Structure And Dynamic Mechanical Properties Of Degradable Polymer/Kaolin Nanocomposites

With the deterioration of environment and people’s pursuit of quality life, biodegradable materials, arousing more and more concern among people, have become a research focus. PLA, an important biodegradable material, has high mechanical strength, good plasticity, etc. The raw materials of PLA can come from renewable resources such as grains, plant straws, which is completely free from dependence on oil resources. In the grim situation of global environmental pollution and lack of resources, the researches on PLA and other biodegradable polymers have important social significance and economic value. However, there are many problems such as hard and brittle texture, low heat distortion temperature and low melt strength during the processing and utilization, which have seriously hampered the application of PLA. Therefore it requires some necessary modification.PLA/PHA/Kaolin10, PLA/PBAT/KaolinlO nanocomposites were prepared by melt-mixing, and the crystallinity, dynamic mechanical performance, rheological behaviors, mechanical properties and surface structure of the blends were studied respectively with DSC, DMA, rheometer, universal testing machine and scanning electron microscope. It also discusses the effects on rheological properties, mechanical properties and creep of PLA/PHA matrix and PL A/PH A/Kaolin from pure kaolin and titanate coupling agent.The results indicated that cold crystallization temperature of PL A/PH A/Kaolin10decreased gradually, dropped by12.5℃, and crystallization capacity improved. Crystallinity increased from21.65%to35.22%, an increase of62.68%. DMA showed that glass transition temperature of the blends increased first and then decreased with the increase of Kaolin10content. At the melting state, viscosity of the blends decreased when sheer rate increased, which showed pseudoplastic fluid. In addition, the storage modulus (G’) and loss modulus(G") decreased with the increase of Kaolin10. When the addition of KaolinlO achieved4%, the material notched impact performance of PLA/PHA/KaolinlO blends improved remarkably. SEM observations showed that a small amount of Kaolin10could disperse homogeneously in the blends, and it could remarkably improve toughness of the blends.The addition of KaolinlO greatly affected the crystallization, rheological behavior and mechanical properties of PLA/PBAT matrix. With the increase of Kaolin10, Tg decreased gradually, which indicated that the moving ability of molecular chains enhanced. The crystallization temperature and initial cold crystallization temperature significantly reduced, which indicated the crystallization ability improved greatly. In addition, melting peak of the blends came to be two peaks by a single peak, and Tml decreased gradually with KaolinlO increased while high temperature peak became strong. When Kaolin10achieved2%, tensile strength, tensile modulus and elongation rate reached the maximum, indicating that an appropriate amount of Kaolin10played a reinforcing and toughening effect. The results of impact strength test were consistent with tensile test.Pure kaolin enhanced G’and G" of PLA/PHA matrix, but excess nanoparticles agglomerated easily, and enhancement was not obvious. The introduction of2%kaolin can enhance the stability of PLA/PHA matrix, especially in high temperature. PLA/PHA/G2was easier to be soft and had better processing performance below185C. Pure kaolin improved the tensile modulus of PLA/PHA matrix, but also made the blends brittler. The stain of material reduced with pure kaolin, indicating that kaolin increased the ability of anti-deformation.As the coupling agent increased, G’and G" of PLA/PHA/Kaolin significantly reduced, and the introduction of excessive coupling agent reduced the critical strain of linear-nonlinear transformation. Each sample was able to maintain stable linear viscoelastic behavior at least30min at190C. Kaolin5improved the modulus and flexibility of PLA/PHA matrix, a performance of strong and tough characteristics, and excessive coupling agent made the matrix turn to be very brittle instead. The final stain of PLA/PHA matrix decreased to1.08%with Kaolin5, indicating that the material has better creep resistance, and it made dimensional stability of the matrix worse by excessive coupling agent.