EBR胶乳凝胶的控制及其对ABS树脂冲击性能的影响

主要讨论了摩尔质量调节剂，延长后期反应时间，提高后期反应温度，过硫酸钾用量等对乙烯－丁二烯橡胶（EBR）胶乳凝胶的影响；同时讨论了低凝胶条件和高凝胶条件下凝胶对ABS树脂性能的影响。结果表明：低凝胶条件,ABS树脂的冲击性能随凝胶质量分数的增加而增加；高凝胶条件下，则随凝胶质量分的增加而降低，得到了EBR胶乳生产中凝胶的主要控制方法，并通过控制EBR胶乳凝胶来实现对ABS树脂冲击性能的控制。     

磷石膏的微量组分及其对水泥凝结、水化和硬化的影响

借助差热分析、热失重、X射线衍射和扫描电镜等测试手段,分析了磷石膏的微量组分,研究了磷石膏对硅酸盐水泥物理性能及水化过程和水化产物的影响,进而探讨了磷石膏对水泥单矿物的水化作用机理。     

ADHESION OF ELASTOMERS: DWELL TIME EFFECTS

The strength of adhesion of elastomers to rigid substrates generally increases with time of contact. This effect has been studied for samples of butyl and chlorobutyl rubber adhering to some rigid substrates. The peel strength increased continuously over long periods of contact until in some cases failure became cohesive within the elastomer layer. At higher temperatures the strength increased more rapidly, consistent with the WLF relation governing molecular motions. It is postulated that slow molecular rearrangements occur at the interface and increase the bond strength. A criterion for the observed transition from interfacial to cohesive failure is suggested.     

Effect of γ-irradiation on strength of concrete for nuclear-safety structures

Concrete applied for construction of nuclear power plant (NPP) Temelín (Czech Republic) has been exposed to γ-irradiation up to dose 6×10⁵ Gy. Depending on the level of irradiation, changes in strength, porous structure and phase composition of the concrete have been studied. It is found that irradiation lowers both the strength of concrete (about 10%) and volume (resp. surface) of porous space. On the other hand, γ-irradiation increases the ratio of calcite, CaCO₃, in the concrete. Observed effects are discussed with respect to safety of NPPs.     

硬沥青改性聚苯乙烯材料的研究

采用熔融共混方法，用深度萃取脱油硬沥青和尤里卡沥青两种高软化点硬沥青材料，对聚苯乙烯(PS)进行改性。力学性能测试表明，硬沥青材料的加入能使PS的冲击强度得到不同程度的提高，但拉伸强度有一定程度下降；透射电镜微观证实，硬沥青在聚苯乙烯材料内主要以约100nm的微粒分布，均匀分散的硬沥青超胶束引起的锚钉效应是聚苯乙烯材料冲击强度提高的原因，但胶束及似晶结构不能有效分散开，导致其拉伸强度等得不到提高。     

Pozzolanic properties of reject fly ash in blended cement pastes

Low-grade fly ash (reject fly ash, r-FA), a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high carbon content and large particle size. But it may be used in certain areas, such as in solidification and stabilization processes of hazardous waste and materials for road base or subbase construction, which require relatively lower strength and reactivity. It is therefore necessary to extend research on the properties of r-FA and explore its possible applications. This paper presents experimental results of a study on the mechanical and hydration properties of cementitious materials prepared by blending r-FA with ordinary Portland cement (OPC). Parallel mixes were also prepared with the good ash [i.e., classified fine fly ash (f-FA)] for comparison. Selective chemical activators were added to the mix to study the effects of the activators on the properties of the blend system. The results show that r-FA generally has a lower rate of hydration than f-FA particularly at the early stage of hydration. Adding Ca(OH)₂ alone almost had no effect on accelerating the hydration of r-FA. But adding a small quantity of Na₂SO₄ or K₂SO₄ together with Ca(OH)₂ significantly accelerated the hydration reaction. The results of the compressive strength measurement correlated nicely with the degree of hydration results. It was also found that water-to-binder ratio (w/b) was an important factor in affecting the strength development and the hydration degree of r-FA pastes.     

粉煤灰对混凝土拌合物泵送性能的影响

介绍了粉煤灰对掺有M17塑化剂的混凝土拌合物泵送性能和混凝土强度的影响，通过扫描电镜对粉煤灰颗粒形貌进行了观察，初步探讨了粉煤灰的作用机理。试验说明在接有M17塑化剂的泵送混凝土中加入粉煤灰，可增加坍落度，降低泌水率，泵逆性能可得到改善。     

Effect of retempering with superplasticizer admixtures on slump loss and compressive strength of concrete subjected to prolonged mixing

To have concrete possesses the specified engineering properties, its slump loss has to be compensated somehow at construction site so that concrete could be placed and compacted properly. Several attempts have been tried so far to render concrete workable at construction site including starting with a high initial slump at the stationary plant, or retempering with water and/or with chemical admixtures at construction site. In this investigation, ASTM C 494 Type F superplasticizer was used for retempering concrete to restore its initial slump. Concrete mixes having an initial slump of about 19 cm were prepared and subjected to prolonged mixing with different mixing duration such as 30, 60, 90, 120, and 150 min following an initial mixing of 5 min to ensure homogeneity. At the end of each mixing period, cube specimens of 15 cm were cast from concrete retempered to its initial slump level and tested at the age of 28 days for compressive strength. Results revealed that compared to the concrete retempered with water, those retempered with a superplasticizer admixture have yielded significantly higher strength regardless of the mixing duration.     

高模量聚丙烯专用料的开发

通过在聚丙烯中添加纳米蒙脱土的改性方法,开发了高模量聚丙烯专用料。着重研究了蒙脱土活化处理及加工条件等对专用料性能的影响。结果表明,在采用蒙脱石质量分数为75%的普通蒙脱土时,专用料弯曲模量提高60%以上,冲击强度提高一倍,回缩率降低35%,并且加工性能良好。     

磷石膏生产墙体材料可行性研究

通过正交试验获得磷石膏—矿渣—粉煤灰—石灰—水泥胶凝体系的优化配合比为磷石膏∶矿渣∶粉煤灰∶生石灰∶水泥=30∶25∶24.5∶10.5∶10,并通过XRD、SEM微观分析手段和宏观测定强度的方法探讨了养护制度对该胶凝体系性能的影响。研究结果表明：该胶结料90℃下蒸养7 h,然后自然养护,28 d抗压强度高达43.9MPa,凝结时间正常,耐水性良好。胶结料强度随养护温度的升高而增加;90℃下,胶结料强度随蒸养时间的增加而增加,此温度下蒸养13 h所得制品,7 d抗压强度便达到39.6 MPa。利用最优配比成型的免烧砖能达到非烧结粘土砖15级的要求。