Polymerization of epoxy resins initiated by metal complexes

BACKGROUND: Processing parameters and material properties of epoxy resins can be vastly influenced by choice of curing agent. In this work, metal complexes were investigated as initiators for anionic and cationic epoxide polymerization. Systems for thermally induced and electron beam‐induced curing are described. RESULTS: Zinc or cobalt imidazole complexes of the type [M(imidazole)₂(anion)₂] are efficient initiators for anionic polymerization of glycidyl‐based epoxy resins. The complexes can be employed to prepare tailored resin systems ranging from fast curing systems at slightly elevated temperatures to systems with very high thermal latencies curable at temperatures far above 150 °C. Silver complexes [Ag(L)_n]SbF₆ (L = crown ether or alkene) are highly efficient initiators for cationic curing and low initiator contents of around 1% are sufficient to reach high degrees of crosslinking. The complexes are excellent initiators for both thermally induced and electron beam‐induced polymerizations. CONCLUSION: Metal complexes are powerful initiators for the homopolymerization of epoxy resins and can be designed not only for anionic and cationic polymerization but also for thermal and radiation curing. Based on this study and additional work, a library can be compiled which allows retrieval of optimized metal–ligand–anion combinations and adjustment of the initiators to the respective processing and material demands. Copyright © 2009 Society of Chemical Industry     

Crosslinking of mixtures of diglycidylether of bisphenol‐A with 1,6‐dioxaspiro[4.4] nonan‐2,7‐dione initiated by tertiary amines: III. Effect of hydroxyl groups on network formation

BACKGROUND: Blends of epoxy resin oligomers, diglycidylether of bisphenol‐A (DGEBA), and a bislactone, 1,6‐dioxaspiro[4.4]nonan‐2,7‐dione (s(γBL)), were anionically copolymerized using two tertiary amines as anionic initiators. Their curing rheology and gelation behaviour were studied to provide a more comprehensive knowledge of the curing of these previously studied systems. RESULTS: The activation energy for gelation was found to be similar to that previously measured using differential scanning calorimetry and appeared to increase in the presence of the bislactone. The reaction rate during copolymerization of DGEBA with s(γBL) was slower than DGEBA homopolymerization alone because the alkoxide attack on the epoxide is faster than the reaction of the carboxylate ion and the epoxy group. The effect of the initiator type on the gel conversion was small and was presumably due to differences in the kinetic chain length caused by amine regeneration from the quaternary amine. For the same initiator and at a constant ratio of DGEBA/s(γBL), an increase in the hydroxyl concentration of the DGEBA oligomer raised the gel conversion. For a DGEBA oligomer with low hydroxyl levels, an increase in the concentration of s(γBL) increased the gel conversion; however, for a DGEBA oligomer with high hydroxyl levels, increasing s(γBL) concentration decreased the gel conversion. CONCLUSION: These results are interpreted in terms of the effect of initiation rate and chain transfer rate on the kinetic chain length. The glass transition temperature of the gel was found to be controlled by the fraction of the aliphatic s(γBL) and the amount of plasticizing sol in the matrix. Copyright © 2009 Society of Chemical Industry     

无水AlCl_3作用下EPDM的交联与接枝性能

以无水AlCl3为催化剂,在溶液体系考察了温度、催化剂用量、溶剂品种等因素对乙丙三元橡胶(EPDM)交联与接枝性能的影响。结果显示,无水AlCl3可以引发EPDM间产生交联反应;温度较低时,EPDM交联反应困难,但乙丙三元橡胶与聚苯乙烯(PS)间产生了接枝反应;在苯与二甲苯溶剂中不易形成活性正碳离子;催化剂用量增大,凝胶含量与交联密度增大;PS进入EPDM凝胶网络,使PS相热稳定性提高,玻璃化温度提高。     

水泥基高强材料的发展

本文综述了几种新型的高强水泥基材料.着重介绍了热压浆体、DSP 材料、MDF 水泥以及PSC 材料的工艺特点和性能.特殊的成型工艺表明,水泥基材料在力学性能上存在着很大的潜力,通过对水泥基材料在不同层次上的改性,可以使水泥、混凝土这种脆性材料具有高强、高韧性、加入有机、无机外掺物,减小孔率都是提高强度的极有效方法.通过对材料在不同层次上的改性,可望设计、制造出具有特殊性能的水泥基材料.     

炭黑表面接枝改性

综述炭黑表面接枝聚合改性及表征方法，着重介绍自由基接枝、阳离子接枝及阴离子接枝等三种方法。     

固相接枝聚丙烯的晶态结构和热行为

采用广角Ｘ射线衍射（ＷＡＸＤ）和差示扫描量热法（ＤＳＣ），研究固相接枝反应对聚丙烯晶态结构和热行为的影响。结果表明聚丙烯用马来酸酐固相接枝后，晶面间距基本不变，微晶尺寸增大，熔点降低，结晶度略有提高。     

2—甲基丙烯酰胺接枝共聚蚕丝纤维工艺及应用研究

蚕丝纤维与2-甲基丙烯酰胺接枝共聚采用液相法.本文在工艺研究的基础上重点研究放样工艺、染色和织造工艺.对接枝共聚后的蚕丝纤维织物的物理性能进行了测试,并探讨了工业实施方案.     

聚硅氧烷接技改性丙烯酸树脂的研究

本文介绍了聚硅氧烷接技改性的带羟基的丙烯酸树脂的研究工作,通过选择适当的实验条件使它们接枝共聚,同时研究了各种因素对它们的影响.通过改性,丙烯酸树脂的综合性能有了显著的提高.具有与有机硅树脂相似的耐热、耐水、耐老化的特点,其成本较低,用途广泛,具有良好的市场前景.     

BDC引发苯乙烯均相聚合反应机理的进一步探讨

BDC引发苯乙烯的均相聚合反应是以活性自由基机理进行的;大分子自由基间的偶合反应及向大分子的链转移反应使聚合产物不带有活性端基;大分子链活性端基数的测定结果表明了这种失活性的存在。     

Chloro-Nickel and Chloro-Cobalt Complexes Containing Phosphine Ligands: Efficient Initiators for Polymerization of Alkynes

We have developed a new series of single-component air- and moisture-stable catalysts for alkyne polymerization based on chloro-nickel and chloro-cobalt complexes containing phosphine ligands. The polymerization of p-diethynylbenzene initiated by these complexes proceeds smoothly in the presence of amines at room temperature to afford soluble -conjugated polymers in yields as high as 81% with weight-average molecular weight up to 17 600.