tailieunhanh - Rubber Compounding - Chemistry and Applications Part 10

Tham khảo tài liệu 'rubber compounding - chemistry and applications part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 9 Resins James E. Duddey Akron Ohio . I. INTRODUCTION Resins or in situ resins are considered to be polymeric materials with weightaverage molecular weights Mw in the approximate range of 800-4000. They are amorphous thermoplastic materials that can be either liquids low softening points or solids high softening points . They serve many functions in rubber compounds. In uncured rubbers they function as process aids softeners tackifiers pigment dispersing aids and homogenizing agents. In cured rubbers they function as plasticizers extenders and reinforcing agents. There are no definitive lines between process aids plasticizers softeners and tackifiers. Barlow 1 defined process aids as materials included in the rubber formulation to reduce the time and energy required to break down the polymer . peptizers or other materials that reduce the viscosity of the rubber mix. At the same time they can help improve the dispersion of dry materials produce smoother stocks improve the dispersion rate of fillers and in some instances increase the homogeneity of rubber blends 1 . The ASTM definition for a softener is a compound material used in a small proportion to soften a vulcanizate or facilitate processing or incorporation of fillers uncured compound . Tackifiers are specialized types of softeners that are used to increase the ability of uncured rubber formulations to form bonds with themselves or other surfaces under pressure by increasing the wettability or contact at the interface while maintaining or even increasing the green strength of the rubber formulation 2 . The ATSM definition of a plasticizer is a compounding material used to enhance the deformability of a polymeric compound. Copyright 2004 by Taylor Francis At processing temperatures softeners and plasticizers have the same function reducing viscosity and improving processing. Both materials are compatible with most rubbers. In the cured rubber plasticizers are materials that lower the glass transition .