Degradation studies of novel degradable starch-polyethylene plastics containing oxidized polyethylene and prooxidant

Linear low-density polyethylene films were prepared that contained native corn starch (7, 14, or 28%), low or high molecular weight oxidized polyethylene (15%), and a prooxidant mixture (18% POLYCLEAN II) that contains manganese and vegetable oil. For each mixture all components were first mixed at high temperatures in a twin-screw extruder and pelletized. The pellets were cast into films using a single-screw extruder. Oxidized-polyethylene addition did not impair the transparency and thickness of the films and did not reduce the percentage elongation, whereas significant reductions in film mechanical properties were observed. Thermal and photodegradation properties of each film were evaluated by 70°C forced-air oven treatment (20 days), by high-temperature, high-humidity treatment in a steam chamber (20 days), and by exposure to ultraviolet light (365 nm; 4 weeks). Changes in the mechanical properties of the films were determined by an Instron Universal Test Machine; in the carbonyl index, Fourier transform infrared spectroscopy; and in molecular weight, by high-temperature gel-permeation chromatography (HT-GPC). The addition of oxidized polyethylene, especially high molecular weight oxidized polyethylene, and up to 14% starch to the films significantly increased the rate of thermal and photodegradation.Journal Paper No. J-15363 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 0178 and 2889.     

硝铵炸药生产中的事故防范

通过分析硝铵炸药生产中发生的火灾和爆炸事故，认为硝铵混合物在高温条件下的热分解是引发这类事故的主要原因；还给出硝酸铵热分解的要点，并提出预防恶性事故的措施。【关键词】     

THERMAL AND DISSOLVED OXYGEN CHARACTERISTICS OF A SOUTH CAROLINA COOLING RESERVOIR1

ABSTRACT: Temperature and dissolved oxygen concentrations were measured monthly from January 1971 to December 1982 at 1-m depth intervals at 13 stations in Keowee Reservoir in order to characterize spatial and temporal changes associated with operation of the Oconee Nuclear Station. The reservoir water column was i to 4°C warmer in operational than in non-operational years. The thermo-dine was at depths of 5 to 15 m before the operation of Oconee Nuclear Station, but was always below the upper level of the intake (20 m) after the station was in full operation; this suggests that pumping by the Oconee Nuclear Station had depleted all available cool hypolimnetic water to this depth. As a result summer water temperatures at depths greater than 10 m were usually 10°C higher after plant operation began than before. By fall the reservoir was nearly homothemious to a depth of 27 m, where a thermocine developed. Seasonal temperature profiles varied with distance from the plant; a cool water plume was evident in spring and a warm water plume was present in the summer, fall, and winter. A cold water plume also developed in the northern section of the reservoir due to the operation of Jocassee Pumped Storage Station. Increases in the mean water temperature of the reservoir during operational periods were correlated with the generating output of the power plant. The annual heat load to the reservoir increased by one-third after plant operations began. The alteration of the thermal stratification of the receiving water during the summer also caused the dissolved oxygen to mix to greater depths.     

水体中痕量氯苯的气相色谱分析方法研究

根据氯苯在水体中溶解度小，易吹脱且热稳定性好的特点，建立了水体中痕量氯苯的分析方法。该法采用简化的吹脱、捕集装置用ＴｅｎａｘＧＣ富集水体中氯苯，热解吸法浓缩进样，大口径毛细管柱分离，ＦＩＤ测定。方法操作简单、快速，测定水体中氯苯最低检出限为０．４μｇ／Ｌ，相对标准偏差小于８．６％。方法适宜于水体中痕量氯苯的测定     

灰色消解模型的改进——z变换后的线性回归解法

针对文献中提出的灰色消解模型的建模方法进行了ｚ变换，然后改用线性回归的办法求解，实例验证后表明，模拟拟合状况一致，但计算工作量大为减轻。     

虾塘残饵腐解对养殖环境影响的研究Ⅱ.虾塘底层残饵腐解对沉积物环境的影响

通过室内模拟实验，研究了虾塘过量残饵的分解过程、池底硫化物的生成原理、沉积物中硫化物的积累与扩散过程和还原条件下虾病发生的可能性。结果显示，在３个月的实验时间内，硫化物可渗透沉积物５ｃｍ深度。静止５ｄ即可耗尽池底溶解氧。在虾饵腐解还原环境中，异养细菌总数达２０３×１０６个／ｇ，弧菌数达６８０×１０４个／ｇ，已达到发生红腿病程度     

COD测定中加热装置的改进

采用HBA—100型标准消解器代替GB11914—89标准分析方法中的加热回流冷凝装置进行化学需氧量测定,具有精确、重现性好、操作简单等特点,能节能,减低电力负荷,提高效率。     

高精度热电离质谱定年及其对第四纪环境研究的意义

用高精度、高灵敏度不平衡铀系热电离质谱 (TIMS)法测定第四纪地质年龄 ,并已在古气候、古环境、古海洋、考古学以及近代活动火山作用的研究中取得了一系列重要成果。本文介绍了我们用MAT -2 62质谱仪对石笋、珊瑚进行测试并取得比较满意结果的情况。     

基于活化能指标的煤自燃倾向性及发火期研究

在煤的自燃及热分析动力学的基础上,结合对神东矿区3种煤样进行了热重实验,运用热重分析手段对煤从常温到燃点之间的氧化热解过程进行了研究。运用不同动力学机制模型函数分别对热重分析数据进行了处理和相关性分析,结果表明煤炭氧化热解过程符合一级化学反应动力学机制,据此求出活化能等动力学参数。对基于活化能指标的煤的自燃倾向性及自然发火期进行了初步研究。经过研究发现,该方法是科学的、客观的。     

绝热加速量热仪在化工生产热危险性评价中的应用

本文介绍了一种新型热危险性分析仪器--绝热加速量热仪的设计原理和内部结构,运行模式以及所能获得的温度、压力和最大温升速率时间等数据类型.并通过阐述其在化学动力学研究、自加速分解温度的计算、化学工艺安全性分析和化学工艺过程开发以及热爆炸事故原因调查等方面的应用,指出了绝热加速量热仪在化工生产危险评价方面的特点和优势.