【作者】 禹海洋；

【导师】 张勇；

【作者基本信息】 上海交通大学 ， 材料学， 2009， 博士

【摘要】 作为我国特有的尼龙品种,尼龙1010具有很好的耐磨性、自润滑性以及低温性能等诸多优点,但尼龙1010的冲击强度对缺口比较敏感,其缺口冲击强度较低。本论文选用乙烯-醋酸乙烯酯共聚物(EVA)以及合适的增容剂,通过熔融共混的方法成功制备了高抗冲尼龙1010材料,系统研究了相关的增韧机理,采用粒子间距模型揭示了共混物结构-性能之间的联系。首先,研究了一种醋酸乙烯酯(VA)含量为40 wt%的乙烯-醋酸乙烯酯橡胶(EVM 400)对尼龙1010的增韧效果。尼龙1010/EVM 400共混物的缺口冲击强度随EVM 400用量的增加而提高,在EVM 400用量由40 ph(rper hundred nylon 1010)增加到80 phr时,尼龙1010/EVM 400共混物的缺口冲击强度从22.8 kJ/m2骤增到62.3 kJ/m2,发生脆韧转变。马来酸酐接枝乙烯-醋酸乙烯酯共聚物(EVA-g-MAH)能显著提高尼龙1010/EVM 400(100/20)共混物的缺口冲击强度,相应共混物在EVA-g-MAH用量由2.5 phr增加到5 phr时发生脆韧转变,缺口冲击强度由19.3 kJ/m2升高到57.8 kJ/m2。扫描电镜表明EVA-g-MAH能有效改善EVM 400在尼龙1010中的分布,分散相粒径随EVA-g-MAH用量增加而显著降低。对共混物断裂形貌分析的结果表明尼龙1010基体的剪切屈服是冲击过程中能量吸收的主要形式,是增韧的主要机理。尼龙1010/EVM 400和尼龙1010/EVM 400/EVA-g-MAH共混物发生脆韧转变的临界粒子间距约为0.2μm,当粒子间距低于该值时,共混物表现为韧性断裂。接着,将所用抗冲改性剂扩展到一系列具有不同VA含量以及门尼粘度的EVA,通过熔融共混制备了各种尼龙1010/EVA/EVA-g-MAH(80/15/5)共混物。在门尼粘度相对较低的情况下,VA含量在28～60 wt%的EVA能显著提高尼龙1010的缺口冲击强度。EVA中VA含量对尼龙1010/EVA/EVA-g-MAH(80/15/5)共混物缺口冲击强度的影响与EVA的玻璃化转变温度(Tg)和结晶度有关。在VA含量相同的情况下,高门尼粘度EVA在尼龙1010基体中更容易发生聚集,对尼龙1010的增韧效果低于相应的低门尼粘度EVA。尼龙1010/EVA/EVA-g-MAH(80/15/5)共混物的缺口冲击强度与粒子间距间的关系基本符合粒子间距模型。将增韧尼龙1010所用抗冲改性剂的种类进一步扩展到不同弹性体,比较不同弹性体对尼龙1010的增韧效果。选用乙烯-辛烯共聚物(POE)、苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)和EVM三种不同弹性体以及相应的马来酸酐接枝弹性体(POE-g-MAH、SEBS-g-MAH和EVA-g-MAH)作为增容剂与尼龙1010熔融共混,制备了不同的尼龙1010/弹性体/马来酸酐接枝弹性体共混物。在未使用马来酸酐接枝弹性体的情况下,三种弹性体中EVM对尼龙1010的增韧效果最好,相应共混物的缺口冲击强度最高。在所有弹性体增韧尼龙1010的共混物中,尼龙1010//SEBS-g-MAH(80/20)共混物则在室温下具有最高的缺口冲击强度,尼龙1010/POE-g-MAH(80/20)共混物的低温韧性最好。采用修正的断裂有用功(EWF)模型,通过单边缺口三点弯曲(SEN3PB)实验对三种弹性体增韧尼龙1010共混物的断裂力学行为进行研究,结果表明当分散相粒径小于1μm时共混物的极限比断裂能(u0)随分散相粒径增加而增加,而当分散相粒径大于1μm时,u0则显著下降;耗散能密度(ud)则随分散相粒径增加而降低。外部塑性变形区是断裂过程中能量耗散的主要区域,基体的剪切屈服是增韧的主要机理。与弹性体共混改性虽然能大幅度提高尼龙1010的缺口冲击强度,但材料的刚性却由于加入弹性体而显著下降。因此,选用玻璃纤维(GF)对尼龙1010/弹性体共混物进行增强改性,通过熔融共混制备了尼龙1010/POE-g-MAH/GF复合材料。尼龙1010/POE-g-MAH/GF复合材料的屈服强度、弯曲强度和模量随GF用量增加几乎呈线性增加。采用修正的EWF模型研究了尼龙1010/POE-g-MAH/GF复合材料的断裂力学行为,发现复合材料的u0随GF用量的增加先增加然后逐渐降低,在GF用量为10 wt%时,u0达到最大;复合材料的ud则随GF用量的增加而逐渐降低。尼龙1010/GF复合材料的临界应力场强度因子随GF用量增加而逐渐提高,这表明GF能够提高尼龙1010抵御裂纹的能力。通过POE-g-MAH和GF共同改性,尼龙1010的冲击强度和屈服强度有了明显提高,吸水率显著下降,维卡软化点则基本保持不变。通过熔融共混的方法制备尼龙1010/笼型结构多面体齐聚倍半硅氧烷(POSS)复合材料,研究POSS对尼龙1010热稳定性的影响。POSS能在一定程度上提高尼龙1010的积分程序分解温度和800 oC时的残炭量。对尼龙1010/POSS复合材料在氮气气氛下的热降解动力学研究表明:尼龙1010在氮气气氛中的非等温降解为一级反应,POSS能显著提高尼龙1010的非等温降解反应的活化能,但对反应级数影响很小。对尼龙1010/POSS复合材料的使用寿命预测表明:在温度相对较低的情况下,POSS能显著提高尼龙1010的使用寿命。热重-红外联用分析表明尼龙1010在氮气气氛下的降解产物主要为小分子的低聚物,POSS并不改变尼龙1010降解产物的组成。最后,研究了EVM和尼龙1010在加工过程中的反应性。在不同加工温度下制备了尼龙1010/EVM 8939(VA含量90 wt%)(50/50)共混物,尼龙1010/EVM 8939(50/50)共混物的拉伸强度和断裂伸长率随加工温度升高先增加而后逐渐降低。对甲基苯磺酸(TsOH)显著降低了尼龙1010/EVM 8939(50/50)共混物的拉伸强度和断裂伸长率;亚磷酸三苯酯(TPPi)则能提高共混物的断裂伸长率。EVM与TsOH在高温下可以发生化学反应。通过热重、热重-红外联用以及核磁共振等分析手段表明相关反应机理为:EVM在TsOH作用下发生水解,生成具有类似于乙烯-乙烯醇共聚物结构的产物,该产物在TsOH的作用下进一步发生分子内脱水生成主链含有双键的结构。当EVM中的VA含量较高时则将生成主链含有共轭双键的结构,该结构赋予EVM与TsOH反应产物许多优良性能,具有潜在的应用价值。本论文的主要创新之处:(一)截至目前为止,关于尼龙1010共混改性的相关报道较少。本论文首次使用高VA含量(40 wt%)的乙烯-醋酸乙烯酯橡胶(EVM 400)对尼龙1010进行抗冲改性,成功制备了高抗冲尼龙1010(缺口冲击强度大于50 kJ/m2)。并通过粒子间距模型揭示了尼龙1010/EVM 400共混物结构与性能之间的关系,计算出了EVM 400增韧尼龙1010的临界粒子间距为0.2μm。(二)将增韧尼龙1010所用的抗冲改性剂扩展到一系列具有不同VA含量(0～90 wt%)和不同门尼粘度的乙烯-醋酸乙烯酯共聚物(EVA),当所用EVA的VA含量在28～60 wt%范围内时,成功制备了高抗冲尼龙1010。系统地研究了EVA对尼龙1010的增韧效果,并将增韧效果与EVA的玻璃化转变温度和结晶度相关联。(三)在前面研究的基础上,通过使用弹性体和玻璃纤维对尼龙1010进行增韧和增强改性,显著提高了尼龙1010的韧性和刚性,尼龙1010的吸水率明显降低而耐热性则基本保持不变,成功制备出综合性能良好的尼龙1010复合材料。采用修正的断裂有用功模型和线弹性断裂力学模型对尼龙1010复合材料的断裂力学行为进行研究,研究玻璃纤维用量对复合材料断裂力学参数的影响。(四)首次选用笼型结构多面体齐聚倍半硅氧烷(POSS)来改善尼龙1010的热稳定性,并研究了尼龙1010及尼龙1010/POSS复合材料在氮气气氛下的非等温降解动力学,POSS能显著提高尼龙1010降解反应的表观活化能但并未改变反应级数。(五)初步研究了乙烯-醋酸乙烯酯橡胶(EVM)和尼龙1010在高温下的反应性,报道了EVM和TsOH在高温条件下的反应性,通过核磁共振、热重-红外联用等分析表征方法探索了相关的反应机理,EVM和TsOH反应后,EVM的耐溶剂性、玻璃化转变温度和力学性能均有所提高,而体积电阻率则显著下降。EVM和TsOH两者之间的反应具有重要的应用价值。更多还原

