Solvent or chemical resistance

For example, solvent or chemical resistance of adhesives used in surface-mount assembly may be tested according to Method 4.5.6 of ANSI/ lPC-SM-817, General Requirements for Dielectric Surface-Mounting Adhesives Although this method specihes specific solvents including isopropanol 1,1,1-trichlorotrifluoroethane an azeotrope of 6% methyl alcohol and 94% trichlorotrifluoroethane and a 10% alkaline... 

The carboxylic polyacrylates are effective as laminating adhesives for both flexible and rigid surfaces. The particular carboxylic acrylate used for a given laminating application is determined by the characteristics of the surfaces to be adhered, whether adhesive or cohesive bond failure is desired, the bond strength required of the adhesive, and many other factors. These may include stiffness, friability, extensibility, clarity, cold flow, moisture resistance, solvent or chemical resistance, heat and light insensitivity, radiation resistance, compatibility with resins and other polymeric materials or pigments, and vulcanizability. The carboxylic polyacrylates may be varied to meet the adhesive requirements of a specific application by ... 

Nitrocellulose based lacquers often contain short or medium oil alkyds to improve flexibiUty and adhesion. The most commonly used are short oil non drying alkyds. Amino resins or urethane resins with residual isocyanate functional groups may be added to cross-link the coating film for improved solvent and chemical resistance. The principal appHcations are furniture coatings, top lacquer for printed paper, and automotive refinishing primers. 

Modified alkyd resins In this group one finds styrenated alkyds, vinyl toluenated alkyds, oil-modified vinyl resins, acrylic alkyds, silicone alkyds and polyurethane alkyds. The modifying component usually has a number of effects. It always increases the molecular weight of the alkyd polymer, and may impart hardness, durability, or chemical resistance. It also affects the solubility of the polymer in solvents. 

Fillers often have a significant effect on the moisture resistance, the moisture-vapor transmission rate, and the solvent and chemical resistance of the cured adhesive bond. The effect, however, can be in either direction. Some fillers such as calcium carbonate tend to lower acid resistance, whereas others, such as silica or aluminum, may tend to lower alkali resistance. 

Because of the solvent and chemical resistance of acetal copolymer, special etching treatments have been developed for surface preparation prior to adhesive bonding. A chromic acid etch and a hydrochloric acid etch have been suggested. Acetal parts that have been formed by heat treatment or machining should be stress-relieved before etching. 

Polyamideimides (PAI) were obtained by polycondensation of imides with aromatic di-amines, [-N=(CO)2=(t)-CO-NH-R-NH-CO-(t)=(CO)2=N-] (Tg = 275°C, HDT = 265-280°C). The resin has high tensile and impact strength from T = -190 to T = 260°C, dimensional stability, good dielectric properties, solvent and chemical resistance, flame retardancy, good UV stability and low outgassing in high vacuum. To improve processability, PAI was blended with PA, PSF, or PEST [Toray Industries, Inc., 1979]. 

Numerous blends exhibiting good solvent and/ or chemical resistance (in addition to other properties) have been described, viz., based on polyole-hns [Yamamoto, 1991 Aleckner et al., 1986 Sezaki et al., 1990 Takada et al., 1991], fluo-ropolymer-PA type [Kawashima and Yoshida, 1991], PPE [Brown et al., 1992 Arashiro et al., 1992 Nakajima and Misoo, 1991], PC [Tera et al, 1992 Endo et al, 1987, 1989], PEST [Ohmae et al, 1992],... 

PCL is commonly used in the manufacture of polyurethanes because of its imparting good water, oil, solvent, and chlorine resistance to the polyurethane produced. In 1934, Carothers et al. [103] prepared epsilon-caprolactone for the first time. Under the condition of heat epsilon-caprolactone is converted to a polyester of high molecular weight. The 1965, Magnus [104] published details of his study of effects of components and varying -NCO/-OH or -NCO/-NH2 group ratio on the low-temperature properties, hydrolytic and heat stability, and solvent and chemical resistance of the polyurethane elastomers. It was found that... 

These blends are immiscible, thus should be compatibilized and toughened. Addition of POM to PC improves the solvent and chemical resistance (MUler 1972). PC blends with POM and TPU were easy to mold into articles having high impact strength (Silvis et al. 1990). POM-b-PC was used either as a compatibilizer or as a modifier of performance for such polymers as PES, PEEK, PA, and PAN (Dhein et al. 1993). 

The general motivation for blending styrenic resins with other polymers, particularly with the higher-priced, high-Tg, amorphous engineering resins such as polycarbonate, or polyphenylene ether, is primarily to lower the cost and improve the processabihty of the latter resins. The main reason for blending styrenic resins with crystalline polymers such as PA6 and PBT is to improve the solvent and chemical resistance which the styrenics lack. 

For noncompatibilized PP/PC blends, the compositional dependence of the heat deflection temperature (HDT), modulus, yield and frachue strength showed a negative deviation from additivity. Addition of a compatibilizer improved the blend performance. Excellent mechanical properties, impact strength, HDT, moldability, and solvent and chemical resistance have been claimed for compatibilized blends containing 5-95 wt.% of either PP or PC. The best overall effects were observed using poly(propylene-g-styrene/acrylonitrile). 

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