克氏螯虾制备甲壳素及壳聚糠的研究

以克氏螯虾(Procambarus clarkii)壳为原料,通过脱脂、脱蛋白及脱钙得到甲壳素,甲壳素继续脱乙酰基制得壳聚糖。研究了HCl质量分数、酸浸时间对甲壳素脱钙的影响及NaOH质量分数、反应时间对壳聚糖脱乙酰度和黏度的影响。得到较佳的工艺为:wHCl=5%,酸浸时间2 h;wNaOH=45%,脱乙酰反应时间4 h。制得甲壳素中灰分0.9%,壳聚糖脱乙酰度81%,黏度440 mPa.s。另外,在甲壳素制备中,通过原料粉碎、添加复合脱脂剂等工艺的改进来提高效率,降低酸、碱消耗,产品质量也得到提高。     

红螯螯虾壳制备壳聚糖的研究

以红螯螯虾壳为原料提取甲壳素,得到白色片状产品,收率为18%。甲壳素通过脱乙酰化制备壳聚糖,脱乙酰度可达83%。考察了浸酸时间、浸酸温度和NaOH浓度对产品质量的影响。结果表明,采用红螯螯虾壳制备壳聚糖是可行的。     

高脱乙酰度壳聚糖的制备

以甲壳素为原料,以异丁醇为溶剂,氢氧化钠为亲核试剂,探讨了一种制备高脱乙酰度壳聚糖的新方法.研究了投料比、反应温度、反应时间、反应方法等对脱乙酰度的影响.结果表明,在反应温度为110℃,反应时间2.5h,壳聚糖∶NaOH∶醇=1∶5∶12(质量比)条件下制得脱乙酰度为93.2%的壳聚糖,而传统水溶剂脱乙酰度小于50%.另外间歇法处理样品可以在较短的时间里制备出脱乙酰度较高的壳聚糖,并用红外谱图对壳聚糖进行了表征.     

蜚蠊壳聚糖的制备研究

以蜚蠊壳为原料用微波法制备甲壳素和壳聚糖 ,用过氧化氢于适当条件下脱色 ,所得甲壳素为白色片状 ,脱乙酰度大于 75 % ,收率 14 .7% ;继而用微波加热法制备壳聚糖 ,产物粘均分子量约 65 2 0 0 0 ,收率 79%。     

从营口对虾虾壳制备壳聚糖的研究

以营口本地对虾虾壳为原料，用稀HCI和NaOH溶液分别脱去钙和蛋白质及脂肪得到甲壳素样品，使用浓碱加热处理得到壳聚糖。通正交试验设计计优化了壳聚糖的制备过程。结果表明壳聚糖制备的最佳条件是先用稀酸脱盐，再用稀碱脱蛋白得到甲壳素，随后用45%NaOH溶液，在95℃、反应时间6 h下得到壳聚糖。自制壳聚糖与市售壳聚糖的红外光谱图一致。用酸碱滴定法和红外光谱法分别测定了样品的脱乙酰度。重量法测定壳聚糖的水分。乌氏粘度计测定壳聚糖大的平均相对分子质量。所得壳聚糖的水分含量为14%,脱乙酰度为74%,平均相对分子质量为4.30×10⁴。     

壳聚糖碱液法制作工艺的优化试验

以天然虾壳为原料,对碱液法制备甲壳素、壳聚糖的工艺进行了优化试验.结果表明,二次酸碱法反应制备甲壳素的常规工艺中盐酸的使用浓度为3%～8%,在此范围盐酸使用浓度愈高甲壳素的品质越好;在壳聚糖的制作过程中,当反应温度为100 ℃,反应时间为8 h,氢氧化钠溶液浓度为60%时,得出的壳聚糖产品脱乙酰度高.     

不同虾壳部位中的甲壳素和壳聚糖

用EDTA的方法分别从虾壳的不同部位:虾头、虾身、虾足和虾头内容物三部分制备甲壳素和壳聚糖,对三组试样的性能参数如脱乙酰度和相对分子量等进行分析研究。得出结论:由虾壳不同部位所制得的甲壳素和壳聚糖结构基本一致,但其脱乙酰度和相对分子量有较大差别,其物化性质也有所不同。在三组试样中,以从虾头壳制备的甲壳素和壳聚糖的相对分子质量为最大;而脱乙酰度则以从虾足和虾头内容物中制得试样较高。     

虾壳制备甲壳素和壳聚糖的研究

用EDTA的方法分别从虾壳的不同部位:虾头、虾身、虾足和虾头内容物三部分制备甲壳素和壳聚糖,对三组试样的性能参数如脱乙酰度和相对分子量等进行分析研究。得出结论:由虾壳不同部位所制得的甲壳素和壳聚糖结构基本一致,但其脱乙酰度和相对分子量有较大差别,所以其物化性质也有所不同。特别值得一提的是,在三组试样中,以从虾头壳制备的甲壳素和壳聚糖的相对分子质量为最大;而脱乙酰度则以从虾足和虾头内容物中制得试样较高。     

微波条件下甲壳素脱乙酰反应的条件研究

研究了微波处理条件下,甲壳素脱乙酰反应条件对壳聚糖脱乙酰度的影响。结果表明:微波甲壳素颗粒大小选择为0.18～0.3mm(过60～80目筛)较利于反应。在料液比小于1∶12(质量∶体积)时,壳聚糖脱乙酰度几乎不变,粘度逐渐增大,之后脱乙酰度随料液比的增大而下降。脱乙酰度随碱液浓度的增大而增大。随微波处理时间的延长,脱乙酰度上升、特性粘度下降。微波功率越高,相同时间下,产品的脱乙酰度越高。经正交试验得出:粒度为0.18～0.3mm的甲壳素原料,按料液比1∶12(质量∶体积)加入浓度为50%(质量分数)的NaOH溶液,在微波功率320W下处理21min,所得产品的脱乙酰度可达85.65%,特性粘度为394.07mL/g,灰分为0.05%。     

制备高脱乙酰度壳聚糖反应条件的研究

以自制甲壳素为原料，通过单组分因素和正交试验结果确定制备高脱乙酰度壳聚糖的反应条件为：碱浓度40％，反应时间5h。反应温度130℃，脱乙酰度为94．4％。实验中，测脱乙酰度采用混合指示剂来代替传统的单指示剂，所得数据更加准确、可靠。     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

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.