聚乳酸热收缩薄膜的制备与拉伸回复性能研究

Preparation and Tensile Recovery Properties of Polylactic Acid Heat Shrinkable Film

目的研究2种环保型改性剂碳酸丙烯酯(PC)和聚碳酸亚丙酯二醇(PPC)对聚乳酸(PLA)的增塑效果,以及PLA/PC、PLA/PPC这2种热收缩薄膜在拉伸回复过程中的热收缩性能、结晶性能和透氧性能。方法采用双螺杆挤出机将PC、PPC分别与PLA共混改性,采用差示扫描量热仪(DSC)、傅里叶变换衰减全反射红外光谱(ATR–FTIR)、X射线衍射仪(XRD)、电子万能试验机、压差法气体渗透仪研究PC、PPC分别对PLA的改性效果,以及PLA/PC、PLA/PPC 2种热收缩薄膜在拉伸回复过程中的热收缩性能、结晶性能和透氧性能。结果PC改性后的热收缩薄膜拉伸强度降低至16.8 MPa,断裂伸长率提高至26.6%,氧气透过率(To)可以达到1020.4 cm^(3)/(m^(2)·d·Pa),而回复率(Rr)仅有27.5%。PPC改性后的热收缩薄膜拉伸强度降低至23.6 MPa,断裂伸长率提高至12.5%,且PLA/PPC热收缩膜的Rr可以达到83.3%;在拉伸后T o仅为915.8 cm^(3)/(m^(2)·d·Pa),阻氧性能较好。结论PLA/PC热收缩薄膜的柔韧性得到提高,但易发生应力松弛削弱分子链的回复应力,导致热收缩性能变差,氧气渗透难度减弱,To增高。PLA/PPC热收缩膜具有较好的柔韧性,在拉伸后,结晶度增大,分子链能够被更好的定向,热收缩性能变好;分子链的规整度提高,氧气渗透难度增大,T o降低,阻氧性能提高。

The work aims to study the plasticizing effect of two environment-friendly modifiers of propylene carbonate(PC)and polypropylene carbonate glycol(PPC)on polylactic acid(PLA)and the thermal shrinkage,crystallinity and oxygen permeability of PLA/PC and PLA/PPC heat shrinkable films during tensile recovery.PC and PPC were blended with PLA by twin screw extruder.Differential scanning calorimeter(DSC),Fourier transform attenuated total reflection infrared spectroscopy(ATR-FTIR),X-ray diffractometer(XRD),electronic universal testing machine and differential pressure gas permeability instrument were used to study the modification effect of PC and PPC on PLA and the thermal shrinkage,crystallinity and oxygen permeability of PLA/PC and PLA/PPC heat shrinkable films during tensile recovery.The tensile strength of the heat shrinkable film modified by PC decreased to 16.8 MPa,the elongation at break increased to 26.6%,the oxygen transmission rate(To)could reach 1020.4 cm^(3)/(m^(2)·d·Pa),and the recovery rate(Rr)was only 27.5%.The tensile strength of the heat shrinkable film modified by PPC decreased to 23.6 MPa,the elongation at break increased to 12.5%,and the Rr of PLA/PPC heat shrinkable film could reach 83.3%.After stretching,the To was only 915.8 cm^(3)/(m^(2)·d·Pa),showing good oxygen resistance.The flexibility of PLA/PC heat shrinkable film has been improved,but stress relaxation is prone to weaken the recovery stress of molecular chains,resulting in poor heat shrinkable properties,reduced difficulty in oxygen penetration,and increased To.PLA/PPC heat shrinkable film has good flexibility.After stretching,the crystallinity increases,the molecular chain can be well oriented,and the heat shrinkable property is good.The regularity of molecular chain increases,oxygen penetration difficulty increases,To decreases and oxygen resistance improves.