A Study of Aggregate Structure, Miscibility and Physical Properties in a series of Natural Rubber Blends

• Main Authors: PEIR-AN TSAI, 蔡培安
• Other Authors: Hsien-Tang Chiu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/80809841412608185539

博士 === 國立臺灣科技大學 === 高分子系 === 94 === In the study, we research the Mooney viscosity, curing rate, morphologies, mechanical properties, post-thermal aging properties and dynamic mechanical properties of a series of nature rubber blends (NR/BR, ENR/CR). Furthermore, we used Neoprene (polychloroprene; CR) latex with the condensation polymers(RF resin) of resorcinol and formaldehyde in traditional RFL dip technology as the adhesion for fabric and NR/BR blends. Under different CR latex contents and treatment conditions, investigated the influence and effect of using CR latex in the adhesion of fabric and NR/BR blends. From these results, we obtained the following results. 1. The study on NR/BR blends The experimental results show that NR has a lower Mooney viscosity, and its initial fluidity is superior to that of BR. Moreover, NR/BR blends tend to have lower Mooney viscosity with increasing NR content. Thus, blending of NR leads to good improvement in BR processibility. Curing rate for NR/BR blends becomes faster with higher curing temperature. Furthermore, curing rate of NR is faster than that of BR. Both scorch time (ts2) and optimum curing time (tc90) of NR/BR blends decrease with increasing NR content. In NR/BR blends, the two peaks corresponding to NR’ Tαn and BR’ Tαb are well separated, meaning that NR/BR blends are immiscible. Moreover, Tαb moves to a low temperature range with increasing NR content, while Tαn moves to a low temperature range with decreasing NR content. In addition, NR surface reveals a domain status of distribution, whereas BR surface shows a uniformly dispersed distribution. Moreover, the fracture surfaces of NR are neater and more even than those of BR. Both tensile and tear strengths of NR/BR blends increase with increasing NR content. BR has higher compression stiffness than NR. The deformation of BR is smaller than that of NR under the same load conditions. In addition, NR has lower air permeability than BR; meaning that the air impermeability of NR is superior to that of BR. NR/BR blends become less gas permeable and achieve better air impermeability with increasing NR content. With regard to aging properties, both tensile stress and strain of NR/BR blends decrease after prolonged aging. In addition, the stress loss of BR is lower than that of NR, meaning that the aging resistance property of BR is superior to that of NR. Furthermore, accumulated thermal history has shifted the glass transition temperature (Tg) of NR/BR blends towards lower temperatures while the loss tangent (tanδ) value increases with prolonged thermal aging. 2. The study on ENR/CR blends The experimental results of ENR/CR blends show that the Mooney viscosity decreased gradually. Plasticization was most pronounced at an ENR/CR ratio of 75/25, and is thus the easiest to process. Owing to the ring-opening of the epoxy group of ENR, the rate of crosslink formation is much faster than that of CR at higher temperature. The vulcanized rate increased with increasing ENR content. The results indicated that 175°C and 5 minutes were the optimum processing conditions for ENR/CR blends. The DMA spectra showed a single damping peak for the ENR/CR blends, which suggests that ENR and CR are miscible. As seen in the Arrhenius plot of frequency against Tg , the activation energy increased with increasing ENR contents. This suggests the existence of interpenetration of these two rubber molecular networks. 3. The study on adhesion of NR/BR blends and textile fabric The experiment result showed that after the fabric is treated with CR latex 100 phr and dried under different drying temperatures, the peel strength of NR100 was the highest and NR0 (pure BR) was the lowest. The best drying temperature for fabric treated with CR latex 100 phr is at 150℃. For vinyl pyridine (VP) latex used to treat fabric in traditional RFL dipping solution, the peel strength of fabric on NR/BR blends is the highest and showed no significant change on the peel strength values of three different kinds of NR/BR blends. When traditional RFL dipping solution is used with CR latex system to treat fabric, the peel strength of NR/BR blends on fabric decreased as the NR content decreased (BR content increased) and CR latex content decreased. When CR latex system was used in the RFL adhesive treatment solution and additives such as cross-linking agent and catalyst were added into CR latex, the peel strength between the fabric and NR/BR blends was increased.