【Abstract】 As a Chinese unique nylon, nylon 1010 has good abrasion resistance, self lubrication and low temperature properties, but it has low notched impact strength due to its low crack propagation energy. In this work, ethylene-vinyl acetate copolymers (EVA) and its maleated version (EVA-g-MAH) were chosen as impact modifiers to toughen nylon 1010 through melt blending, and nylon 1010 blends with high notched impact strength were obtained. The related toughening mechanism was systematically investigated, and the interparticle distance (ID) model was used to reveal the relationship between the notched impact strength and morphology of nylon 1010 blends.Firstly, ethylene-vinyl acetate rubber with 40 wt% VA content (EVM 400) was used as impact modifier for nylon 1010 and its toughening effect was investigated. The notched impact strength of nylon 1010/EVM 400 blends increased with increasing EVM 400 content. A brittle-ductile transition (BDT) was observed when the EVM 400 content increased from 40 phr (per hundred nylon 1010) to 80 phr, and the notched impact strength increased from 22.8 kJ/m2 to 62.3 kJ/m2. For nylon 1010/EVM 400 (100/20) blend, the notched impact strength increased significantly after the addition of EVA-g-MAH, and a BDT was also observed when EVA-g-MAH content increased from 2.5 phr to 5 phr. Scanning electron microscope showed EVA-g-MAH significantly improved the dispersion of EVM 400 in nylon 1010 matrix, and the number average diameter (dn) of EVM 400 particles decreased significantly with increasing EVA-g-MAH content. The ID model showed that a sharp BDT was observed for nylon 1010/EVM 400 and nylon 1010/EVM 400/EVA-g-MAH blends when the interparticle distance was about 0.2μm, independent of the addition of EVA-g-MAH. Then, the impact modifiers used were expanded to a series of EVA with different VA content and Mooney viscosity. The VA content and Mooney viscosity of EVA significantly affected the notched impact strength of nylon 1010/EVA/EVA-g-MAH (80/15/5) blends. The nylon 1010/EVA/EVA-g-MAH (80/15/5) blends with high notched impact strength (over 60 kJ/m2) were obtained when the VA content ranged from 28 wt% to 60 wt%. The effect of VA content on the notched impact strength of nylon 1010/EVA/EVA-g-MAH (80/15/5) blends was related to the glass transition temperature (Tg) and crystallinity of EVA. For nylon1010/EVA/EVA-g-MAH (80/15/5) blends with EVA with the same VA content, high viscosity of EVA usually led to low notched impact strength due to the serious aggregation of EVA in nylon 1010 matrix. A relationship between the notched impact strength and morphology of nylon 1010/EVA/EVA-g-MAH (80/15/5) blends was generally in agreement with the ID model.The impact modifiers used were further expanded to different elastomers, and the toughening effects of different elastomers on nylon 1010 were compared. Ethylene-1-octene copolymer (POE), styrene-ethylene-butadiene-styrene block copolymer (SEBS), EVM and also their