在碳纤维表面原位浸渍聚合尼龙6的工艺探究

为了在碳纤维生产线上配备碳纤维/尼龙6复合材料在线生产装置,探究了一种通过纤维活化原位浸渍聚合法在碳纤维表面合成尼龙6的方法,即先在碳纤维表面包覆一层活化剂TDI(2,4-甲苯二异氰酸酯),将纤维活化,再将活化后的纤维通过预先对己内酰胺与引发剂氢氧化钠体系除水而获得的单体阴离子熔体中,通过单体阴离子扩散聚合在纤维表面形成一层尼龙6。研究表明,采用该纤维活化原位浸渍聚合方法可以成功地在碳纤维表面形成一层尼龙6树脂,但聚合温度对尼龙6的转化率、熔融结晶行为和分子量影响较大,过量的活化剂对尼龙6的转化率也存在不利影响,如果改进活化剂配比,将会提高聚合物的转化率。最后通过红外、电镜扫描(SEM)对材料的官能团分布和微观形貌进行了研究。     

引发剂和活化剂用量对MC尼龙性能的影响

通过改变催化剂(包括引发剂和活化剂)用量合成四个系列MC尼龙,研究了引发剂和活化剂用量的变化对MC尼龙合成、结构和力学性能的影响。实验结果表明：引发剂和活化剂的用量对MC尼龙的对聚合速率、单体转化率、结晶度和结晶温度有一定的影响,同时也对拉伸强度、缺口冲击强度、弯曲强度和弯曲模量影响很大。     

阴离子开环聚合合成超高相对分子质量聚硅氧烷

以二甲基硅氧烷混合环体(DMC)为单体,四甲基氢氧化铵硅醇盐为引发剂,通过阴离子开环聚合制备了固态透明的超高相对分子质量聚硅氧烷,研究了聚合体系含水量、引发剂用量以及温度对聚硅氧烷相对分子质量的影响。结果表明:聚合体系的低含水量(10×10~(-6))是得到超高相对分子质量聚硅氧烷的关键因素;在低含水量条件下,通过调节引发剂质量分数为0.28%~1.10%,可以控制聚硅氧烷的相对分子质量为(0.84~1.60)×10~6;聚合温度为105~115℃时,可以快速得到超高相对分子质量线型聚硅氧烷。     

链转移剂调控DMDAAC均聚物分子量

以工业级二甲基二烯丙基氯化铵(DMDAAC)为反应单体、甲酸钠或甲醇为链转移剂,选择过硫酸铵-亚硫酸氢钠氧化还原引发体系,采用水溶液聚合法得到分子量在800～9000的PDMDAAC.通过正交实验考察了单体质量分数、聚合温度、聚合时间、聚合体系pH值、引发剂用量、还原剂用量和链转移剂用量对聚合产物特性粘数和单体转化率的影响.研究了链转移剂对PDMDAAC分子量的调控作用及其用量对聚合物特性粘数和单体转化率的影响规律.     

真空导入成型阴离子聚合尼龙6及其复合材料中活化剂的作用研究

通过真空导入成型的方法制备阴离子聚合尼龙6(APA-6)纯样及其玻纤复合材料,选用己内酰胺钠盐(C10)作为引发剂,双酰化内酰胺-1,6-己二胺(C20)和2,4-甲苯二异氰酸酯(TDI)作为活化剂,研究了活化剂对制品性能的影响。结果表明,由于活化机理不同,当TDI作为活化剂时,体系在聚合前具有较长的导入时间窗口,聚合过程中产生更多长的支链,从而使制品结晶度下降,但是支链之间缠结反而有利于此体系得到的纯APA6具备较优的力学性能。最后,TDI作为活化剂时,树脂与纤维之间产生更强的界面作用,复合材料力学性能更优。     

叔碳酸乙烯酯改性醋酸乙烯酯乳液的研制

采用半种子连续乳液聚合的方法，以过硫酸钾为引发剂，以十二烷基硫酸钠和OP—10复配为乳化剂，合成了叔碳酸乙烯酯／醋酸乙烯酯共聚乳液。研究了乳化剂的用量、阴离子／非离子质量比和叔碳酸乙烯酯用量对乳液性能的影响；引发剂用量、聚合温度、种子单体加入量以及单体进料速率对聚合过程的影响。乳化剂用量为3％、阴离子／非离子为1：1、叔碳酸乙烯酯用量为30％；聚合温度为76℃、引发剂用量为0．4％、种子加入量为10％、进料周期为4h，聚合过程稳定，乳液性能良好。     

超高分子量阴离子型聚丙烯酰胺P(AM-AC)的制备研究

以丙烯酰胺(AM)与丙烯酸(AC)为反应单体,采用水溶液聚合法在复合引发体系下制备超高分子量阴离子聚丙烯酰胺,重点探讨引发剂的用量、单体浓度、初引发温度、pH值等因素对聚合物特性黏数的影响.实验结果表明,最佳的制备工艺参数如下:氧化还原引发剂的质量分数为0.025％,二级引发剂偶氮二异丁咪唑啉盐酸盐(V-44)的质量分...     

