Study Of Toughened And Flame Retarded Poly(Ethylene Terephthalate) Engineering Plastics

Polyethylene terephthalate (PET) has excellent properties, such as high strength, insulation, heat resistance and chemical resistance, etc. PET has been used as engineering plastic which is an interesting research topic. It's significant to convert the large amounts of PET recycled from municipal wastes to high-performance engineering plastics.Serval scientific and technical topics need to be settled when PET used as engineering plastics. First, the toughness of PET must be improved and its rigidity(tensile yield stress, flexural modulus) must be preserved or decreased little,keep strength and toughness at the same time. Second, to accelerate crystallization rate and decrease cool crystalline temperature, so the product can be mold at lower die temperature. Third, add reinforcing material such as glass fibres to further improve the strength of PET. Forth,select suiTab. ?ame retardant to resolve ?ame retardancy of the materials. At home and abroad, the research works about PET have gotten much positive results, but there are still some scientific and technical problems. For example, when elastomers are used to toughen PET, toughness of the blends can be improved highly but its strength deteriorated largely without expectation, too. Adding nucleating agents and nucleation accelerant to PET blends can improve the crystallization property, but the toughness of PET was decreased. The most serious problem is that these additives are easy to pyrolysis during processing.The inomer had been used to modify PET in this paper. The effects of Surlyn on crystallization of PET were investigated by DSC. Results showed that Surlyn significantly speed up the crystallization rate of PET. Toughening of PET was carried out by blending it with Surlyn, a maleic anhydride grafted polyethylene-octene elastomer (POE-g-MA) and ethylene-butylacrylate-glycidyl methacrylate (PTW). The mechanical properties, flow properties heat resistance and impact fracture surface morphology of the PET/ toughening modifier blends were discussed. The blend morphology was observed by scanning electron microscopy. The results showed that the Surlyn ionomer has strengthening and toughening effect on PET. PET has good comprehensive properties when its content was 10%. In this case, impact strength and tensile strength of PET increased by 66.8% and 6.6% respectively, heat resistance were improved. POE-MAH and PTW also increased toughness of PET but they decreased strength significantly.The effects of glass fiber content on the properties of PET were studied on the basis of 10% Surlyn. The results showed that mechanical properties and heat resistance increased with the increase of GF content. 30% GF reinforced PET/Surlyn composite had the best overall performance.During processing at high temperatures, thermal and/or hydrolytic processes can occur, which decrease the molecular weight of PET. High reactivity of epoxy resin make it possible to be used to improve the properties of PET. A difunctional epoxy resin named NPES907 were added to reinforced PET composite, through reaction between the epoxy group and the carboxyl or hydroxyl group of recycled PET, the interfacial strength were enhanced, the viscosity were increased, mechanical strength and heat resistance were improved, the modified effect was the best with 1% NPES907.Brominated Polystyrene and antimony trioxide were used as flame retardant to improve the flame retardancy of PET, when total addition is 11% the composite can reach the UL94-V0 flame retardant grades. Use flame retardant anti-dripping melt additives together with flame retardant can improve the fire resistance of melt drip and reduce content of flame retardant. The optimal amount of flame retardant and anti-dripping melt additives are 10% and 0.5% respectively. The flame retardant toughed PET engineering plastic prepared has good mechanical properties, rheological behavior, heat resistant and flame retardance.Layered silicates nano-clay have special layered structure, the strength and modulus of polymer can be increased by adding just a small fraction of clay to a polymer matrix, and nanometer sized clay platelets are effective nucleating agents. Based on study above, montmorillonite, kaolinite and halloysite nano-carbon nanotubes were used to modify the PET/Surlyn blends. The results showed that nano-clay as a heterogeneous nucleating agent speed up the crystallization rate of PET, uniformly dispersed nano-clay can improved the tensile strength, rigidity, flowability and heat resistance at low content. The impact strength of material decreased with the increasing of nano-clay. The modifying effect was the best with 3% nano-clay.It is proved through experiments, that PET composite has the best synthetic when the addition of the ionomer was 10%, that of glass fiber was 30%, flame retardant and anti-drip agent were 10% and 0.5% respectively, the optimum content of nano-clay was about 1%. The over-all properties of composite had closed to the levels of Rynite530 of Dupont Company. It can be applied in electronic and electrical equipment.