木虫 (小有名气)
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【答案】应助回帖
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With the rapid development of LED lighting technology, the LED flexible light band, as a kind of energy-saving and environment-protecting high efficiency lighting products, has been widely used in home lighting, commercial lighting and urban landscape, and other fields. However, as a new type of lighting products, it puts forward high requirements for the packaging materials due to the particularity of its application fields, i.e. good mechanics performance, flexural toughness, weatherability, transparency and fire retardancy, etc. Polyurethane, which has strong adhesion, good performance at high and low temperature and good mechanical properties, is the ideal choice for LED flexible light outdoor encapsulation, but it still has the problem of poor weather resistance and flame retardancy. This paper describes the synthesis of halogen-free and flame retardant bi-component polyurethane for LED, and its properties have been characterized. The main research contents and conclusions were as follows: (1) the transparent two-component polyurethane was synthesized with the semi prepolymer method, and the synthesis process and performance of the polyurethane were studied. The polyurethane prepolymer was synthesized with 4, 4 '- dicyclohexyl methane diisocyanate (H12MDI), polyether polyols (N210) and Polycaprolactone polyol (PCL210) as the raw materials, and its viscosity was determined. The results show that isocyanate index R of the prepolymer is 4, and the viscosity of the prepolymer is 3908 mPa•s after 1 h reaction at 50 ℃ and then 2 h reaction at 80 ℃, which is suitable for the synthesis of two-component polyurethane. The effects of catalyst types, curing temperature, curing time and polyols kinds/ratio on the mechanical and optical properties of the polyurethane in the curing process were investigated. The results show that the polyurethane has good mechanical, optical and hydrolysis-resistance performances with a catalyst (TK233), N210 and N3050, etc. as the raw materials, and after 3 days of room temperature curing. (2) The composite flame retardant containing silicon, phosphorus and nitrogen was synthesized by using the method of hydrolytic condensation , and its performance was characterized. The composite flame retardant was synthesized with gamma-aminopropyl triethoxy silane (KH550), N- (β aminoethyl) - γ - aminopropyl triethoxysilane (KH792) and phosphoric acid as the raw materias, and its performance was characterized. The results show that the flame retardant can effectively combine the three elements of silicon, phosphorus and nitrogen together, and has higher thermogravimetric residues and micron size after combustion. (3) The two-component flame retardant polyurethane was synthesized with the semi prepolymer method, and its its performance was characterized. The flame retardant, pentaerythritol, magnesium stearate, stearic acid, talcum powder and other additives were mixed and added to polyurethane, and its flame retardant performance was examined. The results show that the flame retardant performance is the best when the ratio of the amount of ammonium phosphate to that of pentaerythritol in the flame retardant is 3 : 1, and the amount of Si is 3, 4 and 2 times of magnesium stearate, stearic acid and talcum powder, respectively, and the mechanism was studied. |
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