The elasticity and yield parameters of PE were determined through a uniaxial tensile experiment.A pipe-soil fi-nite element model under a point load was established to study the point-loading mechanical response of buried PE gas pipes,and the effects of point-loading dimension,pipe internal pressure,and pipe diameter were analyzed.Based on the DFDI(ductile failure damage indicator)model and combined with the finite element simulation results,quantitative dam-age calculations were carried out for PE pipes under a point load.The results indicated that the point load increased the pipe damage when compared to the damage results of the pipe without a point load.The pipe damage shows a great change with a variation of the internal pressure of the pipe.There is little effect on the PE pipe damage with a small change in the pipe diameter,and the damage values under each pipe diameter are relatively close to each other.
Traditional epoxy resins are made from non-renewable fossil resources, which are difficult to reprocess and recycle, and their flammability makes them unsafe during use. In this experiment, an epoxy resin containing Schiff base (TA-VAN-EP) was synthesized successfully with biomass-derived raw materials. This new material not only had favorable mechanical properties but also had good flame retardancy and degradation properties. The chemical structure of TA-VAN-EP was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (NMR) spectroscopy. Its mechanical properties, thermal stability, flame-retardant properties, and other properties were tested. The results showed that, compared with the pure epoxy resin (EP), the mechanical properties of TA-VAN-EP were significantly improved, and the glass transition temperature (Tg) was increased from 152 degrees C to 190 degrees C. Additionally, TA-VAN-EP reached a V-1 rating during the UL-94 test, and the limited oxygen index (LOI) value increased from 24.7% to 28.4%. Also, the total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) decreased extremely. Moreover, TA-VAN-EP demonstrated good degradation performance under acidic conditions. In conclusion, this work provided a new idea for the production of bio-based flame-retardant epoxy resin with promising degradable abilities and mechanical properties.
Using bisphenol A (BPA) and isophthalaldehyde (IPD) as comonomers, based on open system and solution polycondensation method, phenolic resin was prepared by microwave. The reversible thermochromic composite solution polymerized butadiene styrene rubber film was prepared by resin as chromogenic agent. The resin was tested by gel permeation chromatography, 1 H and 13 C NMR spectrometers, thermogravimetric analyzer, and thermal analyzer, etc. The composite film was tested by thermogravimetric analyzer, thermal analyzer, spectrophotometer, and polarizing microscope, etc. The factors affecting the thermochromic properties, thermal stability, thermal recyclability stability and microscopic morphology of the composite film were studied. The results indicate that BPA-IPD is the 2,6-monosubstituted bisphenol A isophthalaldehyde phenolic resin with M – n of 1.150 × 10 3 g mol –1 and PDI of 1.004. Therefore, the number of monomers in molecular chain containing BPA and IPD are 3 and 3, respectively. When the mass ratio of crystal violet lactone, resin, mixed alcohols (cetyl alcohol and octadecanol) and solution polymerized butadiene styrene rubber is 1 : 1.5 : 30 : 50, i.e., 0.0075 : 0.011 : 0.23(0.14 : 0.09) : 0.38(g), the composite film is obtained by salivation method. The total color difference (Δ E ) of composite film is about 90, and its absorption/scattering color depth difference [Δ( K/S )] values are averagely 20 and 40 at visible light zone of 480– 600 and 600–660 nm at the low temperature region (10–33°С) of phase change during constant speed cooling, respectively. The composite film has good thermal stability and recyclability stability.
Attributed to the merits of excellent material compatibility, healing performance, and long-term stability, the self-healing system based on microencapsulated epoxy-amine chemistry is a potentially practical self-healing system for both structural and functional materials. Herein, based on the microencapsulated epoxy-amine chemistry, a self-healing anticorrosion coating was successfully developed. This self-healing coating system was modeled theoretically to explore the factors that influence the crack filling and the self-healing anticorrosion function. The established quantitative relationship shows that the filling depth of the crack in the coating is proportional to the microcapsule parameters and coating thickness, but inversely proportional to the crack width. Based on the above theoretical model, the effects of various parameters on the anticorrosion performance were experimentally studied. The actual filling of small in-situ cracks (<100 mu m) generated by impact damage was semi-quantitatively characterized using scanning electron microscopy (SEM). The filling behavior is consistent with the theoretical modeling. After being healed at room temperature for 2 days upon impact damage, the formulated self-healing coatings were subjected to accelerated corrosion tests in 10 wt% sodium chloride (NaCl) solution for 2 days to observe their anticorrosion behavior. Compared to the neat epoxy coating, all the formulated self-healing epoxy coatings show evident anticorrosion function. Good self-healing anticorrosion performance was achieved by adding 10.0 wt% microcapsules with a size of 100-150 mu m to the coating with a thickness of 300 mu m. The results of this investigation laid a theoretical and technical foundation for the further development of both the self-healing chemistry and the self-healing anticorrosion coating.
