Biobased Composite Material Fabrication

Poly(hydroxybutyrate) (PHB), grade P226, with a melt flow rate of 10 g·10 min⁻¹ (180 °C, 5 kg), density of 1.25 g·cm⁻³ and number-average molecular weight of 22,200 ± 4500 [38 (link)], was supplied by Biomer (Schwalbach, Germany). Poly(lactic acid) (PLA), grade 3100HP, with a melt flow rate of 24 g·10 min⁻¹ (210 °C, 2.16 kg) and molecular weight of 148 kDa [39 (link)] was supplied by NatureWorks (Plymouth, MN, USA). The mechanically treated (micronized) cellulose pulp fibers (average length and width of 332 µm and 12.5 µm, respectively) were obtained through a micronization procedure from eucalyptus bleached kraft pulp and were kindly provided by a Portuguese pulp mill. The epoxidized linseed oil (ELO), composed of stearic (3–5%), palmitic (5–7%), oleic (18–26%), linoleic (14–20%) and linolenic (51–56%) acids, was acquired from Traquisa (Barcelona, Spain). ELO has an oxirane oxygen minimum of 8%, iodine value under 5%, density of 1.1 g·cm⁻³ and viscosity between 800 and 1200 cP. The nonionic surfactant GlucoPure^® Sense (GPS), composed of sunflower oil methylglucamide (52%), glycerin (5%), water (10%) and propyleneglycol (33%), was obtained from Clariant (Barcelona, Spain). Compost medium Nutrimais Pulverulento, obtained by selective composting of lignocellulosic residues from forest exploration and from food wastes, was acquired from Nutrimais (Gondomar, Portugal). The specifications of the compost medium are as follows: moisture = 29.23 ± 1.41%, water-holding capacity = 170.33 ± 12.34%, organic matter = 57.66 ± 11.5%, pH = 8.9 ± 0.6, and elemental composition = 32.03 ± 2.66% (total carbon (C)), 2.41 ± 0.48% (total nitrogen (N)), 1.96 ± 0.39 (total potassium (K)), 0.71 ± 0.14% (total magnesium (Mg)), 14.50 ± 2.90% (total calcium (Ca)), and 1.33 ± 0.27% (total phosphorous (P)).