Preparation of microcellular poly(ethylene terephthalate) and its properties

Engineering plastics poly(ethylene terephthalate) (PET) is relatively difficult to process microcellularly compared to general thermal plastics because of its low melting viscosity. A new method was developed to microcellularly process PET in this study with a general hydraulic press above PET's crystallization temperature and below its melting temperature within times of a few minutes. A processing window existed in which to prepare microcellular PET under certain foaming time, pressure, temperature, and foaming reagent content scope. The effects of foaming time, temperature, pressure, and foaming reagent content on the thermal, mechanical, and dynamic mechanical thermal properties of microcellular PET foam were investigated. Differential scanning calorimetry (DSC) analysis showed that the transition temperature and crystallinity of microcellular PET had small changes with increasing foaming time. Under some processing conditions used in this study, the tensile strength and breaking extension of microcellular PET foam were both increased at the same time, indicating strengthening and toughening effects. The variation of storage modulus, loss modulus, and tan δ under dynamic mechanical thermal analysis was in accord with DSC analysis and mechanical measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1956–1962, 2003     

微孔发泡聚碳酸酯片材的制备与性能研究

在聚碳酸酯(PC)的玻璃化温度(tg)和熔融温度(tm)之间，采用模压法制备出用挤出、注射和常规发泡难以加工成型的薄型微孔发泡PC片材。模压法有制备周期短、工艺简单、操作容易、价格低廉等优点。通过热性能及力学性能测试．表明用模压法制备的微孔发泡PC片材性能优异。     

超临界CO_2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。     

轻质环氧树脂微孔发泡材料的力学及隔热性能

通过添加不同含量的化学发泡剂,制备了较小密度(0.5 g/cm~3)的环氧树脂基微孔发泡材料,研究了发泡剂含量(0.25%~2%)对环氧复合发泡材料发泡行为的影响,并讨论了材料的力学性能及隔热性能的变化规律。结果表明,随着发泡剂含量的增加,材料的表观密度不断降低,但泡孔尺寸不断增大,泡孔密度则不断降低。力学性能及隔热性能测试表明,随发泡剂含量的增加,材料的压缩屈服强度和压缩弹性模量不断降低,但是材料的隔热性能不断提高。     

Microcellular thin PET sheet foam preparation by compression molding

This study has created a new way of microcellullar processing PET thin sheet foam using a conventional hydraulic press by compression molding and by setting the temperature of press plates differently. Comparing this study with our previous work, the emphasis is on the difference of plate temperature. The nonisothermal condition is used to control the foaming agent decomposition to lead to more uniform cell size microcellular foam. A variety of cell sizes, cell densities, and relative densities are obtained as a consequence of the different foaming temperature, time, pressure, and foaming agent content via isothermal and nonisothermal conditions. The effect of isothermal and nonisothermal foaming on the cell size, cells density, and relative density has been discussed. The electrical properties of the microcellular poly(ethylene terephthalate) (PET) samples prepared in nonisothermal foaming have been investigated. The experimental results show that the microcellular PET foam has lower dielectric constant and dielectric loss and higher electric resistivity than unfoamed PET. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1698–1704, 2004     

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.     

聚碳酸酯微孔泡沫塑料力学性能的研究

采用超临界微孔发泡技术制备出一系列聚碳酸酯(PC)微孔泡沫塑料,通过扫描电镜、力学性能测试等方法研究了超临界流体温度对发泡剂(CO2)含量的影响,及发泡温度、发泡时间和超临界流体温度对PC微孔泡沫塑料力学性能的影响。结果表明:在测试范围内,随超临界CO2流体温度的升高,CO2含量降低;升高发泡温度或延长发泡时间均使PC微孔泡沫塑料的拉伸强度和冲击强度降低;随超临界CO2流体温度的升高,PC微孔泡沫塑料的拉伸强度增加,冲击强度降低。     

动态发泡工艺参数对PS微孔塑料泡孔结构的影响

以超临界CO2为发泡剂,用振动诱导发泡模拟装置研究了微孔塑料动态成型过程中气体饱和压力、压力释放速率、温度、气体饱和时间、稳态剪切速率、振动等工艺参数对聚苯乙烯（PS）微孔塑料泡孔结构的影响。研究发现,PS微孔塑料试样的泡孔结构随着气体饱和压力和压力释放速率的提高而得到改善,而温度、气体饱和时间、稳态剪切速率则存在一个最佳的操作范围,在此范围内制得的PS微孔塑料试样泡孔密度最大,泡孔尺寸最小。在稳态剪切速率一定的情况下,通过施加振动可以进一步改善泡孔结构．     

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.     

