Reaction Wet Compression Molding Of Glass Fiber Reinforced Thermoplastic Polyurethane

Wet compression molding(WCM)is a liquid compression molding process that involves spraying resin onto the surface of dry fibers and then curing it in a mold.At present,thermosetting resins,such as epoxy resin and unsaturated polyester resin,are used for WCM molding,while wet molding of thermoplastic resin by monomer polymerization is rarely used.The thermoplastic resin monomer wet molding process has the characteristics of monomer in-situ polymerization,mold opening operation and low process requirements.At the same time,the thermoplastic resin generated by reaction polymerization has the advantage of recycling.It is a green and environmentally friendly molding method with great industrial value.However,the main problem of this process is that it is difficult to control the matching relationship between resin fluidity and reaction polymerization degree of thermoplastic resin during mold opening operation,and the study on the adaptability of reaction mechanism and equipment is not clear.In this project,4,4’-diphenylmethane diisocyanate(MDI),Butane-1,4-diol(BDO),Poly(1,4-butylene adipate)(PBA)as reaction raw materials,through one-and two-step polymerization of thermoplastic polyurethane(TPU),to determine the suitable reaction wet molding TPU polymerization process.Glass fiber reinforced thermoplastic polyurethane(GF/TPU)composites were prepared successfully.The influence of material parameters of reactive monomer and molding process parameters on the properties of TPU matrix and composites was investigated.Specific research contents are as follows:1.Compared the difference of resin viscosity and gel time in one-step polymerization and two-step polymerization,investigated the matching relationship between resin polymerization degree and resin fluidity,selected the polymerization method suitable for reactive wet molding,and developed the corresponding technological process and experimental equipment according to the polymerization method.At the same time through the experiment to mold surface treatment,release agent,sealing strip selection and optimization.2.The influences of material parameters such as isocyanate index(R value)and hard segment content on TPU molecular weight,reaction degree,crystallization degree,microstructure and mechanical properties of GF/TPU composites were explored.Through systematic study,the optimal material parameters were finally determined:The R value was 1.01,the hard segment content was 43%,the molecular weight of PBA was 2000,the catalyst was DBTDL,the addition amount was 0.06%,and the number of fiber layers was 6.3.The effects of process parameters on TPU molecular weight,reaction degree,crystallization degree,morphology and mechanical properties of GF/TPU composites were studied.The results show that:When the initial molding temperature is 60℃,the molding pressure is 2MPa,and the curing time is 2h,the TPU reaction degree is high,the fiber is well coated,the internal interlayer bonding is tight,the tensile strength of the composite material is298.5MPa,the impact strength is 161.6k J/mm~2,and the bending strength is214.2MPa.The bending modulus is 11.4GPa and the overall performance is maximum.The research results of this subject provide a new idea for in situ molding of thermoplastic resin and expand the application range of wet molding process.