L lactide

Polylactic acid (PLA) Ingeo 4043D, with a content of 98% L-lactide, an average molecular weight (M_w) of 111 kDa, and a density of 1.24 g/cm³ was purchased from NatureWorks (Minnetonka, MN, USA). PHB powder with M_w 490 kDa and a density of 1.25 g/cm³ was purchased from Biomer (Schwalbach am Taunus, Germany) and acetyl tributyl citrate (ABC) plasticizer from Sigma-Aldrich (Burlington, MA, USA). Microcrystalline cellulose (MCC) powder with a mean particle size of 20 µm was supplied by Sigma-Aldrich (Schnelldorf, Germany). Mixed softwood and hardwood waste was collected from wood exploitations and timber factories. Sulfuric acid 96% from Fluka (Buchs, Switzerland) was used for the treatment of MCC.

Plum seed shells derived from Romanian varieties of plum trees were used as raw material to produce cellulose nanocrystals (NC). Sodium hydroxide (NaOH, ≥99%, Carl Roth, Karlsruhe, Germany), sulfuric acid (H₂SO₄, 95–97%, Fluka, Buchs, Switzerland), sodium chlorite (NaClO₂, 80%, Carl Roth, Karlsruhe, Germany), hydrogen peroxide (H₂O₂, 30%, Merck, Darmstadt, Germany) and acetic acid (CH₃COOH, 99–100% min., Carl Roth, Karlsruhe, Germany) were used for cellulose nanocrystals production. Amorphous grade polylactic acid pellets (PLA, Ingeo™ biopolymer 4043D, 1.24 g cm⁻³), L-lactide content about 98% from NatureWorks (Blair, NE, USA), and pelletized PHB from Goodfellow (Huntingdon, UK, 1.25 g cm⁻³) were used as polymer matrices. Cellulose nanocrystals, with a diameter between 30 and 80 nm, were isolated from plum seed shells and were used to modify the PLA/PHB blend. Dicumyl peroxide (DCP, 98%, Sigma-Aldrich, Steinheim, Germany) was used as a cross-linker.

PLA 2002D containing 96% of L-lactide and supplied by NatureWorks^®, Minnetonka, Minnesota USA having melt flow index (MFI) (2.16 kg/190 C) 4–8 g/10 min, was used as a polymer matrix. Before processing, PLA was dried in a vacuum oven at 110 °C for 12 h. 9H-carbazole-ethanol (CA, Aldrich, St. Louis, Missouri, USA), 9-fluorenyl-methanol (FM, Aldrich; St. Louis, Missouri, USA), 2-[4-(2-chloro-4-nitrophenylazo)-N-ethyl-phenylamino]ethanol (disperse red 13, DR, Aldrich), tin(II) 2-ethylhexanoate or stannous octoate (Sn(Oct)₂) (Aldrich, St. Louis, Missouri, USA), chloroform (for HPLC, ≥ 99.8 %, contains 0.5–1.0% of ethanol as stabilizer) were used as received. L-lactide (Aldrich, St. Louis, Missouri, USA) was sublimed before use.