n‐Butyl acrylate based latex interpenetrating polymer networks used as processing modifiers and impact modifiers of poly(vinyl chloride)

A latex interpenetrating polymer network (LIPN), consisting of poly(n‐butyl acrylate), poly(n‐butyl acrylate‐co‐ethylhexyl acrylate), and poly(methyl methacrylate‐co‐ethyl acrylate) and labeled PBEM, with 1,4‐butanediol diacrylate as a crosslinking agent was synthesized by three‐stage emulsion polymerization. The initial poly(n‐butyl acrylate) latex was agglomerated by a polymer latex containing an acrylic acid residue and then was encapsulated by poly(n‐butyl acrylate‐co‐ethylhexyl acrylate) and poly(methyl methacrylate‐co‐ethyl acrylate). A polyblend of poly(vinyl chloride) (PVC) and PBEM was prepared through the blending of PVC and PBEM. The morphology and properties of the polyblend were studied. The experimental results showed that the processability and impact resistance of PVC could be enhanced considerably by the blending of 6–10 phr PBEM. This three‐stage LIPN PBEM is a promising modifier for manufacturing rigid PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1168–1173, 2004     

Phase‐transfer‐agent‐aided polymerization and graft copolymerization of acrylamide

The use of phase‐transfer catalysts, with water‐insoluble initiators, for polymerization and graft copolymerization reactions was explored. The polymerization of a water‐soluble vinyl monomer, acrylamide (AAm), and the graft copolymerization of AAm onto a water‐insoluble polymer backbone, isotactic polypropylene (IPP), with a water‐insoluble initiator, benzoyl peroxide (BPO), and a phase‐transfer catalyst, tetrabutyl ammonium bromide (Bu₄N⁺Br^?), were carried out in a water/xylene binary solvent system. The conversion percentage of AAm into polyacrylamide (PAAm) and the percentage of grafting of AAm onto IPP were determined as functions of various reaction parameters, such as the BPO, AAm, and phase‐transfer‐catalyst concentrations, the amounts of water and xylene in the water/xylene mixture, the time, and the temperature. The graft copolymer, IPP‐g‐PAAm, was characterized with IR spectroscopy and thermogravimetric analysis. By a comparison of the results of the phase‐transfer‐catalyzed graft copolymerization of AAm onto IPP and the preirradiation method, it was observed that the optimum reaction conditions were milder for the phase‐transfer‐catalyst‐aided graft copolymerization. Milder reaction conditions, including the temperature, the time of reaction, and a moderate initiator (BPO), in comparison with high‐energy γ‐rays, led to better quality products, and the reaction proceeded smoothly with high productivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2364–2375, 2004     

Surface modification of single‐walled carbon nanotubes with polyethylene via in situ Ziegler–Natta polymerization

Single‐walled carbon nanotubes (SWNTs) were modified with polyethylene (PE) prepared by in situ Ziegler–Natta polymerization. Because of the catalyst pretreated on the surface of the SWNTs, the ethylene was expected to polymerize there. Scanning electron microscopy images and solubility measurements showed that the surface of the SWNTs was covered with a PE layer, and a crosslink may have formed between the SWNTs and PE. When the SWNTs covered with a PE layer were mixed with commercialized PE by melt blending, the resulting composite had better mechanical properties than the composite from the SWNTs without a PE layer. The yield strength, the tensile strength and modulus, the strain at break, and the fracture energy of the modified‐SWNT/PE composites were improved by 25, 15.2, 25.4, 21, and 38% in comparison with those of the raw‐SWNT/PE composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3697–3700, 2004     

耐溶剂复合纳滤膜的研究进展

耐溶剂纳滤是一种新型的膜分离技术,用于有机混合物的分离。商品耐溶剂纳滤膜大多是采用相转化法制备的整体皮层非对称膜,膜皮层较厚,通量较低。耐溶剂复合纳滤膜由基膜和分离层组成,具有薄皮层、高溶剂通量和高溶质截留率的优点。耐溶剂复合纳滤膜的制备与改性也因此成为近年来的研究热点。本文从界面聚合、表面涂覆、层层自组装、原位生长、有机-无机杂化和表面改性六个方面介绍耐溶剂复合纳滤膜的研究进展,最后对其发展前景进行展望。     

PET环状低聚物的表征及其开环聚合研究

以对苯二甲酸双(2-羟乙基)酯(BHET)为原料,通过悬浮法合成了聚对苯二甲酸乙二醇酯(PET)的环状低聚物(COET),对COET的结构和性能进行了表征;研究了COET的开环聚合及其在PET熔体中的开环聚合,探究了开环聚合工艺条件对其聚合产物的影响.结果表明:由核磁共振氢谱和碳谱表征悬浮法合成产物为COET,其主要以...     

