THE LDPE RESIN-CASTING METHOD APPLIED TO VESSEL CHARACTERISATION

Abstract

Low-density polyethylene (LDPE) was used as a casting medium to study vessel attributes. The LDPE had a low crystallinity and melted around 102 °C. The glass transition point was very low (-20 °C) in comparison to polystyrene (105 °C). The viscosity decreased exponentially as the temperature was raised. Dry sample blocks of selected hardwoods, fixed in tubes and previously heated, were impregnated with melted LDPE under vacuum or under compression. After the removal of cell-wall materials, the resin casts obtained almost entirely consisted of vessels clearly showing threedimensional arrangement. These casts were dissected with a thin steel knife for SEM observation. Vessel-casts were usually not accompanied by casts of vasicentric elements. Resin-casts of fibres, tracheids and parenchyma cells were observed only near the surface of the blocks. Cell wall sculpturing such as pits and helical thickenings were observed in detail. The depth of LDPE drawn into vessel lumina depended on the time of evacuation and diameter of vessels.