DSC测试环氧胶玻璃化转变温度的影响因素

采用差示扫描量热法测试了环氧胶样品的玻璃化转变温度。结果表明:样品的Tg值随着样品的厚度、形状、养护时间等的不同而变化,不同条件下测试的Tg值不具有可比性,因此,在说明某种材料的Tg值时,应详细注明测试条件。     

PPO/EP复合材料的玻璃化转变温度及其测试方法

介绍了玻璃化转变温度(Tg)的内涵及其主要测试方法;以聚苯醚/环氧树脂(PPO/EP)为研究对象,分别采用DSC法和DMA法测定其Tg值,并讨论了两种测试方法的异同。结果表明:两种测试方法的测试条件、测试精度及影响测试结果的因素是不同的。在给出某一种高聚物的Tg时须注明测试方法和条件。     

用差示扫描量热法测定橡胶填充油的玻璃化转变温度

采用差示扫描量热法(DSC)测定了不同组成的橡胶填充油的玻璃化转变温度(Tg),考察了操作条件对Tg的影响,并分析了测试方法的精密度和重复性.结果表明,试样用量和升温速率对测试结果均影响不大,综合考虑试样用量宜为5～20 mg,升温速率为20℃/min;DSC测试具有良好的精密度和重复性.     

锦纶工业长丝的测试方法比较分析

应用BISFA法、JIS法、ASTM法及用户法4种测试方法,对锦纶工业长丝的常规物理性能指标——纤度、断裂强力、定负荷伸长率、断裂伸长率进行了测试。分析了4种测试方法对同一样品测试结果的差异性。结果表明:由于测试条件不同,使用不同的测试方法,测试结果差异较大;4种方法测试数据之间的差值恒定,可以采用修正系数修正测试结果。     

高含量粉体填充复合材料的流动性测试方法

采用落杆法,使用熔融指数测试仪和毛细管流变仪测试了一种高含量粉体填充树脂基复合材料在不同温度下的流动性,并对测试结果进行了分析比较.结果表明,3种测试方法均可用于该类材料的流动性测试;落杆法具有操作简单和可测试材料范围广的优势.     

纳米二氧化钛的制备及光催化性能的研究

实验采用了熔融分相法制备纳米TiO2光催化材料，本文研究了该制备方法的实验原理，采用DTA，XRD，SEM，TEM等测试手段对实验结果进行分析，并对不同条件下热处理样品的TiO2晶体的析晶情况进行讨论，用甲基橙作为模拟降解物进行光催化性能的测试。实验结果表明：采用熔融分相法可以制备出晶体粒径在纳米尺寸的与多孔玻璃负载牢固的TiO2光催化材料。光催化性能结果显示了对于不同条件热处理的样品，只有在多孔玻璃载体孔径及TiO2晶粒尺寸大小适宜时，其光催化效果才能达到最佳。     

不同有机硅聚合物的粘弹性能分析

利用综合流变仪表征了三种有机硅聚合物样品在不同测试频率、振幅及温度下的动态粘弹性能。结果表明,通用硅橡胶样品与低苯基硅橡胶样品在高频条件下的弹性性能均优于苯基硅油样品,且均为非交联结构,随着频率的增大,三种样品的储能模量G'与损耗模量G″均增大;在振幅测试条件下,低苯基样品的损耗因子tanδ略微低于通用硅橡胶样品,但储能模量G'大于通用硅橡胶样品,回弹性更好,更适合做减震材料;温度测试条件下,得到三种样品的玻璃化转变温度Tg,其中低苯基硅橡胶样品的耐高、低温性较好。     

