Preparation Of In-situ Synthesis Modified LDHs By Silane And Its Application In PP

In order to achieve high efficiency flame retardant and reduce the loss of mechanical properties of materials as much as possible,the preparation and application of LDHs-based PP flame retardant were studied by"in-situ synthesis modification"method by silane.In this paper,due to the agglomeration of LDHs particles,the dispersion and compatibility of LDHs in the non-polar PP material matrix are poor,and the mechanical properties of PP material will be reduced if a large number of LDHs particles are added.Silane in-situ synthetic modified Mg AL-LDHS was innovatively prepared by"Silane in situ synthetic modified method".The prepared LDHs and Sb₂O₃were combined to form a halogen-free synergistic composite flame retardant system.The effect of LDHs on the flame retardancy and mechanical properties of PP composites was investigated,and the flame retardant mechanism was preliminarily discussed.The main conclusions are as follows:(1)CPTMO was selected and determined as a suitable silane coupling agent.The optimum conditions for the formation of stable silane hydrolysate were investigated and determined as follows:25%ethanol aqueous solution,V_(CPTMO):V_(25%ETOH)=1:40,hydrolysis temperature is 70?,hydrolysis time is 120min and the pH value of the system is 10.(2)The optimum conditions for preparing?-LDHS samples by powder modification of CPTMO hydrolysate were as follows:3g-50ml of?-LDHS,time is120min,temperature is 70?.(3)Under the conditions of temperature 70?,pH 10,V_(CPTMO):V_{(25%Et OH)}=1:40,Mg²⁺:Al³⁺=3:1(molar ratio),the suitable concentration of Al³⁺for the preparation of?-LDHS samples by in-situ synthesis and modification of silane is 0.4 mol·L-1.(4)The effects of adding mass ratio of?,?and?-LDHS on the flame retardant properties of PP composites were investigated.The results show that the PP composites with?-LDHs have better flame retardant properties and significantly reduce the loss of mechanical properties of the composites.When the ratio of?-LDHS is 30%,the LOI value of the composite spline is 23.5%,and the vertical combustion of UL-94 is V-1grade.Compared with pure PP material,the tensile strength decreased by 15%and the bending strength decreased by 7.5%.(5)The flame retardant performance of halogen-free co-effect composite flame retardant LDHs-Sb₂O₃ on PP materials was investigated.The results show that the total amount of composite flame retardant is 30%,the mass ratio of?-LDHS and Sb₂O₃ is 9:1.?-LDHs_(90%)-Sb₂O_3(10%)-PP composite spline has better comprehensive properties,the LOI value of the spline reaches 26.8%,the vertical combustion of UL-94 reaches V-0grade,the tensile strength decreases by 11.2%,the bending strength decreases by 7.0%.(6)The activation index,oil absorption value,XRD,FE-SEM and thermogravimetric analysis of the samples showed that the?-LDHS samples had higher activation index and smaller oil absorption value;The lamellar morphology of?-LDHS samples was incomplete and showed fine granularity.?-LDHs_(90%)-Sb₂O_3(10%)-PP composite increased the carbon residue from 1.5%to 34%of pure PP material,and had a good flame retardant effect.The mechanism of silane modification and the synergistic flame retardant mechanism between?-LDHS and Sb₂O₃ were also discussed.