Browse Articles

The concept of thermal homogeneisation efficiency, hht was defined, giving an indication on the thermal homogeneity realised by a certain zone through the heat generated by internal friction. Its optimal value corresponds hht = 1. This concept was then applied to the calculus of thermal homogeneity at the flow of a power-law non-Newtonian polymer melt, through a rectangular slit, similar to the flow over the barrier flight f. The relationships obtained for temperature rise due to heat generated through internal friction allowed the calculus of hht in a given case. Kewords: thermal homogeneity, internal friction, polymer melt

This work presents the results obtained from experiments of rigid PVC stabilization both lead stabilizer and earth alkaline carbonates as co stabilizer. Efficiency of stabilizers was tested by dynamic tests (roll mill processing or Brabender plastograph) and static test (thermogravimetric analysis). Both types of test were in concordance from point of view of stabilization efficiency and from thermal analysis can be predicted the thermal lifetime of PVC products. This is an important fact for durable usage or for recycling products made from PVC. Keywords: PVC stabilizers, roll mill, Brabender plastograph, thermal analysis, lifetime prediction, isoconversional method

In this paper it was established the influence of the processing temperature of the injection moulding on the in-mould pressures and on the characteristics of the obtained items used for high performance sport products. The processed polymers were: polypropylene (PP), polyamide 6,6(PA66), polycarbonate (PC), polyurethane (PU), polyoxymethylene (POM, polyacetal). The injection machine employed was ENGEL G/11/10/116/3 produced in 2002. For the correct temperature measurement in the injection cylinder nozzle a DYNISCO Ti422J thermocouple was used and for the determination of the cavity temperature, a thermocouple 2024T model, produced by Digitron Instrumentation Ltd. was used. The mould cavity pressure was measured with a transducer model IDA, produced by Dynisco Europe GmbH. Keywords: injection moulding, pressure, temperature

The paper argues the necessity of 3-dimensional inspection of injected plastic parts, presenting the special demands and particular condition related to the specificity of part material nature. A measuring strategy on the coordinate measuring machine is presented for verifying the position, dimensional accuracy and shape of the circular holes, slots and the line form for plastic parts used in the automotive industry due to the dimensional changes caused by shrinkage and warpage. The reverse-engineering technique applied in the try-out phase to the production launch is also presented. Keywords: injection, shrinkage, warpage,3-D measurement, reverse engineering

Highly active, new bis(2,6-di- tert-butyl-4-methyl-phenoxy)aluminum methylphosphonate sterically hindered aluminum catalyst was developed for both, homo- and copolymerization of propylene oxide with carbon dioxide. The behaviour of this catalyst compared with that of bis(2,6-di-tert-butyl-4-methylphenoxy)aluminum alcoxide-based catalyst was investigated. The former shows much higher catalytic activity in chemical fixation of carbon dioxide than the latter. According to the experimental data, the unavoidable propylene carbonate resulting in an appreciable proportion in propylene oxide - carbon dioxide copolymerization reaction initiated by sterically hindered aluminum catalysts, seems to appear not at the back-biting reaction of the growing chain. Apparently the reaction temperature or the reaction components molar ratio did not influence the propylene carbonate proportion. Keywords: propylene oxide, carbon dioxide, aluminium catalysts

The paper presents the results of experiments in obtaining some plastic mixtures with high quality characteristics, which should lead to products of complex geometry and improved chemico-structural features, meant to be used in the processing industry-helical milling machining by applying the formation technology in a plastic state. The paper presents the physico-chemical, mechanical and structural features of the mixtures of hard K20 alloys, the compositional networks of the powder making system and of the multi-component organic binder, all these being accomplished according to ICEM’s technical view. To improve the toughness, the tenacity and the wear resistance of the parts devoted to metal working industry, the helical mills were coated with some extra-hard layers by TiC, TiN/Ti2N deposits on hard alloy support by a new PVD technique which supposes a combined magnetron sputtering and ion implantation (CMSII). Keywords: plastic mixtures; helical mills; extra hard layers; magnetron sputtering; ion implantation

In this paper the mechanical models for nanocomposites are discussed focussing on the main restrictions of the first order models. It is proposed, according to some results for the second order models, to include in the mechanical approach some geometrical parameters to handle the transition from to scale to scale, but also to refer the modelling to an expedient class of functions which naturally describe the scale transition. Keywords: nanocomposites, first order models, second order models, wave propagation, wavelets

Ultra-high molecular weight polyethylene generally cannot be processed by injection moulding because of its high viscosity. In this paper, the formability of GUR-UHMW-polyethylene is numerically investigated during the injection moulding in an acetabulat cup. A number of numerical simulation tests have been performed on different acetabular cups to select the most appropriate process parameters and to optimize the injection moulding process. The numerical analysis demonstrates that the GUR-UHMW- polyethylene can be processed by injection moulding. Keywords: injection moulding, finite element analysis, UHMW-PE

Composite materials fatigue is a process which causes early failure or damage of variable loading subjected structure. Prediction of life period of composite materials uses different deterioration models. Quantifying of interlaminar stress and delamination can be underlined on load capacity of stratified composite materials subjected to fatigue. Keywords: composite materials, fatigue, interlaminar stress, delamination, load capacity

In this paper the static traction behavior of two types of talcum polyethylene, having the same friction coefficient but different modulus of elasticity and different tensile strengths, individually used and assembled with bolt, is studied. The behavior evaluation is done on the force-displacement curves and on the mechanical characteristics basis, specific to the materials (tensile strength, elongation, Young modulus), emphasizing the tension concentrator effect. Keywords: polymers, static loading, assemblies, mechanical characteristics