【作者】 王思静；

【导师】 熊金平；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 硕士

【摘要】 本文研究了溴化丁基橡胶(BIIR)在热氧、紫外照射、溶剂浸泡和盐雾环境中的老化行为,初步推断其热氧和紫外老化机理,并选择不同评价指标预测溴化丁基橡胶在不同环境中的使用寿命。在热氧环境中,BIIR老化后表面产生粉化与裂纹,并且温度升高将导致裂纹数目增加,宽度增大。随热氧老化时间的延长,当温度在25～60℃时,BIIR的交联密度、硬度、拉伸强度和扯断伸长率几乎不变化,当温度在70℃以上时,BIIR的硬度和交联密度逐渐增大,而拉伸强度和扯断伸长率逐渐降低,当温度达到110℃以后,BIIR的硬度仍在增大,而拉伸强度和扯断伸长率几乎丧失,交联密度也出现降低。热氧作用对BIIR的热稳定性影响较大。热氧老化使BIIR分子中的双键减少的同时,伴随有羟基和羧基等基团生成,同时BIIR结构中主链断裂氧化导致-CH2-、异丙基基团减少,热氧老化温度升高加剧上述基团变化程度。在BIIR热分解过程中,-C-Br键因键能较低而首先发生断裂,出现脱溴化氢的反应,之后-C-C-键所形成的主链断裂,断链后的低聚物后期在氧的存在作用下大量生成烃类气体分子。在紫外照射环境中,老化使BIIR表面产生粉化与开裂,且裂纹的密度随紫外老化时间的延长而逐渐增大。随紫外老化时间延长,BIIR的交联密度和硬度逐渐增大,而拉伸强度和扯断伸长率则逐渐降低,且拉伸强度在初始老化2天时间内有所增大。紫外照射环境对BIIR的热稳定性影响不大。紫外老化过程中氧的参与作用导致羟基和羧基等基团的增多,继而使BIIR分子中的主链断裂而导致-CH2-基团和异丙基基团的减少。BIIR中,-C-Br键键能较低,紫外光照射下首先发生断裂生成气体逸出,之后与双键相连的a位的甲基氢处形成过氧化反应中心,引致之后链断裂。50℃环境下,在93#汽油中,BIIR10天后质量溶胀率超过100%且表面出现发粘,其耐油性较差；在环己烷非极性溶剂中,7天后质量溶胀率达96.2%且未出现表面发粘现象；在乙醇极性溶剂中,6天后质量溶胀率仅0.45%,几乎不能溶解或溶胀。在35℃盐雾环境中,随着老化时间延长,BIIR表面产生凹凸不平和空洞,并有微裂纹产生；质量变化率逐渐增大；硬度增大,而拉伸强度和扯断伸长率则逐渐降低,随老化时间延长,变化趋势逐渐平缓。50℃条件下,在热氧环境中,当选用交联密度、硬度、拉伸强度和扯断伸长率作为评价指标时,BIIR的使用寿命分别为68天、107天、63天和54天；在紫外环境中,当选用交联密度、硬度、拉伸强度和扯断伸长率作为评价指标时,BIIR的使用寿命分别为47天、540天、41天和34天；在溶剂环境中,当选用质量溶胀率作为评价指标时,BIIR在93#汽油和环己烷中的使用寿命均为1天,而在乙醇中的使用寿命则较长；在盐雾环境中,当选用质量变化率、硬度和扯断伸长率作为评价指标时,BIIR的使用寿命分别为24195天、4359天和622天,以拉伸强度作为评价指标时,其使用寿命则较长。更多还原

【Abstract】 Aging behavior of brominated butyl rubber(BIIR) were studied in thermal-oxidative,UV irradiation,solvent immersion and salt spray environments,and the mechanism in the environment of thermal-oxidative and UV irradiation were predicted.Different Evaluating indicators were adopted to predict the service life of BIIR in various environments.In thermal-oxidative environment, crack and powder were produced on the surface of BIIR after aging.The higher the temperature and the wider the crack.When the temperature were during 25～60℃,the crosslink denstiy,hardness,tensile strength and elongation at break rarely changed with aging.The hardness and crosslink density increased,while the tensile strength and elongation at break decreased at 70℃and above with the elongation of aging time.When the temperature reached 110℃,the hardness increased,while the tensile strength and elongation at break were almost lost,and crosslink density began lower.The thermal-oxidative stability was deteriorated after aging in this environment.From the results of ATR-FTIR spectroscopy it can be concluded that the increasing strength of the peak of carboxy groups and hydroxyl groups of BIIR,but the decreasing of double bonds, isopropyl groups and methylene groups of its with the increasing temperatures. The bond energy of -C-Br is low and first fractured in the process of BIIR thermal decomposition,the reaction of hydrogen bromide off happened. Then, the main strand broke and formed -C-C-bond.In the late period,the oligomers at the presence of oxygen generated hydrocarbon gas molecules. In the UV irradiation environment,crack and powder appeared on the surface and the crack density increased gradually with aging.The hardness and crosslink density tended to increase while the tensile strength and elongation at break decreased.The thermal-oxidative stability was not deteriorated upon exposure to UV. The spectroscopy of ATR-FTIR illustrated oxygen took part in the aging and the increasing strength of the peak of carboxy groups and hydroxyl groups,but the decreasing of methylene groups and isopropyl groups of BIIR with aging-C-Br bond in BIIR is low and the bond was broken first to generate gas under UV irradiation. After that peroxide reaction center formed in the position of a of methyl hydrogen connected with double bond resulting in strand breaks later.Under 50℃, the swelling rate of the brominated butyl rubber reached more than 100% after 10 days in 93# gas, and the surface was sticky. It indicated the oil resistance of BIIR was poor.Under the same temperature in cyclohexane as the non-polar solvent, swelling rate was 96.2% after 7 days and the surface did not appear sticky,while in polar solvents ethanol, the swelling rate of BIIR was 0.45% after 6 days almost insoluble or swelling.In the environment of salt spray at 35℃, with increasing of aging time, the surface of BIIR became uneven and cavity, and micro-cracks. Rate of quality change increased.The hardness gradually increased, while the tensile strength and elongation at break decreased gradually.With the elongation of time,these change gradually flattened.In thermal-oxidative environment,the service life of BIIR is 68d,107d,63d and 54d when crosslink density,hardness,tensile strength and elongation at break are used as evaluating indicators,respectively.In UV irradiation environment,its service life is 47d,540d,41d and 34d when crosslink density,hardness,tensile strength and elongation at break are used as evaluating indicators,respectively. In the solvent environment, selected the rate of quality change as evaluating indicator, its service life in the 93# gasoline and in cyclohexane is 1d respectively, while in ethanol is longer. In the salt spray environment, the service life of BIIR is 24195d,4359d and 622d when rate of quality change,hardness and elongation at break are used as evaluating indicators respectively,and its service life is longer when tensile strength as evalutating indicator.更多还原