Design,Synthesis And Properties Of Bio-based Thermosetting Resin-based Phase Change Materials

Improved energy efficiency and resource utilization are considered to be necessary for sustainable development.Organic phase change materials(PCMs)as an effective thermal energy storage tool have attracted great interest,but non-renewable ingredients,low stability and their unsafe nature largely restrict their sustainability.Herein,a series of bio-based benzoxazine-derived PCMs were developed,in which green preparation,efficient energy conversion,and safe utilization can be simultaneously achieved.This is the first time to use thermosetting resin as phase change material,which provides an idea for the design of new organic PCMs and broadens the application field of thermosetting resin.The main research contents are as follows:(1)A series of mono-benzoxazine PCMs with high yield and high atom economy were successfully synthesized by combining natural cardanol with amine sources including long-chain aliphatic amines,amino acids and amino acid methyl esters through Mannich condensation reaction.The resulting PCMs exhibited adjustable latent heat(48.78-147.02 J/g)by altering raw materials,which are close to their commercial unsustainable counterparts.Due to the designed structure,as-prepared PCMs also possessed more excellent properties of thermal stability(Td50% was increased by 65.1%)and flame retardancy(p HRR was reduced by 39.4%)compared with traditional ones.(2)Using renewable cardanol and three fatty diamines with different carbon chain lengths,three difunctional benzoxazine PCMs with high monomer ring closure rate and high purity were successfully synthesized.Compared with mono-benzoxazine PCMs,the latent heat of difunctional monomers is much higher,reaching a maximum of 162.8 J/g.At the same time,the melting range of the bifunctional PCMs is also reduced by half,and the degree of undercooling remains basically unchanged,or even slightly reduced.After 20 thermal cycles,the phase transition temperature and latent heat are almost unchanged.In addition,the thermal stability of the difunctional monomers is significantly improved,and the initial decomposition temperature is increased by ～50 °C.After triggering the safety vale,the p HRR of the monomers decreased significantly.(3)Using a two-step method,with guaiacol and vanillin,the flame retardant BDB-MC monomer was successfully synthesized,and the BDBMC monomer was compounded with PEG1000 to prepare the polymeric form-stable composite PCMs BDB-MC/PEG.Compared with pure PEG1000,BDB-MC/PEG can maintain good shape at melting temperature,and the latent heat value of 57% of pure PEG.In addition,the DOPO flame retardant group in the BDB-MC monomer and the cross-linked network after polymerization form a synergistic effect,which effectively improves the thermal stability and flame retardant performance of the composite,and makes the Char yield at 800 °C of BDB-MC/PEG increased,p HRR and THR were significantly decreased.