聚甲醛生产中的挥发分脱除北大核心

根据聚甲醛的生产特点,通过研究双螺杆挤出机的脱除挥发分(简称脱挥)机理,结合聚甲醛实际生产的脱挥工艺,从螺杆组合、螺杆转速、进料量、筒体温度、螺杆长径比等方面分析了影响挤出机脱挥效率的主要因素,给出了适合聚甲醛生产的工艺参数:进料量与螺杆转速的比值维持在18~20,筒体温度为180~195℃,真空度维持在0.01 MPa以下。通过对现有挤出机脱挥系统的优化改造,使脱挥后聚甲醛中甲醛挥发量达100μg/g以下。     

聚甲醛生产中的挥发分脱除

根据聚甲醛的生产特点,通过研究双螺杆挤出机的脱除挥发分(简称脱挥)机理,结合聚甲醛实际生产的脱挥工艺,从螺杆组合、螺杆转速、进料量、筒体温度、螺杆长径比等方面分析了影响挤出机脱挥效率的主要因素,给出了适合聚甲醛生产的工艺参数:进料量与螺杆转速的比值维持在18~20,筒体温度为180~195℃,真空度维持在0.01 MPa以下。通过对现有挤出机脱挥系统的优化改造,使脱挥后聚甲醛中甲醛挥发量达100μg/g以下。     

羟基聚硅氧烷在单螺杆挤出机中的脱挥

研究了α,ω-二羟基聚二甲基硅氧烷在单螺杆挤出机中的脱挥,分析了影响脱挥效果的因素。结果表明,温度与真空度是影响脱挥效果的关键参数。温度升高,脱挥效果提高,最佳温度200～220℃;真空度升高,脱挥效果提高,但同时增加了冒料的可能性,适宜的真空度为24～28kPa。得出了实验范围内的挥发分最终质量分数与螺杆转速及进料流量的关联式。     

乙丙橡胶干法脱挥工艺技术研究

对乙丙橡胶（J～4045）胶液进行了干法后处理脱挥实验研究，探索了不同工艺条件对胶液浓度以及产品挥发分含量的影响。研究结果表明，在一定的工艺条件下，通过控制预热器的压力，可以控制胶液闪蒸浓度；通过干法后处理实验研究，确定了干法后处理最佳的工艺条件，采用干法后处理工艺，可以使样品的总挥发分小于0．5％（质量分数），满足产品指标要求；在挤出机螺杆转速为100～450r／min范围内，挤出样品的门尼粘度几乎不发生变化，挤出的样品也未发生降解，可以满足乙丙橡胶的脱挥要求。     

稀土异戊橡胶螺杆挤压脱水膨胀干燥一步法

北京化工大学和吉林石化公司研究院采用螺杆挤压脱水膨胀干燥一步法干燥稀土异戊橡胶,考察了机头温度、机筒温度、机头压力和螺杆转速对产品质量和生产能力的影响。确定了最佳工艺参数:螺杆转速为80～90r·min-1,机头温度为150℃,机筒温度为160℃,机头压力为14～16MPa。在最佳工艺条件下,装置运行和工艺参数控制平稳,干燥后稀土异戊橡胶挥发分含量小于1.0%,门尼黏度降幅小于10%,能够满足产品应用的要求。     

加工技术对聚丙烯中VOC含量的影响

研究了双螺杆挤出机中自然脱挥、真空脱挥、螺杆转速,以及加工设备种类对聚丙烯(PP)粉料中挥发性有机物(VOC)含量的影响。结果表明:PP粉料中VOC主要为烷烃、烯烃及醛酮类化合物;自然脱挥和真空脱挥均可降低PP粉料中总挥发性有机物(TVOC)的含量,但后者效果明显优于前者;控制双螺杆挤出机的螺杆转速为500 r/min,PP中TVOC含量最低;BUSS捏合机降低PP中TVOC含量的效果好于双螺杆挤出机,前者的TVOC含量仅为后者的50%左右。     

乙丙橡胶湿法脱挥工艺研究

采用乙丙橡胶(J-2070)胶液进行了凝聚、挤出脱挥的实验研究。采用改造后的喷嘴结构及合理的加料方式,有效地提高了胶液凝聚过程中的脱挥效率。采用改造后的Ⅱ型模头,进行乙丙橡胶水凝聚样品的挤出脱挥实验,实验结果表明:在挤出机模头压力3.6 MPa机头温度为154℃时,挤出样品的w(总挥发分)0.5%;在挤出机转速为50~120 r/min的范围内,挤出样品不发生降解,说明该脱挥工艺可行,满足乙丙橡胶脱挥的要求。     

螺杆转速对ABS/EVA力学性能影响

采用在材料熔融挤出共混过程中提高双螺杆挤出机螺杆转速的方法,研究了较高螺杆转速条件下双螺杆挤出机的机械剪切应力对丙烯腈-丁二烯-苯乙烯共聚物/乙烯-乙酸乙烯共聚物(ABS/EVA)共混材料力学性能的影响。结果表明,双螺杆挤出机的高剪切应力可促进EVA颗粒的分散和界面结合力的增强。在220℃的挤出温度下,当螺杆转速由120 r/min提高至1 200 r/min时,ABS/EVA共混材料的缺口冲击强度由14.3 kJ/m2提高至16.6 kJ/m2。     

单螺杆挤出机高温裂解聚乙烯制备聚乙烯蜡研究

以高密度聚乙烯(HDPE)、低密度聚乙烯(LDPE)作为裂解原料,采用单螺杆挤出机作为裂解反应器制备聚乙烯蜡(PEW)产品,研究螺杆转速和裂解温度对原料裂解所得产品性能的影响。结果表明,在挤出机裂解温度420℃、螺杆转速为10 r/min条件下,HDPE裂解所得PEW产品的性能较佳,其黏均摩尔质量为3 732 g/mol,熔点为125.5℃。此外,相同裂解工艺下,LDPE裂解所得产品较HDPE裂解所得产品的黏均摩尔质量和熔点较低,且产品的摩尔质量分布宽。     

二醋酸纤维素塑料生产中挥发分的脱除与利用

分别研究了二醋酸纤维素塑料水分、增塑剂吸收量及生产过程中螺杆转速、喂料量、螺杆组合对脱挥效率的影响。结果表明，水分作为助脱挥剂，有利于脱挥；增塑剂吸收量高，不利于脱挥；高螺杆转速、低喂料量、排气口前高屏障型螺纹元件均有利于脱挥；挥发分的有效脱除可改善产品通透度和热稳定性；挥发分中60 %以上为邻苯二甲酸二乙酯（DEP）成分；通过设计冷凝系统，实现了挥发分中增塑剂的分离，从而实现了DEP的回收利用。     

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。