Efeito de técnicas de recurtimento sobre a resistência do couro da tilápia do Nilo (<em>Oreochromis niloticus</em> L.)

Abstract

The aim of this work was to evaluate the resistance of the Nile Tilapia leather (Oreochromis niloticus) tanned with chromium salts and different techniques of retanning. The skin was distributed in randomized blocks, in a 4x2 factorial design, presenting four techniques of retanning, (T1 = 4% of chromium salts; T2 = 4% vegetal tanning barks; T3 = 4% synthetic tanning barks and T4 = 2% synthetic tanning barks and 2% vegetables) and two directions of the leather (S1=Longitudinal; S2=Transversal), with 6 repetitions. In order to determine the resistance to traction, elongation and gradual tearing were used dynamometer EMIC, with offset speed between 100 loads ± 20 mm/mm, in climatized environment (±23 o C and UR of the 50% air), for 24 hours (ABNT-NBR 10455, 1988). The retanning technique influenced the thickness of the leather which became inferior (1.30 to 1.53 mm) to other treatments due to the chromium salts (T1=0.61 to 0.68 mm). The course of the leather did not influence the thickness. The leather retanned with chromium salts did not present significant values for traction (30.31 N/mm 2 ), elongation (52.42%) and gradual tearing (91.23 N/mm) compared with the tanned ones with vegetal, synthetic tanning barks or combined values. The longitudinal section of the leather presented superior traction (23.00 N/mm 2 ) compared with the transversal line (12.3 N/mm 2 ); however it did not differ in the test from elongation and gradual tearing between the longitudinal and the transversal one. According to standards in literature, the leather tanned in chromium should present a resistance to traction of about 9.80 N/mm 2 , 60% for elongation and 14.0 N/mm for rip. The skin tanned with chromium and retanned with chromium salts presented the more adequate values to the recommended one for clothes confection