For hydrothermal sintering, intensities of bands attributed to C-C,C-O and CH3 symmetric stretching progressively decrease with the sintering time,up to extremely low values for the sample HS80. For the cold sintering process, only a very low intensity band attributed to CH3 symmetric stretching is clearly visible.The intensity further decreases with the sintering time until quasifull disappearance for the sample CSP80.