| Polybutylene terephthalate（PBT）possesses excellent comprehensive properties and is widespreadly used in automotive household appliances,electronic appliances and other industries,but its application is limited due to its flammability and high insulation to generate static electricity easily.In this paper,flame retardant and antistatic PBT/PP composites were prepared using PBT and polypropylene（PP）blends as matrix resins,diethyl aluminum hypophosphite（AlPi）and melamine polyphosphate（MPP）as compound flame retardants,iron/cobalt metallic organic frameworks（Fe/Co-MOFs）as synergistic flame retardant,graphene nanosheets（GNPs）as antistatic agent,ethylene-glycidyl methacrylate-methyl acrylate terpolymer（BF-7M）and nitrile rubber grafted glycidyl methacrylate-styrene copolymer（NBR-g-（GMA-co-St））self-made as a toughening and compatibilizer.The mechanical properties,flame retardancy,antistatic properties and thermal stability of the composites were investigated.The main conclusions are as follows:（1）The compatibilization and toughening effect of NBR-g-（GMA-co-St）in PBT/PP composites were investigated.For PBT/PP blends,with the increase of PP content,the tensile strength of the blends decreases and the melt flow rate increases.When the proportion of PP is higher,the oil resistance of the blends decreases.The addition of St with the same mass ratio as GMA in the grafting process of NBR can effectively improve the degree of grafting and reduce the degree of crosslinking;When adding 10%St and 10%GMA,the relative grafting degree of NBR-g-（GMA-co-St）is increased to 1.16,which is twice that of NBR-g-GMA with only adding 10%GMA;Moreover,reducing the amount of dicumyl peroxide（DCP）can reduce the degree of crosslinking.In PBT/PP composites,NBR-g-（GMA-co-St）makes the glass transition of PBT move to the low temperature direction,decreases the size of PP dispersed phase particles,and improves the compatibility of composites.NBR-g-（GMA-co-St）has a toughening effect on composites.When the content of NBR-g-（GMA-co-St）is 16.7%,the impact strength of PBT/PP composites rises to 15.47 k J·m-2.In addition,NBR-g-（GMA-co-St）can reduce the thermal stability and crystalline properties of the composites.（2）The flame retardant effects of AlPi,AlPi/MPP and AlPi/MPP/Fe/Co-MOFs retardant systems applied to two-phase PBT/PP composites were studied.A small amount of deionized water and triethylamine（TEA）make Fe/Co-MOFs more likely to be lamellar.Fe/Co-MOFs has a strong catalytic effect,which can promote the catalytic charring effect of AlPi and MPP.The optimal ratio of PBT/PP/AlPi/MPP/Fe/Co-MOFs is 70/30/13.0/6.5/0.6.The oxygen index of the composites in this ratio is 32%,the UL-94 vertical combustion grade is V-0,the carbon residue rate is 8.97%.The compound flame retardant reduces the mechanical properties and thermal stability of the composites.When 16.7%compound flame retardant is added,the tensile strength of the composites drops to 25.76 MPa,the impact strength drops to 2.8 k J·m-2,and the initial decomposition temperature decreases to 368.9℃.The compound flame retardant plays the role of heterogeneous nucleation in the composites,which increases the crystallization temperature of the composites.After adding toughening agent to increase the toughness of flame retardant PBT/PP composites,the thermal stability of the flame retardant material is improved,and the vertical combustion grade remains unchanged.The toughening effect of BF-7M is better than that of NBR-g-（GMA-co-St）,but the addition of the toughener reduces the oxygen index of the composites.（3）The effects of carbon fiber（CF）,conductive carbon black（CB）and GNPs on the antistatic properties of PBT/PP blends were compared and investigated,and GNPs was added to flame retardant PBT/PP composites to study the antistatic properties.For PBT/PP blends,CF needs to be added at a larger amount（>11.5%）to achieve the antistatic effect,and at a larger addition,CF has an enhanced effect;When the addition of CB and GNPs is 6.5%,the volume resistivity of the composites reaches the order of magnitude of 106,and the surface resistivity reaches 107.CB and GNPs also have the same enhanced effect at a lower addition;The toughening agent has little effect on the antistatic properties of PBT/PP composites.When the compound flame retardant is added to the antistatic PBT/PP composites,the antistatic properties of the composites is basically unchanged and remains within an order of magnitude.GNPs and compound flame retardants have synergistic flame retardant effect.When adding 3%GNPs to flame retardant PBT/PP composites,the vertical combustion grade of the composites has no effect,still maintains V-0 grade,and oxygen index increases slightly to 33%,then continued to increase the amount of GNPs,and the oxygen index of the composites decreases.The addition of GNPs reduces the initial decomposition temperature of the composites to 365.6℃,but is conducive to the formation of carbon residue,and the carbon residue rate increases to 13.90%.The addition of BF-7M improved the thermal stability of the flame retardant and antistatic PBT/PP composites,and the initial decomposition temperature increases to 369.5℃.After the flame retardant and antistatic PBT/PP composites are soaked in gasoline,the tensile strength of the composites decreases,the vertical combustion grade drops to V-1,the oxygen index drops to 23%,and the surface resistivity and volume resistivity increase to 109 orders of magnitude,but the antistatic effect still can maintain.Compared the flame retardant and antistatic PBT/PP composites prepared by the one-step method and the two-step method,the composites prepared by the two-step method have better mechanical properties,flame retardant properties and antistatic properties. |