轮胎侧向松弛长度测试方法的研究

针对不同规格的轿车子午线轮胎,研究不同测试条件下侧向刚度法和侧偏角阶跃法的侧向松弛长度测试结果。结果表明：侧向刚度法和侧偏角阶跃法得到的侧向松弛长度存在一定差异;小规格205/55R16轮胎在不同充气压力和负荷下的侧向松弛长度基本都小于较大规格225/50ZR17轮胎;两种测试方法得到的侧向松弛长度随充气压力和负荷的变化趋势具有一致性,但不同规格轮胎侧向松弛长度随测试条件的变化趋势有所差异。     

高分子网络凝胶法制备纳米ZnO的结构性能研究

采用高分子网络凝胶法制备了ZnO粉末样品。通过X射线衍射、扫描电镜等测试方法研究了样品的物相组成、微观形貌。X射线衍射测试结果显示,样品的衍射峰尖锐,各特征峰显示完整,与标准PDF卡片比对,证实粉末样品的物相为ZnO。使用Scherrer公式计算得到的晶粒度大小约为31.28nm,晶格常数分别为3.247和5.208。使用扫描电镜观测不同放大倍数下的样品形貌,发现晶粒外观形貌显现完整,晶粒尺寸大小与XRD测试结果相吻合。结果表明,实验成功制备了高质量的ZnO纳米多晶粉体,可以用于后续实验。     

导热系数测试方法的综述

本文介绍了导热系数的五种测试方法,描述各种方法的测试原理及其计算方法。材料导热系数测试方法各有其特点,在选择时。应该充分考虑测试材料的性质、导热系数范围、测试温度等。     

测试方法对聚合物玻璃化温度的影响

选取环氧树脂固化物为样品,分别采用DSC法和DMA法测定了其玻璃化转变温度。结果表明,玻璃化转变温度随测定方法和条件的不同而变化,因此,在给出某种材料的玻璃化转变温度时,必须注明测定方法和条件。     

非晶态粉体玻璃化转变温度的测量方法与装置

为了研究非晶态高分子粉体玻璃化转变与结块特性,需要建立一种实用有效的玻璃化转变温度的测定方法。基于非晶态高分子粉体的体膨胀系数在玻璃化转变时发生突变的原理,采用热膨胀计技术,提出了一种用膨胀计测量非晶态高分子粉体玻璃化转变温度的新方法——膨胀计法,并建立了相应的测量装置。以聚苯乙烯为例,详细介绍了用该方法进行测量及数据处理的过程,并考察了测量结果的有效性。以谷物及含水淀粉体为例,考察了该方法在食品粉体玻璃化转变温度测量中的应用。结果表明,膨胀计法测量非晶态高分子粉体玻璃化转变温度,实用、有效,为非晶态高分子粉体的玻璃化转变温度测量提供了一种新途径。     

Problems of compatibility of the values of glass transition temperatures published in the world literature

The influence of different factors (primarily, the temperature-time conditions for preparation and measurement of samples) on the glass transition temperatures determined from the temperature dependences of properties is analyzed using the calculations performed in terms of the relaxation theory of glass transition. The most optimum conditions for measurement of the glass transition temperatures T _g that ensure the compatibility of the values of T _g obtained by different researchers are recommended. The validity of the assertion that the glass transition temperature T _g is a temperature at which the viscosity of glasses is equal to 10¹³ P is considered.     

玻璃化相变及其对食品干燥贮藏影响的研究进展

在玻璃化转变的相关基础理论上,综述了影响玻璃化转变温度的主要因素,指出了玻璃化转变温度作为建立在动力控制过程的非平衡态基础上的物理化学参数,与水分含量和水分活度两重要指标相结合,可以用来解释玻璃化相变对干燥贮藏过程的影响,并对玻璃化相变温度的测定方法进行了总结评价。     

