Brittleness mastic

A relatively new development which promises to gain in importance in the future is the modification of asphalt by butadiene-styrene block polymers.44 The block polymers help reduce the low temperature brittleness and impart resistance to flow at elevated temperatures. Applications in mastics, automobile body undercoatings and waterproofing materials such as high quality roofing membranes are envisaged. 

We can determine what features of the chewing sequence influence assessment of particular textural characteristics of food by using this approach to examine the interaction between food and consumer during the mastication process. We should then be able to develop mathematical models for perception of textural qualities which take into account different texture combinations (for example, assessment of hardness in both elastic and brittle foods), and different breakdown patterns. Although currently at an early stage, mastication analysis shows promise for enhancing our measurement of perceived texture in foods. 

Brittleness—the force with which the material fractures. This is related to hardness and cohesiveness. In brittle materials, cohesiveness is low, and hardness can be either low or high. Brittle materials often create sound effects when masticated (e.g., toast, carrots, celery). 

Light yellow, brittle, elongated tears translucent with vitreous fracture crumbles 10 powder when masticated. Insol in water, benzene, petr ether. Sol in alcohol, ether, acetone, hot caustic alkalies partially sol in chloroform, volatile oils, oil turpentine, carbon disulfide. 

Only atactic or amorphous poly(vinyl acetate) is currently commercially available. It has a glass transition temperature, Tg, of 29°C. Consequently, the polymer becomes sticky at temperatures slightly above ambient. The low-molecular polymers, which are normally brittle, become gumlike when masticated (used in chewing gums). Its adhesive strength is dictated by its water sensitivity. 

Rosin family s most common form of adhesive is colophony, a hard amorphous substance derived from the oleoresin of the pine tree. This material is applied in solvent solution form as a hot-melt mastic. It has poor resistance to water, is subject to oxidation, and has poor aging properties. Plasticizers are usually added to reduce its brittleness. Bond strengths are moderate and develop rapidly. These materials are used as temporary adhesives in bonding paper and as label varnishes. They are also used as components of PSAs based on styrene-butadiene copolymers and in hot-melt adhesives and tackifiers. These materials have been largely replaced by synthetic-resin adhesives. One specialized form of rosin adhesive is Canada Balsam, covered by the obsolete Military Specification MIL-C-3469C, titled Canada Balsam. This material was intended for cementing optical elements. 

Shellacs are thermoplastic resins derived from insects. They are used in alcoholic solutions or as hot-melt mastics. They have good electrical insulating properties, but are brittle imless compounded with other materials. 

In one process, natural rubber is milled with a metal soap (e.g., cobalt linoleate) and then masticated in an internal mixer at 80°C in the presence of wood flour (which acts as a surface catalyst for oxidation). The mixture is then extracted with benzene and the solvent is removed by distillation to yield the oxidized rubber as a brittle brown solid. 

Feller, R. L. (1958). Dammar and mastic varnishes hardness, brittleness, and change in weight... 

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