Hemicellulose biodegradable films prepared by a rapid method

Y.N. SOLIER; ZANUTTINI M.A.; MOCCHIUTTI PAULINA; SCHNELL, CARLA N.; GALVÁN, MARÍA V.; INALBON, MARÍA C.

Coimbra

Conferencia; XXV Tecnicelpa International Forest, Pulp and Paper Conference / XI CIADICyP Iberoamerican Congress on Pulp and Paper Research (2021), Web International Conference; 2021

TECNICELPA/ CIADICYP

Hemicelluloses are an interesting renewable resource to obtain new value-added materials, such as films, coatings, composites among others. In this work, the film formation of hemicelluloses from sugar cane bagasse (xylan, X) complexed with chitosan (Q) is investigated. Instead of the drop wise addition, polyelectrolyte solutions were rapidly mixed and instead of the slow traditional casting/evaporation method, a fast evaporation of the suspension prior to the final oven drying (with a specific volume reduction) is proposed. These alternatives considerably reduce the time of film preparation. The biodegradability and the mechanical properties of these films is evaluated.Xylan solution (4 g/l) was quickly added on chitosan solution (2.2 g/l) and the suspension was stirred during 15 minutes. Then, it was sonicated for 2 min. After that, the volume of the suspension was reduced, evaporating 75% of the water from the suspension at 100 ºC, under vigorous stirring. Finally, the solution was treated in an ultrasonic bath during 2 minutes (to remove the excess of air) and then dried in an oven at 70 ºC to complete the film formation. The traditional casting/evaporation method (without the fast evaporation at 100 ºC) was also evaluated to compare the new procedure proposed. Two mass ratios were used, 70/30 and 80/20 (X/Q). Mechanical properties (stress and strain at break) and the biodegradability during 25 days of the films were determined according to ASTM D882 and ASTM D5338-98 with some modifications. Erlenmeyer flasks were charged with wet perlite, commercial organic soil, sample (film pieces of 4 cm2 of area) corresponding to approximately 300 mg of carbon, commercial organic soil and finally wet perlite. Flasks placed in an oven at 50 ºC were aerated every day during 2 hours. The CO2 in the air flow, produced by the biodegradation of the films, was trapped in a Ba(OH)2 solution and determined by indirect titration with HCl. Homogeneous, translucent, brownish and handable films were obtained in all cases, with both mass ratios and methods proposed. The addition of plasticizer or crosslinking agent was avoided. The new method proposed did not affect mechanical properties of the films. In all cases these properties were acceptable and film were flexible. When hemicellulose content in the film was increased, the stress at break clearly was increased (from 10 to 22 MPa) and the strain at break was decreased (from 24 to 13%). This behavior could be explained by the crystallinity produced by xylan. Films were fast degraded. During the first 10 days, 10% of mass was lost. Then, the degradation rate was much slower. In this test, no effect of the mass ratio neither the method employed in the film preparation was found. When flasks were discharged after the period of burial condition, it was observed that the pieces of samples were clearly affected. The biodegradability, determined under burial conditions, were similar to that of other biodegradable film that currently exist on the market