Effect of grinding aids and process parameters on dry fine grinding of polytetrafluoroethylene

• DOI: 10.1016/j.powtec.2021.03.040
• Publication Date: 2021-03-19T03:11:33Z
• Authors: Rengui Weng; Jinqi Jiang; Jun Qu; Xinfei Li; Qiwu Zhang; Xinzhong Liu
• Keywords: 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 0104 chemical sciences

Abstract Ammonium salts (NH4Cl and CO(NH2)2) were used as grinding aids for crushing waste polytetrafluoroethylene (PTFE) to produce ultrafine PTFE powder (d50 = 30 μm) for the first time. PTFE was first dry-milled with the ammonium salts, after which the ground sample was washed with water to remove the soluble salts. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric differential scanning calorimetry (TG-DSC), and scanning electron microscopy (SEM) techniques were used to evaluate the mechanism of PTFE fractionation. A small part of the C–F2 bonds was transformed to -CH2- during ball-milling. Without the covering of the fluorine atoms, the PTFE molecular chain fractured at the position of the -CH2- group, thereby reducing the diameter of PTFE. The proposed ball-milling process is facile and effective for recycling waste PTFE and producing ultrafine PTFE powder with high economic value.