Two phosphorus-nitrogen flame retardants were synthesized by using chlodiphenylphosphine (CDP) or diphenylphosphinyl chloride (DPP) and cytosine (Cy), respectively. The products are marked as CCDP and CDPP, and characterized by using Fourier transform infrared spectra (FT-IR), 31P and 1H nuclear magnetic resonance and thermogravimetric analysis (TGA). The CCDP and CDPP were used to modify the flame retardancy of polyamide 6 (PA6). The results indicated that 6 wt% CCDP and CDPP both make PA6 achieve the UL-94 V-0 rating and improve its LOI value. The degradation behavior was studied by TG-IR, melt volume-flow rate, etc. The results revealed that both CCDP and CDPP promote the degradation of PA6 and improve its flame retardancy by melting away. The CCDP tends to work in the gas phase and the CDPP in the condensed phase. In addition, in order to reduce the effect of flame retardant on the mechanical properties of PA6, CDPP was coated with epoxy resin. The results showed that the flame retardancy decrease after coating. Finally, melamine cyanurate was blended with the CDPP coated by epoxy to adjust the comprehensive properties of PA6 composite, and excellent flame retardancy and mechanical properties are obtained.

Inorganic matter modifications were used to improve the hydrophobic properties and slow-release effects of water-based copolymer films. Water-based copolymers were prepared by aqueous polymerization of polyvinyl alcohol, starch, chitosan, and sodium carboxymethyl cellulose, and then, zeolite powder, volcanic ash or biochar were added to prepare the inorganic matter modified water-based copolymer films. The results showed that the inorganic matter modified water-based copolymer films had enhanced thermal stability, reductions in O-H and water vapour permeability, and increased crystallinity and roughness. Compared with water-based copolymer films, the water absorption capacities of the zeolite powder modified water-based copolymer films, volcanic ash modified water-based copolymer films, and biochar modified water-based copolymer films were reduced by 42.8%, 50.0% and 39.0%, and their ammonium permeability was reduced by 53.0%, 12.1% and 1.1%, respectively. Inorganic matter modified water-based copolymer films have properties that make them suitable for use in preparing slow-release coating materials.

Rapid advances have been made in developing analytical technologies for characterization of highly heterogeneous active ingredients of complex drugs, such as pentosan polysulfate (PPS), active ingredient of the drug Elmiron®, approved by the Food and Drug Administration and marketed in the United States to treat interstitial cystitis. PPS sulfated polysaccharides comprise of a repeat unit of β(1—4)‐D‐xylopyranoses randomly substituted by 4‐O-methyl-glucopyranosyluronic acid. To define the critical quality attributes (CQAs) of such a complex drug, it is critical to develop an approach that integrates data from orthogonal analytical methodologies. Here, we developed an approach integrating diverse analytical tools including gel permeation chromatography, LC/ESI-MS and NMR to measure CQAs of PPS. The proposed mathematical framework integrates the data from these diverse analytical methods as function of PPS chain length and building blocks. Our approach would facilitate in establishing a scientific foundation for comparative characterization of drug products with complex active ingredients.

One of the main challenges in membrane gas separation is the plasticizing effect that reduces selectivity. For a better understanding of this phenomenon, the knowledge of the sorption behavior of each component of the mixture is necessary. For this purpose, the sorption thermosyphon apparatus (STA), was successfully designed and tested with gas sorption measurements. One of the main advantages of the STA compared to actual other methods is to ensure concentration uniformity at the headspace using a thermosiphon, as pressure decay is recorded. The equilibrium condition is not disturbed during the sampling and allow the obtention of accurate data at the end of the sorption experiment. To validate the novel system, the sorption, diffusion and permeation coefficients of pure CO2 and CH4, as well as for a CO2/CH4 (50/50) mixture, in polydimethylsiloxane (PDMS) were obtained through STA and other experimental techniques showing good agreement with literature data.

It is proposed to transfer the capabilities of a high sensitivity photothermal technique, developed by the group and widely used in the study of thermal properties of ceramics, metals and glass, to the study of polymer composites. The technique uses a sensing beam for the measurement of the thermal response of the sample due to local effects induced by heating with a modulated pump laser. With a simple spatial sweep of the beams on the sample surface, information on a micrometric scale of the thermal diffusivity of the material, distribution of phases and pores is obtained. Post-process analysis allows calculating average values of relevant properties such as thermal diffusivity, degree of crystallinity and distribution of aggregates. These measurements are performed at low laser powers (of the order of micro watts) avoiding the damage of the studied samples and turning this technique into a powerful tool of non-destructive characterization.

