PAN纤维共聚单体作用机理的光电离质谱研究

本工作以丙烯腈/衣康酸(IA)二元共聚原丝以及丙烯腈/IA/丙烯酸甲酯(MA)三元共聚原丝为研究对象,利用热重分析仪(TG)和热解-同步辐射真空紫外光电离质谱(Py-SVUV-PIMS)对其热稳定化过程进行研究。TG结果表明,氮气气氛下,二元共聚原丝(PAN/IA)和三元共聚原丝(PAN/IA/MA)分别呈现三阶段和两阶段的热分解过程,其中PAN/IA的第一和第二阶段均对应PAN线型分子链的断裂,但前者是由自由基环化反应放热引发的,后者则是由正常温度下的热分解所致,而单体MA的加入显著抑制了自由基环化反应,使得PAN原丝的热稳定化能够以单体IA诱导的离子型环化反应为主较平缓地进行,相应的热失重过程也由两阶段转变为了单阶段。Py-SVUV-MS的实验结果表明,两种共聚PAN原丝在程序升温过程中会生成包括含氮小分子、丙烯腈单体及低聚物、成环化合物在内的三类主要热解产物,对比各类产物的生成趋势和产量,推断单体MA通过降低PAN结构的规整度,使其无定形化,从而增加环化反应的引发点,促进PAN原丝向稳定的预氧丝转变,同时由典型热解产物——甲基丙烯腈的生成路径可知,MA本身并不参与PAN大分子的环...     

用DSC研究选择聚丙烯腈原丝的共聚单体

本文主要利用差示扫描量热分析(DSC)研究了聚丙烯腈的共聚物及其原丝的热性能，研究结果发现国产原丝具有相似的放热单峰，而日本某公司的原丝具有两个峰，分峰使聚丙烯腈原丝放热峰宽化，避免了在预氧化、碳化时放热集中产生熔化、断丝现象．聚丙烯腈原丝的纺丝、溶解、氨改性等加工过程不能明显改变其放热峰的形状，而共聚单体的种类和组成配比才是最重要的因素，通过适当的共聚单体选择、配比设计可以制得具有与日本原丝放热峰相似的聚丙烯腈聚合物或原丝。     

Network copolyesters from benzenepolycarboxylic acids and 1,6-hexanediol

Network copolyesters were prepared from trimesic (Y), pyromellitic (X) or mellitic (Y_H) acids and 1,6-hexanediol (6G). Prepolymers prepared by meltpolycondensation were cast from dimethylformamide solution and postpolymerized at 260°C for 6h to form a network. The resultant films were transparent, flexible and insoluble in any organic solvents. Degree of reaction estimated from the infrared absorbance of ester and methylene groups was almost the same for all films, 94–96%. X-ray diffraction intensity curves and densities showed that the ordering of networks was decreased by the copolymerization, which was remarkable for 6G–X/Y_H copolymer films and was consistent with the higher decreases of heat-distortion temperature for these copolymer films. The copolymerization also caused decrease of thermal stability, tensile properties and alkali resistance and increase of dye absorption.     

Enhancing water resistance of paper by graft copolymerization reaction

The chemical graft copolymerization reactions were used to enhance water resistance of paper by reaction of acrylonitrile (AN) monomer onto cellulosic paper sheet in the presence of comonomer (styrene or acrylic acid or itaconic acid) 1 : 1 molar ratio in dimethyl formamide using benzoyl peroxide as free radical initiator under nitrogen atmosphere at 70°C. The infrared spectroscopy confirms that graft copolymerization reaction occurs onto the paper samples. Water absorption test was carried out following the Normal Protocol 7/81 (water absorption by complete immersion) to evaluate the protective effect of the graft treatment onto the paper sheet. It was found that the three graft copolymerization systems reduced the water absorption of the investigated paper and the reduction of water absorption is directly proportional to the grafting %. The wettability of the grafted and ungrafted paper sheet samples were investigated using the wicking time method which exhibits the decreasing of paper sheet wettability using the AN/S comonomers in the graft copolymerization reaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Glycolytic aminolysis of poly(ethylene terephthalate) waste for recovery of value‐added comonomer at atmospheric pressure

