Abstract

The aim of this investigation is to correlate the percentage yields of pulp of twenty tropical hardwood species with their lignin and extractive contents. The hardwoods studied include Abura (Hallea ciliata), Afara (Terminalia superba), Agba (Entada gigas), Akomu (Pycnanthus angolensis), Akun (Uapaca guineensis), Eki-Eki (Lophira alata), Erimado (Ricindendron heudelotii), Erun-obo (Erythropleum suaveolens), Iroko (Milicia exelsa), Itako (Strombosia pustulata), Itara (Sacoglottis gabonensis), Mahogany (Khaya ivorensis), Masonia (Masonia altissima), Obeche (Triplochiton scleroxylon), Odoko (Ipomoea asarifolia), Ofun (Avicennia germinans), Okilolo (Symphona globulifera), Opepe (Nauclea diderrichii), Oporoporo (Pterygota macrocarpa) and Some (Ceiba pentadra). Hardwood species such as H. ciliata, T. superba and S. globulifera that gave pulp yield of 50% were found to have the lowest lignin contents in the range of 19.0 to 28.4% and extractives contents of 4.8 to 6.0%. The results obtained showed that there is significant negative correlation (p < 0.01 and r = -0.84) between the percentage pulp yield and the lignin contents as well as between percentage pulp yield and contents of extractive materials (p < 0.01, r = -0.811). However, a significant positive correlation (p < 0.01, r = 0.649) between the percentage lignin contents and the extractive components of the wood samples was observed. The chemical integrity of the pulp, lignin and extractive contents of the wood samples was confirmed by infra-red (i.r.) spectroscopic studies.

Key words: Tropical hardwood species, pulp yield, lignin content, extractives.