固体沥青改性用丁苯胶乳的工艺研究

以丁二烯和苯乙烯为单体,采用阴离子乳化体系,在过氧化物与亚铁盐构成的氧化还原引发体系作用下,合成了性能良好的固体沥青改性用丁苯胶乳,讨论了影响聚合过程及胶乳性能的因素。结果表明,单体配比、乳化剂浓度、引发剂浓度、分子质量调节剂用量及聚合温度是控制丁苯胶乳性能的关键因素,分批加入乳化剂及梯度控温有利于控制胶乳门尼粘度和结...     

苯基聚硅氧烷的非均相制备与聚合机理研究

以固相八苯基环四硅氧烷、八甲基环四硅氧烷作为共聚单体,四甲基氢氧化铵为引发剂进行阴离子开环本体聚合,结合反应物、产物的全程监测分析对聚合过程进行了系统研究,并探讨了其共聚动力学。     

聚丙烯酸钠盐高吸水性聚合物的研制

本文以丙烯酸为单体,以脂肪族碳水化合物为溶剂,在乳化剂存在下,采用自由基聚合引发剂进行反相乳液聚合,当反应终止时,将聚合体系冷却降温,再次将含有引发剂的单体倒入该体系中,升温聚合。研究了此二步聚合法的工艺条件;考察了温度、吸水介质、粒径、吸水时间对吸水率的影响。     

阴离子淤浆聚合尼龙6的性能研究

通过阴离子淤浆聚合方法,以氢氧化钠为催化剂、异氰酸酯作活化剂,以惰性脂肪烃为分散剂,在不同的反应时间和140～150℃温度下,制得了不同相对分子质量的尼龙6,最高相对粘度17．5。通过熔融纺丝,获得了可纺性良好的纤维,其断裂强度5．0～6．9 cN／dtex。X衍射测试分析表明,同阴离子本体聚合尼龙6(MC尼龙6)和高粘度尼龙6比较,阴离子淤浆聚合尼龙6在二次成型中更易于生成轫性较好的γ晶型,具有更高的冲击强度。     

Graft copolymerization of ϵ-Caprolactam onto Kevlar-49 fiber surface and properties of grafted Kevlar fiber reinforced composite

The anionic graft copolymerization of ϵ-caprolactam onto a Kevlar-49 fiber surface was carried out by using a metalation reaction in a dimethyl sulfoxide solution of sodium hydride. The effects of reaction conditions on the graft yield and on the tensile strength of the fiber have been investigated. Graft yield significantly increased with increasing metalation time, NaH concentration, and monomer concentration. The graft yield varied from 6 to 32% with reaction conditions. The tensile strength of the fiber depended predominantly on NaH concentration. The retained tensile strength was over 93% when the concentration of NaH was below 2.1 mmol/L per 0.5 g of Kevlar. The discontinuous Kevlar fiber reinforced composites were prepared by a blending/melt-pressing method. In thermomechanical and dynamic mechanical analyses, the relaxation peak of grafted Kevlar fiber/Nylon 6 composite film moved to higher temperatures, compared with the original Kevlar fiber/Nylon 6 composite film. The grafted Kevlar fiber reinforced Nylon 6 composite film exhibited mechanical properties superior to those of the original Kevlar fiber reinforced composite film. The higher thermal and mechanical properties were due to the effect of higher interfacial interaction between the grafted Kevlar fiber and matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 99–107, 1997     

Die polymerisation der lactame XIV. Einfluß des hexamethylguanidiniumchlorides auf die aktivierte anionische polymerisation der lactame

It was proved that hexamethylguanidiniumchloride (HMGC) exhibited a pronounced accelerating effect on the activated anionic polymerization of 2-pyrrolidone (40°C) and 6-caprolactam initiated by alkali metal salts of the corresponding lactams. The accelerating effect of HMGC was not specific for a certain type of alkali metal salt of lactams as initiator, it was proved that the effect is operative for polymerization of 6-caprolactam when using sodium or cesium salt of 6-caprolactam. It was proved that HMGC does not form growing centers under reaction conditions studied. The initial polymerization rate in the homogeneous phase is a linear function of square root of HMGC concentration at constant concentrations of initiator and activator. On the basis of this finding it was possible to suggest a plausible mechanism of HMGC influence on the polymerization process.     

Polymerization of lactams, 28. Effect of reaction conditions on the anionic polymerization of 2-pyrrolidone (part 5)

The effect of temperature, activator concentration, and polymerization time on the anionic polymerization of 2-pyrrolidone was studied using the method of statistical planning of the experiments. Sodium tert-butoxide or sodium dihydrido-bis(2-methoxyethoxy)aluminate was used as initiator; N-acetylpyrrolidone served as activator in both cases. Results obtained with both initiation systems were presented in the form of explicit mathematical equations.     

