Shearing test is carried out on the joint which bonded under different pre curing processes with two component adhesives of acrylic and epoxy resin respectively. The pre curing strength is obtained, which used to analyze the relationship between the pre curing strength and time. The hoods with different pre curing strength are baking with high temperature. The deformation of different areas of the hood is measured with gauges, and the deformation characteristics of the hood after baking are acquired with comparative analysis. Combining the components of two component adhesives and DSC test, the pre curing mechanism of different adhesive systems are studied. Therefore, the key factors and regular pattern of the deformation for the hood are obtained. The results indicate that, finally deformation of the hood after high temperature baking varies with the pre curing time. The key of the pre curing time of acrylic adhesives lies in the chain initiation stage of the free radical polymerization reaction. Due to the influence of the chemical properties of methyl acrylate and its initiator, the pre curing reaction induced by free radical polymerization is very fast. The shear strength of this joint can reach to 3.67 MPa with a pre curing time of 1 h, which quickly achieving the pre cure strength required for deformation control. For epoxy adhesives, the rate determining step in pre curing process is the esterification reaction. Due to the influence of the structure of carboxylic acid, the esterification process is relatively long. Shear strength of this joint can only reach 0.87 MPa after pre curing for 4 h without external heating.
分别采用2,3,3',4'-联苯四甲酸二酐(α-BPDA)、2,3,3',4'-二苯醚四甲酸二酐(α-ODPA)、均苯四甲酸二酐(PMDA)、3,3',4,4'-联苯四甲酸二酐(s-BPDA)以及二胺单体,利用化学亚胺化或热亚胺化方法制备了不同分子结构的热塑性聚酰亚胺树脂模塑粉.借助热重分析(TG)、红外光谱(FTIR)、动态热力学分析(DMA)、扫描电子显微镜(SEM)和力学性能测试等表征分析方法,研究了分子主链结构对热塑性聚酰亚胺理化性能、力学性能的影响.结果表明,基于扭曲非共面联苯结构的α-BPDA合成的LPI-1聚酰亚胺树脂玻璃化转变温度为326℃,5％热分解温度为554℃,冲击强度为88.5 kJ/m2,拉伸强度为111.3 MPa,兼具较好的耐热性与韧性.
螺纹形式严重影响双螺杆挤出材料的均匀性.基于Polyflow建立了正螺纹及不同槽数、槽深的开槽螺纹元件下等规聚丙烯混合挤出过程的模拟模型.借助Polystat从停留时间、剪切速率、分离尺度等角度分析了螺纹元件的分散混合能力.结果表明,相比于正螺纹,开槽螺纹建压能力弱,降低了螺杆的挤出能力,但开槽螺纹有利于物料的反流及物料在螺杆内的停留时间;当一周开槽数为6且槽深为4 mm时,物料所受剪切速率最大,比正螺纹大22 s-1;当一周开槽数为8且槽深为4 mm时,其分离尺度相比于正螺纹元件降低了 40％,其破碎效果相比于正螺纹提升了 38％,更有利于粒子的分布混合及分散混合,提升物料的均匀性.
2023年,我国高校毕业生人数达1158万,创历史新高,整体就业形势十分严峻,大学生就业压力十分巨大.但在全球提倡低碳环保、致力实现"双碳"目标的趋势下,能源/化工/环保的重要性日益显现,化工类专业大学生就业机会同其他行业相比也有了大幅增长.据《2023届高校毕业生就业数据报告》数据显示,能源/化工/环保应届毕业生职位同比增长超40％,居行业首位.虽然岗位供给有所增加,但由于化工行业某些领域存在一定的危险性和污染性,使得化工类专业大学生就业出现一方面学生就业难,另一方面企业人才难觅的现象.由化学工业出版社出版,宋来新、商云龙编著的《化工类专业大学生职业发展与就业指导》(2017年版)一书,结合化工行业特色及化工类学生实际需求,通过真实案例,引导帮助学生解决职业生涯发展过程中遇到的问题,助力学生职场起航.全书立足专业背景、凸显行业特色,为高校化工类专业大学生职业生涯规划教育奠定了坚实的理论和实践基础.
随着计算机技术的快速发展和应用,化工企业已经在化工生产、办公管理等方面实现了网络化和自动化,有效提升了化工企业的信息共享程度,使化工企业的生产效率和工作质量得以稳步提升.但是,在计算机网络技术广泛应用的时代背景下,计算机网络安全问题出现的频率也在不断升高,一些不法分子会利用技术漏洞来对他人的计算机进行攻击,以窃取他人数据信息,从而谋取不法利益.因此,化工企业必须要提升网络安全的重视程度,以保障企业的网络使用中的安全性.
