| Summary: | 碩士 === 國立臺北科技大學 === 有機高分子研究所 === 94 === The rheological character of a polymer often appears as shear-thinning. Most polymers behaviour in a solution can be explained by the polymer chain or hard sphere theory. Other than that, shear-thickening polymer solution also exists. Its behavior can be explained by dilatant theory, which suggests that the shear-thickening of the solution is due to the swelling of the polymer particles. This phenomenon often occurs in suspension or emulsion. Solution exhibits a mixed behavior can also be found whose behavior is such that shear-thinning occurs under low shear force and shear-thickening occurs under high shear force. Under this circumstance, the viscosity versus shear force graph exhibits a spoon shaped curve. The rheological study can be applied to the dispersion of paint which can predict the dispersion effect of various polymer materials in solution.
Commercial methyl silicone resins are general synthesized by various ratios of dichlorodimethylsilane and methyltrichlorosilane to form various middle-low molecular weight resin. Acid, alkaline, and organic metal compound are then used as catalysts to harden the resin, which transforms it to coatings with high hardness, thermal resistance, water repellence and rust proofing properties. The applications of such resin include (1) thermal, fire and rust proofing paint. (2) insulation paint for electronic components (3) primer with water repellant property.
Theoretically the structure of methyl silicone resin exhibits a mixture structure of network and chain as it consists of two-functional monomer and tri-functional monomer. A state of colloids soft-sphere appears if such resin is dissolved in solution. Studies have shown that silicon resin exhibits shear-thinning and shear-thickening properties depending on the type of solution used. It will also cause different rheological properties of coatings when the resin solutions applied to coatings formulas.
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