D. Klempner

A review of kinetic studies on the formation of interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) are unique alloys of crosslinked polymers. This article reviews the studies on kinetic effects involved in IPN formation. Several investigators have studied the effect of kinetics of curing reactions on the morphology and properties of IPNs. It was found, in general, that the faster the rates of the respective chain extension and crosslinking reactions are and the closer they are to simultaneity, the more homogeneous are the IPNs. Other investigations revealed that the individual components sometimes can polymerize more rapidly in the IPN than alone, due to a “solvent effect” of the IPN. Effects of changing reaction variables, such as NCO/OH ratio, composition activators and temperature were used to study reaction kinetics as well as phase morphology by the Fourier transform infrared technique. Thermochemical techniques have been utilized to study the kinetics of IPN formation which influence phase separation. Small-angle X-ray scattering and small-angle neutron scattering techniques were used to estimate the extent of microheterogeneity of the phase domains in a study of the kinetics of phase separation in the IPNs.

Recent Advances in Polymer Alloys and IPN Technology

Abstract In this three part paper, we review the synthesis, morphology, and physical and mechanical properties of IPNs as well as the related pseudo-IPNs in which only one of the polymers is cross-linked. Recent studies have shown that the degree of phase separation achieved in these materials is strongly dependent on the compatibility of blends of the linear polymer constituents of the IPN components, as well as the kinetics of chain extension and the presence of grafting between component polymers in Part 2. We illustrate this by a series of IPNs consisting of a polyurethane and acrylic copolymer. The acrylic is a typical automotive enamel. An enhancement in properties results which is dependent on the amount of grafting and the kinetics of polymerisation. Also discussed in Part 3 are IPNs of a polyurethane and an epoxy, which exhibited a synerigsm in adhesive properties, and IPNs of a RIM polyurethane with several epoxies and unsaturated polyesters.

Barrier and Surface Properties of Polyurethane-Epoxy Interpenetrating Polymer Networks

The chemical and physical combination of two or more structurally dissimilar polymers has been of commercial and academic interest for a number of years, since it provides a convenient route for the modification of properties to meet specific needs. It has been used commercially to impart processing, flexibility, tensile and impact strength, chemical resistance, weatherability, flammability resistance, and a variety of other properties (1–4). The physical properties of the combined polymers not only depend on the properties of the constituent polymers but also on the way they are combined.

Laboratory performance of ASR modified asphalt binders

Automobiles, when they are no longer useful, are flattened and shipped to an automotive shredder facility. At the shredder facility, while they are shredded to recover the ferrous and non-ferrous metals for recycling, a huge quantity of non-metallic residue commonly called Automotive Shredder Residue (ASR) is generated. Since ASR mostly contains plastic and rubber related materials, and addition of plastic and scrap rubber from waste tires as a road material has been proven to be effective in solving existing pavement related problems, attempts were made to examine the feasibility of ASR as a road material additive. As a part of this effort, compatibility and mechanical properties of ASR modified asphalt were studied. The asphalt was mixed with a requisite amount of ASR for one hour at 375°F. Glass transition temperature (Tg) and microstructure of ASR, asphalt and ASR modified as-phalt were examined to determine compatibility. Mechanical properties of ASR modified asphalt were studied by performing dynamic mechanical analysis. The photomicrographs and Tg of ASR modified asphalt demonstrated some compatibility between ASR and asphalt. Dynamic mechanical analysis indicated that rutting and aging properties of asphalt should improve with the addition of ASR.

Nomenclature of Interpenetrating Polymer Networks

A nomenclature scheme for various types of interpenetrating polymer networks (IPN) based on morphology, topology, and method of synthesis is presented. In this scheme, IPN is the generic name of all polyblends of this type, regardless of their origin, as opposed to Sperlings recent classification of polyblends and graft copolymers, (Polymer Preprints, 14, (2), August, 1973), in which the various types of IPNs are given separate classifications under the generic heading of polyblends.

New Heat Resistant Isocyanate Based Foams for Structural Applications

This paper describes unique types of isotropic urethane-isocyanurate and urethane-urea isocyanurate foams based on a combination of an aromatic polyester polyol and an amine-containing tetrol as the only polyols with a low functionality polymeric isocyanate

Polyurethane-Acrylic Copolymer Pseudo Interpenetrating Polymer Networks

Previous investigations (1–6) have demonstrated that interpenetrating polymer networks (IPN’s) have exhibited better mechanical properties than those of their component networks. In addition, more complete phase mixing was observed for IPN’s than for blends of the corresponding linear polymers. These results were interpreted in terms of the permanent interlocking of the polymer chains of the composite structure. In this study, three different types of polymer blends, i.e., linear blends, pseudo-IPN’s and IPN’s, were prepared from a polyurethane and an acrylic copolymer. The polymers studied were similar to those used in an earlier study (7,8). However, the polyacrylate used in the present study cross-links by means of a free radical mechanism, while the polymer used previously was crosslinked with a melamine-formaldehyde resin via pendant hydroxyls. Therefore, in this study the possibility of grafting occurring between the component polymers is much less (i.e., reaction of the melamine with the hydroxyl-terminated chain extender for the polyurethane). The pseudo-IPN’s, made from a linear polymer and a crosslinked polymer, would theoretically result in temporary entanglements rather than permanent entanglements, which occur in the IPN’s.

Utilization of Polyurethane Foam Scrap as a Sole Binder for Recycling of Automotive Interior Trim Products

A number of rear-seat-to-back-window trim panels (CHMSL covers) were manufactured by thermoforming ground polyurethane-cored headliner (UROCOR) scrap with PMDI as a binder with and without water as a component of the composite mixture utilizing industrial equipment at a Lear plant in Holland, Michigan. Unexpectedly, it was found that UROCOR scrap which contains a significant amount of flexible and semi-rigid polyurethane foam can be thermoformed without addition of PMDI. In order to confirm that the polyurethane scrap can be used as a binder, the polyurethane seating foam scrap was successfully recycled as the sole scrap and in 75/25 and 50/50 mixtures with resinated fibers.

Secondary Amine Extended Flexible Polyurethane-Urea Foams

n the present work the effects on the physical properties of flexible foams prepared with a new liquid secondary diamine are described. This additive, UNILINK 4200, was first introduced for cast elastomer applications by UOP Inc. in 1986. The current effort summarizes the preliminary evaluation of UNILINK 4200 as an additive in flexible foam applications. The reactivity of secondary amines allows for the incorporation without significant changes in the rise profile. With the addition of UNILINK 4200 a decrease in density is observed. However, it was quite unexpected that the additional urea linkages and hard segment content would afford improved physical properties, such as strength and hardness, even at the lower densities. This benefit of lower foam densities, thus lower costs on a cubic foot basis, together with improved physical properties are expected to provide the polyurethane

Urethane-Based Polymer Alloys (IPNs)

nent polymers. IPNs possess several interesting characteristics in comparison to normal polyblends. Formation of IPNs is the only way of intimately combining crosslinked polymers, the resulting mixture exhibiting (at worst) only limited phase separation. Normal blending or mixing of polymers results in a multiphase morphology due to the well-known thermodynamic incompatibility of polymers. However, if mixing is accomplished simultaneously with crosslinking, phase separation may be kinetically controlled by permanent interlocking of entangled chains. Recent studies in IPNs at the University of Detroit’s Polymer Institute have encompassed a variety of areas, including effects of molecular weight of prepolymers and extent of crosslinking on the morphology and properties, the effects of charge groups and intentional grafts, pseudo-IPNs, and three component IPNs. The polymers studied have been polyurethanes, acrylic polymers and copolymers, and epoxies.