超声波作用下反应体系组成对苯乙烯分散聚合反应规律的影响

研究了超声波作用下反应体系组成对苯乙烯(St)分散聚合反应规律的影响,表明超声波作用下的分散聚合反应并非一般的热引发分散聚合反应,超声波的空化作用可有效地、多途径地生成更多的自由基。掌握了聚合反应规律,可初步实现根据聚苯乙烯(PS)粒径及分布和聚合反应速率要求进行反应体系的配方设计。     

超声波引发苯乙烯分散聚合反应制备SiO2/PS复合粒子

在系统研究超声波场下辅助引发苯乙烯(St)分散聚合反应规律的基础上,利用超声波的分散、粉碎、活化、引发等多重作用,在实现纳米SiO2粒子于反应介质中均匀分散的同时,引发St单体在纳米SiO2粒子表面进行分散聚合反应,制备出二氧化硅/聚苯乙烯(SiO2/PS)复合粒子,并运用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、红外光谱(FTIR)、热重分析(TGA)、X射线衍射谱(XRD)及X射线光电子能谱(XPS)等多种测试手段对SiO2/PS复合粒子的形貌、粒径及分布、表面特性、化学组成及结构等进行了表征。     

超声波场辅助引发MMA分散聚合反应

通过试验设计,对超声波场下辅助引发甲基丙烯酸甲酯分散聚合反应的可行性进行研究,研究结果表明:利用超声波空化作用产生的热点效应,油溶性引发剂AIBN裂解生成自由基可引发甲基丙烯酸甲酯的分散聚合反应.反应体系组成对甲基丙烯酸甲酯分散的聚合反应有较大的影响,较优化的配方为:w(MMA)=15%,w(AIBN)=0.20%,w(PVP)=1.50%,VMeOH/VH2O=2.0.     

紫外光引发乳液聚合制备P(St-co-MMA)复合微球

以十二烷基硫酸钠为乳化剂,2,2-二甲氧基-2-苯基苯乙酮等为引发剂,在水中由紫外光引发苯乙烯(St)和甲基丙烯酸甲酯(MMA)进行乳液聚合,研究了引发剂种类及乳化剂用量对反应收率和微球粒径的影响,并与光引发分散聚合体系进行了比较。结果表明,乳液聚合速率大于分散聚合,由乳液聚合得到的P(St-co-MMA)微球的粒径均一,可控制在70～140 nm之间。     

表面处理方式对纳米SiO_2/PS复合粒子粒径及分布的影响

纳米SiO2粒子进行表面处理时所用表面活性剂的种类及用量直接影响二氧化硅/聚苯乙烯(SiO2/PS)复合粒子的粒径及分布。纳米SiO2粒子在超声波场作用下经十六烷基三甲基溴化胺(CTAB)处理后,可在纳米SiO2粒子表面形成单体和引发剂的富集区,在适当条件下引发以纳米SiO2粒子为核心的原位分散聚合反应。当纳米SiO2粒子对CTAB的吸附与初级粒子对聚乙烯吡咯烷酮(PVP)K-30的吸附达到动态平衡时,制备出的SiO2/PS复合粒子表面光滑,分散性好,仅有少量的游离纳米SiO2粒子存在,大部分纳米SiO2粒子被PS包裹。     

超声波场作用下苯乙烯的分散聚合反应机理研究

通过实验研究和理论分析,提出了超声波场作用下分散聚合的反应是分区域分阶段逐步进行的反应机理。在分散聚合反应过程中,成核机理为接枝共聚物聚结机理,稳定机理以接枝稳定机理为主,分散剂吸附为辅。聚合过程可分为5个阶段:自由基生成阶段、强化扩散阶段、均相溶液聚合阶段、聚结成核阶段和粒子增长阶段。     

苯乙烯分散聚合反应

苯乙烯在乙醇／水混合溶液介质中,在偶氮二异丁腈引发作用下,以聚乙烯基吡咯烷酮为稳定剂进行分散聚合反应,采用溴加成双键分析方法研究了苯乙烯分散聚合反应过程中单体转化率的变化,并讨论了引发剂浓度和反应温度对单体转化率的影响。     

低密度聚乙烯反应挤出接枝衣康酸的研究

以过氧化二异丙苯(DCP)为引发剂,在双螺杆挤出机中制备了衣康酸(IA)熔融接枝低密度聚乙烯(LDPE)。考察了引发剂用量、单体用量、螺杆转速对接枝反应的影响,并探讨了苯乙烯(St)作共聚单体对接枝反应的影响。结果表明:St共聚单体可显著提高接枝率。     

溶剂对甲基丙烯酸甲酯与苯乙烯高温聚合的影响

利用引发剂,在高温下引发甲基丙烯酸甲酯(MMA)与苯乙烯(St)聚合,研究了w(甲苯)对聚合过程及产品结构的影响。结果表明,溶剂的存在能够显著影响MMA与St的共聚合。随着w(甲苯)增加,聚合物中w(St)随之增加;w(甲苯)=5%～20%,反应转化率减小,聚合物相对分子质量增加;w(甲苯)20%,反应转化率减小趋势变慢,聚合物相对分子质量降低。     

粒子表面处理对纳米Ag/PMMA复合粒子的影响

纳米银/聚甲基丙烯酸甲酯(Ag/PMMA)复合粒子是一种新型的功能粒子,可以有效利用昂贵金属纳米粒子组元的独特性能,是高表面能金属纳米粒子稳定化的有效途径。在Ag/PMMA复合粒子的制备过程中,纳米Ag粒子表面处理时所用表面活性剂的种类及用量直接影响Ag/PMMA复合粒子的粒径及分布。纳米Ag粒子在超声波场作用下经十二烷基硫酸钠(SDS)处理后,可在纳米Ag粒子表面形成单体和引发剂的富集区,在适当条件下引发以纳米Ag粒子为核心的原位分散聚合反应。本文通过对各影响因素的研究,采用阴离子表面活性剂SDS对纳米Ag粒子进行表面处理,且用量控制在Ag粒子质量的10%～15%范围内,可实现Ag粒子的PMMA有机包覆。     

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。