原位聚合型阻燃尼龙6纤维的制备及性能研究

利用原位聚合的方式,在己内酰胺水解聚合体系中引入三聚氰胺氰尿酸盐(MCA)阻燃剂,一次性制备出MCA/尼龙6(PA6)阻燃复合材料。利用这种复合材料进行熔融纺丝,通过扫描电镜(SEM)考察了阻燃纤维的相容性。MCA粒子在PA6基体树脂中均匀分布,没有发生团聚现象。通过测定阻燃纤维的力学性能,发现MCA加入量在7.2%和10.0%的阻燃纤维的断裂强度与断裂强力都有一定程度的降低,但断裂伸长率变大。阻燃剂含量在7.2%和10.0%的MCA/PA6阻燃纤维极限氧指数(LOI)能达到35%以上,具有较佳的阻燃性能。     

原位聚合无卤阻燃3D打印PA 6粉末的制备及表征

在己内酰胺(CPL)水解开环悬浮聚合体系中加入三聚氰胺氰尿酸(MCA)单体盐,制备了可用于3D打印的无卤阻燃聚酰胺6(FRPA 6)粉末材料,在打印机上烧结成形,研究了MCA单体盐的加入对制品力学性能及阻燃性能的影响,并对FRPA 6形貌及性能进行了表征。结果表明:在悬浮聚合体系中,MCA的自组装反应进行比较充分,生成的MCA均匀分散在FRPA 6中,达到纳米级别;随着体系中MCA含量的增加,FRPA 6的熔点、抗冲击强度、拉伸强度和弯曲强度有所下降,断裂伸长率、结晶温度有所提高,当MCA质量分数为8%时,FRPA 6阻燃性能达到UL94 V-0级,拉伸强度为62.4 MPa,缺口冲击强度为7.4 k J/m~2,弯曲强度为64.7 MPa。     

芳香席夫碱基阻燃剂的制备及其在聚酰胺6中的应用

为提高聚酰胺6(PA6)用反应型阻燃剂的热稳定性，以对苯二甲醛（TPAL）、对氨基苯甲酸（PABA）、9,10-二氢-9-氧代-10-磷杂菲-10-氧化物（DOPO）与二苯基氧膦（DPO）为原料，制备芳香席夫碱基磷氮协效阻燃剂TMADOPO和TMA-DPO，对产物的结构及热稳定性进行表征。通过熔融共聚制备阻燃PA6(FRPA6s)，在TMA-DOPO中分别引入二乙基次磷酸铝（AlPi）和三聚氰胺氰尿酸盐（MCA）以协效阻燃，研究阻燃剂对PA6相对黏度、热稳定性、阻燃性能和力学性能的影响。结果表明：TMA-DOPO的热稳定性更优异。引入阻燃剂后，FRPA6s的热稳定性、相对黏度、拉伸强度均下降，阻燃性能提高。相比PA6，当TMA-DOPO与MCA（或AlPi）引入量分别为己内酰胺质量的5%、3%,TMA-DPO引入量为7%时，使FRPA6s垂直燃烧达到V-0级，极限氧指数（LOI）分别提升至30.7%、30.3%和29.7%。     

包覆型MCA/PA6复合材料的制备及其阻燃性研究

以水为反应介质、无水乙醇为溶剂,将正硅酸四乙酯(TEOS)制备成二氧化硅(SiO_2)溶胶,利用溶胶的网络结构对三聚氰胺氰尿酸盐(MCA)进行表面包覆,制备出包覆型MCA阻燃剂;通过熔融共混方式,将包覆前后MCA与聚己内酰胺(PA 6)切片混合制备成不同阻燃剂含量的阻燃PA 6复合材料;采用红外光谱仪X射线光电子能谱仪、差示扫描量热仪、热重分析仪、垂直燃烧法和极限氧指数法等研究了阻燃PA 6复合材料的结构、热性能及阻燃性能。结果表明:SiO_2溶胶成功接枝在MCA表面,且主要分子结构没有发生改变;随着阻燃剂含量的增加,PA 6复合材料的熔点均有降低,但下降幅度较小;包覆型MCA在材料燃烧过程中能够有效参与成炭,在材料表面形成致密的保护层,增强PA 6复合材料的凝聚相阻燃效果,提高其阻燃性能;随着阻燃剂含量增加,PA 6复合材料的阻燃性逐步提高,添加包覆型MCA质量分数为8%时,PA 6复合材料阻燃性可达到UL-94 V-0等级,极限氧指数为28%。     

氮–磷协效阻燃聚酰胺66制备与性能

为改善聚酰胺66(PA66)的阻燃性能,以氮系阻燃剂三聚氰胺氰尿酸盐(MCA)和磷系阻燃剂9,10–二氢–9–氧杂–10–磷酰杂菲–丁二酸(DDP)协效,将原位聚合法与共聚法结合,经熔融缩聚制备氮-磷协效阻燃PA66树脂。利用傅立叶变换红外光谱仪、差示扫描量热仪、万能材料试验机、垂直燃烧仪和极限氧指数仪等研究阻燃PA66树脂的结构与性能。结果表明:随DDP含量的增加,阻燃PA66的相对黏度、熔点、结晶度和力学性能均呈下降趋势。当MCA含量为2%,DDP含量为4%时,阻燃PA66(FRPA66–4)的熔点、结晶温度和结晶度分别降至250.78℃,203.74℃,29.21%,FRPA66–4的拉伸强度和断裂伸长率分别下降为68.8 MPa和69.5%,比PA66降低了17.01%和17.46%。但PA66的阻燃性能得到改善,FRPA66–4的垂直燃烧测试达UL94 V–0级,极限氧指数为30.6%,阻燃效果良好。     

