Influence of TMP fibers on the rate of biodegradation in soil of PHA structures

PONCE DE LEÓN, AGUSTINA; EHMAN, NANCI VANESA; FELISSIA, FERNANDO ESTEBAN; VALLEJOS, MARÍA EVANGELINA; CHINGA CARRASCO, GARY; AREA, MARÍA CRISTINA

Conferencia; XXV TECNICELPA / XI CIADICYP Conference 2021; 2021

This work aimed to evaluate the effect of the addition of thermomechanical pulp (TMP) on the rate of biodegradation in soil of polyhydroxyalkanoates (PHA) structures. Three samples were tested: 20% TMP pulp/PHA, 20% TMP with 5% elastomer in PHA matrix, and pure PHA as a reference. The mixes were extruded to produce filaments of 1.7 mm diameter, which were used to print structures by fused deposition modeling. The 3D structures were buried in soil and were maintained under environmental conditions to perform the analysis of biodegradation. The weight loss was determined after 48, 92, 158, and 260 days. The climate conditions (temperature, relative humidity, precipitation, and atmospheric pressure) were measured during the period. Finally, the rate of the biodegradation was estimated using the weight loss, the area of the structures, and the buried time. The initial visual inspection of the samples after 260 days showed a degraded surface, which could indicate biodegradation by an erosion mechanism. Furthermore, the samples showed color changes, which could indicate that the microorganisms attack the amorphous lignin in the fibrous fraction.The results showed a 12% of increase for the rate of biodegradation in the soil for the samples with 20% of TMP fibers and 80% PHA respect to 100% PHA (from 0.055 to 0.062 mg. day-1 cm-2) whilst with the inclusion of elastomer the increase was 73% (increase up to 0.096 mg. day-1 cm-2). The weight loss of the structures was higher for the first period up to 48 days with a weight loss of 2.9% (20%TMP/80%PHA), 5.1% with the use of 20%TMP/80%(PHA + elastomer) in comparison with the 100% PHA structure (2.0%). Lower rate of biodegradation was observed in the following periods, reaching in all cases a weight loss lower than 5%. However, in the last period, the rate of biodegradation was higher respect the previous period for all samples, which can be attributed to the increase in temperatures and precipitations (up to 37°C and 685 mm, respectively).