全水发泡阻燃聚氨酯硬质泡沫塑料的制备与性能

采用多元醇、异氰酸酯、催化剂、发泡剂和阻燃剂等为原料制备了全水发泡阻燃聚氨酯硬质泡沫(PURF),讨论了聚醚多元醇种类、催化剂、发泡剂、异氰酸酯指数以及阻燃剂对PURF性能的影响。结果表明,聚酯多元醇能够改善泡孔结构,但降低压缩强度和尺寸稳定性;不同催化剂复配,可以控制发泡工艺;水发泡剂与泡沫的密度、泡孔结构、力学性能有关;异氰酸酯指数在1.1～1.2时,泡沫的压缩强度、尺寸稳定性等较好;三(2-氯异丙基)磷酸酯(TCPP)可赋予PURF一定的阻燃性,但对泡体结构、压缩强度和尺寸稳定性有影响。     

PA6材料尺寸稳定性的影响因素

通过双螺杆挤出机熔融共混制备PA6材料,分析了环境湿度、成核剂、热处理对PA6材料尺寸稳定性的影响。结果表明,吸湿膨胀和内应力释放收缩共同影响PA6材料的尺寸变化,前者是主导因素;环境湿度越高、时间越长,PA6材料尺寸变化率越大,且在垂直流动方向上的尺寸变化率大于流动方向上的;随着成核剂用量的增加,PA6材料的尺寸变化率降低,用量为0. 5份时,尺寸稳定性最佳,成核剂用量继续增加,PA6材料尺寸变化率下降较小;热处理促进PA6材料内应力释放收缩,与吸湿膨胀相反,PA6材料的尺寸变化率明显降低;在相对湿度为50%的环境试验180 d,未添加成核剂、添加0. 50份成核剂、添加0. 50份成核剂热处理后的PA6材料在流动方向上的尺寸变化率分别为0. 39%、0. 33%、0. 21%,垂直流动方向上的尺寸变化率分别为0. 53%、0. 43%、0. 38%。     

浇口设计对塑件收缩规律影响的数值模拟

应用Moldflow分析工具,选用PP与ABS两种材料,以侧浇口填充方式,进行了不同浇口位置和尺寸对注塑成型收缩影响的数值模拟。模拟数据采用正交实验方法进行处理,并通过极差分析和贡献率的计算分析了各因素间的作用关系及其对成型收缩的影响规律。结果表明:不论哪种塑件结构,浇口位置变化始终是影响塑件成型收缩的主要因素;而塑件结构及浇口尺寸变化对成型收缩的影响依次减小。     

复合肥料的吸湿性及其影响因素

通过对复合肥吸湿性能的测定,得出各种配方复合肥的临界相对湿度,并对复合肥临界相对湿度与物料温度、原料成分之间的关系进行了研究,指出硝基复合肥的临界相对湿度受m(硝铵)/m(磷铵)的影响明显。     

注塑成型制件尺寸稳定性研究

材料吸湿性对制品尺寸的影响(4) 关于尺寸稳定性的研究我们已经讨论了造成制品尺寸变小的影响因素.但是也存在一些环境因素,它们使得制品的尺寸随着时间增加.其最好的例子是尼龙制品吸收空气中的水分时会出现的尺寸增大. 许多聚合物具有吸湿性,由于大气中总是存在水蒸气,因此这成为聚合物吸水的主要来源.在正常气候条件下许多吸湿性材料经过一定的时间可以吸收0.1％ ～ 0.2％的水分.但是对于尼龙材料来说,由于含有氢键,它吸水的程度更大.在相对湿度为35％～65％之间的"正常"环境室温条件下,未填充尼龙的平衡吸水量按重量计算大约在1.5％～2％之间.     

增强聚氨酯硬质泡沫塑料压缩性能研究

利用中空玻璃微珠和纳米二氧化硅作为增强剂,制备了增强聚氨酯硬质泡沫塑料(RPURF),对其压缩性能进行了研究,并在金相显微镜下观察了它的微观结构.实验结果表明,泡孔支柱处的增强剂加强了其承载能力,有利于压缩性能的提高;随着增强荆用量的增加,PURF压缩强度和模量先增加后降低,即增强剂用量处于最佳用量范围内时,PURF体现最好的压缩性能;并随着纯聚氨酯硬质泡沫塑料密度的增加,其压缩性能有显著的提高.     

