Chemilumunescence of Isotactic Polypropylene Induced by UV Irradiation

Abstract

The kinetics of the weak Chemilumunescence (CL) and peroxyl radical decay after UV irradiation of isotactic polypropylene (PP) have been studied. The correlation has been found between CL and the reaction of chain termination under the PP post-oxidation at room temperature in air. Kinetics of CL decay, its compliance with kinetics of peroxyl radical decay, relative quantum yield of CL per one act of radical termination and effects of the plasticizer, accelerating both radical termination and CL decay, have been determined. Kinetic features of CL decay indicates the distributions of peroxyl radicals on both rate constants of termination and quantum yields of CL in the acts of the disproportionation of two peroxyl radicals. In terms of these distributions it is possible to describe quantitatively observed kinetics of CL decay under the post oxidation of PP after the UV irradiation in air.     

The Depth of Penetration of Radiation Oxidation in the Presence of Stabilizers

Abstract

The disposable syringes manufactured from low pressure polyethylene (LPPE) and polypropylene (PP) are widely used in the USSR. Irradiation by ionizing radiation is one of the most prospective methods of sterilizing the disposable syringes. Problems in developing the polyethylene and polypropylene formulations that remain stable under the action of sterilizing doses of radiation and subsequent prolong storing are reviewed.     

Nanosilica-Reinforced Polypropylene Composites: Microstructural Analysis and Crystallization Behavior

Polypropylene (PP) was reinforced with polystyrene-grafted nanosilica particles. A detailed study on the microstructure of untreated and treated nano-SiO₂-particle–reinforced polypropylene composites has been made by using Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The observations were correlated with the properties of the composites. Characterization of the microstructure of the nanocomposites led to a better understanding of the mechanisms of improvement in properties upon modified nanosilica reinforcement. Dispersion characteristics of the nanoparticles and the extent of agglomerate formation became clear from the AFM and TEM examinations. In order to analyze the nanomechanical properties of the composite, microscratching and nanoindentation studies were carried out using AFM. The effect of particle reinforcement on the crystallization behavior of the composites has been studied. Crystallization kinetics has been analyzed by Differential Scanning Calorimetric (DSC) measurements. The nature of nucleation and crystal growth process has been investigated by optical microscopy. The dynamic mechanical properties, microhardness, and the wear properties of the nanocomposites were examined as a function of filler content.     

Influence of the Preparation Technique on the Morphological Characterization of Polymeric Blends

Abstract

Morphology-property relationships are among the parameters which determine the practical use of polymer blends. However, very few reports in the literature realize that the preparation technique of the samples for being examined by a particular methodology, is crucial for the final results. Indeed, in the case of Electron Microscopy, for instance, for the studies of polymer and copolymer blends, very little care is taken in analyzing the effect of, for example, using dissolution for preparing samples or how a microtomy process could affect the observation. Accordingly, in this work a study of the influence of different preparation techniques for SEM (Scanning Electron Microscopy) analysis of Ethylene Vynil Acetate/Polypropylene blends (EVA/PP), including a discussion on the relevance of various physical or chemical factors affecting the observation, is presented.     

Dynamically Vulcanized EPDM/PP (40/60) Blends

Dynamically vulcanized thermoplastic elastomer (TPE) blends were first described by Fisher. In the 1960s, the usage of TPE was low. However, the consumption of TPE is increasing today. Due to hard and soft polymer phases in its structure, TPE replaced a lot of materials. TPE materials are preferred today due to their good thermal properties, oxidation resistance, transparency, adhesion, compatibility with other polymers etc. As a result of the studies that were done in 1975, TPV—vulcanized thermoplastic elastomers were developed. In this study, TPV elastomers were produced by forming crosslinks with peroxide from different ratios, of EPDM and PP. Mixing was done with twin screw extruder. After that yield and tensile strength, the modulus of elasticity, % elongation, Izod impact strength, hardness, Melt Flow Index (MFI), Vicat Softening Point, Heat Deflection Temperature (HDT), and density of crosslinks were determined. Thermal transition temperatures and microstructure were determined with DSC and SEM, respectively.     

中国办公自动化设备塑料模具行业现状与发展

阐述了中国办公自动化（Office Automation简称0A）设备塑料模具行业的现状，并对未来的发展趋势进行了分析。     

聚丙烯纤维混凝土施工技术的工程实践

通过工程实例，介绍聚丙烯纤维混凝土的施工原理。该技术对混凝土裂缝具有很好的抑制作用，能有效改善混凝土的抗裂防渗性能。     

Influence of Water on Properties of Cellulosic Fibre Reinforced Polypropylene Composites

Abstract

Flax fibers with different moisture content were used as reinforcement in polypropylene matrix with maleic anhydride grafted polypropylene coupling agent. Mechanical properties-three point bending and Izod impact strength-were investigated as a function of moisture content of the fiber, and amount of applied coupling agent.

By decreasing the moisture content of the fiber all the investigated properties can be improved. Using PPgMA as coupling agent the three point bending characteristics (flexural strength, flexural modulus, and ultimate bending stress) were better, while the impact strength decreased.     

DYNAMICALLY VULCANIZED THERMOPLASTIC ELASTOMER BLENDS OF NATURAL RUBBER AND POLYPROPYLENE

Dynamic vulcanization of a soft grade of thermoplastic natural rubber (TPNR) was carried out using several concentrations of Hexamethylene N, N′ bis (tert-butyl peroxy carbamate) (HBTP). The blends were melt mixed in a Brabender plasticorder. The effectiveness of dynamic vulcanization was investigated using the Brabender plastograms, swelling index measurements, rheological behavior by means of a capillary rheometer, dynamic mechanical properties, and tensile testing. It was found that varying the HBTP concentration had a great influence on the rheological behavior as well as the dynamic and tensile properties of the material. The increase of HBTP dosage resulted in an increase of the extent of crosslinking and caused an increase of the elastic modulus and a reduction of the loss modulus. The ultimate tensile strength and elongation at break also increased with increasing HBTP loading. The rheograms indicated that the blends exhibit a pseudoplastic behavior.     

漫射光对塑料印刷品色彩再现的影响

通过分析入射到印刷品的光在印刷品中所走过的路径的差异,来研究漫射光对塑料印刷品色彩再现的影响。运用Kubelka-Munk二能流和辐射传递理论,进一步推广描述已有光子在油墨和平行浑浊塑料介质中传输规律的辐射传输模型,从而更好地分析了半透明塑料基对印刷图像色彩再现的影响。