corresponding maleated versions (POE-g-MAH, SEBS-g-MAH, and EVA-g-MAH) were melt blended with nylon 1010. The elastomer type significantly affected the notched impact strength of nylon 1010/elastomer/maleated elastomer blends. EVM had the best toughening effect on nylon 1010 in the absence of maleated elastomers were added. Among all the nylon 1010/elastomer/maleated elastomer blends, nylon 1010/SEBS-g- MAH (80/20) blend had the highest notched impact strength at room temperature, and nylon 1010/POE-g-MAH (80/20) blend had the best low temperature toughness. The modified essential work of fracture (EWF) was used to characterize the fracture behavior of nylon 1010/elastomer/maleated elastomer blends. The limited fracture energy (u0) of the blends increased with increasing dn when the dn was below 1μm and decreased sharply when dn was over 1μm, while the dissipative energy density (ud) increased with decreasing dn. The energy consumed in the outer plastic zone was the main part of dissipated energy during the fracture process, and the shear yielding of nylon 1010 matrix was the main toughening mechanism.Although the notched impact strength of nylon 1010 could be significantly increased by blending nylon 1010 with suitable elatomers, the stiffness of nylon 1010 decreased obviously due to the addition of elastomers. A good trade-off between stiffness and toughness was obtained by the combination of POE-g-MAH and glass fiber (GF). The yield strength, flexural strength and modulus almost linearly increased with increasing GF content. The modified EWF model was used to characterize the fracture behavior of nylon 1010/POE-g-MAH/GF composites. For nylon 1010/POE-g-MAH/GF composites, with increasing GF content, ud gradually decreased and u0 reached the maximum value at the GF content of 10 wt%. The critical stress intensity factor of nylon 1010/GF composites increased with increasing GF content, suggesting GF could enhance the crack resistance of nylon 1010. POE-g-MAH and GF significantly increased the toughness and stiffness of nylon 1010, and decreased the water absorption ratio of nylon 1010.The effect of Polyhedral Oligomeric Silsesquioxane (POSS) on the thermal stability of nylon 1010 was also investigated. POSS increased the integral procedure decomposition temperature and char yield at 800 oC of nylon 1010. The Doyle-Ozawa and Friedman methods were used to characterize the non-isothermal decomposition kinetics of nylon 1010 and its composites in nitrogen. The non-isothermal decomposition of nylon 1010 in nitrogen was first order reaction. POSS significantly increased the activation energy of nylon 1010 but had little effect on the reaction order. The lifetime of nylon 1010 and nylon 1010/POSS composites decreased with increasing temperature. POSS significantly prolonged the lifetime of nylon 1010, especially at relatively low temperatures. TG coupled FTIR showed the non-isothermal decomposition products of nylon 1010 were polyamide oligomers, and POSS did not change the formulation of the decomposition products.Finally, the reaction between EVM and nylon 1010 during melt blending was also investigated. Nylon 1010/EVM 8939 (VA content, 90 wt%) (50/50) blends were prepared at different mixing temperatures. Both the tensile strength and the elongation at break of