Preparation And Properties Of Recyclable Styrene-maleimide Copolymer Aerogels For Energy Conservation

Polystyrene maleic anhydride alternating copolymer is a commercial polymer that is very inexpensive and has highly reactive anhydride groups that can react with hydroxyl and amino groups to prepare new functionalized polymers,and the reaction with ammonia can prepare high temperature resistant styrene maleimide based copolymers.Polymer aerogels have many excellent properties,but the traditional sol-gel method requires up to 6-7 days of aging and cross-linking.It is well known that the lower the density of a polymer product,the higher the cost of transport for recycling.Polymer aerogels with very low densities are more difficult to recycle than conventional plastics,and cross-linked or hydrophobically treated polymer aerogels are even more difficult to recycle.As consumption increases,polymer aerogels will certainly cause more’white pollution’ than conventional plastics in the future.No research has yet been carried out on polymer aerogels that can be recycled under mild conditions without the use of organic solvents,although this is extremely important for the sustainable development of polymer aerogels.In order to achieve the recycling of polymer aerogels under mild conditions without the use of organic solvents,a high temperature resistant styrene maleimide copolymer aerogel was developed using a low cost alternating maleic anhydride styrene copolymer in this work,which the aerogels can be recycled quickly at 95°C without agitation in the presence of ammonia.The aerogels are prepared and recycled without the use of organic solvents and are environmentally friendly.The main research elements and innovations in this paper are as follows:1.A new simple and environmentally friendly method for the preparation and recovery of hydrophobic and water-resistant SMI copolymer aerogels has been designed,which does not require the use of organic solvents during both the preparation and recycling process of the aerogels.The polymer aerogels can be consistently recycled with efficiencies more than 99%,and the recovery of the aerogels is a process of upcycling with increased glass transition and thermal decomposition temperatures as the degree of acylation increases.This method is not limited to aerogels,but is universal and can be used for the recovery of membranes and plastic materials,etc.We have also demonstrated that other alternating copolymers of maleic anhydride can be recovered under ammonia after acylation,which significantly broadens the potential and industrial value of the method.We have also tested the AIE performance of SMI for the first time and utilized it for composite material performance monitoring,including temperature monitoring of phase change materials(PCMs)and water absorption monitoring of dehumidified materials.We have also focused on the chemical reactions and structural changes involved in the preparation and recovery of aerogels,providing a detailed analysis of the recovery process.The porous structure of SMI aerogels gives them a low density of 19.2 kg/m3 and a thermal conductivity of0.0274 W/(m·K),and the glass transition temperature and thermal decomposition temperature of SMI are much higher than those of conventional polymeric foams,making them suitable for use as high temperature insulation.The glass transition temperature and thermal decomposition temperature of SMI are much higher than those of conventional polymeric foams.Through the conversion process of watersoluble polymers and non-water-soluble polymers,we propose a new green recycling method for polymers.2.The SMI aerogel loaded dodecane shape-stable PCMs for cold storage have AIE photoluminescence properties,so the PCMs can be used for real-time temperature monitoring by fluorescence intensity,which can be used for food preservation and cold chain transportation,including vaccines.The SMI/r GO composite aerogel was obtained by thermal reduction and microwave reduction of graphene oxide,which was used for loading paraffin wax to prepare a shape-stable PCM for thermal storage with photothermal conversion,which can be heated to over 70°C within 30 min and can be used for thermal storage and solar energy as well as environmental temperature regulation.The introduction of r GO improved the thermal conductivity of the phase change composite(PCC)by 26.6%,significantly improved the compressive properties of the PCMs and enabled the PCCs to have a photothermal conversion function.In addition,both phase change composites can be recycled by re-dissolving them in ammonia at 95°C after being discarded.The recyclable aerogel particles for dehumidification were prepared using a one-step process to exploit the recyclability of the SMI aerogel backbone.The hydrophobic SMI aerogel was loaded with water-soluble Li Cl as a skeleton in the aerogel particles.24 h water absorption of HSMIA at 80% relative humidity(RH)was as high as 3.965 g/g.HSMIA aerogel can effectively reduce the in confined spaces,such as air dehumidification in confined spaces,and this aerogel material dehumidifies extremely fast,and the water absorption is 30.5 and 14.4 times higher than that of commercial desiccants silica gel and 4A molecular sieve.30.5 and 14.4times the water absorption of commercial desiccants silica gel and 4A molecular sieve.The aerogel can simply be regenerated repeatedly in an oven with little change in the kinetic curve of the regeneration process and the moisture absorption capacity remains relatively constant.After the hygroscopic aerogel has been completely discarded beyond its service life,it can be quickly and completely converted to an aqueous solution at 95°C for 30 min without stirring and can be used directly for the next cycle of hygroscopic aerogel production.In order to reduce costs,we have also developed KCOOH-based hygroscopic aerogels,which are extremely low cost(only 2% of Li Cl)and still have a good hygroscopic capacity.In order to improve the flame retardancy of SMI aerogels,a new lowcost environmentally friendly halogen-free intrinsic flame retardant,MEAPP,was successfully synthesised by ion-exchange reaction of aqueous solutions of SAPP and MEA.MEAPP loading enables the aerogel to be self-extinguishing off fire and significantly reduces heat release in microcalorimetric tests.In order to broaden the scope of application of MEAPP flame retardants,flame retardant RPUF composites were prepared and the MEAPP/EG flame retardant system developed has excellent synergistic flame retardant effects.With the addition of only 5% MEAPP and 10% EG,the LOI value increased to 31.9% and passed the UL-94 V-0test,with rapid self-extinguishing within 0.3 s.Compared to pure RPUF,both PHRR,THR and SPR were significantly reduced.Since MEAPP is an intrinsic flame retardant and acts as a cross-linking agent in addition to the flame retardant,the compressive strength of RPUF increased by 39% after adding only 5wt% of MEAPP.The prepared flame retardant RPUF material has a long-lasting flame retardant effect,an excellent flame retardant and thermal insulation effect and excellent overall performance.