The purpose of this study was to prepare a novel Clay Bio-Polymer Nanocomposite (CBPN) films by mixing polymer (chitosan, C) with exfoliated nanoclay (kaolinite, k). DRX has shown that the mechano-chemical treatment of kaolinite allows its exfoliation and the significant reduction of its particles size. Physicochemical properties namely thickness, water solubility, color, light transmission and transparency of the films were studied. Fourier transform infrared analysis (FTIR) was to study the interaction between chitosan and kaolinite. Differential scanning calorimetry (DSC) scans showed that the transition temperature (Tg) of films depends on the film's composition. The surface morphology of the films was also studied by scanning electron microscopy (SEM). Results showed that water solubility (Ws) decrease with the increase of the amount of clay. In addition, the presence of clay in the said films increases the mechanical strength. All prepared films were tested for their antimicrobial activities against gram-positive and gram-negative bacteria (strain). It was found that all CBPN films showed good inhibitory activity against all the tested bacteria. The above analysis suggested that the CBPN films could be used as potential candidates for therapeutic application.

Extracellular polysaccharides (EPS) from Nostoc muscorum, a heterocystous, filamentous cyanobacterium isolated from a jhumland (shifting cultivation) soil of Assam, North-East India, was physico-chemically characterized to find out its potential applications and to improve its production with some stress source like ozone. Using Response Surface Methodology (RSM), EPS production was improved. Accordingly, with magnesium sulfate (MgSO4·7H2O) at 62 mg L−1, Sodium Chloride (NaCl) at 58 mg L−1 and 56 mg L−1 di-potassium hydrogen phosphate (K2HPO4), a yield of 126.73 μg mL−1 of EPS in 12 days was obtained which was four-fold higher than un-optimised control. An important finding of this study is that EPS production could be further enhanced by over 50% with a mild stress by a strong oxidizing agent ozone (O3). Physico-chemical properties of this Ozone induced EPS was evaluated and found identical to uninduced EPS. EPS was composed of the hexoses- Glucose (14.80%), Galactose (18.01%) and Mannose (12.64%), the pentoses- Arabinose (17.86%) and Xylose (11.66%), the deoxyhexose- Fucose (12.53%) and Rhamnose (12.50%). Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analysis revealed the presence of the functional groups uronic acid and traces of sulfate group. The Zeta potential analysis revealed that the emulsions were stabilized electrosterically rather than by pure electrostatic repulsion and steric stabilization. EPS at 1% in hydrocarbons and vegetable oils was observed to be an excellent emulsifier (99%), with reasonable stability. Rheological study revealed that the EPS (1%) was a non- Newtonian weak gel, useful for emulsification activity. Unlike petroleum-based emulsifiers now in use, bio-based EPS are renewable, economical and eco-friendly. The physico-chemical characteristics suggest their utility in a wide variety of other applications including bioremediation, manufacture of paints, shear reduction in oil drilling etc.

Thermoplastic starch (TPS) composites incorporating bentonite/cellulose (Bent/Cellulose) hybrid fillers in different ratios were prepared by film casting. Ultra‐sonication was done to promote good dispersion of filler in the host TPS and enhance the filler‐matrix interactions. Ultra‐sonicated fillers resulted in superior improvement in the tensile properties when the samples preconditioned at both ambient and 2°C. Upon preconditioning at 2°C, the TPS composite containing the ultra‐sonicated hybrid bent/cellulose in 80:20 ratio displayed the greatest tensile properties achievement among all the tested materials. These could be due to the effect of low temperature interactions between the starch, plasticizers, and the hybrid fillers. Differential scanning calorimetry analysis proved the changes in the crystallinity and dynamic characteristic of the TPS molecular chains which benefit in enhancing the biopolymer elongation at break and toughness, even when stored at refrigerated condition. In summary, the TPS/bent/cellulose composite has potential to be further developed for refrigerated food packaging application. POLYM. ENG. SCI., 2020. © 2020 Society of Plastics Engineers

Graphene/polymer nanocomposites (GPNCs) have gained intense research interest in recent years. Graphene can improve the properties of the nanocomposites at low loadings, but usually causes sudden drops in the mechanical properties of the nanocomposites at similarly low loadings, risking the performance, reproducibility, and batch stability of the nanocomposites. This problem has been troubling the GPNCs field for years, but it is difficult to solve mainly because the mechanism of the sudden mechanical property drops has not been well documented yet. Here, we present a systematic study on this problem. At first, a statistical study was made to provide an overview of the sudden mechanical property drops. It was found that the sudden mechanical property drops were almost independent of the surface modification of graphene, and the in situ polymerization method sometimes leads to lower critical concentration than the solvent blending and melt blending methods. Then, we demonstrated a cutting‐off mechanism which unveiled that the formation of a continuous or semicontinuous network of graphene throughout the polymeric matrix was the main cause of the sudden mechanical property drops, and the low critical concentration of the sudden mechanical property drops was mainly due to the large aspect ratio of graphene. Finally, future research prospects were proposed. Overall, our work has provided new understandings and insights to the mechanical properties of GPNCs.

