增塑聚碳酸酯片材的模压法微孔发泡研究

采用磷酸三甲酚酯(TCP)对聚碳酸酯(PC)片材进行增塑,并采用模压法对所增塑的PC片材进行微孔发泡,探讨了加工参数和TCP用量对PC片材泡孔结构的影响。结果表明:TCP对PC具有良好的增塑效果,制得的微孔塑料具有理想泡孔结构,且拓宽了发泡温度范围;增塑PC片材的泡孔结构随发泡压力、发泡时间、发泡温度的变化趋势与未增塑PC片材的变化趋势保持一致,只是泡孔尺寸、泡孔密度发生了一定程度的变化;随TCP含量的增加,泡孔尺寸先减小后增大,泡孔密度的变化趋势则相反。     

微孔塑料挤出成型的研究

以超临界CO2作为物理发泡剂,对低密度聚乙烯(LDPE)进行了微孔发泡的研究。介绍了微孔塑料成型过程中聚合物/气体均相体系的形成、气泡成核和气泡长大及定型这三个步骤。并分析了加工工艺因素(温度、压力)等对制品中泡孔尺寸和密度的影响:泡孔直径随挤出压力的增加而减小;泡孔密度随压力的增加而增加;泡孔直径随压力降速率的增大而减小;泡孔密度随压力降速率的增大而增加;而适当提高温度有利于减小泡孔直径、增加泡孔密度。     

ABS微孔发泡材料气体扩散行为分析

采用化学交联模压法制备了丙烯腈-苯乙烯-丁二烯共聚物(ABS)微孔发泡材料,研究了发泡温度、发泡压力及发泡时间对ABS微孔发泡材料气体的扩散行为及泡孔结构的影响,结果表明:气体吸收量随着发泡温度、发泡压力和发泡时间的增加,先增大后减小;随着气体吸收量的增加,制品的泡孔尺寸逐渐减小,泡孔密度逐渐增大,增加气体吸收量有利于提高发泡效果。当发泡温度为170℃、发泡压力为10 MPa、发泡时间为12min时,泡孔密度约为2.87×108个/cm3,可满足工业上微孔发泡材料泡孔密度的要求。     

微孔聚碳酸酯的制备工艺与泡孔结构研究

使用超临界CO2流体作为发泡剂在不同条件下制得一系列微孔聚碳酸酯(PC)。通过扫描电子显微镜观察分析了各种制备工艺参数对微孔PC泡孔结构和分布的影响。结果表明,饱和阶段的时间超过3.5 h时,试样中的CO2基本达到饱和;饱和阶段压力的增加会使泡孔直径减小,泡孔密度增大;而发泡温度的增加和发泡时间的延长则会使泡孔直径增大,泡孔密度减小。当完全发泡时,试样的泡孔结构在厚度方向上有明显区别:试样表皮部分未发泡,有致密的表皮结构;试样表层附近泡孔直径较小,泡孔密度较大;试样中心处的泡孔直径较大,泡孔密度较小。     

工艺参数对PC塑料泡孔结构影响

采用自制的微孔发泡模拟机研究了温度和压力以及气体饱和时间对微孔聚碳酸酯（PC）泡孔结构的影响。结果表明，对于微孔PC泡沫塑料的成型存在一个最佳温度值;随着饱和压力升高，泡孔直径变小，泡孔的密度增大；气体饱和时间对PC泡沫塑料泡孔结构的影响不是很明显，在一定的饱和时间范围内，延长PC发泡时间有利于得到更均匀的泡孔结构。     

发泡工艺对超临界CO_2/PLA微孔发泡泡孔形态的影响

研究了超临界CO2/PLA微孔发泡过程中,发泡温度、饱和压力、剪切速率对聚合物PLA泡孔形态的影响。结果表明,发泡温度对泡孔形态影响很大,温度降低,熔体强度增加,泡孔塌陷和合并减少,发泡材料的泡孔密度增大,泡孔尺寸减小,但温度太低时,熔体黏度和表面张力增加,发泡样品泡孔密度较低,泡孔壁较厚;压力对发泡形态的影响也是很显著的,压力太低,CO2的溶解度小,泡孔壁厚,泡孔分布不均匀。随着压力升高,CO2的溶解度增加,发泡样品的泡孔密度增加,泡孔更加均匀;随着转子转速增加,泡孔尺寸减小,气泡成核密度增大。但是转子转速过快,泡孔沿剪切的方向被拉长,泡孔取向严重,泡体质量变差。     

模压成型ABS微孔发泡材料的研究

采用化学交联模压法制备了丙烯腈-苯乙烯-丁二烯共聚物(ABS)微孔发泡材料,研究了发泡温度、发泡压力、发泡时间等加工参数对泡孔性能的影响,采用力学测试方法、扫描电子显微镜(SEM)研究了ABS微孔发泡材料的力学性能和泡孔形态。研究结果表明,当发泡温度为170℃、发泡压力为10 MPa、发泡时间为12 min时,制得的ABS微孔发泡材料泡孔尺寸、泡孔密度适中,表观密度最小,同时具有较好的冲击强度。在此模压工艺参数下,材料的平均泡孔直径约为50μm,泡孔密度约为3.2×108个/cm3,满足工业上微孔发泡材料泡孔密度的要求。     

