio calculations, molecular dynamics (MD) and Monte Carlo (MC) simulation techniques are used to investigate the structural properties of triptycene based polymers of intrinsic microporosity (PIMs), consisting of polyimide branched with the side groups: C4H9, C3H7, CH3 and CF3, to evaluate their performance as polymeric membrane for separation of gases, O2, N2, CO2, CH4 and H2S, which are the constituents of natural gas and their separation is of high industrial interest. In the course of MD simulation, initially, the branched polyimide membranes are built to obtain the PIMs' model. Then the low-density membrane models undergo a consecutive simulation procedure of compression and relaxation to achieve the experimental density of equilibrated membrane. The structure of the constructed membranes is analyzed by calculating: dihedral angles, radius of gyration, fractional free volume, accessible free volume, cavity size distribution, and surface area. The behavior of the membranes against penetration and permeation of the studied gases is determined by evaluating the diffusion and solubility coefficients of the gases and by employing MD and MC simulation techniques, respectively. Comparison of the structural properties of the membranes shows that the PIM membranes with larger side branch groups in their polymeric chain structure are more rigid and therefore, due to restriction in chain packing and cavity formation between polymer chains, the free volume in the membrane's structure increases which as a result would promote the diffusion and permeation of gases into the membrane, where, the obtained results indicate that the membrane with C4H9, as the largest side branch in its polymer chain, has the greatest diffusivity and permeation. Also, the highest selectivity for all studied binary gas mixtures is manifested by the PIM membrane with C4H9 at its side branch, however, for (CO2/CH4) and (H2S/CH4) binary mixtures CF3 as the side branch of PIM membrane represents an acceptable selectivity. The obtained results illustrate that in addition to the membrane free volume, other parameters are influential in gas separation by these polymeric membranes which require further consideration. These parameters include gas adsorption, specific surface area of the membrane for adsorption, the size of gas molecules and their interaction with the PIM membranes which need to be investigated and discussed in the light of the obtained results. To the best of knowledge, based on a thorough investigation of the literature, no similar work can be cited which includes detailed properties of PIM membranes at the atomic scale by using quantum mechanical and simulation techniques in order to elucidate the behavior of PIMs for gas separation.

Shape memory polymers (SMPs) based on polynorbornene (PNB) was prepared and modified by In-situ reactive thermoplastic polyurethane (TPU). Analysis shows that the TPU formed in PNB matrix slightly decreases Tg of PNB from 24.1 to ca. 23.4, which is beneficial to study the shape memory performance at room temperature. A small amount of TPU can be uniformly dispersed in PNB matrix to form interpenetrating network structure, which can significantly toughen and strengthen PNB. Simultaneously, the interpenetrating network can replace the physical entanglement of part of the PNB, increase the free volume among the molecular chains of PNB, make shape fixing easier, and reduce energy consumption in overcoming friction during the recovery process. Therefore, the PNB/TPU composites have higher shape fixing ratio and recovery ratio than PNB. When the content of TPU in PNB matrix is lower, the interpenetrating network of chain entanglements is formed with no phase separation; therefore, the improvement of shape memory performance is remarkable.

In this work, two polyesters and four copolyesters were studied. All materials were synthesized to obtain the monomers dedicated for thermoplastic polyurethane elastomers. For this type of PUR, the monomers should characterize by appropriate selected physicochemical properties and macromolecular structure distribution, which depends on synthesis conditions. The study of chemical structure with extensive and knowledgeable analysis of formed macromolecules of synthesized bio-based copolyesters was conducted with the use of FTIR and 1H NMR spectroscopy and MALDI-ToF mass spectrometry. The results allowed to propose the majority of probable chemical structures of macromolecules formed during synthesis. Moreover, the impact of the structure on the thermal stability of the obtained copolyesters was also determined with the use of thermogravimetric analysis. The temperature of the beginning of thermal decomposition equaled even 330 °C. Furthermore, the results of DSC-TG/QMS coupled method confirmed that all prepared polyesters degraded by α and β-hydrogen bond scission mechanisms.