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。     

微发泡PP/竹塑复合材料发泡行为及性能研究

采用注塑成型方法,在二次开模条件下制备微发泡聚丙烯(PP)/竹粉复合材料,分析了不同含量的竹粉对微发泡PP复合材料力学性能和发泡行为的影响。结果表明:随着竹粉用量的增加,泡孔平均直径逐渐减小,泡孔密度逐渐增加。竹粉用量为30%时,泡孔直径最小,为23.4μm,泡孔密度达到10.4×106个/cm3,具有理想的发泡效果。竹粉用量在20%时,发泡材料的冲击强度和纯PP基本相同,在性能不降低情况下,节约了原材料成本。     

ABS微孔发泡材料的制备与性能研究

利用化学交联模压法制备了丙烯腈–丁二烯–苯乙烯塑料(ABS)微孔发泡材料,研究了发泡剂偶氮二甲酰胺(AC)、活化剂氧化锌(ZnO)、交联剂过氧化二异丙苯(DCP)用量对ABS微孔发泡材料力学性能和泡孔结构形态的影响。结果表明,当AC为2份、DCP为0.15份、ZnO为0.2份时,制得的ABS微孔发泡材料的泡孔密度为1.31×108cells/cm3,平均泡孔尺寸为24μm,比强度达到44.7 N/tex,综合性能最佳,可以满足微孔发泡材料的要求。     

改性剂和增塑剂对PVC微孔泡沫塑料形态影响

以超临界CO2为发泡剂,用自制的动态模拟发泡装置研究了聚氯乙烯(PVC)配方中改性剂丙烯酸酯类高分子聚合物(ACR)含量和增塑剂邻苯二甲酸二辛酯(DOP)含量对PVC微孔塑料泡孔形态的影响.结果表明,在其他工艺条件和配方相同的情况下,ACR为4份时得到的PVC微孔泡沫塑料泡孔密度最大,泡孔粒径最小,DOP为2～6份时比较适合PVC微孔发泡,并且振动力场的引入有利于得到细小均匀的微孔结构.     

CM与PVC共混发泡性能的研究

采用模压法进行发泡,研究了氯化聚乙烯(CM)与聚氯乙烯(PVC)的共混比和发泡剂用量对发泡体的泡体性能、泡孔结构的影响。结果表明,不同CM/PVC共混比的复合材料,随体系中CM的增加,发泡密度逐渐减小、泡孔体积和发泡倍率逐渐增大,当CM/PVC=50/50时,发泡材料具有较好的综合性能;改变共混体系中发泡剂AC的用量,测试泡体性能及观察泡孔结构得出,随AC发泡剂用量的增加,发泡材料的发泡密度减小,其相应的物理机械性能如拉伸强度、撕裂强度逐渐降低。     

Aramid fiber reinforced EPDM microcellular foams: Influence of the aramid fiber content on rheological behavior,mechanical properties,thermal properties,and cellular structure

In this paper, aramid fiber (AF)/ethylene-propylene-diene monomer (EPDM) microcellular foams added with different content of AF are prepared by the supercritical foaming method. The effect of the AF content on the rheological behavior, mechanical properties, thermal properties and cellular structure of the AF/EPDM microcellular foams has been systematically studied. The research illustrates that compared with pure EPDM, the AF/EPDM matrix has greater viscosity and modulus, which is conducive to reduce the cell size and increase its density. And the thermal stability of EPDM foams is improved with the addition of aramid fiber. Meanwhile, when the content of AF is added to 1 wt%, the AF/EPDM microcellular foam exhibits a relatively low thermal diffusion coefficient and apparent density with the thermal conductivity to 0.06 W/mK. When the AF is added to 5 wt%, the tensile strength of the AF/EPDM microcellular foam increases to 1.95 MPa, which is improved by 47% compared with that of the pure EPDM foam. Furthermore, when the compressive strain reaches to 50%, the compressive strength of the AF/EPDM microcellular foam is 0.48 MPa, improved by 296% compared with that of the pure EPDM foam.     

