热牵伸行为对COC/PETG热收缩微孔薄膜结构和性能的影响

Study on the effect of heat stretching behavior on COC/PETG microvoid shrink film

利用单向热牵伸法,在PETG收缩薄膜中添加25%(质量分数)COC,在一定的温度和牵伸比例下制备了内部含有微孔结构的高收缩率薄膜。利用SEM、紫外-分光光度计、收缩率测试仪、电子拉伸机等研究了热牵伸行为对薄膜内部结构、力学性能、收缩应力、收缩曲线以及紫外线透过性能的影响。结果发现,COC/PETG属于共混不相容体系,一定温度下的热牵伸行为造成了COC与PETG的相分离,在COC周围产生2~10μm的微孔结构;随着热牵伸温度的提高,95℃下的横向收缩率逐步降低,收缩应力逐步降低,紫外线透过率变化不大;随着热牵伸比例的增加,95℃下的横向收缩率逐步增大,收缩应力逐步降低,紫外线透过率变化不大;当m(COC)/m(PETG)=25∶75时,在拉伸温度80℃、拉伸比例5.0倍的条件下,可获得50μm厚度、0.95g/cm3超低密度、72%超高横向收缩率、99%以上紫外线阻隔效果的稳定的热收缩微孔薄膜。

COC/PETG shrink film with microvoid was manufactured by using single heat stretching process. The film surface morphology, cross section pattern, mierovoid structure, film shrink behavior and thermal property were studied by SEM, DSC, Ultraviolet spectrophotometer, shrinkage tester, shrink force tester, electronic tension machine, etc. The result showed that COC/PETG blending system belongs to incompatible system during extrusion process and microvoid structure could be formed during heat stretching process. The shrinkage of COC/PETG blending system under 95 ℃ increased with the decrease of stretching temperature and increase of stretch ratio. The shrink force decreased with the increase of stretching temperature and stretching temperature. When COC/PETG = 20wt%/80wt% blending system was stretched under 80 ℃ and 5.0 ratios, microvoid structure with 25% porosity was achieved, stable and 72% high TD shrinkage under 95 ℃ water bath was achieved, over 99% UV light under 200-400 nm wavelength was blocked by the microvoid formed during heat stretching process.