Flame Retardant And Waterproof Modification Of Thermoplastic Polyolefin

Thermoplastic polyolefin（TPO）waterproofing membrane is widely used in the construction waterproofing.However,TPO is extremely easy to be burned,once the TPO waterproofing membrane laid on the roof of the building is ignited,it will trigger the overall building fire.It has become a serious threat to the safety of people’s lives and property,so it is very urgent to modified the TPO with flame retardant.Intumescent flame retardants（IFR）are highly efficient and environmentally friendly flame retardants.However,due to the molecules of IFR contain hydrophilic groups,when applied in TPO for outdoor areas,it will cause the water absorption of TPO waterproofing membranes become larger.The precipitation and loss of flame retardant under the rain shortens the safe service life of TPO waterproofing membrane.Therefore,it is necessary to improve the water resistance of flame retardant TPO composites.In this paper,piperazine pyrophosphate（PAPP）and melamine phosphate（MPP）were selected to form IFR and applied in TPO.The water resistance of flame retardant TPO composites was improved by adding bulking agents and using different ways to coat IFR.The main research is:1 The water resistance of flame retardant TPO composites was improved by using maleic anhydride grafted polyethylene wax（MA-PEW）as bulking agent.MA-PEW had both polar and non-polar ends,the polar end-MA could react with the polar group in IFR molecule,and the non-polar end-PEW had great compatibility with TPO molecular chain.MA-PEW could be added directly into the flame retardant TPO composites as a processing additive with easy and convenient operation.The obtained samples were soaked in deionized water at 70°C for 168h.Compared to TPO/20%IFR,the water absorption of TPO/20%IFR/3%MA-PEW decreased from 5.88%to 4.84%.The UL-94 test for TPO/20%IFR（sample thickness is 3.2mm）achieved V-0 rating before water soaking,but after water soaking it was NR rating.TPO/20%IFR/3%MA-PEW maintained UL-94 V-0 rating before and after water soaking,showed good water resistance.2 The improvement of water resistance of flame retardant TPO composites by IFR coated with modified PP was studied.PP was modified to obtain maleic anhydride grafted polypropylene（MAPP）and multi-branched polypropylene（MCB-MAPP）.The polar groups in the modified PP reacted with the polar groups in the IFR to achieved the coating of IFR,and the unreacted non-polar groups lied on the outer side to acted as a hydrophobic protective layer.The water resistance and flame retardant demands were improved,the UL-94 test was conducted using 1.6 mm thick samples,and the addition of IFR was 22%.Compared to the NR rating for TPO/IFR in UL-94 test,TPO/MAPP@IFR and TPO/MCB-MAPP@IFR were upgraded to UL-94 V-0 rating,UL-94 V-2 rating was achieved after water soaking.The water absorption of TPO/IFR was 6.03%,the water absorption of TPO/MAPP@IFR was 4.66%,with 23%reduction,the water absorption of TPO/MCB-MAPP@IFR was 4.02%,with 33%reduction.TPO/MCB-MAPP@IFR showed better water resistance.3 The improvement of water resistance of flame retardant TPO composites by IFR uniform coated with silicone resin was studied.The silicone resinγ-DHPP was synthesized,Zn²⁺andγ-DHPP were used to improve the flame retardant efficiency of IFR.The outer layer of IFR was loaded with zinc ions complex(Zn²⁺-BCT),and then KH550 reacted with Zn²⁺-BCT to guide the silicone resinγ-DHPP to uniformly coat the surface of IFR,thus to improve the water resistance of IFR.The test results for TPO/22%Si-Zn@IFR compared with TPO/22%IFR,the water absorption decreased from 6.03%to 3.91%,the tensile strength increased from 12.5MPa to 18.0 MPa,the elongation at break increased from 538%to 842%,and the V-0 rating could be maintained for UL-94 test（1.6 mm）before and after water soaking.It indicated the excellent comprehensive properties of TPO/22%Si-Zn@IFR.