Effect of Spent Coffee Grounds on the Crystallinity and Viscoelastic Behavior of Polylactic Acid Composites.

This work investigated the addition of spent coffee grounds (SCG) as a valuable resource to produce biocomposites based on polylactic acid (PLA). PLA has a positive biodegradation effect but generates poor proprieties, depending on its molecular structure. The PLA and SCG (0, 10, 20 and 30 wt.%) were mixed via twin-screw extrusion and molded by compression to determine the effect of composition on several properties, including mechanical (impact strength), physical (density and porosity), thermal (crystallinity and transition temperature) and rheological (melt and solid state). The PLA crystallinity was found to increase after processing and filler addition (34-70% in the 1st heating) due to a heterogeneous nucleation effect, leading to composites with lower glass transition temperature (1-3 °C) and higher stiffness (~15%). Moreover, the composites had lower density (1.29, 1.24 and 1.16 g/cm3) and toughness (30.2, 26.8 and 19.2 J/m) as the filler content increased, which is associated with the presence of rigid particles and residual extractives from SCG. In the melt state, polymeric chain mobility was enhanced, and composites with a higher filler content became less viscous. Overall, the composite with 20 wt.% SCG provided the most balanced properties being similar to or better than neat PLA but at a lower cost. This composite could be applied not only to replace conventional PLA products, such as packaging and 3D printing, but also to other applications requiring lower density and higher stiffness.

Waste Paper as a Valuable Resource: An Overview of Recent Trends in the Polymeric Composites Field.

This review focuses on polymeric waste-paper composites, including state-of-the-art analysis with quantitative and qualitative discussions. Waste paper is a valuable cellulose-rich material, produced mainly from office paper, newspaper, and paper sludge, which can be recycled and returned to paper production or used in a new life cycle. A systematic literature review found 75 publications on this material over the last 27 years, with half of those published during the last five years. These data represent an increasing trend in the number of publications and citations that have shown an interest in this field. Most of them investigated the physicomechanical properties of composites using different contents of raw waste paper or the treated, modified, and cellulose-extracted types. The results show that polyethylene and polypropylene are the most used matrices, but polylactic acid, a biodegradable/sourced polymer, has the most citations. The scientific relevance of waste-paper composites as a subject includes the increasing trend of the number of publications and citations over the years, as well as the gaps identified by keyword mapping and the qualitative discussion of the papers. Therefore, biopolymers and biobased polymers could be investigated more, as well as novel applications. The environmental impact in terms of stability and degradation should also receive more attention regarding sustainability and life cycle analyses.

Effect of chemical treatment of pineapple crown fiber in the production, chemical composition, crystalline structure, thermal stability and thermal degradation kinetic properties of cellulosic materials.

Recently, the growing environmental concerns and economic demands have driven the need to develop effective solutions for the treatment of vegetal fibers to be used as renewable source for various industrial applications. The present study aimed to explore pineapple crown fibers (PCs) as an alternative source of cellulose. The three treatments (alcohol-insoluble residue (AIR), alkaline (AT), and organosolv) evaluated promoted chemical and morphological changes to the PCs. Fresh and treated PCs were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TG), and chemical composition. The XRD results showed that the Cellulose-I allomorph was not altered during extraction, and that the crystallinity index of the fibers treated with AT, first bleaching step, second bleaching step, and the second bleaching step followed by KOH treatment (2B_KOH) increased to 77.8; 83.2; 83.5 and 86% when compared with fresh PC (62.3%). Results from the thermal analysis revealed that thermal stability increased for the isolated cellulose, and the maximum degradation for (2B_KOH) is 350 °C. Chemical composition results showed a decrease in the content of hemicellulose, lignin and other soluble materials after alkaline treatment, suggesting high-quality 2B_KOH with 74.6% of cellulose. SEM revealed changes in the morphological structure on fibers. Alkaline treatment followed by H2O2 bleaching is an excellent alternative for the removal of non-cellulosic material and facilitates the isolation of cellulose. These results suggested that there is a potential to isolate cellulose from PC via the sequence of treatment of a methodology by chlorite-free.

