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。     

模压法微孔发泡PET薄膜的性能研究

在聚对苯二甲酸乙二醇酯(PET)的玻璃化温度(Tg)和熔融温度(Tm)之间,采用模压法用AC发泡剂对PET薄膜进行微孔发泡加工,通过光学显微镜观察,微孔PET薄膜的泡孔直径小于100mm,示差扫描热分析(DSC)显示,PET结晶度和熔融温度无明显变化;拉伸力学测试表明,用模压法加工后的PET微孔薄膜材料其力学性能得到了改善。     

微孔发泡聚苯乙烯力学性能的分析与探讨

制备了发泡量相同的微发泡聚苯乙烯,采用扫描电镜(SEM)和Image-pro图像处理软件对微发泡聚苯乙烯的微孔尺寸进行了观察和统计;建立微球模型,分析了微孔尺寸大小对微发泡聚苯乙烯力学性能的影响.结果表明:细小而均匀的泡孔对微发泡聚苯乙烯力学性能的提高有较明显的促进作用,微球模型的计算结果与宏观力学性能的影响规律有很好的重现性.     

微孔发泡塑料中成核剂的研究

介绍了发泡加工过程中成核剂的引入对泡孔特性的影响。根据成核剂影响微孔发泡的原理,同时针对目前成核剂应用的研究现状进行分析对比,列举出不同类型成核剂对泡孔形态的影响,指出理想成核剂在控制泡孔异相成核过程中的作用。重点阐述了选择成核剂的标准,并指出实际过程中面临的问题,为工业生产和科学研究提供理论指导。     

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     

耗散结构理论在聚丙烯微孔发泡材料中的应用

从系统的角度出发,运用耗散结构理论,对聚丙烯微孔发泡材料中泡孔的长大规律进行分析,从而更深入地揭示了泡孔尺寸大小和泡孔分布的本质.研究结果表明:聚丙烯微孔发泡材料中泡孔的长大系统具有耗散结构特性,二次开模距离L=0.95 mm或气泡内部压力Pc达到阈值Ac时,能从原来的无序状态变为时间、空间或功能的有序状态,使体系向优化方向转变而获得均匀分布的微孔聚合物材料.     

聚合物微发泡材料制备技术理论研究进展

20世纪90年代末,超临界流体(SCF)制备聚合物微发泡材料实现了工业化,这种方法制备的微发泡材料具有非常多的优点,被誉为"21世纪的新型材料"。介绍了SCF的概念、性质以及其在相关领域的应用情况。然后对聚合物微发泡材料的理论研究进展进行了介绍,主要回顾了3个方面的研究内容,包括气体在聚合物中的溶解行为、泡孔的形成和长大机理以及聚合物/气体体系的流变行为等。这些基础性的研究工作对于深入理解聚合物微发泡材料的形成机理及后续的应用研究具有非常重要的意义。     

Improving the flame-retardant property of bottle-grade PET foam made by reactive foam extrusion

Upcycling of low intrinsic viscosity (IV) poly(ethylene terephthalate) (PET) grades, such as bottle- or recycled grades, by a reactive foam extrusion process, provides an appropriate alternative to high pricing, high IV grades commonly used for foaming applications. However, the drawback of bottle-grade PET foams is its flame retardant (FR) performance. In this study, pyromellitic dianhydride was used as a chain extender to foam bottle-grade PET. The influence of different FRs, containing halogenated (HFR) and four different phosphorous-based types, on the processability and final foam properties was investigated. HFR showed better processability to achieve proper foams with fine morphology compared to P-based FRs, where the FR content was adjusted between 2 and 5 wt%. However, HFR exhibited lower FR performance by cone calorimeter testing compared to the P-based FRs and the commercial reference foam Kerdyn. Nonetheless, all of the FRs can only improve the time to ignition of the neat PET foams while the other values depend on the specific type of FR. In addition, all FR foams have improved mechanical properties more than twice in comparison to the neat PET foam.     