Polyurethanes are commonly used as shape memory materials due to their micro‐phase separation structure. The degree of micro‐phase separation is the key factor in the shape memory properties of materials. In this study, the shape memory polyurethane (SMPU) elastomer was prepared based on polycaprolactone diols, isophorone diisocyanate, and 1, 4‐butanediol. And the branched structure is introduced by glycerol and hexamethylene diisocyanate to increase the degree of micro‐phase separation. Moreover, nano‐ZnO is also used to enhance micro‐phase separation. Atomic force microscopy images clearly show that the nano‐ZnO disperses uniformly in the polymer matrix and leads to significant change in the phase structure of SMPU. Dynamic mechanical analysis results indicate that the SMPU/ZnO nanocomposites possess two phase transition above 0°C, one is the melting transition of the soft segments, which is near the body temperature, and the other is the glass transition of hard segments. And with the addition of nano‐ZnO, the difference in transition temperature between the hard and the soft segments is significantly increased. The relationship between shape memory properties and the micro‐phase separation is explored and discussed. In vitro biocompatibility studies show that the SMPU/ZnO nanocomposites have good biosafety. Therefore, the obtained bionanocomposites have the potential application prospect as smart biomaterials.

The capacities of Z‐pinning in improving the bending performance of composite T‐joints were examined experimentally and numerically. It was found that Z‐pinning was not effective in enhancing the maximum bending load capacities of the T‐joints. Delamination at the interfaces of flange/filler, flange/flange, flange/skin, in the arc‐flange, as well as the fracture of the upper corner of the filler was observed. Among those failure patterns, the notorious delamination formed in the arc‐flange assumed the main responsibility of the disability of Z‐pinning in enhancing the maximum bending load capacity. Despite this, Z‐pinning was found to be highly effective in improving the residual plateau load‐carrying capacities of the T‐joints and the maximum bending displacement could also be dramatically increased, making the T‐joint maintain considerable bending load capacity under large deformation and preventing the T‐joint from catastrophe failure once the maximum bending load was attained.

The influence of seawater (SW) and distilled water (DW) aging on low‐velocity impact behavior of glass fiber/polymer laminates with and without multiwalled carbon nanotubes (MWCNTs) is experimentally investigated. To this aim, unidirectional glass fiber fabrics were coated with 0.75 wt% MWCNTs by airbrushing, infused with resin (epoxy or vinylester), and cured. Then, composite laminates with and without MWCNTs were cut into specimens for low‐velocity impact testing and exposed to hydrothermal aging by immersing them to SW and DW at 60°C for ~2000 h. After that time of conditioning, dry and wet specimens were tested using a drop‐weight tower with an impact energy of 15 J. Results showed that the moisture absorption content of composite laminates exposed to SW and DW aging is considerably higher on epoxy‐based specimens with respect to vinylester ones. The impact tests revealed that the measured impact peak force and absorbed energy in wet specimens are significantly lower compared to dry specimens due to plasticizing effect of the matrix. With the incorporation of MWCNTs into the laminates, the absorbed energy is increased due to additional damage mechanisms induced at CNT‐rich regions during the impact loading. It was also found that the damage area of the laminates after impact tends to be more prominent for laminates fabricated using vinylester resin than for those using epoxy resin as a result of its brittle behavior during impact loading. Post impact damage analyses by ultrasonic C‐scan imaging and scanning electron microscopy showed that matrix cracking, fiber breakage, fiber/matrix debonding, and delamination are the main damage mechanisms induced in the dry and wet specimens during impact.

Abstract Aqueous solutions or gels of polyampholytes attract interest for more than half a century due to their several attractive properties. We present here thermally healable hydrophobically modified physical polyampholyte (PA) hydrogels based on oppositely charged 2-acrylamido-2-methylpropane-1-sulfonic acid sodium salt (AMPS) and (3-acrylamidopropyl) trimethylammonium chloride (APTAC) monomers. PA hydrogels were prepared via micellar polymerization technique in the presence of the hydrophobic monomer n-octadecyl acrylate (C18A) in aqueous sodium dodecyl sulfate (SDS) solutions. Charge-balanced PA hydrogels containing 60–90% water exhibit a high tensile strength and stretchability of up to 202 kPa and 1239%, respectively. Above 7 mol% C18A, swollen hydrogels containing around 90% water exhibit much better mechanical properties as compared with the corresponding as-prepared ones because of the stronger hydrophobic interactions in the absence of SDS micelles. Cut-and-heal tests conducted at 50 °C reveal a complete healing efficiency with respect to Young’s modulus for all as-prepared PA hydrogels within 1–4 h. Graphical abstract .

