Application of Raman spectroscopy in plastics industry

* Introduction

Plastic products widely exist in our lives. Plastic materials used for food packaging are closely related to people's health. Therefore, the detection and classification of plastics is particularly important. According to the relevant national standards, plastic products can be divided into seven categories according to their components: polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC). Different plastics are used in different fields, but some plastics forbidden to be used in food packaging, such as PVC used in building materials, plastic bags and other fields, are often illegally used in food packaging because of its low price, which is harmful to people's health. The commonly used identification methods are thermal analysis and infrared spectroscopy, but both are destructive detection, and the analysis and testing steps are complex, time-consuming, and not suitable for the detection of a large number of actual samples.

Raman spectroscopy is a new kind of spectroscopic detection technology, which is nondestructive, fast, without sample preparation, and is not affected by the appearance. It is applied to the detection and classification of plastics, greatly improving the detection efficiency and reducing the detection cost.

* Application

Fourier transform Raman spectroscopy of several plastics

Fourier transform Raman spectroscopy is used to detect several common plastics. Compared with ordinary Raman spectroscopy, Fourier Raman spectroscopy has the advantages of avoiding fluorescence interference, high measurement accuracy and faster speed. The results are shown in the figure.

Fig.1 Fourier transform Raman spectrogram of PE         Fig.2 Fourier transform Raman spectrogram of PS

Fig. 3 Fourier transform Raman spectrogram of PP       Fig. 4  Fourier transform Raman spectrogram of PVC

Fig.5 Fourier transform Raman spectrogram of PET       Fig.6 Fourier transform Raman spectrogram of PA

Each plastic has its own unique Fourier transform Raman spectrogram, which can be identified and distinguished accordingly.

Fourier transform Raman spectroscopy (FT-Raman spectroscopy) is an intuitive, accurate and rapid method for the determination of plastics. It can be completed in a relatively short time with several hours or even longer measurement time. It does not require sample preparation and avoids possible contamination during sample preparation and preserves the integrity of the sample. Raman spectroscopy will play an increasingly important role in the field of plastics detection.

Reference:

几种塑料的傅里叶变换拉曼光谱分析，陈和生等