硅烷偶联剂改性云母粉在微孔发泡PP中的应用

通过硅烷偶联剂改性的云母粉,以不同含量加入聚丙烯(PP)中,制备微发泡PP/云母粉复合材料;通过相容性和分散性分析了改性与未改性云母粉微发泡PP复合材料发泡行为和力学行为的影响规律。结果表明:改性云母粉的微发泡PP复合材料泡孔直径明显减小,泡孔密度增大;抗拉强度和冲击强度都得到提高。     

Optimized Polystyrene Cell Morphology by Orthogonal Superposition of Oscillatory Shear

A novel dynamic microcellular foaming technology is presented in the form of mechanical vibration, forming an oscillatory shear orthogonal superposition upon steady shear flow. The effects of steady and oscillatory shear on polystyrene foam processing were investigated with a novel dynamic foam processing simulator. Cell morphology was analyzed by using a scanning electron microscope (SEM). The results show that the oscillatory shear has a significant influence on the cell morphology. A fine cell structure with nearly spherical cell shape is nucleated with properly arranged rotor speed and vibration parameters. At the same time, cell density increases remarkably with the introduction of vibration.     

Compressive response of PMMA microcellular foams at low and high strain rates

Microcellular foams are widely applied in various applications in both civil and military applications for barriers and energy absorption materials. Poly(methyl methacrylate) microcellular foams were fabricated via supercritical foaming method. Field emission scanning electron microscopy, differential scanning calorimetry, and mechanical test machine were used to visualize the foam structure and test the quasi‐static compression properties. Moreover, Split Hopkinson Bar (SHPB) setups were adopted to explore the dynamic compression properties. The experimental results show that the microcellular foams have homogeneous cell size distribution and exhibit superior compressive behavior at both quasi‐static and high strain rates. The mechanical properties depend on both foam density and strain rate. Strain rate effects are clearly observed. At quasi‐static strain rate and 7500 S^?1 regime, cell wall bucking and folding are the main failure mechanism. However, at high strain rate regime, softening phenomenon is observed. By roughly calculating the energy absorbed and the temperature rise, the temperature of the foams will rise up to as high as 130 °C after conducting high strain rate compression, and it is postulated that the generated heat will destroy the cell structure of the foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46044.     

Microcellular foaming of silicone rubber with supercritical carbon dioxide

In spite of great concern on the industrial application of microcellular silicone rubber foams, such as in electric and medical devices, only a few works can be found about the foaming of silicone rubber. In this study, microcellular silicone rubber foams with a cell size of 12 μm were successfully prepared with curing by heat and foaming by supercritical CO₂ as a green blowing agent. The microcellular silicone rubber foams exhibited a well-defined cell structure and a uniform cell size distribution. The crosslinking and foaming of silicone rubber was carried out separately. After foaming, the silicone rubber foam was cross-linked again to stabilize the foam structure and further improve its mechanical properties. Foaming process of cross-linked silicone rubber should be designed carefully based on the viscoelastic properties because of its elastic volume recovery in the atmosphere. The basic crosslinking condition for small cell size and high cell density was obtained after investigating the rheological behavior during crosslinking.     

氯化聚乙烯/废旧轮胎胶粉共混发泡性能研究

采用模压法进行发泡,以氯化聚乙烯（CM）为基体,研究了胶粉用量、硫化温度、硫化助剂对CM发泡体的泡体性能、泡孔结构的影响。结果表明,CM发泡体随着胶粉用量的增加,发泡密度逐渐增加,泡孔体积及发泡倍率逐渐减少。综合CM发泡体的泡体性能及泡孔结构,当胶粉用量为10份,170℃下硫化7min,使用TCHC作硫化助剂时,可得到发泡效果好,断面均匀分布,泡孔结构明显的CM发泡体。