The common feature of thermoplastics is the low melting point. For example, the melting point of nylon 1010 is 200-210 degrees and the melting point of polyethylene is 123-130 degrees. The difference between the ignition temperature or the decomposition temperature of the powder and the melting point temperature is small. Therefore, the flame plastic spraying must be effective in controlling the flame temperature and the degree of heating of the plastic powder. To ensure that the heated plastic particles are both in the molten state, but also lower than the ignition or decomposition temperature, or plastic powder will burn or deterioration. This is the key technology of plastic flame spraying. The solution to this problem is to add a layer of air (aerosol or air curtain) outside the oxy-acetylene flame of the gas torch based on the original gas torch. The flame directly heats the air, and then let the air heat the plastic powder. You can reach the desired spray heating temperature, complete the spraying operation.