Preparation and morphology characterization of microcellular styrene‐co‐acrylonitrile (SAN) foam processed in supercritical CO2

Microcellular polymeric foam structures have been generated using a pressure‐induced phase separation in concentrated mixtures of supercritical CO₂ and styrene‐co‐acrylonitrile (SAN). The process typically generates a microcellular core structure encased by a non‐porous skin. Pore growth occurs through two mechanisms: diffusion of CO₂ from polymer‐rich regions into the pores and also through CO₂ gas expansion. The effects of saturation pressure, temperature and swelling time on the cell size, cell density and bulk density of the porous materials have been studied. Higher CO₂ pressures (hence, higher fluid density) provided more CO₂ molecules for foaming, generated lower interfacial tension and viscosity in the polymer matrix, and thus produced lower cell size but higher cell densities. This trend was similar to what was observed in swelling time series. While the average cell size increased with increasing temperature, the cell density decreased. The trend of bulk density was similar to that of cell size. © 2000 Society of Chemical Industry     

PMMA/CNT微发泡密度梯度吸能材料的优化设计研究

基于聚甲基丙烯酸甲酯（PMMA）/碳纳米管（CNT）微孔发泡复合吸能材料,建立了一种等密度差密度梯度泡沫模型,通过在非线性唯象本构模型拟合得到的准静态压缩下的本构方程,计算了泡沫模型在不同载荷下的吸能效率分布特性及相应优劣势。系统研究了泡沫模型层间密度差、上下限密度差、泡沫层厚度梯度规律3种因素对梯度泡沫吸能效能的影响规律。结果表明,层间密度差为25 kg/m³与50 kg/m³的泡沫吸能效能较好;上下限密度差越小,吸能效率的峰值越高,在较低载荷的吸能效能会越差;单层密度接近于平均表观密度的泡沫层越厚,吸能效率峰值会越高。基于实验结果优化设计了一种吸能效率峰值达到0.326且吸能效能在<15 MPa载荷范围内相对于均质泡沫更有优势的梯度泡沫。这些结果对于密度梯度吸能材料的设计思路具有重要指导意义。     

Visualization of bubble dynamics in foam injection molding

This article presents a visualization study on nonisothermal bubble growth and collapse in the foam injection molding process (FIM). Observation study can give more insight to the bubble growth in foaming process, especially in the challenging injection foaming process. In this study, besides the growth of bubbles, collapse of the bubbles was also observed which could provide knowledge to the final foam morphology. Cell growth vs. time was recorded and analyzed using a software‐equipped high speed camera. To investigate the cell collapse, various holding pressure was exerted on the gas‐charged molten polymer. The amount of holding pressure had noticeable effect on the rate of bubble collapse. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microcellular Foamed Wood‐Plastic Composites by Different Processes: a Review

Wood fiber reinforced polymer composites represent a relatively small but rapidly growing material class, extensively applied in interior building applications and in the automotive industry. The polymer‐wood fiber composites utilize fibers as reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the materials cost and mechanical properties such as stiffness and strength. Wood fiber reinforced polymer composites are microcellularly processed to create a new class of materials with unique properties. Most manufacturers are evaluating new alternatives of foamed composites that are lighter and more like wood. Foamed wood composites accept screws and nails like wood, more so than their non‐foamed counterparts. They have other advantages such as better surface definition and sharper contours and corners than non‐foamed profiles, which are created by the internal pressure of foaming. This paper represents a review on microcellular wood fiber reinforced polymer composites obtained by different processes (batch, injection molding, extrusion, and compression molding process) and includes an overview of foaming agents (physical and chemical) and the foaming of wood fiber‐polymer composites (changes in phase morphology, formation of polymer‐gas solution, cell nucleation, and cell growth control).

     

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。     

微孔发泡制备聚乳酸开孔材料

微孔发泡技术避免使用有机溶剂和高温过程,在生物组织工程支架材料的制备方面具有广阔的应用前景.研究采用DOE(试验设计)方法研究发泡温度、饱和压力及发泡时间等工艺参数对开孔度及表观密度的影响程度,根据DOE试验结果确定试验空间内的最佳工艺务件,并对聚乳酸材料的开孔机理进行探讨.     

