Other Resins

Thermoplastic resins are generally reinforced with short fibres (for use with injection moulding and not considered in this book), with long fibres (thermoplastic sheet compound, Chapter 5) or with glass mat (i.e. glass mat thermoplastics or GMT). Polypropylene is the resin most used as the matrix for GMT and the reinforcement is usually a random mat, primarily chopped strand but it may be continuous filament or needled mat. 

These materials compete with sheet moulding compounds (SMC) for applications which are generally of high volume (section 11.4). Compared with SMC (Table 11.11) they have a lower modulus, and a higher failure strain. 

These materials have only recently become available in Europe and development work is still under way to develop suitable glass sizings and reduce the melt viscosity (by adding a small amount of plasticizer to the resin). Unlike SMC, these materials have so far only been used for semi-structural applications, primarily motor vehicles. 

Reinforcements for polypropylene technology developments. Reinforced Plastics, March 1992, 18-21. 

Macrocyclic groups have been incorporated into resins to impart a different selectivity for metal cations than is possible with ordinary cation-exchange resins. 

Application of macrocyclic ligands to ion chromatography has been discussed [46]. A practical column was created by absorbing tetradecyl-18-crown-6, which is a macrocycle with a long hydrophobic tail, onto a polystyrene-divinylbenzene substrate. When packed into a column, the macrocycle remains adsorbed to the resin [46]. 

Exactly the same elution order was observed for these same ions with the TD18C6 column [47]. 

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Extmsion of polyethylene and some polypropylenes is usually through a circular die into a tubular form, which is cut and collapsed into flat film. Extmsion through a linear slot onto chilled rollers is called casting and is often used for polypropylene, polyester, and other resins. Cast, as well as some blown, films may be further heated and stretched in the machine or in transverse directions to orient the polymer within the film and improve physical properties such as tensile strength, stiffness, and low temperature resistance. 

PhenoHc-based resins have almost disappeared. A few other resin types are available commercially but have not made a significant impact. Inorganic materials retain importance in a number of areas where synthetic organic ion-exchange resins are not normally used. Only the latter are discussed here. This article places emphasis on the styrenic and acryHc resins that are made as small beads. Other forms of synthetic ion-exchange materials such as membranes, papers, fibers (qv), foams (qv), and Hquid extractants are not included (see Extraction, liquid-liquid Membrane technology Paper.). 

PTFE is outstanding in this group. In thin films it provides the lowest coefficient of friction (0.03—0.1) of any polymer, is effective from —200 to 250°C, and is generally unreactive chemically. The low friction is attributed to the smooth molecular profile of PTFE chains which allows easy sliding (57). Typical apphcations include chemical and food processing equipment, electrical components, and as a component to provide improved friction and wear in other resin systems. 

The plasticization of PVC accounts for the vast majority of plasticizer sales. However, significant amounts of plasticizers are used in non-PVC polymers and this may become increasingly important in the future. Although PVC stands alone in its abiUty to accept and retain large quantities of commercial plasticizer, effective plasticization of other resins using slightly modified plasticizers may be possible if certain conditions specific to the polymer of interest are met. 

Although blending with other coating resins provides a variety of ways to improve the performance of alkyds, or of the other resins, chemically combining the desired modifier into the alkyd stmcture eliminates compatibiUty problems and gives a more uniform product. Several such chemical modifications of the alkyd resins have gained commercial importance. 

Amino resins are also often used for the cure of other resins such as alkyds and reactive acryUc polymers. These polymer systems may contain 5—50% of the amino resin and are commonly used in the flexible backings found on carpets and draperies, as well as in protective surface coatings, particularly the durable baked enamels of appHances, automobiles, etc. 

The future for amino resins and plastics seems secure because they can provide quaHties that are not easily obtained in other ways. New developments will probably be in the areas of more highly specialized materials for treating textiles, paper, etc, and for use with other resins in the formulation of surface coatings, where a small amount of an amino resin can significantly increase the value of a more basic material. Additionally, since amino resins contain a large proportion of nitrogen, a widely abundant element, they may be in a better position to compete with other plastics as raw materials based on carbon compounds become more costly. 

