Preparation Of Environment-friendly Polyurethane And Its Application In Sizing Agent For Carbon Fiber

Carbon fiber reinforced thermoplastic resin matrix composites(CFRTP)possess a variety of excellent properties,such as high strength,modulus,thermal conductivity,and stability.Not only does the CFRTP play a significant role in the aerospace,marine,military,etc.,but also in the civil industrial field of new materials.However,owing to the carbon fiber(CF)surface of the smooth and chemically inert,the interfacial adhesion and stress transfer efficiency between fiber and matrix were weak,which would affect seriously the mechanical performance of the composites.In this paper,two types of hyperbranched waterborne polyurethane sizing agents from the bio-materials were prepared to improve the poor interfacial adhesion of CF/polyamide-6(PA6)composites.The study contents of this paper are as follows:(1)According to the principle of “similar dissolve mutually”,a series of bio-based waterborne polyurethane with hyperbranched conformation was designed via freesolvent and self-catalytic methods,and then the different concentrations of waterborne sizing agent were prepared through adding a neutralizer.In addition,the introduction of 2,4-diominobenzene sulfonic acid sodium salt emerged a higher ionization strength between the emulsion particles.A strong electric double layer was formed,resulting in a powerful electrostatic repulsion in the emulsion.The formation of the electric double layer can effectively prevent the aggregation between the latex particles and improve the solid content of the emulsion(58%).After being treated with 1.5 wt% sizing agent,the CF/PA6 composites also represented excellent mechanical performance compared with the unsized composites.The ILSS and flexural strength of the CF-1.5 wt%/PA6 composites were up to 60.3 MPa and 508.4 MPa,with an increment of 50.3% and27.7%,respectively.This work also provides a new strategy for the preparation of environmentally friendly high-solid content sizing agents.(2)Based on the consideration of the production,storage,and transportation of the sizing agent,a waterborne branched polyurethane sizing agent with excellent storage stability was prepared.Polyethylene glycol,isophorone diisocyanate and 1,4-butanediol were used to synthesize the block polymer chain,and bio-based gallic acid was employed through a one-step method as a chain extender to synthesize polyurethane.Finally,the carboxyl groups of the system were neutralized by dropwise adding triethylamine and introducing 2,4-diominobenzene sulfonic acid sodium salt to prepare a waterborne polyurethane.The mechanical test results demonstrate that the 1.5wt% sizing agent was the best,and the mechanical properties were improved obviously.Besides,the storage stability of the sizing agent was tested by keeping the samples in a dry and cool place for 9 months.Compared with the above experiment,it has excellent storage stability and a longer shelf life.