Tomasz Garbacz

EFFECTIVENESS OF CELLULAR INJECTION MOLDING PROCESS

In a study of cellular injection, molding process uses polyvinylchloride PVC. Polymers modified with introducing blowing agents into them in the Laboratory of the Department of Technologies and Materiase of Technical University of Kosice. For technological reasons, blowing agents have a form of granules. In the experiment, the content of the blowing agent (0–2,0% by mass) fed into the processed polymer was adopted as a variable factor. In the studies presented in the article, the chemical blowing agents occurring in the granulated form with a diameter of 1.2 to 1.4 mm were used. The view of the technological line for cellular injection molding and injection mold cavity with injection moldings are shown in figure 1. The results of the determination of selected properties of injection molded parts for various polymeric materials, obtained with different content of blowing agents, are shown in Figures 4–7. Microscopic examination of cross-sectional structure of the moldings were obtained using the author’s position image analysis of porous structure. Based on analysis of photographs taken (Figures 7–9) it was found that the coating containing 1.0% of blowing agents is a clearly visible solid outer layer and uniform distribution of pores and their sizes are similar.

Quantitative Assessment of the Microscopic Structure of Extruded and Injected Low-Density Polyethylene Modified with Microspheres by Image Analysis

The paper investigates the macroscopic structure of low-density polyethylene modified with polymer microspheres. The analysis is performed on specimens produced by extrusion and injection molding with the following contents of the modifying agent: 0.25%, 0.5% and 1%. The structure of the specimens is examined in six measuring regions by image analysis. In addition, the number and diameter of produced micropores and their area fraction are determined.

The Influence of Blowing Agent Addition, Glass Fiber Filler Content and Mold Temperature on Selected Properties, Surface State and Structure of Injection Molded Parts from Polyamide 6

The effects of blowing agent and glass fiber addition and also mold temperature on selected properties of PA6 molded parts was presented in this work. Blowing agent was dosed to plastic in amounts 0.5 – 1%, and glass fiber was added in amounts 15 – 30%. Furthermore, molded parts from unfilled and unfoamed PA6 was also investigated. The experimental plan was prepared using Design of Experiments (DoE) method. The results of selected part properties: molded parts weight, thickness, hardness, impact strength, tensile strength, elongation at maximum force, and also surface state of molded parts (gloss and color) was presented. The article also presents microscopic investigations (using SEM method) of molded parts with blowing agent and glass fiber. It was found, that the glass fiber content has a larger impact on mechanical properties of parts than addition of blowing agent. The use of the blowing agent in an amount of 1% wt. will allow the reduce injection cycle time by reducing the hold pressure and hold time, without significant worsening their properties. The mold temperature has an impact especially on the gloss of molded parts and the pore size.

The Influence of Modifying HDPE on Properties of the Surface

The aim of the paper was to discover the influence of modifying HDPE with selected agents that is a blowing agent, in the course of the extrusion process, inclusive of determination how the modification affects selected physical properties and properties of the surface of HDPE extrusion product. Endothermic chemical blowing agents in the amount of 0.6 % by mass were used in the research. The article presents selected results of examination of melt flow rate (MFR) and microscopic structure.

RESEARCH ON THE INFLUENCE OF BLOWING AGENT ON SELECTED PROPERTIES OF EXTRUDED CELLULAR PRODUCTS

As a part of a more comprehensive research project, the present study was undertaken to investigate the effect of the type and content of blowing agents in the polymeric materials being processed on the structure and selected physical and mechanical properties of the obtained extrusion parts. In the experiment, the content of the blowing agent (0–2.0% by mass), fed into the processed polymer were adopted as a variable factor. In the studies presented in the article, the blowing agents of endothermic decomposition characteristics (Hydrocerol BIH 70, Hydrocerol BM 70) and the exothermic decomposition characteristics (PLC 751) occurring in the granulated form with a diameter of 1.2 to 1.8 mm were used. Based on the results of investigating porosity, porous structure image analysis as well as microscopic examination of the structure, it has been found that the favorable content of the blowing agent in the polymeric material should be of up to 0.8% by mass. With such a content of the blowing agent in the polymeric material, favorable strength properties are retained in porous parts, the pore distribution is uniform and the pores have similar sizes.

