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NIR spectroscopy in the polymer industry: The ideal tool for QC and product screening – Part 3

Jun 14, 2021

Article

This article is Part 3 of a series.

Polyethylene terephthalate (PET): A brief introduction

PET is a very common plastic, mostly encountered in our lives as PET bottles and as a food packaging material. In this article you will learn how NIR spectroscopy can improve the efficiency of your PET analysis at different steps along the production cycle. Before getting into this, let’s introduce some background information about PET.

Polyethylene terephthalate (PET)

Polyethylene terephthalate (PET) is a general-purpose thermoplastic polymer which belongs to the polyester family. Polyester resins are known for their excellent combination of properties such as mechanical, thermal, and chemical resistance as well as dimensional stability.

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Figure 1. Molecular structure of linear PET.

PET is one of the most recycled thermoplastics and has the number 1 as its recycling symbol. Recycled PET can be converted into fibers, fabrics, sheets for packaging and for manufacturing automotive parts. PET is a highly flexible, colorless, and semi-crystalline resin in its natural state. Depending upon how it is processed, it can be semi-rigid to rigid. It exhibits good resistance to impact, moisture, alcohols, and solvents.

The chemical formula of PET is (C10H8O4)n and its molecular structure is shown in Figure 1.