氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土纳米复合材料制备及其耐介质老化性能

采用原位聚合和混炼插层相结合技术制备了氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土(HNBR/PMgMA/OMT)纳米复合材料,通过XRD,SEM和TEM等测试方法研究了HNBR/PMgMA/OMT纳米复合材料的结构、形态和性能.PMgMA离子簇与未反应完全的MgMA单体形成纳米-微米共存形态结构,PMgMA对HNBR有显著的增强效果,HNBR/PMgMA/OMT纳米复合材料具有良好的加工性能、物理机械性能和耐介质老化性能.TEM结果显示MgMA/OMT并用有助于OMT剥离分散,有机蒙脱土在硫化胶中形成以剥离和插层为主、反插层和未插层共存的微观结构;SEM显示当MgMA/OMT用量为20/10份时能明显改善复合材料的界面结合,此时纳米复合材料的拉伸强度、扯断伸长率和扯断永久变形分别为30.2 MPa,520%和30%;同时具有优异的耐热空气和耐油老化性能,耐热水性能也明显改善,在165℃的热空气、水和油中长期老化14天的老化系数分别达到0.61,0.63和0.84,其耐介质老化性能明显好于炭黑增强HNBR硫化胶及HNBR/PMgMA复合材料.良好的蒙脱土片层分散结构是提高HNBR/PMgMA/OMT纳米复合材料耐介质老化性能的主要原因.     

Relaxation of glasses: The Kohlrausch exponent

Relaxation of glasses is analyzed in the framework of the generalized Vogel-Fulcher-Tamann law. In this model the relaxation times of the cooperative and individual motions (α and β) verify the relation log τ_α(T,T′) = 1/n(T,T′) log τ_β(Τ) . In the glass state the equivalent temperature T′ is the temperature of the liquid (at equilibrium) which has the volume of the glass, T′ is then the function of the aging time and of the experiment time. In the liquid state (T = T′), n(T) ~ T − T₀ is the Kohlrausch exponent (T₀ is the Vogel temperature). In the glass state the parameter, n(T,T′), is a function of the aging time and temperature, of the rheological parameters of the liquid (WLF constants C₁ and C₂) and of the expansion coefficients of the liquid and glass states. The Kohlrausch exponents deduced from the properties below Tg (volume, creep, stress relaxation) are deduced from the generalized VFT model.     

Thermal and mechanical behaviour of flexible poly(vinyl chloride) mixed with some saturated polyesters

Four saturated polyesters poly(hexamethylene adipate), poly(ethylene adipate), poly(hexamethylene terephthalate) and poly(ethylene terephthalate) were prepared. The resulting materials were characterized by IR and ¹H NMR, end group analysis and gel permeation chromatography. The effect of blending these polyesters (5 and 10%) with poly(vinyl chloride) (PVC) in the melt was investigated in terms of changes in the thermal behaviour of PVC by studying the weight loss after 50 min at 180 °C, colour changes of the blend before and after aging for one week at 90 °C, the variation in glass transition temperature and the initial decomposition temperature. The results gave proof for the stabilizing role played by the investigated polyesters against the thermal degradation of PVC. The best results are obtained when PVC is mixed with 5% aliphatic polyesters rather than with aromatic ones. This is well illustrated not only from the increase in the initial decomposition temperature (IDT), but also from the decrease of % weight loss and from the lower extent of discolouration of PVC, which is a demand for the application of the polymer. It was also found that blending PVC with 5% of the four investigated polyesters before and after aging for one week at 90 °C gave better mechanical properties even than that of the unaged PVC blank.     

纳米级金红石型二氧化钛与受阻胺光稳定剂协同改进ABS的抗老化性能研究

分别采用纳米级金红石型TiO2和受阻胺光稳定剂(HALS)对ABS进行改性,通过熔融共混法制备了ABS/纳米TiO2、ABS/纳米TiO2/HALS和ABS/HALS复合材料,采用GB/T16422.2~1999所述的塑料实验室光源暴露实验方法,用氙灯气候试验机对其进行28天人工加速老化,通过测定其老化过程中的无缺口和缺口试样冲击强度的变化来对其抗老化性能进行表征,同时利用光学显微镜和扫描电镜对其老化过程中的冲击断口形貌变化进行了研究.结果表明,纳米TiO2在ABS基体中分散良好,改性后的复合材料均具有较好的抗老化性能,纳米TiO2与HALS复合改性ABS对其耐候性的提高具有明显的协同作用,其老化后的抗冲击性能超过了单一使用HALS或纳米TiO2的改性效果,老化28天后纯ABS树脂试样的无缺口冲击强度保持率只有20%左右,添加2.0 wt%纳米TiO2后,老化28天后的ABS/纳米TiO2/HALS复合材料试样的保持率则提高到47.9%,为纯ABS树脂试样的2.5倍.     

签字笔墨迹的光老化及书写时间变化规律的研究

利用日光和紫外光对黑色签字笔字迹样本进行了光老化处理,通过区带毛细管电泳法分析了签字笔字迹墨水提取液,二极管阵列检测器记录了190～600 nm波长范围内的物质吸收峰,用电泳图中不同波长不同迁移时间的电泳峰面积之比对老化时间作图,得出了墨水中不同染料间含量的相对变化关系相对于老化时间的变化规律。同时也对自然老化的签字笔样品随书写时间的变化规律进行了研究。     

应用ResNet和CatBoost检测重放语声*

针对短语声指令声频信息少、不适用句子级重放语声检测的问题以及近距离录声后用高质量重放设备重放的语声难以检测的问题，提出了一种适用于词级重放语声检测的模型。首先，利用短时傅里叶变换、低频平均能量计算和帧排序等方法选择声频帧，然后提取这些帧的伽马通频率倒谱系数。其次，用基于自注意机制的残差网络模型进一步提取伽马通频率倒谱系数中的信息，并转化为特征向量。最后，将提取后的特征向量用CatBoost分类，从而提高检测性能。在POCO数据集上的实验结果表明，提出的方法可以以87.54%的准确率和12.53%的等错误率检测重放语声，优于基线和现有的方法。该文提出的方法在ASVspoof2019 PA数据集上的等错误率与串联检测代价函数分别为4.92%和0.1418，证明该文方法也适用于多种设置的重放语声检测。