偏氯乙烯/丙烯腈/苯乙烯悬浮共聚合动力学

本文研究了偏氯乙烯（ＶＤＣ）／丙烯腈（ＡＮ）／苯乙烯（Ｓｔ）三元悬浮共聚合体系的聚合机理、共聚速率、非聚物组成及其特性粘度的影响因素。实验表明随着投料配比的改变,可分成四个不同聚合机理区域。Ｓｔ对ＶＤＣ／ＡＮ／Ｓｔ三元悬浮共聚有缓聚作用。ＶＤＣ三元悬浮共聚速率可用半经验模型,ｄＣ／ｄｔ＝αＣ＾β「Ⅰ」ｏ＾γｅｘｐ（－γｋｄｔ）描述,由实验得到模型参数γ值为２．２４,模型参数α、β是聚合温度与引发剂浓度的函数。ＶＤＣ－ＡＮ－Ｓｔ三元悬浮共聚物存在着较宽的ＶＤＣ组成分布,并受到单体ＡＮ水溶性的影响,经ＡＮ动态相平衡校正后,可预测ＶＤＣ三元共聚物组成。ＶＤＣ－ＡＮ－Ｓｔ共聚物的特性粘度随着转化率的升高而增大。在相同引发剂用量下,高转化率ＶＤＣ－ＡＮ－Ｓｔ共聚物特性粘度的对数与温度的倒数成线性关系。     

偏氯乙烯悬浮共聚过程中蒸汽压变化的研究

研究了ＶＤＣ／ＭＭＡ和ＶＤＣ／ＡＮ悬浮共聚过程中蒸汽压的变化。结果表明：该两个共聚体系的蒸汽压—聚合时间关系可分为三个阶段,第一阶段迅速升压,第二阶段缓慢升压,第三阶段显著降压;由于ＡＮ部分地溶于水,使ＶＤＣ／ＡＮ悬浮共聚的第二阶段压力变化很小;ＶＤＣ／ＭＭＡ悬浮共聚约在转化率为７０％时开始降压;ＶＤＣ／ＡＮ悬浮共聚约在转化率为６５％时开始降压     

无定形VDC/MMA悬浮共聚树脂的合成研究

用悬浮聚合法合成了无定形ＶＤＣ／ＭＭＡ共聚树脂,研究了单体配比、聚合温度、引发剂浓度等因素对聚合速率、树脂组成和树脂某些特性的影响。结果表明,单体中ＭＭＡ质量分数含量在２０％～４０％范围时,ＶＤＣ／ＭＭＡ悬浮共聚的速率随ＭＭＡ含量的增加而加快,并具有明显的自动加速现象,温度低于６０℃时,自动加速现象较剧烈;高转化率的树脂中ＭＭＡ单元的含量大于初始单体中ＭＭＡ的含量,其玻璃化温度与窄组成分布的ＶＤＣ／ＭＭＡ共聚树脂相近;当初始单体中ＭＭＡ质量分数大于２５％时,用本文悬浮法制得的树脂为无定形ＶＤＣ／ＭＭＡ共聚树脂     

无定形VDC／MMA县浮共聚树脂的合成研究

用悬浮聚合法合成了无定形ＶＤＣ／ＭＭＡ共聚树脂,研究了单体配比,聚合温度,、引发剂浓度等因素对聚合速率,树脂组成和树脂某些特性的影响。结果表明,单体中ＭＭＡ质量分数含量在２０％－４０％范围时,ＶＤＣ／ＭＭＡ悬浮共聚的速率随ＭＭＡ含量的增加而加快,并具有明显的自动加速现象,温度低于６０℃时,自动加速现象较剧烈;高转化率的树脂中ＭＭＡ单元的含量大于初始单体中ＭＭＡ的含量,其玻璃化温度与窄组成分布的ＶＤ     

