辐照改性聚丙烯拉伸流变行为及其挤出发泡的研究

通过在线形聚丙烯中加入双官能团丙烯酸酯类单体,经小剂量γ射线高能辐照,制备了高熔体强度聚丙烯,研究了其拉伸流变行为及其在挤出发泡方面的应用。Rheotens拉伸流变测试表明,辐照改性后由于形成了长支化分子结构,聚丙烯的熔体强度、拉伸黏度显著提高,具有明显的应变硬化特征。实验表明,ZnO可明显降低AC发泡剂分解温度,缓和分解放热;在辐照改性制备的高熔体强度聚丙烯中加入AC／ZnO复合发泡剂,可挤出发泡得到泡孔尺寸较为均一、分布均匀、具有闭孔结构的发泡材料。     

Tocopherol oil concentration in field-grown sunflower is accounted for by oil weight per seed

Tocopherols are natural antioxidants that increase the stability of fat-containing foods and perform important biological activities. Significant variations (389 to 1873 μg g oil⁻¹) in the total tocopherol concentration of sunflower seed oil have been reported. The main objectives of this work were to determine the influence of intercepted photosynthetically active radiation on tocopherol concentration during seed filling and to establish and validate relationships between tocopherol concentration in oil and other quality variables of the seed. Seven sunflower hybrids were grown under good water and nutritional conditions in two similar experiments carried out in two contrasting environments. Treatments were applied to modify the amount of radiation intercepted per plant during seed filling in order to obtain a range in oil yield per plant and its components. Greater per plant intercepted radiation decreased the tocopherol concentration in oil. Tocopherol concentration decreased when oil weight per seed increased. Tocopherol concentration stabilized for oil weight per seed higher than 23 mg oil seed⁻¹. This exponential relationship accounted for 73% of the variability in tocopherol concentration (507 to 1203 μg g oil⁻¹) despite differences in hull type, locations, hybrids, and radiation treatments. The proposed relationship acceptably predicted independent results. Crop management techniques could lead to seeds with greater concentrations of tocopherols.     

Comparative study on the preparation and properties of radiation‐grafted polymer electrolyte membranes based on fluoropolymer films

In this study the fluoropolymers, poly(ethylene‐co‐tetrafluoroethylene) (ETFE) and poly(vinylidene fluoride) (PVDF) films, together with the radiation‐induced crosslinked polytetrafluoroethylene (cPTFE) film were compared on the basis of their preparation and properties of radiation‐grafted polymer electrolyte membranes. The polymer electrolyte membranes were prepared by radiation grafting of styrene into the base films and subsequent sulfonation. The proton conductivity and chemical stability of the three types of membranes with a similar ion exchange capacity (IEC) near 1.0 mmol/g were investigated and are discussed in detail. Although the ETFE‐based polymer electrolyte membrane was relatively more stable, its proton conductivity was lower than those of the PVDF‐ and cPTFE‐based membranes. On the other hand, the cPTFE‐based membrane showed a significantly higher proton conductivity, but its chemical stability was shorter than that of the ETFE‐based membrane. It is considered that the difference in the preparation and properties of the polymer electrolyte membranes was due to the difference in the degree of crystallinity as well as in the chemical structure of the fluoropolymer base films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1966–1972, 2007     

^60Co—γ辐照改性法制备高熔体强度聚丙烯

以多官能度丙烯酸酯类单体为辐照敏化剂，在氮气保护下，通过^60Co-γ射线的引发作用，将普通线怀聚丙烯改性成为具有长支化结构的高熔体强度聚丙烯。研究了辐照敏化剂的官能度数，用量以及辐照的剂量对凝胶含量的影响。通过辐照聚丙烯熔体流动速率和熔体强度的测定，可以得出结论；在氮气氛围中，普通聚丙烯树脂加入1．0％的两官能度辐照敏化剂，采用1kGy剂量的^60Co-γ射线进行辐照，可得到高熔体强度的聚丙烯；增塑剂和抗氧剂的加入，以及聚丙烯辐照前，后的热处理对辐照聚丙烯熔体强度的提高均有不同程度的促进作用。     

