From waste to functional additives: thermal stabilization and toughening of PVA with lignin

Blend films of poly(vinyl alcohol) (PVA) and a graft copolymer (GL) of acrylic acid (AA) with eucalypt lignosulfonate calcium (HLS) were prepared by using a solution casting method. The structure of GL/PVA blend films was confirmed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), which indicate that GL/PVA is a homogeneous system due to the strong interactions between PVA and GL. Differential scanning calorimetry (DSC) results indicate that only one glass transition temperature (T-g) can be seen over the entire blending ratio. Meanwhile, the T-g was enhanced and the melting point (T-m) was depressed when GL was added to PVA. With the addition of 3 wt% GL, the onset decomposition temperature (T-o) was increased by 102 degrees C compared to that of PVA. Compared with pure PVA, the GL/PVA exhibited a remarkable improvement in mechanical properties: the tensile strength and Young's modulus of GL/PVA with 5 wt% GL were 39% and 285% higher than that of pure PVA, respectively. These results show that a new melt-processing method of PVA may be developed by the addition of GL in PVA.