Preparation And Characterization Of The Degradable Composites Of Lignin And PCL

With the depletion of fossil fuels and the increase of white pollution, more and more attention has been attracted into biodegradable, renewable and eco-friendly materials. Lignin which is a biodegradable, non-toxic and renewable aromatic polymer is the second most abundant natural macromolecules after cellulose. It widely exists in woody tissues of plants, and is largely separated from plants in pulping and papering industries and bio-ethanol production industries. However, only a few of it utilized properly. Therefore, making full advantages of lignin is of great economic importance. Given its rigid molecular structure with amounts of benzene rings and hydroxyl groups, blending with flexible macromolecules can be a good way out. Poly(ε-caprolactone) (PCL) is a linear synthetic polyester, which makes the chains flexible and biodegradable. Therefore, the lignosulfonate (LS) with great output in industries was melt blended with PCL and the performances of the blends were also investigated to pave a way for the use of lignin and prepare materials with biodegradable properties.The blends of LS and PCL were studied by attenuated total reflectance infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC) and so on, and the results showed that there are interactions between LS and PCL, which has a great influence on the performances of the LS/PCL composites. The agglomeration and prolapse of lignosulfonate particles were obvious as shown in scanning electron micrographs (SEM), when the content of LS reached 50 wt% in blends. The mechanical properties, including tensile strength, elongation at break and impact strength decreased with the increase of LS content, while the Young’s modulus increased as LS content ncreased. The effect of LS content on the mechanical properties of LS/PCL blends was ascribed to rigidity of LS molecules and interactions between LS and PCL.The lignosulfonate was modified with maleic anhydride in order to improve mechanical properties of LS/PCL blends. And lignosulfonate was esterified with maleic anhydride in alkali water solution under mild heat and stir condition. The structure of the obtained maleated lignosulfonate (MLS) was verified through Fourier transform infrared spectroscopy (FT-IR) and the thermal properties of MLS were also determined through DSC and thermogravimetry analysis(TGA). Then VILS was blended with PCL under the same conditions as that of LS/PCL blends. The MLS/PCL blends were characterized by ATR-IR, SEM, DSC and so on. The results showed that the interactions between VILS and PCL were much stronger than that between LS and PCL, and the MLS particles well distributed in the PCL matrix. What is more, the mechanical properties of MLS/PCL blends were obviously improved compared with mechanical properties of LS/PCL blends. And the LS/PCL blends and MLS/PCL blends are biodegradable, which was tested from soilburial experiments. Other factors, such as melt :emperature, which had an influence on interactions between MLS and PCL, and addition of DOP, which improved the roughness of MLS/PCL blends, were also investigated.