Janusz W. Sikora

The impact of selected granulometric properties of poly(vinyl chloride) on the effectiveness of the extrusion process

Abstract The article presents results of a study of the effect of selected granulometric features of plastified poly(vinyl chloride) granule on the basic parameters of extrusion. In the study, it was determined how mass polymer flow rate, power supplied to the extruder, power transmitted by the polymer, unit energy consumption, and energy efficiency of the extrusion process were related to pellet length and bulk pellet density. The tests were carried out using an extruder with a screw diameter of 25 mm and a length-to-diameter ratio of 25, and involved processing of pellets of different lengths at variable rotational speeds of the screw. It was established that the granulometric features of plastified poly(vinyl chloride) considered in this study, i.e., pellet length and pellet bulk density, affect the effectiveness of the extrusion process. It was shown that best effectiveness of extrusion is achieved with the use of a granule characterized by a pellet length that is close to the other characteristic dimension of granule – its pellet diameter.

Impact of Feed Opening Width and Position on PVC Extrusion Process Effectiveness

The influence of the feed opening axis width and position in relation to the plasticizing system axis on the effectiveness of the extrusion process of poly(vinyl) chloride has been studied. The research was conducted on the extrusion line for profiles with the extruder of the screw diameter 25 mm and L/D ratio = 25. In the extruder, the extruder head was mounted with a die of a rectangular cross-section shape for extruding a sheet of a defined width and thickness. The extruder was adapted for mounting five feed segments in the feed zone of the plasticizing unit; the segments differed from one another in terms of their feed opening width, the values of which were 0.6 D, 0.7 D, 0.8 D, 0.9 D and 1.0 D, respectively, whereas the values of the longitudinal axis shift of the opening relative to the longitudinal axis of the plasticizing unit were 0.2 D, 0.15 D, 0.10 D, 0.05 D and 0.0 D, respectively, which corresponded to 5 mm, 3.75 mm, 2.5 mm, 1.25 mm and 0 mm, respectively. The effectiveness of the polyvinyl chloride extrusion process was determined by dependences of extrudate temperature, extruder screw torque, polymer mass flow rate, power supplied to the extruder and conveyed by the polymer, unit energy consumption and energy efficiency of the extrusion process on the feed opening width and its axis position relative to the plasticizing unit axis, at different values of the screw rotational speed. It was stated that the width and position of the feed opening in relation to the plasticizing system axis can be adjusted in such a way that the extrusion process will be the most effective and other conclusions were also drawn.

Evaluation of Process Wear of Selected Tool Steels for Injection Molds

The aim of this contribution is to test the suitability of selected types of tool steels used for manufacturing of injection molds. Experiments were realized by the simulation of adhesive wear using laboratory equipment Amsler, which allows the testing of grinding pairs. Evaluated grinding pairs consisted of tool steel and two types of roundels. Tested polymeric materials were based on pure PA6 and PBT filled with short glass fibers, prepared by mixing process in twin screw extruder. The wear of five types of tool steels were evaluated by weight decrease before and after the experiment, while changing the friction coefficient of grinding pairs, material of grinding pairs and sensing the roughness of steel before and after wear.

Experimental Research on the Blown Film Extrusion Process of Polyethylene

Experimental studies of the blown film extrusion process presented in this paper aim at examining the influence of selected properties of constructional elements of intensive shearing and mixing on the characteristic of this process. The analysis concerned especially the influence of the thickness of the research gap between the inner surface of extruder barrel and the cylindrical surface of the intensive shearing ring placed in the screw’s metering section. Dependences of polymer mass flow rate, polymer head pressure, specific energy consumption of the extruder drive system and the component of extruder energy efficiency derived from its drive system on the frequency of screw rotation at different thickness of the research gap were presented.

Twin screw extrusion with Expancel foaming agent

Abstract Foam extrusion of polypropylene with a foaming agent, Expancel 950 MB 80 and 950 MB 120, was performed. The process was performed using a co-rotating twin screw extruder, with an 18 mm screw diameter and 24 L/D ratio. Dependences of polymer mass flow rate, extrudate foam rate, and polymer pressure on screw speed and foaming agent amount were determined and relevant conclusions were drawn.

