Toughening Modification Study Of Flame-retarding And Reinforced Poly (1,4-butylene Terephthalate)

Poly(1,4-butylene terephthalate)，shorted as PBT，due to its excellent properties,has been widely applied in lots of fields like automobile parts, industrial machineryand equipment, household electrical appliances, electronic and electrical, preciseinstrument since it was invented. However, when it comes to the mechanicalproperties of pure PBT, the main drawback is its low notched impact strength, whichseriously limited the applications because of the large shrinkage-rate of injectionmolding products and severe warping phenomenon. So it is of great significance toreinforce and modify PBT in practical applications. Currently, the glass fibermodified PBT occupied more than seventy percentage of the total PBT products.Adding glass fiber into PBT enhanced the notched impact strength and mitigated thewarping phenomenon while reducing some properties like melt flow index, breakingelongation and other mechanical properties. In the aspect of combustion performanceof pure PBT，as one of the extremely flammable engineering plastics, pure PBTreleased heavy smoke and dropped terribly during combustion. Glass fiber isnonflammable, so the addition of glass fiber into pure PBT depressed the droppingphenomenon to some extent. However, the fire retardant in reinforced PBTdecreased its mechanical properties, which failed to meet the need of highercomprehensive performance fields and limited the industrial applications of PBT. Itis necessary to modify the reinforced PBT to synthesize high-performanceflame-retardant and reinforced PBT.In this paper, we synthesized the acrylic ester and methacrylic acid glycidylester bi-functional vinyl elastomeric toughening agents KT-22, KT-27, respectively;and studied the toughening modification of reinforced PBT and flame-retardant andreinforced PBT. Besides, we compared the reinforced performance of AX-8900, theimported toughening agent of the same type. During the toughening modification ofreinforced PBT study，we discussed what impact toughening agent dosage imposed on the comprehensive performance of the compound materials and concluded thatthe optimal dosage of the as-synthesized toughening agents were five percent.Firstly, we discussed what impact the different dosages and pretreatment ofglass fiber imposed on the mechanical properties of PBT. By experimentalcomparison, when the content of glass fiber was controlled about thirty percent, theprocess-ability and mechanical properties of reinforced PBT were relativelybalanced. What’s more, the glass fiber treated with silane coupling agent KH-560further enhanced the reinforcement and process-ability, making the surface of theproducts smoother. Then, we chose five common and representative flame retardantsto modify the synthesized reinforced PBT and discussed what impact different flameretardants imposed on the performance of reinforced PBT. The five flame retardantsare red phosphor masterbatch, decabromodiphenyl oxide (DBDPO), brominatedepoxy resin (BER), bromated polystyrene (BPS), poly(pentabromobenzylacrylate)(PBBPA）, respectively. In order to increase the flame retarding performance,we mixed bromated flame retardants with Sb2O3in the proportion of2.5:1.The dosages of the five flame retardants above were the minimum dosages tomake synthesized reinforced PBT reach the UL-94V-0level, which alleviated theimpact of flame retardants on the mechanical properties to the maximum extent. Thetests showed that when the adding mass ratio of PBT/GF/PBBPA/Sb2O3was set as56/30/10/4, the products maintained the flame retarding performance of UL-94V-0level, the notched impact strength of products reached8.73KJ/m2, decreasingthirteen percent compared with glass fiber reinforced PBT and the descending rangewas the smallest. While we tested the phosphor masterbatch flame retardingmodified glass fiber reinforced PBT, the notched impact strength of productsremained5.0KJ/m2and the descending range exceeded one hundred percent.Besides, adding the five flame retardants made other mechanical properties decreaseto some extent as well.On the basis of ensuring the UL-94V-0flame-retardant level of the synthesizedreinforced PBT, we separately mixed the synthesized toughening agents KT-22,KT-27, the imported toughening agents AX-8900into every flame retarding systemby blending method. We made toughening modification toward these systems to get better comprehensive performance and compared the properties after modification.The tests showed that when the adding mass ratio of PBT/GF/PBBPA/Sb2O3/KT-27was set as51/30/10/4/5, the products maintained the flame retarding performance ofUL-94V-0level, the notched impact strength of products reached11.00KJ/m2,increasing20percent, the tensile strength reached100.91MPa, the breakingelongation reached the1.67%and the tensile strength reached172.9MPa. Everysystem adding5%synthesized toughening agents KT-27displayed relatively averagemechanical properties, and maintained the original flame retarding performance andprocess-ability. Obviously, the comprehensive performance of harmless andenvironment-friendly synthesized systems surpasses the AX-8900, and has a brilliantfuture in the market.