Abstract
Abstract In this work, bottle-grade poly(ethylene terephthalate) (PETR), kraft lignin (KL), and chemically modified lignin (ML) were used to form blends to improve the mechanical and thermal properties of pure PET. The PET/KL and PETR/ML blends were produced with 0.5, 1, 3, and 5 wt.% of lignin via melt extrusion and injection molding. The produced blends and PETR were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and mechanical properties testing. The FTIR measurements confirmed the chemical modifications of the ML samples, while the TGA results showed KL to be thermally more stable than ML. The glass transition temperature of PETR changed as a function of the amount of lignin, as revealed by the DSC measurements. The PET/KL blends demonstrated their potential for use as an engineering material due to their improved thermal and mechanical properties compared to those of PETR.
Highlights
Synthetic or petroleum-based polymers have many practical uses; their low biodegradability causes serious environmental problems
The results of ATR-Fourier transform infrared spectroscopy (FTIR), TGA, and Differential Scanning Calorimetry (DSC) analyses verified the presence of chemical modifications in the modified lignin (ML) samples
The TGA measurements indicated that kraft lignin (KL) was thermally more stable than ML, which is intrinsically linked to the ability of ML to absorb water, increasing this material’s susceptibility to degradation
Summary
Synthetic or petroleum-based polymers have many practical uses; their low biodegradability causes serious environmental problems. Several strategies to replace or reduce the use of synthetic polymers have been developed[1,2,3,4]. Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic aromatic polyester known for its mechanical properties, lightness, strength, and high transparency, which ensure its widespread use in food and cosmetic packaging materials[2,6,7,8,9,10]. Recycled PET is often mixed with other polymers or fillers to produce polymer blends or composites with different mechanical and thermal properties compared to neat polymers, adding value to raw materials. For added-value processes to be consistently efficient, the compatibility between mixture components is highly essential to achieve satisfactory thermal and mechanical properties for a specific application[11,12,13]. Mechanical enhancements may be useful to the automobile and civil construction industries, while improvements of thermal stability would be useful for applications in the packaging and electronics industries
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