二步法制备高强度聚甲醛纤维的工艺及性能研究

首先采用熔融纺丝工艺制备聚甲醛(POM)初生纤维,然后采用二级热箱对初生纤维进行热拉伸及热定型,制备高强度POM纤维;根据POM初生纤维的熔融结晶曲线和等温结晶性能,确定了初生纤维的热拉伸温度;研究了拉伸倍数对纤维力学性能、结晶度和取向度的影响。结果表明:POM初生纤维的热拉伸温度即第一级热箱温度为155℃,热定型温度即第二级热箱温度为120℃;POM纤维的拉伸强度和结晶度随拉伸倍数的增大先增加后降低,初生纤维经9倍拉伸时均达到最大;POM纤维取向度随拉伸倍数的增加而增加,初生纤维经9倍拉伸后趋于稳定;POM初生纤维经9倍拉伸时,所得POM纤维的拉伸强度达到最大值为1.23 GPa,断裂伸长率为21.07%。     

超拉伸UHMWPE纤维的结晶结构及其形成机理

采用冻胶纺丝-超拉伸技术纺制了超高相对分子质量聚乙烯(UHMWPE)纤维。利用小角X光散射(SAXS)、广角X射线衍射(WAXD)及拉曼光谱等测试手段,研究了拉伸过程中UHMWPE纤维的结晶结构变化。结果表明:随拉伸的进行,纤维非晶区中分子链逐渐参与了结晶,纤维SAXS强度减弱,纤维结构变得紧密规整;纤维结晶长周期及结晶度随拉伸倍数的增加而增大,并趋于平衡,拉伸30倍后,纤维结晶长周期约为50 nm,结晶度约为67.5％;纤维横向晶粒平均尺寸随拉伸倍数的增加而变小,拉伸30倍后,趋于平衡,而纤维晶粒c轴方向的轴向晶粒尺寸随拉伸倍数的增加而变大。     

I_2/KI溶液改性PVA纤维的制备及其性能研究

采用摩尔浓度比为1∶2的I2/KI溶液对聚乙烯醇(PVA)初生凝胶丝条进行超声浸泡处理,制备了改性PVA(I-PVA)纤维;探讨了I2/KI溶液浓度对纤维拉伸性能的影响,并对I-PVA纤维的结构与性能进行了研究。结果表明:I2在PVA纤维中主要以I-5的形态存在,I2的加入会阻碍PVA分子链之间的氢键形成,纤维的拉伸倍数得到提高,强度和模量也有提高;I-PVA纤维的最佳热拉伸温度为150℃,比未改性PVA纤维最佳热拉伸温度降低了50℃;PVA初生纤维在空气中拉伸3倍,采用0.1 mol/L的I2/KI溶液于40℃超声浸泡1 h后,于150℃拉伸10倍,得到的I-PVA纤维的断裂强度可达14.7 c N/dtex,比未改性PVA纤维提高9.7%,最大拉伸倍数提高到36。     

聚丙烯腈纤维热物理收缩行为的研究

利用动态力学分析、热机械分析以及X射线衍射分析等方法对聚丙烯腈(PAN)纤维在不同拉伸条件下的热物理收缩行为进行了研究。结果表明:拉伸有利于PAN纤维非晶区的取向,在热环境条件下,随着分子链运动活性的提高而生产解取向;拉伸倍数越大,PAN纤维解取向越容易发生,物理收缩量越大;沸水处理后,PAN纤维的物理收缩量随拉伸倍数的增加而减小,纤维晶态结构完善,非晶区相对含量减少。     

热水浴拉伸对聚丙烯腈初生纤维结构和性能的影响

研究了聚丙烯腈(PAN)初生纤维在热水浴拉伸过程中超分子结构和力学性能的变化。结果表明:PAN初生纤维中的内应力随拉伸温度的升高而减小,随拉伸速率和拉伸倍数的提高而增大;初生纤维在热水浴中的玻璃化转变温度约为80℃,当水浴温度低于和高于80℃时,纤维分别发生冷拉和高弹形变;PAN初生纤维的结晶度和晶区取向度随拉伸温度的升高先增大后减小,随拉伸速率和拉伸倍数的升高而增大。     

