The invention provides a method and a device for identifying common plastics. The method comprises the following steps: measuring the mid-
infrared spectrum of a sample to be identified by utilizing ATR-FTIR; the characteristic
wave band of the mid-
infrared spectrum is intercepted, the characteristic
wave band is decomposed step by step through
wavelet transformation, fine-scale and large-scale information in the characteristic
wave band is separated into a
wavelet detail coefficient and an approximation coefficient after
wavelet transformation, the approximation coefficient comprises low-frequency components of signals, and the low-frequency components of the signals are converted into low-frequency components of the signals; the detail coefficient comprises the high-frequency change of the
signal, and each level of
decomposition can further refine the characteristics of the
signal; selecting a middle layer of the multi-layer wavelet detail coefficient set obtained after step-by-step
decomposition to carry out two-dimensional reconstruction to obtain a two-dimensional
data matrix; and inputting the two-dimensional
data matrix into a pre-established CNN2D model to obtain the plastic category of the sample to be identified. According to the invention, common plastic types can be quickly identified, secondary
pollution is avoided, the efficiency is high, the speed is high, the identification accuracy rate is high, and the classification accuracy rate is high.