树脂基复合材料拉挤成型研究进展

简要综述了用于拉挤成型的热固性和热塑性聚合物种类和成型工艺,详细论述了数值模拟在拉挤成型理论分析建模和工艺参数优化等方面的研究进展。此外,还介绍了几种新型拉挤成型技术,包括编织缠绕拉挤成型技术、弯曲拉挤成型技术等。连续纤维增强热塑性复合材料具有可再加工性、环保可回收等特点,在拉挤成型领域有着广阔的发展前景。     

快速拉挤用环氧树脂体系TTT图构建及应用

拉挤成型复合材料由于其质量轻、强度高、生产成本低等优点被广泛应用。拉挤成型用树脂基体是影响复合材料工艺和性能的关键因素，掌握其在成型固化过程中的凝胶化和玻璃化行为对工艺制定和提高复合材料性能具有重要意义。文中制备了快速拉挤成型环氧树脂基体，采用动态差示扫描量热仪(DSC)和半经验的唯象模型研究了树脂固化度和固化时间、温度之间的关系，绘制了等固化度曲线；采用恒温DSC得到了基于DiBenedetto经验方程的玻璃化转变曲线；通过测试树脂的凝胶点，研究了凝胶时间和温度的关系。综合上述工作绘制了拉挤树脂体系的TTT(Time-Temperature-Transition)图，由TTT图确定了拉挤速度及模具温度设置。依据确定的工艺参数制备了拉挤板材，经超声扫描和DSC测试，复合材料内部无空隙，玻璃化转变温度达到了树脂完全固化水平。     

复合材料自动化成型和加工工艺在航天技术中的应用（续）

4.连续拉挤成型工艺 连续成型工艺就是从原材料开始经过浸渍、模制、固化、切割等工序最后得到所要求的复合材料制品。连续成型工艺是新发展起来的一种新的工艺方法,它包括连续缠绕、连续拉挤和热塑性增强塑料挤出成型等工艺,本文着重讨论连续拉挤成型工艺。 拉挤成型方法在欧美等国已有25年以上历史,但初期制品仅限于钓鱼竿等体育用品和棒材等,工艺设备也比较简陋。连续拉挤工艺就其工艺设备的完善、产品范围的扩大、生产效率的提高等方面的发展来说还是近十年的事,但所占的比重不断增加,其主要原因是其生产效率高、易于实现机械化和自动化、产品质量稳定、操作方便、劳动条件好等优点。     

水悬浮-拉挤法制备长玻纤增强PVC复合材料的研究

本文探索了长玻璃纤维增强PVC(LGF/PVC)复合材料用水悬浮-拉挤成型工艺,针对硬质PVC难加工、易降解的特点,对多种稳定剂进行了试验,并确定选择了有机锡类稳定剂,讨论成型温度等影响成型工艺的各种因素,运用SEM、冲击强度、拉伸强度、弯曲强度等测试技术研究LGF/PVC复合材料的结构和性能。结果表明,水悬浮法制备长玻璃纤维增强PVC复合材料的拉挤成型工艺是可行的,所得的复合材料有十分优良的力学性能。     

纤维缠绕复合材料固化成型中纤维密实过程数值模拟

纤维缠绕复合材料固化成型过程中,缠绕制件的纤维密实程度及单层厚度受缠绕张力、树脂流动影响较大。基于Squeeze-sponge模型,发展了适用于纤维缠绕复合材料固化成型的树脂流动/纤维密实模型。该密实模型考虑了固化度、温度、树脂黏度、渗透率等参数随固化时间的变化特性,并引入缠绕张力、缠绕图案等缠绕特征,实现缠绕制件纤维密实过程的数值模拟。通过对比文献结果,证明了密实模型的可靠。基于密实模型,对不同缠绕张力制度下的纤维密实程度进行数值模拟,结果表明,相较于各层缠绕张力相等的缠绕制度,采用层间压力相等的缠绕制度时,树脂分布更加均匀,各层纤维体分比数值趋于一致,且适当提高远离树脂出口位置的缠绕张力可实现各层纤维体分比数值相等。     

树脂基复合材料成型工艺的发展

随着复合材料工业的迅速发展,传统的复合材料成型工艺日臻完善,新的成型方法不断涌现。本文通过梳理接触低压成型工艺、拉挤成型工艺、模压成型工艺、缠绕成型工艺、铺放成型工艺、RTM成型工艺这几种先进树脂基复合材料成型工艺的发展历程,分析发展过程中的关键技术,来研究先进复合材料成型工艺的演变,从而探讨未来树脂基复合材料成型工艺的发展方向。     

拉挤成型用聚酯树脂配方的研究

一、概述拉挤成型工艺是纤维在牵引装置的拉引下,经过胶槽,再经过具有一定温度的模具后,连续快速制成纤维增强材料的拉挤制品的成型工艺。拉挤工艺要求树脂系统内无易挥发的组份;使用期长以适应连续生产,固化时间短可提高生产效率,对金属模具无腐蚀作用等。聚酯树脂的工艺性能好,它的固化过程是通过自由基聚合进行反应。当树脂基体进入具有一定温度的模具时,过氧化物分解并导致自由基开始链式反应,数秒内即可形成     

树脂基复合材料内外协同固化工艺仿真与分析

在采用传统内固化工艺对厚壁壳体成型时,内层温度往往不足以满足其固化要求或者加热时间过长,因此通常采用多次缠绕多次固化的成型工艺,耗能高、效率低,不但大大提高了成本,也难以保证产品质量。因此本文提出了内外协同固化新工艺并介绍其原理,建立纤维树脂复合材料厚壁壳体内外协同固化过程的传热模型和固化动力学模型,通过有限元软件ANSYS和APDL语言开发内外协同固化过程数值模拟程序,实现了厚壁壳体内外协同固化过程中温度和固化度的分布及其变化规律的数值模拟研究。对新工艺的数值模拟结果表明,随着外温和预热温度的不断增大,中心节点的温度、固化度和应变波动较大;厚壁壳体内外协同固化的时间很短,是传统固化时间的1/3。     

热塑性树脂基复合材料拉挤成型研究及应用进展

拉挤工艺是一种能够经济的连续生产复合材料的典型制造工艺,它不但具有其他成型方法的优点,且还具有其他工艺所不具备的优点,如生产效率高,重复性好,长度可任意切断,省原料、省能耗等.本文简要介绍了热塑性树脂基复合材料拉挤成型工艺的研究,以及国内外拉挤成型设备的发展概况.     

复合材料拉挤成型过程中温度和固化度的数值模拟研究

本文对拉挤成型过程中热传导方程和固化度动力学方程进行了数值分析，确定了拉挤模具内温度和固化度属于强耦合关系。使用有限元软件IFEPG和FORTRAN语言为平台开发出一计算机程序，并使用该程序模拟出在一定工艺参数下拉挤模具内温度和固化度的分布，着重探讨了拉挤速度对模具内温度和固化度分布的影响。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。