ABSTRACT
In this study, bio-adhesives from natural rubber latex (NRL) were combined with starch and formic acid to fabricate jute stick-based particleboards (JSPs). Different blends of NRL, starch, and formic acid, i.e., 6 : 1 : 1, 2 : 1 : 1, and 2 : 3 : 3, were used to produce particleboards using a pressing temperature of 180 °C and applied pressure of 5 MPa using a 5 min pressing time. The particleboards were tested for physical, mechanical, and thermal properties according to ANSI standards. Based on initial screening, the best formula (NRL/starch/formic acid of 2 : 3 : 3) was used to optimize the temperature and pressing time for the highest board performance. The highest density, tensile strength, modulus of elasticity, and modulus of rupture were 830 g cm-3, 10.51, 2380, and 20.05 N mm-2, respectively. Thermo-gravimetric analysis indicated that thermal decomposition of samples primarily occurred in a temperature range of 265 to 399 °C, indicating good thermal performance. The measured physical and mechanical properties of the produced JSPs fulfilled the production standards. However, fulfilling the water absorption and thickness swelling criteria was a challenge. The results indicate that NRL is a promising alternative binder when blended with starch and formic acid.
ABSTRACT
The recent rapid expansion of thin-film, bendable, and wearable consumer (opto)electronics demands flexible and transparent substrates other than glass. Plastics are the traditional choice, but they require amelioration because of their thermal instability. Here, we report the successful conversion of a soft and thermally vulnerable polymer into a highly thermally stable transparent nanocomposite material. This is achieved by the meticulous choice of a polymer with a glass-transition temperature below 0 °C that gives stable mechanics above room temperature, reinforcing the polymer with a load-bearing hierarchical network of the incredibly strong and stable natural material: cellulose nanorods. Owing to the Pickering emulsification process, the nanocomposites inherit the self-assembled structural hierarchy from the cellulose nanorod-encapsulated resin droplets. The ameliorated nanocomposites have highly desirable high-temperature endurance (â¼150-180 °C) in terms of the thermomechanical, thermodimensional, and thermo-optical performance. Any photonic nano- or microstructures can be directly molded on the surface of the nanocomposites in high precision for better light management in photonic and opto-electronic applications. The highlight of this work is the demonstration of a highly thermally stable microlens array on the ameliorated transparent nanocomposite.
ABSTRACT
Achieving a structural hierarchy and a uniform nanofiller dispersion simultaneously remains highly challenging for obtaining a robust polymer nanocomposite of immiscible components. In this study, a remarkably facile Pickering emulsification approach is developed to fabricate hierarchical composites of immiscible acrylic polymer and native cellulose nanofibers by taking advantage of the dual role of the nanofibers as both emulsion stabilizer and polymer reinforcement. The composites feature a unique "reverse" nacre-like microstructure reinforced with a well-dispersed two-tier hierarchical nanofiber network, leading to a synergistic high strength, modulus, and toughness (20, 50, and 53 times that of neat polymer, respectively), high optical transparency (89%), high flexibility, and a drastically low thermal expansion (13 ppm K-1, 1/15th of the neat polymer). The nanocomposites have a three-dimensional-shape moldability, also their surface can be patterned with micro/nanoscale features with high fidelity by in situ compression molding, making them attractive as the substrate for flexible displays, smart contact lens devices, and photovoltaics. The Pickering emulsification approach should be broadly applicable for the fabrication of novel functional materials of various immiscible components.
ABSTRACT
Doubly curved nanofiber-reinforced optically transparent composites with low thermal expansion of 15 ppm/k are prepared by hot pressing vacuum-filtered Pickering emulsions of hydrophobic acrylic resin monomer, hydrophilic chitin nanofibers and water. The coalescence of acrylic monomer droplets in the emulsion is prevented by the chitin nanofibers network. This transparent composite has 3D shape moldability, making it attractive for optical precision parts.
