Study On Flame Retardancy And Chain Extension Of Pet For Foaming

Polyethylene terephthalate(PET)is an important engineering plastic.Because of its flammability and lower melt strength,it is difficult to prepare flame retardant foam materials.In this paper,the flame retardant modification of PET was carried out by encapsulating red phosphorus(P),two aluminum hypophosphite(ADP)and polyphosphate flame retardant DH260 as flame retardants.The synergistic effect of chain extender PMDA and DH260,was studied to prepare flame retardant pet,with high melt strength.1.The effects of three kinds of flame retardants and their contents on the flame retardancy and rheological properties of PET were studied by means of limiting oxygen index instrument,horizontal vertical combustion tester and rotational rheometer.The results show that the amount of red phosphorus and ADP is greater than or equal to 5%,which can be tested by UL94V-O level.When DH260 content is greater than 10%,it can be tested by UL94V-o level.Among them,red phosphorus flame retardant PET has no droplet,ADP and DH260 all have droplet phenomenon.When red phosphorus and ADP content is 10%,the limit oxygen index can reach 36.7%and 34.5%,and DH260 reaches 32.2%at 15%content.It can meet the requirements of combustible materials.By comparison of rheological properties and the addition of three kinds of flame retardants,the viscosity of PET can be reduced by ADP and red phosphorus.When the content of DH260 is 10%,the viscosity of PET can be increased.The viscosity of PET can reach 1053.2Pa.S,which is 134 higher than that of pure material.2.The chain extender PMDA and flame retardants DH260 were used together.By changing the ratio of the two additives and controlling the drying conditions,the effect of DH260 on the chain modification of PET was studied.The results showed that the water absorption of DH260 was very strong.Before the experiment,it was necessary to ensure that the material was fully dried and dried at 95 degrees in a vacuum drying oven.The moisture content of DH260 should be lower than 500ppm before melting process.The addition of flame retardants will inhibit the chain extension of PET.Therefore,when adding flame retardants,it is necessary to increase the amount of chain extender PMDA to achieve the viscoelasticity of the melt required for foaming.When the flame retardant DH260 is added to 10%,the amount of chain extender should be increased by 50%.3.The flame retardant PET with high viscosity was analyzed by differential scanning calorimetry(DSC).The different foaming temperatures were used to carry out the intermittent foaming experiment.The results showed that with the increase of PMDA content,the foaming temperature region of flame retardant PET could be effectively broadened with the increase of PMDA content.When the dosage of PMDA was 0.6%,the pressure was 10Mpa,and the foaming temperature was 240 C,the foaming rate could reach 37.3 times.