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分别以聚乙烯醇缩丁醛（PVB）、聚丙烯酸酯乳液共聚物（PMBM）和聚苯乙烯（PS）为改性剂，研究了不同改性剂对脲醛树脂模塑料尺寸稳定性、力学性能及热稳定性能的影响；采用动态力学机械分析（ DMA）和电镜扫描（ SEM）分别研究了改性前后模塑料动态力学性能和冲击断面的微观结构。结果表明：当改性剂PVB、PMBM、PS添加量分别为20％、20％、10％时，各改性剂改性的模塑料尺寸稳定性最好；PVB添加量为20％时，模塑料冲击强度为2．55 kJ／m2，弯曲强度为88．3 MPa，分别比纯模塑料提高了49．1％和63．2％；PMBM改性的模塑料耐低温性能较好，PVB改性的模塑料耐高温性能较好；由DMA测试结果可知，PVB和PMBM对模塑料增韧的改性效果显著，且与脲醛树脂的相容性较好，PS无增韧效果。此外，由SEM微观结构分析可知：PVB和PMBM改性的模塑料断面粗糙，断口光滑，趋于韧性断裂；而PS改性的模塑料为脆性断裂。“,”The effects of modifiers polyvinyl butyral, polyacrylate and polystyrene on size stability, mechanical properties and thermal stability of moulding compound were investigated, and the dynamic mechanical properties and mi?crostructure of fracture surface of modified systems were studied with dynamic mechanical analysis ( DMA) and scanning electron microscope ( SEM) . The results showed that moulding plastic had the best dimension stability when polyvinyl butyral, polyacrylate and polystyrene were added 20%, 20% and 10%, respectively. The impact strength and bending strength of urea?formaldehyde resin molding plastic modified with 20% polyvinyl butyral were 2.55 kJ/m2 and 88.3 MPa respectively, and increased by 49.1% and 63.2% comparing with unmodified compound. Polyacrylate could improve the low temperature resistance of molding compound, and moulding compound modified with polyvinyl butyral had good high?temperature performance;The DMA test results showed that polyvinyl butyral and polyacrylate had the toughening effects on the moulding compound, and the compatibility with urea?formaldehyde resin was better. The moulding compound modi?fied with polystyrene could not be toughened. In addition, fracture surface of moulding compound modified with polyvinyl butyral and polyacrylate appeared gliding fracture and the compound modified with polystyrene appeared brittle fracture.