Temperature-driven surface reorganization in hot-pressed CTMP sheets revealed by ToF-SIMS and chemometrics

Artikel i vetenskaplig tidskrift, 2026

The surface chemistry of bio-based materials governs surface properties such as adhesion but can also be central to other functional properties such as dry and wet strength; however, how temperature-driven reorganization during processing occurs is not well understood. Laboratory-prepared, statically hot-pressed CTMP handsheets and industrially hot-pressed CTMP sheets were investigated to evaluate temperature-dependent surface reorganization. A comparison of ATR-FTIR and ToF-SIMS results showed that heat treatment induced chemical changes at the nanometer scale. Principal component analysis revealed systematic variation with temperature and sheet side, while orthogonal partial least squares-discriminant analysis and a shared-and-unique-structures plot isolated temperature-specific marker ions independent of front/back-side asymmetry. At 100 °C, the front-side is enriched in small carbohydrate- and lignin-derived fragments, sterols, and medium-chain fatty acid salts; at 200 °C, lignin-derived fragments and long-chain fatty acids are more abundant. Side controls show no systematic front/back-side differences, indicating a primarily temperature-driven effect. The observed temperature-dependent surface reorganization is attributed to moisture-assisted thermal softening, enhanced polymer-segment mobility, and redistribution of lignin-rich domains and extractives during hot pressing. The marker-set workflow provides an interface-sensitive approach for resolving temperature-driven surface reorganization in chemically heterogeneous lignocellulosic materials.