基于熔喷过程的等规聚丙烯中拟六方与α混合晶的构成及其稳定性

Constitution and Stability of Mixture of Mesomorphic and α Crystal in Isotactic Polypropylene by Melt-blown Process

采用微型熔喷实验机制备得到等规立构聚丙烯熔喷非织造布,采用广角X射线衍射技术研究了熔喷过程中非织造布生产条件对所形成的非织造布中拟六方和α混合晶晶相结构的影响,采用等温热老化方法研究了混合晶的热力学稳定性及拟六方晶向α晶转变的热力学规律。结果表明,受热风牵伸和室温冷却的共同作用,等规立构聚丙烯熔喷非织造布在成型过程中,易形成含α晶型与拟六方晶型的混合晶。混合晶中α晶与拟六方晶型的比例随牵伸风力的增大和熔体冷却成型时温差的减小而增加。温度高于70℃的热老化可促使混合晶中拟六方晶型向α晶型转变。混合晶晶粒尺寸随α型晶体比例增加而增大。

Constitution and stability of mixture of mesomorphic andαcrystal for isotactic polypropylene（i-PP）nonwovens,formed in self-made micro melt-blown experimental mechanism,were studied with wide Angle X-ray diffraction（XRD）technology.Influence of technique conditions on mixed crystal structure was investigated.The results showed that formation of mixed crystal was effect by the synergy of drafting wind force and cooling condition during forming the nonwovens.Proportion ofαcrystal in mixed crystal increases when decease of temperature difference between melt temperature and room temperature,and also with increase of drafting force.Thermal aging above 70℃ can promote the fast transformation from mesomorphic crystal form toαcrystal form.The size of the mixed crystal grain is related to the proportion ofαcrystal form.