氧化还原引发下的淀粉、丙烯酸反相乳液聚合

以环己烷为连续相,Span20为乳化剂,采用氧化还原引发体系,通过反相乳液聚合技术,合成淀粉、丙烯酸接枝共聚物。并用红外光谱对共聚物进行了表征。研究结果表明:采用氧化还原引发剂可使聚合反应低温快速进行,在过硫酸钾为3.1mmol/L,亚硫酸氢钠为3.1mmol/L,单体丙烯酸浓度为2.6mol/L,反应温度为30℃,反应时间为3h,乳化剂浓度为5%时,单体转化率为92.6%、淀粉接枝率为43.2%、淀粉接枝效率56.4%。     

N-苯基马来酰亚胺/苯乙烯/丙烯腈/α-甲基苯乙烯乳液共聚动力学

以十二烷基硫酸钠（SDS）为乳化剂,过硫酸钾（KPS）引发剂引发N-苯基马来酰亚胺／苯乙烯／丙烯腈／α-甲基苯乙烯（PMI／St／AN／α-MeSt）进行四元乳液共聚,考察了聚合温度,引发剂浓度,乳化剂浓度,α-MeSt浓度对聚合速率的影响。结果表明,共聚体系的表观活化能为84．14kJ／mol,聚合初始速率同引发剂浓度的0．46次方和乳化剂浓度的0．57次方成正比。乳化剂浓度8．4mmol／L,引发剂浓度1．8mmol／L,聚合温度75℃,聚合1h,85℃熟化2h是较为合理的反应条件。α-MeSt的浓度对聚合速率有很大的影响,应控制在0．35mol／L以下。     

N-苯基马来酰亚胺/苯乙烯/丙烯腈/ɑ-甲基苯乙烯乳液共聚动力学

以十二烷基硫酸钠(SDS)为乳化剂,过硫酸钾(KPS)引发剂引发N-苯基马来酰亚胺/苯乙烯/丙烯腈/ɑ-甲基苯乙烯(PMI/St/AN/-ɑMeSt)进行四元乳液共聚,考察了聚合温度,引发剂浓度,乳化剂浓度,-ɑMeSt浓度对聚合速率的影响。结果表明,共聚体系的表观活化能为84.14 kJ/mol,聚合初始速率同引发剂浓度的0.46次方和乳化剂浓度的0.57次方成正比。乳化剂浓度8.4 m mol/L,引发剂浓度1.8m mol/L,聚合温度75℃,聚合1 h,85℃熟化2 h是较为合理的反应条件。-ɑMeSt的浓度对聚合速率有很大的影响,应控制在0.35 mol/L以下。     

反相乳液聚合法合成淀粉接枝丙烯酰胺的工艺研究

研究以玉米淀粉为原料,反相乳液体系中淀粉与丙烯酰胺接枝共聚反应规律。考察引发剂浓度、乳化剂用量、丙烯酰胺单体与玉米淀粉质量比接枝共聚反应的影响。通过单因素实验,获得最佳工艺条件:引发剂浓度为6mmol/L,乳化剂用量5%,丙烯酰胺单体与玉米淀粉的质量比为1.5∶1。在此条件下,可制备得到单体转化率95.46%、接枝效率88.12%、特性粘度410 mL/g的接枝共聚物,该接枝物比相对分子质量500万的聚丙烯酰胺的絮凝性能更好,在用量为25 mg/L时,对高岭土水样的浊度去除率达到88.6%。     

紫外光引发MMA/BA/AA的三元共聚乳液的研究

采用紫外光引发体系合成了MMA/BA/AA三元共聚乳液,利用红外光谱表征了共聚物的结构。讨论了光照时间、AA含量、乳化剂配比和光引发剂等因素对乳液的影响。实验结果表明,单体转化率随光照时间延长而增加,在光引发剂浓度为3%时单体转化率最高,而后下降。当AA含量为3%且阴/非离子乳化剂配比为1∶3时乳液性能最好。     

衣康酸/苯乙烯磺酸/丙烯酸共聚物阻垢剂的合成研究

以衣康酸(IA)、苯乙烯磺酸(SSA)和丙烯酸(AA)为单体,过硫酸铵为引发剂,异丙醇为链转移剂,在水相中合成了IA/SSA/AA共聚物阻垢剂.通过正交试验确立了最佳合成工艺条件:单体质量比m(IA):m(SSA):m(AA)=2:1:4,引发剂与总单体的质量比为4.5%,链转移剂与总单体质量比为9.5%,在95℃下反应2 h.当IA/SSA/AA共聚物的极限黏数为5.5～6.0 mL/g,实验水中Ca2 的质量浓度为1.6g/L,阻垢剂投加质量浓度为10 mg/L时,共聚物阻CaCO3垢的阻垢率高达91.9%,特别适用于高矿化度的工业循环冷却水和油田回注水.     

DL/AM/AMPS共聚物的合成

用引发聚合方法合成了DL/AM/AMPS三元共聚物.研究结果表明,在单体总浓度为20%～30%,引发剂浓度0.1%,pH值为中性时,在0～8℃反应6h可以得到转化率为95%,特性粘数为22～28dL/g的共聚物.     

壳聚糖-甲基丙烯酰氧乙基三甲基氯化铵接枝共聚物的制备与絮凝性能研究

以壳聚糖和甲基丙烯酰氧乙基三甲基氯化铵(DMC)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,合成了壳聚糖-DMC接枝共聚物。通过正交试验考察了反应条件对接枝度的影响,得出的最佳工艺条件为:反应时间5 h、引发剂浓度16 mmol/L、壳聚糖与DMC质量比1:6、油水体积比1:1。最佳条件下平均接枝度达到110 %。将得到的壳聚糖接枝共聚物用作絮凝剂处理高岭土悬浮液,结果表明其絮凝性能优于壳聚糖和聚丙烯酰胺(PAM),且在pH值6.0、投加量为2.0 mg/L时絮凝效果最佳。     

物理变性淀粉的接枝共聚反应及其应用性能

研究了经过热处理的变性淀粉分别与醋酸乙烯酯和丙烯酸的接枝共聚反应 ,并用红外光谱验证了该反应。应用性能的实验结果表明 :变性淀粉与醋酸乙烯酯的接枝共聚反应最佳反应条件是 :单体浓度为 0 .63 mol/L ,引发剂浓度为 2 .6mmol/L,反应温度 70℃ ,淀粉浓度 70 g/L ;变性淀粉与丙烯酸接枝共聚反应的最佳反应条件是 :单体浓度 0 .42 mol/L ,引发剂浓度 3 .0 mmol/L,反应温度 70℃ ,淀粉浓度 70 g/L。将该接枝共聚物作为胶粘剂用于纸浆的粘合 ,与纯变性淀粉粘合剂比较 ,所压制纸板的性能得到较大的改善     

低分子量丙烯酰胺-丙烯酸共聚物的研制

论述了过硫酸钾 -亚硫酸氢钠氧化还原引发剂引发丙烯酰胺与丙烯酸水溶液共聚合反应工艺 ,得出了合成低分子量丙烯酰胺 -丙烯酸共聚物的最佳工艺条件为 :引发剂温度 2 5℃、丙烯酰胺浓度 3.5 mol/L、丙烯酸浓度 0 .7m ol/L、过硫酸钾浓度 0 .0 0 11m ol/L、亚硫酸氢钠浓度 0 .0 0 2 9m ol/L,溴化铜浓度 0～ 0 .0 0 0 45m ol/L。     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.