Abstract We here report the facile fabrication of inverse core–shell and Janus structured particles consisting of poly(4-butyltriphenylamine) (PBTPA) and poly(methyl methacrylate) (PMMA) via a solvent evaporation from solution droplets of a polymer blend dispersed in an aqueous phase. Janus structured composite particles in which the PBTPA domain was partially coated by the PMMA domain were obtained using poly(vinyl alcohol) (PVA) as a suspension stabilizer. On the other hand, when sodium dodecyl sulfate (SDS) was added as a surfactant together with PVA, “inverse core–shell” particles in which the PMMA core was covered by the PBTPA shell were formed as well as Janus particles. TEM observation showed that the PMMA core was located at the center of the sphere and PBTPA layer has uniform thickness in inverse core–shell particles. The increase of the composition of PBTPA or the concentration of SDS increased the ratio of the inverse core–shell particles to the Janus ones. Graphical abstract

Lytic polysaccharide monooxygenases (LPMOs) are powerful enzymes that degrade recalcitrant polysaccharides, such as cellulose. However, the identification of LPMO-generated C1- and/or C4-oxidised oligosaccharides is far from straightforward. In particular, their fragmentation patterns have not been well established when using mass spectrometry. Hence, we studied the fragmentation behaviours of non-, C1- and C4-oxidised cello-oligosaccharides, including their sodium borodeuteride-reduced forms, by using hydrophilic interaction chromatography and negative ion mode collision induced dissociation - mass spectrometry. Non-oxidised cello-oligosaccharides showed predominantly C- and A-type cleavages. In comparison, C4-oxidised ones underwent B-/Y- and X-cleavage close to the oxidised non-reducing end, while closer to the reducing end C-/Z- and A-fragmentation predominated. C1-oxidised cello-oligosaccharides showed extensively A-cleavage. Reduced oligosaccharides showed predominant glycosidic bond cleavage, both B-/Y- and C-/Z-, close to the non-reducing end. Our findings provide signature mass spectrometric fragmentation patterns to unambiguously elucidate the catalytic behaviour and classification of LPMOs.

The preparation mainly composed of extraction, pre-purification and dehydration is essential for the research and development of natural polysaccharides. The methods or conditions used in the three procedures had significant effects on the composition, structure and function of the polysaccharides obtained. Temperature, pH, enzyme, ultrasound and microwave were the important factors associated with their physicochemical changes. Molecular degradation and intermolecular interaction were two of the main mechanisms responsible for the changes. The degradations of polysaccharides responding to hydrothermal and ultrasonic conditions could be partly descripted by multiple linear regression model, implying the possibility for the prediction and control of polysaccharide degradation. Moreover, the interactions between polysaccharide and other compounds, forming complexes natively or conditionally, could be selectively triggered or eliminated to obtain polysaccharides under certain functions. This work shows new insights into the preparation of polysaccharides, which could benefit the efficient utilization of their natural and modified properties.

Cellulose nanocrystals (CNCs) are used to design nanocomposites because of their high aspect ratio and their outstanding mechanical and barrier properties. However, the low compatibility of hydrophilic CNCs with hydrophobic polymers remains a barrier to their use in the nanocomposite field. To improve this compatibility, poly(glycidyl methacrylate) (PGMA) was grafted from CNCs containing α-bromoisobutyryl moieties via surface-initiated atom transfer radical polymerization. The novelty of this research is the use of a reactive epoxy-containing monomer that can serve as a new platform for further modifications or crosslinking. Polymer-grafted CNC-PGMA-Br prepared at different polymerization times were characterized by XRD, DLS, FTIR, XPS and elemental analysis. Approximately 40% of the polymer at the surface of the CNCs was quantified after only 1 h of polymerization. Finally, nanocomposites prepared with 10 wt% CNC-PGMA-Br as nanofillers in a poly(lactic acid) (PLA) matrix exhibited an improvement in their compatibilization based on SEM observation.

The antimicrobial action of chitosan against several phytopathogens in agriculture has been tested, including Penicillium digitatum, which is the major pathogen that causes postharvest decay of oranges. However, the biopolymer action has not been tested against other fungi that are capable of developing molds in orange fruit. This study have demonstrated that chitosan is able to inhibit the growth in vitro and in vivo of two Penicillium species, which were isolated from decay oranges fruit and identified as Penicillium citrinum and Penicillium mallochii, using molecular methods. This is the first report of P. mallochii acting as an orange phytopathogen. The commercial chitosan with higher molecular weight demonstrated a reduction in the disease incidence of 50-70% for the inoculum P. citrinum and of 40% for the inoculum P. mallochii for the in vivo experiments. The data obtained opens interesting alternative options to synthetic fungicide to prevent orange decay caused by the potential phytopathogenic species of Penicillium here identified.

