水相沉淀法制备丙烯腈/丙烯酰胺共聚物的工艺研究

以丙烯酰胺为共聚单体,选择过硫酸铵为引发剂,采用水相沉淀法制备了丙烯腈/丙烯酰胺共聚物。研究了引发剂浓度、单体配比、聚合温度及链转移剂和终止剂的选用对共聚物转化率和分子量的影响。结果表明,反应温度宜控制在65℃,随着引发剂和共聚单体的增加,共聚物的转化率提高而分子量降低。引入链转移剂并未改变分子链结构,从热性能上看乙醇胺效果较好。而终止剂宜选用N,N-二乙基羟胺。     

水相悬浮法合成丙烯腈三元共聚物的工艺研究

以偶氮二异丁腈(AIBN)为引发剂,采用水相悬浮聚合工艺合成了高分子量的丙烯腈/丙烯酸甲酯/衣康酸(AN/MA/IA)共聚物。研究了引发剂浓度、总单体浓度、分散剂浓度、共聚单体配比、聚合温度和聚合时间对共聚反应的影响。结果表明,该聚合体系的反应速率及产率较高,且制得的AN三元共聚物具有较高的粘均分子量。     

磁场调控下制备可熔融丙烯腈-丙烯酸甲酯共聚物

外加不同强度间歇磁场(MF,0T,0.1T,0.3T,0.6T,0.9T和1.1T)的干预下,采用水相沉淀聚合法制备了一系列投料摩尔比为85/15的丙烯腈/丙烯酸甲酯共聚物(85/15AN/MA)。通过核磁共振分析仪、差示扫描量热分析仪和热台显微镜对共聚物进行了表征分析。结果表明,外加磁场对可熔融85/15AN/MA的共聚物组成、数均序列长度(NASBL)、立构规整性、热稳定性和熔融行为有较大的影响。当磁场强度为0.9T时,85/15AN/MA的共聚物组成与投料比最为接近,NASBL最短,三单元间规立构体含量最高,热稳定性高,在220℃时熔融行为更为明显,共聚物的可熔融加工性明显提高。     

丙烯腈水相沉淀聚合引发机理的研究

综述了无机引发剂引发丙烯腈水相沉淀聚合的反应机理,其特点是在主氧化剂(过硫酸盐或氯酸盐)存在的无机引发体系中,易产生离子型自由基引发丙烯腈的水相沉淀聚合反应.     

可熔融丙烯腈共聚物的组成及流变性与热性能

分别采用水相沉淀聚合法和乳液聚合法制备了丙烯腈-丙烯酸甲酯共聚物（AN/MA,投料比为85/15（物质的量比））,采用傅里叶变换红外光谱（FT-IR）、元素分析（EA）、乌氏黏度计、高级扩展流变仪（TA）、差示扫描量热仪（DSC）、热重分析仪（TG）对共聚物的组成、流变行为和热性能进行了研究。结果表明,水相沉淀聚合法和...     

聚合工艺参数对丙烯腈/丙烯酸甲酯水相沉淀共聚合反应的影响

以过硫酸铵(APS)为引发剂,采用水相沉淀聚合工艺合成了高分子量的丙烯腈/丙烯酸甲酯(AN/MA)共聚物。研究了各聚合反应因素对共聚反应的影响。结果表明:该聚合体系的反应速率及产率较高,制得的PAN共聚物具有较高的粘均分子量。     

复合引发剂在水相沉淀法制备聚丙烯腈中的应用

采用不含碱金属离子的氧化还原复合引发体系,以丙烯腈为第一单体,衣康酸为共聚单体,使用水相沉淀聚合法制备碳纤维用聚丙烯腈.研究了不同复合引发剂,单体配比,聚合反应温度和引发剂氧还比的改变对共聚反应的影响.结果表明,在不影响转化率的同时,以过硫酸按和亚硫酸按组成的复合引发体系反应温度比单引发剂至少降低了 1/3,得到的聚合...     

