STRUCTURE AND THERMAL PROPERTIES OF MALEATED LIGNIN-RECYCLED POLYSTYRENE COMPOSITES

Abstract

In this work, the changes caused by a chemical modification of the properties and chemical structures of lignin are studied. Lignin from a mixture of Eucalyptus globulus and Eucalyptus nitens obtained through the kraft pulping process was used. The lignin was isolated by acid precipitation and modified by a reaction with maleic anhydride. Maleated lignin (ML) was incorporated to recycled polystyrene (rPS) at 2, 5, and 10 wt-% by a melt-blending process. Fourier transformed infrared spectroscopy (FT-IR) was used to determine the ML structure, and the morphology of rPS/ ML composites was studied by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the glass-transition temperature (T g ) and the thermal stability of rPS and rPS/ ML composites and were compared with virgin PS. The T g values of rPS and their composites were higher than those of the virgin PS. TGA revealed that the thermal stability of rPS with 2 and 5% of ML was slightly greater than that of the virgin PS. These results suggest that postconsumer PS can be used to obtain composite materials with good thermal properties. 4 . Alkaline lignin isolated from sugar cane bagasse blended with polar poly- mers as polyvinyl alcohol ( PVA), showed an increase of thermal stability due at least some miscibility of the lignin / PVA blend. The mechanical properties of the blends were not reported 5 . Lignin as powder product of the prehydrolysis of beech wood was used as filler on low density polyethylene (LDPE) and polypropylene (PP). In small concentration lignin acts as a stabilizer for PP, but over 10% acts as an initiator of degradation. On LDPE, lignin acts as a stabilizer at concentrations greater than 10%. For both polymers (PP and LDPE), the mechanical properties decrease with increasing lignin content 6 . Alkali lignin from bamboo was used to prepare poly(4-vinylpyridine) (PVP) / lignin blend film by the casting method. The glass transition temperature (T g ) of these blends increased with the increase of lignin content, which indicated that these blends were able to form a miscible phase due to the formation of intermolecular hydrogen bond between the hydroxyl of lignin and the pyridine ring of poly( 4-vinyl pyridine). The thermostability of these blends decreased with the increase of lignin content. Initially, an appreciable increase in the measured tensile strength was achieved with a lignin content of 15 %, at which the maximum value of tensile strength was reached but, the strain behaviour of these blend films was deteriorated 7 .In other study, commercial lignin (Protobind 100SA-140) was used as filler with and without silica , on polysiloxane as polymeric matrix. The results of the thermomechanical, physical, and thermal investigations have evidenced the fact that lignin inserted in a silicon matrix does not alter its properties, and in some cases (e.g. mechanical properties), it even induces a slight improvement of these, leading to the conclusion that lignin can be used as an extender for silicones, with positives effects mainly on the material's cost 8 . The miscibility of hardwood Kraft lignin with several synthetic polymers, polyethylene oxide (PEO), polyethylene terephthalate (PET), PP and PVA, has been analysed using thermal analysis and FT-IR spectroscopy. Miscible blends were observed in lignin / PEO and lignin / PET blends, while immiscible blend behavior in the blends of lignin / PP and lignin / PVA were reported 9 . Lignin from beech wood pre-hydrolysis with dioxane water mixture was used to study the oxidative stability of PP and recycled PP. Lignin was used in the concentration range from 0.5 to 10 wt-% with a commercial antioxidant (Irganox 1010). The antioxidant effect is increased with lignin concentration up to 5 wt-% 10