Synthetic resin types

The medium is the binder which provides for the adhesion of pigments. The most important types are the temper media (glue, egg, and gum), the oils, and wax. In addition, for wall painting there is the tme fresco technique, where the pigments are laid down in a fresh, wet plaster preparation layer. Several other media have been used, but much less frequendy, eg, casein temper. In modem paints, a number of synthetic resins are used for this purpose. Contemporary artist paints are often based on acryhc polymers (see Acrylic ester polymers Paints). 

A varnish is often appHed on top of the paint layers. A varnish serves two purposes as a protective coating and also for an optical effect that enriches the colors of the painting. A traditional varnish consists of a natural plant resin dissolved or fused in a Hquid for appHcation to the surface (see Resins, natural). There are two types of varnish resins hard ones, the most important of which is copal, and soft ones, notably dammar and mastic. The hard resins are fossil, and to convert these to a fluid state, they are fused in oil at high temperature. The soft resins dissolve in organic solvents, eg, turpentine. The natural resin varnishes discolor over time and also become less soluble, making removal in case of failure more difficult (see Paint and FINNISH removers). Thus the use of more stable synthetic resins, such as certain methacrylates and cycHc ketone resins, has become quite common, especially in conservation practice. 

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.). 

Synthetic resins are extensively used, e.g., in surface finishes, in the fabrication and repair of boat and motor vehicle bodies, in the manufacture of laminated boards, for electrical components, in pattern making and in paints and varnishes. Non-rubber adhesives made from fish glues and from cotton derivatives (e.g. cellulose acetate) tend not to be sensitizing but, depending upon composition and the manner of use, many other types may pose significant dermatitic and fume hazards. 

Resins can be divided into natural and synthetic types. Natural resins have a vegetable or animal origin. Typical examples are rosins. Synthetic resins result from controlled chemical reactions, and can be divided into two subgroups. 

Synthetic resins form the heart of the paint industry. The tw o main types of synthetic resins are condensation polymers and addition polymers. Condensation polymers, formed by condensation of like or unlike molecules into a new, more complex compound, include polyesters, phenolics.. iniino resins, polyurethane, and epoxies. Addition polymers include polyvinyl acetate, polyvinyl chloride, and the acrylates,... 

Certain types of adsorption media have been shown to preferentially adsorb certain contaminants. For example, research has shown that, in some cases, coconut shell-based GAC removes MTBE better than typical coal-based GAC. In addition, synthetic resins have been developed to preferentially adsorb some oxygenates, such as TBA, that are less absorbable by GAC. Often, adsorption processes also take advantage of the biodegradability of MTBE and other oxygenates by promoting bacterial growth on the adsorption. 

The principal field of application for synthetic polymers as art materials is that of paint binders, which developed in the second half of the twentieth century when manufacturers of artists paints and varnishes realized the potential of synthetic resins used in the decorative household and industrial paint market [81]. The most important families of synthetic artists paints are the acrylics, the vinyl acetate resins, and the alkyds, and Py-GC/MS has been used to identify all these types of modem paints. 

In general, the acid-sorbing resins may be classified as high molecular weight polyamines or polyimines. Thus, the original Adams and Holmes material was a polymer of m-phenylenediamine. Cation Exchange materials include synthetic resins, such as sulfonated phenol-formaldehyde or polystyrene types, and sulfonated coal. Some manufacturers have a variety of sub-types which are considered superior for particular applications. 

P.R.242 is an equally valuable product for paints, especially for various types of industrial paints. It is also recommended for use in automotive finishes. Both lightfastness and weatherfastness are excellent, but do not quite reach the levels of the appreciably yellower anthanthrone P.R.168. P.R.242 is fast to overcoating and heat stable above 180°C. It is also employed in emulsion paints based on synthetic resin. 

P.Y.108 is applied in various types of industrial finishes, especially in original automotive (O.E.M) and in automotive refinishes. It is also recommended for metallic finishes, although it is much less weatherfast in such systems. The pigment tends to seed, i.e., it forms specks upon storage. The mechanism behind this phenomenon remains to be elucidated. Besides, P.Y.108 also lends color to emulsion paints, in which it is durable enough to satisfy the requirements for exterior paints based on synthetic resin dispersions. It is also fast to acids, alkali, and plaster. 

The technical uses of phenol are important, particularly in the manufacture of salicylic add (Chap. VI. 4, p. 249), and in that of the valuable synthetic resins of the bakelite type (condensation with formaldehyde). Under mild conditions phenol may be caused to combine with formaldehyde giving p-hydroxybenzyl alcohol ... 

Attempts to utilize sucrose in synthetic resins have had no great success. The position has recently been summarized by Long in an article Sugar and Sugar By-Products in the Plastics Industry. As far as the author is aware the only other possible use of sucrose as such is in solution as a lubricant for certain types of machinery used in the sugar industry, for example in rotary pumps and stirring apparatus. 

Formalin is an aqueous solution of approximately 40% formaldehyde. It was traditionally used to preserve biologic specimens, but its identification as a mild carcinogen has curtailed its use as a preservative. Formaldehyde is widely used to produce synthetic resins. Resins are sticky, liquid organic compounds that are insoluble in water. They often harden when exposed to air. Many commercial types of glue are resins. Natural resins are produced by plants as a response to damage. When a plant suffers external damage, natural resins flow to the area and harden to protect the underlying... 

ION EXCLUSION. The process in which a synthetic resin of ihc ion exchange type absorbs nonionized solutes such as glycerine or sugar while it docs not absorb inni/etl solutes that are also present in a solution in contact with the resin. Thus, sodium chloride and glycerine can he separated by passage of their aqueous solution through a bed of particles of an inn exclusion resin. 

Coumarone Indene Resins, These are thermoplastic resins of relatively low mw, varying from fairly viscous liqs to hard resins. Their color varies from pale yel to nearly black. They are obtd by heating mixts of coumarone indene with H2SC>4 so as to cause polymerization. Coumarone indene resins are one of the oldest types of synthetic resins, having been produced in Germany as early as 1900. The manuf props are described in Ref 2... 

Heat-Sensitive or Thermoplastic Adhesive-Based Labels Activated by Heat. Two types are in use, instant tack and delayed tack. Both are based on synthetic resins. The former has to have heat and pressure applied to effect the transfer, but sets immediately after the source heat is removed. 

Organic Extenders. Organic extenders are primarily of two types (1) fillers derived from organic materials and (2) low-cost, naturally occurring or synthetic resins. Of the first type, wood flour, shell flour, and other cellulosic fillers are the most common. They also provide a margin of mechanical property reinforcement because of their relatively high aspect ratio. Of the resinous types these are petroleum-based derivatives as well as soluble lignin and scrap synthetic resins. 

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