透明聚酰胺聚集态结构与拉伸性能的热处理效应

Thermal Treatment Effects on the Microstructure and Tensile Properties of Transparent Polyamides

研究了透明聚酰胺PAPACM12和PAMACM12的基本性能以及热处理对透明聚酰胺聚集态结构和应力应变行为的影响,着重分析并对比了重复单元结构相近的透明聚酰胺在聚集态结构上的差别.示差扫描量热法(DSC)的结果表明,PAPACM12的玻璃化转变温度为135.6°C、熔点为244.6°C,PAMACM12的玻璃化转变温度为160°C.对比傅里叶变换红外光谱(FTIR)谱图的结果,PAPACM12在对应了酰胺基团变形振动的961 cm^(-1)结晶谱带与PAMACM12有明显差异.经过退火处理后,PAPACM12在一维广角X射线衍射(WAXD)曲线上出现了2个衍射峰,其晶面间距分别为0.50和0.45 nm,对应于聚酰胺的α晶型,这是冷结晶所致;PAMACM12经过热处理后仍为无定形状态.退火后处理后PAPACM12的拉伸强度得到了改善、断裂强度下降,这也是冷结晶过程中微晶含量不断增加所致,而PAMACM12的拉伸强度和断裂强度均有所下降.

The properties and thermal treatment effects on the microstructure and stress-strain behaviors of two transparent polyamides, poly(4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAPACM12) and poly(3,3′-dimethyl-4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAMACM12), were studied in this work. Differences in microstructure and the corresponding properties between the two polymers with similar repeating units were found out via comparative analyses. PAPACM12 behaved as a microcrystalline polymer with a distinct glass transition temperature of 135.6 ℃ and a melting point at 244.6 ℃. By contrast, PAMACM12 showed a higher glass transition temperature of 160 ℃, as the elimination of thermal history reduced a lot its crystallinity. Besides, cold crystallization was observed for PAPACM12 during the heating process, which gave rise to an exothermic peak on the DSC curve at 174 ℃. Comparing the Fourier transform infrared spectroscopy (FTIR) spectra of two polyamides, the band of 961 cm^-1 as a crystalline indicator was found present for PAPACM12 but absent for PAMACM12. This observation was consistent with the DSC results obtained above. Further, thermal treatment effects on the aggregate structure and tensile properties were investigated. Experimental results showed that quenching treatment could reduce the yield strength and elongation at break for both samples. Besides, the cold crystallization of PAPACM12 after annealing let two diffraction peaks occur on the integrated pattern of wide-angle X-ray diffraction (WAXD), which corresponded to the d-spacings of 0.50 and 0.45 nm, respectively. These two values approximated to the ones for (100) and (010/110) lattices in the AABB-type polyamides. Moreover, the tensile strength of PAPACM12 increased while the fracture strength decreased after annealing, for cold crystallization process conduced to an improved microcrystalline formation. Differently, both tensile strength and fracture strength of PAMACM12 were decreased by annealing, but its optical transparency was barely affected.