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1.
稀土掺杂PVC的紫外及微波交联研究   总被引:3,自引:1,他引:2  
聚氯乙烯 (PVC)是我国目前产量最大 ,应用面最广的高分子原材料。但其耐热性、稳定性及抗老化性都较差。我们考虑到使用稀土掺杂以改进其相关性能 ,同时掺入了少量从水玻璃中提取出来的活性硅醇到PVC中以增加其柔性 ,探索了紫外辐射交联和微波辐射交联对PVC机械力学性能的影响。本文采用PVC流延膜来进行辐射交联并测定样品的力学性能。结果发现 ,稀土掺杂的结果使得样品的扯断伸长率大幅度提高 ,拉伸强度上升显著。而添加活性硅醇后PVC流延膜的扯断伸长率进一步提高 ,拉伸强度则下降 ,柔性得以提高。将氯化钕溶于 95 %的乙醇…  相似文献   

2.
聚合物强化辐射交联研究进展   总被引:1,自引:0,他引:1  
本文综述卫应用含有多个C=C不饱和基团的多官能团单体来强化辐射交联聚合物的研究进展,对强化交联的反应机理、多官能团单体的强化交联行为、强化交联的影响因素及强化交联的研究表征方法进行了介绍。  相似文献   

3.
在开发出催化性能良好的合成MTBE沸石分子筛催化的基础上,详细考察了反应条件:包括温度、压力、空速、醇烯比等操作条件对改性β沸石分子筛催化剂的合成MTBE反应性能的影响。结果表明:反应条件对催化剂活性、MTBE选择性及活性稳定性都有一定影响。在一定范围内反应温度升高,烯烃的转化率增加、MTBE的选择性不变,但反应温度过高,MTBE的选择性和催化剂的稳定性变差;反应压力必须大于系统完全液化压力;醇烯  相似文献   

4.
聚乙烯在室温下几乎不溶于任何有机溶剂。所以,较低分子量有机化合物对聚乙烯辐射交联影响的研究受到很大限制。本文将具有端基双键的正-1-十六烯和相应的正-十六烷分别溶胀在固态聚乙烯中,观察了这两种较低分子量有机分子对聚乙烯辐射交联和不饱和度的影响。结果表明,分别溶胀在聚乙烯中的两种有机分子对聚乙烯的辐射交联有不同程度的抑制作用,对聚乙烯辐照后不饱和度的变化亦有明显影响,进一步证实了PE不饱和的端双键基Y型交联是聚乙烯辐射交联优先发生的主要方式。  相似文献   

5.
温斌  何鸣元 《分子催化》2000,14(2):93-96
以ZSM-5和锐钛矿为原料,利用离子交换和等量浸渍法制备了3种催化剂,模拟FCC再生器条件,以CO为还原剂,分别考察了反应温度及尖体系中氧气的浓度、水蒸汽和二氧化硫的存在对催化剂DeNOx性能的影响。结果表明,低温(≤550℃)时催化剂的活笥很低;氧气的存在使催化剂的DeNOx活性降低;H2O的存在有利于催化剂低温(≤550℃)活笥的提高,但对不同催化剂在720℃时的活笥却有不同的影响;反应体系中  相似文献   

6.
稀土改性PVC膜的制备及性能研究   总被引:2,自引:0,他引:2  
利用硝酸稀土作为改性剂,加入到聚氯乙烯(PVC)的四氢呋喃(THF)溶液中,用流延法制得表观透明均匀的PVC膜,经紫外辐射交联后,测试其力学和物理性能,发现经稀土改性后的PVC薄膜的力学和物理性能均有了较大的提高。  相似文献   

7.
研究了聚酯丙烯酸酯 (PEA)类多官能团物质与聚己内酯 (PCL)共混物的辐射交联效应 .分别考察了多官能团PEA的用量、官能团数目、辐射交联剂量等因素对聚己内酯的辐射交联规律、动态力学性能、形状记忆行为等性能的影响 .结果表明 ,PCL PEA共混物的辐射交联规律不再遵从Charlesby Pinner关系式 ,而是符合陈欣方 刘克静 唐敖庆关系式 .多官能团PEA的加入可以显著提高PCL辐射交联的效率 ;相同剂量时 ,官能团数目越多、用量越大的样品 ,生成的凝胶含量越多 ,强化辐射交联效应越大 .DMA分析表明 ,PCL强化辐照交联后的弹性模量和耐热性能显著提高 .强化交联PCL在其熔点以上都呈现出高弹态平台 ,可以实现形状记忆 .且交联度较高 ,形状记忆恢复速率较快 .  相似文献   

8.
根据x射线、电镜、DSC和凝胶分数的测试结果,讨论了多官能团单体结构对低密度聚乙烯聚集态结构的影响以及结晶度与辐射交联(或剂量)的关系。发现由于单体的存在导致低密度聚乙烯结晶度增加而结晶尺寸变小(即结晶成核效应);成核效应越大,增强辐射交联的效果也越大。添加具有高结晶成核作用的单体有利于低密度聚乙烯的辐射交联,同时也加速其结晶结构的破坏。  相似文献   