In presented study, various chitosan derivatives containing covalently bounded gallic acid were obtained: chitosan with gallic acid (CG), quaternized chitosan with gallic acid (QCG), and succinylated chitosan with gallic acid (SCG). Chitosan derivatives were used as stabilizing and reducing agents in the synthesis of silver nanoparticles (AgNPs). The dimensional characteristics of nanomaterials were determined by transmission electron (TEM), dynamic light scattering (DLS) and atomic force (AFM) microscopy, antibacterial activity (against E. coli, S. epidermidis), cytotoxicity (HaCaT, Colo 357 cell lines) and hemocompatibility. Among all samples, QCG-AgNPs showed low toxicity in the range of studied concentrations (3.125-100 µg/ml) high stability of nanoparticle for 4 months (according to UV.spectroscopy data) the highest antibacterial activity against S. epidermidis (3.91 µg/ml). The high antibacterial activity, stability, and simplicity of the process of producing AgNPs based on the QCG derivative reveals that a new method for producing modified AgNPs deserves future consideration.

In this study, 2-urea-chitosan oligosaccharide derivatives (2-urea-COS derivatives) and 2,6-diurea-chitosan oligosaccharide derivatives (2,6-diurea-COS derivatives) were successfully designed and synthesized via intermediate 2-methoxyformylated chitosan oligosaccharide. All samples were characterized and compared based on FT-IR, 1H NMR spectroscopy, and elemental analysis. The antifungal effects of COS derivatives were tested against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, and Botrytis cinereal. Their antioxidant properties, including superoxide radicals’ scavenging activity, hydroxyl radicals’ scavenging activity, and DPPH radicals’ scavenging activity were also explored within different concentrations. COS derivatives bearing urea groups showed improved bioactivity compared with pristine COS and 2,6-diurea-COS derivatives had a higher biological activity than 2-urea-COS derivatives in tested concentrations. Additionally, L929 cells were used to carry out cytotoxicity test of COS and COS derivatives by CCK-8 assay. The results indicated that some of samples showed low cytotoxicity. These findings offered a suggestion that COS derivatives bearing urea groups are promising biological materials.

A therapeutic nanocarrier capable of cell targeting has the potential to reduce off-target effects of otherwise effective drugs. Nanoparticle surface modification can be tailored for specific cells, however multistep surface modification can prove slow and difficult for a variety of cell types. Here, we designed drug carrying polysaccharide based nanoparticles with a layered structure for clickable surface modification. The center of nanoparticle was composed of cationic macromer (e.g., poly-L-lysine) and anionic polysaccharide (e.g., heparin). Furthermore, a ‘clickable’ polysaccharide was installed on the surface of the nanoparticles to permit a wide range of bioconjugation via norbornene-tetrazine click chemistry. The utilities of these layered nanoparticles were demonstrated via enhanced protein sequestration, selective cell targeting (via PEGylation or altering polysaccharide coating), as well as loading and release of chemotherapeutic. The drug-loaded nanocarriers proved cytotoxic to J774A.1 monocytes and MOLM-14 leukemia cells.

The novel flame retarded unsaturated polyester resins have been developed and prepared by introduction of high nitrogen content additives into the polymer matrix in order to verify their effectiveness in the formation of swollen carbonaceous char inhibiting the burning process of the polymer. The intumescent flame retardants (IFRs) based on mixture or metal complex were developed and characterized by particle size distribution, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD), elemental analysis (CHN) and thermogravimetric analysis (TGA). The evaluation of the efficiency of IFRs addition on the flammability and smoke emission of the unsaturated polyester resins (UP) was carried out using the fire hazard (UL-94), limiting oxygen index (LOI) and cone calorimeter (CC) tests, as well as smoke density chamber tests. The volatile compounds evolved during the burning of materials were determined using a steady state tube furnace and a gas chromatograph with mass spectrometer. Furthermore, the prepared materials were subjected to differential scanning calorimetry (DSC), thermogravimetric c analysis and water resistance tests. The mechanical properties of the materials were investigated using Shore D hardness and dynamic mechanical thermal analysis (DMA). The structural evaluation of the manufactured materials and samples after the cone calorimetry test was carried out using scanning electron microscopy (SEM). It was found that the incorporation of new intumescent flame retardants led to the formation of carbonaceous char layers’ inhibiting the decomposition process and limiting the smoke emission. The most promising results were obtained for the resin containing complex designated as ZN3AT, for which the highest reduction in maximum values of heat release rate (419 kW/m2) compared to unmodified polymer (792 kW/m2) were recorded. Apart from that, the prepared intumescent flame retardants affect the cross-linking process as well as the thermal and mechanical properties of the UP.

This study proposes an optical methodology to measure the deflection radius of flexible polymeric substrates; to our best knowledge, this is the first report taking into consideration the optical anisotropy effect of these substrates for such measurements. The relation between the deflection-induced optical phase retardation of two distinct refraction beams and the deflection radius was derived. Full-field phase maps were obtained via a polarization measurement system and the phase-stepping technique. The measurement results for three substrates having nominal deflection radii of 50, 55, and 60 mm were, correspondingly, 51.39 ± 0.37, 57.56 ± 1.00, and 58.71 ± 0.85 mm (error = 2.78%, 4.65%, and 2.15%, respectively); thus, the measurement precision was confirmed.

