PET recycling: a study of the solid state polymerization and increasing of barrier properties by deposition of amorphous carbon by PECVD process

• Grant number: 09/09425-9
• Support Opportunities: Regular Research Grants
• Start date: March 01, 2010
• End date: October 31, 2012
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Sandra Andrea Cruz
• Grantee: Sandra Andrea Cruz
• Host Institution: Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas (CECS). Universidade Federal do ABC (UFABC). Santo André , SP, Brazil

Abstract

The growing applications of polyethylene terephthalate - PET, mainly in the soft drink market, associated with the lack of adequate management of municipal solid waste (MSW), has caused serious environmental problems in Brazil. As the principal PET application is in blow-moulded packaging, it would be extremely useful if this material could be treated to be returned to its suitable form as its original purpose. However, the recycling cause degradation through chain scission, results in decreased polymer molar mass and, consequently, in intrinsic viscosity, which prevents bottle-to-bottle recycling. Besides, the use of the recycled material in direct contact with food is not permitted, due to the eventual processes of contaminants migration that may occur. The molar mass of recycled polymer could be obtained by post-condensation in the solid state (SSP). It is possible to use recycled material in food packaging, which is very attractive from the point of view of food safety, could be the use of a functional barrier. However, this project intends initially to study the parameters that could influence the SSP process. The parameters that will be studied are sample shape (powder, flake, pellets), molar mass, cristalinity, time and temperature of the process. The process efficiency will be evaluated by determination of carboxyl end groups, intrinsic viscosity, differential scanning calorimetry and parallel plate rheometry. Secondly, it intends to study the increase of barrier properties in recycled PET by the deposition of hydrogenated carbon thin films by PECVD (Plasma Enhanced Chemical Vapour Deposition) process. The increase in barrier properties will be evaluated by water vapour and oxygen permeation. The film thickness and deposition parameter will be changed. Chemical structure will be evaluated by infrared reflection - absorption spectroscopy. The film will be submitted to an accelerated ageing test and exposed to contact with food simulants listed by the FDA. Morphological alterations will be analyzed by microscopy electronic scattering (SEM) and structural chemical alterations will be evaluated by x-ray photoelectron spectroscopy (XPS). (AU)

Filed patent(s) as a result of this research project