管材专用PPR的等温结晶动力学

Isothermal crystallization kinetics of PPR pipe resin

研究了管材专用无规共聚聚丙烯(PPR)的结晶温度和等温结晶行为,利用Avrami方程对等温结晶过程和动力学进行了分析。结果表明:北欧化工公司的PPR1具有更高的结晶温度、结晶度以及更快的结晶速率。同一结晶温度条件下,国产PPR3的结晶度达到一半的时间略高于其他PPR。利用Hoffman-Lauritzen结晶动力学理论计算得到了PPR的成核常数和结晶生长时大分子在垂直于分子链方向的折叠表面自由能(σ_(e)),与其他试样相比,PPR1的σ_(e)最低,PPR3的σ_(e)最高,结晶速率最慢。通过偏光显微镜照片可以发现,PPR1的球晶尺寸最小,PPR3和PPR4的球晶较大,球晶尺寸比较接近。

The crystallization temperature and isothermal crystallization behaviors of polypropylene random copolymer(PPR)resins used for pipes were investigated.The Avrami equation was employed to describe the isothermal crystallization kinetics of the PPR samples.The results show that the PPR1 produced by Borealis has higher crystallization temperature and crystallinity as well as a faster crystallization rate.The semi-crystallization time of the domestic resin PPR3 is slightly faster than that of other PPR samples at the same crystallization temperature.The nucleation constant K_(g) and the surface free energy of the developing crystals(σ_(e))that is normal to molecular chains are calculated according to the Hoffman-Lauritzen theory.PPR1 obtains the lowest σ_(e) than other PPR samples,while PPR3 exhibits the highest σ_(e),indicating its slowest crystallization rate.The polarized light microscopy(PLM)results indicate that the spherulite size of PPR1 is the smallest,and that of PRR3 and PRR4 are quite similar and larger than that of other samples.