Preparation, Structure And Properties Of Plla/Nbr Thermoplastic Vulcanizates

In this thesis,we discussed the preparation,structure and properties of PLLA/NBR-thermoplastic vulcanizates (PLLA/NBR-TPV) which is made by using dynamic vulcanization technology. The originality of this thesis lies in the fact that we adopt PLLA as the thermoplastic resin composition which is biodegradable and derived from natural. This makes PLLA/NBR-TPV partly biodegradable while maintaining high elasticity and thermal plasticity. At the same time,dynamic vulcanization temperature is lower than reported in literatures that dynamic vulcanization temperature is20～30℃higher than the melting point of resin phase. This not only reduces the energy consumption,also prevents PLLA from degradation at high temperature. And we prepared PLLA/NBR-TPV adopting simple process equipment and process conditions with excellent properties that the tensile strength of PLLA/NBR-TPV can be up to15MPa and the elongation at break of PLLA/NBR-TPV can be up to300%.Through regulation of formula and optimization of processing conditions,we got the suitable technological conditions to prepare f PLLA/NBR-TPV. And the influence of formulation factors on the performance and structure of the PLLA/NBR-TPV was discussed. The results showed that the ratio of NBR/PLLA,curing agent and accelerator system have some influence on the performance of PLLA/NBR-TPV. By changing the ratio of NBR/PLLA from7:3to4:6,we prepared PLLA/NBR-TPV with better performance and different ratio of NBR/PLLA,especially when NBR/PLLA is5.5:4.5, the properties of NBR/PLLA-TPV is optimal. The content of curing agent and different promoter system affect the phase structure and the performance of PLLA/NBR-TPV by influencing the crosslinking and crushing process of NBR during dynamic vulcanization, when the sulfur vulcanization agent dosage is1phr and the accelerator system is PX/BZ/T.T,NBR/PLLA-TPV has optimal performance.We investigated the morphology of PLLA/NBR-TPV with different ratio of NBR/PLLA and different dynamic vulcanization time by TEM. The results showed that PLLA/NBR-TPV has PLLA dispersed in NBR matrix when the ratio of NBR/PLLA is7:3,also its rheology properties is poor and difficult to be molded. With increase of the relative contents of PLLA,the continuity of PLLA phase increases,while the size of NBR phase decrease. When the ratio of NBR/PLLA is below6:4,the island structure of NBR dispersed in PLLA matrix was observed. When the ratio of NBR/PLLA is5.5:4.5,the phase structure of PLLA/NBR-TPV evolved into the island structure with NBR as the dispersed phase from bicontinuous structure with the extension of dynamic vulcanization time. PLLA/NBR-TPV has the optimum properties when vulcanization time is400s.