Preparing And Properties Of Insulting Thermal Conductive PET Composites

Industry demand and technology development put forward higher requirement for thermal conductive materials. In addition to thermal conductivity, it also requires the materials to be less costly, lighter, be easy to process, possess good mechanical properties and electronic insulation. This paper looked at how to prepare insulating thermal conductive composites with polyethylene terephthalate ?PET? as the matrix and Al₂O₃ as the filler. The research also reviewed the impact of Al₂O₃ content and particle size on the mechanical properties and thermal conductivity of PET/Al₂O₃ insulating thermal conductive composites. As the Al₂O₃ content increased, the thermal conductivity became higher while the mechanical properties degraded; when Al₂O₃ content was fixed, the bigger the Al₂O₃ particles size, the higher the thermal conductivity, and the worse the mechanical properties. When Al₂O₃ content reached 70 wt%, the thermal conductivity of PET/Al₂O₃ insulating thermal conductive composites would be 1.102 W/?m K?, higher than that of pure PET by 4.89 times; the tensile strength, flexural strength, impact strength and the volume resistance would reached 29.22 MPa, 55.74 MPa, 1.66 kJ/m2, 3.2×1015 ?·cm ,respectively.To improve the mechanical properties of the insulating thermal conductive composites, in this paper, after silane coupling agents ?KH-550?containing amino groups reacting with Al₂O₃, we added respectively the equimolar amount of 1,4-butanediol diglycidyl ether and 1,6-hexane dioldiglycidyl ether to prepare two types of functionalized Al₂O₃ with epoxy groups. The epoxy groups over Al₂O₃ could react with carboxyl groups of the PET matrix, not only increasing capacity but also extending the chain. The SEM image showed that functionalized Al₂O₃ can improve the dispersion of Al₂O₃ particles in PET matrix; the mechanical properties and the thermal conductivity of composites modified by functionalized Al₂O₃ were superior to those unmodified and modified by three coupling agents. When functionalized Al₂O₃ prepared with KH-550 and HDE, the thermal conductivity of the insulating thermal conductive composites was higher. When Al₂O₃ content reached 70 wt%, the thermal conductivity, the tensile strength, the flexural strength and the impact strength were 1.262 W/?m K?, 38.31 MPa, 67.82 MPa and 2.62 kJ/m2,respectively.When Al₂O₃ content reached 70 wt%, the fluidity of the composites got worse.Considering the thermal conductivity, the mechanical properties and the processing of the insulating thermal conductive composites, Al₂O₃ content was below 60 wt%.While at that time, the thermal conductivity was lower. This paper involved mixture of different size Al₂O₃ to improve the thermal conductivity, when the ratio of 4 ?m Al₂O₃ to 20 ?m Al₂O₃ was 8:2, the overall performance of the composites got better.To improve the thermal conductivity of the composites, the above mentioned optimum Al₂O₃ mixture could mix respectively with fillers with high thermal conductivity, SiC?AIN and BN. This would also allow for more consideration on the categories of the high thermal conductivity fillers and ratio of Al₂O₃ to high thermal conductivity fillers on the impact to properties of the insulating thermal conductive composites.