Research On Flame Retardant Behavior And Mechanical Properties Of Rigid Polyurethane Foam Used For Sandwich Panels In Storage And Transportation Warehouses

Because of the heavy weight of the partition in the pure metal storage and transportation warehouse,it is difficult to transport and install.Therefore,the sandwich partition is proposed.Rigid Polyurethane foam(RPUF)has many advantages such as light weight,thermal insulation,corrosion resistance,mass production and easy cutting.It is usually used as a sandwich composite core material.However,RPUF has large specific surface area and low oxygen index,so it is easy to be ignited.It brings immeasurable harm to people.This fatal disadvantage seriously limits its application range.Therefore,in order to ensure the safety of people's lives and property,RPUF must be flame retardant modified.Expandable graphite(EG)and ammonium polyphosphate(APP)are halogen-free,low smoke,environmentally friendly flame retardants,which are widely used in polymers to reduce the flammability of materials.In this thesis,the main work of flame retardant modification of RPUF is as follows:(1)RPUF/EG flame retardant composites were prepared by adding a single EG flame retardant in RPUF and one-step free foaming.The effects of EG on the density,mechanical properties,thermal stability and flame retardant properties of RPUF/EG composites were studied.It was found that with the increase of EG addition,the density,thermal stability and flame retardant properties of RPUF/EG composites were improved,but the mechanical properties of RPUF/EG composites decreased to some extent.At the same time,it was observed that the "worm like" expanded carbon layer was formed on the combustion surface of the composites filled with EG,and the more EG was added,the more obvious the "worm" effect was.When the EG content amount was 20wt%,the flame retardant RPUF/EG composites exhibited the excellent comprehensive properties.(2)RPUF/EG/APP flame retardant composites were prepared by one-step free foaming method with different proportions of EG and APP added at 20wt%.The effects of the ratio of EG and APP on the density,mechanical properties,thermal stability and flame retardant properties of RPUF/EG/APP composites were studied.It was observed that the dense carbon layer generated by APP could fill the gap between the "worm-like" expanded carbon layers generated by EG.Therefore,when RPUF was filled with EG and APP in any proportion,the thermal stability and flame retardant of the composite flame retardant system were better than that of single APP or EG.The density and mechanical properties of RPUF/EG/APP composites increased with the relative content of EG in the flame retardant system,but the mechanical properties were worse than pure RPUF.Among them,when the ratio of EG and APP was 1:1,the corresponding flame retardant RPUF/EG10/APP10 composite had the best comprehensive properties.(3)RPUF/EG10/APP10-BDO reinforced composites were prepared by bulk grafting technology,in which 10wt% EG and 10wt% APP were introduced into the molecular chain of RPUF by solution method,and the effects of BDO on the density,mechanical properties,thermal stability and flame retardancy of the composites were investigated.The results showed that the density of the composites increased with the introduction of BDO,and the combustion carbon layer of the composites was more compact and dense than that of RPUF/EG10/APP10 composites.The compressive strength,impact strength and carbon residue rate of the composites increased firstly and then decreased with the increase of BDO content.When the BDO content was 4wt%,the composite had the best comprehensive properties.(4)Using 20 mm thick pure RPUF and RPUF/EG10/APP10-BDO4 composite as core material,and 1 mm thick Q235 steel plate as surface layer,composite plate sample 1 and composite plate sample 2 were prepared by using epoxy resin adhesive.The load bearing capacity of the two composite plates was evaluated by comparing bonding strength,shear strength,compressive strength and bending strength.The results showed that the mechanical properties of composite structural plates depend on the properties of the core materials.Taking the modified flame retardant RPUF/EG10/APP10-BDO4 composite as the core material,the sandwich structure plate could be endowed with better mechanical properties.After testing,the bonding strength,shear strength,compressive strength and bending strength of composite plate sample 2 were 34 MPa,83MPa,16.4MPa and137.7MPa respectively,which were better than that of composite plate sample 1 with the same size design.