Photo-oxidative degradation and stabilization of acrylonitrile-butadiene-styrene (ABS)

Acrylonitrile-butadiene-styrene (ABS) is a polymeric material used in many applications due to its outstanding properties and relative low cost for an engineering polymer. However, a common drawback of polymers with polydiene sequences, such as ABS, is their susceptibility to photo-oxidative degradation when exposed to ultraviolet (UV) radiation in the presence of oxygen. This work is dedicated to the study of the influence of weathering under natural and accelerated conditions on chemical structure and properties of ABS, aiming understands its degradation mechanism and enhancing its performance against UV radiation. Unstabilized and stabilized ABS samples obtained by extrusion were exposed to natural and accelerated weathering conditions. Natural exposure was carried out at Lisbon (Mediterranean climate) and accelerated weathering in a Xenotest 150S chamber. Chemical modifications of unstabilized ABS, evaluated by infrared spectroscopy with an ATR accessory, showed that under accelerated conditions the formation rate of photoproducts is higher than in natural weathering, although chain scission occurred mainly during natural exposure. During both types of weathering, optical, mechanical and rheological properties are considerable affected. Results obtained by DMA and spectrophotometry showed that titanium dioxide (TiO2) and carbon black (CB) have an important influence on photochemical stability of ABS exhibiting a protective effect against UV radiation, under accelerated conditions. The best results were achieved for ABS samples containing CB. Stabilized ABS samples with hindered amines light stabilizers and ultraviolet absorbers, primary and secondary antioxidants and a combination of both indicated that all stabilizers induced a decrease on the degradation rate of ABS during accelerated weathering experiments, although synergetic effects were achieved for samples containing physical mixtures of light and thermal stabilizers. The study of the interaction between light stabilizers, antioxidants and a combination of both with CB and TiO2 on the photostability of ABS reveled that while TiO2 efficiency is enhanced with the incorporation of light and thermal stabilizers, an antagonistic effects were found for pigmented-ABS samples with CB.

Name thesis:degree_name

Doutoramento em Ciência e Engenharia de Polímeros e Compósitos

Year dc:date.issued

2013

Author dc:creator

• Santos, Raquel Miriam Barbosa dos

Advisors dc:contributor.advisor

• Machado, A. V.
• Botelho, Gabriela
• Cramez, M. C.

Statement dc:rights

• restrictedAccess

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1822/23760

OAI record oai:identifier

http://repositorium.sdum.uminho.pt/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Arepositorium.uminho.pt%3A1822%2F23760