Preparation And Properties Of Oil Basis Crosslinked Reversible Non-isocyanate Polyurethane

Non-isocyanate polyurethane(NIPU)prepared from cyclic carbonate and polyamines is a new type of polyurethane,which is insensitive to the water in the surrounding environment,has high chemical resistance and thermal stability,low permeability and water absorption,and is a research hotspot in recent years.However,there are some technical problems in this method,such as excessive use of petroleumbased raw materials,necessary use of organic solvents,high reaction activation energy,poor chemical resistance,difficult reprocessing and recovery and so on.The introduction of dynamic bond exchange reaction which can carry out reversible cross-linking into NIPU can prolong the service life of NIPU and solve the above problems.In view of this,the oil-based reversible crosslinking NIPU,was prepared by using oil-based cyclic carbonate as raw material and three different amines as cross-linking agents,which not only solved the above problems,but also studied the regulation of amino cross-linking agents on the structure and properties of NIPU.The main results are as follows:(1)Carbonated soybean(CSBO),was prepared from epoxy soybean oil(ESBO)and CO2,and then the bio-based p-menthane-1,8-diamine(MDA)was used as the crosslinking agent to cure CSBO,and the whole biological CSBO-MDA was obtained.The analysis shows that CSBO-MDA has good thermal stability and good solvent resistance.Through dynamic thermo-mechanical analysis and stress relaxation test,it is confirmed that the prepared NIPUs is homogeneous and reversible cross-linking reaction can be carried out at or above 140 °C.Through experiments,it is proved that reversible crosslinked CSBO-MDA has the characteristics of welding,physical cycle reprocessing,chemical recycling processing and shape memory.(2)4,4'-methylenedianiline(DDM)containing two amino groups and two benzene rings was used as cross-linking agent to cure CSBO-DDM with CSBO at 140 °C.The results show that CSBO-DDM has high thermal stability,the decomposition temperature of 10% of its weight loss is above 300 °C,and has good solvent resistance.NIPUs can realize reversible cross-linking of network structure by dynamic bond exchange at140 °C and above.It is proved by experiments that reversible cross-linked CSBO-DDM has the characteristics of self-healing,physical cycle reprocessing,chemical recycling processing and shape memory.(3)Double reversible cross-linked CSBO-DTDA,was prepared by curing 4,4'-diaminodiphenyldisulfide(DTDA)and CSBO containing two amino groups,two benzene rings and disulfide bonds at 140 °C and compared with single-disulfide reversible crosslinked ESBO-DTDA and single-carbamate reversible crosslinked CSBO-DDM as mono-reversible crosslinked NIPU.Through dynamic thermomechanical analysis and stress relaxation test,it is confirmed that all the prepared NIPUs can realize reversible cross-linking by dynamic bond exchange,and CSBO-DTDA has faster stress relaxation under the same conditions.Furthermore,double reversible crosslinked CSBO-DTDA has faster self-healing properties and better reprocessing properties.