Characteristics of starch-filled LLDPE plastic processed from plastic waste

In this study, rice starch-filled linear low-density polyethylene (LLDPE) was prepared by twin screw extrusion. The rice starch was blended in a virgin grade LLDPE and two kinds of recycled LLDPE using citric acid as a compatibilizer. It was found that the maximum content of rice starch blended into LLDPEs could not be more than 3?wt%. The ratios of starch to citric acid were 1?:?1 for extruded samples. The starch increased the melt flow index (MFI) of LLDPE, but tended to decrease the MFI of recycled LLDPE. Tensile strength and elongation at break of the LLDPE (common recycle grade) when blended with starch at 1?wt% were less by 8.2% and 9% than those of neat recycled LLDPE, respectively. Tensile strength and elongation at break of the deinked-recycled LLDPE when blended with starch at 1?wt% were less by 9.5% and 26% than those of neat deinked-recycled LLDPE, respectively.     

Power from plastic

Solar power is the most abundant renewable resource on our planet. In spite of this abundance, only 0.04% of the basic power used by humans comes directly from solar sources because harvesting solar energy using a photovoltaic (PV) panel costs more than burning fossil fuels. Solution-processable organic materials have recently been intensively studied for PV applications, not because they show a possibility for harvesting the sun’s power more efficiently, but because power generation from organic photovoltaic (OPV) materials will cost considerably less than other PV technologies. The cost/Watt savings comes from the possibility of using flexible substrates, using printable organic inks for the active layers, light-weight transport, low temperature and ambient pressure fabrication, and reduced materials costs. The ability to use solution processes for deposition is particularly exciting because products such as automobiles, freight containers, and building materials could be painted with photovoltaic coatings. This article gives an overview of the current state-of-the-art for OPV technology and discusses scientific issues that need to be addressed to facilitate scale-up of OPV.     

Serrated plastic flow

This paper attempts an assessment of the current understanding of the phenomenon of “serrated plastic flow”, which manifests itself as serrations, load drops, jerkiness or other discontinuities in the stress-strain curves obtained in constant extension rate tensile tests, and as sudden bursts of strain in constant loading rate tests and in constant load (stress) creep tests (the so called staircase creep). Though one can identify at least seven physical processes that can cause serrations, the discussion here is restricted mainly to serrated yielding in tension tests originating from dynamic strain ageing (dsa). The characteristics of the five types of serrations that have been identified so far and the experimental conditions under which they occur are discussed. The various models of serrated flow that have been put forward are reviewed critically. Some recent results on 316 stainless steel are presented to illustrate the effects of grain size, temperature and strain rate on serrated flow. Manifestations ofdsa other than serrations such as a negative strain rate sensitivity, positive temperature dependence for flow stress and work hardening, and the ductility minimum are also discussed. Finally the various issues to be resolved are enumerated.     

The plastic flow and finite element simulation of plastic fine blanking

An idea of fine blanking is put forward where negative clearance affects plastic shearing and the plastic state of material in the shearing zone is examined under the condition of negative clearance. By analyzing of blanking force and stress, the paper brings forward a method of setting up the three-directions pressed stress. The method determines if the material of deformation field enters the plasticity regime. Some parameters that control when the material of blanked zone enters into the plastic state are given. The analysis indicates that the material stays in the plastic regime, when the specific energy of elastic deformation for common carbon steel Q235 reaches 8.34 MPa. The status of plastic flowing in the shearing zone is simulated.     

降解塑料的开发进展

本文介绍了降解塑料的研究开发和生产现状 ,探讨了其中存在问题 ,并且对市场前景进行了分析     

Heterogeneous Mohr-Coulomb plastic material

We consider a heterogeneous medium which locally obeys a Mohr-Coulomb rigid-plastic behavior. We are interested in the macroscopic yield criterion based on an admissible stress formulation. We propose a two-dimensional analysis based on Airy potential formulation, using a first order perturbation. We first derive an upper bound for the macroscopic yield, and then construct explicitly an admissible stress field which reaches this bound. We finally show that within this framework, the macroscopic friction angle tends to the average of the local friction angle. Corrections to this value decay with the system size as [log(L)/L]^1/2, for all (narrow) distributions of local friction angle. Received: 26 June 1999     

Comparison studies on the percolation thresholds of binary mixture tablets containing excipients of plastic/brittle and plastic/plastic deformation properties

Percolation theory has been used with great interest in understanding the design and characterization of dosage forms. In this study, work has been carried out to investigate the behavior of binary mixture tablets containing excipients of similar and different deformation properties. The binary mixture tablets were prepared by direct compression using lactose, polyvinyl chloride (PVC), Eudragit RS 100, and microcrystalline cellulose (MCC). The application of percolation theory on the relationships between compactibility, P_max, or compression susceptibility (compressibility), γ, and mixture compositions reveals the presence of percolation thresholds even for mixtures of similar deformation properties. The results showed that all mixture compositions exhibited at least one discreet change in the slope, which was referred to as the percolation threshold. The PVC/Eudragit RS100 mixture compositions showed significant percolation threshold at 80% (w/w) PVC loading. Two percolation thresholds were observed from a series of binary mixtures containing similar plastic deformation materials (PVC/MCC). The percolation thresholds were determined at 20% (w/w) and 80% (w/w) PVC loading. These are areas where one of the components percolates throughout the system and the properties of the tablets are expected to experience a sudden change. Experimental results, however, showed that total disruption of the tablet physical properties at the specified percolation thresholds can be observed for PVC/lactose mixtures at 20-30% (w/w) loading while only minor changes in the tablets' strength for PVC/MCC or PVC/Eudragit RS 100 mixtures were observed.     

Load-strength simulation of plastic mouldings

The load-strength theory is used to simulate the relations between the reliability, the safety factors used in the mechanical design and the different material conditions caused by batch variations in raw material, the injection moulding process and the mould design.     

Statistical nature of plastic deformation

General physical representations on plastic deformation as a process involving the formation of dislocation ensembles (DEs) are used to determine the dependence of the plastic deformation of a local volume on the acting stress and the number of DEs. A structural model is proposed to describe the nonuniform distribution of plastic strains in local volumes. It is shown that the dispersion of the strains (the strength reduction factor) is determined by the product of the stresses averaged over the macrovolume and the plastic strain.Translated from Problemy Prochnosti, No. 4, pp. 99–108, April, 1996.