Polyolefin elastomer grafted unsaturated hindered phenol esters: synthesis and antioxidant behavior

Monomeric antioxidants are synthesized from esterification of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with unsaturated fatty alcohols. The antioxidant activity is evaluated both in blending and radical grafting processes. The effect of chain length and phenolic group is investigated on efficiency of antioxidants. It is demonstrated that the esters of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid exhibit significantly longer induction time. The results of radical grafting reaction shows synthesized antioxidants can be successfully grafted onto polymer chains and the phenolic moiety is functional after extraction process, while pure and commercially stabilized samples are degraded instantaneously. Also, different initiator systems are utilized to enhance the extent of grafting. Among MEK, DCP, and DHBP peroxides, DHBP can be more effective in increasing the antioxidant grafted onto polymer. In addition, possibility of rising in graft content is investigated in presence of redox initiator. Using this approach, polymer-bound antioxidant with prolonged thermal stability can be achieved.     

Injection Molding Micro‐ and Nanostructures in Thermoplastic Elastomers

Flexible polymers such as poly dimethyl siloxane (PDMS) can be patterned at the micro‐ and nanoscale by casting, for a variety of applications. This replication‐based fabrication process is relatively cheap and fast, yet injection molding offers an even faster and cheaper alternative to PDMS casting, provided thermoplastic polymers with similar mechanical properties can be used. In this paper, a thermoplastic polyurethane is evaluated for its patterning ability with an aim to forming the type of flexible structures used to measure and modulate the contractile forces of cells in tissue engineering experiments. The successful replication of grating structures is demonstrated with feature sizes as low as 100 nm and an analysis of certain processing conditions that facilitate and enhance the accuracy of this replication is presented. The results are benchmarked against an optical storage media grade polycarbonate.

     

Effect of Temperature and Relative Humidity on Friction and Wear Properties of Silicone-Based Magnetorheological Elastomer

In this study, the effect of varying temperature and humidity on the friction and wear properties of a silicone-based isotropic magnetorheological (MR) elastomer were examined with an applied magnetic field. Specifically, MR elastomer specimens were fabricated, and a temperature- and humidity-adjustable reciprocating friction tester was employed. The results indicated that the friction coefficient decreased across all tests when a magnetic field was applied. The friction coefficient increased when the temperature increased and slightly decreased following an increase in relative humidity. The wear depth results also exhibited an increasing pattern as the temperature increased and a decreasing pattern when the relative humidity increased. The surface state experienced significant changes under varying temperatures and relative humidity conditions with and without a magnetic field.     

深水管道复合聚氨酯弹性体保温工艺与设备

叙述了深水复合聚氨酯弹性体保温管道涂层结构、保温层涂敷预制工艺和主要设备,给出了深水管道复合聚氨酯弹性体保温生产线典型的工艺流程,并对主要设备的组成及工作原理进行了介绍。     

聚脲弹性体材料耐磨性能的探讨

由不同二元醇与二异氰酸酯合成不同NCO含量的半预聚体(A组分)与端氨基聚醚、胺扩链剂等原料组成的R组分经喷涂设备喷涂成型聚脲弹性体。讨论了在不同摩擦工况下NCO含量、异氰酸酯指数、预聚物类型、耐磨助剂等对聚脲弹性体耐磨性能的影响。结果表明,不同NCO含量在不同摩擦工况下对聚脲耐磨性能的影响不同,干摩擦工况下NCO含量越高,耐磨性能越佳,湿摩擦工况下则是NCO质量分数为15%耐磨性最佳,异氰酸酯指数对聚脲耐磨性能的影响较小,使用聚四氢呋喃二元醇、TDI预聚物和耐磨助剂,可提高不同摩擦工况下聚脲的耐磨性能。     

CaCO_3对EPDM/PP热塑性弹性体性能的影响

在双螺杆挤出机上采用动态硫化的方法制备CaCO3改性三元乙丙橡胶/聚丙烯(EPDM/PP)共混型热塑性弹性体(TPV),研究了CaCO3添加量对热塑性弹性体拉伸性能、流动性能和邵氏A硬度的影响,并对材料进行热失重分析、差示扫描量热分析以及X射线衍射分析。结果表明:CaCO3对TPV有增强的作用,随着CaCO3含量的增加,热塑性弹性体的拉伸强度和断裂伸长率有很大提高,当CaCO3质量分数为9%时,拉伸强度、断裂伸长率、100%定伸应力与邵氏A硬度达到最大值,随后逐渐降低;CaCO3的加入增加了TPV的流动性,使其热稳定性提高,结晶温度降低,使PP的β(300)晶面消失。     

HZMMA对离子聚合物/聚氨酯(脲)弹性体合金增强机制的研究

采用热失重分析(TG)和原位红外研究了含有不饱和双键和羟基的单甲基丙烯酸锌(HZMMA)的化学反应行为;采用X射线衍射(XRD)、扫描电子显微镜(SEM)研究了HZMMA由于其官能团的反应而发生的结构与形态变化。结果表明,针状的HZMMA晶体在引发剂的作用下能自聚形成大小不等的粒子,证实了HZMMA作为反应型增强剂用于制备离子聚合物/聚氨酯(脲)弹性体合金的可能性。以HZMMA作为增强剂,采用预聚体法,以PTMG-1000/甲基二异氰酸酯(TDI)为原料制备预聚物,与自制的混合扩链剂制备出了含有不同量的离子聚合物聚氨酯(脲)弹性体合金,研究了HZMMA的用量对离子聚合物/聚醚型聚氨酯(脲)合金力学性能的影响。当HZMMA的质量分数为0.2%、过氧化二异丙苯(DCP)质量分数为0.2%时,离子聚合物/聚醚型聚氨酯(脲)合金表现出最优的力学性能。     

具有自发可逆形变特性的液晶弹性体

单畴结构的液晶弹性体具有自发可逆形变特性,是一种新型的智能材料,在传感器、微执行器等领域具有重要的应用价值．分别综述了热致型、光致型自发可逆形变液晶弹性体的研究发展现状,分析和阐述了单畴液晶弹性体自发可逆形变特性的原理,并展望了单畴液晶弹性体在人工肌肉和形状记忆材料方面的应用前景．     

纳米纤维素-可聚合低共熔溶剂离子导电弹性体的制备及性能研究

本研究采用紫外光引发原位聚合法将丙烯酸-氯化胆碱合成的可聚合低共熔溶剂（polymerizable deep eutectic solvents,PDES）与纤维素纳米纤丝（cellulose nanofibril,CNF）气凝胶结合,并引入植酸以增强CNF与PDES之间的结合作用,制得含有丰富的共价键和非共价键（氢键）的离子导电弹性体,通过多种现代仪器分析测试其性能。结果表明,该离子导电弹性体在机械性能（应力和应变分别可达0.38 MPa和1378%）、热稳定性、抗冻性、离子电导性（离子电导率可达3.9 mS/m）和紫外屏蔽性方面具有明显优势,同时具有一定的抗疲劳性和弹性,且基于其组装的柔性应变传感器对人体运动表现出快速、稳定、可逆的信号响应。     

乙烯三元共聚合研究现状及展望

从三元共聚合制备高性能聚乙烯(PE)和热塑性弹性体两个领域综述了乙烯三元共聚合机理的研究现状。高性能PE的研究主要集中在聚合过程中的“共单体效应”和“促进效应”;而三元乙丙橡胶的研究重点在对催化剂的研究和二烯烃的选择上。介绍了乙烯三元共聚合的工业化应用情况,总结了目前乙烯三元共聚合研究中存在的问题,并提出今后的研究方向。