Fabrication of foamed polypropylene with excellent behaviors by adding a special foam stabilizer

Foamed polypropylene (PP) has attracted more and more attention in recent years due to its unique properties, such as heat resistance and high flexural modulus. In this work, foamed PP with excellent properties was successfully fabricated by adding a special foam stabilizer, which was prepared by a simple one-step strategy using fatty acid and amino silicone oil as reactants. The two-component stabilizer mixed uniformly with PP and reduced the surface tension during foaming. The foam stabilizer significantly reduced density and cell diameter of the foam. When the amount of foam stabilizer was 1.0 wt%, the density dropped to 0.958 g/cm³, about 2.8% lower vs foam generated without stabilizer. The tensile strength increased to 18.4 MPa from 16.1 MPa, and the elongation at break increased to 495% from 328%.     

型腔气体反压对微孔发泡泡孔结构与制品表面质量的影响

设计型腔气体反压辅助微孔发泡注塑(GCP-MIM)成型系统、模具及周边设备,利用这一套系统以聚丙烯(PP)材料为研究对象,研究GCP-MIM工艺对注塑PP试样泡孔结构与表面质量的影响.结果表明,随着气体反压持续时间的延长和气体反压压力的增加,试样泡孔尺寸变小,泡孔密度升高,其中反压持续时间从5 s延长到20 s过程中,...     

Effect of reinforcement type and length on physical properties,surface quality,and cycle time for sheet molding compound (SMC) compression molded parts

One of the fastest growing applications of sheet molding compound (SMC) compression molding is the manufacture of truck body panels. The trucking industry requires parts with high strength and stiffness, but the surface quality is also important. In this study, the effect of reinforcement type and length on physical properties, surface quality, and cycle time are evaluated. In particular, the effect of different lengths of carbon fibers and glass fibers with different sizing are studied. It was found that for the same volume percent, carbon fibers greatly improve the stiffness of the SMC at the sacrifice of strength and surface quality and also require larger fill times for the same molding force, as compared to glass fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2557–2571, 2003     

Changes in liquid hold-up in foam and size of foam by perforated plates and contribution to mechanical foam-breaking

Changes in the liquid hold-up, ?, and the diameter of d, of a foam that are induced by perforated plates (PPs) and the contribution of PPs to foam-breaking were studied. A foaming system containing a dilute detergent solution in a column with mechanical agitation fitted with a rotating-disk foam-breaker (MFRD) was used. After the foam passed through the PPs, ? and d decreased and increased, respectively. The use of PPs to achieve a maximum reduction in ? and a maximum increase in d is confirmed. It is also demonstrated that use of PPs contributes not only to improving the foam-breaking performance of the MFRD, but also to power savings.     

大型模胎用硬质聚氨酯泡沫塑料的制备研究

研究了大型模胎用硬质聚氨酯泡沫塑料的制备方法,考察了催化剂用量、匀泡剂用量、物理发泡剂用量、化学发泡剂、模具压力、后处理温度等对硬质聚氨酯泡沫塑料泡体结构和性能的影响。结果表明,可以通过控制催化剂三乙醇胺和有机锡的用量配比来调节发泡和凝胶速率,匀泡剂用量、物理发泡剂用量、化学发泡剂、模具压力、后处理温度等均能对泡体结构和性能产生影响。     

模胎用高密度酚醛泡沫塑料的制备研究

以热固性甲阶酚醛树脂为基体,正戊烷为物理发泡剂,30%硫酸和冰乙酸组成混合酸为催化剂,吐温-80和甲基硅油作为匀泡剂,玻璃微珠和聚乙二醇-400为改性剂,制备出了密度200 kg/m3以上综合性能较好的高密度酚醛泡沫。研究表明,通过调节物理发泡剂与混合酸催化剂用量可以有效控制泡沫密度以及发泡凝胶时间,添加4%聚乙二醇和8%的玻璃微珠,能够改善泡沫脆性和压缩强度,通过130℃、2.5 h的后处理可以将泡沫的质量稳定。制备出的高密度酚醛泡沫塑料在180℃高温下具有高的压缩强度,尺寸变化率在1%以内,有望作为新型模胎材料使用。