Atom transfer radical polymerization (ATRP): A versatile and forceful tool for functional membranes

The progress in atom transfer radical polymerization (ATRP) provides an effective means for the design and preparation of functional membranes. Polymeric membranes with different macromolecular architectures applied in fuel cells, including block and graft copolymers are conveniently prepared via ATRP. Moreover, ATRP has also been widely used to introduce functionality onto the membrane surface to enhance its use in specific applications, such as antifouling, stimuli-responsive, adsorption function and pervaporation. In this review, the recent design and synthesis of advanced functional membranes via the ATRP technique are discussed in detail and their especial advantages are highlighted by selected examples extract the principles for preparation or modification of membranes using the ATRP methodology.     

Electroactive phases of poly(vinylidene fluoride): Determination,processing and applications

Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.     

含氟无皂乳液P(CTFE-IBVE-SUA)的合成及性能研究

通过无皂乳液聚合法制备得到聚(三氟氯乙烯-乙烯基异丁基醚-十一烯酸钠)[P(CTFE-IBVE-SUA)]含氟乳液。考察了单体配比对聚合反应的影响,研究了SUA用量对乳液及聚合物性能的影响,并对聚合物的结构及乳胶粒的形貌进行了测定。结果表明:含氟无皂乳液P(CTFE-IBVE-SUA)的稳定性好、粒径分布均匀;改变单体配比中IBVE和CTFE的比例可以得到不同结构的含氟聚合物乳液;SUA用量对乳液的稳定性、乳胶粒的粒径大小及粒径分布、聚合物膜与水的接触角都有很大的影响;制得的乳液具有明显的核壳结构。     

水性氟(碳)树脂的制备及应用研究

介绍水性氟(碳)树脂的制备方法和基本性能,讨论乳化剂、反应温度、搅拌速度对聚合过程和产品性能的影响。检测结果表明,用水性氟(碳)树脂制备的水性氟(碳)涂料具有超耐候性、耐沾污性等优异性能。     

助剂对Pd/AC催化剂催化三氟氯乙烯加氢脱氯的影响

采用等体积浸渍法制备了Cu-Pd/AC和K-Pd/AC催化剂,分别考察了Cu和K助剂添加量对三氟氯乙烯加氢脱氯生成三氟乙烯的反应性能的影响,并采用N_2-物理吸附、X射线粉末衍射(XRD)测试、透射电镜(TEM)和H_2-程序升温还原(TPR)等对催化剂进行表征。结果表明:加入助剂Cu,其与Pd形成Pd-Cu合金,抑制催化剂的加氢性能,从而降低催化剂反应活性;加入助剂K,其改变了Pd的电子结构,增强了Pd的电子云密度,使Pd活化H的能力增强,从而提高催化剂的活性。助剂K质量分数为3%的催化剂,在250℃下,具有较好的催化活性,三氟氯乙烯的转化率可达90%左右,三氟乙烯的选择性可达85%左右。     

Heat Capacity and Thermodynamic Properties of Poly(chlorotrifluoroethylene) from 2.5 to 620 K

Heat capacities and thermodynamic properties of a number of poly(chlorotrifluoToethylene) samples subjected to various thermal treatments, to achieve crystallinities ranging from approximately 10 to 90%, have been studied from 2.5 to 370 K by automated adiabatic calorimetiy and from 250 to 620 K by differential scanning calorimetry. Small heat capacity discontinuities in the temperature range from 320 to 350 K were observed in all samples with crystallinities greater than 40%. Spontaneous adiabatic temperature drifts associated with these anomalies were prasitive (exothermic) for quenched samples and negative (endothermic) for annealed samples. Therefore these anomalies were believed to be associated with a relaxation phenomenon similar to that of a glass transition. For highly quenched low crystallinity films, a much larger heat capacity discontinuity of greater than 15% was observed, amidst a crystallization exotherm. In addition to the above phenomena, annealing of the sample at any temperature between 240 to 400 K would produce a shift in the population distribution of crystallites from reorganization or melting and recrystallization. As a result, the apparent heat capacity became somewhat lowered at the annealing temperature and somewhat raised at about 20 K above the annealing temperature.     