Tissue engineering uses some engineering strategies for the reconstruction and repair of the compromised tissues, among which the use of biomaterials as an alternative to conventional transplants is significant. However, not many research has been developed on the use of biopolymer nanostructure microanalysis and calcium phosphate composites of carbon apatite in PLA as scaffolds for tissue regeneration. In this work, poly (lactic acid) filaments with 5% and 20%, carbon apatite (cHA) were microanalysis to produce a 3D printing scaffold. The scaffolds were characterised by the Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) techniques, thereby making it possible to notice a good load dispersion. The microstructural analysis of the scaffolds was carried out by computerised micro-tomography to determine the roughness, morphological parameters of pore size distribution, porosity, as well as better visualisation of the distribution of particles. A computational in vitro and microanalysis tests to assess the biocompatibility viability of the PLA/cHA structure with a variation of scaffold geometry to evaluate their effects on morphological, physicochemical and mechanical properties were also carried out. The characterisation of Ca and P release assays were observed for longer incubation times and the dynamic condition control to simulate the stresses suffered by the biomaterial exerted by the flow of fluids was achieved. The results obtained indicated that the micrographs of the cross-sections of the scaffolds showed a flatness in the loaded material when compared to the 100/0 PLA. Furthermore, the apparent porosity of 5% and 20% of cHA scaffolds gave a porosity percentage of approximately 62% and 41% respectively. The reduced summit height, reduced valley depth and the percentage upper and lower bearing area difference of the samples are 16.33 nm, 9.62 nm and 75.07% respectively. The morphological characterisation surface roughness analysis and tolerance insertion gave a favourable reduced porosity result for the composite scaffolds with 5% of cHA. Hence, this work will assist biomaterial industries in the development of biomaterials which have been engineered with biological systems to meet medical purposes.

The progress in new surface modification techniques towards the manufacture of tailored latex articles is faced with the requirement of new characterization techniques to determine the tribological properties of elastomer surfaces. Thus, the present study aims at the characterization of friction properties of commercially available medical gloves to assess their donning performance. The experimental design of the friction test method involves a linear movement of the glove sample across selected counterpart materials. In the first step, bio-tribological studies with a panel are carried out enabling an objective evaluation of the donning properties of gloves. These results are compared to the coefficient of friction of the gloves against various skin equivalents including polymer based materials, glass and biological tissue. In terms of skin friction, a high correlation between human skin and the biological skin equivalent is obtained. However, in contrast to bio-tribological studies, the friction experiments with biological tissue benefit from high reproducibility and low standard deviation. With the established test method the influence of state-of-the-art surface functionalization processes (chlorination and polymer-based coatings) and lubricants (cornstarch) on the friction properties of medical gloves is investigated in order to evaluate crucial process and surface parameters for low surface friction against human skin.

The thermoplastic vulcanizates (TPVs) of Polylactide (PLA)/Epoxidized natural rubber (ENR) were prepared by dynamic vulcanization technology. The processing torque, crosslink density, morphology of PLA/ENR blends, and PLA's molecular weight during the processing were investigated by HAAKE rheometer, swelling measurement, scanning electron microscopy (SEM), and gel permeation chromatography (GPC). It was found that the vulcanization of ENR completed at the turning point after torque peak. After the turning point, the torque and crosslink density decreased with the processing time increasing. Moreover, the morphology of PLA/ENR blends showed bi-continuous structure during the dynamic vulcanization processing, and the phase size of PLA/ENR was increased with processing time and temperature. GPC results showed PLA degradation mainly happened after torque turning point. Thermal gravimetric analysis (TGA) results indicated that some parts of PLA would graft on ENR during processing, and the higher the processing temperature, the more the PLA was grafted.

Dioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.

This paper provides details of a new test rig design and methodology intended for, and successfully applied to, measuring the gear wear rate and performance of polymer composite gears under both dry and lubricated conditions. One of its unique contributions is that it continuously measures the gear wear rate, a feature essential for understanding polymer gear behaviour. While sharing some concepts with the traditional back-to-back test configuration used for steel gears, the new method introduces a rotary freedom to the block supporting the polymer gears under test. This block rotates if the gear tooth thickness is reduced, which aids control of the test load. The gear surface wear rate is recorded continuously by using a capacitance transducer to measure the pivot block motion. A second unique contribution of the new test method involves splitting the support block so that controlled misaligned gear engagements (not reported in other designs) can be introduced and subsequent changes to wear behaviour studied. The paper first outlines the test rig concepts and design before discussing in more detail the gear wear rate measuring principles, the methods of centre distance adjustment and the achievement of virtually constant gear loading. Finally, a selection test results are presented in summary to further validate the new test method and illustrate potential applications.