Aniline—formaldehyde resins were once quite important because of their excellent electrical properties, but their markets have been taken over by newer thermoplastic materials. Nevertheless, some aniline resins are stiU. used as modifiers for other resins. Acrylamide (qv) occupies a unique position in the amino resins field since it not only contains a formaldehyde reactive site, but also a polymerizable double bond. Thus it forms a bridge between the formaldehyde condensation polymers and the versatile vinyl polymers and copolymers. 

Other Materials. Benzoguanamine and acetoguanamine may be used in place of melamine to achieve greater solubiHty in organic solvents and greater chemical resistance. Aniline and toluenesulfonamide react with formaldehyde to form thermoplastic resins. They are not used alone, but rather as plasticizers (qv) for other resins including melamine and urea—formaldehyde. The plasticizer may be made separately or formed in situ during preparation of the primary resin. 

Other Resins. Some resins that were important in earlier years have decreased in commercial significance because of scarcity and increased cost of collection. They are Hsted for the historical record. 

Naphthalene sodium prepared in dimethyl ether or another appropriate solvent, or metallic sodium dissolved in Hquid ammonia or dimethyl sulfoxide, is used to treat polyfluorocarbon and other resins to promote adhesion (138—140). Sodium, usually in dispersed form, is used to desulfurize a variety of hydrocarbon stocks (141). The process is most useful for removal of small amounts of sulfur remaining after hydrodesulfurization. 

Speciali2ed copolymer latices, which are inherently and permanently tacky, are available as pressure-sensitive emulsions. They are mechanically stable and have excellent machinabiUty. They are compatible with many other PVAc latices and, therefore, can be easily blended with other resins for modification of surface tack, peel strength, and creep. 

It is not tme either that vinyl is the problem in municipal recycling because it contaminates other resins. Contamination occurs whether or not vinyl is present. Other resins are just as much a contamination problem as vinyl. Except for commingled plastics apphcations, different plastic materials caimot be mixed successfiJly in most recycled products apphcations. This is why it is cmcial to separate efficientiy one plastic from another. Because of the chlorine that is present in it, vinyl lends itself very weU to automated sorting technology. 

Synthetic resins, such as phenoHc and cresyUc resins (see Phenolic resins), are the most commonly used friction material binders, and are usually modified with drying oils, elastomer, cardanol [37330-39-5] an epoxy, phosphoms- or boron-based compounds, or even combinations of two. They ate prepared by the addition of the appropriate phenol and formaldehyde [50-00-0] in the presence of an acidic or basic catalyst. Polymerization takes place at elevated temperatures. Other resin systems are based on elastomers (see Elastomers, synthetic), drying oils, or combinations of the above or other polymers. 

Table 4 lists plastics consumed in building and constmction vs total U.S. plastics consumption for 1990. There was more PVC consumed in the building and constmction sector than any other resin type. 

Epoxy Resins. Epoxy resins (qv) are used to cross-link other resins with amine, hydroxyl, and carboxyHc acid (or anhydride) groups. The epoxy group, properly called an oxkane, is a cycHc three-membered ether group. By far the most widely used epoxy resins in coatings are bisphenol A (BPA) (4,4 -(l-methylethyHdene)bisphenol) [80-05-7] epoxy resins. 

Other Coatings Resins. A wide variety of other resin types are used in coatings. PhenoHc resins, ie, resins based on reaction of phenols and formaldehyde, have been used in coatings for many years. Use has been declining but there are stUl significant appHcations, particularly with epoxy resins in interior can coatings. 

The compositions of sheet and shape waxes are also trade secrets. However, they are blends of various proportions of paraffin, microcrystalline waxes, camauba wax, ceresin, beeswax, gum dammar, mastic gum, and possibly other resins. Sheet waxes are marketed in square sheets approximately 80 by 90 mm. Various thicknesses are available from 32 gauge (0.5 mm) to 14 gauge (1.63 mm). 

