Solubility mastic

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. 

Mastic. Most commercial mastic [61789-92-2] is collected on the Greek island of Chios, near the Turkish coast. It is a soft resin with a softening point of 55°C. It has an acid number of 50—70 and a saponification number of 62—90. It is soluble in alcohols and aryl hydrocarbons. Mastic is used in wood coatings, lacquers, adhesives, and printing inks. 

Mastication of natural rubber with elastomers which do not give gel allows the synthesis of soluble graft or block copolymers, depending on the tendency for chain rupture and transfer reactions. 

Graft polymers were obtained by mastication of a 60/40 blend of natural rubber and chlorosulphonated polyethylene (/). From 10-55% natural rubber was obtained as side chains. Grafting presumably proceeds by transfer of chlorine atoms to the rubber radicals to give grafting sites for combination with rubber radicals. Soluble linear polymers were also obtained by mastication for 50-180 min under nitrogen for a blend 50/50 of natural rubber and a polyurethane rubber (Vulcaprene A) (/). 

Acrylonitrile monomer when masticated in the presence of polymer leads to the formation of pseudocrosslinked block copolymers by mechanical scission of soluble block copolymers. The aggregation of the polyacrylonitrile chains of the block copolymer fraction results in the formation of swollen gels when the polymerization products are extracted with solvents from the initial polymer (78-80). 

Fig. 25. Polymerization of acrylonitrile by poly(methyl methacrylate) mastication. Analysis of products at various extent of polymerization, i free poly(methyl methacrylate) 2 soluble block copolymer 3 chloroform-insoluble block copolymer gel (78)...

The mechanical degradation and production of macroradicals can also be performed by mastication of polymers brought into a rubbery state by admixture with monomer several monomer-polymer systems were examined (10, 11). This technique was for instance studied for the cold mastication of natural rubber or butadiene copolymers in the presence of a vinyl monomer (13, 31, 52). The polymerization of methyl methacrylate or styrene during the mastication of natural rubber has yielded copolymers which remain soluble up to complete polymerization vinyl acetate, which could not produce graft copolymers by the chain transfer technique, failed also in this mastication procedure. Block and graft copolymers were also prepared by cross-addition of the macroradicals generated by the cold milling and mastication of mixtures of various elastomers and polymers, such as natural rubber/polymethyl methacrylate (74), natural rubber/butadiene-styrene rubbers (76) and even phenol-formaldehyde resin/nitrile rubber (125). 

Ammonium polyphosphates, on the other hand, are relatively water insoluble, nonmelting solids with very high phosphorus contents (up to about 30%). There are several crystalline forms and the commercial products differ in molecular weights, particle sizes, solubilities, and so on. They are also widely used as components of intumescent paints and mastics where they function as the acid catalyst (i.e., by producing phosphoric acid upon decomposition). They are used in paints with pentaerythritol (or with a derivative of pentaerythritol) as the carbonific component and melamine as the spumific compound.22 In addition, the intumescent formulations typically contain resinous binders, pigments, and other fillers. These systems are highly efficient in flame-retarding hydroxy-lated polymers. 

The most important characteristics of butyl rubber are its low permeability to air and its thermal stability. These properties account for its major uses in inner tubes, tire inner liners, and tire curing bladders. Because of the poor compatibility of butyl with other rubbers (with respect to both solubility and cure), the halobutyls are preferred. The brominated p-methylstyrene-containing butyl rubbers are used in a number of grafting reactions for tire applications and adhesives. Other uses for butyl rubber are automotive mechanical parts (due to the high damping characteristics of butyl), mastics, and sealants.55... 

In the past, many or perhaps most publications on cellular solids in the nonfood literature were the result of interest in their performance at relatively small deformations (strains). In contrast, during their mastication, foods are subjected to very large compressive strains and are then tom apart. Moreover, in engineering and biomechanics applications, the solid foam is expected to be rather inert. Or, if it does interact with the environment, this would be a slow process that takes place on a time scale of months or years. In contrast, cellular foods interact with moisture very rapidly and the resulting changes can be quite unique, depending on the amount of water soluble components in their cell walls. 

If polymer A has a butadiene rubber block, it will not find application in pressure-sensitive adhesives. It is not readily tackified, it is not readily melt processable, and it will not close a box. However, if dissolved in solvent, compounded with filler and certain resins, it will make the world s best construction mastic, very capable of bonding drywall to wood, etc. If one wants to maximize the solids content in this mastic (use less solvent), and if one wants to design the SBS molecule to be soluble in more environmentally friendly solvents, then in what direction should one head If not A , then where in the region does one strike the balance for a highly extended but tough mastic that allows the solvents of choice while achieving maximum solids and a viscosity low enough to squeeze from a tube ... 

If two homopolymers are masticated together then terminal macro-radicals (-Mj ) and (-M2O are formed that can cross-terminate to give a block copolymer. In this case there will be a blend of two homopolymers as well, since formation of the cross-termination product will compete with recombination of the macro-radicals. There will also be incomplete chain scission of the homopolymers. This strategy has also been employed to produce compatibilization and enhanced interfacial adhesion of immiscible homopolymers since the block copolymer will be soluble in each phase and thus able to bridge the phase boundary. This and other topics concerning polymer blends are discussed in Section 1.3. 

Glycol diocetote is a colorless liquid having a foint odor resembling that of ethyl acetate. It will dissolve a wide range of cellulose esters, camphor, dammar, ester gum, elemi, mastic, rosin and sandarac. When it is mixed with active solvents its range of solubility is increased far a wide variety of cellulose esters and ethers and for natural and synthetic resins. 

Mastication of resins n. Process of hot working of resins, which is believed to reduce molecular complexity and to confer solubility. It has been used in natural copals, and advantages of this treatment are that thermal cracking is avoided and pale colors maintained. Patented methods include treatment between rotating rollers, sometimes in the presence of solvents. 

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