糖类物质辅助凝固天然橡胶的加速贮存特性研究

Coagulation of natural rubber latex with sugar substance is a kind of green processing technology of natural rubber, through which the better performance of natural rubber (NR) can be obtained than the widely adopted acid coagulation technology at present. Researchers have paid close attention on it. However, different sugars profoundly affect the storage properties. Disaccharide and polysaccharide have an obvious effect on the oxygen aging resistance, but the mechanism remains unclear. To master the influence of different sugar substance on storage characteristics of natural rubber, it needs to examine the chemical group change in the NR molecular chains and the resulted storage properties such as P0, PRI, and gel content in detail..We use industrial glucose, starch, trehaose and so on to coagulate the natural rubber latex to prepare high quality natural rubber. Through accelerated storage test, the influence of the molecular structure and constituent change of natural rubber on storage properties is studied. In addition, the effect of sugars on the storage stability of natural rubber and action mechanism would be unclosed and the relationship between the chemical group transform and the characteristics of process and vulcanization would be illustrated. Furthermore, the research can provide reference methods for the effective storage forecasting of natural rubber and promoting the further application of technology of natural rubber coagulation with sugars. In addition, the research can further enrich the theory how to control the natural rubber quality.

糖类物质辅助凝固天然胶乳是一种绿色的天然橡胶加工技术，较目前生产普遍采用的酸凝固技术能制备出性能更优的天然橡胶，这已引起了科研工作者的高度关注。然而不同种糖类物质辅助凝固的天然橡胶，其贮存性能存在差异。二糖和多糖对抗氧老化性影响明显不同，但机理尚不清楚。为掌握不同糖类物质对天然橡胶贮存特性的影响，需要详细研究在加速贮存过程中不同糖类对天然橡胶分子链上基团的转变及其所导致的P0、PRI、凝胶含量等贮存特性的影响。.本研究选用工业葡萄糖、淀粉、海藻糖等来辅助凝固天然橡胶，通过加速贮存试验，研究天然橡胶贮存过程中分子链结构和橡胶组分变化对贮存特性的影响，揭示糖类物质对天然橡胶贮存稳定性的影响和作用机制，探寻天然橡胶贮存过程中分子链基团变化与加工、硫化特性变化之间联系，为天然橡胶的有效贮存预测以及糖类物质辅助凝固天然橡胶技术的进一步应用推广提供方法参考，为天然橡胶质量的控制提供理论依据。

独特的组成和分子结构使天然橡胶具有贮存硬化现象，这极大影响生胶质量一致性。迄今，天然橡胶贮存硬化机制尚存争议。营养源糖分在天然橡胶生物凝固中发挥重要作用，可改变橡胶原生分子形态结构。课题筛选糖分辅助凝固天然橡胶工艺，拟合分析天然橡胶贮存的环境效应，探究天然橡胶分子结构及天然生胶性能差异，研究端基修饰对糖分辅助凝固天然橡胶的贮存特性的影响，比较糖分辅助凝固与其它凝固方式对天然橡胶贮存特性及结构差异，揭示了天然橡胶加速贮存过程中分子结构演变及糖分对天然橡胶加速贮存特性作用的分子基础。结果表明，糖分辅助凝固天然橡胶均达到国产五号胶标准，红糖、乳糖、木薯淀粉是较优凝固糖分。贮存温度增加，直线方程能较好地拟合天然橡胶△P，指数函数能拟合PRI趋势，天然生胶中分子链以支化链形态为主，悬尾链大于80%。贮存湿度对△P影响显著，与温度对分子作用本质差异明显。负压贮存天然橡胶，△P随压力增加而减小。天然橡胶本体的贮存硬化比表面更明显。红糖和葡萄糖辅助凝固天然橡胶分子支化度低，分子近线性，白糖则支化度较高，而海藻糖和木薯淀粉支化度为中间值。低聚合度糖分使天然橡胶α晶层较完善。葡萄糖参与胶乳生物代谢作用时，ω-端基和α-端基的响应性不同，葡萄糖对新鲜胶乳中的Ca2+和Mg2+有螯合作用；管道理论数据显示糖分辅助凝固天然橡胶分子链缠结比分子端基交联或缔合对弹性模量的贡献大。糖分辅助凝固由不同方法进行链端基修饰的天然胶乳，发现△P均大幅度减小，ω端蛋白修饰比α端基修饰影响大。半乳糖辅助凝固天然生胶网络结构贮存稳定好。天然橡胶贮存过程中凝胶是渐次成核，混杂增长机制。糖分主要通过其微生物代谢和对金属离子螯合作用，重构天然橡胶分子结构和分子网络结构是糖分影响加速贮存特性的分子基础。项目成果对天然橡胶质量一致性调控具有重要意义，为糖类物质辅助凝固天然橡胶技术的应用推广提供重要理论参考。