水相沉淀法制备丙烯腈-丙烯酰胺共聚物及其结构研究

以丙烯酰胺(AM)为共聚单体,采用水相沉淀法制备了丙烯腈/丙烯酰胺共聚物。研究了AM对聚合反应以及共聚物结构的影响。结果表明,AM竞聚率高于AN,倾向于均聚反应,会降低PAN的分子量,提高聚合反应的转化率;少量AM会略微改变分子链中的立构规整度,提高PAN的结晶度,降低晶粒尺寸。     

混合溶剂沉淀聚合工艺制备AN/AM/IA三元共聚物研究

以偶氮二异丁脒盐酸盐(V50)为引发剂,采用水/二甲基亚砜(H_2O/DMSO)混合溶剂沉淀聚合工艺合成了高分子量的丙烯腈/丙烯酰胺/衣康酸(AN/AM/IA)三元共聚物。用乌氏黏度计测出产物的平均分子量,继而分析了引发剂浓度、总单体浓度、混合溶剂配比、共聚单体配比以及反应温度和时间对该聚合反应转化率和聚合物平均分子量的影响规律。结果表明:采用V50引发混合溶剂沉淀聚合工艺,可制得高产率和高分子量的PAN共聚物。     

AN/MAA共聚物泡沫塑料泡体结构研究

通过烘箱自由发泡制备丙烯腈(AN)/甲基丙烯酸(MAA)共聚物泡沫塑料,讨论了该泡沫塑料泡孔平均孔径随泡沫塑料密度变化的规律,研究了成核剂和应力对泡沫塑料泡孔尺寸的影响,通过光学显微和电子扫描显微观察了该泡沫塑料的整体结构和微观结构.结果表明: AN/MAA共聚物泡沫塑料泡孔平均孔径随密度的增加而减小;碳酰胺能起到成核剂的作用,显著减小泡沫塑料泡孔尺寸;可发泡共聚物的应力发白现象能改善其发泡成核效果并使泡孔孔径大大减小;该共聚物泡沫塑料具有高闭孔率、各向同性的特征,其泡壁为三至七边形,泡棱由三个泡壁相交而成,泡壁体积分数随密度的增加而减小.     

用原位聚合法制备聚酰亚胺/滑石粉复合薄膜的聚集态结构

用原位聚合法合成一系列不同滑石粉含量的聚酰胺酸/滑石粉(PAA/talc)溶液,再将其热酰亚胺化制备出聚酰亚胺/滑石粉(PI/talc)复合薄膜.偏光显微镜(POM).广角X衍射(WXRD)和扫描电子显微镜(SEM)的观测结果表明,滑石粉的引入使PAA形成一种丝状有序结构,且随着热酰亚胺化的进行或者滑石粉含量的增加,这种结构不但得以保持且越来越明显,最终相互交错形成网状织构,红外光谱(FT-IR)给出的结果表明,滑石粉与PAA间存在氢键相互作用.丝状结构的形成,是在存在氢键的前提下滑石粉诱导被应力驱动的大分子链发生规整有序排列的结果.     

不同沉积工艺下Au/P-CdZnTe接触界面的研究

采用超声波扫描(SAM)、俄歇电子能谱分析技术(AES)、电极粘附力测试和I-V特性测试等方法研究了化学沉积、溅射和真空蒸发三种不同沉积工艺条件下Au/p-CdZnTe接触界面的各种特性.通过实验结果可以看出,化学法沉积的Au电极能形成较好的欧姆接触特性,但其操作工艺不容易控制,电极接触层均匀性较差,在器件使用过程中,容易引起电极的退化;溅射沉积的Au电极有着较好的附着力,但对CdZnTe表面的损伤较大,欧姆接触特性较差;真空蒸发法沉积的Au电极,有着较好的欧姆接触特性,且其电极接触层也较为均匀,只是电极附着力相对较小,但可以通过合适的退火工艺进行改善.     