单片(或双片)钢板弹簧的刚度计算

本文对宽度和高度按线性变化的单片钢板弹簧,导出了普遍的算式。文中指出,钢板弹簧的刚度取决于六个结构尺寸参数;利用所推荐的公式,当其中任一尺寸参数变化时,都能方便地算出相应的刚度值。文中利用这些算式列出了刚度值与诸尺寸参数间的关系曲线图,供设计钢板弹簧时参考使用。     

不同失水速率下膨胀土的开裂特性研究

含水率变化是导致膨胀土开裂的重要因素,其变化快慢影响了土体的裂隙发展.以某边坡膨胀土作为研究对象,自制了一套无干扰气候箱设备开展土体开裂试验,分析环境温度、相对湿度以及光照强度与薄层膨胀土失水速率之间的关系,通过数字图像技术对裂隙几何特征进行统计分析,定量研究了薄层膨胀土失水速率与蒸发及开裂特征参数的关系.结果表明:在...     

聚碳酸酯在高低温交变环境中的老化性能研究

为了探究温度变化对聚碳酸酯的影响,设计了三种温度交变环境,即55℃/-18℃之间快速交变、55℃/-18℃之间逐渐交变和45℃(相对湿度60%)/-18℃之间快速交变。研究了聚碳酸酯材料在这三种高低温交变环境中的结构、性能变化。结果表明:在30个温度循环周期内,在设计的三种温度交变环境中聚碳酸酯主要发生了物理老化。     

含磷和三聚氰胺阻燃体系的聚氨酯硬质泡沫的阻燃性能

以水稻秸秆液化物为聚醚多元醇,与多苯基多亚甲基异氰酸酯反应,制备聚氨酯硬质泡沫(PURF)。采用热重分析、残炭层表面分析、极限氧指数测定、傅里叶变换红外光谱与热重分析联用,探索了一系列磷系阻燃剂、三聚氰胺阻燃PURF的燃烧性能。结果表明:三聚氰胺可在残炭层中起到隔离作用;三聚氰胺与磷阻燃剂配合使用时,较单独使用的残炭层更完整,且可降低气体中可燃物的浓度,获得更好的阻燃效果。     

Synthesis and characterization of polyurethane rigid foams from polyether polyols with isosorbide as the bio-based starting agent

In this study, with the isosorbide as bio-based starting agent, a series of bio-based polyether polyols with different hydroxyl values were synthesized and used to prepare polyurethane rigid foams (PURF). The structures of as-synthesized polyols were studied by FT-IR and ¹H NMR methods. The thermal properties, mechanical properties, microscopic morphology, thermal conductivity and dimensional stability of PURF have been characterized by several physico-chemical and ASTM methods. The initial decomposition temperature T_5% and the maximum decomposition temperature T_max for PURF from isosorbide-based polyols with 458 mg KOH/g hydroxyl value are about 312 °C and 354 °C, improved 61 °C and 75 °C comparing with the PURF from 1,2-propanediol-based polyols. The maximum compressive strength of PURF from isosorbide-based polyols is 141 kPa, comparing with 118 kPa of PURF from 1,2-propanediol-based polyols. Meanwhile, the dimensional stability of PURF from isosorbide-based polyols has been improved twofold, and the water absorption was obviously reduced by 50%. All these results suggest that polyols of isosorbide-based starting agent should be promising feedstock for PURF with high performance.     

物理发泡水稻秸秆基聚氨酯泡沫研究

将水稻秸秆粉碎为粒径250~590 μm的粉末，利用成熟的催化常压加热液化技术将水稻秸秆粉末液化制得液化物，以其为原料，五甲基二乙烯三胺（PC5）和N，N-二甲基环己胺（PC8）为复合催化剂，正戊烷为发泡剂，与多苯基甲烷多异氰酸酯（PAPI）反应通过物理发泡法制备硬质聚氨酯泡沫（PURF）。另外采用全水发泡法制备了聚氨酯泡沫作为对比。对物理发泡制备PURF的条件进行了优化，较优的制备条件为催化剂中PC5和PC8的质量比4:5，泡沫稳定剂硅油B8462用量（以液化物质量计，下同）4%，发泡剂用量15%，该条件下制备的PURF的拉伸强度为347 kPa，压缩强度为181 kPa。采用傅里叶变换红外光谱（FT-IR）和扫描电镜（SEM）对比了物理发泡和全水发泡制得的泡沫，结果显示，通过物理发泡制得的水稻秸秆基聚氨酯泡沫相比于全水发泡聚氨酯泡沫，体系中异氰酸根浓度低，泡沫泡孔开孔率低，制得的泡沫力学性能略优。     

Influence of thermal behavior of phosphorus compounds on their flame retardant effect in PU rigid foam

Phosphorus‐containing compounds have been widely used as flame retardants for polyurethane rigid foam (PURF). In this work, a number of phosphorus compounds were utilized and studied as flame retardants for PURF, including ammonium polyphosphate, pentaerythritol phosphate, triethyl phosphate, and dimethyl methyl phosphonate. The thermal behavior of flame retardants was thoroughly investigated, such as degradation, vaporization, and the properties of degraded products. The influence of thermal behavior of phosphorus flame retardants on PURF was examined and analyzed. The results indicated that the effect of flame retardant was highly related to their thermal behavior. Phosphorus compounds for gas phase flame retardants were very effective in decreasing the heat release rate and increase limited oxygen index of PURF, while condensed phase flame retardants showed better comprehensive flame retardant effect, such as reducing the toxicity of combustion product. Copyright © 2015 John Wiley & Sons, Ltd.     