Influence of strain on the thermal behaviour of poly(chlorotrifluoroethylene)

The effects of uniaxial drawing on the free volume of poly(chlorotrifluoroethylene) have been investigated using the positron annihilation lifetime technique. Annealing measurements were made both in unstrained and maximum strained conditions of the polymer to understand the influence of residual stress on the thermal behaviour. The results indicate uncoiling of the molecular chains upon stretching accompanied by orientation of the polymeric chains. The results further indicate an increase of the glass transition temperature of the drawn film and a negative thermal expansion beyond the glass transition temperature, supported by an increase in activation energy for the strained polymer. © 1999 Society of Chemical Industry     

Chlorotrifluoroethylene oligomer based nonflammable hydraulic fluid. 1 Fluid,additive, and elastomer development

A chlorotrifluoroethylene (CTFE) based nonflammable hydraulic fluid for use in the −54 °C to 175 °C temperature range has been developed for use in future aircraft and armoured land vehicles to reduce fire losses and improve survivability. The desired flammability, chemical, and physical properties of a non- flammable hydraulic fluid were defined in the 1970s and extensive screening tests were performed to determine the best candidate nonflammable hydraulic fluid basestock. CTFE was selected because it had the best overall properties of all the candidates investigated. Structurelproperty correlation studies were conducted better to understand the behaviour capabilities and limitations of the CTFE basestock. Extensive research and development have been per- formed to develop soluble, effective antiwear and antirust additives to improve some of the critical properties of CTFE. A successful formulation utilising a stabilised zinc, containing corrosion inhibitor and a sulphonamide antiwear additive, has been developed which meets all temperature, lubricity, compatibility, and thermal stability requirements. Research was concurrently conducted to develop elastomers and seals compatible with the CTFE fluid. Several materials have been developed which are usable in somewhat limited applications and Viton GLT has been found to be successful for wide temperature range applications. This paper also discusses toxicity studies and results, environmental effects, future plans and applications, and the current military specification, MIL-H-53119.     

P(CTFE-VAc-MAH)的合成

以超临界CO2为反应介质,制备了三氟氯乙烯(CTFE)-乙酸乙烯酯(VAc)-马来酸酐(MAH)共聚物[P(CTFE-VAc-MAH)]。考察了单体配比对聚合反应及聚合物结构、性能的影响,研究了聚合物的自乳化性能及交联反应。结果表明:在m(VAc)/m(CTFE)为6∶14的聚合体系中,增加MAH单体的比例,聚合物颗粒逐渐减小,产物中的氟含量逐渐降低;通过溶液法可使P(CTFE-VAc-MAH)共聚物形成自乳化乳液,乳胶粒的粒径随着聚合物中MAH比例的增大而变小;此共聚物在一定条件下可与多元醇或多元胺类发生交联反应。     

非分散红外测油法中S-316和CCl4两种萃取剂的应用研究

就 S- 316 (氯化三氟乙烯 )和 CCl4(四氯化碳 )两种萃取剂在非分散红外测油法中的应用进行探讨、分析。通过对使用两种萃取剂 (S- 316和 CCl4)方法的线性、精密度、检出限及回收率的比较 ,结果表明 ,在测油仪标定满刻度 2～ 2 0 0 m g/L 范围内成线性 ,测量精度 1%左右 ,检出限为 0 .1m g/L,加标回收率达到 85 %以上。在严格控制萃取剂纯度和分析操作的条件下 ,使用两种萃取剂所得结果一致 ,完全满足现场测油的精度。但使用 CCl4的成本远低于 S- 316 ,在用非分散红外法测水中含油量中有很高的实用价值 ,在环境监测中有着广阔的应用前景