Selected general problems in polymer processing

Sikora, R.

doi:10.14314/polimery.2000.022

Cited by 4 publications

(11 citation statements)

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“…Blowing agents used during cellular extrusion of plastics may display exothermic or endothermic decomposition characteristics [1,2,3].…”

Section: Aspects Of Cellular Extrusionmentioning

confidence: 99%

“…Examples belonging to this group include especially bicarbonates, e.g. sodium bicarbonate, ammonium bicarbonate and 2-Hydroxypropanetricarboxylic acid [3][4][5][6]. Different types of extruder heads are used in the cellular extrusion process.…”

Section: Aspects Of Cellular Extrusionmentioning

confidence: 99%

“…Basic materials for porophors with endothermic decomposition characteristics are bicarbonates and citric acid. As these substances are used as food additives, their use poses no problem [3,8,9].…”

Section: Aspects Of Cellular Extrusionmentioning

confidence: 99%

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Processing Characteristics and Properties of the Cellular Products Made by Using Special Foaming Agents

Garbacz¹,

Dulebová²

2012

Scientific Proceedings Faculty of Mechanical Engineering STU in Bratislava

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The paper describes the manufacturing process of extruded products by the cellular extrusion method, and presents specifications of the blowing agents used in the extrusion process as well as process conditions. The process of cellular extrusion of thermoplastic materials is aimed at obtaining cellular shapes and coats with reduced density, presenting no hollows on the surface of extruder product and displaying minimal contraction under concurrent maintenance of properties similar to properties of products extruded by means of the conventional method. In order to obtain cellular structure, the properties of extruded product are modified by applying suitable plastic or inserting auxiliary agents.

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“…Blowing agents used during cellular extrusion of plastics may display exothermic or endothermic decomposition characteristics [1,2,3].…”

Section: Aspects Of Cellular Extrusionmentioning

confidence: 99%

Section: Aspects Of Cellular Extrusionmentioning

confidence: 99%

See 1 more Smart Citation

Processing Characteristics and Properties of the Cellular Products Made by Using Special Foaming Agents

Garbacz¹,

Dulebová²

2012

Scientific Proceedings Faculty of Mechanical Engineering STU in Bratislava

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“…In the process of extrusion with granulation, the diameter of the pellets is a consequence of, among others, the conditions of polymer plastification in the extruder ' s plasticizing system, polymer pressure and temperature in the flow channels of the extrusion head, the dimensions of the die, the type of polymer being processed, the Barus effect, and primary and secondary processing shrinkage [1,15,16] . Pellet length is primarily related to the conditions of granulating, in particular the rotational speed of the granulator rotor and the number of cutting knives in the granulator [17,18] .…”

Section: Introductionmentioning

confidence: 99%

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

Samujło

Sikora

2013

Journal of Polymer Engineering

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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.

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“…proces wyt³aczania jest prowadzony autotermicznie) (tabela 1). Wystêpuj¹ jednak przy tym problemy z uzyskaniem odpowiedniej intensywnooeci przebiegu strumienia ciep³a generowanego w tworzywie wzd³u¿ uk³adu uplastyczniaj¹cego i g³owicy wytaczarskiej, co powoduje miejscowe przegrzewanie przetwarzanego materia³u a nawet jego degradacjê pogarszaj¹c¹ jakooeae wytworu [8][9][10][11][12][13][14][15].…”

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The influence of the conditions of blowing extrusion of polyethylene film on the changes of some its properties

Stasiek

2009

Polimery

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Streszczenie -Omówiono podstawowe zagadnienia zwi¹zane z degradacj¹ tworzywa polimerowego (w szczególnooeci polietylenu) zachodz¹c¹ w procesie wyt³aczania folii. Przedmiotem badañ w³asnych by³y ró¿ne handlowe odmiany PE-LD i PE-LLD przetwarzane z wykorzystaniem dooewiadczalnej linii technologicznej wyt³aczania z rozdmuchiwaniem. Podatnooeae tworzywa na degradacjê oceniano na podstawie zmian wartooeci wskaŸnika szybkooeci p³yniêcia (MFR), czasu indukcji utleniania (OIT) oraz przebiegu termogramów DSC. Okreoelono wp³yw wybranych elementów intensywnego mieszania lub oecinania oelimaka, a tak¿e warunków wyt³aczania (normalnych b¹dŸ ekstremalnych, w zale¿nooeci od rodzaju koñcówki mieszaj¹cej, stopnia zasypu uk³adu uplastyczniaj¹cego i wysokooeci szczeliny oecinaj¹cej) na stopieñ degradacji polietylenu powoduj¹cej zmniejszenie ciê¿aru cz¹steczkowego, a w efekcie zmianê w³aoeciwooeci mechanicznych folii, zw³aszcza pogorszenie wytrzyma³ooeci na rozci¹ganie. Okreoe³ono poziom migracji globalnej substancji z folii do p³ynów modelowych imituj¹cych ¿ywnooeae stwierdzaj¹c, ¿e wp³yw stopnia degradacji PE na poziom migracji jest nieistotny. S³owa kluczowe: wyt³aczanie z rozdmuchiwaniem, polietylen, folie, opakowania ¿ywnooeci, degradacja, w³aoeciwooeci u¿ytkowe. Summary -The fundamental problems related to polymer (especially polyethylene) degradation, going during extrusion of the film, are discussed. Various commercial PE-LD and PE-LLD grades, processed in experimental technological line of blowing extrusion (Fig. 1), were the subjects of own investigations. Polymer degradability was evaluated on the basis of melt flow rate (MFR) changes, oxidation induction time (OIT) and DSC thermograms ( Table 2). The effects of selected elements of intensive mixing or shear of a screw (Fig. 2) as well as extrusion conditions (normal or extreme ones, dependently on the type of mixing tip, shot degree of plasticizing system and shearing slot height on the degree of polyethylene degradation were determined. Degradation causes lowering of polymer molecular weight what results in changes of mechanical properties of the film especially deterioration of tensile strength (Table 3 and 4). The levels of total migration of the substances from the films to model liquids mimicking the food were determined (Table 3). It was found that the effect of PE degradation degree on migration level was insignificant.

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Selected general problems in polymer processing

Cited by 4 publications

References 0 publications

Processing Characteristics and Properties of the Cellular Products Made by Using Special Foaming Agents

Processing Characteristics and Properties of the Cellular Products Made by Using Special Foaming Agents

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

The influence of the conditions of blowing extrusion of polyethylene film on the changes of some its properties

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