Resin choice

Colour. The colour of resins ranges from water-white to dark brown. Colour may be an important factor in resin choice depending on end use. Pale colours are necessary in some types of adhesives, whereas darker colours may be tolerated in rubber formulations, especially where carbon black filler is incorporated. Medium-coloured resins can be used in most adhesive formulations. 

Table II. Outdoor Exposure Data as a Function of Resin Choice...

This chapter will provide a concise summary of the main technologies and applications. Distinction will be made between PE and PP in terms of their suitability for specific fiber and nonwoven applications. Resin choice, in terms of its molecular weight and formulation, is critical not just to the final product performance but also to the type of technology used to convert the resin. 

Splitting Excessive orientation in machine direction Die lines Degraded resin Poor resin choice Increase blow-up ratio See die lines Reduce melt temperature Ensure resin is suitable... 

Therefore with less solvent, resin choice is more limited and as the systems technology is stretched, the performance characteristics of the coating are altered compared to a traditional system. Usually a low solvent product will be more specialised than the traditional solvent based version, often meaning more restricted flexibility in application or use. 

The surge in new electronic products led by small computer-based devices has resulted in significant changes in resin choices for enclosures. Downsizing and more importantly, the rush to thin-wall constructions have led to a change in resin selection for enclosures. 

Polypropylene is widely used in both small and large appliances. In small appliances, like electric drip coffee makers, can openers, blenders, and mixers, and in tools, like electric drills, PPs ease of molding, light weight, stiffness, durability, electrical properties, appearance, and cost make it a very attfactive resin choice. Homopolymers and impact copolymers are both used, with an MFR of around 12 g/10 min being the norm. 

This paper provides an overview of water-borne coatings from a practical formulating point of view, and sheds light on how to achieve specific properties in water systems. It deals first with the question of differentiating between the types of water-homes, then looks at resin choices, facets of formulation, and where to expect new technologies. 

Each reference should therefore be used as a guide only to the likely location of additional, afiemative systems. Their separate descriptions - as tabulated later - should then be employed as a Tirst-filter choice, prior to contacting the manufacturers/suppliers to request more defintive technical data, from which a final optimum thermoset resin choice/s can be made. 

Clearly the variety of uses to which thermoplastic acrylic resins (TPA) are put, has meant that many polymers have been formulated to meet the demands of particular applications. In most instances, where TPA s are used, they are the major, or even sole binder component. A good understanding of acrylic polymer technology is therefore essential for optimum resin choice. 

The acrylic component can now contain reasonable amounts of styrene which reduces cost and the isocyanate component can be aromatic instead of the more expensive aliphatic variety. (Although IBM and Compaq have non - yellowing requirements that preclude the use of aromatic isocyanates.) Textured formulations with low gloss levels are popular decorative requirements in this industry, used to break up the hard lines of a computer box to make it more acceptable to the eye. Application is by conventional spray, often robotically applied in this high volume production industry. Above ambient or ambient cure and rapid handling time to permit sub assembly after the box is coated, means that acrylic is the only viable resin choice. 

Although ABS resins have a long history by industry standards, the products are anything but mature. ABS resins and blends are, and are expected to remain, the engineering thermoplastics of choice for a wide array of markets. 

Rubber-mill chips are dissolved similarly to resins, to provide color concentrates. Dough mixer and chip concentrates must be diluted with solvent and other vehicles to make finished inks. Media milling is becoming a method of choice in both flexo and gravure ink manufacturing. Other high speed dispersing units, such as the Morehouse, Cowles, Kady, and others, are also used. 

Hot pressing with a smooth plate has an advantage in smoothing the grain, and the heat can be used to cure the resin of the finish. The hot pressing is anticipated in the design of the finish system and in the choice of the resins by the finish manufacturer. 

