Key Engineering Materials Vol. 669

Abstract: The paper deals with the study physical-mechanical properties of polypropylene composites in dependence on amount of hollow glass microspheres in matrix. Composite material compounded by method "Water cooling strand pelletizing" consists of polypropylene, adhesion promoter and hollow glass microspheres with average diameter (18÷20) μm and different density: 0,46 g/cm³ (iM16K) and 0,60 g/cm³ (iM30K). Measured results are compared with talc filled polypropylene. In terms of experimental measurement is by the differential scanning calorimetry method evaluated also course of prepared composites crystallization. Finally there are concluded measured results not only regarding utility properties of parts but regarding also possibilities to control and optimize processing process.

Abstract: This work is focusing on optimization of the chosen process conditions (melt temperature, injection rate and holding pressure) and their mutual interaction on the local shrinkage of wall thickness carried out on rectangular plate. The test was applied on semicrystalline polymer in following modifications - polypropylene homopolymer and 40 % talc filled polypropylene. For better understanding of processes influencing shrinkage the pressure evolution inside cavity was captured by transducers placed near the gate and at the end of flow.

Abstract: Cooling the injection moulds with using of liquid CO₂ is rated among progressive and innovative tempering systems nowadays. In the ideal case this cooling method is chosen in combination with conventional drilled or milled tempering channels where the heat transfer medium flows. These wide-spread ways of cooling are not very often effective enough and they do not provide required accuracy of heat transfer control during production by injection moulding technology. Implementation of capillary tubes that bring the liquid CO₂ to critical zones enables local increasing of heat transfer. Regulation of liquid CO₂ amount that is injected into mould enables removal of required heat quantity in a very short time period. In this way the homogenous rate of part cooling can be achieved which is very difficult when producing the parts with complex geometry or with combination of various wall thickness. The final mechanical and physical properties of moulded parts accrue from properties of polymer material, part design and used technological parameters. This article deals with evaluation of technological parameters, concretely the cooling parameters of both the conventional cooling method and the system utilizing the cooling potential of liquid CO₂. The analysis is focused on observation of temperature field distribution on injected part surfaces.

Abstract: The waste production is increasing owing to an economical development of the society. In the area of a communal sphere they are namely PET (polyethyleneterephtalate) bottles. The research aim was to evaluate methods of compacting the drinking PET packaging. The plastic drinking packaging waste is distinguished for its dominant representation. Owing to its construction it takes up a front place in low efficiency of a storing and transporting space comparing with a material yield. The efficient compacting of the drinking packaging leads to solving a problem with often fulled up containers. The volume decreasing by means of the compacting of the packaging waste can be done in a few ways. A basic sortion is a manual pressing without the press, second way is using the mechanical presses. A low efficiency of the packaging materials is one of essential problems from the sustainable progress of human society point of view. Statistical methods were used for evaluating results and deducing conclusions. The most often used PET drinking packaging (the volume 0.5 l, 1.5 l and 2.0 l) was evaluated. The volume of the bottle before compacting and after it was set on the base of a level uplift in a calibrated laboratory tub coming from the Archimedes´s law. Experiment results showed that an effective compacting rate was reached by a manual press

Abstract: Paper deals with simulation analysis of thermoplastic flowing in plastics product. As there is a demand in plastic products, plastic industries are growing in a fastest rate. Hence plastic injection molding process begins in manufacturing of complex shapes, in this process optimum gate location is one of the important criteria in mold design. Knowledge of ideal flow properties of thermoplastic materials give us a very good starting position for design of thermoplastics products which will be made by injection molding. By simulation software Plastic Advisor was compared injection parameters for the mold with varying gate locations. Simulated thermoplastic product is made from polycarbonate and is using for the drum washing machine as console window.

Abstract: This paper deals with optimization of mechanical properties mainly hardness and stiffness of flexible part of two component injection molded part regarding production systems. Optimization is performed on two material combinations: Thermoplastic - thermoplastic elastomere and thermoplastic - silicone. Polymers used for two component part are suitable for medical applications.

Abstract: Still more and more applications using synthetic polymers find new material alternative in materials based on synthetic polymer filled with nature fibers mainly plant fibers. Not only in common applications but also in technical applications is possible to use nature fiber composites. But some additional modifications are necessary to perform to gain properties possible to use in technical applications. Mainly increasing adhesion between matrix and fibers is the most common intent of these additional operations. This paper deals with maleic anhydride based coupling agent and silane coupling agent effect in the polypropylene matrix and jute fiber composite and its mechanical properties. By using of silane coupling agents was achieved mechanical properties which are possible to compare with composites with glass fibers mechanical properties mainly in case of the flexural and tensile modulus and mainly was gained significant increasing of composite production system stability.

Abstract: To evaluate and optimize the cutting process from the effective, qualitative and economic point of view, the detailed knowledge about size, direction and orientation of cutting forces is necessary. Cutting forces are an important indicator of machining performance. It helps to understand every single action which occurs during the machining process. In this study, the influence of selected cutting parameters (cutting speed and feed rate) on the behavior of cutting force components were experimentally investigated. AlMgSi1 aluminum alloy (EN AW 6082) was milled in dry and wet machining conditions utilizing uncoated sintered carbide end mills with a different helix angle. Cutting force components were measured and statistically analyzed with using of ANOVA.

Abstract: To ensure optimal temperature conditions during casting cycle the pressure casting moulds are equipped with cooling systems. These days the cooling systems used in the most of Czech foundry plants enable pre-heating of pressure casting moulds to the working temperature before start-up of production and during casting operation to keep optimal temperature balance among the casting and the mould. Pressure casting mould temperature balance is provided by system of mutually connected channels which are mostly parallel with parting line and inside those the heat transfer medium flows. However such a system allows removal only limited heat amount from the most overheated places of the casting mould and does not allow heat removal from cores of small diameters. This inhomogeneous heat removal causes porosity of the casting in certain areas and also lifetime of the pressure casting mould is dramatically reduced. Cooling by means of liquid CO₂ was developed as one of the new cooling possibilities for such places in the pressure casting mould where the heat is concentrated and for standard cooling systems it is too complicated to fully control the heat processes there. The paper deals with the behaviour monitoring of the new cooling system utilizing the potential of liquid CO₂. This system was applied into pressure casting mould core and its final impact on the casting quality in the close surrounding was observed.