纤维级复合阻燃PA 6的制备及其热稳定性研究

以三聚氰胺氰尿酸盐(MCA)与硫化锌(ZnS)或类石墨相氮化碳(g-C_3N_4)或9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物衍生物(ZDOPO)复配体系为阻燃剂,与聚己内酰胺(PA 6)切片共混、造粒、干燥、纺丝,制备阻燃PA 6纤维;通过常规升温热失重分析以及模拟纺丝过程恒温热失重分析,研究阻燃剂种类及含量对PA 6共混体系热稳定性的影响。结果表明:在阻燃剂总质量分数为6.0%条件下,添加MCA/ZDOPO复配体系对PA 6共混体系的热稳定性影响最小,制备的阻燃PA 6纤维具有良好的力学性能和阻燃性能;添加MCA质量分数3.0%、ZDOPO质量分数3.0%,PA 6/MCA/ZDOPO共混体系热失重5%时的热分解温度为393.8℃,热失重10%时的热分解温度为412.6℃,与纯PA 6的热学性能非常接近,制备的阻燃PA 6纤维的断裂强度为1.9 cN/dtex,断裂伸长率为75.8%,极限氧指数可达29.0%。     

尼龙6/纳米蒙脱土复合材料制备及性能研究

利用活化处理的纳米蒙脱土(OMMT),通过原位插层聚合原理,控制聚合温度、压力、时间等,在聚合管实现连续化稳定制备剥离型尼龙6(PA6)/纳米OMMT复合材料;采用熔融纺丝法制得PA6/纳米OMMT复合纤维;利用X射线衍射、透射电镜(TEM)等方法分析复合材料的结构与性能。结果表明:聚合时控制水与己内酰胺质量比为3%～5%,前聚压力不超过0.4 MPa,后聚压力小于-0.040 MPa,聚合温度240～280℃,聚合时间26～30 h,可制得相对分子质量为18 000～18 600,单体质量分数小于1.6%,含水率小于450μg/g的PA6/纳米OMMT切片;TEM分析表明,纳米OMMT在PA6基体均匀分散;复合材料的力学性能有较大幅度的提高,断裂强度达102.15 MPa,比纯PA6提高了12%;PA6/纳米OMMT复合纤维性能优异,适合轮胎骨架材料的制备要求。     

阻燃抗滴落PA6纤维的性能研究

采用聚合方法制备抗滴落PA6切片,添加阻燃剂共混纺丝得到阻燃抗滴落PA6纤维。用差示扫描量热法、X射线衍射、透射电镜、极限氧指数法等方法对所得产物的热性能、结晶结构、添加剂的分散性能、阻燃性能及力学性能等进行表征。结果表明,抗滴落剂的加入引起了PA6结晶行为的变化,由α晶型转变成α晶型与γ晶型共存;PA6的热稳定性得到了提高;添加剂在聚合物中分散较均匀,阻燃抗滴落PA6纤维的极限氧指数可达26．6%～28．6%,燃烧时产生的熔融滴落物明显减少。阻燃抗滴落PA6纤维的力学性能较PA6约降低10%。     

无机填料对PA6/MCA阻燃复合材料性能的影响

研究了不同种类的无机填料(硅灰石、碳酸钙)对尼龙6(PA6)/三聚氰胺氰尿酸盐(MCA)阻燃复合材料性能的影响。阻燃性能测试结果表明,PA6/MCA/硅灰石阻燃复合材料为UL94 V–0级,比PA6/MCA阻燃复合材料(V–2级)有显著提高;然而PA6/MCA/碳酸钙阻燃复合材料的极限氧指数却有所下降。扫描电子显微镜测试分析表明,PA6/MCA/硅灰石阻燃复合材料燃烧后的表面炭层呈连续、致密状;PA6/MCA/碳酸钙阻燃复合材料的表面炭层有很多孔洞,且孔洞直径大。傅立叶变换红外光谱测试结果表明,PA6/MCA/硅灰石阻燃复合材料的表面炭层与Si O2能很好地结合,形成致密的保护层,致使其阻燃性能显著提高。另外,力学性能测试结果表明,硅灰石能够提高PA6/MCA阻燃复合材料的拉伸强度,但降低了缺口冲击强度,而碳酸钙的加入却使得PA6/MCA阻燃复合材料的综合力学性能有所下降。     

原位聚合法制备N-P复配型阻燃PA66树脂及性能

以4-(2-(((2-羧基乙烷基)(苯基)磷酰基)氧)乙氧基)-4-氧代己酸(CPPOA)和三聚氰胺氰尿酸盐(MCA)为阻燃单元,通过原位聚合法制备了N-P复配型阻燃尼龙66(PA66)树脂。相对黏度测试表明,阻燃单元的引入会造成PA66树脂分子量下降。力学性能测试结果显示,阻燃PA66的拉伸强度、冲击强度、弯曲强度以及弯曲模量均有所下降。极限氧指数及垂直燃烧测试结果显示,阻燃PA66具有良好的阻燃性能,当CPPOA和MCA的含量均为4%时,阻燃PA66树脂的极限氧指数及阻燃等级分别达到28.7%和UL-94 V-0级。XRD测试表明,阻燃改性未改变PA66的晶型结构。DSC测试表明,阻燃改性后,尼龙树脂的熔融温度、结晶温度和结晶度均呈下降趋势。TGA结果表明,阻燃PA66的初始分解温度较纯PA66下降,但成炭率提高。     

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.     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.