Dynamic mechanical analysis (DMA) is one of the most common methods employed to study a material’s viscoelastic properties. The effect of thermal aging on plain epoxy and a fique fabric-reinforced epoxy composite was investigated by comparing the mass loss, morphologies, and DMA properties of aged and unaged samples. In fact, thermal aging presents a big challenge for the high-temperature applications of natural fiber composites. In this work, both plain epoxy and fique fabric-reinforced epoxy composite were found to have different molecular mobility. This leads to distinct transition regions, with different changes in intensity caused by external loadings from time-aging. Three exponentially modified Gauss distribution functions (EMGs) were applied to loss factor curves of fique fabric-reinforced epoxy composite and plain epoxy, which allowed identifying three possible mobility ranges. From these results it was proposed that the thermal degradation behavior of natural fibers, especially fique fiber and their composites, might be assessed, based on their structural characteristics and mechanical properties.

With its extensive production and consumption, the coffee industry generates significant amounts of lignocellulosic waste. This waste, primarily comprising coffee biomasses, is a potential source of cellulose. This cellulose can be extracted and utilized as a reinforcing agent in various biocomposites with polymer matrices, thereby creating high-value products. One such biodegradable polymer, Poly(butylene adipate-co-terephthalate) (PBAT), is notable for its properties that are comparable with low-density polyethylene, making it an excellent candidate for packaging applications. However, the wider adoption of PBAT is hindered by its relatively high cost and lower thermomechanical properties compared with conventional, non-biodegradable polymers. By reinforcing PBAT-based biocomposites with cellulose, it is possible to enhance their thermomechanical strength, as well as improve their water vapor and oxygen barrier capabilities, surpassing those of pure PBAT. Consequently, this study aims to provide a comprehensive review of the latest processing techniques for deriving cellulose from the coffee industry’s lignocellulosic by-products and other coffee-related agro-industrial wastes. It also focuses on the preparation and characterization of cellulose-reinforced PBAT biocomposites.

Nanocomposites of poly (3-hydroxybutyrate) (PHB) containing fibrillated cellulose extracted from eucalyptus fibers were prepared and characterized. This study focuses initially on the method to follow the acid treatment of eucalyptus cellulose fibers (ECF) through an experimental design, where the studied parameters were the H₂SO₄ concentration, hydrolysis time, and reaction temperatures as independent variables for statistical analysis. The thermogravimetric analysis (TGA) of the ECF revealed that mild hydrolysis conditions shifted the degradation temperature of the fibers to higher values. The crystallinity index (CI) obtained by the X-ray diffraction was greater when intermediate hydrolysis conditions (30% H₂SO₄, 60 °C, 150 min) were employed. Afterward, the most promising ECFs hydrolyzed according to the experimental design were used to produce nanocomposites of PHB(ECF/PHB) containing 5 wt% of the fiber reinforcement via twin-screw mini extruder Haake MiniLab II operating at 180 °C, and varying the rotation speeds (60, 120, and 180 rpm). The ECF/PHB nanocomposites were characterized by TGA and dynamic mechanical analysis (DMA), through which the selected composites with higher thermal and mechanical properties were analyzed by differential scanning calorimetry (DSC), tensile test, and scanning electron microscopy (SEM). ECF/PHB nanocomposites processed at 120 rpm resulted in a material with improved properties. The DMA storage and loss moduli as well as the tensile elastic modulus increased 65%, 196% and 15%, respectively, as compared to the neat PHB. The SEM of the composites revealed nanowhiskers, microcrystalline and microfibrillated cellulose incorporated into PHB, which were attributed to improvements in the thermal and mechanical properties of the PHB matrix.