Polymer Blends (or Alloys)

Interpenetrating polymer networks (IPN’s) are a unique type of polyblend, synthesized by swelling a crosslinked polymer (I) with a second monomer (II), together with crosslinking and activating agents, and polymerizing monomer II in situ (Sperling, 1974–1975 ; Sperling and Friedman, 1969). The term IPN was adopted because, in the limiting case of high compatibility between crosslinked polymers I and II, both networks could be visualized as being interpenetrating and continuous throughout the entire macroscopic sample.* As with other types of polyblends, if components I and II consist of chemically distinct polymers, incompatibility and some degree of phase separation usually result (Sperling, 1974–1975; Sperling and Friedman, 1969; Sperling et al., 1970a,b,c; 1971). Even under these conditions, the two components remain intimately mixed, the phase domain dimensions being on the order of hundreds of angstroms. If one polymer is elastomeric and one polymer is plastic at the use temperature, the combination tends to behave synergistically, and either reinforced rubber or impact-resistant plastics result, depending upon which phase predominates (Curtius et al., 1972; Sperling and Mihalakis, 1973; Sperling et al., 1971; Huelck et al., 1972). Among the other kinds of polymer blends discussed in this monograph, the graft-type copolymers are the ones most closely related to the IPN’s.

Interpenetrating Polymer Networks

Thermosetting polymers are frequently used in formulations, including rubbers, thermoplastic polymers or oils, etc, in an amount of the order of 2–50 wt% with respect to the thermoset. This extra component, called the modifier, may initially be immiscible or may phase-separate during cure. This last process, i.e the reaction-induced phase separation, is the subject of this review. A thermodynamic description of the process is made, using the Flory-Huggins equation at two approximation levels, i.e. a quasi-binary approach and a multicomponent treatment taking polydispersity of constituents into account. Thermodynamic factors affecting the phase separation process are thus established. Nucleation and growth (NG) and spinodal demixing (SD) are considered as possible phase separation mechanisms. Factors promoting one or the other process are discussed. The control of morphologies generated is analyzed on the basis of thermodynamic and kinetic arguments. Ideas for obtaining particular morphologies enhancing particular properties are put forward.

Reaction-induced phase separation in modified thermosetting polymers

The radiation chemistry of fluoropolymers

This invention relates to modified aqueous dispersions of water-insoluble latex polymer prepared by swelling an initial water-insoluble latex polymer, prepared by emulsion polymerization, with additional ethylenically unsaturated monomer, including at least one monomer with two or more sites of ethylenic unsaturation, and subsequently polymerizing the additional monomer within the swollen latex particles.

Modified latex polymer compositions

Interpenetrating Polymer Networks of Poly(ethyl acrylate) and Poly(styrene-co-methly methacrylate). I. Morphology via Electron Microscopy

Interpenetrating Polymer Networks Based on SBR/PS. 1. Control of Morphology by Level of Cross-Linking

In previous papers, interpenetrating polymer networks were shown to display a cellular structure. The phase domain size of polymer II was shown to depend inversely on the crosslink density of polymer I. The present paper presents a semiempirical derivation of equations which show quantitatively the dependence of the phase domain size of polymer II on the crosslinking density of polymer I, and also on the interfacial energy and the overall composition. If polymer II is linear, the dependence on the molecular weight of polymer II is also included. The values of the phase domain sizes so estimated are compared with experimental results. While theory and experiment yield good agreement, the semiempirical nature of the equations must be borne in mind.

A semiempirical derivation of phase domain size in interpenetrating polymer networks

Interpenetrating Polymer Networks Based on SBR/PS. 2. Influence of Synthetic Detail and Morphology on Mechanical Behavior

Damping systems based on interpenetrating polymer networks (IPN's) provide noise and vibration attenuation over broad temperature and frequency ranges. Semicompatible latex IPN's are employed in both extensional and constrained layer configurations. The damping behavior of IPN's of compositions poly(ethyl methacrylate)/poly(n-butyl acrylate) [PEMA/PnBA], poly(ethyl methacrylate–co–ethyl acrylate)/poly(n-butyl acrylate–co–ethyl acrylate) [P(EMA–co–EA)/P(nBA–co–EA)], and poly(vinyl chloride)/poly(butadiene–co–acrylonitrile) [PVC/P(B–co–AN)] were investigated and compared to both commercially available materials and to theory. The damping of both the PEMA/PnBA and the P(EMA–co–EA)/P(nBA–co–EA) IPN's in a constrained layer configuration was significantly better, over a broad temperature range of −10° to 60°C, than the commercial materials. In addition, the P(EMA–co–EA)/P(nBA–co–EA) IPN was found to be effective in damping phenolic-impregnated Kevlar cloth laminates. A reduction of 10 dB in impact noise resulted with a 6–8% by weight layer inserted between the Kevlar-phenolic panels. The relationship between the peak damping temperature of a constrained layer system to maximum tan δ along with that of an extensional damping system to maximum E″ was also demonstrated. Although the amount of damping predicted by the theory approached that found experimentally, sufficient differences existed such that the exact detail of the damping curve was not described.

D. A. Thomas

Papers

Interpenetrating Polymer Networks of Poly(ethyl acrylate) and Poly(styrene-co-methly methacrylate). I. Morphology via Electron Microscopy

Interpenetrating Polymer Networks Based on SBR/PS. 1. Control of Morphology by Level of Cross-Linking

A semiempirical derivation of phase domain size in interpenetrating polymer networks

Interpenetrating Polymer Networks Based on SBR/PS. 2. Influence of Synthetic Detail and Morphology on Mechanical Behavior

Noise and vibration damping with latex interpenetrating polymer networks