Melamine-formaldehyde (MF) resin with different hydroxymethylation degree was blended with polyvinyl alcohol ( PVA) solution and spun into MF/PVA blend fiber via wet spinning process. The compatibility of MF and PVA was observed by scanning electron microscopy. The nitrogen-loss rate of the blend fiber was analyzed during the spinning process by Kjeldahl method. The mechanical properties, fire retardancy, hot water retardancy and thermal stability of the fiber were characterized. The results showed that the hydroxymethylation degree of MF resin can be regulated by varying the proportion of melamine and formaldehyde; the nitrogen-loss rate of the blend fiber gradually decreased with the increase of the hydroxymethylation degree of MF resin; the nitrogen-loss rate of the blend fiber was 0.20% as the hydroxymethylation degree of MF resin was increased to 1. 15; after heat treating at 220℃, the fiber made from high-hydroxymethylation degree MF resin had the breaking strength 3. 19 cN/dtex, elongation at break 25. 1% , limit oxygen index 33.2% , softening point in water 86℃, initial thermal decomposition temperature 258.8℃ in nitrogen atmosphere and carbon residue rate 24.63% at 600℃.%采用不同羟甲基化度的三聚氰胺甲醛(MF)树脂与聚乙烯醇(PVA)溶液共混湿法纺丝,制备MF/PVA共混纤维；借助扫描电子显微镜研究了MF与PVA的相容性,凯氏定氮法分析了共混纤维在纺丝过程中氮流失率,并对纤维的力学性能、阻燃性能、耐热水性能及热稳定性进行了测试表征.结果表明:改变甲醛与三聚氰胺的比例可以获得不同羟甲基化度的MF树脂；随着MF树脂羟甲基化度的提高,共混纤维的氮流失率逐渐降低；当MF树脂的羟甲基化度增大至1.15时,共混纤维氮流失率为0.20％；高羟甲基化度MF制成的共混纤维经220℃处理后,断裂强度和断裂伸长率分别为3.19 cN/dtex和25.1％,极限氧指数为33.2％,水中软化点为86℃,在氮气氛围下的初始热分解温度为258.8℃,600℃时残炭量为24.63％.
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