Polypropylene/poly(butyl methacrylate) blends prepared by diffusion and subsequent polymerization of butyl methacrylate in isotactic polypropylene pellets

Polypropylene/poly(butyl methacrylate)(PP/PBMA) blends were prepared by diffusion and subsequent polymerization of butyl methacrylate(BMA) in commercial isotactic polypropylene(iPP) pellets.The diffusion kinetics,diametrical distribution of PBMA in a pellet and phase morphology of a typical PP/PBMA blend were investigated.     

Numerical simulation for the temperature changing rule of the crude oil in a storage tank based on the wavelet finite element method

In order to study the temperature changing rule of the crude oil in the storage tank, the wavelet finite element method, the traditional finite element method and the test were used to carry out the numerical simulation. Firstly, the thermal wavelet finite element was put forward established based on thermal finite element theory and the wavelet theory. And the computational model and three boundary conditions were established. And then the temperature changing rule of the crude oil in the storage tank in 24 h for three boundary conditions was obtained by using three methods, and the results showed that the wavelet finite element method had advantages in the numerical analysis of the temperature changing rule of the crude oil in the storage. And then the temperature distribution rule of the crude oil in the storage tank under different conditions in 5 h was obtained. And the temperature changing mechanism of the crude oil was summarized finally.     

UPLC-ELSD Determination of 1-Octacosanol in Raw Material and Health Products

Determination of the levels of 1-octacosanol is important in food stuff for the study of its pharmacological activities and health benefits. In this study, a novel, simple and fast internal standard method for the non-derivatization ultra-performance liquid chromatographic determination of 1-octacosanol in raw materials and health products was developed and validated based on evaporative light scattering detection. The linearity (r ² > 0.998), recovery (99.1–100.2%, RSD <2.7%), intra- and inter-day precision (RSD <3.8%), limit of detection (1.0 mg/L), limit of quantification (2.2 mg/L) of the 1-octacosanol were determined. The method was successfully applied to nine real 1-octacosanol products. The results of analyses had close agreement with the labeled claims of 1-octacosanol content in these products. Compared with the classical gas chromatography method, the developed method was simpler, faster and more environmentally friendly due to avoiding any derivatization step. This protocol represents a rapid and feasible method for quality control of 1-octacosanol products.

     

Flexural contact in MEMS stiction

Adhesive force between two solid surfaces can lead to stiction failure of the micro-electro-mechanical systems (MEMS) device. The competition between the adhesive force and the beam restoring force determines whether the stiction occurs or not. Previous models assume that the stuck beam deforms either as the arc-shape or the S-shape, which causes significant differences in the measurements of adhesion and disputations among researchers. The contact mechanics model presented in this paper shows that the assumptions of the arc-shape and S-shape on the beam deformation over-simplify the problem; both the arc-shaped deformation and S-shaped deformation significantly deviate from the real ones. The previous theories are shown to be incompatible with the recent experimental results. The model presented in this paper attempts to explain those new experimental results and resolve some disputations on the previous models. The instabilities of jump-in during loading process and jump-off during unloading process are also incorporated in this model.     

Discontinuous crack-bridging model for fracture toughness analysis of nacre

Studying the structure–property relation of biological materials can not only provide insight into the physical mechanisms underlying their superior properties and functions but also benefit the design and fabrication of advanced biomimetic materials. In this paper, we present a microstructure-based fracture mechanics model to investigate the toughening effect due to the crack-bridging mechanism of platelets. Our theoretical analysis demonstrates the crucial contribution of this mechanism to the high toughness of nacre. It is found that the fracture toughness of nacre exhibits distinct dependence on the sizes of platelets, and the optimized ranges for the thickness and length of platelets required to achieve higher fracture toughness are given. In addition, the effects of such factors as the mechanical properties of the organic phase (or interfaces), the effective elastic modulus of nacre, and the stacking pattern of platelets are also examined. Finally, some guidelines for the biomimetic design of novel materials are proposed based on our theoretical analysis.     

Efficient Imine Formation by Oxidative Coupling at Low Temperature Catalyzed by High-Surface-Area Mesoporous CeO2 with Exceptional Redox Property

High-surface-area mesoporous CeO₂ (hsmCeO₂) was prepared by a facile organic-template-induced homogeneous precipitation process and showed excellent catalytic activity in imine synthesis in the absence of base from primary alcohols and amines in air atmosphere at low temperature. For comparison, ordinary CeO₂ and hsmCeO₂ after different thermal treatments were also investigated. XRD, N₂ physisorption, UV-Raman, H₂ temperature-programmed reduction, O₂ temperature-programmed desorption, EPR spectroscopy, and X-ray photoelectron spectroscopy were used to unravel the structural and redox properties. The hsmCeO₂ calcined at 400 °C shows the highest specific surface area (158 m² g⁻¹), the highest fraction of surface coordinatively unsaturated Ce³⁺ ions (18.2 %), and the highest concentration of reactive oxygen vacancies (2.4×10¹⁵ spins g⁻¹). In the model reaction of oxidative coupling of benzyl alcohol and aniline, such an exceptional redox property of the hsmCeO₂ catalyst can boost benzylideneaniline formation (2.75 and 5.55 mmol h⁻¹ based on >99 % yield at 60 and 80 °C, respectively) in air with no base additives. It can also work effectively at a temperature of 30 °C and in gram-scale synthesis. These are among the best results for all benchmark ceria catalysts in the literature. Moreover, the hsmCeO₂ catalyst shows a wide scope towards primary alcohols and amines with good to excellent yield of imines. The influence of reaction parameters, the reusability of the catalyst, and the reaction mechanism were investigated.