9.
辐照对聚己内酯结构和性能的影响   总被引:7,自引:2,他引:5  
研究了γ 辐照对不同分子量的聚己内酯 (PCL)的力学性能、热性能、结晶行为的影响 ,在此基础上 ,研究了辐射交联后的PCL的形状记忆行为 .研究结果表明 ,PCL的分子量越大 ,辐射交联所需的凝胶化剂量越低 .溶胶分数S +S1 2 与 1 D的关系很好地符合Charlesby Pinner关系式 ,说明PCL的辐射交联属于无规交联 .剂量对PCL的力学性能影响显著 ,剂量越大 ,抗张强度和断裂伸长率下降越多 ,但分子量较高的PCL的抗张强度受剂量的影响较小 .DMA分析表明 ,聚己内酯辐照交联后的弹性模量和耐热性能显著提高 .交联度较高的PCL表现出高弹态 ,可以拉伸 ,并具有较好的形状记忆行为 .DSC分析表明 ,辐射交联使PCL的结晶度有所增加 ,但也使结晶熔点有所降低  相似文献   

10.
铜对钌改性尖晶石催化剂结构和氧化性能的影响   总被引:4,自引:0,他引:4  
通过湿化学法制备钌改性的纳米尖晶石MnFe1.95Ru0.05O4催化剂, 考察了添加助剂铜对该催化剂的影响.通过比表面积和孔径分布表征结果证实, 铜助剂的添加有效地增大了比表面积和孔容.XPS的测试结果表明, 钌的改性大大改变了尖晶石中各元素如锰和铁的化学环境;助剂铜的添加对于锰和铁等原子的影响不大, 但对钌原子的影响显著;EXAFS表征结果显示了铜助剂的导入影响了钌的周围环境, 形成了活性Ru=O键.以桂皮醇和苯甲醇的氧化反应为典型反应考察了添加助剂铜前后的影响.  相似文献   

11.
研究了含乙烯基和硅氢键的聚硅氮烷(ViHPSZ)在氯铂酸催化下的交联过程。用FTIR、TG-DSC研究了其热行为并对结构进行了表征,同时考察了陶瓷产物的致密性。结果表明,氯铂酸催化剂经活化处理可催化ViHPSZ交联。交联主要以硅氧化反应方式进行,聚硅氮烷在交联过程中重量损失少,产物密度较高。  相似文献   

12.
《先进技术聚合物》2018,29(5):1497-1506
The cross‐linking effects of cross‐linked ethylene‐tetrafluoroethylene copolymer (XETFE)‐insulated cables at different electron beam radiation doses were analyzed in this paper. Evaluation of the mechanical performance of the cables revealed that the highest tensile and breaking elongation was achieved at a radiation dose of 8 × 104 Gy and that XETFE had a good resistance to extreme electron beam irradiation. This is attributed to the cross‐linking effects induced by electron beam irradiation, and this takes full advantage of the strength of molecular chain crosslink to each other. The crystallization kinetics of XETFE at different electron beam radiation doses were studied in detail in terms of the non‐isothermal and isothermal crystallization processes. The results indicated that the crystallinity of the XETFE domain increased with an increase in the radiation dose as a result of heterogeneous nucleation. Moreover, the highest ΔEa was obtained, indicating that XETFE absorbed some energy at a radiation dose of 8 × 104 Gy. These kinetic parameters had help in carrying out a comprehensive evaluation of the performance of XETFE‐insulated cables for aerospace applications. Moreover, the fluoride precipitation observed in this study indicated that upon electron beam irradiation, XETFE could internally produce hydrogen fluoride, which is corrosive to metals. Thus, optimizing the radiation dose was necessary to achieve the desired performance. We could believe that the improvement for properties of electron beam XETFE insulation cables would expand their range of applications in the aerospace field.  相似文献   

13.
Amphiphilic block poly(propylene carbonate)‐block‐allyloxypolyethyleneglycol (PPC‐b‐APEG) copolymer was synthesized by the click chemistry, and its structure were characterized. PPC‐b‐APEG can self‐assemble into micelles without emulsifier in water. Shell cross‐linked micelles were obtained by the reaction of the allyloxy groups, which were exposed on the outer of the PPC‐b‐APEG micelles, and N‐vinylpyrrolidone (NVP). The morphology and size of the micelles before and after cross‐link reactions were characterized. The research result shows that the shell cross‐linking could improve the stability of micelles. The particle size of uncross‐linked micelle was about 800 nm. The size of cross‐linked micelles increased with increasing amount of cross‐linking degree. To better evaluate the release behavior of PPC‐b‐PEG copolymer, doxorubicin (DOX)‐loaded micelles were synthesized using DOX as the model drug. Results showed that the DOX releasing rate decreased with increasing of NVP. The shell cross‐linking do decrease the burst release behaviours of DOX and reduce the DOX release rate.  相似文献   

