The Influence of Enclosed Isocyanate Dosage on the Reaction Rate, Mechanical Properties and Grinding Performance of Polyurethane Grinding Wheels

Abstract

Polyurethane (PU) materials are known for their excellent elasticity and abrasion resistance, which makes them a good matrix for grinding materials. However, the fast reaction speed makes the production of large polishing wheels more difficult. In order to prolong the reaction time of polyurethanes, the reaction of phenol and polymethylene isocyanate (PAPI) was utilized in this paper to enclose the more reactive isocyanate (NCO). The enclosed NCO was then unsealed by heating, and PU materials containing differently enclosed NCO were subsequently prepared. We used various molar ratios of NCO and OH to prepare the PU materials, where a portion of the NCO content was provided by heating the enclosed NCO. The morphology and properties of the materials were investigated by a series of structural characterizations scanning electron microscopy (SEM) and (Fourier transform infrared (FTIR) spectroscopy) and hardness tests. The mechanical properties of PU materials containing different enclosed NCOs were investigated, in which 30% of the added closed NCO had good foaming stability, with a pore size of 350 μm, a reaction time of 9 min, a Shore hardness C of up to 90, and a good economic efficiency. The PU polishing wheel we prepared has a one-time grinding removal rate of more than 90% on the surface of the copper sheet, while the thickness of the copper sheet was reduced by 0.0007 mm. The addition of sealers can well extend the reaction time of PU materials, which provides engineers with a good direction for further applications of PU materials.