Table 1. Chemical composition of PU samples

Variable	PEG	PEG1/KL1	PEG2/KL1	PEG3/KL1	PEG1/ESL1	PEG2/ESL1	PEG3/ESL1
PEG (wt%)	59.7	30.8	40.6	45.5	29.3	39.4	44.4
KL (wt%)	.	30.8	20.3	15.2	.	.	.
ESL (wt%)	.	.	.	.	29.3	19.6	14.8
MDI (wt%)	37.3	35.4	36.1	36.4	38.5	38.1	37.9
DBTDL (wt%)	5	5	5	5	5	5	5
NCO index	100	118	120	112	118	109	108
NCO/OH ratio	1.0	1.0	1.0	1.0	1.0	1.0	1.0

PU: polyurethane, PEG: polyethylene glycol, KL: kraft lignin, ESL: ethanol-soluble lignin, MDI: 4,4’-diphenylmethane diisocyanate, DBTDL: dibutyltin dilaurate.