Chemical modification of Norway spruce (Picea abies (L) Karst) wood with melamine formaldehyde resin
Impregnation of Norway spruce soft wood with melamine formaldehyde (MF) resin under vacuum-pressure process showed promising potential to improve number of properties, such as, dimensional stability and surface hardness. In this study, MF resin impregnated wood was evaluated at different levels of weight percent gain (WPG) compared to untreated one, mainly for dimensional stability and surface hardness. The modified wood, at 22.9 level of WPG possessed increase in dimensional stability in terms of anti-swelling efficiency and surface hardness by 17.5% and 124% over untreated, control. Chemical adherence and/or reaction takes place onto wood cell wall components other than cell lumens, which was proved by vertical density profile (VDP), UV microscopic and scanning electron microscopic (SEM) studies.
In order to study possible mediators of the vascular manifestations of passive cutaneous anaphylaxis (PCA), several arachidonic acid metabolites were injected into guinea-pig skin. SRS-A, LTB4, LTC and LTD increased vascular permeability, responses to LTs being enhanced by PGE2. Mepyramine inhibited responses to histamine, but not those to SRS-A and LTs: the latter were inhibited by the SRS-A antagonist FPL-55712. Both mepyramine and FPL-55712 exert limited inhibitory effects on vascular permeability during PCA. Leukotrienes may contribute towards vascular permeability during PCA.