Functionalization of multiwalled carbon nanotubes with polyamide 6 by anionic ring-opening polymerization

Covalent functionalization of multiwalled carbon nanotubes (MWCNTs) with polyamide 6 was accomplished by anionic ring-opening polymerization of ε-caprolactam in the presence of sodium caprolactamate as a catalyst and caprolactam functionalized MWCNTs as an initiator. The initiator precursor, isocyanate functionalized MWCNTs, was prepared by directly reacting commercial hydroxyl functionalized MWCNTs with excess toluene 2,4-diisocyanate. This anionic ring-opening polymerization was found to occur in a highly efficient manner at relatively low reaction temperature (170 °C) and short reaction times (6 h). FTIR spectroscopy was utilized to follow the introduction and consumption of isocyanate groups on the MWCNTs. Thermogravimetric analysis indicated that the polyamide 6 was successfully grown from the MWCNT surface, with the final products having a polymer weight percentage of ca. 40-65 wt%. Transmission electron microscopy was utilized to image the polymer-functionalized MWCNTs, showing relatively uniform polymer coatings presented on the surface of MWCNTs.     

多官能度聚乙二醇的合成研究

以D-山梨醇为引发剂,二甲亚砜为溶剂,氢氧化钾为催化剂,环氧乙烷为单体,阴离子开环聚合合成了多官能度聚乙二醇。详细考察了催化剂、引发剂、溶剂、聚合温度等因素对聚合产物的性能影响。初步确定了聚合条件,聚合温度100～110℃,聚合时间6h。通过官能度的理论计算和测试证明合成的聚合物为多官能度聚乙二醇。     

新型低温型聚丙烯酸酯乳液的合成

采用种子乳液聚合法合成新型低温反应型聚丙烯酸酯乳液粘合剂,即以丙烯酸丁酯（BA）、丙烯酸异辛酯（EHA）、苯乙烯（St）为软、硬单体,丙烯酸（AA）为功能单体,以过硫酸钾为引发剂,并选用一种适当的交联单体合成了性能优良的聚丙烯酸酯涂料印花粘合剂。讨论了引发剂用量、乳化剂用量、阴／非离子乳化剂的配比、乳液滴加时间、保温时间等对聚合物的影响。确定了乳液聚合最佳工艺条件：乳化剂用量为o8％,阴／非乳化剂质量比为4：3,引发剂用量为0．8％,乳液滴加时间60min,保温时间60min。     

Reaction Kinetics for the Anionic Ring-Opening Polymerization of Tetraphenyltetramethylcyclotetrasiloxane Using a Fast Initiator System

It is well known that the rate of polymerization for an anionic mechanism is dependent on the ability of the bulk material or solvent system to disassociate the ion pair at the propagating chain end. In the anionic ring-opening polymerization of cyclic organosiloxanes in particular, the larger and softer the counter ion, the more rapidly the reaction proceeds. A recently developed phosphazene initiator system provides a large, soft counter ion relative to other traditional initiators used for the polymerization of poly(dimethylsiloxane) (PDMS). This novel initiator system was used in this investigation for the ring-opening polymerization of tetraphenyltetramethylcyclotetrasiloxane (P₄) and the reaction kinetics under bulk and solution conditions were investigated. The new initiator system showed a dramatic increase in the rate of polymerization over the conventional potassium hydroxide-catalyzed system. Furthermore, this initiator was sufficiently reactive to be useful for the ring-opening polymerization of P₄ at 293 K.     

Herabsetzung der niedermolekularen Anteile in alkalisch hergestelltem Polyamid 6

The content of low-molecular substances in polymers usually influences their effective properties and appearance in a negative way, therefore means to reduce it have been investigated. This applies also to polyamide mouldings produced by anionically activated polymerization of 6-caprolactame. The concentration of low-molecular substances in prepared samples was reduced by the action of residual initiator and activator centres inducing additional polymerization in the system at elevated temperature. The influence of the initiator and activator concentration at different times of additional polymerization on the yield of polyamide and its degree of polymerization was studied. The results proved that the content of low-molecular substances was decreasing with increasing time of additional polymerization. The highest effect appears in the initial phase of additional polymerization which is advantageous especially for practical applications of this method to improve the properties and appearance of polyamide mouldings.     

Synthesis and characterization of polyvinyl acetate/montmorillonite nanocomposite by in situ emulsion polymerization technique

Exfoliated polyvinyl acetate/montmorillonite nanocomposite (PVAc/MMT) was prepared via in situ emulsion polymerization. The resulting PVAc with various organophilic MMT contents was investigated. In the nanocomposite latex preparation, sodium lauryl sulfate (SLS), ammonium persulfate (APS), and poly (vinyl alcohol) (PVA) are used as anionic emulsifier, conventional anionic initiator, and stabilizer, respectively. The samples were characterized using elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). The XRD and AFM results demonstrate that the MMT well dispersed at molecular level in the PVAc matrix. Thermal properties of the nanocomposite were studied by using differential scanning calorimetric analysis (DSC). The exfoliated PVAc/MMT nanocomposite showed a higher glass transition temperature and a better thermal stability compared to the pure PVAc.