EPDM rubber gaskets, as a water-proof sealing material installed in the tunnel segment joints, were subjected to compressive stress-thermo oxidative ageing at different temperature and compressive stress levels. It was found that compared with thermo-oxidative ageing, compressive stress-thermo oxidative ageing of EPDM samples was more aggressive due to the destructive effect of compressive stress: the molecular structure was oxidized to form oxygenated species such as carbonyl groups, while high compressive stress level resulted in the degradation of EPDM with lower degradation activation energy (Ea), and the breakage of CB network structure and phase separation. Meanwhile, the crosslinking reaction dominated over the chain scission reaction especially at high temperature during the whole ageing process, leading to the increase of crosslinking density of EPDM samples. With increasing ageing temperature and compressive stress, the ageing degree of EPDM rubber was much severe, and compressive stress promoted the degradation of samples, resulting in the decrease of glass transition temperature (Tg) and increase of free volume at high stress levels, while thermo-oxidative ageing promoted the crosslinking reaction of samples, leading to the higher Tg and lower free volume at high ageing temperature. As a result, the surface of EPDM rubber became much rough and interfacial debonding occurred between CB and EPDM matrix, while the mechanical and durable sealing resilience performance were deteriorated during stress-thermal ageing.

It is of great significance and challenge to efficiently improve the tracking and erosion resistance of silicone rubber along with the growing requirements in the field of outdoor high voltage insulation. In this work, we herein proposed an effective way to address this issue by incorporating vinyltriethoxysilane (ViTES) and layered Mg–Al double hydroxide (LDH) into high temperature vulcanized silicone rubber (HTVSR). ViTES/LDH notably enhanced the tracking and erosion resistance of HTVSR. With addition of 3.33 phr ViTES and 5.00 phr LDH, the anti-tracking performance of HTVSR reached the 1A 4.5 level, and the eroded mass was merely 0.3%. The results of scanning electron microscopy and equilibrium swelling showed that ViTES substantially improved the interfacial interaction between HTVSR and LDH and the crosslinking density of HTVSR, and enhanced the dispersion of LDH sheets in the HTVSR matrix. The possible synergistic suppression mechanism of ViTES/LDH on the tracking and erosion of HTVSR was further studied and demonstrated by the plasma irradiation analysis, thermogravimetry and thermogravimetry-Fourier transform infrared spectrometry. It was indicated that under the high voltage arcing discharge, LDH facilitated the formation of a dense barrier layer consisting of bimetal mixed oxides on the HTVSR surface, exerting outstanding lamellar barrier effect. The further degradation and the generation as well as development of electrical tracking were efficiently suppressed. Our findings provided a new approach to fabricate silicone rubber with excellent tracking and erosion resistance.

The research work focused on the preparation of biobased eugenol benzoxazine (EUBz) using thiourea as amine resource and their conversion into EUBz‐epoxy (EUBz‐EP) blend matrix and EUBz‐EP blend composites. In the present work, thiourea‐based eugenol‐benzoxazine monomer was synthesized using eugenol as phenolic compound, thiourea as amine resource and paraformaldehyde. The molecular structure of monomer was confirmed by FTIR, NMR, and Maldi mass studies. The thiourea‐based EUBz properties were enhanced by the blending of EP resin and reinforced with varying weight percentages of amine functionalized cashew nut shell carbon (f‐CSC). The thermally cured f‐CSC/EUBz‐EP composites possesses a higher glass transition temperature of 202.9°C when compared to that of the EUBz matrix (104.2°C), which might arise due to the higher crosslinking density resulted from the reinforcement of EP resin with f‐CSC. In addition, the hydrophobic behavior of the prepared composite materials is improved by blending the EUBz with EP resin and reinforcing with f‐CSC. The enhancement of the value of contact angle from 80.3° to 105.9° infers the improvement of hydrophobic behavior of f‐CSC reinforced EUBz‐EP blend composites. The corrosion rate and protection efficiency of 5 wt% f‐CSC/EUBz‐EP composites exhibits 0.814 (mm/year) and 99.97%, respectively. Data obtained from different studies suggested that the f‐CSC reinforced EUBz‐EP blended composites can be used in the form of sealants, encapsulants, adhesives, and coatings for different industrial and engineering applications.