热固性树脂拥有优异的力学性能和热性能,但是不能重新加工且很难降解,通过将席夫碱引入热固性树脂中,利用其解离机制使热固性树脂具备重塑性与降解性是生物质材料的研究热点.本文介绍近年来席夫碱结构热固性树脂的合成方法,列举了常用的合成材料,并阐述了席夫碱结构的降解机理,针对席夫碱结构的特点列举了不同的应用领域;最后总结全文并提出了展望.
双螺杆挤出机在生产过程中经常会出现螺杆磨损等问题,严重影响了螺杆的使用寿命和聚合物加工的品质.本文采用离散单元法(DEM),结合Archard磨损模型,对同向啮合双螺杆挤出机螺杆磨损进行数值模拟,分析螺杆转速和填充率等因素对双螺杆挤出机磨损特性的影响规律.结果表明,螺杆磨损主要发生在螺棱的顶部区域以及进料口处,在物料进入机筒入口处会发生严重的挤压磨损;随着螺杆转速和填充率的增加,螺杆的磨损程度不断增大;料槽后方输送段的螺杆主要产生横向切削磨损,切向累积能量是导致磨损的关键因素.
建立高效液相色谱质谱联用法(HPLC-QQQ)对食品接触材料中的双酚A迁移量进行测定,以咖啡杯为检测对象,验证双酚A检测方法的可行性.该法实现了双酚A迁移量在食品接触材料中的测定,重复性、稳定性、日内精密度及日间精密度良好,定量限为0.10 mg/kg,检出限为0.01 mg/kg,加标回收率为99.35%.在0～1.0 mg/L浓度范围内,双酚A的浓度与峰面积成正相关,线性关系良好.该方法操作简便、快捷、定量定性精确,能满足双酚A迁移量在食品接触材料中的测定.
以聚醚砜(PES)为原料,采用氯磺酸(CSA)为磺化剂,通过控制反应温度和时间制备系列磺化聚砜(SPES),并以SPES为基质,二维黑磷(BP)为功能填料,采用溶液铸膜法制备了复合质子交换膜.采用红外光谱分析仪(FT-IR)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对材料结构进行表征,研究了复合膜的吸水率、质子交换性、阻醇性等.结果表明,SPES的磺化度随反应温度、时间、磺化剂浓度的升高而增大.BP的添加增强了复合膜的热稳定性、氧化稳定性、质子交换性、阻醇性等综合性能.在相同测试条件下SPES基膜的甲醇渗透率为1.185×10-6 cm2/s,而5%(质量分数,下同)SPES/BP复合膜的甲醇渗透率仅为2.88×10-7 cm2/s.
通过熔融共混法在聚乙烯中加炭黑,模拟制备管道用聚乙烯/炭黑复合材料.采用了不同的焊接条件包括单程序焊接和多程序焊接进行复合材料的焊接,并对焊接性能、焊接管道的力学性能、结晶性能、微观形态进行了研究.结果表明,复合材料的制备工艺流程中挤出机的加工温度应避免超过240℃以上,且螺杆转速不超过40 r/min时能够有效避免管道制备过程产生炭黑分散不均匀以及气泡的缺陷;焊接过程中,单段式程序焊接过程中会出现实验末期温度急剧上升的情况,而多段式焊接程序能够使熔区温度保持在一个相对稳定的温度区间,对焊接试样进行拉伸剥离实验可知,多段式焊接程序的焊接性能要优于单段式焊接程序.
综述了聚丁二酸丁二醇酯(PBS)及其共混物的制备及应用进展.目前国内外PBS的合成工艺主要有直接酯化法、酯交换法和扩链法.PBS的耐热性好、力学性能优良,是可完全生物降解的脂肪族聚酯,能从根本上解决塑料白色污染的重要材料之一.PBS与脆性可降解聚酯共混可以提高其韧性和生物降解性;通过与其他可再生资源如热塑性淀粉、木薯淀粉、开心果壳粉共混可以提高刚性和熔点,改善力学性能的同时降低成本;与少量无机填料如碳酸钙、二氧化硅等共混不仅可以降低PBS的价格还可以改善PBS的性能.PBS目前主要应用于包装材料、农林业用品、日用杂品、纺织业及医用制品中.PBS作为薄膜应用时其力学性能及气体阻隔性能是两项重要的指标,所以重点总结了对PBS复合膜的力学和阻隔性能的改善研究进展.最后对PBS未来的研究和发展方向进行了展望,指出PBS生产技术应该向综合性能高、成本低和绿色环保方向发展.
