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- Title
Establishing long-term behaviour of underground pressureless polyolefin materials.
- Authors
de Palo, R.; Pradella, F.; Burgin, E.; Ferrari, E.
- Abstract
This paper addresses the difficult problem of predicting service life in pressureless underground plastics pipes applications. Lifetime in such applications is generally determined by thermooxidative behaviour, which is governed principally by the type and amount of two classes of stabiliser: primary antioxidants and thio-synergistics. Ageing studies in water at 95°C have indicated that, for polypropylene (PP), mechanical performance is not influenced by exposure for up to six months (longer term trials are in progress). Despite this, aging in water can have a significant effect on the thermoxidative life of PP, by extracting antioxidant additives. As in pressurised pipe applications, determination of the combined effects of oxygen and water extraction is key to useful predictions of durability. In an attempt to improve life assessment, polypropylene plaques have been aged in contact with water at 95°C to determine the fitting parameters for Fickian diffusion. The residual stabiliser was measured directly by high-performance liquid chromatography (HPLC) and indirectly, using oven aging. Parameters have been determined for three phenolic primary antioxidants widely used in polyolefin pipes. Direct analysis by HPLC was found to give much lower scatter and hence is proposed as the more reliable method. A methodology is proposed to predict the lifetime of polyolefin pipe materials for underground sewerage applications avoiding the need to make tests on pipes.
- Subjects
POLYOLEFINS; POLYMERS; PLASTIC pipe; POLYPROPYLENE; ANTIOXIDANTS; HIGH performance liquid chromatography
- Publication
Plastics, Rubber & Composites, 2005, Vol 34, Issue 7, p334
- ISSN
1465-8011
- Publication type
Article
- DOI
10.1179/174328905X59818