Flame Retardant System Design And Cross-linking Modification Study Of PMMA Transparent Cast Board

Polymethyl methacrylate(PMMA),with excellent transparency,low production cost,easy mechanical processing,which is widely used in the field of advertising,signs,transportation,and construction,and etc.Nevertheless,PMMA is a flammable material(LOI value is 17.3%),and will release intense heat and cause dripping when being ignited.Therefore,it is essential to improve its flame retardant property when it is used in some easy to contact fire sources or special applications.High light transmittance is the most prominent advantage of PMMA,which is often used in special fields such as precision instrument panels,aircraft cockpits,and medical equipment.Under normal temperature conditions,most phosphate esters are colorless and transparent liquids,which have good compatibility with MMA monomers.However,phosphate ester flame retardants also have some problems in PMMA,such as low flame retardant efficiency and large addition.At the same time,the material's thermal stability,mechanical properties and light transmittance are affected.Therefore,the flame retardant PMMA obtained from this technical route has no actual market application value.This subject takes the above background as the research direction,and solves the above problems from two aspects.First,through the synergy between flame retardants,design a flame retardant system suitable for PMMA transparent cast board.Second,through physical and chemical cross-linking,the physical properties and heat resistance of the composites are improved from the perspective of stiffening and strengthening.The main research contents include:(1)The flame retardant system was compounded by Tris(2,3-dichloropropyl)phosphate(TDCPP)and polyphosphoric acid and used as flame retardant in PMMA.The study found that as the proportion of PPA,the flame retardant performance and thermal stability of the composites are improved.The LOI of flame retarded PMMA can reached 27.1% and UL-94 V-0 rating can be achieved at 18 wt %(TDCPP15wt%,PPA3wt%)loading.The gaseous products were analyzed through TG-FTIR,the composition of char was characterized by FTIR.Then the degradation route and flame-retardant mechanism of flame retardant were speculated.(2)Use dimethyl methylphosphonate(DMMP)as a halogen-free flame retardant for PMMA.At 25wt% and 30wt% loading of DMMP,the LOI of flame retarded PMMA could reach 24.6% and 26.2%,respectively,and UL-94 V-0 rating could be achieved.The gaseous products of the composites during the decomposition process were analyzed by TG-FTIR,the char structure and composition of the composites at different temperatures were characterized by FTIR,and speculate the flame retardant mechanism of flame retardant DMMP in PMMA.The research results showed that DMMP is mainly gas-phase flame retardant in PMMA.The composites of has excellent flame retardant properties at 25wt% DMMP loading,but its physical properties and thermal stability are significantly lower than pure PMMA.(3)Ethylene glycol dimethacrylate(EGDMA),triallyl isocyanurate(TAIC),and allyl methacrylate(AMA)are used as chemical crosslinking agents for PMMA.The linear PMMA macromolecules long chains are cross-linked into a "three-dimensional network",which improves the physical properties and thermal stability of the composites.Among the three crosslinking agents,EGDMA has the best effect.The Vicat softening point temperature of the modified flame retardant material is increased from 26.4 ? to 50.6 ? at 6wt% EGDMA loading,and physical properties of the composites has significantly improved.(4)Use methacrylic acid(MAA),acrylic acid(AA),and methacrylamide(MAAM)as physical crosslinking agents.MAA,AA,MAAM molecules form hydrogen bonds with-C=O groups in PMMA long chain or the same kind of molecules to improve the thermal stability of composites.Among the three physical crosslinking agents,MAA has the best effect.The Vicat softening point temperature of the modified flame-retardant composites was increased to 60.7?at 6wt% MAA loading,and it has excellent light transmittance and physical properties,meet the production and use standards.