Degradation studies on recycled Polyethylene terephthalate
type: CreativeWork
description: This project aims to investigate the influence of UV on the properties under natural and artificial weathering. The real-time outdoor weathering exposures provide the most accurate results but, they are very slow and manufacturers cannot afford to wait in order to see if a new or improved product formulation is really an improvement. So, accelerated testing methods are designed to simulate natural weathering with the combined action of the most weathering damaging factors; UV radiation, oxygen, temperature and water. Whatever the application, there is a concern regarding the durability of the products because if its useful lifetime can be estimated in short time, their maintenance and replacement can be planned in advance. In this study, recycled PET samples were exposed to UV outdoors and to accelerated weathering up to 13,000 hr. The mechanical behaviour (tensile and impact), thermal behaviour (DSC), molecular structure analysis (FTIR), flow characteristics (MFI) and surface properties (colour and gloss) of the samples were investigated. The whole body of the samples was substantially unaffected by degradation for long exposure time and this is confirmed by MFI and DSC results. However, the surface of the samples is affected which is seen in FTIR analysis, colour and gloss change. This explains that the photodegradation is a surface effect. FTIR analysis shows an increase in the gauche ratio and decrease in the trans ratio for both types of weathering indicating a less ordered structure after the UV radiation due to chain scission by Norrish Type I and II mechanism. Carboxylic acid is formed as a result of degradation and increases with the extent of UV exposure in both types of weathering, the formation of carboxylic acid by Norrish II is dominated over Norrish I. Colour and gloss measurement shows that the effect of degradation takes place strongly in the first 2000 hr of exposure in natural weathering and extended up to 5000 hr in accelerating weathering due to…
abstract: This project aims to investigate the influence of UV on the properties under natural and artificial weathering. The real-time outdoor weathering exposures provide the most accurate results but, they are very slow and manufacturers cannot afford to wait in order to see if a new or improved product formulation is really an improvement. So, accelerated testing methods are designed to simulate natural weathering with the combined action of the most weathering damaging factors; UV radiation, oxygen, temperature and water. Whatever the application, there is a concern regarding the durability of the products because if its useful lifetime can be estimated in short time, their maintenance and replacement can be planned in advance. In this study, recycled PET samples were exposed to UV outdoors and to accelerated weathering up to 13,000 hr. The mechanical behaviour (tensile and impact), thermal behaviour (DSC), molecular structure analysis (FTIR), flow characteristics (MFI) and surface properties (colour and gloss) of the samples were investigated. The whole body of the samples was substantially unaffected by degradation for long exposure time and this is confirmed by MFI and DSC results. However, the surface of the samples is affected which is seen in FTIR analysis, colour and gloss change. This explains that the photodegradation is a surface effect. FTIR analysis shows an increase in the gauche ratio and decrease in the trans ratio for both types of weathering indicating a less ordered structure after the UV radiation due to chain scission by Norrish Type I and II mechanism. Carboxylic acid is formed as a result of degradation and increases with the extent of UV exposure in both types of weathering, the formation of carboxylic acid by Norrish II is dominated over Norrish I. Colour and gloss measurement shows that the effect of degradation takes place strongly in the first 2000 hr of exposure in natural weathering and extended up to 5000 hr in accelerating weathering due to…
author: Al-Azzawi, Farah
keywords: 620 Engineering & allied operations
date published: 2015
date modified: 2026-07-24T02:54:20Z
provider: London Metropolitan University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: London Metropolitan University