热拉伸过程中PE–UHMW/PE–HD共混纤维的晶体结构演变

将超高分子量聚乙烯(PE–UHMW)与高密度聚乙烯(PE–HD)按照质量比为6︰4进行共混熔融纺丝,并对初生丝进行高倍热拉伸制得PE–UHMW/PE–HD共混纤维。利用广角X射线衍射、差示扫描量热、声速取向试验等方法研究了PE–UHMW/PE–HD共混纤维在热拉伸过程中的晶体结构演变过程。研究显示,随着热拉伸过程的进行,纤维的分子链沿纤维的轴向取向度逐渐增加,熔融峰温度逐渐升高,结晶度逐渐增加;沿径向的晶粒尺寸逐渐减小,而沿轴向的晶粒尺寸逐渐增加,即形成了更细长的晶粒;晶体的取向度逐渐增加。当拉伸倍数由1增大至6时,上述现象变化显著,当拉伸倍数由9增至15时,上述现象变化缓慢。与PE–HD共混后的纤维结晶度、晶体取向度和分子链取向度更高,晶粒更加细长。

Crystal Structure Evolution of PE-UHMW/PE-HD Blend Fibers During Hot-drawing Process

The ultra-high molecular weight polyethylene (PE-UHMW)/high-density polyethylene (PE-HD) blend as-spun filaments were prepared by melt spinning method,and the mass ratio of the PE-UHMW and PE-HD in the blend was 6 :4. The as-spun filaments were hot drawn to obtain PE-UHMW/PE-HD fibers. The crystal structure evolution of the fibers during the hot-drawing process was studied by the means of wide-angle X-ray diffraction,differential scanning calorimetry,sound velocity orienta-tion test and so on. The results show that,with the hot-drawing ratios increasing,the molecular chain orientation degree along the axial direction,melt peak temperature and crystallinity of the fibers gradually increase,the grain size in the radial direction gradually decreases and in the axial direction gradually increases,indicating that thinner grains is formed during the hot-drawing process,and the crystal orientation degree of the fibers gradually increases also. The variation trend of the above phenomenon is obvious with the hot-drawing ratios increasing from 1 to 6 and slow with the hot-drawing ratios increasing from 9 to 15. Blending with PE-HD can improve the crystallinity,crystal orientation degree and molecular chain orientation degree of the fibers,and form the thinner grains.