Effect of crosslinked polycarboxylate superplasticizers with varied structures on cement dispersion performance

In order to investigate the effect of double bond content in the crosslinkers on the performance of superplasticizers, three different crosslinked polycarboxylate superplasticizers were synthesized herein with various respective crosslinkers. Their impacts on the fluidity, absorption, and hydration behavior of cement systems were studied. The results showed that the polymer, which was synthesized using a crosslinker with four double bonds and five/six double bonds, had higher fluidity and the highest fluidity reached up to 395 mm at W/C of 0.35. Additionally, thermogravimetric analysis and hydration heat tests showed that the crosslinked polycarboxylate superplasticizers could prolong the hydration process of cement slurries. Among these three kinds of crosslinked polycarboxylate superplasticizers, the induction period of cement slurry containing the polymer with crosslinker of four double bonds was significantly extended to facilitate the processing of the concrete. The purpose of this study is to provide strategies for studying high-performance polycarboxylate superplasticizers with novel topological structure.     

丁二烯-丙烯腈-丙烯酸丁酯三元共聚物的制备及性能

采用乳液聚合法制备了丁二烯-丙烯腈-丙烯酸丁酯三元共聚物（BNBR）,考察了引发剂、乳化剂及相对分子质量调节剂用量对乳液聚合反应速率的影响,并对BNBR的微观结构和动态力学性能进行了表征。结果表明,随着聚合温度的升高,BNBR的反应速率明显加快,反应诱导期缩短。引发剂及乳化剂用量的增加均可提高反应速率,而相对分子质量调节剂用量的变化对反应速率影响不大。BNBR共聚体系的表观反应活化能为27.97 kJ/mol,BNBR胶乳粒径分布均匀。BNBR的玻璃化转变温度低于丁腈橡胶（NBR）,二者相差约10 ℃,BNBR在低温下的动态力学性能优于NBR。     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。     

pH或/和温度双重响应嵌段接枝膜的开关特性

利用原子转移自由基聚合法(ATRP)成功地制备了聚甲基丙烯酸-嵌段-聚N-异丙基丙烯酰胺(PMN)和聚N-异丙基丙烯酰胺-嵌段-聚甲基丙烯酸(PNM)接枝开关膜。通过通量实验系统考察了两类开关膜分别或同时对pH和温度的响应性。结果表明:用ATRP法接枝嵌段共聚物开关中第一段接枝物的接枝率总是高于第二段接枝物的接枝率;该嵌段接枝开关膜对pH和温度同时响应的开关系数要大于其对单一pH或温度响应的开关系数;嵌段接枝开关中第一段接枝物对膜孔的"开"或"关"起主导作用,而第二段接枝物的影响相对较小。实验结果还表明,PMAA的pH响应开关系数比PNIPAM的温度响应开关系数显著。研究结果为设计和制备双重或多重嵌段接枝开关膜提供了有价值的参考。     

乳液聚合丁腈橡胶聚合过程的稳态模拟

运用美国Aspen Tech公司研发的Polymer Plus软件模拟乳液聚合丁腈橡胶生产中聚合部分的流程,通过对热力学参数的拟合和反应动力学参数的调整,建立了牌号为N41的丁腈橡胶聚合部分的模型。8个反应釜的模拟结果表明转化率、丙烯腈结合率和数均相对分子质量均符合乳液聚合机理的特性,与生产现场实验室分析结果能较好地吻合,相对误差在4%以内。将此热力学和动力学参数系统应用于牌号为N32的丁腈橡胶的模拟过程中,对参数的准确性进行考察,结果表明反应模型具有较好的适应性,模拟结果与实验室分析结果的相对误差在5%以内。