Study On Mechanical Properties And Crystal Structures Of The α Phase In IPP During The Tensile Deformation Process

It is well-known that the deformation-induced structure change in semicrystallinepolymers can induce the manipulation of mechanical properties. Upon deformation,the isotropic structure of polymeric materials can be transformed into an anisotropicstructure due to the orientation of polymer chains. Hence, the mechanisms of suchtransformations and how they are related to the resulting morphology, structure, andphysicomechanical properties are of great scientific interest and practical importancein polymer science.In this study, we use iPP polymer doped with new α nucleating agent ZC-2as amodel to study the effect of temperature on the structure changes of iPP duringuniaxial tensile deformation at different temperatures (i.e.,30℃,60℃,100℃,120℃).It turned out that, the strain-stress curves demonstrated the existence of a commonscenario: the yield strain is invariant against variations in temperature. To correlateproperties with structure, in situ characterizations have been carried out duringpolymer deformation. The main experimental techniques were wide-angle X-rayscattering (WAXS) and small-angle X-ray scattering (SAXS) using synchrotronX-rays. Based on the experimental results, we hypothesize that the yield strain is afunction of degree of crystallinity. Therefore a change in the crystallinity is expectedto lead to a change in the location of the yield strain.An obvious way to change the crystallinity is to change the crystallizationtemperature. α-iPP which isothermal crystallized at25℃,135℃,140℃and145℃were drew at varying temperatures. The results of α-iPP well supported the ideamentioned above. Besides, the results showed that no matter how much content ofnucleating agent, both yield stress and fracture stress of iPP decreased with increasingtemperature, while the tensile elongation at break of high temperature was larger thanthat of lower temperature. The samples exhibited higher elongation at break when thecontent of the nucleating agent was0.2wt%.