The effects of DCS from TMP on paper and fibre surface

The effects of water recirculation in a paper mill were investigated by lab oratory-scale simulation using thermomechanical pulp and deionised water wi thout any additives. Increased water recirculation causes dissolved and col loidal substances (DCS) originating from the pulp to accumulate in water. T he objective of the study was to analyse changes in fibre and paper propert ies resulting from increasing DCS concentration. After an initial rapid cha nge, many of the measured parameters of fibres and paper were found to retu rn close to their original level to stabilise. For instance, the surface co verage of lignin in fibres. returns almost to its starting level after a co nsiderable drop at the beginning of DCS accumulation. Different methods wer e used for analysing the surfaces of fibres and paper that contain only TMP and accumulated DCS. The methods used for surface analysis were Atomic For ce Microscopy (AFM), Electron Spectroscopy for Chemical Analyses (ESCA) and Loser Induced plasma Spectrometry (LIPS). Surface energies were also measu red. The applicability of these methods was of special interest in this stu dy. AFM seems to be an excellent method for analysing surfaces that have be en covered by DCS.