木粉/PHBV复合缓冲材料的制备及性能表征

目的 制备一种缓冲性能优异的木粉/聚β–羟基丁酸戊酸酯(PHBV)复合缓冲材料,作为缓冲包装材料用于运输包装领域。方法 选用马来酸酐接枝聚丙烯(MAPP)作为偶联剂,选用碳酸氢钠(NaHCO3)和偶氮二甲酰胺(AC)作为发泡剂,采用共混热压工艺制备毛白杨木粉和聚(β–羟基丁酸戊酸酯)(PHBV)复合材料,进行力学性能和缓冲性能测试,并通过扫描电子显微镜(SEM)、傅里叶红外光谱(FT–IR)、差示扫描量热法(DSC)等进行性能表征,分析讨论不同木塑比、发泡剂种类和添加量对木塑复合缓冲材料微观界面、缓冲性能的影响。结果 研究结果表明,当木粉与PHBV质量比为6∶4时木塑复合材料的缓冲性能、吸收能量和热性能最佳,NaHCO3发泡剂和AC发泡剂质量分别为2.0 g和1.5 g时,泡孔多且均匀,与木纤维交织连接形成稳定连续的泡孔结构,受压时不会出现应力集中点,吸收能量分别提高了34.6%和33.8%,加入适量发泡剂熔融焓分别提升了43.74%和41.83%,其中加入AC发泡剂材料的结晶率明显提高。结论 当木粉与PHBV质量比为6:4,NaHCO3发泡剂和AC发泡剂质量分别为2.0 g和1.5 g时,制备得到的木粉/PHBV复合材料具有优异的缓冲性能,在运输包装领域具有潜在的应用前景。     

以AC发泡剂为添加剂燃烧合成α-Si3N4粉体

以硅粉和Si3N4粉体为反应剂,偶氮二甲酰胺(AC发泡剂)为添加剂,利用燃烧合成技术在较低氮气压力下制备了高α相含量的Si3N4粉体.采用X射线衍射和扫描电镜分别对产物的物相组成及显微结构进行了表征,研究了AC发泡剂对α相Si3N4粉体的形成和产物颗粒形貌的影响.结果表明,AC发泡剂能促进硅粉快速氮化,产物中α-Si3N4的含量随着AC发泡剂添加量的增加而增加.当AC发泡剂的添加量为24wt%时,产物中α-Si3N4的含量高达85.2wt%.对AC发泡剂作用下的燃烧合成Si3N4的反应机理做了初步探讨,研究表明:AC发泡剂的分解产物N2、CO、NH3不仅增加了坯体的透气性,而且改变了燃烧反应的传热和传质路线,从而促进了硅粉快速氮化和α-Si3N4粉体的生成.     

硬质聚氯乙烯用复合发泡剂的研究

采用活化剂(尿素、碳酸锌)和碳酸氢钠对偶氮二甲酰胺(AC)改性制备硬质聚氯乙烯(R-PVC)用复合发泡剂,并用热分析和放气量检测对复合发泡剂进行了表征。结果表明当AC、NaHCO3、尿素和碳酸锌的质量比为10:10:2.5:2.5时所得的复合发泡剂分解温度处于R-PVC成型加工范围内,吸-放热基本平衡,放气量大且无突发性。采用这种复合发泡剂制备的硬质聚氯乙烯发泡材料具有较好的力学性能和微孔结构。     

HDPE微发泡塑木复合材料的制备及其性能研究

以废旧高密度聚乙烯(HDPE)、木粉为主要原料,采用模压法制备了HDPE微发泡塑木复合材料,研究了木粉粒径、交联剂添加量、AC发泡剂添加量对HDPE微发泡塑木复合材料性能的影响,结果表明:随着木粉粒径增加,材料的密度逐渐增大,木粉粒径为106μm,交联剂的用量为1.5%时复合材料的物理性能较好,且随着AC发泡剂用量的增大,材料的力学性能和密度都逐渐降低,当AC发泡剂用量超过0.7%时,材料力学性能降低幅度增大。     