片材口模尺寸对聚丙烯挤出发泡影响的研究

自行设计加工不同几何尺寸的片材口模,进行挤出发泡实验,并重点讨论口模尺寸对聚丙烯发泡材料性能的影响。结果表明,在口模流道宽度与高度一定的条件下,随着流道平直段长度的增加,机头压力增大、机头压降速率减小;当机头压力及压降速率较大时,发泡样品的表观密度较小、泡孔尺寸较小,泡孔均匀性较好。     

加工参数对PP／木粉复合材料结构和性能的影响

将聚丙烯(PP)与处理木粉混合,经双螺秆挤出机适粒后·混入微扎发泡母粒,经单螺杆挤出机塑化和片材口模成型PP/木粉复合微孔片材试样.通过改变挤出温度、螺杆转速、口模压力降以及冷却定型条件,测定试样拉伸性能、密度、孔隙率,扫描电镜(SEM)观察试样断面形貌,研究加工参数与PP/木粉复合微孔片材结构和性能的关系.结果发现,在挤出温度180℃,螺杆转速50 r/min,高的挤出压力时,泡孔尺寸小而均匀.对片材坯料给予的冷却定型可以固定泡孔结构防止泡孔合并和过度生长及塌陷.     

超临界CO2制备微孔聚碳酸酯及其泡孔特性研究

采用超临界微孔发泡技术制备出一系列聚碳酸酯微孔泡沫塑料,通过扫描电子显微镜、密度测试等方法研究了发泡温度和发泡时间对聚碳酸酯微孔泡沫塑料泡孔特性和体积密度的影响。结果表明,在测试范围内,随发泡温度的升高,泡孔密度增加,泡孔孔径先增加后降低,体积密度降低;随发泡时间的增加,泡孔密度和孔径均增加,体积密度降低。     

Preparation and characterization of microcellular thin polycarbonate sheets

A new method was developed for the microcellular processing of polycarbonate (PC) thin sheets by compression molding above PC's glass‐transition temperature and below its melting temperature within a few minutes. The effects of the foaming time, foaming pressure, foaming temperature, and foaming agent active ratio on the cell size, cell density, and relative density were studied. The structures of the microcellular PC foam were controlled in the foaming process by carefully choosing the foaming parameters. In addition, the thermal, dynamic mechanical thermal, and electrical properties of the microcellular PC foam were investigated. A differential scanning calorimetry analysis showed that the microcellularly processed PC may have a plastication effect. The variation of the storage modulus, loss modulus, and tan δ under dynamic mechanical thermal analysis was in accord with the calorimetry analysis. The measurement of the electrical property demonstrated that the insulation ability of the microcellular PC thin sheet was obviously enhanced and the dielectric strength of the microcellular PC foam was decreased compared to the unfoamed PC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1760–1766, 2006     

Cell structure and impact properties of foamed polystyrene in constrained conditions using supercritical carbon dioxide

To obtain cellular with small cell diameter, to control cell structure and to improve impact strength of foaming materials, the quick-heating method was applied for foaming polystyrene (PS) using supercritical CO₂ (Sc-CO₂) as physical blowing agent. Then, changes of cell structure and impact strength in microcellular foamed PS materials under constrained conditions were studied. The effects of foaming processing parameters, such as foaming temperature, saturation pressure and foaming time on the cell structure and impact strength of foamed PS in the constrained conditions were studied. The results showed that the Sc-CO₂ solubility and nucleation density in the constrained conditions were not influenced compared with those under free foaming conditions. However, cells in constrained foaming process are mostly circular and independent with thick cell walls; the phenomenon of cell coalescence and collapse was effectively eliminated under constrained conditions. In addition, cell diameters in constrained foaming process decrease with increase in foaming temperature and increase with increase in the foaming time. Compared with that in free foaming conditions, the cell growth was restrained dramatically under constrained conditions which resulted in smaller cell diameter. Moreover, higher impact strength could be obtained for foamed PS as foaming time was prolonged, foaming temperature was increased or saturation pressure was enhanced.     