14.
The in situ nanoscopic imaging of soft matter polymer structures is of importance to gain knowledge of the relationship between structure, properties, and functionality on the nanoscopic scale. Cross‐linking of polymer chains effects the viscoelastic properties of gels. The correlation of mechanical properties with the distribution and amount of cross‐linkers is relevant for applications and for a detailed understanding of polymers on the molecular scale. We introduce a super‐resolution fluorescence‐microscopy‐based method for visualizing and quantifying cross‐linker points in polymer systems. A novel diarylethene‐based photoswitch with a highly fluorescent closed and a non‐fluorescent open form is used as a photoswitchable cross‐linker in a polymer network. As an example for its capability to nanoscopically visualize cross‐linking, we investigate pNIPAM microgels as a system known with variations in internal cross‐linking density.  相似文献   

15.
The physicochemical, thermomechanical, and elastic-strength characteristics of samples based on an oligoetheracrylate binder cured both under the action of only coherent UV radiation and with subsequent aftercuring in a UV oven were studied. It was established by differential scanning calorimetry that full curing of the polymeric matrix is not achieved by coherent UV radiation. The use of additional treatment in a UV oven leads to the formation of a denser three-dimensional cross linking, which increases the brittleness of the polymeric matrix. The introduction of 16A electrocorundum as a filler into the polymeric matrix decreases the thermomechanical and elastic-strength characteristics of an oligoetheracrylate binder regardless of the curing mode.  相似文献   

16.
Rubber magnetic composites were prepared through the incorporation of magnetic soft lithium ferrite into acrylonitrile butadiene rubber. Standard sulfur‐based curing and peroxide curing systems were used for cross‐linking of rubber matrices. The experimental part was focused on the investigation of ferrite content and curing system composition on cross‐link density, physical‐mechanical, magnetic and shielding characteristics of composites. The results demonstrated that cross‐link density and physical‐mechanical properties of composites can be modified by both the amount of ferrite and composition of the curing system. The influence of curing systems on magnetic properties was negligible. It can be stated that the application of lithium ferrite to rubber matrix leads to the preparation of rubber composites with the ability to efficiently absorb harmful electromagnetic radiation in the tested frequency range. The shielding efficiency of composites increased with increasing content of magnetic filler.  相似文献   

17.
To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross‐linking. This model is able to predict the temporal and spatial distribution of generated cross‐links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model takes account of the initial riboflavin concentration and bleaching, light intensity and time of illumination.  相似文献   

18.
Chemical cross‐linking, combined with mass spectrometry, has been applied to map three‐dimensional protein structures and protein–protein interactions. Proper choice of the cross‐linking agent, including its reactive groups and spacer arm length, is of great importance. However, studies to understand the details of reactivity of the chemical cross‐linkers with proteins are quite sparse. In this study, we investigated chemical cross‐linking from the aspects of the protein structures and the cross‐linking reagents involved, by using two structurally well‐known proteins, glyceraldehyde 3‐phosohate dehydrogenase and ribonuclease S. Chemical cross‐linking reactivity was compared using a series of homo‐ and hetero‐bifunctional cross‐linkers, including bis(sulfosuccinimidyl) suberate, dissuccinimidyl suberate, bis(succinimidyl) penta (ethylene glycol), bis(succinimidyl) nona (ethylene glycol), m‐maleimidobenzoyl‐N‐hydroxysulfosuccinimide ester, 2‐pyridyldithiol‐tetraoxaoctatriacontane‐N‐hydrosuccinimide and succinimidyl‐[(N‐maleimidopropionamido)‐tetracosaethyleneglycol]ester. The protein structure itself, especially the distances between target amino acid residues, was found to be a determining factor for the cross‐linking efficiency. Moreover, the reactive groups of the chemical cross‐linker also play an important role; a higher cross‐linking reaction efficiency was found for maleimides compared to 2‐pyrimidyldithiols. The reaction between maleimides and sulfhydryl groups is more favorable than that between N‐hydroxysuccinimide esters and amine groups, although cysteine residues are less abundant in proteins compared to lysine residues. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

19.
Chemical cross‐linking combined with mass spectrometry (XL‐MS) and computational modeling has evolved as an alternative method to derive protein 3D structures and to map protein interaction networks. Special focus has been laid recently on the development and application of cross‐linkers that are cleavable by collisional activation as they yield distinct signatures in tandem mass spectra. Building on our experiences with cross‐linkers containing an MS‐labile urea group, we now present the biuret‐based, CID‐MS/MS‐cleavable cross‐linker imidodicarbonyl diimidazole (IDDI) and demonstrate its applicability for protein cross‐linking studies based on the four model peptides angiotensin II, MRFA, substance P, and thymopentin.  相似文献   

20.
We present an integrated approach for investigating the topology of proteins through native mass spectrometry (MS) and cross‐linking/MS, which we applied to the full‐length wild‐type p53 tetramer. For the first time, the two techniques were combined in one workflow to obtain not only structural insight in the p53 tetramer, but also information on the cross‐linking efficiency and the impact of cross‐linker modification on the conformation of an intrinsically disordered protein (IDP). P53 cross‐linking was monitored by native MS and as such, our strategy serves as a quality control for different cross‐linking reagents. Our approach can be applied to the structural investigation of various protein systems, including IDPs and large protein assemblies, which are challenging to study by the conventional methods used for protein structure characterization.  相似文献   

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