Reinforcement Of Polyurethane/epoxy Interpenetrating Network Composites With Modified Palygorskite

Interpenetrating polymer networks (IPNs) are special polymer blends consisting of at least two polymers in a network, which is held together by permanent entanglement and shows excellent thermal stability and mechanical properties because of a synergetic effect induced by the forced compatibility of the individual components. Hence, IPNs have shown potential utility as functional materials in many applied fields in the last 3 or 4 decades.Polyurethane (PU) was widely investigated and utilized in many technical applications for its processibility, excellent abrasion resistance, oil resistance and low temperature performance. However, PU also has some disadvantages, such as low thermal stability and mechanical properties. Epoxy resins (EP) have been widely used in adhesives,construction materials, electronics, aircraft and spacecraft industries owing to their high strength and stiffness, chemical resistance, low viscosity. However, the cured resins are brittle and have poor resistance to the crack propagation. As a result, epoxy resins must be modified with other polymers to improve their physical and mechanical properties. PU/EP IPN can be considered to fulfill these requirements. The PU/EP IPN are relatively easy to synthesize and have outstanding properties. Recently, in order to futher wipen the performance and application, many methods have been used to improve the properties of PU/EP IPN. One of the most effective methods is to prepare nanocomposite materials by introducing nano-scale layered silicate into the matrix.Palygorskite (PGS) is a type of natural fibrillar silicate clay mineral that consists of chains of a 2 : 1 phyllosilicate structure , A fibrillar single crystal is the smallest structural unit, with a length of 500-2000 nm and a diameter of 10-25 nm. Structural characteristics and physicochemical properties provide PGS a unique role with respect to other clays.The main purpose of this work is focused on preparing composites with better performance via polyurethane/epoxy interpenetrating network with modified palygorskite,studying the relationship between structure and properties. The content consists of three parts as follows:1) In this part, an organophilic palygorskite (o-PGS) prepared by treatment of natural palygorskite with hexadecyl trimethyl ammonium bromide (HD TMAB) was incorporated into interpenetrating polymer networks (IPN) of polyurethane and epoxy resin (PU/EP) and a series of PU/EP/clay composites were obtained by a sequential polymeric technique and compression molding method. Tensile testing and thermal analysis proved that the mechanical and thermal properties of the PU/EP IPN composites are superior to the pure PU/EP IPN. XRD and SEM analysis showed that adding organophilic palygorskites could promote the compatibility and phase structure of PU/EP IPN matrices. In addition, the swelling behavior studies indicated that the crosslink density of PU/EP IPN gradually increased with increasing o-PGS content. The reason may be that the o-PGS can led to the chains become more rigid and dense.2) In this part, the EP/PU compound material with 2,4-toluene diisocyanate (TDI) grafted palygorskite has been prepared with the method of the interpenetrating polymer network ( IPN). The effects of preparation conditions, such as the mass ratio of EP to PU, the contents of g-PGS on the mechanical properties of the composite were investigated. The results showed that when the amount of polyurethane and g-PGS was lower, tensile strength and thermal properties were better. Synergistic effect may be easy to produce and the grafting reaction between PU, EP and g-PGS was perfect.3) A new flame retardant was synthesized from phosphoric acid, melamine and Substance A as the raw materials. Then flame retarding epoxy compound material was made by adding homemade flame retarding and organophilic palygorskite (o-PGS). Limiting oxygen index (LOI) and UL-94 V testing were used to characterize the flammability. The mechanical propertie testing, Thermogravimetric analysis (TGA) and Scan electronic microscopy (SEM) were carried out to investigate the flame retarding epoxy compound material. The results showed that the flame retarding epoxy compound material had better flame retardancy and smoke suppression than pure epoxy resin. Limiting oxygen index and UL94V flame retardancy of epoxy compound material with 30% of flame retardant and 5% of o-PGS reached 31 and V-0 grade, respectively. The reason is maybe the synergistic flame retardancy of the flame retardant and o-PGS in condensed phase. Tensile testing and thermal analysis proved that the mechanical and thermal properties of the epoxy compound material are perfect.