Binders and Resins. The choice of binder is the most important ingredient choice in the formulation process because the binder affects the performance properties of a paint more than any other single ingredient (3). The physical properties of binders required for paints include the abiHty to dry or cure under various ambient conditions, good adhesion to various substrates, abrasion resistance, washabiHty, flexibiHty, water resistance, and ultraviolet light resistance. The balance of these required properties is mosdy dependent on whether the paint is being developed for interior or exterior appHcations. 

Spectroscopy. Infrared spectroscopy (48) permits stmctural definition, eg, it resolves the 2,2 - from the 2,4 -methylene units in novolak resins. However, the broad bands and severely overlapping peaks present problems. For uncured resins, nmr rather than ir spectroscopy has become the technique of choice for microstmctural information. However, Fourier transform infrared (ftir) gives useful information on curing phenoHcs (49). Nevertheless, ir spectroscopy continues to be used as one of the detectors in the analysis of phenoHcs by gpc. 

Substituted heat-reactive resins are most widely used in contact-adhesive appHcations and, to a lesser extent, in coatings (77,78) -butylphenol, cresol, and nonylphenol are most frequendy used. The alkyl group increases compatibiHty with oleoresinous varnishes and alkyds. In combination with these resins, phenoHcs reduce water sensitivity. Common appHcations include baked-on and electrical insulation varnishes, and as modifiers for baking alkyds, rosin, and ester gum systems. Substituted heat-reactive resins are not used for air-dry coatings because of theh soft, tacky nature in the uncured state substituted nonheat-reactive phenoHcs are the modifying resin of choice in this case. 

Over 70% of the total volume of thermoplastics is accounted for by the commodity resins polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) (PVC) (1) (see Olefin polymers Styrene plastics Vinyl polymers). They are made in a variety of grades and because of their low cost are the first choice for a variety of appHcations. Next in performance and in cost are acryhcs, ceUulosics, and acrylonitrile—butadiene—styrene (ABS) terpolymers (see... 

In general, polycarbonate resins have fair chemical resistance to aqueous solutions of acids or bases, as well as to fats and oils. Chemical attack by amines or ammonium hydroxide occurs, however, and aUphatic and aromatic hydrocarbons promote crazing of stressed molded samples. Eor these reasons, care must be exercised in the choice of solvents for painting and coating operations. Eor sheet appHcations, polycarbonate is commonly coated with a sihcone—sihcate hardcoat which provides abrasion resistance as well as increased solvent resistance. Coated films are also available. 

The properties of polymers formed by the step growth esterification (1) of glycols and dibasic acids can be manipulated widely by the choice of coreactant raw materials (Table 1) (2). The reactivity fundamental to the majority of commercial resins is derived from maleic anhydride [108-31-6] (MAN) as the unsaturated component in the polymer, and styrene as the coreactant monomer. Propylene glycol [57-55-6] (PG) is the principal glycol used in most compositions, and (i9f2v (9)-phthahc anhydride (PA) is the principal dibasic acid incorporated to moderate the reactivity and performance of the final resins. 

Polysulfones also offer desirable properties for cookware appHcations, eg, microwave transparency and environmental resistance to most common detergents. Resistance to various sterilizing media (eg, steam, disinfectants, and gamma radiation) makes polysulfones the resin family of choice for many medical devices. Uses in the electrical and electronic industry include printed circuit boards, circuit breaker components, connectors, sockets, and business machine parts, to mention a few. The good clarity of PSF makes it attractive for food service and food processing uses. Examples of appHcations in this area include coffee decanters and automated dairy processing components. 

Resin Solubilizers. In general, water-soluble resins ate amine salts of acidic polymers. Water-soluble coatings formulated with AMP-95 and DMAMP-80 exhibit superior performance (15,16) (see Water-SOLUBLE polymers). AMP-95, used in conjunction with associative thickeners (17) or hydroxy-ethylceUulose, provides for the most efficient utilization of such thickeners. It also is the neutralizer of choice for use with hair spray resins. 

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