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注射速率表示塑料熔体在模腔内流动的快慢程度,对注塑试样的性能有很大影响。提出在注塑试样制备的注射阶段,熔体在模腔内应为流动状态,并应采用体积转换的方式确定模塑体积。在确定了正确的模塑体积基础上,通过控制螺杆的注射速度调整熔体的注射时间,当该注射时间达到根据标准公式计算的结果时,熔体在模腔内的注射速率则符合标准的要求。该方法的注射速率和注射压力为函数关系,注射压力在试样制备中不再是主要的影响因素,亦不能单独调整注射压力改变注塑试样的某项测试性能。该方法将注射过程与聚合物熔体的“流动”行为相关联,确保了注塑试样制备中的科学性和规范性,进而提高了重复性和再现性水平。 相似文献
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采用Moldflow软件对变模温注射成型过程进行数值模拟。利用蒸汽加热和冷却水冷却的变模温注塑工艺,研究不同蒸汽加热时间下注塑位置处压力以及制件冷凝层的变化规律,同时分析了制件表面和模具型腔表面的热响应规律。结果表明,相比于传统注射成型工艺过程,变模温注射成型通过提高注塑充填过程中模具温度,使得制件冷凝层出现在充填阶段之后;随着模具加热时间从10、15、25 s增加到40 s,注塑位置处最大注射压力从87.0608、84.6064、79.6863 MPa减小到74.4342 MPa,大大提高了熔体注塑充填过程中的充填能力;通过不同的蒸汽加热时间,制件表面和模具型腔表面可以获得不同的温度值,同时通过模拟获得了传热系数对制件表面温度的影响。 相似文献
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以高温聚酰胺10T(PA10T)为基体,制备碳纤维增强聚酰胺10T复合材料(PA10T/CF),研究复合材料注射成型的工艺参数对复合材料力学性能的影响。通过对复合材料的纤维保留长度进行分析,得到最佳平均保留长度为295μm,同时得到优化的注塑工艺参数为注塑温度330℃,注塑压力50%(注射压力最大值的50%),注射速率70%(注射速率最大值的70%),保压压力50 MPa,模具温度30℃。分析扫描电子显微镜(SEM)表征结果可知,不同纤维含量的PA10T/CF复合材料采用优化工艺参数成型时,其样品断面呈韧性断裂且CF均匀良好地分散。 相似文献
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为了提升家具设计中碳纤维复合材料的拉伸性能和弯曲性能。采用传统注塑(多浇口进胶)工艺和新型SVG(顺序阀浇口)工艺制备了碳纤维复合材料,考察了碳纤维质量分数和注塑成型工艺参数(熔体温度、模具温度、注射压力、注射速率)对碳纤维复合材料拉伸性能和弯曲性能的影响。结果表明,采用新型SVG工艺可以消除传统注塑成型工艺下的熔接痕缺陷和气穴缺陷;随着碳纤维质量从0增加至25%,不同熔体温度、模具温度、注射压力和注射速率下碳纤维复合材料的弯曲模量先增大后减小,在碳纤维质量分数为20%时取得较好综合性能;随着碳纤维质量分数的增加,熔接痕处试样和非熔接痕处试样的拉伸强度和弯曲模量都表现为先增大后减小,在碳纤维质量分数为20%时取得最大值,且在相同碳纤维质量分数下,非熔接痕处试样的拉伸强度和弯曲模量都明显大于熔接痕处试样。 相似文献
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聚保物熔体流变性能在气辅注塑工艺的影响 总被引:1,自引:0,他引:1
应用Hele-Shaw物理模型和改进的Cross流变模型及有限元算法对5种聚丙烯的气辅注塑过程进行了模拟,研究了不同聚丙烯材料在充填速度相同的条件下的压力及锁模力变化规律。结果表明,气辅注塑在气体注射后与传统注塑有较大差异,所需压力,锁模力均比传统注塑有显著降低,且聚合物的熔体流动速率减小,气体注射后产生的压力降越大,表明在生产中应尽可能选用高熔体流动速率树脂以利于气辅注塑工艺。 相似文献
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采用10 %的(质量分数,下同)NaOH碱溶液对竹纤维进行了处理,通过双螺杆挤出和注射成型制备了聚酰胺6(PA6)/竹纤维复合材料。用扫描电子显微镜﹑差示扫描量热仪、X射线衍射仪和热失重分析仪等表征了材料的形貌、结构和热性能,测试了熔体流动速率和力学性能。研究表明,碱处理可清除竹纤维中的胶质物,增大其比表面积,有利于改善PA6和竹纤维间的界面结合。PA6与竹纤维之间具有较好界面结合,相界面间无明显间隙。竹纤维使复合材料中PA6晶相的完整程度降低,使复合材料刚性增加,冲击强度、熔体流动性和热稳定性下降。在挤出和注射过程中,PA6/竹纤维复合材料较好的熔体流动性和一定的热稳定性使其具有熔体加工性能。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
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. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
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. 相似文献
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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. 相似文献
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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. 相似文献
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中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2009,37(3)
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. 相似文献
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中蓝晨光化工研究院《塑料工业》编辑部 《塑料工业》2007,35(3):1-25,67
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。 相似文献