nylon 1010/EVM 8939 (50/50) blends went through maximum values with increasing mixing temperature. p-toluenesulfonic acid (TsOH) significantly decreased the tensile strength and elongation at break of nylon 1010/EVM 8939 (50/50) blends, while triphenyl phosphate obviously increased the elongation at break of nylon 1010/EVM 8939 (50/50) blends. An obvious reaction was observed between EVM and TsOH during melting mixing at elevated temperature. The related reaction mechanism was further studied and could be interpreted as follows: EVM was hydrolyzed in the existence of TsOH, and then the hydrolyzation product was intra-molecule dehydrated to form conjugated double bonds. Such conjugated double bonds contributed many excellent properties to EVM materials, which has potential application in future.The innovations of this dissertation are list as follows:(1) The impact modification of nylon 1010 had not been widely investigated. In this work, ethylene-vinyl acetate rubber with 40 wt% VA content (EVM 400) was firstly used as impact modifier to toughen nylon 1010, and nylon 1010/EVM 400 blends with high notched impact strength (over 50 kJ/m2) were successfully prepared. The relationship between the morphology and the notched impact strength of nylon 1010/EVM 400 blends was revealed by the interpaticle distance (ID) model, and the critical ID for EVM 400 toughened nylon 1010 was around 0.2μm, which has not been reported before.(2) The impact modifiers used were further expanded to a series of ethylene-vinyl acetate copolymer (EVA) with different VA content (0 ~ 90 wt%) and Mooney viscosity. Nylon 1010 with high notched impact strength (over 50 kJ/m2) was prepared when the VA content of EVA ranged from 28 wt% ~ 60 wt%. The toughening effects of EVA with different VA content on nylon 1010 were further related to the glass transition temperature and crystallinity of EVA.(3) Maleated ethylene-1-ocetene copolymers (POE-g-MAH) and glass fiber (GF) were used to modify nylon 1010. After the addition of POE-g-MAH and GF, the notched impact strength and the yield strength of nylon 1010 significantly increased, while the water absorption ratio of nylon 1010 obviously decreased. Nylon 1010 composites with good comprehensive properties were successfully prepared. The modified essential work of fracture and linear elastic fracture machanics were used to investigate the fracture behavior of nylon 1010 composites. The effect of GF content on the fracture parameters was investigated.(4) Polyhedral Oligomeric Silsesquioxane (POSS) was firstly used to enhance the thermal stability of nylon 1010. The non-isothermal decomposition kinetics of nylon 1010 and nylon 1010/POSS composites in nitrogen were investigated. POSS significantly increased the activation energy but had little effect on the reaction order.(5) Exploring research was carried out on the reaction between EVM and nylon 1010. The reaction between EVM and TsOH during melt mixing was also invesigated, and related reaction mechanisms were studied in terms of NMR, TGA-FTIR and etc. The reaction between EVM and TsOH contributed EVM many excellent properties such as increased solvent resistance, glass transition temperature, mechanical properties and decreased volume resistivity, which has potential application in future.更多还原