Study On Polyurethane/melamine-formaldehyde Interpenetrating Polymer Network Foams

Polyurethanes(PUs)are a broad class of polymers containing urethane groups(-NHCOO-),and are typically formed via the polyaddition reaction of polyhydric alcohols and polyisocyanate.These polymers have structures ranging from rigid to flexible,and had been commonly used in a variety of forms,including foams,elastomers,and adhesives.PU foams has exhibited excellent insulation,good mechanical properties,and low apparent density,and has been widely used in various industrial fields,including the construction,automotive,furniture,and cosmetics industries.As is well know,polyurethane foam,a kind of material with large specific surface area,is particularly vulnerable to burning and will give off large amounts of toxic gases and fumes in the combustion,thus bringing great harm to people's lives and public security.Therefore,the study of the flame retardant property of polyurethane foam has become a very important issue.UP to now,the major study has been focusing on the effectiveness of additive type flame retardant on flexible polyurethane foams,but mechanical performance properties have declined.To improve the performance of polyurethane foams,we will prepare the interpenetrating polymer network(IPN)by introducing a second reactive polymer to compensate for the shortcomings of existing polyurethane materials.This approach essentially can produce an interpenetrating polymer network(IPN).Melamine consists of a thermally stable s-triazine ring,and has been used as a standard industrial retardant in PU foams.However,the application of neat rigid PU foams has been restricted because of their high thermal expansion coefficient and low rigidity at high temperatures.One approach to improve the material properties is the introduction of a second reactive polymer into the PU reaction to compensate for the deficiencies of the existing material.This approach essentially can produce an interpenetrating polymer network(IPN).When PU foams burn,melamine mainly acts by eliminating ammonia in an endothermic manner and promoting the formation of insoluble products,thereby providing both a heat sink and gas-dilution effect.In this paper,melamine formaldehyde has been resined and polyurethane to form interpenetrating polymer foam,not only to improve the flame retardant polyurethane foam,while the mechanical properties have also been improved.The research results are as follows:1.This paper has studied the melamine and formaldehyde as raw materials to synthesize melamine formaldehyde resin in alkaline environment.The main factors include the mole ratio of formaldehyde,reaction time,solid content and so on.It is concluded that the optimum molar ratio of melamine to formaldehyde is 1:3,the best pH value is 8 ~ 9,and the best reaction time is 90 ~ 100 min.The best foaming conditions: MF 20 g,OP-10 1.0 g,formic acid 1ml,n-pentane 3 ml.2.When Melamine Foam Modified Polyurethane Foam,PU/MF IPN foams have been synthesized via a simultaneous IPN method and characterized by Tg measurements.The density and compressive strength of the foams has increased as the MF content increased.The flame retardancy of the PU foams has significantly improved by the addition of MF.SEM micrographs have revealed that the foams' average pore size initially decreased upon the addition of MF and then increased as more MF were added.3.When Polyurethane Foam Modified Melamine Formaldehyde Foam,PU/MF IPN foams have been synthesized via a simultaneous IPN method.The density and compressive strength of the foams have increased as the PU content increased.The tenacity of the PU foams have significantly improved by the addition of MF.SEM micrographs revealed that the foams' average pore size has not been changed.