Study On Synthesis And Properties Of Composite PET Catalyzed By Nano-Zinc Borate

Polybutylene terephthalate?PET?is a typical semi-crystalline thermoplastic polyester obtained by esterification and polycondensation of terephthalic acid?PTA?and ethylene glycol?EG?.PET has good mechanical properties,fiber forming,abrasion-resistant capability,creep resistance and insulation properties.It is widely used in fiber,film,PET bottles and other fields.At present,the catalysts used to prepare PET are basically antimony?Sb?catalysts,and Sb catalysts have good catalytic activity.But Sb is a heavy metal element,causing great pollution to the environment.Therefore,the use of a non-heavy metal catalyst is particularly important.At the same time,PET is easy to burn when it comes into contact with fire source,and it is easy to have fire hazards during use.Therefore,the flame retardancy of PET is also a focus of its research.The nanometer Zinc Borates?ZB?is made in this paper,and we explored the best synthesis of ZB.PET/ZB nanocomposites were prepared by in-situ polymerization.In this paper,we used the polycondensation reaction time,intrinsic viscosity,chroma,and melt index to compare the catalytic effects of the same content of ethylene glycol hydrazine with ZB,and the influence of different content of ZB on the polymerization.The thermal and mechanical properties of PET/ZB nanocomposites were studied by differential scanning calorimeter,thermogravimetric analyzer and universal testing machine.The flame retardancy of PET/ZB was studied by limiting oxygen index instrument,vertical combustion apparatus and Raman spectroscopy.Through the best synthetic process conditions:The molar ratio of raw material is n?Zn?NO₃?₂·6H₂O?:n?Na₂B₄O₇·10H₂O?=1:1,liquid-to-solid ratio is 1:1,PH value is 6.0⁶.5,stirring speed is 300rpm,the reaction temperature is 85,and the reaction time is 6h.A new type of zinc borate particles with chemical formula of 3ZnO·3B₂O₃·3.5H₂O?ZB3335?was prepared.The rod-like structure has a product diameter of about 100 nm and a length of about 250 nm.The nano ZB loses the crystallization water temperature around 370°C.ZB has higher catalytic activity than ethylene glycol antimony.When the content of ZB increased to 0.25 wt%,the condensation time was 1.5 h,the intrinsic viscosity was 0.606 dL/g,the MI value of the melting index was 46.235 g/10min,the transparency of the polyester decreased and the catalytic effect was obviously enhanced.When the content of ZB is not more than 0.25wt%,ZB is dispersed more evenly in PET matrix without agglomeration.When the amount of addition is 0.375 wt%,ZB has a general dispersion effect in PET,but it still presents a state of uniform dispersion on the whole.This indicates that nano ZB can be dispersed uniformly in PET matrix by in-situ polymerization process.With the increase of ZB content,tensile strength,Young's modulus and elongation at break also increased first and then decreased.When the addition amount is 0.25 wt%,PET/ZB composites have better tensile strength,young modulus and elongation at break.The addition of ZB has no obvious changes in the glass transition temperature?T_g?,melting temperature?T_m?and crystallization temperature(T_mc),and the thermal properties of the PET/ZB composites are in the range of suitable processing applications.The TGA test showed that the residual carbon content increased at 700?,indicating that the addition of ZB promoted the formation of carbon layer.The study on the flame retardancy of PET/ZB showed that the LOI value of PET and PET/ZB?0.03 wt%?,which was prepared by the same content of ethylene glycol antimony and ZB,increased from 22%to 24.8%,indicating that the flame retardancy of ZB was higher than that of ethylene glycol antimony.With the increase of ZB content,the LOI value continues to increase.When the ZB content is 0.25 wt%,the LOI value reaches 25.7%,and the flame retardancy is improved obviously.