气相色谱法测定面粉中过氧化苯甲酰

在酸性条件下用碘化钾还原过氧化苯甲酰为苯甲酸 ,经有机溶剂提取后在 5 % ( m/ m) DEGS+1%( m/ m) H3PO4 固定液的 60— 80目 Chromosorb W AW玻璃柱上分离 ,以保留时间定性 ,峰面积定量 ,建立了气相色谱分析过氧化苯甲酰的新方法。检出限为 6.0× 10 -4 g/ kg。该法用于样品分析 ,结果令人满意     

过氧化苯甲酰的光敏电荷转移分解反应及引发甲基丙烯酸甲酯的聚合

过氧化苯甲酰(BPO)的光诱导分解曾为许多工作者所注意。Walling和Gibian认为:以二苯酮为敏化剂时,BPO的敏化光解是通过三重态的能量转移过程。Encinas和Lissi则认为敏化是通过单重激发态使激发能转移至过氧化物基态的热振动态,从而导致过氧化物的分解。Tokumarur是最早提出过氧化苯甲酰光敏化诱导分解过程中存在着激基复合物(Exciplex)的可能性。最近他们又进一步研究以BPO为猝灭剂去猝     

过氧化苯甲酰对多壁碳纳米管衍生化的研究

近年来,利用化学修饰制备可溶性的碳纳米管进行了很多研究,使得碳纳米管（CNTs）的衍生化成为一个热点。本文通过在苯溶剂中加热回流的方法实现了碳纳米管和过氧化苯甲酰氧自由基的加成反应。一方面通过红外光谱证明了过氧化苯甲酰氧自由基和多壁碳纳米管之间的类烯加成反应,另一方面通过热重分析研究了反应产物与反应时间和反应物比例之间关系,说明了过氧化苯甲酰对碳纳米管衍生化的影响。     

Chemical initiation of graft copolymerization of methyl methacrylate onto styrene–butadiene block copolymer

When a solution containing both styrene–butadiene block copolymer (SBS) and methyl methacrylate is treated with an initiator both homopolymerization of the methyl methacrylate and graft copolymerization of the methyl methacrylate onto the SBS occur. The amount of graft copolymerization depends upon the time and temperature of the reaction, the concentrations of all species, and the identity of the solvent and initiator. The combination of benzoyl peroxide in chloroform gives the highest graft yield and the reaction occurs by removal of an allylic hydrogen from the SBS by the initiator radical and subsequent addition of monomer units to that site; there is a significant solvent effect. Both AIBN and BPO function by the removal of an allylic hydrogen atom from SBS; BPO is able to effect this reaction relatively easily while AIBN can remove the hydrogen atom only with great difficulty and to a limited extent. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 965–974, 1997     

Flux growth of BPO4 crystals

Single crystals of BPO₄ with sizes up to 15×10×12 mm³ were grown by top-seeded solution growth method using Li₂O–Li₄P₂O₇ as fluxes. The components volatilized from the melt were characterized by the method of X-ray powder diffraction. The defects of grown crystals have also been investigated. The measured ultraviolet cutoff edge of BPO₄ was about 130 nm. Its density was 2.82 g/cm³ determined using drainage method.     

BaBPO5晶体的生长研究

本文采用顶部籽晶高温溶液法,以BPO4-NaF为助熔剂,生长了BaBPO5单晶.生长参数:液面以下温度梯度为1.5℃/cm,液面上温度梯度为10℃/cm,晶体旋转速度30r/min,降温速率0.5-1℃/d,可获得尺寸为30mm×20mm×15mm的BaBPO5单晶.测定了所获单晶及其挥发物的X射线粉末衍射图谱,讨论了助熔剂对BaBPO5晶体生长的影响和该晶体的物化性能.     

单一成本目标数据处理服务外包业务工艺规划研究

本文对数据处理服务外包业务工艺规划所涉及的要素——成品数据要求、工艺方法、工序排序和设备工具进行了分析,结合数据处理业务流程特点,采用数学规划方法建立了非线性优化模型。在综合比较各类求解非线性规划的方法的基础上,鉴于遗传算法具有编码容易、搜索速度快以及鲁棒性等优点,选择遗传算法求解单目标优化问题。通过选取实际企业数据,利用MATLAB编程求解,验证了本文结果的适用性。     

STUDY OF THE EFFECT OF TWO BPO/AMINE INITIATION SYSTEMS ON THE FREE-RADICAL POLYMERIZATION OF MMA USED IN DENTAL RESINS AND BONE CEMENTS

ABSTRACT

The kinetics of the free radical bulk polymerization of methyl methacrylate (MMA) was studied by DSC, using the benzoyl peroxide (BPO)/amine initiation system. N,N dimethyl-4-aminophenethyl alcohol (DMPOH), which is a newly synthesized and used amine in the preparation of acrylic dental resins and bone cements was examined, and the results compared to the most commonly used in these applications amine, the N,N dimethyl-p-toluidine (DMT). For both amines, the effect of the molar ratio of BPO/amine and of the reaction temperature, on the polymerization kinetics was investigated. The prepared polymers were characterized by determination of the average molecular weights (M¯ _n and M¯ _w ) and molecular weights distribution (M¯ _w /M¯ _n ) using Gel Permeation Chromatography. DMPOH was found to lead in slightly higher polymerization rates, lower gel times and lower molecular weights than DMT. The values of these parameters for both amines were influenced by the molar ratio of BPO to amine, when the product of the concentrations of these was kept constant. The highest polymerization rate occurred in the lowest gel time, resulting in polymers with the lowest molecular weight, and was observed when a molar ratio of about 1.5 BPO/amine was used. However, the final monomer conversion was found to be independent of the molar ratio and amine used. The activation energy of polymerization was found to be 51.8 kJ/mol K for BPO/DMPOH and 47.1 kJ/mol K for BPO/DMT.