Effects of Non-Aqueous Plasticizers on the Thermal Softening of Paper

The stress-strain properties of a NSSC-fluting medium plasticized with various amounts of ethylene glycol have been measured over a temperature range up to 250°C. By comparison with delignified and hemicellulose-extracted samples it is concluded that the major softening is to a large extent caused by the lignin. It is shown that the Kaelble equation provides a good estimate of the glass transition temperature in lignin plasticizer systems. A reasonable correlation is also found between the measured softening in NSSC-papers containing ethylene glycol and the predictions of the plasticizing effect on lignin and carbohydrates based on the Kaelble approach. On this basis, the thermal softening of a NSSC-fluting medium and its lignin and carbohydrate polymers when plasticized by water is discussed, particularly in relation to the hot corrugating process.