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SYNOPSISPoly(viny1 acetate) and vinyl acetate-ethylene (VAE) copolymers compose one of the more important polymeric materials, widely employed in coating and adhesive applications. A new class of miscible polymer blends involving poly(viny1 acetate) and VAE with styreneacrylic acid and acrylate-acrylic acid copolymers has been found. Experimental windows of miscibility as a function of the ethylene content for VAE copolymers and the acrylic acid content of the acrylate-acrylic acid copolymers are observed (acrylate = methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate). Employing well-established analog heat of mixing measurements, predicted windows of miscibility were compared with experimental results. Fair qualitative agreement was observed and supported the hypothesis that specific rejection arguments can be employed to explain the observed miscibility. Failure to quantitatively predict miscibility based on the analog heat of mixing measurements may be due to the higher association tendencies of the model compounds relative to acrylic acid units in the high molecular weight polymers. No miscible combinations were found for methyl methacrylate-acrylic acid copolymers or acrylate-methacrylic acid copolymers in admixture with poly(viny1 acetate) or the VAE copolymers, thus indicating the sensitivity of phase behavior to minor structural changes. VAE (30 wt % ethylene) copolymers were also noted to be miscible with several polymers previously noted to be miscible with poly(viny1 acetate), namely, poly(viny1idene fluoride), poly(ethy1ene oxide), and nitrocellulose. 0 1995 John Wiley & Sons, Inc. I NTRO D UCTl ONPoly (vinyl acetate) and vinyl acetate copolymers are among the more important commodity polymers utilized in the large coating and adhesive markets. As such, polymer blends comprising vinyl acetatebased polymers are of significant interest. As vinyl acetate-based polymers have been available for over 60 years, a large number of blend combinations have been reported in the open and patent literature. The study presented here discusses a new class of polymer blends miscible with poly (vinyl acetate) ( PVAc) and vinyl acetate-ethylene (VAE) (270 wt % VAc ) copolymers, namely, acrylate-acrylic acid and styrene-acrylic acid copolymers.

Acetylene terminated polyimide prepolymers have many advantages over conventional polyimides in the areas of processing and solvent resistance. In addition, the presence of the isoimide structure further extends the the utility of these systems by modification of the solubility properties and glass transition temperature. This work discusses the thermal crosslinking and isomerization reactions occurring in the acetylene terminated isoimide prepolymer: Thermid IP600. The techniques of Fourier Transform Infrared Spectrometry and Differential Scanning Calorimetry are used to determine the contribution of these two reactions during the thermal cure including their kinetics at 183°C.The increasing need for high service temperature adhesives and structural matrix resins has led to the development of many new polymeric systems in recent years. One of the most interesting and potentially useful of these new polymers is polyimides.Polyimides are noted for their excellent thermal and mechanical properties but their utility has been severely limited due to problems with fabrication and processing of these polymers (1-3). Nevertheless, the careful design of polyimides can lead to enhanced processability.In this respect, several approaches have been investigated and found to be useful.One design method which has improved the processability of linear aromatic polyimides is the introduction of meta-substituted aromatic diamines for para substituted analogs (4,5). This procedure, while improving the processability, also has the possible detrimental effect of lowering the glass transition temperature.Another method which has been successfully utilized in improving polyimide processing and solubility characteristics is the incorporation of bulky side groups such as phenylated diamine monomers (6). Although these materials maintain a high glass transition temperature their resistance to solvents may be sacrificed.Processability can also

SynopsisModification of properties of an addition-curing polyisoimide prepolymer is achieved by the incorporation of small metal particles. No evidence for the modification of the cure chemistry of the prepolymer is observed. Physical modification of the system is observed in electrical, dynamic mechanical, and adhesive properties. Compositions containing various volume fractions of metal and polymer were prepared. Two different molecular weights of prepolymer were studied. Samples were prepared by fabricating single overlap adhesive specimens to aluminum. These lap shear specimens were then used for the electrical and adhesive properties of the material. The electrical properties improved markedly at above 25 volume percent metal loading. The adhesive properties to aluminum showed a maximum at 20-25 volume percent loading. X-ray photoelectron spectroscopy was used to examine adhesive failure surfaces.