甲基矽樹脂於不同溶劑中之流變行為研究

一般高分子聚合物溶液的流變行為多半呈現剪稀(shear-thinning)的現象，而大部分的高分子在溶液中的行為是以分子鏈或是硬球(hard sphere)觀點來解釋，另外也有剪稠(shear-thickening)現象的高分子溶液，其流變行為則是以膨脹體(dilatant)觀點來解釋，即在高剪切力下，由於高分子團體積變大而使溶液黏度升高，這在懸伏液、乳液等常見；但也有在低剪切力下，溶液具有剪稀的行為，而在高剪切力下卻成現剪稠的行為，在黏度對剪切力作圖時，會呈現出一個勾形曲線的圖形；流變行為的探討可應用在塗佈材料的分散技術上，以推測不同的高分子溶液對分散效果的影響。甲基矽樹脂(methyl silicone resin)一般是以二甲基二氯矽烷及三甲機氯矽烷兩種單體，以不同單體比例合成出不同特性的中低分子量的甲基矽樹脂，之後再以酸、鹼或有機金屬等做為催化劑，使樹脂近一步硬化形成具有耐熱、高硬度、潑水及防鏽功能的塗膜，一般被應用於耐熱、防火、防鏽塗料、電子元件的絕緣保護塗層及底材表面的潑水處理等。由於甲基矽樹脂由二官能度及三官能度兩種單體合成，因此理論上會呈現網狀與鏈狀兩種混合結構，溶解在溶劑中會呈現膠體軟球的狀態；研究中發現：矽樹脂溶解在不同溶劑中，黏度對剪切力作圖卻會有剪稀與剪稠兩種不同的流變行為表現，而且應用在塗料配方設計中，亦會造成不同的塗料流變性質。

關鍵字

流變行為；矽樹脂

並列摘要

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.