Characterization of Post-Consumer PET after Removal of the Original Surface: Influence of Raw Material

Abstract

Post-consumer cooking oil and soft drink PET bottles (PET_oil and PET_{soft drink}) were ground and washed only with water (conventional washing). The polymer was then chemically washed (10 min in an aqueous solution of sodium hydroxide 5 mol·L⁻¹ at 90°C) and rinsed. The materials before and after chemical washing were characterized by intrinsic viscosity, differential scanning calorimetry, thermogravimetry, elemental analysis, scanning electron microscopy with X-ray spectrum microanalysis, and gas chromatography coupled to mass spectrometry. The results indicated that conventionally washed PET_oil is the material that most differs among the four tested ones, and that the other three are more similar to each other and to what is expected for pure PET. For example, the composition of PET_oil washed only in water contained 30 volatile organic compounds, 5 nonvolatile compounds, and 7 metals, while PET_{soft drink} washed conventionally and chemically contained 5 volatile organic compounds and no metal or nonvolatile organic compounds.

Keywords:

• impurities
• oil bottles
• PET
• soft drink bottles
• washing

The authors wish to thank FAPESP (processes 04/08718-9 and 06/55213-5) and PIBIC-UNESP/CNPq for the financial support. They are also grateful to Dr. Amélia Severino Ferreira e Santos and the environmental engineering students Camila Bernadete Benassi Parra, Camila Silva Franco, Raquel Carramilo Keiroglo and Vansessa Alves Mantovani.

Notes

Where:

• I – PET_{soft drink} flakes after only conventional washing;

• II – PET_{soft drink} flakes after conventional and chemical washing and rinsing;

• III – PET_oil flakes after conventional washing;

• IV – PET_oil flakes after conventional and chemical washing and rinsing.

Where:

• I – PET_{soft drink} flakes after only conventional washing;

• II – PET_{soft drink} flakes after conventional and chemical washing and rinsing;

• III – PET_oil flakes after conventional washing;

• IV – PET_oil flakes after conventional and chemical washing and rinsing.

Where:

• I – PET_{soft drink} flakes after only conventional washing;

• II – PET_{soft drink} flakes after conventional and chemical washing and rinsing;

• III – PET_oil flakes after conventional washing;

• IV – PET_oil flakes after conventional and chemical washing and rinsing.