DC/AN悬浮共聚树脂的组成及其特性研究

研究了偏氯乙烯／丙烯腈悬浮共聚树脂的组成,玻璃化曙度Ｔｇ、熔融焓△Ｈｍ、结晶度Ｘｃ和溶解度参数δｐ。结果表明：虽然ＡＮ的竞聚率较大,但ＶＤＣ／ＡＮ悬浮共聚树脂中ＡＮ含量却低于原料单体中ＡＮ的含量。、熔融     

PVF2／P（MM—St）共混体系的结晶性能和相容性的研究

用示差量热法（ＤＳＣ）、动态力学分析法（ＤＭＡ）和悬浮法测密度法研究了聚偏氟乙烯（ＰＶＦ２）／甲基丙烯酸甲酯与苯乙烯的无规共聚和［Ｐ（ＭＭＡ－Ｓｔ）］的共混体系的相容性和结晶性能。结果发现ＰＶＦ２／Ｐ（ＭＭＡ－Ｓｔ）共混体系是部分相容体系,其结晶性能随共混物中Ｐ（ＭＭＡ－Ｓｔ）的含量而变化,并就模压成型的热历史对该共混体系相容性的影响进行了讨论。     

丙烯腈/醋酸乙烯酯/甲基丙烯磺酸钠共聚体系竞聚率的研究

利用核磁共振技术测定共聚物组成,用Ｍａｙｏ－Ｌｅｗｉｓ共聚物组成方程拟合实验数据计算竞聚率。得到的丙烯腈／醋酸乙烯酯（ＡＮ／ＶＡｃ）本体共聚的竞聚率数据用于分析间歇聚合反应试验,理论计算与试验数据吻合。并研究了丙烯腈／醋酸乙烯酯／甲基丙烯磺酸钠（ＡＮ／ＶＡｃ／ＳＭＡＳ）三元水相共聚反应体系的特征,测定了该三元共聚体系表观竞聚率     

一种超强吸水树脂

华中理工大学化学系以丙烯酸（ＡＡ）、Ｎ，Ｎ－亚甲基双丙烯酸胺（ＭＢＡＭ）、过硫酸钾、甲醇、环己烷、丙烯酸及其十八酯共聚物（ＰＳＲ）为原料，在Ｎ２气流中，采用反相悬浮聚合法合成了聚（丙烯酸盐－丙烯酰胺）类超强树脂。其吸水及吸盐性能分别为：吸蒸馏水１０５０ｍｌ／ｇ，吸０．９％ＮａＣｌ溶液８６ｍＬ／ｇ，可用于婴儿尿片，医用吸水垫以及林业保墒材料。一种超强吸水树脂@吴自强     

氯乙烯／N—苯基马来酰亚胺／乙烯基单体悬浮共聚速率

根据氯乙烯（ＶＣ）／Ｎ－苯基马来酰亚胺（ＰＭＩ）／乙烯基单体悬浮共聚合工艺的特点，确定了倒加料的聚合工艺，比较了丙烯腈（ＡＮ），甲基丙烯酸甲酯（ＭＭＡ）对ＶＣ／ＰＭＩ聚合速率的影响，研究了ＡＮ的用量和聚合温度对ＶＣ／ＰＭＩ／ＡＮ三元悬浮共聚合速率的影响。     

Iniferter BDC的合成及引发St、MMA光聚合

合成Ｎ,Ｎ’－二乙基二硫代氨基甲酸苄酯（ＢＤＣ０。以ＢＤＣ作为ｉｎｉｆｅｒｔｅｒ引发Ｓｔ、ＭＭＡ光聚合,单体Ｓｔ和ＭＭＡ的转化率随光照时间的增加而增加,但没有呈现出线性关系。此外,反应环境温度高,单体转化率增加;ＰＳ和ＰＭＭＡ的粘均分子量则随光照时间的增加而呈现线性增加的关系;所得聚合物的分子量分布较宽;ｉｎｉｔｅｒｔｅｒ ＢＤＣ可以进行分子设计,合成Ｐ（Ｓｔ－ｂ－ＭＭＡ）嵌段共聚物,表现为“准活     

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.