Preparation and properties of composites made from rice straw and poly(vinyl chloride) (PVC)

Rice straw was employed for the preparation of lignocellulosic‐poly(vinyl chloride) (PVC) composites. The effect of pretreatment of rice straw, concentration of PVC, pressure as well as pressing temperature on the mechanical properties and water absorption was studied. Also, the effect of lignin as coupling agent on the mechanical properties and water absorption of composite was studied. Composites of rice straw comprising both PVC and a coupling agent offer superior properties compared to those made from only rice straw and PVC. The extent of improvement in the mechanical properties and dimensional stability of composites depended not only on the pretreatment of rice straw, concentration of PVC and lignin but also on pressure and pressing temperature. Copyright © 2004 John Wiley & Sons, Ltd.     

反相乳液聚合制备壳聚糖接枝共聚物及应用

以壳聚糖、丙烯酰胺、甲基丙烯酰氧乙基三甲基氯化铵为原料,硝酸铈铵为引发剂,Span-20为乳化剂,通过反相乳液聚合技术,合成壳聚糖阳离子接枝共聚物。分析讨论了乳化剂用量、引发剂浓度、油水体积比、单体配比、反应时间、反应温度对共聚物接枝率的影响,并采用正交试验方法对合成条件进行了优化。研究了其对重金属离子Cu2 、Cd2 、Zn2 的吸附性能。结果表明,在Cu2 、Cd2 、Zn2 的混合离子体系中,该共聚物对Cu2 、Zn2 有选择性吸附。     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

甲酰胺与肌醇在氯化钠水溶液中的焓相互作用

应用等温流动微量热法测定298.15 K时甲酰胺与肌醇分子在不同浓度氯化钠水溶液中的混合过程焓变及其稀释焓, 根据McMillan-Mayer理论关联得到各级异系焓相互作用系数(h_xy, h_xxy及h_xyy). 结果表明, 甲酰胺与肌醇分子在氯化钠水溶液中的异系焓对相互作用系数h_xy均为负值, 并且随着氯化钠浓度的增加, h_xy的绝对值逐渐减小.     

Nitroxide mediated living radical polymerization of styrene onto poly (vinyl chloride)

Nitroxide‐mediated ‘living’ free radical polymerisation (LREP) was employed for the first time to prepare graft copolymer by having arylated poly (vinyl chloride) (PVC‐Ph) as a backbone and polystyrene (PS) as branches. The graft copolymerization of styrene was initiated by arylated PVC carrying 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) groups as a macroinitiator. Thus, the arylated PVC was prepared in the mild conditions and these reaction conditions could overcome the problem of gelation and crosslinking in polymers. Then, 1‐hydroxy TEMPO was synthesized by the reduction of TEMPO with sodium ascorbate. This functional nitroxyl compound was coupled with brominated arylated PVC (PVC‐Ph‐Br). The resulting macro‐initiator (PVC‐Ph‐TEMPO) for ‘living’ free radical polymerization was then heated in the presence of styrene to form graft copolymer. DSC, GPC, ¹HNMR, and FT‐IR spectroscopy were employed to investigate the structure of the polymers. Copyright © 2007 John Wiley & Sons, Ltd.     

基于双氨基三唑硫醚为中性载体的汞离子选择性电极的研究

研制了基于双氨基三唑硫醚为中性载体的阳离子选择性电极。实验表明,该电极对Hg2 具有良好的电位响应特性,在pH 2.0硝酸盐缓冲液中,电极电位呈近能斯特响应,线性响应范围为4.0 mg/L~20 g/L,斜率为33.4 mV/dec.(25℃),检出限为1.7 mg/L。该电极响应时间短(<10 s),pH范围较宽(1.3~3.3)。将该电极用于实际水样和二元混合溶液中Hg2 的检测,其结果令人满意。     

INTROMISSION OF WATER-REPELLENT AND HYDROSCOPIC PROPERTIES SIMULTANEOUSLY TO PP BY PLASMA DISCHARGE METHOD

Plasma-induced surface graft copolymerization of acrylic acid on polypropylene non-woven fabric (PP-g-AA) and polypropylene membrane were reported. The extents of grafting were controlled by the plasma and polymerization condition. Hexadecyltrimethyl ammonium bromide was then coupled with the carboxyl group of PP-g-AA to obtain a polyion complex (PIC). At last, CF4 plasma was used to give PICs hydrophobic property. The moisture regain and water-repellency of the processed PICs was investigated. The surfaces were characterized using ATR FT-IR and XPS. The result indicates that the products have very high ability to adsorb moisture, even better than cotton fiber. At the same time, the products show excellent hydrophobic property, which can‘t be wetted by those reagents whose surface tensions were higher than 327mN/m.     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

Molar volumes and ion pairing of lithium halides in alcohols

The concentration dependence of the apparent molar volumes of lithium halides (and electrolytes in general) in alcohols (and solvents permitting association in general) is, in the first instance, due to changes in the degree of association and to the inherent difference between the apparent molar volumes of the ions and of the ion pairs. Previous publications on the molar volumes of electrolytes in organic solvents, disregarding altogether ion pairing, appear to be incorrect. Data from the literature for lithium chloride and lithium bromide in normal primary alcohols and several branched alcohols from C₁ to C₈ and data from our laboratory for lithium halides in 1-hexanol and 2-ethyl-1-hexanol served for the determination of φ _V and φ _E . Electrical and structural contributions to the values of these functions for the ions and for the ion pairs are discussed.