The extrusion of plasticized poly(vinyl chloride) in an extruder with a modified feed zone. Part 1: extrusion process

Abstract The work presents the results of experimental studies of plasticized poly(vinyl chloride) (PVC) extruded by a single-screw extruder with a modified feed section. The variable factors were the feed opening width, the feed pocket depth in the extruder barrel, and the rotational speed of the screw. The following parameters were studied: extrudate temperature Tw (°C), screw torque M (Nm), polymer mass flow rate G (kg/h), unit consumption of energy supplied to the extruder Ejc (J/g), and extrusion process energy efficiency κ (%). It was found that the increase in the depth of the pocket and the decrease in the width of the feed opening influence the extrusion process in a positive way.

Analysis of the Mechanical Properties Change of PA6/MMT Nanocomposite System after Ageing

The paper deals with the influence of environmental degradation on the change of the mechanical properties of polymer nanocomposites. The tested material was polyamide (PA) filled with nanoclay fillers Cloisite 30B, Cloisite 93A and Cloisite Na + in a volume of 2, 4 and 6 wt%. Test samples were produced by injection molding and were subjected to 540 hours and 1080 hours of UV radiation. The change of mechanical properties of PA6/MMT nanocomposite systems after the ageing in the UV chamber was studied by tensile test and Charpy impact resistance test. Article also compares structure of PA6/MMT nanocomposite.

The production and properties of micro-extruded low-density polyethylene microtubes

Abstract Micro-extrusion is the process of obtaining microtubes with either simple or complex cross-sections which are used for the high-precision transport and protection of various of media. Through this process, it is possible to create tubing with interior diameters and wall thicknesses as small as 0.1 mm and 0.05 mm respectively. Micro-extruded tubing such as micro catheters and peripheral intravenous cannulas are employed in microfluidics, paediatrics and micro-analytics. This article presents the results of granulometric tests of micropellets produced by micro-extrusion with cold pelletizing and results of tensile strength tests of microrods of different diameters. The trials were performed using a standard twin-screw extruder and low-density polyethylene.

Properties of Moldings Prepared from LDPE-Pumpkin Seed Hulls Blend

In recent decades, standard polymer blends for different applications have been more and more often replaced by blends containing raw materials. The use of natural materials as filler in thermoplastics brings both economic and environmental benefits. The use of a given vegetable filler depends on the geographic location and natural occurrence of the vegetables in a given geographic region. In Poland, for instance, the pumpkin is one of such vegetables. They are used for producing oil which is pressed from pumpkin seeds. Pumpkin seeds are then collected, dried and purified to produce waste material in hull form. Particles of ground pumpkin seed hulls with varying sizes and weight-in-weight concentration ranging from 0% to 20% relative to the matrix are used as filler in low-density polyethylene. Pumpkin seed hulls are ground and sieved. Four fractions of hulls with different particle sizes are produced: <0.2 mm, 0.2-0.4 mm, 0.4-0.6 mm, 0.6-0.8 mm. The paper reports the results of investigation of the mechanical properties, i.e., strength properties determined by static tensile testing and hardness measurement, of injection molds produced at constant processing parameters. In addition, the cross sections of the obtained products are subjected to microscopic examination. Relationships are determined between tensile modulus, maximum tensile stress, tensile stress at yield, maximum tensile strain, tensile strain at yield as well as Shore hardness and weigh-in-weight concentration of the powdered natural filler and its grain sizes. Finally, relevant conclusions are drawn.

Effect of mechanical properties of metal powder-filled hybrid moulded products

Abstract The extensive research on polymer composites is motivated by the fact that it can result in obtaining new materials with enhanced properties. This research primarily focuses on investigating basic mechanical properties which determine the use of a particular composite material. This paper presents the results of tests investigating the mechanical properties, i.e. tensile strength, hardness and impact strength, of hybrid injection mouldings produced at constant processing parameters. We used five metal powder fillers: aluminium, zinc, tin, iron and copper powders, with their contents ranging from 2.5 wt% to 15 wt% relative to a polypropylene matrix composite material. The relationships were determined between different contents of the aforementioned metal powder fillers and Young’s modulus, maximum tensile stress, tensile stress at break, strains, Shore hardness and Charpy impact strength. The research also involved investigating mould shrinkage. Relevant conclusions were drawn.