聚乙烯管材中晶点的结构表征及分析  

Structural Characterizations and Analysis of Crystal Points in Polyethylene Pipes

作　　者：张晓伟 李玉娥[1] 张伟[1] 刘张硕 刘云鹏 华晔[1] ZHANG Xiaowei;LI Yu'e;ZHANG Wei;LIU Zhangshuo;LIU Yunpeng;HUA Ye(Sinopec(Beijing)Chemical Research Institute Co.,Ltd.,Beijing 100013,China)

机构地区：[1]中石化(北京)化工研究院有限公司,北京100013

出　　处：《塑料工业》2024年第8期123-129,共7页China Plastics Industry

摘　　要：通过光学显微镜、扫描电子显微镜、分子量分布、差示扫描量热仪、傅里叶变换红外光谱仪等表征手段以及连续自成核退火热分级法对聚乙烯管材表面的晶点进行了详细的表征与分析,研究了管材表面晶点的组成和分子链结构,分析了晶点形成的原因。结果表明,聚乙烯管材表面的晶点呈现局域态的晶片堆积结构,同时有一些裂纹的产生,凸起的晶点区域由分子量较高的高分子链段构成,在加工过程中,高分子量链段部分移动较慢,容易缠结而形成晶点。相较于样品无晶点的区域,有晶点区域的结晶焓较低,结晶温度较低,熔融焓较低,结晶度也较低。热分级结果显示,样品有无晶点区域的差异主要体现在高温熔融区,样品有晶点区域的高温熔融峰位都较低,这表明晶点区域的分子链结构规整度低,所形成的片晶厚度较小。对比3种由不同管材专用料所制成管材样品表面晶点之间的区别,发现共聚单体链段结构越长,所形成的晶点较大,高分子量部分含量越高,所形成的片晶厚度也更大。The crystal points on the surface of the polyethylene pipes were characterized and analyzed in detail by the optical microscope,scanning electron microscopy,molecular weight distribution,differential scanning calorimetry,Fourier transform infrared spectroscopy and successive self-nucleation and annealing fractionation.The compositions and the molecular chain structures of the crystalline points were investigated,and the reasons for the formation of the crystalline points were also analyzed.The results indicate that the crystal points on the surface of the polyethylene pipes present a lamellar stacking structure in the localized state,along with the generation of some cracks.The raised crystal point regions consist of polyethylene chain segments with high molecular weight.In the process of fabrication,the high molecular weight chain segments move slowly and tend to entangle,forming the crystal points.Compared to the regions of the samples without crystalline points,the regions with crystalline points have lower enthalpy of crystallization,lower crystallization temperature,lower melting enthalpy and lower crystallinity.The results of the successive self-nucleation and annealing fractionation indicate that the major differences between the samples with and without crystal points are in the high temperature melting regions.The high-temperature melting peaks in the regions of the samples with crystal points are lower,which indicates that the molecular chain structures in the crystal point regions are less regular,and the thickness of the lamellar crystals formed is smaller.Comparing the differences between the crystal points on the surface of the pipes made from different raw materials,the longer chain structures of the copolymers result in larger crystal points,and the higher content of the high-molecular-weight portion results in larger thickness of the lamellar crystals.

关 键 词：聚乙烯管材 晶点 分子量分布 结晶度 

分 类 号：TQ325.12[化学工程—合成树脂塑料工业]