L. H. Sperling

Multicomponent latex IPN materials: 2. Damping and mechanical behavior

The integrals of the linear loss shear modulus vs. temperature (loss area, LA) and linear tan δ vs. temperature (tan δ area, TA) were characterized for various core/shell latex particles with synthetic rubber, poly(butadiene-stat-styrene) [P (Bd/S), 90/10], and interpenetrating polymer networks (IPN) as the cores. The IPN cores were composed of P(Bd/S) (Tg ≃ − 70°C) and an acrylate based copolymer (Tg around 10°C) for potential impact and damping improvement in thermoplastics. Poly(styrene-stat-acrylonitrile) (SAN, 72/28) was the shell polymer for all these polymers. Under the same loading, for both toughening and damping controls, among the IPN core/shell, blend of separate core/shell, and multilayered core/shell polymers, the IPN core/shell polymers were the best dampers. However, the other core/shell polymers also showed higher LA values than P(Bd/S)/SAN core/shell polymer. A comparison of LA values via a group contribution analysis method was made, the effect of particle morphology and phase continuity on damping being studied. Inverted core/shell latex particles (glassy polymer SAN was synthesized first) showed much higher LA and TA values than normal core/shell ones (rubbery polymer was synthesized first). Models for maximum LA and TA behavior are proposed. The damping property was essentially controlled by the phase miscibility and morphology of the core/shell latex particles. The LA values for each peak in these multiphase materials provided some indication of the several fractional phase volumes.

Isocyanate‐functionalized latexes: Film formation and tensile properties

Latexes functionalized with isocyanate groups were prepared by carrying out the emulsion terpolymerization of dimethyl meta-isopropenyl benzyl isocyanate (TMI®) with methyl methacrylate and n-butyl acrylate. The film formation of these latexes and the tensile properties of the resulting latex films were studied. The effect of TMI concentration on the film properties was investigated. The locus of the isocyanate groups in the latex particles was controlled by using different polymerization processes. The locus of the functional groups was found to greatly influence the tensile properties of the latex films. Triethyl amine was used as an external catalyst to cure the TMI polymer films. One-component self-curable systems capable of undergoing crosslinking at ambient temperatures were developed by incorporating small amounts of methacrylic acid into the recipe. These systems exhibited significant improvement in tensile properties upon curing. In addition, the shelf-stability of these latexes was found to be excellent.

Morphology, design and characterization of IPN-containing structured latex particles for damping applications

Abstract We have prepared a series of novel structured latex particles with interpenetrating polymer network (IPN) cores and glassy SAN shells. The IPN cores were composed of two polymers: polybutadiene-based and acrylic-based. The morphologies of these latex particles were determined by TEM. The glass transition temperature and mechanical behavior of the polymers were characterized by DMS. The effect of different components on the final core/shell particle morphologies and mechanical properties was studied. The mechanical behavior of core/shell particles with IPN cores was also compared with that of separate core/shell and multilayered core/shell particles. In addition, normal core/shell synthesis (rubbery part first, then the glassy part) and inverted core/shell synthesis (glassy part first, then the rubbery part) were performed to provide another access for morphology design and control. It was found that the core/shell latex particles with poly(butyl acrylate)-based copolymers are more miscible than poly(ethylhexyl methacrylate)-based copolymers. The high grafting efficiency of poly(butyl acrylate) plays an important role in governing phase miscibility. The latex particles synthesized by the inverted core/shell mode showed higher miscibility than the normal synthesized ones. The damping properties of different core/shell particles were evaluated based on the loss area (LA) from dynamic mechanical spectroscopy measurements. The IPN core/shell polymers were found to be the best dampers due to their more miscible chemistry. The highest level of damping was achieved by inverting core/shell particles with dual-phase continuity compared to normal core/shell particles.

Toughening polycarbonate with core–shell structured latex particles

The toughness as a function of temperature of polycarbonate modified by blending with core-shell structured latex particles was evalated. Comparisons were made among a commercial core-shell latex (MBS), other core-shell (CS) latexes that incorporated a single component rubbery core, and a new class of interpenetrating polymer network (IPN) core-shell latexes with two elastomers in the core. Notched tensile tests differentiated among the blends in terms of their toughness. The most effective modifier at low temperatures was the commercial MBS latex. The CS latexes produced blends that were only slightly less tough than the MBS blends despite better dispersion of MBS and better adhesion to the matrix. The IPN blends were the least tough at low temperatures; however, at 25°C, a blend with IPN had the highest impact strength. Differences between CS and MBS blends were attributed to differences in the percent of butadiene-containing rubber and the chemical nature of the shell. A comparison among the CS latexes showed that increasing the acrylonitrile content of the shell increased the toughness, and increasing the rubber content or the gel fraction of the core increased the toughness.

CASTOR OIL BASED INTERPENETRATING POLYMER NETWORKS. III CHARACTERIZATION AND MORPHOLOGY

Interpenetrating polymer networks (IPNs) based on castor oil and polystyrene have been synthesized using 2, 4 tolylene diisocyanate (TDI), 80/20: 2,4/2,6 tolylene diisocyanate, and hexamethylene diisocyanate as crosslinkers for the castor oil component. The crosslink level of the polystyrene phase was maintained at 1% divinyl benzene (55%). The NCO/OH ratio for incipient infinite network formation was determined by experiment to be 0.64.

Morphology and Mechanical Behavior of Interpenetrating Polymer Networks

The synthesis and morphology of IPN’s are compared to the several other methods of preparing blends of distinguishable polymer pairs. Both components of IPN’s are continuous throughout, the very finely divided phase domain dimensions being controlled by the crosslink density.

Novel Plastics and Elastomers from Castor Oil Based IPN’s: A Review of an International Program

Among the renewable resources available in the world, plant products rank very high. Examples include cotton, which yields clothing; wood, for construction; and natural rubber, for automotive tires, etc. Many plants yield valuable oils, such as corn oil, linseed oil, and cotton seed oil (1). Besides food uses, these oils provide the basis for paints, adhesives and other industrial uses. The presence of multiple unsaturated sites allows for ready polymerization (2). Castor oil, which comes from the castor bean plant, is nearly unique among vegetable oils in containing hydroxyl groups in addition to points of unsaturation. Thus, there are two ways of polymerizing castor oil: through the use of sulfur or oxygen, which attacks the double bonds, or through the hydroxyl groups, to form polyurethanes, or polyesters, etc (3–5). As shown in structure (1), the number of double bonds and hydroxyl groups are identical, at three each per oil molecule (90% pure).

Poly(Butadiene-Co-Styrene)/Polystyrene IPN’s, Semi-IPN’s and Graft Copolymers: Staining Behavior and Morphology

Since the synthesis of interpenetrating polymer networks (IPN’s) in this laboratory in 1967,(1) the existence and importance of two-phase morphologies have become increasingly apparent.(2,3) A close relationship to graft copolymers has also been recognized. The research reported here is the first systematic study of the morphological relationships between IPN’s and graft copolymers of the solution graft type. Because of the critical role of staining in revealing morphologies on the 100 A scale, we have studied the kinetics of OsO4 staining as well.