Reaction of poly(ethylene terephthalate) waste (PETW) powder with ethylene glycol (EG) using 0.003 mol lead acetate as a catalyst was carried out in a batch reactor at 470 K under atmospheric pressure. Reactions were undertaken with various particle sizes ranging from 50 to 512.5 μm and reaction times ranging from 10 to 60 min at 10‐min intervals. A low molecular weight product of PETW was obtained using this reaction. Then hydrazine monohydrate, chlorobenzene, and cyclohexylamine (CHA) were introduced to convert the low molecular weight product of PETW into terephthalohydrazide (TPHD). To increase the PETW conversion rate, an external catalyst (lead acetate) was introduced during the reaction. The reaction product was deposited onto the surface of unreacted PETW that was removed from the surface by introducing dimethyl sulfoxide. To accelerate the reaction rate CHA was introduced during the second stage of reaction, which has industrial significance. Depolymerization of PETW was proportional to the reaction time and inversely proportional to the particle size of PETW. Analyses of value‐added products (TPHD and EG) as well as PETW were undertaken. A kinetic model was developed and experimental data were simulated consistent with the model. A thermodynamic study was undertaken because this is required during the transfer of laboratory data through the pilot plant for commercialization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3437–3444, 2003     

Synthesis of multifunctional polypropylene via solid phase cografting and its grafting mechanism

Functional monomers, maleic anhydride (MAH) and vinyl acetate (VAc), were used as comonomers in the solid‐phase grafting of polypropylene (PP). Quantitative determination of the graft level of both MAH and VAc performed by titration and FTIR methods allowed for a good appreciation of the interaction of MAH and VAc. A product with high‐graft level of both VAc and MAH was obtained when the feeding molar ratio of MAH/VAc approached 1 : 1. The melt flow rate (MFR) of the grafted PP decreased with the increase in the feeding amount of VAc. It was proposed that MAH and VAc molecules could form a kind of stable transition state during the graft polymerization and that the reactivity of both monomers were enhanced. The resulting multifunctional PP offers possibility for the development of novel PP‐based polymer blends and composites, thus extending the application field of PP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 929–935, 2002; DOI 10.1002/app.10121     

Blends of high density polyethylene and ethylene/1‐octene copolymers: Structure and properties

The morphology formation in the blends comprising a high density polyethylene (HDPE) and selected ethylene/1‐octene copolymers (EOCs) was studied with variation of blend compositions using atomic force microscopy (AFM). The binary HDPE/EOC blends studied showed well phase‐separated structures (macrophase separation) in consistence with individual melting and crystallization behavior of the blend components. For the blends comprising low 1‐octene content copolymers, the lamellar stacks of one of the phases were found to exist side by side with that of the another phase giving rise to leaflet vein‐like appearance. The formation of large HDPE lamellae particularly longer than in the pure state has been explained by considering the different melting points of the blend components. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by buckling of HDPE lamellar stack along the strain axis and subsequent microfibrils formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1887–1893, 2007     

Effect of comonomers on melt processability of polyacrylonitrile

This work is concerned with the feasibility of achieving melt‐processable polyacrylonitrile copolymer systems as precursors for the manufacture of carbon fibers. Identification of suitable comonomers and achieving the optimum content of the comonomer were some of the main objectives of this investigation. It was seen that methyl acrylate (MA) was found to be suitable for enabling the melt processing of polyacrylonitrile (PAN), in terms of melt viscosity, time stability, and char yield. Below 10 mol % of MA, the PAN copolymer exhibited no flowability, even at very low molecular weights (～ 20,000). The long‐range order inherently present in PAN is speculated to be broken down at a critical value of about 10% MA at 220°C in the PAN‐based system, enabling its melt flowability. It was also seen that the incorporation of MA was seen to improve the temperature and molecular weight window of processability of the PAN system. The molecular weight cutoff for the 90/10 mol % acrylonitrile/methyl acrylate (AN/MA) system was about 50,000 at 220°C, whereas it was increased to about 100,000 in the presence of 15 mol % MA comonomer. Feasibility studies on the use of other comonomers such as higher acrylates and acrylamides were also conducted. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 69–83, 2002     

Acrylic ampholytic ionomers

In a continuing study of the preparation of ampholytic ionomers from the polymerization of ion-pair comonomers (cationic-anionic monomer pairs) with nonionic comonomers, the preparation of such ionomers from methyl methacrylate and n-butyl acrylate is described. For both systems, ionomers of varying ion contents were obtained. In the n-butyl acrylate system, a linear relationship of T_q vs. mol % ion content was found, but this did not occur for the methyl methacrylate ionomers. The solubilities of these materials in a wide variety of solvents is discussed. It appears that for n-butyl acrylate ionomers of high ion content in aqueous solution, a new form of polymeric surfactant is obtained.     

Emulsion Copolymerization of Butyl Acrylate with Watersoluble Monomers in the Absence of Emulsifier

Abstract

Paper has connection with emulsion copolymerization of butyl acrylate with water soluble monomers in the absence of emulsifier. It was measure of kinetics of this reaction for different conditions and mechanism of this reaction is discussed.