To date, epoxidized natural rubber (ENR) latex is still far from being commercially available for the production of dipped latex goods although the process was reported in 1922. Therefore, the objective of this work is to establish an understanding on the colloidal properties of ENR latex and relate them to coagulation and film formation. To do so, ENR latex was first prepared from low ammonia preserved natural rubber (LATZ) latex and then concentrated (C-ENR) using a patented process via membrane separation technology. NMR was used to determine the epoxidation level and ring opening in the ENR latex. The LATZ latex and both epoxidized latexes (ENR and C-ENR) were characterized for their particle size distribution, morphology, zeta potential and rheological properties. NMR analysis revealed an epoxidation level of 26% with < 2% ring opening. Particle size analysis showed C-ENR latex to have a narrow size distribution with no flocculation upon sonication. Zeta potential analysis as a function of pH showed a lower isoelectric point for C-ENR latex compared to LATZ latex. Zeta potential was also low for C-ENR latex compared to LATZ latex above pH 5 indicating an outward shift in the shear plane of the latex particle due to adsorption of the nonionic surfactant. Rheology of the latexes was studied using steady-state and oscillatory measurements. Elastic overshoot was observed for C-ENR latex at volume fraction (ϕ) of 0.490–0.584 indicating strong particle–particle interaction. The calculated maximum packing fraction (ϕ_p) of C-ENR latex was 0.721 compared to the ϕ_p of 0.815 for LATZ latex. The lower ϕ_p was attributed to the adsorbed nonionic surfactant layer on C-ENR latex particles. Oscillatory measurements showed that C-ENR latex behaved as dominantly elastic material from ϕ of 0.4975–0.584. At ϕ of 0.497 (= 48.5 wt%), the adsorbed polymer layers start to interact with each other. At this ϕ, the calculated adsorbed nonionic surfactant layer thickness (Δ) was 35 nm. As the latex concentration was increased, the latex became more elastic due to the interpenetration and compression of the surfactant layers. At the highest latex ϕ of 0.584 (= 57.6 wt%), tan δ was 0.3 resulting in an Δ of 20 nm. This thick layer of adsorbed surfactant hinders the coagulation of particles by salt during dipping thereby prohibiting the film formation process required to make the latex dipped products.

中文翻译：

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膜分离技术制备的环氧天然胶乳的胶体性能

迄今为止，尽管1922年已经报道了环氧化天然橡胶（ENR）胶乳的生产工艺，但仍远不能从商业上获得。因此，这项工作的目的是建立对ENR胶体性质的了解。胶乳并将它们与凝结和成膜有关。为此，ENR胶乳首先由低氨防腐天然橡胶（LATZ）胶乳制备，然后使用获得专利的膜分离技术进行浓缩（C-ENR）。NMR用于确定ENR胶乳中的环氧化水平和开环。LATZ胶乳和两种环氧化胶乳（ENR和C-ENR）的粒径分布，形态，ζ电位和流变特性均得到了表征。NMR分析显示开环<2％时环氧化水平为26％。粒度分析表明，C-ENR胶乳的粒径分布较窄，超声处理时无絮凝现象。Zeta电位分析与pH的关系表明，与LATZ胶乳相比，C-ENR胶乳的等电点更低。与高于pH 5的LATZ胶乳相比，C-ENR胶乳的Zeta电位也很低，这表明由于非离子表面活性剂的吸附，胶乳颗粒的剪切平面向外移动。使用稳态和振荡测量研究了乳胶的流变学。C-ENR乳胶在体积分数（与高于pH 5的LATZ胶乳相比，C-ENR胶乳的Zeta电位也很低，这表明由于非离子表面活性剂的吸附，胶乳颗粒的剪切平面向外移动。使用稳态和振荡测量研究了乳胶的流变学。C-ENR乳胶在体积分数（与高于pH 5的LATZ胶乳相比，C-ENR胶乳的Zeta电位也很低，这表明由于非离子表面活性剂的吸附，胶乳颗粒的剪切平面向外移动。使用稳态和振荡测量研究了乳胶的流变学。C-ENR乳胶在体积分数（φ）的0.490-0.584指示强颗粒-颗粒相互作用。计算出的最大敛集率（φ _p相比，C-ENR胶乳的）为0.721 φ _p的0.815为拉兹胶乳。较低的ϕ _p归因于C-ENR胶乳颗粒上吸附的非离子表面活性剂层。振动测量结果表明，C-ENR乳胶在0.4975-0.584的ϕ中起主要弹性材料的作用。在0.497的ϕ（＝ 48.5重量％）下，吸附的聚合物层开始彼此相互作用。在这个ϕ，计算出的吸附非离子表面活性剂层厚度（Δ）为35nm。随着胶乳浓度的增加，由于表面活性剂层的互穿和压缩，胶乳变得更有弹性。在最高乳胶ϕ为0.584（＝ 57.6重量％）时，tanδ为0.3，导致Δ为20nm。吸附的表面活性剂的厚层阻碍了浸渍过程中盐的颗粒凝结，从而阻碍了制造胶乳浸渍产品所需的成膜过程。