Regarding the EW-based reference sample, low and nearly constant values of torque and temperature are observed over the 10 first minutes. In contrast, formic acid addition leads to an instantaneous increase in torque (up to more than 90 N m) followed by a rapid decay, whilst temperature suddenly increases up to more than 100 C. This high value of temperature is due to the large heat flux dissipated by friction during blending of the high viscosity resulting material. However, if the reference sample processing is prolonged beyond 10 min, a powdery-like instead of a dough-like material is obtained. In the same way, acid addition did not allow a material with suitable features to be achieved.