Studies On The Crystallization Of Flame Retardant Polyethylene Terephthalate (PET) Engineering Plastic And Formulation Optimization Principles

Effects of the viscosity of the resin, the type and content of nucleating agents and the nucleating promoters, the flame retardants, glass fiber on the crystallization behavior of PET have been investigated. Talc and polysuccinate (PBS) were chosen from thirteen nucleating agents and eight nucleating promoters respectively. The process formulation of enhanced flame retardant PET was determined. The fire performance of PET can reach up to V-0 with the tensile strength of 145MPa, flexural strength of 212MPa, the impact strength of 8.0 kJ/m2 and heat distortion temperature of 223℃, which can compete with similar foreign products.The effect of nucleating agents and nucleating promoters on the crystallization behavior has been studied by using differential scanning calorimetry (DSC), and morphology of PET was observed by polarized light microscopy (POM) and wide-angle X-ray diffraction (WAXS). The mechanisms of both nucleation and nucleating promotion were proposed.The results show that the crystallization temperature Tc of PET has been increased in varying degrees by the addition of various nucleating agents, the crystallization rate has been speeded up. Among them, talc powder has the best nucleating effect, which can increase the crystallization temperature by 12.54℃with 0.5%addition and the crystallization can be improved with the cooling rate reduction; non-isothermal crystallization kinetics equations also was used to confirm the effect of talc powder on the crystallization of PET. In addition, the function of talc, montmorillonite, rare earth compounds, import product (P250), sorbitol (BQ-88), hindered phenol phosphate salts (MD-NA-28), sodium benzoate, the nucleating mechanism were analyzed and discussed according to the mechanical properties and molecular structure.The nucleating promoters can reduce cold crystallization temperature Tcc by different degrees, the Tcc of PET which added with 3%of the mixture of PBS and polyethylene glycol (PEG-1500) with the mass ratio of 1:1 can be reduced by 17.5℃. PBS as a better nucleating promoter is due to its faster crystallization rate.Flame retardants and the synergistic flame retardant can also promote nucleation; however, the effect of glass fibre on the crystallization behavior of PET is minimal.The principle of enhanced flame retardant PET engineering plastic formulation has been discussed. The results show that the flame retardants can also be used as nucleating agents, the effects of nucleating agents and nucleating promoters on different enhanced flame retardant PET systems are not as significant as that on pure PET; the efficiency of additives in formulation should be considered.