Preparation and characterization of a proton‐exchange membrane by the radiation grafting of styrene onto polytetrafluoroethylene films

Radiation‐induced simultaneous grafting of styrene onto polytetrafluoroethylene (PTFE) films and the subsequent sulfonation in the chlorosulfonic acid/dichloroethane were investigated. The effects of the main radiation grafting conditions, such as the type of solvents, irradiation dose, dose rate, the styrene concentrations, etc., on the degree of grafting (DOG) were studied. To elucidate the influence of both the grafting and sulfonation conditions on the properties of the PTFE‐g‐polystyrene‐sulfonic acid (PSSA) membranes, the sulfonation conditions, including the sulfonation temperature and the concentration of the ClSO₃H with respect to the DOG, were systematically evaluated. The grafted and sulfonated membranes were characterized by FTIR–ATR spectra, ion‐exchange capacity (IEC), water uptake, thickness measurement, etc. The as‐prepared PTFE‐g‐PSSA membranes in this work showed a good combination of a high IEC (0.85–2.75 meq g^?1), acceptable water uptake (8.86–56.9 wt %), low thickness, and volume expansion and/or contraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1415–1428, 2006     

Preparation and characterization by radiation of hydrogels of PVA and PVP containing Aloe vera

In these studies, hydrogels for wound dressing were made from a mixture of Aloe vera, poly(vinyl alcohol) (PVA) and poly(N‐vinylpyrrolidone) (PVP) by freeze‐thaw, gamma‐ray irradiation, or a two‐step process of freeze‐thaw and gamma‐ray irradiation. Physical properties, such as gelation, water absorptivity, gel strength and degree of water evaporation were examined to evaluate the applicability of these hydrogels to wound dressing. The PVA:PVP ratio was 6:4, and the dry weight of Aloe vera was in the range of 0.4‐1.2 wt %. The solid concentration of PVA/PVP/Aloe vera solution was 15 wt %. Mixtures of PVA/PVP/Aloe vera were exposed to gamma irradiation doses of 25, 35 and 50 kGy to evaluate the effect of irradiation dose on the physical properties of the hydrogels. Gel content and gel strength increased as the concentration of Aloe vera in PVA/PVP/Aloe vera decreased and as irradiation dose increased and freeze‐thaw was repeated. Swelling degree was inversely proportional to gel content and gel strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1612–1618, 2004     

基于多智能体技术的反辐射导弹作战效能评估建模研究

分析了机载反辐射导弹的作战流程;建立了基于多智能体技术的复杂电磁环境下反辐射导弹作战效能评估模型框架;研究了基于Bayesian网的反辐射导弹作战效能评估模型。提出的建模方法对其他复杂装备系统作战效能评估研究具有参考作用。     

紫外线对建筑膜材料拉伸性能的影响

采用2因子二次通用旋转组合设计,以紫外线照射时间和强度为两个因子,对建筑膜材料进行紫外线照射,测试材料的拉伸性能,分别建立了膜材断裂强力和断裂伸长率的数学模型。结果表明:紫外线对建筑膜材料的断裂强力和断裂伸长率有显著的影响;通过红外光谱分析,涂层化学结构发生了变化。     

运用AHP和云重心评价法的弹道导弹威胁评估

弹道导弹技术的发展和应用,对我国的安全环境造成了严重的威胁,合理地运用科学方法对弹道导弹威胁进行评估,可为我国的弹道导弹防御系统的发展和建设提供辅助决策的科学依据.通过确定弹道导弹威胁评估指标集,综合AHP和云重心方法的有关知识,建立各指标的云模型及其多维加权综合云的重心表示;应用云重心评价法给出威胁度的定量评估值,结合实例分析得出：该方法评估弹道导弹威胁可减少人为主观判断引起的偏差,具有可操作性.     

基于模糊灰色关联法的巡航导弹探测体系评价

为了对巡航导弹探测体系方案进行优选和客观评价,必须建立科学的评价体系和选择合理的评价方法.在分析区域巡航导弹探测体系组成与功能的基础上,提出一套巡航导弹探测的评价指标体系,利用模糊灰色关联法对3种巡航导弹探测体系方案进行仿真对比分析.结果表明评价指标体系是科学合理的.