乳清酸的2.5次微分示波极谱法测定

拟定了乳清酸的2.5次微分示波极谱测定新方法.结果表明在0.8 mol/L HCl介质中,乳清酸产生一灵敏的极谱还原波,峰电位Ep =-0.77 V(vs.SCE);其2.5次微分极谱峰峰电流ep″与乳清酸浓度在4.0×10-8～4.0×10-5 mol/L范围内呈良好线性关系(r=0.999 6,n=9),检测限为1.0×10-8 mol/L;13次平行测量4.0×10-7 mol/L乳清酸的峰电流,所得RSD为1.8%.该方法可直接用于测定牛奶中乳清酸的含量.     

Synthesis and properties of poly(amic acid)s and polyimides based on 2,2′,6,6′‐biphenyltetracarboxylic dianhydride

Poly(amic acid)s (PAAs) having the high solution stability and transmittance at 365 nm for photosensitive polyimides have been developed. PAAs with a twisted conformation in the main chains were prepared from 2,2′,6,6′‐biphenyltetracarboxylic dianhydride (2,2′,6,6′‐BPDA) and aromatic diamines. Imidization of PAAs was achieved by chemical treatment using trifluoroacetic anhydride. Among them, the PAA derived from 2,2′,6,6′‐BPDA and 4,4′‐(1,3‐phenylenedioxy)dianiline was converted to the polyimide by thermal treatment. The heating at 300 °C under nitrogen did not complete thermal imidization of PAAs having glass‐transition temperatures (T_g)s higher than 300 °C to the corresponding PIs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6385–6393, 2006     

Glycopolymeric inhibitors of β‐glucuronidase. III. Configurational effects of hydroxy groups in pendant glyco‐units in polymers upon inhibition of β‐glucuronidase

Two kinds of new glycopolymers, (P(VB‐1‐GlcaH‐co‐AAm), 9 ) and (P(VB‐1‐Glco‐co‐AAm), 10 ), were synthesized through the radical copolymerization of styrene derivatives bearing pendant D ‐glucaric and D ‐gluconic moieties, N‐(p‐vinylbenzyl)‐1‐D ‐glucaramide (VB‐1‐GlcaH, 7 ), and N‐(p‐vinylbenzyl)‐D ‐gluconamide (VB‐1‐Glco, 8 ), with acrylamide (AAm). Glycopolymer 9 bearing the pendant glucaric moiety at the first position inhibited the hydrolysis of a model compound for xenobiotics‐β‐glucuronide conjugates, p‐nitrophenyl β‐D ‐glucuronide, uncompetitively, in contrast to the competitive inhibition in the presence of the corresponding isomeric glycopolymer bearing the pendant D ‐glucaric unit at the sixth position (P(VB‐6‐GlcaH‐co‐AAm), 3 ) reported in our previous article. On the other hand, another copolymer 10 bearing the gluconic moiety was found not to inhibit the hydrolysis as well as the corresponding copolymer bearing pendant gulonic unit (P(VB‐6‐Glco‐co‐AAm), 4 ). These results indicate that the hydrolysis is influenced not only by existence of pendant carboxyl units but also by the direction on the linkage of the glyco‐units to the polymer frame. Therefore the configurational position of hydroxy groups in pendant glyco‐units in macromolecular inhibitors may be essential for the interaction with β‐glucuronidase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4895–4903, 2006     

Chiral soluble polymers and microspheres for enantioselective crystallization

A series of chiral polymers based on poly(N‐acryl) amino acids was synthesized using a convergent synthetic approach. These chiral polymers have been used as chiral additives to induce enantioselective crystallization of racemic or conglomerate amino acids in solutions. These polymeric additives showed strong capabilities to enhance highly enantioselective resolution during the crystallization of amino acids. In addition, these polymers caused unusual modifications of amino acid crystal morphologies. Furthermore, spherical microparticles of those same chiral polymers were also shown active in similar chiral discriminations during amino acid crystallizations occurring on microparticle surfaces. Our study demonstrates the high potential of chiral polymers and microparticles to resolve amino acids throughout crystallization processes. High enantiomeric excesses in one targeted enantiomer of amino acids can also be maximized via time‐dependent kinetic control of crystallizations. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3009–3017, 2006     

Reinforcement effect of MAA on nano‐CaCo3‐filled EPDM vulcanizates and possible mechanism

Methacrylic acid (MAA) was used as in situ surface modifier to improve the interface interaction between nano‐CaCO₃ particle and ethylene–propylene–diene monomer (EPDM) matrix, and hence the mechanical properties of nano‐CaCO₃‐filled EPDM vulcanizates. The results showed that the incorporation of MAA improved the filler–matrix interaction, which was proved by Fourier transformation infrared spectrometer (FTIR), Kraus equation, crosslink density determination, and scanning electron microscope (SEM). The formation of carboxylate and the participation of MAA in the crosslinking of EPDM indicated the strong filler–matrix interaction from the aspect of chemical reaction. The results of Kraus equation showed that the presence of MAA enhanced the reinforcement extent of nano‐CaCO₃ on EPDM vulcanizates. Crosslink density determination proved the formation of the ionic crosslinks in EPDM vulcanizates with the existence of MAA. The filler particles on tensile fracture were embedded in the matrix and could not be observed obviously, indicating that a strong interfacial interaction between the filler and the matrix had been achieved with the incorporation of MAA. Meanwhile, the presence of MAA remarkably increased the modulus and tensile strength of the vulcanizates, without negative effect on the high elongation at break. Furthermore, the ionic bond was thought to be formed only on filler surface because of the absolute deficiency of MAA, which resulted in the possible structure where filler particles were considered as crosslink points. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1226–1236, 2006     

北方铜业冶炼厂硫酸系统风机单机运行实践

详细介绍了S1200-16型鼓风机在北方铜业冶炼厂的使用情况，以及S1200-16型鼓风机的结构、技术参数，提出了为确保风机的正常运行所采取的处理措施。     

Moisture sorption, transport, and hydrolytic degradation in polylactide

Management of moisture penetration and hydrolytic degradation of polylactide (PLA) is extremely important during the manufacturing, shipping, storage, and end-use of PLA products. Moisture transport, crystallization, and degradation, in PLA have been measured through a variety of experimental techniques including size-exclusion chromatography, differential scanning calorimetry, and X-ray diffraction. Quartz crystal microbalance and dynamic vapor sorption experiments have also been used to measure moisture sorption isotherms in PLA films with varying crystallinity. A surprising result is that, within the accuracy of the experiments, crystalline and amorphous PLA films exhibit identical sorption isotherms.