时域NMR法研究热处理对聚乙烯相结构的影响

Effect of heat treatment on the phase structure of polyethylene studied by time-domain NMR

采用固体时域NMR法研究了热处理前后不同类型聚乙烯的相结构信息。表征结果显示,热处理后,高密度聚乙烯(HDPE)、中密度聚乙烯(MDPE)、线型低密度聚乙烯(LLDPE)、低密度聚乙烯(LDPE)的无定形区分子运动性受限加大;LLDPE和LDPE的界面区分子运动性受限加大;聚烯烃弹性体(POE)的晶区和界面区分子运动性受限加大,无定形区分子运动更自由;HDPE和MDPE晶区和无定形区增多,界面区减少;LLDPE和LDPE晶区基本不变,界面区减少,无定形区增多,且在运动自由区有新的相区出现;POE热处理后晶区减少,无定形区和界面区增多。时域NMR法具有简便、快捷,设备易于维护的优点,在表征聚烯烃相结构方面具有独特优势,能够通过一次实验就得到相结构的全面信息。

The phase structure of different type polyethylene(PE)before and after heat treatment was studied by solid time-domain NMR.After heat treatment,confinement on the molecular mobility in amorphous region of high density PE(HDPE),medium density PE(MDPE),linear low density PE(LLDPE)and low density PE(LDPE)is increased,and confinement on the molecular mobility in crystalline-amorphous interface of LLDPE and LDPE is increased,meanwhile confinement on the molecular mobility in crystalline region and crystalline-amorphous interface of polyolefin elastomer(POE)is increased,molecular mobility in the amorphous region becomes more free.Both crystalline region and amorphous region fraction increased in HDPE and MDPE.For LLDPE and LDPE,amorphous region fraction increased while crystalline-amorphous interface decreases,in addition a new phase appeared.Both amorphous region and crystalline-amorphous interface fraction in POE increased while crystalline region decreases after heat treatment.Solid time-domain NMR method is convenient and fast,the equipment is easy to maintain,the phase structure of polyolefin can be obtained through only one experiment,indicating it has unique advantages in characterizing the phase structure of polyolefin.