聚甲醛及其纤维的热分析研究

用Ozawa法和Mo法对聚甲醛(POM)的非等温结晶动力学进行研究。采用双螺杆纺丝机熔融纺得POM初生纤维,再用水浴拉伸方法制得POM纤维,研究拉伸倍数、水浴温度对POM纤维结晶性能的影响。结果表明:在不同的降温速率下,随着降温速率的提高,POM结晶峰峰值温度降低,半结晶时间缩短,结晶速率加快;采用Mo法研究POM的非等温结晶过程比较理想,而Ozawa法不适用;水浴拉伸有利于纤维的结晶,而随着水浴温度的提高,POM纤维的结晶度提高。     

干法纺丝低温水溶聚乙烯醇纤维的制备

以聚合度为1 700±50、不同醇解度的聚乙烯醇(PVA)为原料,按PVA-1795∶PVA-1788质量比6∶4进行共混,采用干法纺丝制备低温水溶PVA纤维,并对水溶纤维的结晶度、取向度、晶面间距、晶粒尺寸、溶断温度和溶断收缩率进行表征。结果表明:纤维的溶断温度主要取决于纤维拉伸倍数和拉伸温度,拉伸倍数越高、拉伸温度越低,溶断温度也越低;纤维的溶断收缩率不仅与取向度有关,也与晶粒尺寸有关,取向度相差不大的情况下,晶粒尺寸越大,所得纤维的溶断收缩率越高;在180℃下进行4倍拉伸时,可得到拉伸强度为5.45 cN/dtex,溶断温度为18℃,溶断收缩率为27%的低温水溶PVA纤维。     

高密度聚乙烯熔纺纤维的拉伸工艺

相对分子质量为１４万的高密度聚乙烯（ＨＤＰＥ）通过螺杆挤出机熔纺成形,然后经过高温超拉伸可制成强度为９．７ｃＮ／ｄｔｅｘ的中强聚乙烯纤维。讨论了拉伸温度、拉伸比对纤维力学性能的影响,并通过声速取向、热分析（ＤＳＣ）、广角Ｘ射线衍射（ＷＡＸＤ）和纤维力学性能的测试研究了拉伸过程中聚乙烯纤维结构与性能的变化。结果表明：拉伸温度对纤维稳定拉伸影响较大,最佳温度为１０５～１１５℃;且初生纤维的纤度越小,高倍拉伸纤维强度越大,随拉伸倍数的提高,纤维的强度和声速取向都显著提高并改善了纤维的热性能和力学性能,但断裂伸长却呈下降趋势。     

增塑剂对尼龙6性能与结晶行为的影响

研究了不同含量的苯磺酰胺增塑剂JZ-218对尼龙6力学性能、结晶行为以及热稳定性的影响.结果表明,随着增塑剂含量的增加,拉伸强度、弯曲强度与弯曲模量逐渐下降,而断裂伸长率、冲击强度与熔体质量流动速率逐渐提高.且增塑剂含量越高,改性尼龙6的熔融温度、结晶温度与玻璃化转变温度越低,但结晶度略有提高.此外,随着增塑剂含量的增...     

低温溶液缩聚PPTA共聚物的直接湿法纺丝研究

采用低温溶液缩聚法,在聚对苯二甲酰对苯二胺(PPTA)聚合体系中引入了一定量的4,4'-二氨基二苯醚(4,4'-ODA),制备出了高黏度的改性PPTA纺丝原液,并直接进行湿法纺丝;研究了使用不同黏度的纺丝原液时,拉伸倍数、凝固浴温度、凝固浴浓度等纺丝工艺条件对初生纤维力学性能的影响,确定了最佳的湿法纺丝条件;借助扫描电镜、热重分析仪、红外光谱、X射线衍射对纤维的结构和性能进行了表征。结果表明:4,4'-ODA被成功地引入到PPTA中,但改性PPTA的结晶性能和耐热性能下降;当改性PPTA纺丝原液的比浓对数黏度(ηinh)从2.12 dL/g增大至2.58 dL/g,拉伸倍数从1.25增加至2.27时,改性PPTA纤维的强度均有所增加;最佳纺丝条件为改性PPTA的ηinh2.58 dL/g,纺丝温度50℃,拉伸倍数2.27,凝固浴为N-甲基吡咯烷酮与水的体积比1∶9,凝固浴温度30℃,在此条件下可制得改性PPTA初生纤维的断裂强度为4.22 cN/dtex,断裂伸长率为24.9%,模量为105.98 cN/dtex。     

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。