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采用偶氮二甲酰胺(AC)做为发泡剂,直接通过挤出过程制备聚乳酸(PLA)泡沫塑料,通过显微镜照片、HAKKE流变仪观察和研究了工艺条件对其泡孔结构的影响。结果表明,发泡剂与成核剂的增加能降低发泡PLA的表观密度,增加其泡孔密度。流变试验表明纯PLA与发泡PLA熔体在低剪切速率下都呈现剪切变稀现象,发泡后PLA熔体的黏度会下降10%~30%。发泡剂含量在4%以下时,泡孔直径随发泡剂含量增加而减小;发泡剂含量增加到5%及以上时,PLA熔体强度过小,泡孔会过于密集而导致塌陷和串泡。成核剂的加入能够明显降低PLA熔体强度,异相成核使得泡孔直径较均相成核大,但前者泡孔密度较后者小。 相似文献
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改性聚乙烯醇体系熔体的流变性能 总被引:7,自引:0,他引:7
采用HAAKE RHEOCORD-90挤出式毛细管流变仪测定了改性PVA体系的流变性能。结果表明,改性PVA熔体是对剪切速率敏感的假塑性流体,非牛顿指数n较小,熔体偏离牛顿流体的程度较大。在相同温度及剪切速率下,随水含量增加,改性PVA体系的表观粘度下降。改性PVA体系的粘流活化能随剪切速率提高和水含量减少而降低,即温度敏感性降低。 相似文献
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采用密炼机制备了聚苯乙烯(PS)和聚对苯二甲酸乙二醇酯1,4环己二甲醇酯(PETG)共混物;以超临界二氧化碳(CO2)为物理发泡剂,采用釜压法制备了PS和PS/PETG共混物发泡试样。通过旋转流变仪、扫描电子显微镜对PS和PS/PETG共混物的流变性能和泡沫的泡孔形态进行了表征。结果表明,加入PETG没有对PS的流变性能产生明显的影响,但对PS泡沫的泡孔形态影响显著,加入10 %的PETG时,其平均泡孔直径由纯PS的2268 μm降至758 μm,泡孔密度由345×108个/cm3提高到447×109个/cm3,泡孔尺寸分布明显变窄,说明PETG在PS中起到明显的气泡成核作用。 相似文献
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以聚乳酸(PLA)为基体,加入不同含量的塑化聚乙烯醇(CPVA),通过熔融共混法制备PLA/CPVA合金样品。以超临界CO2为物理发泡剂,采用釜压发泡和粒子沥滤法成功制备出PLA/CPVA合金开孔泡沫。结果表明,随着CPVA含量的增加,PLA的结晶温度下降,结晶度先上升后下降,熔体黏弹性改善;随着CPVA含量的上升,PLA/CPVA合金开孔泡沫的发泡倍率先减小后逐渐增大,开孔率逐步提高;当CPVA含量为50%(质量分数,下同)时,PLA/CPVA合金开孔泡沫的发泡倍率为23.1倍,开孔率达到了91.6%。 相似文献
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将废旧瓦楞纸板粉碎制浆,与HDPE(高密度聚乙烯)通过模压成型制备了废纸浆/HDPE发泡复合材料。利用英国Rosand双料筒毛细管流变仪,在线研究了发泡剂AC含量、废纸浆含量、温度以及吸热、放热和平衡发泡剂对废纸浆/HDPE复合发泡材料的流变行为的影响,并在SEM下观察了不同AC含量和废纸浆含量对发泡形态的影响。结果表明:废纸浆/HDPE复合发泡材料熔体表现为假塑性流动特征,当剪切速率达到600 s-1时,出现管壁滑移现象。发泡剂AC能明显降低熔体黏度,随着AC含量的增加,熔体黏度下降。随着废纸浆含量的增加,熔体黏度增加。当剪切速率小于275 s-1时,随着温度的升高,熔体黏度降 相似文献
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Hyun Ju Lim Sung Jun Lee Han Jo Bae Seok Kyun Noh Yong Rok Lee Sung Soo Han Han Yong Jeon Won Ho Park Won Seok Lyoo 《应用聚合物科学杂志》2007,106(5):3282-3289
The effects of tacticities on the characteristics of poly(vinyl alcohol) (PVA) nanowebs prepared by an electrospinning technique were investigated. PVA webs composed of uniform nanofibers with syndiotactic dyad (s‐dyad) contents of 53.5 and 57.3% were successfully obtained with electrospinning. By changing processing parameters such as the initial polymer concentration, applied voltage, and tip‐to‐collector distance, we found suitable conditions for forming PVA webs with uniform nanofibers. PVAs of higher s‐dyad contents were prepared at a lower solution concentration and at a higher applied voltage because of the easy formation of syndiotactic PVA chain entanglements at a very low polymer concentration. The average diameter of the nanofibers in a PVA web with the higher s‐dyad content of 57.3% (ca. 240 nm) was thinner than that of the nanofibers in a PVA web with the lowers‐dyad content of 53.5% (ca. 270 nm). In addition, the crystallinity and thermal stability were greatly increased with an increase in the s‐dyad content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
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The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology
Stephen Ormondroyd 《Polymer International》1988,20(4):353-359
The requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems. After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co-suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences. 相似文献
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Shivshankar Chaudhari YongSung Kwon MyungJun Moon MinYoung Shon SeungEun Nam YouIn Park 《应用聚合物科学杂志》2017,134(48)