新型多孔聚酯纤维的制备

介绍了一种制备发泡聚酯纤维的方法,并研究了处理工艺与多孔结构的影响。通过光学显微镜结果分析及计算,研究了加压压力、加压时间、发泡温度及发泡时问等参数对纤维中气泡密度的影响。结果表明,在其他工艺条件不变的情况下,发泡聚酯纤维中气泡密度分别随着压力、加压时间、发泡温度和发泡时间的增加而增大。其中发泡时间大于10 s后,时间对气泡密度无明显影响。     

发泡工艺对超临界CO2／PP微孔发泡泡孔形态的影响

研究了超临界CO2／PP微孔发泡过程中发泡温度和饱和压力对结晶性聚合物PP泡孔形态的影响。结果表明，温度对泡孔形态影响很大，温度升高，熔体黏度和表面张力降低，泡孔变大，泡孔密度减小。与发泡温度相比，CO2饱和压力对泡孔结构的影响较小。压力太低，CO2的溶解度小，泡孔壁太厚，泡孔分布不均匀。随着压力升高，CO2的溶解度增加，熔体黏度减小，所以泡孔直径和泡孔密度都增加，泡孔壁变薄。     

Structure and Properties of Radiation Cross-Linked Polypropylene Foam

Polypropylene (PP) sheets obtained through a two-step process (masterbatch method) were crosslinked by electron beam irradiation. The crosslinked PP sheets were foamed in an oven under different processing conditions. The effects of foaming temperature and time on the mechanical properties and cell structure of PP foams were studied. With the foaming temperature increasing and foaming time lengthening, both the compression modulus and compression strength dropped. Scanning electron microscope (SEM) was employed to study the morphology and cell structure of different samples and the related morphology parameters were acquired. The results showed there was an optimum temperature and time that produced the maximum expansion ratio or the minimum foam density. As foaming temperature or time increased, the cell size increased and the cell density decreased regularly. Excessively high foaming temperature and overly long foaming time caused the coalescence and even the collapse of the cells.     

Production of microcellular foam plastics by supercritical carbon dioxide

The production of microcellular plastic was studied in the polymethyl metacrylate (PMMA)-supercritical carbon dioxide and polycarbonate (PC)-supercritical carbon dioxide systems. The test pieces of PMMA and PC were put into a saturation vessel of which temperature and pressure were kept constant. Supercritical carbon dioxide at temperature between 303K and 393K and pressure between 100 bar and 250 bar was used as a foaming agent. After saturation of carbon dioxide, the pressure was quickly released to atmospheric pressure. The samples were immediately taken out from the vessel and heated in an oil bath. The fractured part of the sample was used for microstructure analysis with SEM. The effect of the saturation temperature, pressure of sorption and the foaming time on the cell mean size and cell density of the foam was investigated by considering the solubility of carbon dioxide in PMMA and PC. The foam morphologies of the foamed plastics were affected by solubility of carbon dioxide, which was directly related to saturation temperature and pressure. The cell density increased and, consequently, the cell size decreased with the solubility of carbon dioxide. The foaming time can be used a controlling factor to obtain the desired foam structure and the volume expansion ratio.     

Effect of processing parameters on cell morphology of polycarbonate foam

Abstract

The purpose of this research is to investigate the effect of processing parameters on the cell morphology of polycarbonate (PC) foam. In this study, foamed PC was prepared using a dynamic simulation foaming set-up. The cell morphology was compared at different temperatures, pressures, gas saturation times, pressure drop rates and shear rates. The cell morphology of foamed samples was characterised using SEM. It was found that foamed samples with better morphology could be obtained by varying mechanical properties, such as pressure, pressure drop rate and gas saturation time. Optimum temperature and shear rate for microcellular foaming of PC are presented.     

Foaming behavior of microcellular foam polypropylene/modified nano calcium carbonate composites

A new process was used to prepare microcellular foams with supercritical carbon dioxide as the physical foaming agent in a batch. The foaming temperature range of the new process was about five times broader than that of the conventional one. Characterization of the cellular structure of the original polypropylene (PP) and PP/nano‐CaCO₃ (nanocomposites) foams was conducted to reveal the effects of the blend composition and processing conditions. The results show that the cellular structure of the PP foams was more sensitive to the foaming temperature and saturation pressure variations than that of the nanocomposite foams. Uniform cells of PP foams are achieved only at a temperature of 154°C. Also, the low pressure of 20 MPa led to very small cells and a low cell density. The competition between the cell growth and cell nucleation played important role in the foam density and was directly related to the foaming temperature. Decreasing the infiltration temperature depressed the initial foaming temperature, and this resulted in significantly larger cells and a lower cell density. A short foaming time led to a skin–core structure; this indicated that a decrease in the cell size was found from skin to core, but the skin–core structure gradually disappeared with increasing foaming time. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚丙烯及聚苯乙烯发泡体系熔体密度的研究

通过高压毛细管流变仪测量聚丙烯发泡体系的PVT关系,得到一定压力和温度下聚丙烯发泡体系的熔体密度,用于分析发泡体系的毛细管流变特性。与聚苯乙烯和高冲击强度聚苯乙烯发泡体系的熔体密度进行了对比,研究并分析了温度、压力、发泡剂及成核剂含量对发泡体系熔体密度的影响。结果表明:发泡体系的熔体密度均随压力的增大而提高,随温度的升高而降低;在发泡气体的临界压力处,发泡体系的熔体密度产生突变;高压下,发泡剂与成核剂含量对熔体密度的影响很小。