Comparison of properties of solid and porous pvc destined for pipe construction
Zygmunt Nitkiewicz, Przemysław Chmielowiec, Henryk Stokłosa, Marian Mierzwa Politechnika Częstochowska, Instytut Inżynierii Materiałowej, al. Armii Krajowej 19, 42-200 Częstochowa
Annals 4 No. 12, 2004 pages 421-425
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abstract In the production of polymer pipes there is a tendancy to construct pipes with laminary wall structure. The porous layer between the inner and outer layers can be around 2/3 of the total thickness of the pipe wall. In this paper some comparisons of the properties of solid and porous PVC pipes, with 6.25÷6.50 wall thickness, have been shown (Tables 3 and 4). The mass density, porosity and leakproofness of both solid and porous PVC pipes have been found (Tab. 3) and presented. The fracture toughness of the tested composites was measuread by stress intensity factor KIc parameter, which was calculated in plane strain cracking conditions. The fracture thoughness measured using the parameter was 0.34 MPa ⋅ m for solid PVC and 0.57 MPa ⋅ m for porous PVC. The addition of a frothing agent caused an increase in strength from 25 MPa (solid PVC) to 37 MPa (porous PVC). Observations using scanning microscopy enabled us to describe the fracture surfaces of the tested composites. The solid PVC was characterized by brittle fracture surface as shown in Figure 2. The porous PVC was characterized by ductile fracture areas, located in the middle of the pipe thickness. It was noticed that the pore size (100÷300 μm) differs depending on its location (Figs. 3 and 4). Key words: porous PVC, mechanical properties, stress intensity factor, fractography