Preparation And Properties Of Flame Retardant Transparent PMMA

Plexiglass(Chemical name is polymethylmethacrylate,English abbreviation is PMMA)has high transparency,good chemical stability,electrical insulation and excellent processing performance.It also has the advantages of light weight,crushing resistance and easy installation compared with ordinary glass and toughened glass.It has became an effective substitute for ordinary glass and toughened glass.However,PMMA has poor thermal stability and is very easy to burn.It would produce serious dripping phenomenon and cause secondary disasters in the process of burning in the air,which limits the application of PMMA in the field of high-rise buildings instead of tempered glass.In order to solve this problem,PMMA composites were prepared by bulk polymerization with methyl methacrylate(MMA)as polymerization monomer,triethyl phosphate(TEP)as toughening agent,octavinyl cage silsesquioxane(Ov POSS)and hexachlorocyclotriphosphaze-ne(HCCP).The effects of HCCP_x/Ov POSS_1%and Ov POSS_x/HCCP_10%compound systems on the thermal stability and flame retardancy of PMMA composites were discussed.HCCP-POSS was synthesized from HCCP and aminopropyl triethoxysilane(KH-550)by nucleophilic substitution/hydrolysis condensation two-step method.Its molecular structure was characterized by FT-IR,NMR,MS,XRD and TG.Then HCCP-POSS/PMMA composite was prepared by bulk polymerization.Research found that:1.The introduction of HCCP would significantly improve the thermal stability of PMMA composites,and its glass transition temperature(T_g)increased from 120?to 174?when HCCP_x/Ov POSS_1%composite system was used to modify PMMA.And the flame retardant grade of PMMA composites would reach UL94 V-1 when HCCP content reached 20%,PMMA composites not only had strong and tough properties,but also maintain a visible light transmittance of about 85%,with good transparency when HCCP content was 10%.The introduction of Ov POSS could improve the thermal stability of PMMA composites,increasing its T_g from 120?to 163?and LOI value,and significantly reducing the water absorption of HCCP_10%/PMMA composite when Ov POSS_x/HCCP_10%composites system was used to modify PMMA.The mechanical properties of PMMA composites were the best when the content of Ov POSS was 1%,and the visible light transmittance was maintained at about85%,with good transparency.2.The introduction of HCCP molecule into Ov POSS_1%/PMMA composite system or Ov POSS molecule into HCCP_10%/PMMA composite system had a rigid contribution to the PMMA molecular chain,and the N,P and Cl elements in HCCP molecule could also form a gradient with the Si element in Ov POSS molecule and the P element in TEP to delay the decomposition of PMMA.At the same time,Ov POSS could inhibit the compliance of strong polar chlorine substituents in HCCP molecules to the increase of PMMA molecular chain interaction,and inhibit the contribution of nucleophilic substitution reaction and thermal decomposition of HCCP and TEP.3.HCCP-POSS could be synthesized from KH-550 and HCCP by nucleophilic substitution/hydrolysis condensation two steps.It was a light yellow amorphous substance with high thermal stability,T_50%was as high as 828?,and the carbon residue rate was 48.5%.The introduction of 0.4%HCCP-POSS into PMMA could greatly improve the thermal stability,hardness and impact strength of PMMA,which had high research value.