Photopolymerization-based 3D printing process is typically conducted using free radical polymerization, which leads to fabrication of immutable materials. An alternative 3D printing of polymeric materials using trithiocarbonate (TTC) reversible addition-fragmentation chain transfer (RAFT) agents has always been a challenge for material and polymer scientists. Herein we report 3D printing of RAFT-based formulations that can be conducted fully open to air using standard digital light processing (DLP) 3D printer and under mild conditions of visible light at blue (λ max = 483 nm, 4.16 mW/cm2) or green (λ max = 532 nm, 0.48 mW/cm2) wavelength. Our approach is based on activation of TTC RAFT agents using eosin Y (EY) as a photoinduced electron-transfer (PET) catalyst in the presence of a reducing agent (triethylamine (TEA)), which facilitated oxygen tolerant 3D printing process via a reductive PET initiation mechanism. Re-activation of the TTCs present within the polymer networks enables post-printing monomer insertion into the outer layers of an already printed dormant object under a second RAFT process, which provides a pathway to design a more complex 3D printing. To our best knowledge, this is the first example of oxygen tolerant EY/TEA catalyzed PET-RAFT facilitated 3D printing of polymeric materials. We believe that our strategy is a significant step forward in the field of 3D printing.

As enantioselectively permeable membrane materials showing high permeability and good self-membrane forming ability, twenty-four well-defined chiral graft copolymers (PPA-graft-OMPS) consisting of flexible chiral oligomethylpinanylsiloxane (OMPS) grafts and a rigid polyphenylacetylene (PPA) backbone were synthesized stepwise in a well-controlled manner. First, synthesized cyclic OMPS monomers containing one or two chiral pinanyl groups were used in living anion ring-opening polymerization to produce the precursors of the corresponding macromonomers whose degrees of polymerization were controlled. Then, by introducing a triple bond at one end of the precursors, the macromonomers were obtained. Finally, PPA-graft-OMPS with controlled numbers of the grafts were synthesized by copolymerization of the macromonomers with phenylacetylene comonomers. The PPA-graft-OMPSs show good self-membrane forming abilities in spite of the very high content of the flexible OMPS unit because of the rigid conjugated backbone. They show stable enantioselective permeation with high permeability for around 1,000 hours based on solution selectivity.

The design of the icephobic surface represents an urgent challenge in the field of surface engineering with high application potential. In this work, we proposed the introduction of icephobic surface properties on the technically relevant material – polyetheretherketone/carbon fibers (PEEK/CF) composite. The developed method utilizes the simple and scalable electrochemical etching to induce a significant increase of surface roughness and subsequent chemical grafting for attachment of hydrophobic fluoro-containing chemical moieties. The surface morphology was characterized at different scales, using the profilometer, confocal microscopy, and atomic force microscopy (AFM) measurements. The success of chemical grafting was confirmed using the X-Ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) measurements. The surface properties were tuned to reach the superhydrophobic and Cassie Baxter water drop states, minimizing the contact area between the drop and sample surface. The icephobic surface properties were tested through the measurements of the time delay of ice formation, precooled drop slipping, and estimation of ice removal force. It was convincingly demonstrated that optimal combination of physical and chemical treatment allows us reaching the icephobic properties on PEEK/CF composite. The main advantages of proposed procedure are its simplicity and scalability, which makes it highly attractive for the practical introduction of icephobic properties in the field of aircraft materials.

An inherent flame-retardant PA6 (FR-PA6) containing polydiphenylsiloxane (PDPS) was synthesized under the action of ethylene glycol (EG) via a facile “2-step” bulk polymerization. Inspiringly, EG acted not only as a ‘chain-linker’ to connect PA6 oligomer with PDPS moiety but also as a charring agent to increase the charring capacity of FR-PA6 after combustion. The prepared FR-PA6 reached 28.3% of limiting oxygen index (LOI), and passed the V-0 level of UL94 test with suppressed melt-dripping. After investigating the char residues and pyrolysis volatiles of FR-PA6 after combustion, the formation of silicon-rich protective layer was proved to be the essential factor to increase the flame retardancy of FR-PA6 via reducing the diffusion of pyrolysis volatiles, restricting the heat transfer and mass loss as well as preventing polymer melts from dripping. This work thus makes a worthwhile contribution to the development of FR-PA6 by offering a novel route that is easily accessible to industrial fabrication.

The utility of profluorescent nitroxides (PFNs) as sensitive probes to detect early stage photodegradation in a cyclic olefin copolymer, TOPAS®, during both natural aging and accelerated aging under laboratory conditions is reported. PFN additives in TOPAS® capture radicals to form fluorescent adducts as the material degrades. The levels of fluorescence detectable from the polymer reflect the degree of free-radical degradation in the material, with the PFN probes delivering enhanced sensitivity over traditional analytical methods for the detection of photodegradation of TOPAS®. The probes are able to highlight polymer degradation occurring within the oxidation “induction” period, where little change can be observed using infrared spectroscopy; however, their efficacy does not extend far beyond this period. The effective probe lifetime however can be significantly extended through the use of common additives such as the UV absorber (Tinuvin P) and a hindered amine stabiliser analogue (1,1,3,3-tetramethylisoindol-2-yloxyl, TMIO).

