Regulation Of Crystallization And Toughening Behavior Of Poly (Ethylene Terephthalate)

In this work,in order to improve the crystallization rate and impact toughness of thermoplastic polyester polyethylene terephthalate(PET),aromatic amides Star NU-100,inorganic filler graphite(Gr),small molecular substance m-pentadecyl phenol(PDP)and thermoplastic elastomer TPEE were used as modifiers to mediate the crystallization and toughening behaviors of poly(ethylene terephthalate)(PET)with melt blending method.Differential scanning calorimeter(DSC),wide-angle X-ray diffraction(XRD),polarizing microscope(POM),tungsten filament scanning electron microscopy(SEM)and mechanical properties test were used to study the effects of these substances on the crystallization and melting behavior,crystal structure,spherulite morphology and mechanical properties of PET.Firstly,PET/NU-100 composites were prepared by melt blending,and the effects of aromatic amides NU-100 on the properties of PET were investigated.DSC results showed that NU-100 had obvious nucleation effect on the crystallization of PET.When the content of nu-100 in PET matrix was 0.8wt%,the crystallinity reached 40.57%,the nucleation efficiency was 78.30%,and the crystallization rate was also greatly improved.At the same time,the addition of NU-100 did not change the crystal form of PET,but the nucleation density increased and the crystal grains were more refined.The mechanical test results showed that the impact strength of PET/NU-100 composites increased first and then decreased with the increase of NU-100 content.When the content of NU-100 was 0.2wt%,the impact strength of the composites was 0.244 KJ/m2,increasing by 39%.Secondly,the effects of inorganic filler graphite(Gr)on the crystallization behavior,crystal structure and mechanical properties of PET were studied.The results showed that graphite(Gr)could effectively improve the crystallization behavior of PET.When the content of Gr was 0.1 wt%,the crystallization peak temperature and crystallinity were increased by 10.79 C compared with pure PET.XRD test results showed that Gr had no significant effect on the crystal structure of PET,while the number of crystal nucleus increased and the spherulite size tended to homogenize.At the same time,the addition of Gr increased the bending strength of PET,and the impact strength decreased.That is to say,Gr played a role in enhancing the impact toughness of PET and weakening its impact toughness.Subsequently,thermoplastic elastomer TPEE was added to modify the impact toughness of polyethylene terephthalate(PET),and the crystallization behavior and mechanical properties were investigated.The results showed that the addition of TPEE into PET/Gr composites slowed down the crystallization rate of the composites and affected the crystallization properties of the composites.With the increase of TPEE content,the crystallization hindering behavior was more obvious.However,compared with pure PET,Gr and TPEE promoted the crystallization behavior of PET,accelerated the crystallization rate of PET,and had no obvious effect on the crystal structure of PET.With the increase of TPEE content,the intensity of the diffraction peak increased and the grain size increased.SEM results showed that the number of folds on impact section increased,and the number of crazes and shear bands also increased gradually,showing typical plastic fracture characteristics.In addition,the addition of TPEE reduced the rigidity of PET,but improved the impact toughness significantly.Finally,the small molecule PDP and Gr were blended with different mass ratios and then added into PET to modify it.The results showed that the crystallization temperature of PET/Gr/PDP increased with the addition of Gr-PDP with different ratios,the crystallization rate increased,and the crystal structure of the composites did not change significantly.At the same time,the impact energy and impact strength of composite PET/Gr/PDP increased,and the impact energy and impact strength showed an increasing trend with the increase of gr-pdp ratio.