Structure and Properties of Reactive Extruded Ethylene-block-co-Polypropylene: Influence of Dicumyl Peroxide and Divinylbenzene

The reaction of an ethylene-block-co-polypropylene (co-PP) with a polyfunctional monomer—divinylbenzene (DVB)—in the presence of dicumyl peroxide (DCP) was performed in a single screw extruder. It was found that the chain structure of co-PP was significantly influenced by the DVB concentration when the DCP content was fixed. Without DVB, degradation of co-PP chains, induced by DCP, mainly occurred. But when DVB was incorporated, reactions of crosslinking and branching prevailed in the system. The crystallization temperature of the modified co-PP was enhanced and the number of spherulites was increased, accompanied with a decrease of the spherulite size, due to the branched and crosslinked structure. The essential work of the fracture (EWF) method was adopted to characterize the fracture performance of the modified co-PP. The specific essential work of fracture, w_e, first decreased gradually to a minimum, and then climbed with increasing DVB concentration, which might be attributed to the variations of the length of the DVB segment (LDS) acting as the crosslinking node and the spherulite size of co-PP. The specific, nonessential work of fracture, β w_p, of the modified co-PP was elevated to some extent with an increasing concentration of DVB. It was speculated that the crosslinked and branched structures favored stress transfer among molecular chains and spherulites, which was beneficial to the enlargement of the plastic deformation zone.     

Effect of EPDM Content on Melt Flow,Microstructures and Fracture Behavior of Dynamically Vulcanized PP/EPDM Blends

Polypropylene (PP)/Ethylene‐propylene‐diene terpolymer (EPDM) blends were dynamically vulcanized with dicumyl peroxide (DCP), using a two‐step method of even dispersion of DCP in EPDM at first and then cross‐linking at elevated temperature. The results showed that though both chain scission and cross‐linking occurred, the cross‐linking reaction predominated in this process and the number of EPDM particles was increased, accompanied with a reduction in particle size and uniform dispersion. Differential scanning calorimetry (DSC) results indicated the existence of PP/EPDM graft copolymer. The essential work of fracture (EWF) results showed that both the specific essential work of fracture (w _e ) and the specific plastic work (w _p ) increased with increasing EPDM content, the fracture toughness and plastic energy consumption (βw _p ) could be improved simultaneously and the ratio of w _e and βw _p could be controlled by adjusting EPDM and DCP content.     

Ag,Au,K吸附在W(001)表面上的功函数随外加电场的变化

基于局域密度泛函理论和第一性原理赝势法,计算了Ag,Au,K在W(001)表面上吸附时的功函数随外加电场的变化关系.从计算结果可以看到,所有吸附系统的功函数变化与外加电场强度变化之间呈线性关系.通过比较系统功函数随外加电场强度变化的斜率的不同,可以推断Ag—W(001)的键合作用与Au—W(001)键合作用之间的细致差别,表明了Au—W(001)键合作用会略强于Ag—W(001)间的键 关键词： 功函数变化 外加电场 第一性原理计算     

A relationship between effective work of adhesion and peel force for thin hyperelastic films undergoing large deformation

A method to determine the effective work of adhesion for hyperelastic thin films undergoing large deformations is presented. Starting from energy balance equation a relationship between work of adhesion, the peel force, the peel angle, and the stretch is derived. Based on this relation a procedure to compute the energy of adhesion from peel tests is proposed. To this end the peel force as well as the engineering stress vs. engineering strain diagram for thin film is required. The derived relationship shows that the non-linearity of the stress-stain relation must be taken into account in computing the effective work of adhesion from the peel force. The processing of experimental data within the standard linear elasticity approach would lead to an overestimation of effective work of adhesion. The error would increase with a decrease of the peel angle.     

实验室智能化管理的探讨

结合智能化一卡通网络管理系统在山东省计量科学研究院实验室管理中的应用情况,研讨实验室智能化管理的相关问题,重点介绍系统结构、系统特点、系统功能和系统应用。     

红外光谱法研究不同硅铝比的ZSM-5及ZSM-11分子筛的骨架振动

红外光谱法研究分子筛的骨架振动得出了在X、Y等沸石分子筛骨架上振动频率与四面体中铝含量的线性关系^[1]。但未见到有关ZSM-5型的报道.本文用红外光谱法系壳探讨了硅铝比和ZSM-5及ZSM-11的骨架振动频率之间的线性关系,并将由IR得到的SiO₂/Al₂O₃比与化学分析值进行了比较。     

无机化学实验教学中的几点尝试

针对无机化学实验教学中存在的学生实验操作不规范、理论联系实际能力不足、学习兴趣不大等问题,提出了在实验教学过程中,以强化规范实验操作、培养良好实验习惯为教学目标,同时通过实验设计、趣味化学实验、举办优秀作品展示等活动,提高学生理论联系实际的能力及对无机化学实验课程的学习兴趣。     

Determination and comparison of the essentialwork of fracture (EWF) of two polyester blends

The fracture toughness of blends of polypropylene terephthalate (PPT) with polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) were investigated. Binary blends were prepared comprising 10:90, 30:70, 50:50, 70:30 and 90:10 mass/mass%. The fracture toughness was determined for each blend using the essential work of fracture (EWF) method and thin film double edge notched tension (DENT) specimens. The specific essential work of fracture, w _e, values obtained for blends of PET/PPT ranged from 27.33 to 37.38 kJ m^–2 whilst PBT/PPT blends yielded values ranging from 41.78 to 64.23 kJ m^–2. Differential scanning calorimetry (DSC) was employed to assess whether or not crystallinity levels influence the mechanical properties evaluated. The fracture toughness of PPT deteriorated with PET incorporation. However, high we values exceeding that of pure PPT were obtained for PBT/PPT blends across the composition range studied.