Research On The Preparation Technology Of Polyurethane Homogenous Reinforced Composite Material By In-mold Reaction Molding

Polyurethane materials have unparalleled designability in material properties and can meet diversified application needs.Polyurethane-based composites with fibers as reinforcing materials enhance the material properties and are widely used in various fields.However,the recyclability of traditional composite materials is limited,and they cannot be fully melted and recycled at the end of the life cycle,and the end-of-life disposal of materials may lead to critical environmental pollution.It does not meet the mainstream trend of increasing demand for environmentally friendly materials in the industry,resulting in limited application prospects.Single-polymer composite material is a kind of composite material in which both the matrix material and the reinforcement material are from the same polymer.And the single-polymer composites have higher chemical compatibility and good interfacial bonding.However,no research has been carried out on polyurethane-based single-polymer composite materials in China,in this project,the in-mold reaction molding method is used to prepare polyurethane-based monopolymer composites.In the end of life span,for thermosetting composites,after high temperature decomposition,the polyurethane monomer can be recycled,the liquid can be used as fuel oil,and the residue can be used as composite material filler.For thermoplastic composites,it could be absolutely melted and recycled after being scrapped,which greatly settles the environmental pollution caused by traditional material recycling stage.Through the experimental study to analyze the influence of the reaction molding preparation process on the properties of the composite material.Provide help for the application research of polyurethane-based single-polymer composite materials in automotive parts,soft robots.The thesis mainly studies the following contents:A new molding process for preparing polyurethane-based single-polymer composites by in-mold reaction molding is innovatively proposed,and a molding experimental platform is built and related experimental studies are carried out.The molding experiment platform includes a reaction injection molding machine for polymerization reaction molding of polyurethane,and a reciprocating filament winding machine for fiber stabilization winding before molding.The results show that the established experimental platform has good repeatability and can stably prepare polyurethane-based single-polymer composites.Explore and determine the raw material formula ratio of thermoplastic polyurethane.After repeated experiments and demonstrations,the formulation system of thermoplastic polyurethane elastomer adopts the total molar ratio of polyether polyol,isocyanate and glycol chain extender is n(polyether polyol):n(isocyanate): n(chain extender)= 1:2:1,it is the best ratio of materials.The effects of three reaction molding process parameters,fiber mass fraction,post-curing process parameters,and fiber preload on the properties of composites are explored.First,for thermosetting polyurethane-based singlepolymer composite materials: the test results show that the appropriate fiber mass fraction can make the tensile strength of hard materials reach a maximum of 26.25 MPa,and the strength enhancement efficiency can reach 142.6%;The efficiency reaches 284.62%,and the modulus enhancement efficiency reaches53.17%.It shows that the appropriate fiber mass fraction can effectively enhance the mechanical properties of polyurethane-based monopolymer composites;And proper post-curing process can make the maximum tensile strength of the elastomer material reach 11.01 MPa,and the strength enhancement efficiency can reach 19.02%.In addition,the post-curing process has no obvious effect on the thermal stability of the composite material,but it will promote the full reaction of the initially formed composite material and increase the hardness value.It shows that suitable post-curing process can improve the properties of polyurethane-based monopolymer composites.Second,For thermoplastic polyurethane-based monopolymer composites: with the rise of fiber preload,the elongation at break of the composite material gradually reduces,and the tensile strength and modulus rises gradually.When the fiber preload is 0.9N,the maximum tensile strength is 20.99 MPa,and the strength enhancement efficiency is 84.5%.The highest modulus enhancement efficiency is 85.3% when the preload is 1.1N.It shows that good fiber preload can improve the mechanical properties of polyurethane-based monopolymer composites.