Enhancement of thermal properties of epoxy resins was achieved by incorporation of polybenzimidazole fibermats filled with carbon nanomaterials, prepared by the solution electrospinning technique. Different type of carbon nanostructures (carbon nanotubes, graphite flakes, graphene nanoplatelets and carbon black) were compared as fillers in polybenzimidazole fibers. The carbon-PBI-fibermats showed remarkable thermal transport properties and therefore, they were studied as thermal reinforcement material for epoxy composites. Mechanical and thermal properties of produced composites were evaluated and the effectiveness of different types of carbon fillers examined. Results showed that the produced carbon filled fibermats can be used effectively as a thermal reinforcing material in epoxy resins, offering several advantages.

Although applied for several decades, production of hollow plastic parts by extrusion blow molding (EBM) is still over-dimensioned. To overcome this issue, a thorough investigation of the process-structure-property relationship is required. In this study, the local process-structure-property relationship for high-density polyethylene EBM containers is analyzed with differential scanning calorimetry and dynamic mechanic analysis microindentation. Local process-dependent crystallinity and complex modulus data at various processing conditions are supplemented with wide-angle X-ray diffraction and transmission electron microscopy (TEM). The crystallinities and the complex moduli clearly show lower values close to the mold side than at the inner side and the middle of the cross-section, which reflects the temperature gradient during processing. Additionally, the orientation of the polymer chain (c-axis) reveals a low level of biaxiality with a slight tendency towards transverse direction. The biaxiality increases for low mold temperature and high draw ratio. Finally, biaxiality is confirmed with TEM, which reveals no preferred lamellar orientation.

The temperature-dependent visco-hyperelastic-viscoplastic behavior of poly(vinylidene fluoride) is investigated and modeled. The proposed mathematical formulation of the visco-hyperelastic element is constructed using a generalized Maxwell model consisting of non-linear springs and viscous dampers in series with a viscoplastic element. The Yamashita and Kawabata strain energy function is considered for modeling the hyperelastic response of the non-linear springs’ elements. The viscoelastic response is represented by the Prony series invoking the time-temperature correspondence principle and employing the Arrhenius equation to define the shift factors. The viscoplastic flow rate is defined by a phenomenological model activated when the Frobenius norm of the deviatoric portion of the Cauchy stress exceeds the material yield stress. The material parameters are calibrated from stress relaxation and monotonic tensile tests performed at different temperatures. Model predictions showed good agreement with the experimental results.

Cross-linked polyethylene (XLPE) insulated power cables are widely used in transmission and distribution networks. The enhanced localised electrical field/stress can result in surface discharges (SD), i.e. partial discharges on the surface of the dielectric. To measure discharges, very low frequency (VLF-0.1 Hz or lower) excitation has emerged as an attractive alternative to the conventional power frequency (PF- 50/60 Hz) testing as it significantly reduces the required reactive power from the test supply. As the discharge process mainly resulted from the enhanced electric stress; it is necessary to understand how the electric field distributes on the XLPE dielectric surface when it is exposed to a high voltage AC excitation. In this study, the distribution of surface electric field before, during and after a PD event at VLF and PF test voltage is investigated. Finite element analysis (FEA) based numerical simulation shows that the space charge dynamics cause the differences in the field distribution and supports the experimental results.

This article presents an experimental investigation into the adhesion between aluminum and epoxy nanocomposites reinforced with multi-walled carbon nanotubes (MWCNT). The nanotubes are dispersed in epoxy chemically with the aid of a surfactant, rather than mechanically via high shear mixing or ultrasonication. Four MWCNT weight fractions are considered viz. 0%, 0.1%, 0.5% and 1%. The adhesion with aluminum is tested via end-notched flexure tests conducted on specimens consisting of Aluminum strips adhered together with various epoxy nanocomposite glues. The best results are obtained for 1% MWCNT, where the tests show a notable increase in adhesion, evidenced by an intact bond despite considerable plastic deformation of Aluminum. However, the peak load capacity is seen to be not enhanced. The higher adhesion with 1% MWCNT addition is seen to successfully suppress the brittle debonding failures even at very high levels of adherend plasticity. For this weight fraction the overall response is highly ductile involving shearing of the glue and is desirable for engineering applications. Despite promising results, the surfactant itself is seen to be not very effective as a dispersing agent for the epoxy resin considered here.