Polyethylene/clay nanocomposites prepared by polymerization compounding method

A new technique for the preparation of high density polyethylene/clay nanocomposite, "polymerization compounding," is reported. This technique was based on the chemical anchoring of a Ziegler-Natta catalyst on organically modified clay surface containing an ammonium cation bearing primary hydroxyl groups. The polymerization of ethylene was initiated after adequate activation and the growing polyethylene chains are directly adsorbed on to the clay surface through the hydroxyl-functionalized surfactant. Finally, the nanocomposite was prepared by diluting polyethylene adsorbed clay in the high density polyethylene (HDPE) matrix using a batch mixer at 180 degrees C. The as-synthesized nanocomposite was typically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) that revealed the formation of intercalated nanocomposite. Tensile property measurements exhibit substantial increase in stiffness (approximately 50%) and strength (approximately 20%) of nanocomposite as compared to that of neat HDPE. Dynamic mechanical analysis under molten state revealed 25% increase in storage modulus when compared to that of neat HDPE.     

Antireflection coatings on plastics deposited by plasma polymerization process

Antireflection coatings (ARCs) are deposited on the surfaces of optical elements like spectacle lenses to increase light transmission and improve their performance. In the ophthalmic industry, plastic lenses are rapidly displacing glass lenses due to several advantageous features. However, the deposition of ARCs on plastic lenses is a challenging task, because the plastic surface needs treatment for adhesion improvement and surface hardening before depositing the ARC. This surface treatment is usually done in a multi-stage process—exposure to energetic radiations, followed by deposition of a carbonyl hard coating by spin or dip coating processes, UV curing, etc. However, this treatment can also be done by plasma processes. Moreover, the plasma polymerization process allows deposition of optical films at room temperature, essential for plastics. The energetic ions in plasma processes provide similar effects as in ion assisted physical deposition processes to produce hard coatings, without requiring sophisticated ion sources. The plasma polymerization process is more economical than ion-assisted physical vapour deposition processes as regards equipment and source materials and is more cost-effective, enabling the surface treatment and deposition of the ARC in the same deposition system in a single run by varying the system parameters at each step. Since published results of the plasma polymerization processes developed abroad are rather sketchy and the techniques are mostly veiled in commercial secrecy, innovative and indigenous plasma-based techniques have been developed in this work for depositing the complete ARCs on plastic substrates.     

Effects of different acetylene/nitrogen ratios on characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition

The effects of C₂H₂/(C₂H₂ + N₂) ratios on the characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition are investigated. The C₂H₂/(C₂H₂ + N₂) ratios are set to 60, 70, 80, 90, and 100%. Additionally, the deposition temperature, working pressure, and mass flow rate are 1003 K, 133 kPa, and 40 sccm, respectively. The deposition rate, microstructure, and electrical resistivity of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is elucidated. Experimental results indicate that the deposition rate increases with increasing the C₂H₂/(C₂H₂ + N₂) ratio, and the deposition process is located at a surface controlled regime. As the deposition rate increases, the electrical resistivity of carbon coatings increases, while the ordered degree, nano-crystallite size, and sp² carbon atoms of the carbon coatings decrease. Additionally, the low-temperature surface morphology of the carbon coatings shows that if the carbon coating thickness is not smaller than 289 nm, decreasing the deposition rate is good for producing hermetic optical fiber coatings.     

Characterization of amorphous hydrogenated carbon films deposited by MFPUMST at different ratios of mixed gases

Amorphous hydrogenated carbon films (a-C:H) on p-type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by Raman spectra, X-ray photoelectron spectroscopy (XPS), nano-indentation tests and spectroscopic ellipsometry. It is found that the sp ³ fraction increases with increasing Ar concentration in the range of 17–50%, and then decreases when Ar concentration exceeds 50%. The nano-indentation tests reveal that nano-hardness and elastic modulus of the films increase with increasing Ar concentration in the range of 17–50%, while decreases with increasing Ar concentration from 50% to 86%. The variations in the nano-hardness and the elastic modulus could be interpreted due to different sp ³ fractions in the prepared a-C:H films. The variation of refractive index with wavelength have the same tendency for the a-C:H films prepared at different Ar concentrations, they decrease with increasing wavelength from 600 to 1700 nm. For certain wavelengths within 600–1700 nm, refractive index has the highest value at the Ar concentration of 50%, and it is smaller at the Ar concentration of 86% than at 17%. The results given above indicate that ratio of mixed gases has a strong influence on bonding configuration and properties of a-C:H films during deposition. The related mechanism is discussed in this paper.