Blended membranes of hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(vinyl amine) (PVAm) were prepared and crosslinked with glutaraldehyde. The prepared membranes were characterized using infrared (attenuated total reflection mode) spectroscopy, differential scanning calorimetry, X‐ray diffractometry, and scanning electron microscopy measurements. Pervaporation performances of the membranes were evaluated for the separation of water‐isopropanol (IPA) mixtures. As the PVAm content increased from PVAm0 to PVAm1.5, the flux through a 70 μm film increased from 0.023 to 0.10 kg/m2 h at an IPA/water feed ratio of 85/15 at 30 °C. The driving force for permeation of water increased due to the temperature but it has no effect on IPA permeation. Activation energies for the permeation of IPA and water were calculated to be 17.11 and 12.46 kJ/mol, respectively. Controlling the thickness of the blend membrane could improve the permeation flux with only a marginal reduction in the separation factor. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45572. 相似文献
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聚乙烯醇薄膜的共混改性 总被引:1,自引:0,他引:1
从聚合物结构方面分析了聚乙烯醇(PVA)薄膜的水溶性,提出用共混改性方法提高PVA薄膜的溶解性能。研究了聚丙烯酸不同中和度,不同共混组分组成对薄膜水溶性和力学性能的影响,并利用差示扫描量热法(DSC)、傅立叶红外光谱(FTIR)、广角X射线衍射(WXRD)等手段对共混改性机理进行了分析。 相似文献
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肝素化聚乙烯醇性能研究 总被引:1,自引:0,他引:1
用聚乙烯醇(PVA)缩醛化方法,共价键结合肝素。用Schiff试剂染色法、红外光谱分析、X射线光电子能谱法(ESCA)、元素分析等测试方法证明醛基和肝素的存在。力学性能测定表明,肝素化聚乙烯醇的拉伸强度达到12 25MPa,断裂伸长率为400%。生物学指标说明,在全血凝固时间实验(CT)中,肝素化聚乙烯醇的抗凝时间达3h,在活性部分凝血时间实验(APTT)中,缩醛化聚乙烯醇共价键结合肝素非常牢固,没有肝素脱落到血液中,证明肝素化聚乙烯醇具有显著的抗凝血性。 相似文献
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Poly(vinyl alcohol) modified with carboxylic acid anhydrides: crosslinking through carboxylic groups
The reaction of carboxylic acid anhydride with poly(vinyl alcohol) (PVA) leads to vinyl alcohol—vinyl ester copolymers which contain carboxylic acid groups. Esterification enables degrees of modification to be reached which depend on the chemical structure of the anhydride introduced and the ratio of the reagents in the feed. The copolymers obtained were characterized by spectroscopic techniques, elemental analysis, and thermal methods. These half-esters reacted in a second step with aromatic diglycidyl ethers to obtain tridimensional networks. This crosslinking reaction through the carboxylic groups was studied by differential scanning calorimetry. The water absorption of the linear and crosslinked polymers was determined gravimetrically as a function of time at room temperature. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1643–1651, 1997 相似文献
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Effects of individual and composed poly(vinyl alcohol) (PVA) suspending agents on the particle morphology of poly(vinyl chloride) (PVC) resins were investigated and discussed in the view of PVA absorption at the oil/water interface and interfacial behavior. It was shown that the percentage and surface coverage of PVA at the oil/water interface decreased with the increase of the degree of hydrolysis (DH) of PVA in the DH range of 70–98 mol %, while the interfacial tension of VC/PVA aqueous solution increased linearly with the increase of DH of PVA. PVC resin with more regular particle shape, increased agglomeration and fusion of primary particles, lower porosity and higher bulk density, was prepared by using PVA with a higher DH as a suspending agent. This was caused by the occurrence of drop coalescence at the very early stage of VC polymerization, the increase of particle shrinkage, and the lower colloidal protection to primary particles. It was also shown that the interfacial tension of VC/water in the presence of composed PVA suspending agents varied linearly with the weight composition of the composed PVA suspending agents. The particle properties of PVC resin prepared by using the composed PVC suspending agents were usually situated in between the properties of PVC resins prepared by using the corresponding individual PVA suspending agent. The particle morphology and properties of PVC resin could be controlled by the suitable choice of the composed PVA suspending agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3848–3855, 2003 相似文献
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聚乙烯醇改性及降解研究进展 总被引:3,自引:0,他引:3
从材料学的改性技术和环境学的相容性两个角度综述了国内外聚乙烯醇生物降解的研究概况。通过聚乙烯醇溶液及薄膜的降解过程的介绍,指出化学改性和微生物降解的结合将是今后处理含聚乙烯醇类废水和固体废弃物的主要方法。 相似文献