The impact of the additive 1,8-diiodooctane on the morphology of bulk-heterojunction solar cells based on the systems P3HT:PC71BM, PTB7:PC71BM and PTB7-Th:PC71BM is studied using a combination of Small Angle Neutron Scattering (SANS) and Atomic Force Microscopy (AFM). The results clearly show that while in the P3HT:PC71BM system, the additive DIO promotes a slight coarsening of the phase domains (type I additive), in the systems PTB7:PC71BM and PTB7-Th:PC71BM, DIO promotes a large decrease in the size of the phase domains (type II additive). SANS is demonstrated as being particularly useful at detecting the minor morphological changes observed in the P3HT:PC71BM system, which can be hardly seen in AFM. This work illustrates how SANS complements AFM and both techniques when used together provide a deeper insight into the nanoscale structure in thin organic photovoltaic (OPV) device films.

In this study, the stick-slip mechanism of ABS resin friction noise and the effect of different lubricants on the friction noise were investigated by means of friction coefficient test instrument and self-designed noise test method. It was found that different types of lubricants have different effects on ameliorating the noise and stick-slip phenomena of ABS material. As the content of lubricant increased, the friction noise and stick-slip phenomenon of ABS were reduced. According to the study, reducing the dynamic and static friction △F was the key factor to reduce the stick-slip phenomenon and reduce the friction noise.

A novel self-heating 3D printed continuous carbon fiber (CCF)/epoxy (EP) mesh for deicing was proposed. Because of electron migrating conduction and hopping conduction, the conductivity of CCF reached 131.3 S cm−1 at 25 °C and increased by 1.1%–148.4 S cm−1 at 200 °C, exhibiting a negative temperature coefficient (NTC) effect. Because of the electron conduction of CCF and uneven thermal expansion of the fiber/matrix components, the CCF/EP mesh had NTC and positive temperature coefficient (PTC) effects. After specific hot-cold cycles, the resistance stability of the printed mesh was confirmed. Compared to unprotected glass fiber-reinforced composite laminate, the CCF/EP mesh reinforcement decreased the deicing time by 85% and had a protective effect on the residual flexural strength and modulus, fiber-resin bonding, and internal voids. Excellent conductivity, resistance stability, and electric self-heating performance indicate that 3D printed CCF/EP mesh is a promising candidate for use in deicing.

Collagen and chitosan are widely employed as biomaterials, including for 3D-bioprinting. However, the use of collagen and chitosan (col:chi) blends as bioinks is still scarce. In this work, the rheology of different hydrogel precursors (0.5–1.50% w/v chi: 0.18–0.54% w/v col) was analyzed through frequency and strain sweeps, as well as at different shear rates. Col:chi blends showed a shear-thinning behavior, with viscosity values at low shear rates between 0.35 and 2.80 Pa s. Considering the strain rate determined by the applied flow in a 3D-bioprinter, precursor viscosities during the extrusion were in the interval 0.5–0.8 Pa s. Printability (Pr) was measured comparing images of the printed meshes and the corresponding CAD grid design, using photograph analysis. Col:chi 0.36:1.00 was chosen to print mono-layered scaffolds for tissue engineering (TE) because of its suitable viscosity, printability and polymer ratio content. Hydrogels were obtained through NaHCO3 nebulization and 37° incubation, and NHS/EDC were added to obtain scaffolds with improved mechanical behavior. They were stable after 44 h in PBS with collagenase at physiological level and showed no cytotoxic effect in NIH-3T3 fibroblasts.

The present work aims to prepare thermal and oxidation resistant Natural Rubber (NR) composites using antioxidant-modified nanosilica (MNS). The thermo-oxidative aging performance of the composites was evaluated by the variations in mechanical properties after aging at 100 °C for 24 h. The performance was further monitored through Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, Thermogravimetric Analysis, and Dynamic Mechanical Analysis. NR nanocomposite with 1–7.5 phr nanosilica (NS) and 3 phr MNS were prepared and its rheological properties were studied. A comparative study of the theoretical models yielded that modified Guth-Gold equation predicted Young's modulus better than other models. Thermal stability of natural rubber MNS composite was improved by 10 °C with pre-eminent mechanical properties like tensile strength and heat build-up. A linear relationship of compression set with modulus of all composites were also established. Equilibrium swelling test revealed improved crosslink density in NR MNS composite. The strong interaction between antioxidant and nanosilica enabled low migration of antioxidant in NR MNS composite. Hence its protective function after aging showed more effective than NR NS composites. These versatile functional properties of NR MNS composite suggest its potential application in electrical, electronic and high performance rubber products.

