Kraft lignin

For the preparation of the nanocomposites, PLA of molar mass Mw~75 kg/mol with ~96% of L- and ~4% of D- forms was employed, and was obtained from Plastika Kritis S.A. (Iraklion, Greece). As reported in our previous study [19 (link)], for this molecular weight and based on titration measurements, the fractions of –COOH and –OH groups of PLA were calculated as, approximately, 3 meq/kg and 17 meq/kg, respectively. Tannin (T) and Kraft-Lignin (KL) were purchased from Sigma-Aldrich. According to dynamic light scattering (ZetaSizer 5000, Malvern company, Worcestershire, United Kingdom) measurements, the average particle size of the powders, which were measured in water, was found to be 612 nm for kraft-lignin (polydispersity index, PDI~0.64) and 454 nm for tannin (PDI~0.44).

A biobased Polyamide 11 (PA), Rilsan® BMNO-TLD; Mn = 17,000 g/mol, melt flow index (MFI) =14–20 g/10 min at 235 °C, supplied from Arkema (Colombes, France), was chosen as the polymer matrix. The lignin used as charring agent is a kraft lignin (KL) purchased from Sigma Aldrich (Darmstadt, Germany). Ammonium polyphosphate (AP) with the reference Exolit AP 422 was supplied by Clariant (Muttenz, Switzerland). The both additives consist of a thin powder with an averaged particle size of 39 µm and 15 µm respectively. All the materials were dried at 80 °C for 24 h before any use.

The polymer used in this study as the matrix was neat PLA, poly (L-lactic acid, with 96% of L and 4% of D isomer) and was provided by Plastika Kritis S.A. (Iraklion, Greece) with molecular weight Mw~75 kg/mol and intrinsic viscosity η = 1.24 dL/g. Kraft lignin (KL) and tannin (TANN) samples were acquired from Sigma-Aldrich. The physiochemical properties of KL and TANN were described in our previously published work [45 (link),46 (link)].

All chemicals used were of the highest purity
available. Aqueous solutions were prepared in deionized water with
an electrical resistivity of ≥18 MΩ cm at 25 °C.
Cellobiose (C7252) was purchased from Merck. Cello-oligosaccharides
and hemicelluloses were purchased from Megazyme (Wicklow, Ireland):
cellotriose (O-CTR-50MG), cellotetraose (O-CTE-50MG), cellopentaose
(O-CPE-20MG), β-glucan from barley (high viscosity, P-BGBH),
β-glucans from barley (low viscosity, P-BGBL), glucomannan (GM)
from konjac tubers (low viscosity, P-GLCML), xyloglucan from tamarind
seeds (P-XYGLN), galactan from lupin seeds (P-GALLU), lichenan from
icelandic moss (P-LICHN), arabinoxylan from wheat flour (medium viscosity,
P-WAXYM), mannan (1,4-β-d-Mannan, P-MANCB), xylan from
birchwood (partially acetylated, P-ACXYL), xylan from beechwood (P-XYLNBE-10G),
and curdlan (P-CURDL). Phosphoric acid-swollen cellulose (PASC) was
prepared according to a published protocol^{63 (link)} from microcrystalline cellulose (MCC) (d = 50 μm,
11365, Avicel PH-101, Merck). Crystalline nanocellulose (CNC, d = 10–20 nm × l = 300–900
nm, NG01NC0101) was purchased from Nanografi Nanotechnology (Ankara,
Turkey). Kraft lignin (370959) and horseradish peroxidase (77332)
were purchased from Merck.

Halloysite nanoclay (Al₂Si₂O₅(OH)₄·2H₂O), with a molecular weight equal to 294.19 g/mol and the CAS number: 1332-58-7, was purchased from Merck, Darmstadt, Germany, and kraft lignin purchased from Merck, Darmstadt, Germany (average M_w ~10,000 g/mol, CAS number: 8068-05-1) were used in these studies as fillers.
The rigid PVC dry blend is composed of a suspension of PVC S-61 Neralit (Spolana Anwil Group, Neratovice, Czech Republic) 100 phr and organotin stabilizer Patstab 2310 (Patcham, Goor, The Netherlands) 4 phr, and 1 phr Naftolube FTP paraffin wax (Chemson, Arnoldstein, Austria) was employed as the matrix for the composites. Stabilizer and paraffin wax were the only added components in order to minimize the influence of additives on processing properties.

Kraft lignin, sodium dodecyl sulfate (SDS), decyltrimethylammonium bromide (DeTAB), hexadecyltrimethylammonium bromide (CTAB), and Triton X-100 (TX-100) were purchased from Merck (Algés, Portugal). Sodium octyl sulfate (SOS), sodium decyl sulfate (SDeS), and polysorbate 20 (PS20) were acquired from Fluka (Bunchs, Switzerland). Octyltrimethylammonium bromide (OTAB) was obtained from Tokyo Kasei Kogyo Co., Ltd. (Tokyo, Japan) and tetradecyltrimethylammonium bromide (TTAB) was purchased from LabKemi (Stockholm, Sweden). Sodium hydroxide (NaOH) was purchased from José Manuel Gomes dos Santos, Lda., (Porto, Portugal) and formic acid from Merck (Algés, Portugal). All the chemicals were used as received. Maritime pine (Pinus pinaster Ait.) sawdust was received from Valco - Madeiras e Derivados, S.A. (Leiria, Portugal) as a kind gift and was dried before further use.

Isopropyl alcohol was purchased from Honeywell (Hanover, Germany). Petroleum solvent, Nefras grade C2-80/120, was purchased from “Latvijas ķīmija” (Riga, Latvia). Activated charcoal powder, chloroform-d, Kraft lignin, and beechwood xylan were purchased from Merck KGaA (Darmstadt, Germany). Nanofibrillated cellulose (NFC) was produced from old filter paper waste according to the method previously reported by the authors [27 (link)]. NFC sizes ranged from 40 to 120 nm in diameter, and fiber lengths from around 500 to 2000 nm. Pine needles (Pinus sylvestris, L.) were gathered locally in Latvia through a forestry company.