In the domestic production of recycled plastics, it is difficult to separate olefin polymers such as polyethylene and polypropylene. Therefore, the prerequisite for identifying the cargo-solid waste properties of recycled plastics is to determine the polymer composition. In this paper, Fourier transform infrared spectroscopy was used to detect polypropylene content in polyethylene and polypropylene blends. Under 2%-8% polypropylene content, an exponential relationship was shown in the ratio of characteristic peak area. This method features fast detection speed and accurate judgment. It can quickly determine whether the polypropylene content in the polyethylene and polypropylene blends is greater than 5% in the tariff inspection. Also, it can determine plastic solid waste attributes and identify whether polyethylene is mixed with a small amount of polypropylene content.

An analytical method for determination of polyurethane content in modified polyoxymethylene (POM) by nuclear magnetic resonance (NMR) spectroscopy was established in this paper. Specifically, the samples were dissolved in the deuterated reagent, followed by being tested by 1H-NMR spectroscopy. Next, the characteristic peaks of POM and polyurethane were integrated, and the polyurethane content in modified POM was obtained by integral area ratio. This method, featuring the advantages of a high accuracy, simple and fast operations, and no nominal samples required, has a relative standard deviation of < 2%, and its correlation coefficient with actual results was 0.9993.

The composition of imported coated fibre cloth was quickly identified by fusion sample preparation X-ray fluorescence spectrometry. Na2O, MgO, Al2O3, SiO2, P2O5, SO3, K2O, CaO, TiO2, Cr2O3, MnO, Fe2O3, NiO, CuO, ZnO, As2O3, SrO, ZrO, CdO, BaO, PbO in the matrix of the coated fibre cloth were determined. In this paper, the technology of direct melting of flake sample is studied. The method of pre-oxidation is that the sample piece is obliquely placed on the inner wall of crucible to increase the air circulation space and remove the organic matter and halide in a short time. The 66.5:33.5 mixed flux was used as the flux, and LiBr was used as the release agent. The temperature was about 1050 °C, and the time was about 17 min. The problem of melting of inorganic fibre and flux melt was found and solved. The calibration curve is constructed by silicate rock, bauxite, cement and other reference materials and high-purity reagents. The matrix effect correction adopts the variable theoretical α influence coefficient method, and B2O3 represents the unmeasured components as the elimination item. The maximum Al2O3, SiO2, CaO curves of this method are 84.4%, 91.5%, 62.6%, respectively. The Cr, Ni, Cu, As, Cd, Pb curve range of harmful elements is greater than 0.005%-0.33%; 21 curves have good linearity. R2 divided by BaO equals 0.997 and the rest are greater than 0.9993; the detection limit of harmful elements is less than 15 mg·g−1; precision relative standard deviation (n=11) principal component is less than 0.5%, and trace component is less than 15%; after comparison of standard substances and standard methods, the results are consistent. Accuracy of methods is good, and it can quickly identify the content of the main elements of the coated fibre cloth and provide a strong support for the subsequent identification of solid waste characteristic.

The content of carbon, hydrogen and nitrogen in imported recycled ABS plastics was determined by Instrumental, and the content of three monomer units (acrylonitrile, butadiene and styrene) in ABS was calculated. The influence of sample quantity and combustion time was discussed. The precision of carbon, hydrogen and nitrogen was 0.08% - 1. 32%, and the content of three monomer units was 0.08% - 1.32%. The precision of the method was 0.72% - 8.22%, and the recovery rate of the method was 90.7% - 114.8%. The precision and recovery rate of the method are good. It can quickly determine the content of each monomer unit in ABS plastics, and provide technical support for the property identification of related imported plastic solid waste.

The peroxide value of polyethylene, polypropylene and polystyrene resin was detected by titration method, Plastic particles were dissolved in a mixed solvent of chloroform and acetic acid (2:3, volume ratio), add 0.5 mL of saturated potassium iodide solution, shake for exactly 1 min then add 30 mL of water, titrated with 0.01 mol L-1 sodium thiosulphate. The detection limit of the method reaches 0.05 mmol L-1. The relative standard deviations were below 9.5 %. The method was effectively applied for the determination of peroxide value in plastic particles.