One of the main challenges of the mode I double cantilever beam (DCB) test is the simultaneous determination of the applied load and displacement with the developing delamination length. The present work addresses this issue by side-view tracking the crack propagation by means of digital image correlation (DIC). Two different reduction methods were developed to determine the crack length from the DIC data. On the one hand, the crack tip position was defined by the high strain concentration in the immediate vicinity of the crack tip, and on the other hand, by crack tip opening displacement (CTOD). The data obtained enabled the calculation of the energy release rate of carbon fibre reinforced thermoplastic specimens with either run-arrest or stable crack extension. For reasons of comparability, top surface analysis (TSA), as recently reported, was also carried out. Following this approach, the crack propagation was tracked applying DIC to the top specimen surface. The methods developed showed a good correlation with both the standardised procedure and TSA. It was shown that DIC can be used as an alternative to the conventional optical measuring tools to follow the crack propagation in the mode I DCB test.

This study establishes FEM modeling for compressive deformation behavior of polymeric foams with different loading rates. The polymeric foam used in this study was made from polypropylene (the base matrix of the polymer) with porosity of about 95%. The pore size and shape were randomly distributed in the foam. The X-ray CT method was first conducted to observe the microstructure, the geometric feature of which was reproduced in the FEM model. Uniaxial compression tests with different loading speeds were carried out to investigate an effect of loading rate (strain rate) dependency on the deformation behavior. By using the X-ray CT method, in situ observation of microscopic deformation was carried out. Furthermore, FEM computations were carried out to simulate macroscopic and microscopic deformation behaviors. The random porous structure was modeled using Surface Evolver. The elastoplastic property with strain rate dependency was used in this model. The established FEM framework may be useful for a porous polymer with a random pore structure and for deformation modeling with strain rate effect.

Poly (methyl methacrylate) organic glass is used in aircraft windshield application; these structures should have better fatigue and fracture resistance to yield good service life. The tendency towards achieving these properties is lost during manufacturing process. This study aims to determine the effect of grooving on PMMA Organic glass. The grooves are manufactured using two different processes namely Micro-Milling (MM) and Laser Ablation (LA). The tribological properties of laser ablated PMMA (LA-PMMA) and micro-milled PMMA (MM-PMMA) were studied using Pin-on-disc tribometer. The grooved surface roughness of both MM-PMMA and LA-PMMA samples has decreased with increase in wear time, whereas after reaching minimum roughness the coefficient of friction has increased; due to higher adhesion between polymer and sliding metal. The tensile properties of differently machined samples have not shown significant difference; whereas the fracture toughness values were higher with LA-PMMA samples. This effect indicated LA-PMMA had greater capacity to resist crack propagation compare to MM-PMMA samples. Similarly the fatigue endurance limit was found higher with LA-PMMA compared to MM-PMMA, due to better finish of LA-PMMA. Further, the microscopic analysis of laser grooved sample before and after fracture have also shown smoother surface and less conic shapes (fracture point) compare to MM-PMMA.

For energy scavenging applications, estimating fatigue life of dielectric elastomer is as crucial as computing the amount of scavenged energy. Crack growth approach, well known in rubber industry, is a fast methodology to estimate fatigue life. We adapt this methodology to dielectric silicone elastomers (Elastosil 2030) and we focus in particular on the factors influencing this estimation such as sample geometry, tearing energy, power law. We underline that the variation in tearing energy estimation induces a small dispersion on the fatigue life estimation whereas power law identification is the crucial and critical parameter. Finally, we define an index of performance based on fatigue life and scavenged energy density, and we compare two materials (acrylic 3MVHB4910 and silicone Elastosil 2030).