利用可再生资源为协效剂,将竹基多孔碳(PCM)与二乙基次膦酸铝(AlPi)添加于环氧树脂(EP),研究了PCM协同AlPi催化阻燃EP复合材料性能及作用机理.结果表明,PCM(3%)与AlPi(4.4%)复合于EP后,复合材料的极限氧指数(LOI)由纯EP的24.6%提高到42.6%,UL 94测试达到V-0级,热释放速率峰值降低60.7%,PCM协同AlPi催化阻燃EP的效果显著.热失重-红外光谱联用、热失重-质谱联用、X射线光电子能谱及拉曼光谱研究揭示,PCM具有催化AlPi在气相释放二乙基次膦酸捕捉自由基,在凝聚相形成氧化铝、磷酸铝和焦磷酸铝,提高炭层的耐热氧化能力及促进类石墨炭层形成的作用.
为探究热熔螺母嵌件与塑胶的连接性能,将热熔螺母嵌件连接方式合理应用到三维(3D)打印塑胶壳体中.通过单因素试验分析了嵌件类型、热熔温度和孔洞直径对热熔螺母嵌件与塑胶连接性能的影响,采用田口方法对埋植参数进行优化,得到埋植参数的优化组合,完成了热熔螺母嵌件在3D打印电子产品壳体中的应用实践.结果表明,嵌件的形状影响了其与塑胶的连接性能,各类嵌件的抗拔脱性能排序为:斜纹>网纹>直纹,抗扭转性能排序为:斜纹>直纹>网纹;180～220℃范围内,随着热熔温度的升高,嵌件与塑胶的连接性能增强;5.8～6.0 mm范围内,随着孔洞直径的减小,嵌件与塑胶的连接性能增强;埋植参数对嵌件与塑胶连接性能的影响程度为:嵌件类型>孔洞直径>热熔温度,优化埋植参数为:嵌件类型(斜纹)、孔洞直径(5.8 mm)、热熔温度(220℃),此参数组合下热熔螺母嵌件的最大拉出力1.22 kN、最大扭矩3.04 N·m,嵌件与塑胶的连接性能最佳.
系统地评价了商用选择性激光烧结(SLS)聚丙烯(PP)的加工性能和力学性能,并比较了它和注射成型(IM)样品的差异.结果表明,预热温度、激光功率和能量密度作为选择性激光烧结的3个重要工艺参数,对最终产品的性能有很大影响.在选择工艺参数时,必须同时兼顾制品的力学性能和尺寸精度.本文的独特之处在于定量分析了不同工艺条件下选择性烧结带的结晶形态,建立了工艺条件、结晶晶型和力学性能之间的关系.通过调整选择性激光烧结的工艺参数,可获得不同晶型含量的样品,以便调控制品的力学性能.
以硅橡胶(SR)为基体,添加莫来石纤维(MF)、空心玻璃微珠(GB)、碳酸钙(CaCO3)、2,5-二甲基-2,5-双(叔丁基过氧基)己烷、铁红(Fe2O3),制备了母炼胶.通过添加不同份数比的氢氧化铝[Al(OH)3]和氢氧化镁[Mg(OH)2],经过密炼、开炼、硫化制备了可陶瓷化阻燃有机硅橡胶复合材料.结果表明,所制备的可陶瓷化阻燃硅橡胶复合材料中,GB在高温下能够起到黏结桥梁的作用,MF能很好地起到骨架作用,添加30份Mg(OH)2的硅橡胶复合材料,其拉伸强度可达4.93 MPa,同时具有1 450.73%的断裂伸长率,而极限氧指数(LOI)值可以达到31.8%,水平垂直燃烧达到V-0级,硅橡胶复合材料在50 Hz频率、5 g加速度、1 050℃的温度下燃烧15 min,试样不被烧穿.
利用广角X射线衍射仪和差示扫描热仪研究了不同增压速率、不同增压温度下等规聚丙烯/多壁碳纳米管(iPP/MWCNTs)复合材料的结晶行为.结果表明,慢速增压条件下(1 MPa/s),增压温度较低时有利于α-iPP的生成,增压温度越高越有利于γ-iPP的生成,且慢速增压条件下MWCNTs对iPP的结晶具有诱导作用,制备的γ-iPP较稳定,在升温过程中不会发生熔融重结晶现象;快速增压条件下(200 MPa/s),较低的增压温度就能够制备出纯的γ-iPP,但MWCNTs的存在使iPP的熔体黏度增大,阻碍分子链运动,不利于晶体生长,形成的γ晶结构完善性较差,在升温过程中会发生熔融重结晶,增压温度较高时,快速增压能够制备出亚稳态中间相iPP.对比发现,增压速率和熔体记忆效应的协同作用共同决定了复合材料中iPP的结晶结构,慢速增压条件下熔体记忆效应对iPP的结晶结构影响较大,增压速率升高后,熔体记忆效应对其结晶行为的影响减弱.