Obtainment and characterization of nanocellulose from an unwoven industrial textile cotton waste: Effect of acid hydrolysis conditions.

Cellulose nanocrystals (CNCs) have a promising application in many advanced products, such as biomedical applications and hydrogels. In this research, industrial cotton waste was treated using alkali and bleaching to eliminate hemicellulose, lignin, and other amorphous contents. The efficiency of these treatments was proven by chemical compositions analysis, which showed an increase in cellulose percentage with the progression of treatments. Fibers were analyzed by X-ray diffraction, thermogravimetric, and Scanning Electron Microscopy (SEM). CNCs were then prepared by acid hydrolysis using different sulfuric acid concentrations (50 wt%, 60 wt% and 64 wt%) and two reactions time (60 min. and 75 min.) resulting in six CNCs suspensions. CNCs were analyzed by X-ray diffraction, thermogravimetric, zeta potential, and Transmission Electron Microscopy (TEM). CNCs obtained exhibited a good crystallinity index varying from 75 to 81% and thermal stability between 146 °C and 200 °C. TEM analysis showed that sulfuric acid concentration influenced in CNCs length (105 nm-5880 nm). By analyzing all results, the optimal parameters for acid hydrolysis were 64% (w/w) of acid concentration combined with 60 min. of reaction time. The preparation of CNCs in this work showed some prospects of using untraditional industrial cotton waste as an advanced material.

Effect of different degradation types on properties of plastic waste obtained from espresso coffee capsules.

In terms of large use of plastic products, a necessity exists to minimize effects of the waste produced on environment by recycling, reuse and application in new products. In Brazil, the espresso coffee capsules are an emerging plastic waste, representing 0.9% of the coffee consumed in 2017. Therefore, Nescafé Dolce Gusto espresso coffee capsules were chosen in order to understand the polypropylene stabilization and degradation initiators with the purpose of recycling by applying in a composite material, as home composting product. In this context, the plastic capsule wastes were exposed to chemical, thermal, accelerated weathering (ultraviolet radiation + humidity) and natural weathering in order to analyze the influence of exposure and possibilities of a real application in a composting environment. Masses of the samples were monitored before and during the weathering conditions. Thermal (TGA and DSC) and chemical (FTIR) analysis were carried out before and after exposure. No changes in thermal stability were observed, however, samples conditioned in acid solution presented thermal degradation event beginning at 131 °C. In addition, all samples presented a similar behavior of melting and crystallization points, which did not change with exposure. FTIR analysis showed a disappearance of CC and CO bonds on samples exposed to natural weathering and basic solution conditioning. It also showed formation of chromophores groups on samples exposed to accelerated weathering. The visual analysis showed huge differences in samples exposed to accelerated weathering and acid solution, which were the most damaged. On the other hand, samples exposed to natural weathering, thermal and basic conditioning did not presented significantly changes supported by the TGA and FTIR results.

Preparation of nanocellulose from Imperata brasiliensis grass using Taguchi method.

Cellulose nanoparticles (CNs) were prepared by acid hydrolysis of the cellulose pulp extracted from the Brazilian satintail (Imperata Brasiliensis) plant using a conventional and a total chlorine free method. Initially, a statistical design of experiment was carried out using Taguchi orthogonal array to study the hydrolysis parameters, and the main properties (crystallinity, thermal stability, morphology, and sizes) of the nanocellulose. X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), zeta potential and thermogravimetric analysis (TGA) were carried out to characterize the physical-chemical properties of the CNs obtained. Cellulose nanoparticles with diameter ranging from 10 to 60 nm and length between 150 and 250 nm were successfully obtained at sulfuric acid concentration of 64% (m/m), temperature 35 °C, reaction time 75 min, and a 1:20 (g/mL) pulp-to-solution ratio. Under this condition, the Imperata Brasiliensis CNs showed good stability in suspension, crystallinity index of 65%, and a cellulose degradation temperature of about 117 °C. Considering that these properties are similar to those of nanocelluloses from other lignocellulosics feedstocks, Imperata grass seems also to be a suitable source for nanocellulose production.