喷雾造粒ZrO2粉料坯体性能的研究

以喷雾造粒ＺｒＯ２粉料为研究对象,通过对粉料的压力－密度曲线及坯体的ＳＥＭ显微结构分析,发现喷雾造粒粉料的粒度分布对坯体密度的影响较小;颗粒强度的大小是获得均匀的坯体结构的关键,颗粒的强度与其大小及环境湿度有关,因此颗粒适当的增塑及去除大颗粒均有利于坯体显微结构的改善。     

非溶剂致相分离3D打印聚合物的成型工艺研究

采用自行搭建的湿度可控的气辅式三维（3D）打印机,基于非溶剂致相分离原理,实现了常温下、高精度、低成本3D打印耐高温的聚合物材料。以聚醚酰亚胺（PEI）为例,探究了挤出压力、喷头直径、打印速度、打印环境相对湿度、打印层高等打印参数对成型质量的影响。结果表明,挤出丝料的宽度与打印速度、环境相对湿度有关,随打印速度和环境相对湿度的增大而减小;打印层高与挤出丝料的厚度有关,打印层高约等于挤出丝料的厚度的时,成型质量最好;通过多层沉积实验,得到最优的打印参数,成型了表面质量良好、精度高的PEI坯体。     

Observations on Finger-like Crack Growth at a Urethane Acrylate/Glass Interface

Interfacial crack growth behavior along a urethane acrylate/glass interface is characterized by the development of finger-like perturbations along the advancing crack front. The finger-like perturbations grow from a slightly irregular crack front until they reach a steady-state where the velocity of the finger tips equals the velocity of the finger valleys. Once the fingers reached steady-state, the crack velocity was dependent on the applied strain energy release rate via a power law relationship where the exponent was independent of test humidity; however, the multiplicative constant A decreased by an order of magnitude from 80 to 15% RH. The spacing of the fingers was found to be independent of the crack's velocity and the relative humidity of the environment.     

Observations on Finger-like Crack Growth at a Urethane Acrylate/Glass Interface

Interfacial crack growth behavior along a urethane acrylate/glass interface is characterized by the development of finger-like perturbations along the advancing crack front. The finger-like perturbations grow from a slightly irregular crack front until they reach a steady-state where the velocity of the finger tips equals the velocity of the finger valleys. Once the fingers reached steady-state, the crack velocity was dependent on the applied strain energy release rate via a power law relationship where the exponent was independent of test humidity; however, the multiplicative constant A decreased by an order of magnitude from 80 to 15% RH. The spacing of the fingers was found to be independent of the crack′s velocity and the relative humidity of the environment.     

盐湖老卤蒸发气候条件研究与蒸发模型建立

通过开展环境气候条件实验研究,揭示环境气候主要参数大气湿度和老卤蒸发速度之间的关系,建立了老卤蒸发模型,并利用模型推算出老卤自然蒸发的大气相对湿度极限值为33.2%。实验证明蒸发环境大气相对湿度小于该值时老卤将会自然蒸发,大于该值时不但不蒸发,还将倒吸空气中的水分。利用本研究蒸发数学模型,可以预测盐湖气候季节变化过程中老卤蒸发情况,为合理设计老卤蒸发方案提供科学依据。     

Charpy impact fracture testing—a precise measure of ductile-brittle transition in a filled polymeric system

The fracture toughness of a filled nitrile rubber/phenolic polymeric system was assessed by means of ductile-to-brittle transition temperature (DBTT) as measured by the Charpy impact method to search for sampling location dependencies of toughness in structures. This investigation established the relationship between the Charpy DBTT and exposure to selected relative humidity (RH) for the filled polymer from the three lots. Charpy fracture tests of specimens subjected to a low RH environment (15 percent) had higher DBTTs than their counterparts exposed to a high RH condition (70 to 75 percent). Charpy specimens of this material exhibited a 9 to 22°F change in DBTT which depended upon the manufacturer and the conditioning period for a corresponding change of 60 percent RH. The change in DBTT with relative humidity was found to be reversible; initial fracture behavior could be restored to samples from the low RH (15 percent) station by equilibrating at a high RH (75 percent) level.