The modification of nanocomposite coatings with fillers having unique characteristics in the polymeric matrix is a promising strategy to enhance the durability as well as to prevent the growth of microorganisms that decrease the stability of the materials. This study was conducted to evaluate the rheological and antimicrobial behavior of epoxy-based nanocomposite coatings filled with nanosilica, titanium oxide (TiO2) and zinc oxide (ZnO) against Staphylococcus aureus and Escherichia coli. A rheometer was used for characterizing the rheological properties of the various fillers embedded epoxy nanocomposite coatings. All of the composites inhibited the growth of Staphylococcus aureus and Escherichia coli on modified Kirby Bauer antimicrobial testing, only when they are in contact with samples. Upon quantitative analysis, bioactive constituent dependent antimicrobial activity was observed which increased with the exposure of contact times. The epoxy/silica/TiO2/ZnO (ESTZ) coating showed the highest bacterial reduction of more than 95% for 4 h of treatment. The bioactivity was decreased for the case of epoxy/silica/ZnO (ESZ) or epoxy/silica/TiO2 (EST). The combined effect of the nanosilica, TiO2, and ZnO shows the highest performance in terms of stress, viscosity and torque compared to the individual effect of these three fillers onto the epoxy. Results showed that the shear stress of ESZ, EST, epoxy/silica (ES), and ESTZ coating was increased by 4.4%, 7.7%, 32.2%, and 42%, respectively, compared to the neat epoxy (NE) coating. The torque versus strain curve also showed that the torque of ESTZ composites was the highest (0.52 mN m) compare to NE (0.36 mN m), ESZ (0.38 mN m), EST (0.40 mN m), and ES (0.45 mN m). The studies indicate that the epoxy-based thermoset nanocomposite coatings can be utilized as bactericidal surfaces for the industrial and medical purpose to reduce microbial growth.

Three different solvent mixtures were used to prepare electrospun membranes based on polylactic acid (PLA), polyethylene oxide (PEO) and enzymatic cellulose nanofibers (CNF). The materials were characterized from a morphological, spectroscopic, mechanical and rheological point of view. Furthermore, swelling test were performed in order to assess the water uptake of each sample. The results put into evidence that the choice of the solvents affects the structure and the properties of the membranes. Among the protocols tested, using chloroform/acetone/ethanol mixture was found to allow a high degree of CNF dispersion and a good electrospinnability of polymer solutions. These features led to membranes with impressive improvement of mechanical properties (+350% in stiffness, +350% in tensile strength and +500% in toughness) with respect to those of PLA/PEO and dramatically increased the water uptake of these materials (up to +350% within 120 min).

Aramid fiber (AF) reinforced by polyamide (PA) composites are excepted to have good interfacial matching due to their similar chemical interactions of hydrogen bonding. Thus, polarizing optical microscope (POM), transverse fiber bundle (TFB) test, and droplet micro-debonding technique were respectively performed to characterize interfacial crystallization, adhesion and shear behaviors of AF/PA6 composites with different thermal treatments. Both interface adhesion and AF fibrillation are enhanced with decreasing cooling rate or increasing annealing temperature due to the increased interfacial transcrystallization interaction. However, fast cooled interface also presents a high interfacial shear strength (IFSS) due to favorable normal residual stress. The apparent IFSS is believed to be a result of competition between crystallization enhancing interfacial interaction, interfacial mismatching aggravating debonding, and an uncertain residual stress positive or negative for load transfer. TFB failure mechanism including AF fibrillation and kinking are schematically presented. Fibrillation strength of AF is found to follow Weibull distribution evaluated by droplet micro-debonding technique.

In this paper an inclined edge cracked short beam specimen subjected to symmetric three-point bend loading was designed and examined for conducting mixed-mode I/II fracture toughness experiments. The aspect ratio (i.e. length to width ratio) and the loading span distance are considered much lower than the other conventional cracked bend beam samples. Crack tip parameters such as stress intensity factors and T-stress were computed numerically for this specimen by several finite element analyses and it was demonstrated that the specimen is able to produce full combinations of mode I and II including pure mode II. The practical capability of the short bend beam specimen was studied experimentally by conducting a set of mixed-mode fracture tests on PolymethylMethacrylate (PMMA) as a well-known model brittle material. The critical stress intensity factors, the direction of fracture kinking and the path of fracture trajectory were investigated both experimentally and theoretically using two stress and strain-based fracture criteria. The fracture toughness of tested PMMA was decreased by moving towards mode II case due to the effect of T-stress on the fracture mechanism of the short bend beam specimen.