Worldwide sales of poly(phenylene ether)—styrene resin alloys are 100,000—160,000 t/yr (47,96) aimual growth rates are ca 9%. Other resin, particularly acrylonitrile—butadiene—styrene (ABS) polymers and blends of these resins with PC resins, compete for similar appHcations. 

Engineering resins can be combined with either other engineering resins or commodity resins. Some commercially successhil blends of engineering resins with other engineering resins include poly(butylene terephthalate)—poly(ethylene terephthalate), polycarbonate—poly(butylene terephthalate), polycarbonate—poly(ethylene terephthalate), polysulfone—poly (ethylene terephthalate), and poly(phenylene oxide)—nylon. Commercial blends of engineering resins with other resins include modified poly(butylene terephthalate), polycarbonate—ABS, polycarbonate—styrene maleic anhydride, poly(phenylene oxide)—polystyrene, and nylon—polyethylene. 

The forecasts made in 1985 (77) of 8—8.5% worldwide aimual growth have not materialized. The 2 x lOg + /yr engineering plastic production reported for 1985—1986 has remained fairly constant. Whereas some resins such as PET, nylon-6, and nylon-6,6 have continued to experience growth, other resins such as poly(phenylene oxide) have experienced downturns. This is due to successhil inroads from traditional materials (wood, glass, ceramics, and metals) which are experiencing a rebound in appHcations driven by new technology and antiplastics environmental concerns. Also, recycling is likely to impact production of all plastics. 

The higher molecular-weight soHd epoxy resins are used in formulations that usually consist of a resin, hardener, reinforcing filler, pigments, flow control agents, and other modifiers. In addition to using conventional hardeners in these formulations, epoxy resins can also be hardened with other resins, ie, acryhcs or polyesters. 

It has been seen that this resin has also some important advantages over the other resins in the literature like high total ion exchange capacity, easy synthesis, lower cost, simple regeneration. Furthermore, very good sepai ations were obtained using a concentration gradient of elution. In these elutions, very low concentrations of sodium trimetaphosphate were used. As a result, the resin synthesized can be used as an adsorbent for the effective removal of Pb, Cd, Co, Cu, Fe, Ni, Zn and Cr from aqueous solutions. 

This includes inorganic materials such as glass fibre and mica impregnated or glued together with epoxy, polyesterimide, polyurethane or other resins having superior thermal stability. 

For many years atactic polypropylene was an unwanted by-product but today it finds use in a number of markets and is specially made for these purposes rather than being a by-product. In Europe the main use has been in conjuction with bitumen as coating compounds for roofing materials, for sealing strips where it confers improved aging properties and in road construction where it improves the stability of asphalt surfaces. Less important in Europe but more important in USA is its use for paper laminating for which low-viscosity polymers are used, often in conjunction with other resins. Limestone/atactic... 

In addition to the resins based on bis-phenol A dealt with in preceding sections there are now available a number of other resins containing epoxide groups. These can be treated in two main groups ... 

Secondly, whereas 26-30% chlorine is required to make the resin effectively fire retardant, only 13-15% of bromine is required. It is therfore possible to achieve a greater flexibility in formulation with the bromine resins, which may be blended with other resins and yet remain effectively fire retardant. 

For a number of purposes the unmodified epoxide resins may be considered to have certain disadvantages. These disadvantages include high viscosity, high cost and too great a rigidity for specific applications. The resins are therefore often modified by incorporation of diluents, fillers, and flexibilisers and sometimes, particularly for surface coating applications, blended with other resins. 

Nitrile rubber is compatible with phenol-formaldehyde resins, resorcinol-formaldehyde resins, vinyl chloride resins, alkyd resins, coumarone-indene resins, chlorinated rubber, epoxies and other resins, forming compositions which can be cured providing excellent adhesives of high strength, high oil resistance and high resilience. On the other hand, NBR adhesives are compatible with polar adherends such as fibres, textiles, paper and wood. Specific formulations of NBR adhesives can be found in [12]. 

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