Properties and Physical Structure of Cellular PVC Coatings

The production of cellular coatings made of polymeric materials by the extrusion process differs from solid coating extrusion in that the polymer produced by the process based on the application of blowing agents has a diphase structure (gas-polymer) with small and evenly distributed gas bubbles. The research described in the paper was conducted using blowing agents with endothermic and exothermic decomposition behaviours, dosed as pellets in the range from 0.4% to 0.8% by weight relative to the weight of the polymer being processed. The extrusion process for modified PVC was conducted using the technological line for the production of electrical cable coatings. The content of the blowing agents applied in the tests in the amount of up to 0.8 wt% was selected in such a way as to produce cables with a solid coating and center coating. The appearance of the produced cable coatings, their thickness and dimensions comply with the current norms. In the investigated range of the blowing agent content, the temperature of the extrudate leaving the head decreased by approximately 7%, which can probably be attributed to the endothermic blowing agent decomposition behaviour in the extruder head. The mechanical properties of cellular products, including their hardness, are affected by the macromolecular shape, orientation and bond. A lower number of cross-linkages in the cellular polymeric material means decreased strength properties of such product. The results of the cellular coating resistance to water and oil absorption have demonstrated considerably increased absorption of the coatings produced, depending on the residence time in the aggressive environment and type of blowing agent applied. Analyzing the results of density, porosity and optical examination of the physical structure of thin-walled cellular coatings, it has been determined that the favourable content of the blowing agent in the polymer should amount to 0.6-0.8 wt%, which leads to density decrease by approximately 40%.

MODERNIZATION OF TECHNOLOGICAL LINE FOR CELLULAR EXTRUSION PROCESS

In recent years, cellular extrusion of polymers has been one of the fastest growing processing methods. It is used especially to obtain sections, bars, pipes and cellular coatings free from strains on the product surface, displaying reduced density and minimum shrinkage, at the same time maintaining similar properties of products extruded in a conventional way. In order to obtain cellular structure, product properties are modified by application of proper plastics or adding blowing agents. The article provides a description of manufacturing processes of cellular product. It gives characteristics of blowing agents used in the extrusion process and of processing conditions. Also, it discusses selected results of examined properties of the obtained cellular products. As part of the modernization of the cellular extrusion technology the extrusion head was designed and made. During the designing and modeling of the head the Auto CAD programe was used. After the prototyping the extrusion head was tested. In the article specification of cellular extrusion process of thermoplastics was presented. In the research, the endothermal chemical blowing agents in amount 1,0% by mass were used. The quantity of used blowing agent has a direct influence on density and struc ture of the extruded product of modified polymers. However, these properties have further influence on porosity, impact strength, hardness, tensile strength and another.

Influence of Polylactide Modification with Blowing Agents on Selected Mechanical Properties

The article presents research of modification of PLA with four types of blowing agents with a different decomposition characteristic. Modifications were made in both cellular extrusion and injection molding processes. The obtained results show that dosing blowing agents have the influence on mechanical properties and structure morphology. Differences in the obtained results are also visible and significant between cellular processes.

The Effect of Particulate Fillers on Hardness of Polymer Composite

The analysis of polymeric composites can be quite challenging because the samples are often of complex nature due to the presence of various groups of additives, compounding ingredients, and fillers. In this contribution, changes of hardness of Polypropylene (PP) composites during and after the exposure of materials to UV chamber and low temperatures were investigated. The particulate fillers talc and chalk in weight fraction from 10 to 50% and montmorillonite (MMT) in weight fraction 4% were used as fillers in the polypropylene matrix. The composites were mixed in the extruder while the length, diameter of screw, as well as the number of grooves in the feed zone were changed. The influence of ageing – UV radiation and low temperature was examined by change of Shore hardness after 360h and 720h of exposure. According to the performed tests we can conclude that the tested materials may be exposed to UV radiation and low temperature of -20oC without significant changes of hardness.

Calibrator device for the extrusion of cable coatings

Abstract This paper presents selected results of theoretical and experimental research works on a new calibration device (calibrators) used to produce coatings of electric cables. The aim of this study is to present design solution calibration equipment and present a new calibration machine, which is an important element of the modernized technology extrusion lines for coating cables. As a result of the extrusion process of PVC modified with blowing agents, an extrudate in the form of an electrical cable was obtained. The conditions of the extrusion process were properly selected, which made it possible to obtain a product with solid external surface and cellular core.