Preparation And Properties Of Polycarbonate-Derived Shape Memory Polyurethane

As one of the smart materials,shape memory polyurethane is one of the hotspots of international academic research today.It has many advantages and can be applied in many fields.In addition to the advantages of smart materials,it also has some unique advantages,such as large shape variables,adjustable shape memory speed,strong designable,etc.,which could ensure its application in many fields(aerospace,biomedicine,petroleum industry and so on).Therefore,its research shows that it is very necessary.A series of polycarbonate-based shape memory polyurethane elastomers were synthesized by one-step melting method using carbodiimide-modified MDI(L-MDI),Polycarbonate 1,6-hexanediol esterdiol(PCDL),ethylene glycol(EG),1,4-butanediol(BDO),1,6-hexalene glycol(HDO),1,4-cyclohexanedimethanol(CHDM)and trimethylolpropane(TMP).The effects of hard segment content,molecular weight of soft segment,and chain extender on the properties(degree of hydrogen bonding,thermal properties,mechanical properties,hardness,water absorption rate,shape memory properties,and so on)of the material were investigated by FT-IR,differential scanning calorimetry,hardness test,tensile strength test,water absorption test and shape memory test.The results showed that when the memory phase(L-MDI and CHDM)content is 20%and the soft segment phase(PCDL)molecular weight is 2000,the shape memory polyurethane elastomer has strong hydrogen bonding degree,great mechanical properties and shape memory properties,shows best performance and great potential in the field of biomedical,petroleum engineering and smart clothing.A series of shape memory polyurethane foams(SMPUF)were synthesized by L-MDI,CHDM,PCDL-2000,and water.The effects of the type and content of the foaming agent,the type and content of the catalyst,and the content of the foam stabilizer on foam performance were investigated by density testing,mechanical testing,differential scanning calorimetry,and shape memory performance testing.The results showed that when the foaming agent(H2O)is 1.5 g,trimethylamine and dibutyltin dilaurate is 0.8 g,silicone oil is 0.5 g,SMPUFs have highest shape recovery rate and shape fix rate,minimum time required for shape recovery,and highest mechanical performance.Based on the full-text work,the design rules of PCDL and CHDM as shape memory polyurethane raw materials with high shape memory performance are summarized here:(1)For the structural design of the memory phase,the hydrogen bonding force and cohesive energy intensity should be increased as much as possible to ensure its strong cross-linking degree;(2)For the composition design of the memory phase,the movement of the molecular chain inside the polyurethane should be coordinated to reduce the steric hindrance of the memory molecular chain;(3)For the structural design of the switching phase,the regularity of the molecular chain should be improved as much as possible,and the length should be paid attention to ensure its strong crystallization performance.