Interpenetrating elastomer networks

IPN s and related materials) in fact) have a long history. For example) IPN s were first synthesized to produce smooth sheets of bulk polymerized homopolymers (11), IPN s were next used as solution polymerized ion exchange resins. (12) 13) Further development of IPN s included the syntheses oT interpenetrating elastomer networks (lEN s) and simultaneous interpenetrating networks (SIN s) (14). lEN s consist of a mixture of different emulsion polymerized elastomers which are both crosslinked after coagulation. SIN s are formed by the simultaneous polymerization of mixed monomers by two noninterfering reactions (3 ) 16). 

If the latex components are crosslinked after the bulk product is formed, the material is known as an interpenetrating elastomer network (lEN), discussed in Section 8.5. 

Latex lENs. Latex interpenetrating elastomer networks, latex lENs, are latex blends that have been cross-linked after film formation. They are named after the early works of Frisch and co-workers, who called these materials interpenetrating elastomer networks (Frisch et al. 1969b). Many latex blends, as used in coatings especially, are cross-linked as finally used in service. 

DACBA Diallyl carbonate of bisphenol-A DMS Dynamic mechanical spectroscopy EA Ethyl acrylate EMA Ethyl methacrylate EPDM Ethylene-propylene-diene copolymer HEMA Hydroxyethyl methacrylate lENs Interpenetrating elastomer networks IPN Interpenetrating polymer network LA Loss area... 

Figure 6.7. Electron micrographs of interpenetrating elastomer networks from mixed polyacrylate and polyurethane latexes (a) 70/30 (b) 50/50 (c) 30/70 polyacrylate/polyurethane. Polyurethane stained with osmium tetroxide. ...

The lENs (interpenetrating elastomer networks) are blends of two kinds of latexes, both of which are pre-cross-linked. The surface modification grafts involve grafting of polymer 2 onto the surface of a polymer 1, often to alter the surface characteristics of the material such as contact angle, polarity, or bondability. 

Where the polyurethane comprises <30% of the blend, the polyurethane remains in discrete droplets within the polyacetal matrix. In this range the particle size and particle size distribution of the elastomer particles are of importance. Where the elastomer component is in excess of 30%, interpenetrating polymer networks exist in the sense that there are two interpenetrating continuous phases (as opposed to two cross-linked interpenetrating polymer systems). 

This is a theoretical study on the structure and modulus of a composite polymeric network formed by two intermeshing co-continuous networks of different chemistry, which interact on a molecular level. The rigidity of this elastomer is assumed to increase with the number density of chemical crosslinks and trapped entanglements in the system. The latter quantity is estimated from the relative concentration of the individual components and their ability to entangle in the unmixed state. The equilibrium elasticity modulus is then calculated for both the cases of a simultaneous and sequential interpenetrating polymer network. 

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. 

Energy-Absorbing Multicomponent Interpenetrating Polymer Network Elastomers and Foams... 

Two- and three-component interpenetrating polymer network (IPN) elastomers composed of polyurethanes (PU), epoxies (E), and unsaturated polyester (UPE) resins were prepared by the simultaneous technique. Fillers and plasticizers were... 

Fig. 1.14 Fabrication steps for IPN elastomer films. The film is first prestrained, then an multifunctional monomer additive is sprayed onto the host film and polymerized forming an interpenetrating polymer network. Upon releasing the film it retains most of the applied prestrain, with the additive network being in compression and the host film in tension [200], Proc SPIE 2007, reprinted with permission...

Zhang H, During L, Kovacs G, Yuan W, Niu X, Pei P (2010) Interpenetrating polymer networks based on acrylic elastomers and plasticizers with iminoved actuation temperature range. Polym Int 59 384-390. doi 10.1002/pi.2784... 

More recently, iodonium salts have been widely used as photoinitiators in the polymerization studies of various monomeric precursors, such as copolymerization of butyl vinyl ether and methyl methacrylate by combination of radical and radical promoted cationic mechanisms [22], thermal and photopolymerization of divinyl ethers [23], photopolymerization of vinyl ether networks using an iodonium initiator [24,25], dual photo- and thermally-initiated cationic polymerization of epoxy monomers [26], preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran) [27], photoinduced crosslinking of divinyl ethers [28], cationic photopolymerization of l,2-epoxy-6-(9-carbazolyl)-4-oxahexane [29], preparation of interpenetrating polymer network hydrogels based on 2-hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone [30], photopolymerization of unsaturated cyclic ethers [31] and many other works. 

Brochu P, Stoyanov H, Niu X, Pei Q (2013) All-silicone prestrain-locked interpenetrating polymer network elastomers free-standing silicone artificial muscles with improved performance and robustness. Smart Mater Struct 22 055022... 

The field of interpenetrating polymer networks now takes its place parallel to the fields of polymer blends, grafts, and blocks. Indeed, most of these materials are useful because they imdergo some kind of phase separation. Many IPNs seem to work best when the degree of phase separation is only partial or the size of the domains is in the tens of nanometer range. Those IPNs composed of an elastomer and a plastic to make flexible materials seem to be the most imique among these materials. 

Another procedure for synthesis of polsrmer blends is by formation of interpenetrating polymer networks. A network of one polymer is swollen with the other monomer or prepol5mier after that, the monomer or prepolymer is crosslinked (63). In contrast to the preceding methods used for thermoplastics and uncrosslinked elastomers, blends of reactoplastics are prepared by this method. Phase Structure Development in Molten State. 

In a series of papers concerned with functional group oils (51), natural castor oil was polymerized and formed into interpenetrating polymer networks. (Using a 60/40 SIN of polystyrene and castor oil, this research team made a pair of shoe heels which have seen wide service on and off the lecture podium. The product is a very tough elastomer.)... 

As part of an investigation of the use of renewable feedstocks to synthesize polymers, a series of simultaneous interpenetrating networks (SINs) were prepared in which an elastomer network based on epoxidized botantical oils was combined with a glassy polymer network of crosslinked polystyrene (PSN). Thus SINs were successfully prepared containing from 5% to 40% elastomer based on epoxidized linseed, crambe, lunaria, and lesquerella oils. 

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