Glass transition temperature in nylons

The determination of the glass transition temperature of semi-crystalline polymers is a controversial problem in the literature, because of the complexity of the phenomenon and of the different methods used for its measurement. In this work the glass transition temperatures of five commercial nylons (nylon-6, nylon-6,6, nylon-6,10, nylon-11, nylon-12) have been measured by both thermal and mechanical methods. The behaviour observed during thermal measurements is analogous to that observed by Gordon, who found that the transition detected in the heating cycle disappeared in the subsequent cooling cycle and appeared again only after a sufficient rest period of the samples, and at a temperature different from the initially measured one. He attributed this behaviour to the structure of the amorphous regions of the material, where the hydrogen bonding groups form an irregular network. The delay in reforming the above mentioned network is the main cause of the dependency of the observed transition on the thermal history imposed on the samples. Mechanical measurements give results that are quite insensitive to the thermal treatment of the materials, and thus provide very reproducible values of the transition. This feature allows the possibility of attributing to the transition obtained the character of a true glass transition where the main cause of the phenomenon is the increased mobility of the chain backbone in the amorphous regions of the materials with increasing temperature. This character was also confirmed by dilatometry, with results in agreement with Boyer's criteria for a true glass transition temperature.     

COMPARISON OF GLASS TRANSITION TEMPERATURE AND STICKY POINT TEMPERATURE FOR SKIM MILK POWDER

Wall deposition of particles in spray dryers is a key processing problem, and information about the glass transition temperature of the amorphous material that arises from spray drying can be used to guide the selection of operating conditions that may minimise wall deposition. The glass transition temperatures for skim milk powder with various moisture contents were determined using Differential Scanning Calorimetry (DSC), and a repeatable glass transition temperature diagram was established from these results. The glass transition temperature decreased as the moisture content increased, as expected (low moisture content 1.65 g/100 g of dry powder, glass transition temperature 87.7°C; high moisture content 4.52 g/100 g of dry powder, glass transition temperature 46.7°C). The glass transition temperature was found to be virtually the same as the sticky-point temperature measured using a thermo-mechanical test. The difference is essentially due to the difference between doing a mechanical test for viscosity (sticky-point) and a phase transition measurement (DSC).     

Effect of drying conditions on the glass transition of poly(acrylic acid)

Systematic changes of drying conditions of poly(acrylic acid) were tested to study their effect on the glass transition of the material. The materials were synthesized in two different mediums of water and benzene, respectively. The glass transition temperatures of the samples were determined by thermal analysis using DSC. The samples were also characterized by IR spectra. The glass transition of poly(acrylic acid) was found to be significantly dependent on the drying conditions and also dependent on the medium in which poly(acrylic acid) was prepared. The anhydride formation in poly(acrylic acid) was increased as the drying temperature was raised, resulting in the increase of the glass transition temperature. The “bound” water involved in the preparation of poly(acrylic acid) in water medium could affect significantly the glass transition of the sample. A significant discrepancy in the previously reported values of the glass transition temperature of poly(acrylic acid) seems to be due to the differences in the drying conditions of the materials.     

环氧树脂与氰酸酯共固化反应的研究Ⅱ.固化反应动力学参数及固化物性能

用DSC，介电和动态力学等分析方法研究了组成对乙酰丙酮过渡金属络合物催化促进的环氧树脂与氰酸酯共固化反应体系反应动力学参数，固化产物力学，电气和耐热性能以及玻璃化转变温度的影响。结果表明，随着共固化反应体系中氰酸酯含量的增加，其表观反应活化能和频率熵因子均随之升高；在相同的固化条件下，共固化产物中三嗪环结构含量增加，聚醚结构减少，玻璃化转变温度升高，耐热性能，介电性能提高。     

含噁唑结构固化剂的分子动力学模拟研究

首先利用分子模拟技术建立了缩水甘油醚双酚A环氧树脂/二胺基苯并噁唑(E/ABO)固化环氧树脂体系的简单分子模型,并利用这些模型在计算机上对树脂体系的玻璃化转变温度进行研究,同时利用实验进行验证.结果表明,利用分子模拟技术可以很好地预测环氧树脂固化体系的玻璃化转变温度;同时新开发的E/ABO环氧树脂固化体系的玻璃化转变温...