硅泡沫材料发泡体系的研究

对发泡剂NaHCO3、OBSH、H、AC 4种典型的无机及有机发泡剂进行了示差扫描量热分析及热失重分析,了解其热分解温度.分析了发泡剂H与发泡助剂季戊四醇、发泡剂AC与发泡助剂尿素之间的协同效应以及OBSH,H与季戊四醇,AC与尿素3种发泡体系与树脂交联体系的匹配性关系,结果表明,季戊四醇可有效地调节发泡荆H的分解温度与分解速度且H与季戊四醇发泡体系能和树脂交联体系呈现最好的匹配性,促进发泡工艺,稳定泡体结构及质量.     

化学发泡剂含量对秸秆纤维/聚丙烯复合材料性能的影响机理

目的 揭示发泡剂含量对微发泡注塑成型秸秆纤维/聚丙烯复合材料(SF/PP)密度及力学性能的影响规律,提供制备低密度高性能SF/PP材料的发泡剂用量工艺参考。方法 以偶氮二甲酰胺(AC)为化学发泡剂,制备了注塑发泡SF/PP,利用扫描电子显微镜、电子万能实验机和红外光谱测试等手段,分析了不同发泡剂含量下SF/PP的拉伸、弯曲、冲击性能、泡孔微观形貌和分布以及复合材料红外光谱图,通过实验对比分析了不同发泡剂含量下材料性能的变化规律。结果 当AC含量增加时,微发泡SF/PP的密度先降低后升高,冲击强度则先升高后降低,拉伸和弯曲强度为逐渐降低。当AC的质量分数为4%时,微发泡SF/PP的综合性能最佳,泡孔结构最好;微发泡(SF/PP)红外光谱图结果显示,在3420cm^-1处的—OH伸缩振动峰强度高于未发泡复合材料的,这表明秸秆纤维表面极性增大,秸秆纤维与树脂之间的结合性变差,导致微发泡SF/PP的拉伸强度低于未发泡材料的。结论 适当增加AC含量可使复合材料获得微小、致密的泡孔微观结构,降低材料密度,提升产品的力学性能;但当AC含量过多时,泡孔坍塌会使泡孔直径增大、泡孔结构...     

镁合金表面TaC/TaC-Mg/Mg梯度涂层的 残余热应力分析

采用间歇式挤出发泡工艺制备淀粉/PVA复合发泡材料。在淀粉含量固定、甘油作为增塑剂的情况下,研究偶氮二甲酰胺（AC发泡剂）与聚乙烯醇（PVA）的含量对发泡材料的表观密度、发泡倍率、相对硬度、吸水性能、回弹性能以及压缩性能等的影响。结果表明：随着PVA含量的升高,复合材料的表观密度和压缩模量减小,回弹性能变好。PVA含量对吸水率影响不明显,吸水率稳定在20%左右。吸水至饱和状态后,相对硬度随着PVA含量的增加而不断增加。随AC发泡剂含量的升高,复合材料的表观密度减小,相对硬度降低,发泡倍率和回弹率增加,材料的泡孔孔径逐渐增大但是发泡孔径的均匀性变差。当PVA、AC发泡剂的添加质量分数分别为30%, 1%时,复合材料性能最优。     

发泡剂含量对双马来酰亚胺泡沫泡孔结构和性能的影响

以偶氮二甲酰胺(AC)为发泡剂,采用预聚、发泡的两步法制备双马来酰亚胺泡沫,研究AC含量对泡沫泡孔结构、密度、尺寸稳定性温度和压缩性能的影响。结果表明:可通过发泡剂用量的改变实现泡沫密度在60~280kg/m3范围内调整,发泡剂用量对泡孔尺寸及其均匀性影响较小。随发泡剂用量降低,尺寸稳定性温度和压缩性能提高,当泡沫密度为280kg/m3时,尺寸稳定性温度可达220℃,压缩强度和模量分别为4.8MPa和200MPa,满足结构泡沫的耐温性能和力学性能要求。     

玉米秸秆缓冲包装材料的研制及性能测试

研究了以玉米秸秆和氧化淀粉为主要原料制备植物纤维发泡制品的工艺.结果表明:氧化淀粉是合适的粘合剂,发泡温度应控制在70～100℃,适合的秸秆用量为20%～30%,发泡剂用量为10%左右时,制品经性能测试具有良好的实际使用性能.     