The high cost (material, service, and production loss) involved to substitute a condemned flexible pipe whose pressure sheath has reached its theoretical preconized service life has motivated this study. Therefore, the main objective is to propose a constitutive equation for in-service aged polyamide 11 (PA11) describing the creep behavior as a function of temperature, stress level, and Corrected Inherent Viscosity (CIV), this latter parameter representing the level of material degradation due to hydrolysis. The constitutive equation may be employed for gap spanning analysis and also to subsidize the decision to extend the operational life of flexible pipes that have experienced more severe conditions or have been used for a longer time than designed. The current models to assess the remaining life of the sheath are based only on a single property decay based on corrected intrinsic viscosity (CIV) curves obtained from laboratory tests. To compare the result from the life-prediction model in use and the material mechanical behavior, an experimental campaign was performed using polyamide 11 (PA 11) samples retrieved from a 6″ gas production flexible flowline, which theoretically had reached a full-damaged condition after nearly 3 years operating at higher than specified temperature (80 °C). Dog-bone geometry specimens were machined from the internal, intermediate, and external layers of the flexible flowline pressure sheath. Once polymers are excellent thermal insulators, it was assumed that the material operated under different temperatures within the thickness and, therefore, presents different degradation degrees. CIV, tensile, and creep analyses were performed, confirming that the behavior is different for each region within the thickness of the pressure sheath. Differential scanning calorimetry (DSC), thermogravimetry analyses (TGA), and dynamic thermomechanical analysis (DMA) were performed to comparatively characterize the degree of crystallinity, amount of extractables and morphology of each section. A creep behavior model considering the gradient difference in the material is proposed. It is concluded that aging is different across the liner thickness, and the PA11 creep behavior may be expressed as a function of the CIV, temperature, and stress.

Polymeric electrospun nanofibers have been gaining notoriety in the same way as their industrial applications, since the manufacturing of this type of material is simple and low-costed. In order to obtain fibrous polymeric material with small diameters and with reduced beads formation, a 24 factorial experiment with triplicate at center point was performed. Cellulose acetate (CA) and cationic cetylpyridinium bromide (CPB) surfactant nanofibers were made using a homemade electrospinning apparatus. The assessed inputs were as follows: CA%, CPB%, flow rate, and applied voltage. From the analysis of the response surface methodology and scanning electron microscope (SEM), the optimal concentrations of CA and CPB for producing nanofibers were 21 w/v-% and 0.5 w/v-%, respectively, using a flow rate of 0.7 mL h−1 and applied voltage of 18 kV. Fibers mats morphology shows average diameter of 0.2 μm and 7 nm pore size, as well as it was found that the single fiber unit presented nanoheterogeneity. Mechanical resistance of 2.70 MPa was obtained in the tensile strength test. The modification of CA by the addition of surfactant attributed better thermal and mechanical resistances to the nanofibers without, however, affecting their biodegradability and water resistance properties. The morphological characteristics of the newly obtained CA/CPB nanofibers combined with mechanical resistance provided subsidies to suggest that the as-obtained material presents potential to be applied as an air filter.

PHB-silver nanocomposite (PHB-AgNc) was synthesized biologically by utilizing a dairy-industry by-product, cheese whey permeate as a substrate for Bacillus megaterium. The single-step synthesis of PHB-AgNc was further confirmed by UV–vis spectroscopy and GC-MS analysis. Further, the extracted PHB-Ag Nc was characterized by employing various techniques such as TEM, SEM, FTIR, NMR, Zeta Potential, and DLS analysis. Mechanical properties such as elongation at break, tensile strength, and Young's Modulus were found to be 1.305%, 35.42, and 1.058 N/mm2, respectively. The nanocomposite was found to be stable, polydispersive, and hydrophobic. It exhibited a degradation temperature of 340 °C and portrayed significant antimicrobial resistance against common food pathogens such as E.coli and Pseudomonas spp. Batch fermentation study was carried out for a period of 96 h in a 14 L bioreactor. The highest biomass and nanocomposite yield obtained was 5.8 and 2.4 g/L, respectively. The highest product productivity concerning biomass was found to be 0.012 h−1 at 12 h. The film's migration properties were tested for various food stimulants, and the values obtained were less than the overall migration limit established for food contact materials; hence, the film was found to be appropriate for food packaging applications.

Stretchable conductive hydrogels have received significant attention due to their possibility of being utilized in wearable electronics and healthcare devices. In this work, a semi-interpenetrating polymer network (SIPN) strategy was employed to fabricate a set of flexible, stretchable and conductive composite hydrogels composed of polyvinyl alcohol (PVA) in the presence of glutaraldehyde as the crosslinker, HCl as the catalyst and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as the conductive medium. The results from FTIR, Raman, SEM and TGA indicate that a chemical crosslinking network and interactions of PVA and PEDOT:PSS exist in the SIPN hydrogels. The swelling ratio of hydrogels decreased with increasing content of PEDOT:PSS. Due to the chemical crosslinking network and interactions of PVA and PEDOT:PSS, PVA networks semi-interpenetrated with PEDOT:PSS exhibited excellent tensile and compression properties. The tensile strength and elongation at breakage of the composite hydrogels with 0.14 wt% PEDOT:PSS were 70 KPa and 239%, respectively. The compression stress of the composite hydrogels with 0.14 wt% PEDOT:PSS at a strain of 50% was about 216 KPa. The electrical conductivity of the hydrogels increased with increasing PEDOT:PSS content. The flexible, stretchable and conductive properties endow the composite hydrogel sensor with a superior gauge factor of up to 4.4 (strain: 100%). Coupling the strain sensing capability to the flexibility, good mechanical properties and high electrical conductivity, we consider that the designed PVA/PEDOT:PSS composite hydrogels have promising applications in wearable devices, such as flexible electronic skin and sensitive strain sensors.

