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[塑料] 塑料阻燃深度总结(八)无机氢氧化物阻燃剂

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发表于 2013-10-20 09:23:03 | 显示全部楼层 |阅读模式
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本帖最后由 846082533 于 2015-12-31 14:59 编辑 <br /><br />
1.3.2.4 无机氢氧化物阻燃剂
41Inorganic hydroxides or mixed hydroxide – inorganic salts that can release water upon heating above 200?C can be used as flame retardants in many types of polymers. The two most commonly used products are aluminum hydroxide (ATH) and magnesium hydroxide (MH). In fact, ATH is, by weight, the largest commercially manufactured flame retardant, its main use being in wire and cable insulation and other elastomeric products, synthetic marble and synthetic onyx, latex for carpet back-coatings, phenolics, epoxies, and unsaturated polyesters.
在高于200℃时,无机氢氧化物或碱类与无机盐的混合物可发生脱水反应,二者可作为多种聚合物的阻燃剂使用。该类阻燃剂中,最常用的是氢氧化铝(ATH)和氢氧化镁(MH)。目前ATH是产量最大的阻燃剂之一,主要用于电线电缆的绝缘层、弹性体产品、人造大理石和玛瑙、地毯背面乳胶涂料、酚醛树脂、环氧树脂及不饱和聚酯。
42ATH begins to release water at about 220?C with an endotherm of 1.17 kJ/g, whereas MH starts releasing water at about 330?C with an endotherm of 1.356 kJ/g. Thermogravimetric and differential scanning calorimetry curves obtained on heating of ATH and MH are shown in Figures 1.2 and 1.3, respectively. There is little doubt that the main mechanism of fire retardant action of these hydroxides is heat absorption and dilution of the flame with water vapors. Another mechanism could be the catalytic effect of anhydrous alumina, which will help acid-catalyzed dehydration of some polymers and as a result can enhance charring. Since both anhydrous alumina and magnesia are white highly refractory powders, they provide heat insulation by reflecting heat when they accumulate on a surface.

研究表明,ATH和MH分别在220℃和330℃左右时脱水,吸热量分别为1.17 kJ/g和1.356 kJ/g。图1.2和1.3分别为升温时ATH和MH的热失重曲线与差示扫描量热曲线。据研究,无机氢氧化物的阻燃作用机理不仅有脱水吸热及水蒸气的隔热与稀释效应,还可催化一些聚合物发生酸化脱水而有助于成炭。因为无水氧化铝与氧化镁粉体的耐火性极佳,故当积聚于聚合物表面时,二者也可以发挥隔热层的作用。
43ATH and MH are used primarily in wire and cables in poly(vinyl chloride) (PVC), polyethylene, and various elastomers. There is also some limited application of MH in polyamide-6. To pass flame retardancy tests, 35 to 65 wt% of metal hydroxide is required. Decreasing the loading of metal hydroxides will result in a significant gain in physical properties, especially low-temperature flexibility; therefore, combinations with red phosphorus, silicones, boron compounds, nanoclays (treated montmorillonites), and charring agents have been explored. Surface treatment of metal hydroxides also helps to improve physical properties and sometimes improves flame retardancy, due to better dispersion.

现在ATH与MH主要应用于PVC、PE和弹性体制成的电线电缆材料,MH在PA66中也有少量的应用。为通过阻燃性测试,金属氢氧化物的添加量需达到35%-65%。降低金属氢氧化物的添加量可有效改善聚合物的物理性能,尤其是低温时的韧性;因此,人们正在研究无机氢氧化物与红磷、硅化合物、硼化合物、纳米粘土(改性蒙脱土)、成炭剂的复配使用。对金属氢氧化物表面改性可助于改善物理性能,有时候也能促进良好分散而可提高阻燃效率。 [size=+0][size=+0][size=+0]


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