“Optimization of the artificial ageing performance of Polyvinyl Chloride (PVC) films containing metallic pigments”

“Optimization of the artificial ageing performance of Polyvinyl Chloride (PVC) films containing metallic pigments”: Study on the combined effect of UV radiation and water

Katris, Ioannis (TU Delft Mechanical, Maritime and Materials Engineering)

Saviello, Daniela (mentor)
Mendes, Eduardo (mentor)

Delft University of Technology

Materials Science and Engineering

2019-06-26

Metallic pigments are versatile, eye-catching and increasingly utilized materials to create unique effects in plastics. However, these pigments usually show a higher sensitivity to weathering factors like UV light and water in polymer formulations than other pigments. In the particular case of Polyvinyl Chloride (PVC), this is even more evident for pigments containing iron based compounds (the typical red and orange brilliant colors) because they can initiate a degradation processes or catalyze oxidation of the polymer or other components. Thus, an improvement of such formulations for a better long term stability of the final products is needed.The present study was carried out in the Avery Dennison R&D laboratories. It was designed in order to carry out a preliminary test to address the issue of low durability of certain colored PVC based-films containing metallic pigments. Several sensitive pigments were selected as a case study for this project. In particular, the project aims to focus on understanding the effect of water on the surface of colored PVC cast films. Water retention on the surface of the films tends to cause accelerated and localized degradation of the PVC matrix enhanced by the effect of the metal oxides.What was observed for the pigmented PVC films is that as the pigment loading increases, the weathering durability improves. The degradation spots were mostly observed on the sides of the tested films but in some cases degradation spots were observed on the surface as well. The localized degradation on the sides is attributed to the damaged flake/particles of pigments which causes the initiation and propagation of PVC degradation in combination with water retention. After the SEM analysis, the degradation on the surface can be attributed to pigment flakes/particles really close to the films surface or even protruding from it where they can easily come in contact with water.Among all five selected additives (water scavenger, dispersants 1 and 2, fluorinated MICA and anticorrosive pigment), the ones with the best overall performance were the water scavenger and the anti-corrosive pigment. The water scavenger reacts with water avoiding its involvement in the PVC degradation process. Since water is not involved, less free radicals are formed and as a result, the propagation of PVC degradation is delayed. The anti-corrosive pigment increases the overall weathering durability of the system by protecting the sensitive metallic pigments with the Zn content of the anti-corrosive pigment surface treatment conferring sacrificial cathodic protection

PVC
Pigments
Water
Films
Additives
Degradation

http://resolver.tudelft.nl/uuid:b63c5a3e-c751-4ee9-bc9f-afb27f253460

2020-06-26

Student theses

master thesis

© 2019 Ioannis Katris