This work consists of the synthesis of high purity graphene nanoflakes (GNF), the manufacturing of GNF-epoxy nanocomposites and the mechanical characterization of the nanocomposite at high and quasi static strain rates, (2750/s - 1.E−5/s). GNF were synthesized by using the electric arc discharge technique. Thermogravimetry/Differential Thermal Analysis (TG/DTA) of synthesized graphene reveals high purity and high crystallinity. Raman spectra and the broad Brunauer-Emmet-Teller (BET) specific surface area indicate that the synthesized graphene has several layers. Following the solution mixing manufacturing process of GNF-epoxy nanocomposites, the influences of strain rate on the mechanical behaviors are investigated under quasi static and dynamic loadings. High strain rate uniaxial compression tests (1270–2750/s) using Split Hopkinson Pressure Bar (SHPB) and quasi static compression tests (1.E−3 and 1.E−5/s) of GNF-epoxy with two graphene contents (0.1 and 0.5 wt %) are performed at room temperature. The maximum elasticity modulus achieved by the GNF-epoxy with 0.5 wt% at the strain rate of 2350/s corresponds to a 68% increase compared to the neat epoxy. The yield strength of the material is doubled under dynamic loading conditions compared to the quasi static loading.

In this paper, experimental investigation and numerical modelling of the mechanical properties of polyvinylidene fluoride (PVDF) nanofibrous membranes produced by electrospinning are addressed. Membranes with three different diameters are fabricated by adjusting the needle-collector distance during electrospinning. The fiber morphology and the physical properties of the resulting membranes are investigated using Scanning Electron Microscopy (SEM) while their elastic properties are probed using conventional tensile tests. It is found that the membrane with the largest nanofiber diameters are filled with large beads while the contrary is found in the membrane with the smallest nanofiber diameter. Consequently, the membrane with the smallest nanofiber diameter yielded the highest membrane Young's modulus thanks to better fiber packing and higher crystallinity in the nanofibers. Next, the experimental results serve as basis for a pixel-based finite element method (FEM) which is applied directly on the SEM images of the membranes. This technique has the advantage of providing estimations of mechanical properties from the real structure of the membranes. Two parameters are needed for this linear elastic analysis: the elastic modulus of a single fiber and the fiber percentage in the membrane. Results show that the model predictions are in good agreement with experimental data. These results suggest that the pixel-based FEM could be a promising nondestructive alternative to the conventional tensile tests.

The drawback of the application for poly(l-lactide) (PLLA) is the low crystalline rate and crystallinity obtaining via normal processing methods. Modifying crystallization of PLLA has been found to be an efficient way to improve its mechanical and heat resistance properties. In this wok, 4, 4′-diphenylmethane diisocyanate (M) and benzohydrazine (P) were employed into PLLA melt to in-situ form nucleating agents. The in-situ melting reaction was confirmed by a nuclear magnetic resonance spectroscopy. The crystallization behavior and crystalline morphology were investigated by a differential scanning calorimetry, a polarized optical microscopy and a field emission scanning electron microscope. The crystalline rate of PLLA was abruptly enhanced by adding (M+P) and melting reaction with PLLA. The crystallization half-time of PLLA dramatically decreased from 42.0 to 1.1 min at 130 °C by the in-situ formation of nucleating agents. The crystallinity of PLLA increased from 10.3 to 42.1 by adding 0.25% (M+P) and melting reaction for 8 min. Furthermore, the size of PLLA crystals was dramatically reduced because of the nucleating effect. Accompanied with improvement on crystallinity, the Vicat softening temperature of PLLA shifted from 57.4 °C to 93.7 °C by the in-situ reaction with 6.00% (M+P), and indicating heat resistance enhancement.