Abstract Acrylonitrile butadiene styrene (ABS) polymer is used in different areas of engineering based applications, especially in the aviation and automobile industry. It is highly desirable to improve the thermal and mechanical properties of this polymer to enhance its current applicability and to widen its scope for variety of advanced applications. Fabrication of polymer nanocomposite by reinforcing the polymer with nanofiller is one of the key techniques used worldwide to enhance the properties of polymer. In this paper, we have fabricated nanocomposite of ABS using facile solution blending technique with functionalized multi-walled carbon nanotubes (MWCNT) as nanofiller. The weight of functionalized MWCNT in ABS was varied from 1 wt% to 5 wt%. Fourier-transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) were used for characterization of functional group and structural analysis in functionalized MWCNT. The distribution and confirmation of functionalized MWCNT in ABS was analyzed using field emission scanning electron microscope (FESEM) and Raman spectroscopy. Thermal characterization showed considerable improvement in thermal degradation stability and significant reduction in thermal expansion of ABS nanocomposite in comparison to pure ABS. Mechanical characterization using nanoindentation techniques also showed significant enhancement in mechanical properties of ABS nanocomposite in comparison to pure ABS. The 5 wt% nanocomposite showed improvement of 95% and 91% in elastic modulus and hardness respectively in comparison to pure ABS. Dynamic mechanical properties average storage modulus and average hardness improved by 148% and 369% respectively for 5 wt% nanocomposite in comparison to pure ABS. These improved thermal and mechanical properties of ABS using functionalized MWCNT will lead to wider and enhanced applicability of ABS.

Abstract Microemulsions (μEs)-based drug delivery is known to be superior as well as effective due to customizable and easy management, efficiency and capability, and quick drug absorption over a wide range of targets. Herein, two μE formulations were established comprising of clove oil (as oil phase), water (as aqueous phase), Tween-80 (as surfactant), isopropanol, and methanol (as cosurfactant) for formulation A (μE-A) and formulation B (μE-B), respectively, and further used for the encapsulation of an antimuscarinic drug, mirabegron (MBG). Multiple complementary measurements, namely, electrical conductivity (σ), viscosity (η), and optical microscopy, show the existence of phase transition from W/O to O/W μE via intermediate bicontinuous channels. MBG showed long storage stability as well as good solubility i.e. 3.0 and 2.5 wt% at pH 6.4 in optimum μE-A and μE-B, respectively. Furthermore, no apparent aggregation of MBG was observed, as revealed by scanning transmission electron microscopy and peak correlations of IR analysis, suggesting the stability of MBG inside the formulations. Likewise, fluorescence detection senses the interfacial environment of MBG molecules in the examined formulations that could be vital for understanding the mechanism of controlled drug release. Graphical abstract Structural Dynamics of Tween-Based Microemulsions for Antimuscarinic Drug Mirabegron

A series of fatty acid cellulose esters (FACEs) with both various degrees of substitution (from DS = 1.7 to 3) and side chain length were obtained by grafting aliphatic acid chlorides (from C10 to C16) onto cellulose backbone, in a homogeneous LiCl/DMAc medium. These materials were characterized by Fourier Transformed InfraRed (FTIR) and Nuclear Magnetic Resonance of Proton (1H NMR) spectroscopies, as well as Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC), mechanical analyses and chemical resistance to concentrated acid and alkali solutions. Whatever the alkyl chains length and the DS, all samples displayed a layered structure composed of a planar arrangement of parallel cellulosic backbones with fully extended flexible side chains oriented perpendicular to the planar structure without interdigitation. The alkyl chains were able to crystallize as soon as they are long enough. As the DS decreased, the plasticizing effect of the alkyl chains was less pronounced and their ability to crystallize was improved. Regarding the mechanical behavior and the chemical resistance, similar results were observed whatever the DS is.

Nanosilica, multiwalled carbon nanotubes and graphite powder have different effects on guar gum fracturing fluid because of the different morphologies of these nanomaterials. The results showed that the apparent viscosity, temperature tolerance, elastic modulus and tensile strength of nano-hybrid guar gum fracturing fluids were improved by nanomaterials compared to those properties of blank fracturing fluid (without nanomaterials). However, microscopic analysis by SEM and TEM revealed that different nanomaterials played different roles in the network structure of guar gum fracturing fluid. In terms of micro particle size, modified nano-SiO2 (M-NS) played a nuclear point and skeleton role in the fracturing fluid and obviously enhanced the network structure. Hydroxylated multiwalled carbon nanotubes (MWNTs-OH) and guar gum macromolecular chains were intertwined. Graphene oxide (GO) intercalation entered the guar gum molecular chain and the interaction was relatively weak because of its sheet structure.