Interpenetrating polymer network 3- phenol

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

An interpenetrating polymer network (IPN) consisting of an epoxy and an elastomer has been developed by Isayama.29 This is a two-component adhesive-sealant where the components are simultaneously polymerized. It consists of the MS polymer, developed in Japan by Kanegafuchi and commonly used in sealant formulations, with the homopolymerization of DGEBA using a phenol catalyst and a small amount of silane as a graft site to connect the MS polymer and epoxy homopolymer networks. 

Vinyl Compound and Phenolic Interpenetrating Polymer Networks... 

These compounds have the structure of an interpenetrating polymer network (IPN) of phenolic resin with materials having elastomeric properties. (3-8) Except for early work by Aylsworth in 1914, there has been no work on full IPN phenolic materials. 

The first IPN resin was invented by Aylsworth in 1914 (51). The mixture of rubber, sulfur, phenol and formaldehyde, on heating, yields a simultaneous interpenetrating polymer network... 

Hassan, A., Ken, L. S., Jawaid, M. (2013]. Flame retardancy and kinetic behavior of ammonium poljtphosphate-treated unsaturated polyester/phenolic interpenetrating polymer network,... 

Model reactions showed that the co-condensation reaction of melamine with phenolic resin occurs only by the reaction of phenolic methylol groups and the unsubstituted amino group at slightly acidic conditions. In contrast, a strong acidic or alkaline environment leads only to the formation of phenol methanal homocondensation products. The phenol reactivity in the reaction with methanal is low in comparison to the melamine reactivity in neutral and mildly acidic environments. An alkaline environment reverses this relative reactivity [99,100]. CiDsslinking of the products obtained by the reaction of 4-methylphenol and melamine with methanal appears to produce an interpenetrating polymer network [101]. 

Schematic Structure of an Interpenetrating Polymer Network Formed by Crosslinking of a Phenolic Prepolymer (Rectangles Connected by Short Lines) in Presence of Other Monomers (Network Junctions are marked with Full Squares in tiie Case of Phenolics and with Circles in Case of the Other Polymer)...

Phenolics can be chemically modified during synthesis by the use of substituted monomers or monomer mixtures. After synthesis additional modification can occur by electrophilic ring substitution, nucleophilic hydro l group capping, and reactions with compounds of boron, phosf orous, silicon, and titanium. Furthermore, phenolics can be physical modified by formation of polymer blends, interpenetrating polymer networks, and foam or by using fibers, fillers or other additives. 

Interpenetrating polymer network varnishes are composed of the phenolic resin, an epoxy resin, flame retardants, for example brominated epoxies or acrylates, and triphenylphosphate, polymerization initiators for radical polymerization of the acrylates and curing accelerators to catalyze the reaction between epor groups and phenolic groups. 

HDPE -1- butadiene/acrylonitrile rubber was compatibilized by addition of dimethylol phenolic resin, which cured and compatibilized the blend [61, 62]. Cure reactions of diene rubbers with phenolic resins have been observed before [159], and probably formed an interpenetrating polymer network in this study. 

Commercial interpenetrating polymer networks (not including thermoplastic compositions) include artificial teeth (Dentsply) made Ifom crosslinked PMMA mixed with MMA monomer and polymerized (sequential IPN), sound and vibration damping compositions (e.g., vinyl-phenolic Hitachi) and sheet molding compositions (acryhc/urethane/polystyrene Ferro Chemical) [164]. Water-borne acrylic methane semi-IPNs are commercial Ifom several sources where acrylate monomers are polymerized in the presence of a polymethane water dispersion. A silicone/polytetrafluoroethylene composition described as an IPN is offered by Biomed Sciences under the Silon tradename. The fluoropolymer provides the mechanical strength and the silicone rubber offers the softness and oxygen and moisture permeability for applications in the wound care area. 

Blends of elastomers are routinely used to improve processability of unvulcanized rubbers and mechanical properties of vulcanizates like automobile tires. Thus, cis-1,4-polybutdiene improves the wear resistance of natural rubber or SBR tire treads. Such blends consist of micron-sized domains. Blending is facilitated if the elastomers have similar solubility parameters and viscosities. If the vulcanizing formulation cures all components at about the same rate the cross-linked networks will be interpenetrated. Many phenolic-based adhesives are blends with other polymers. The phenolic resins grow in molecular weight and cross-link, and may react with the other polymers if these have the appropriate functionalities. As a result, the cured adhesive is likely to contain interpenetrating networks. 

Phenolics can be physically modified by blending, interpenetrating network formation, and the addition of fibers or fillers. The formation of multicomponent materials opens new directions for tuning of physical properties of polymers. 

Several mechanisms are needed to explain the action of the many different phosphorus compoimds used as FRs. Some of these compounds decompose in the condensed phase to form phosphoric acid or polyphosphoric acid. They can promote charring. Char formation is further enhanced by cellulosics, polyurethanes, phenolics, epoxy resins and EVA copolymers, and there are catalysts that promote it. Phenol-formaldehyde polymers can be used as flame retardants themselves when combined with a more flammable thermosetting polymer to form an interpenetrating network. 

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