Bio-based Modified Magnesium-aluminum Hydrotalcite And Flame Retardant Polypropylene Properties

Polypropylene(PP),as one of the five general-purpose plastics,its relatively small density,easy processing,corrosion resistance and other characteristics,has been widely used in medicine,military and construction industries.However,because PP is highly flammable,it is often accompanied by a large number of combustible droplets,which often causes fire hazards in its application.Therefore,the development of highly effective flame retardants to improve the flame retardant properties of PP is of scientific significance and application value.Hydrotalcite,as one of the halogen-free environmental flame retardants,has the advantages of being non-toxic,smoke suppression,and inexpensive.However,due to the easy aggregation of hydrotalcite and its poor compatibility with polymer materials,its flame retardant efficiency in polymer matrix is reduced and the mechanical properties of polymer are severely damaged.The effective way to solve this problem is to introduce a guest with flame retardant properties to modify the hydrotalcite.Therefore,in this paper,different methods are used to introduce bio-based guest with good flame retardancy and compatibility to modify magnesium aluminum hydrotalcite,and the modified hydrotalcite is applied to PP flame retardant.The specific work is as follows:(1)Based on the good compatibility and flame retardant properties of biological base sodium alginate,the composite material SA@LDHs was fabricated via calcination-reconstruction manner with sodium alginate and magnesium aluminum hydrotalcite,and applied to PP.The results show that SA@LDHs was used as a filler in PP composites,its flame retardant and mechanical properties were better than that of LDHs-C.With 30 wt% loading,the PP/SA@LDHs achieved a LOI value of 30.9% and a UL-94 V-0 rating.Compared with Neat PP,the peak heat release rate(p HRR),total heat release(THR)and total smoke production(TSP)of PP/SA@LDHs decreased by 69.2%,42.8% and 32.2% respectively.(2)In order to achieve a better flame retardant effect,SA@LDHs with a higher load(30%)are still required,and the higher load would affect the mechanical properties of polypropylene,therefore,bio-based sodium lignosulfonate with better flame retardant performance was selected as the modifier.The composite material LDH-LS was fabricated via coprecipitation method with sodium lignosulphonate and magnesium aluminum hydrotalcite,and applied to PP.The results show that compared with LDH,LDH-LS has smaller particle size and better hydrophobicity.And this change makes LDH-LS in PP composites with good dispersion and compatibility,so that the mechanical properties of PP/LDH-LS are better than PP/LDH.With 20 wt% loading,PP/LDH-LS reached UL-94 V-0 rating and LOI was 29.4%.Compared with PP/LDH,the p HRR,THR and TSP of PP/LDH-LS decreased by 44.5%,14.2% and 30.0% respectively,indicating that LS modification can improve the flame retardancy and smoke suppression performance of hydrotalcite in PP.(3)In order to further improve the flame retardant performance of LDH-LS,a nickel-based catalyst is introduced to improve the flame retardant effect of the condensed phase of the composite material.The composite material LDH-LS@Ni(OH)2 was fabricated via in-situ deposition method with nickel hydroxide and LDH-LS,and applied to PP.The results show that adding 15 wt% LDH-LS@Ni(OH)2 into PP,PP/LDH-LS@Ni(OH)2 achieve a LOI value of 30.8% and UL 94 V-0 rating,while LDH-LS requires a higher amount of addition to achieve a similar effect.And Compared with PP/LDH,the p HRR,THR and TSP of PP/LDH-LS decreased by 8.2%,12.2% and 14.3% respectively.This shows that Ni(OH)2 modified LDH-LS can further improve its flame retardancy and smoke suppression performance in PP matrix.