Preparation Of Multi-functional Flame-retardant Composite Materials Via Surface Modification

Globally,flame-retardants played a key role in preventing fire accidents.According to research statistics,the global consumption of flame retardants tends to increase,and is expected to hit 5.2 billion lbs in 2018.Speedy economic development and the increasing awareness of having flame retardants for prevention contribute to the huge flame-retardant consumption,but the low efficiency of flame-retardants is the key in this issue.Though the flame retardants are supplied everywhere,the function of flame retardants is not diverse,which can not meet the requirement of the changeable society.As the society has made big progress,multi-functional flame-retardant products are increasingly demanded.For the flame-retardant composite material attained through surface modification,wash-durability involves resource recycle,environment protection,and human safety.Also,wash-durability is the key of being commercial for a product.Organic flame retardants are commonly used to achieve wash-durable flame-retardant composite material attained via surface modification,but organic flame retardants are extremtly costly.Though inorganic flame retardants are widely used in many areas,it is very difficult to achieve wash-durability,weather-durability and recycling for flame retardant composite materials via surface modification by inorganic flame retardants,which leads to source waste.This dissertation mainly focuses on 3 purposes.First,look for some combinations with high flame-retardant efficiency,and provide an insight of low flame-retardant efficiency situation.Second,utilize different surface modification techniques to prepare multi-functional flame-retardant coatings,and apply the coatings to surface-modify some flammable substrates,including foam,fabric,and film,etc.,to impart flame retardancy-based superhydrophobicity,wash-durability or gas barrier properties.Try to broaden the applica area and increase the commercial product value for flame-retardant composite materials.Third,use inorganic flame-retardants to prepare wash-durable flame-retardant composites.The detailed researches are as follows.In the first part,novel intumescent flame-retardant coatings,consisting of montmorillonite(MMT)nanosheets and poly(acrylic acid)(PAA)and ammonium dihydrogen phosphate(ADP),were prepared via single step self-assembly and applied in flexible polyurethane(PU)foam to improve flame retardance.ADP and PAA could interact with MMT to form composite nano platelets,which could be transformed to thicker char to protect PU.The surface-modified PU with higher levels of MMT exhibited superior flame-retardancy and less shrinkage.Total heat release was reduced by over 45% with the coating of MMT and ADP alone.After 999 cycles of compression,the MMT/ADP sample displayed the weakest resilience and it was found that higher MMT content corresponded to greater loss of stiffness after 1000 cycles.In the second part,a series of coatings containing,consisting of sodium montmorillonite(MMT),ammonium polyphosphate(APP)and chitosan,were prepared via single step self-assembly and applied to PU foams.In the horizon flame test,MMT solely could protect the structure of whole foam,while APP or chitosan could not.The foam with MMT/APP and MMT/APP/Chitosan exhibit the best burning performance with least burning area.APP could protect PU via solid phrase and gas phrase.More importantly,APP exfoliated into MMT platelets,which was transformed into thicker thermal char to protect PU.According to the stress-strain compression test,the stiffness for the foams subjected to 70% strain is as follows: Chitosan>MMT/Chitosan>MMT/Chitosan/APP>MMT>MMT/APP>APP>Control.In the third part,intumescent flame retardant and hydrophobic coatings,consisting of sodium montmorillonite(MMT),ammonium dihydrogen phosphate(ADP),and methyltrimethoxysilane(MTMS),were prepared via in situ sol-gel and self-assembly techniques to acquire multifunctional cotton fabrics.A Si-O-Si network structure was generated via the hydrolysis-condensation reaction of MTMS,induced by the catalysis of ADP.Higer addition of MTMS could produce more hydrolysis-condensation products of MTMS and impart cotton fabrics with more hydrophobicity.After being treated by the coating with 2.0 wt.% of MTMS,the cotton fabric with a total uptake of 22.7 wt.% achieved appreciable flame retardancy and hydrophobicity,as well as satisfactory thermal stability and heat release behaviors.In the forth part,nanocoatings consisting of ammonium polyphosphate(APP),sodium montmorillonite(MMT),and vinyltrimethoxysilane(VTMS)were prepared via self-assembly and in situ sol-gel techniques and applied onto cotton fabrics to achieve both flame retardancy and hydrophobicity.More addition of APP generated higer degree of hydrolysis-condensation reaction,and thus enhanced hydrophobicity(~130.2°).APP and the hydrolysis-condensation product of VTMA could exfoliated into MMT platelets to form composite nano platelets,which could be transformed to thicker protective char when meeting fire or heat.So the treated cotton fabrics possessed excellent flame-retardancy(char length was 4.5 inches),thermal stability(only 40% weight loss)and heat release behavior(91.1% reduction).In the fifth part,wash-durable intumescent flame retardant and highly hydrophobic cotton fabrics were prepared via layer-by-layer(LbL)and UV curing.XRD pattern proves the interactions between ammonium polyphosphate(APP),montmorillonite(MMT)and UV curing polyurethane(UVPU).Furthermore,UVPU connected MMT and APP to make a network with extreme restricted motion after UV and heat curing.When this negative MMT/APP/UVPU layer was placed in-between of two positive branched polyethylenimine(bPEI)layers,motion would be completely restricted,which contributed to excellent wash-durability.The concentration of bPEI determined the final wash-durability of the coated fabrics,and those samples with 3% or 4% bPEI possessed remarkable wash-durability and hydrophobicity(~135°).For the samples coated 4 times,only the sample with 3% of bPEI,instead of the sample with 1%,2% or 4% of bPEI,survived in the vertical flme test,indicating that low concentration of bPEI contributed to bad wash-durability and correspongding flame-retardance loss,while high concentration of bPEI supplied more carbon source to composite material.In the sixth part,polysilsesquioxane co-condensation microspheres or nanospheres with methyl and vinyl functional groups were successfully prepared by emulsion approach.Wash-durable superhydrophobic and flame-retardant cotton fabrics were prepared through UV curing and Layer by Layer techniques with the combination of co-condensation spheres and PDMS.The main struction of of co-condensation spheres and PDMS is Si-O-Si network,the surface energy of which is extremely low.While,the co-condensation spheres were embeded onto the PDMS,enhancing the roughness.Thus,this combination chemically and physically supplied cotton fabrics superhydrophobicity.Though,the side chains of co-condensation spheres and PDMS were methyl and vinyl,which were flammable,the main struction,Si-O-Si,imparted cotton fabrics with remarkable thermal stability.wash-durable flame-retardant superhydrophobic cotton fabrics obtained in this alternative could highly maintained the flame-retardant and hydrophobicity performance.In the seventh part,co-assembly of montmorillonite(MMT)and polyvinyl acohol(PVA)were obtained with the help of ultrasonication,which were used to surface-modify PET films to achieve flame-retardancy and gas barrier properties.High oriention was achieved via the co-assembly of PVA and MMT for building hydrogen bond.More coatings onto the PET films,the better the flame-retardancy and thermal stability were.The high orientation films were transformed into swollen thermal barrier to protect PET film when exposed to fire or heat.What's more,the oxygen transmission rate(OTR)of the PET films was considerably reduced for the high orientation structure,while water vapor transmission rate(WVTR)did not decrease significantly.