基于误差传递公式,对马来酸酐接枝聚丙烯(PP-g-MAH)接枝率的酸碱反滴定法测定建立了误差模型,讨论了取样量、HCl-异丙醇溶液浓度和接枝马来酸酐含量对接枝率测定误差的影响.实验室制备了PP-g-MAH,进行了红外光谱分析,分别以不同取样量、HCl-异丙醇溶液浓度对接枝物进行了接枝率测定;对比了不同马来酸酐含量PP-g-MAH的接枝率测定误差.结果表明,马来酸酐已接枝在PP分子链上;PP-g-MAH的沉析及对KOH的包裹效应是接枝率测定误差大、再现性差的主要原因;酸碱滴定溶液浓度减小、取样量增大可减小测定误差,HCl-异丙醇溶液浓度为0.01 mol/L时可取得最小测定误差;所制备PP-g-MAH在HCl-异丙醇溶液浓度为0.01 mol/L、取样量为0.2 g时,测定接枝率的相对标准偏差为32%;所建误差模型可用于优化PP-g-MAH接枝率测试条件,减小测定误差.
为了解决聚甲醛(POM)导热性差的问题,在POM中加入了铜纤维(COF)和玄武岩纤维(BF),通过挤出-注塑工艺分别制备了POM/COF、POM/COF/BF复合材料;并利用ABAQUS软件验证了COF对POM导热性能的影响.结果表明,铜纤维使POM的热导率达到0.39 W/mK;在力学测试中,COF略微增加了POM的刚度,但却降低了POM的拉伸强度;随着BF含量的增加,POM/COF复合材料的热导率随之增加,在15%含量时达到最大,约为0.5 W/mK,比纯POM的热导率提高了约50%;同时BF的加入使POM的刚度大幅度增加,最大提高了约200%.通过ABAQUS稳态热传导仿真,发现含铜纤维的复合材料表面温度更低,热流更易通过纤维传递至低温区域.
用X射线衍射仪、元素分析仪和扫描电子显微镜等研究了微波脱除聚丙烯腈(PAN)薄膜中残留二甲基亚砜(DMSO)的工艺,分析了微波功率和处理时间对 DMSO的脱除效果、PAN薄膜的微观结构和力学性能的影响.结果表明,随着微波处理功率的提高或微波处理时间的延长,PAN中的DMSO残留量不断降低,PAN薄膜的结晶度呈先下降后上升的趋势,晶粒尺寸不断增加,PAN薄膜的微孔孔径显著减小,拉伸强度总体上升、断裂伸长率下降.经540 W的微波处理4 min后的PAN薄膜的拉伸强度达到21.36 MPa,较初始薄膜提升46.5%,PAN薄膜内部平均孔径减小,整体结构更加致密.
为了进一步改善纳米碳酸钙(nano-CaCO3)、废旧聚乙烯(WPE)单独改性沥青的成本及技术缺陷,本文通过三异硬脂酰基酞酸异丙酯(TTS)作为偶联剂,采取螺杆挤出造粒技术制得nano-CaCO3/TTS/WPE共混体系改性剂(CTW)及其改性沥青.重点研究了不同含量TTS对CTW改性沥青性能影响并对改性机理进行分析.结果表明,随着TTS含量的增加,CTW改性沥青软化点、延度、黏度先增大后基本保持不变,针入度变化则相反.动态剪切流变性及低温性能研究表明,一定含量的TTS有利于改善CTW改性沥青的高低温性能,同时对上述性能变化进行微观形貌及机理分析,可能的原因在于,不同含量TTS与nano-CaCO3/废旧聚乙烯/asphalt材料间物理、化学协同作用导致其性能变化.
以聚乳酸(PLA)为例,讨论异向双螺杆挤出机3种不同螺杆构型(阴阳转子螺杆头数比分别为2∶2、3∶2、4∶2)下的流道分布规律.依据理论端面曲线方程在Solidworks中创立上述3种不同螺杆构型的三维模型,使用Workbench软件对3种螺杆构型进行网格模型的建立,再使用Polyflow流体仿真软件进行模拟实际流场情况,得到后处理结果,使用后处理分析软件FieldView进行最终结果的分析;研究PLA流体的在不同螺杆构型下的压力、剪切速率以及黏度.同时使用Polystat统计模块对停留时间分布曲线RTD以及分布混合特性进行对比研究.结果表明,在螺杆转速为60 r/min和阳转子螺杆头数一定的条件下,随着阴转子螺杆头数的增加,压力波动减小,剪切作用提高,停留时间增加,分布效果提高,有利于材料的输出和混合.