双马来酰亚胺泡沫泡孔结构研究

研究了几种有机发泡剂偶氮二甲酰胺(AC),4,4 ′-氧代双苯磺酰肼(OBSH)和二亚硝基五亚甲基四胺(H)的热分解特性,用扫描电镜(SEM)表征了各种发泡剂对双马来酰亚胺(BMI)泡沫孔径的影响.结果表明,与单一发泡剂相比,通过发泡剂AC/H,AC/OBSH之间的复配可以优化泡孔结构,改善成型工艺性.树脂预聚程度是控...     

AC／ZnO发泡剂系对植物纤维增强淀粉复合发泡材料性能的影响

用偶氮二甲酰胺（AC）／氧化锌（ZnO）作为发泡剂系制备植物纤维增强淀粉复合发泡材料并讨论其含量对该材料性能的影响。通过TGA曲线确定偶氮二甲酰胺（AC）／氧化锌（ZnO）的最佳比例为2：1;在温度为25℃,RH-50％的环境下保持7d,通过力学性能检测,该材料具有良好的拉伸强度和断裂伸长率,分别为6．38MPa、91...     

典型放热型、吸热型和吸-放热型发泡剂热分解特性的研究

研究了典型的放热型发泡剂ＡＣ、吸热型发泡剂ＨＹＤＲＯＣＥＲＯＬ ＢＩＨ和吸放热型发泡剂ＥＸＯＣＥＲＯＬ２３２分解热力学和动力学特性,用ＤＳＣ差示扫描量热仪测定了动态分解温度和热效应以及发泡助剂对分解热力学的影响。并用自行设计的发泡剂的改进提供了参考数据。     

发泡石头纸的制备和性能检测

在石头纸粒料中分别加入质量分数为0.1%,0.4%和0.7%的AC发泡剂,经过高速冷混、熔融混合后,从挤出机挤出预发泡纸膜,再经过热压使纸膜发泡,冷切后分别制得了厚度增加倍率为0.4,0.2和0.8的发泡石头纸。通过扫描电镜对发泡石头纸表面结构和横截面结构进行了观察,发现石头纸表面有微孔结构,石头纸内部的微孔结构规整,其孔壁在发泡产生的气体压力下被拉伸,随着发泡剂量的增加这种拉伸现象越明显。研究表明:发泡石头纸的密度比普通未发泡石头纸减小了16%～30%;石头纸中AC发泡剂质量分数为0.1%时,发泡石头纸的物理性能增强,质量分数为0.4%和0.7%时,其物理性能有所下降。     

Moulded polypropylene foams produced using chemical or physical blowing agents: structure–properties relationship

Polypropylene (PP) foams have become essential items due to their excellent properties. Nevertheless, obtaining net-shaped PP foams with medium relative densities is a complicated issue. In this article, two processes able to produce moulded PP foams in this density range are presented. One of them is based on a modification of the pressure quench foaming method and therefore uses a physical blowing agent (CO₂). The second one is the improved compression moulding technique which uses a chemical blowing agent (azodicarbonamide). PP foams with relative densities in the range between 0.25 and 0.6 and cylindrical shape were prepared using these foaming techniques. A common PP grade (instead a highly branched one) was used to obtain the samples, showing, that by combining the appropriate foaming technique, the adequate moulds, suitable blowing agent and proper foaming parameters, net-shaped PP foams with excellent properties can be produced starting from a conventional PP grade. Samples were characterized by analyzing their cellular structure and their mechanical properties. Results have showed that depending on the chosen foaming route isotropic or anisotropic structures with cell sizes ranging from 40 to 350 μm and open cell content in the range between 0 and 65% can be obtained. Moreover, mechanical properties are highly influenced by the production route and chemical composition of the foams. For instance, the stiffer materials at relative densities higher than 0.4 are the ones produced using the chemical blowing agent while at relative densities lower than 0.4 are the ones produced using the physical blowing agent.     

