TAILIEUCHUNG - Handbook of Plastics Technologies Part 8

Tham khảo tài liệu 'handbook of plastics technologies part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ELASTOMERS ELASTOMERS Particle Size nm NonReinforcing SemiReinforcing 5000 2000 1000 500 Reinforcing 200 100 50 20 10 Barium Sulfate Magnesium Silicate Dry-Ground Calcium Carbonate Pricipitated Calcium Carbonate Aluminum Silicate Calcium Silicate Pricipitated Silica Fumed Silica Wet-Ground Calcium carbonate Soft Clay Hard Clay N990 N765 N650 Carbon Blacks N550 N330 N220 N110 FIGURE Types of fillers. Large Particles. Low Surface Area. High Structure High DBP Absorption Small Particles. High Surface Area High Structure High DBP Absorption Large Particles. Low Surface Area. Low Structure Low DBP Absorption FIGURE Particle size and structure. Small Particles. High Surface Area Low Structure Low DBP Absorption Downloaded from Digital Engineering Library @ McGraw-Hill Copyright 2006 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. ELASTOMERS CHAPTER 4 High-structure fillers give rise to reduced elasticity in the uncured state. Unfilled elastomers when extruded in the uncured state . during processing expand or swell when they leave the extruder die have memory or nerve . Along with this die swell is a shortening of the extruded profile. It is called extrusion shrinkage. Extrusion shrinkage is greatly reduced by fillers especially those of high structure. Also as the structure of the filler increases the viscosity of the uncured composition or the stiffness of the vulcanizate increases. This is because the higher-structure fillers immobilize more of the elastomer during its straining in either the cured or uncured state. The amount of structure is measured by using the dibutyl phthalate DBP absorption method. Small amounts of DBP a nonvolatile liquid are added to dry filler until a noncrumbling paste is obtained. The DBP absorption is expressed in ml of DBP per 100 g filler. Filler Surface Activity. A filler can have high surface area and high structure

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