Eduardo F. Kerche

In this work, rigid polyurethane foams (RPUF) reinforced by micro fibrillated cellulose (MFC) were manufactured using the free rising method and also under confinement inside a closed mould, aiming to increase apparent density and improve mechanical response. Neat RPUF were also manufactured for comparison. The mechanical response, evaluated by compression (following ASTM D1621 standard) tests were correlated with the final composite apparent density (evaluated following ASTM D1622 standard). Simple linear regression statistical models, based on F-test, were developed using stat graphics software, aiming to understand and correlate the increment in density and its influence on the improvement in mechanical response. Different models were developed to describe the foam behavior. The main results show a more significant influence of the density on strength than stiffness for the neat RPUF, unlike the MFC-reinforced RPUF, which presented an opposite response. These effects could be cau...

Micro crystalline cellulose is largely used to improve thermos-mechanical properties of composites. This study aims to evaluate the creep behaviour of micro-cellulose epoxy-based composites, and the effect of reinforcements’ silanization treatment. A new viscoelastic model, based on the generalized logistic function was successfully tested. The results were directly associated with the material’s structure-property relationships. Rigid particles restricted the molecular chain’s motion, mainly on the amorphous segments. This difference achieved the needing of more energy, to achieve creep deformation. Then, MCC improved the structural integrity, when incorporated into an epoxy matrix. On one hand, the incorporation of silanized-MCC increased the mechanical behavior of the composite, due to the stiffer structure. Furthermore, the chemical modification provided an increment in the glassy plateau, associated with higher thermal energy required to initiate strain of the amorphous polymer...

Polysaccharides are formed by a long chain of monosaccharides, with the main function of promoting energetic and structural reserves for plants and animals. They can be applied as a base of electrolytes, using ionic liquids (ILs) as a solvent base. The study of electrolytes is an emerging field, as they are applied as secondary batteries, fuel cells, solar cells, supercapacitors and chemical sensors. They operate stably under extreme conditions, maintaining their high thermal stability. Furthermore, their low cost and environmentally safe character, compared to conventional electrolytes, have attracted considerable attention in the scientific field. ILs are composed entirely of ions and could be potentially applied as solvents. As electrolytes, ILs are environmentally friendly, and their use in combination with polysaccharides leads to a synergic effect. In the present study, a systematic review was performed of all papers published from 2014 to 2022 regarding ILs and polysaccharide...

The materials sector usually seeks light, low cost and high performance materials and sandwich structures, which combine two external faces and a low density core, are an excellent choice for many applications. The aim of this study is to produce sandwich structures using a polyester matrix and sisal (Agave sisalana) fabrics with a PET core. Three types of sisal fabrics with distinct aerial density and architecture were produced for this work and their performance were compared with standard commercial glass-fiber fabric. The composite sandwiches were produced by vacuum infusion and characterized through longitudinal/axial compression and flexural testing. The obtained sandwich composites with sisal fabric showed mechanical performance similar or even superior than that of glass fibers for similar fiber volume fraction. Therefore, they were considered an attractive alternative for replacing glass fiber fabrics in selected industrial applications.

This study aims to evaluate the influence of using a bleached Curauá fiber (CF) as filler in a novel rigid polyurethane foam (RPUF) composite. The influence of 0.1, 0.5 and 1 wt.% of the reinforcements on the processing characteristics, cellular structure, mechanical, dynamic-mechanical, thermal, and flame behaviors were assessed and discussed for RPUF freely expanded. The results showed that the use of 0.5 wt.% of CF resulted in RPUF with smoother cell structure with low differences on the processing times and viscosity for the filled pre-polyol. These morphological features were responsible for the gains in mechanical properties, in both parallel and perpendicular rise directions, and better viscoelastic characteristics. Despite the gains, higher thermal conductivity and lower flammability were reported for the developed RPUF composites, related to the high content of cellulose and hemicellulose on the bleached CF chemical composition. This work shows the possibility of using a Br...