部分动态预硫化对EPDM发泡行为的影响

采用部分动态预硫化工艺制备三元乙丙橡胶(EPDM)发泡材料,即通过在哈克中动态预硫化来控制橡胶预交联,然后混入相同的硫化和发泡剂体系并制得发泡材料。研究了部分动态预硫化对EPDM凝胶含量及发泡行为的影响。结果表明,动态预硫化过程中,随硫磺用量增加,其最终平衡扭矩升高,预硫化混炼胶的凝胶含量增加;硫化和发泡行为测量表明,动态预硫化并未影响EPDM混炼胶二次硫化速度以及发泡剂分解速度;扫描电镜(SEM)显示,预硫化阶段硫磺用量为0.0125phr时的试样,能获得较好的泡孔结构和较低的密度,表明适量的预硫化能明显改善EPDM混炼胶的发泡行为。     

发泡剂对聚乙烯/废纸复合发泡材料的影响

选择偶氮二甲酰胺作为发泡剂,研究结果表明:在复合材料中发泡剂对其质量影响最大,随着发泡剂用量的增加,所得材料的密度、硬度及拉伸强度呈下降趋势,而断裂伸长率则逐步上升.     

Influences of particle sizes and contents of chemical blowing agents on foaming wood plastic composites prepared from poly(vinyl chloride) and rice hull

This research aims to investigate the effects of chemical blowing agent (CBA) contents and particle sizes on the properties of foamed poly(vinyl chloride) (PVC)/rice hull (RH) composites. Fine particles of azodicarbonamide (AC) at 5, 8, 11 and 22 μm were modified with 20% by weight of ZnO and used at 0–3.0% by weight. The average cell size and density of the PVC/RH foamed profiles were reduced as the content of modified azodicarbonamide (mAC) increased. Larger mAC particles lowered the density more effectively. Maximum reduction of density by 46% was achieved when mAC 22 μm was applied at 2.0% by weight. Larger blowing particles led to PVC/RH foam with greater flexural modulus and strength. Greater impact strength, observed when 5 μm mAC was applied, resulted from the rather thick cell wall created abundantly when fine mAC was applied.     

甲醛湿式氧化催化剂的制备及性能研究

用FTIR和N2吸附法对活性炭进行表面分析,通过原子吸收光谱考察了铜在活性炭表面的吸附行为,制备了几种甲醛湿式氧化的催化剂,对比研究了它们在常温常压下对甲醛氧化的催化性能。结果表明,活性炭氧化改性后表面含氧基团增加,对铜和甲醛的吸附性能提高。活性炭表面负载的铜、银、铁对甲醛湿式氧化都有一定的催化能力,其中栽铜活性炭的催化效果最好,载铁活性炭的催化性能优于载银活性炭,催化动力学曲线表明,氧化改性后,载铜活性炭的催化性能进一步提高。     

Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity

To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.     

The effect of blowing agent choice on energy use and global warming impact of a refrigerator

A study, comparing the effect of blowing agent selection on energy consumption and the life cycle climate performance (LCCP) of a typical European refrigerator is discussed. Energy consumption of prototype European-style refrigerators made with a foam formulation with HFC-245fa as the blowing agent was measured and compared with energy consumption of the same model as currently produced (using a foam with a pentane blend for the blowing agent). Results were used in a LCCP study, considering both direct and indirect climate impacts due to blowing agent emissions and energy consumption in manufacturing processes and over the life cycle of the refrigerator. An assumption is made that the refrigerator is built and used in the European market.