Adhesive based upon polyvinyl alcohol and chemical modified oca (Oxalis tuberosa) starch

The development of adhesives from renewable raw materials attract the attention of the scientific community, due to it promises the reduction of the dependence with materials derived from oil. This work proposes the use of modified “oca (oxalis tuberose)” starch and polyvinyl alcohol (PVA) in the elaboration of adhesives for lignocellulose substrates. The investigation focused on the formulation of adhesives with 3 different PVA:starch (modified and native) ratios (of 1:0,33; 1:1; 1:1,67 ). The first step to perform it was the chemical modification of starch through acid hydrolysis and a subsequent urea treatment to get carbonate starch. Then, the adhesive obtained was characterized in terms of instantaneous viscosity, Fourier-transform infrared spectroscopy (FTIR) and shear strength. The results showed that viscosity and mechanical tests exhibit data with the same tendency in relation to the native and modified starch concentration. Itwas observed that the data started to reduce its values to a certain concentration, where the values began to grow. On the other hand, 2 relevant bands were found in the FTIR spectrogram. The firstin 3300 cm-1of OH group with the same intensity for all the essays and the other one in 2900 cm-1belonging to the group of alkanes with a different intensity for each adhesive. On the whole, theratio PVA:starch (1:1) will not favor crosslinking in the adhesive structure and causes the viscosity reduction whereas in the others ones the viscosity is higher. It was also observed that adhesives made with modified starch had better characteristic, but the adhesives with high concentrations of native starch could equals the properties of the adhesives made with low.

Author(s): Borja Samantha; Molina Pamela and Valle Vladimir

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