kinetic response of thermosetting adhesive systems to heat

Activation Energy Index
1,00
0,95
0,90
0,85
ABES
DSC
Gelation time
(2,09) (1,46)
UF#2 UF#3 UFm#4
UFm#5
Adhesive System
Figure 6. Ratios of activation energy of the adhesive systems derived from DSC, ABES
and gelation time methods on a basis of reactivities for adhesive #2.
Composites testing system (ComTes)
Design and testing procedure:- ABES has been modified in order to enable the combined
effects of adhesive and fiber network characteristics on bonding of wood-based composite
materials to be explored. Resinated (but uncured) miniature fiber discs (17.5 mm in diameter and
9-mm in thickness) can be pressed under controlled conditions of temperature and tested in shear
mode perpendicular to the forming direction. For this purpose, after forming, two samples are
pressed and tested simultaneously. Aspects of the system are shown as Figure. 7. Two circular
temperature-controlled pressing heads (�) act uniaxially on the outer surfaces of the samples,
while and one angular block (�) in the center with inserted cartridge heaters are used to transfer
heat and load onto the samples surfaces. To impede passive spreading of the samples, the fiber
discs are peripherally constrained by PTFE (Teflon) cylinders (�) that are pneumatically driven
back prior to testing. Small aluminum discs are glued simultaneously onto the discs’ surfaces
with cyanoacrylate adhesive to transfer shear forces from the shear bar (�) into the samples.
Usually, the samples fail in the core layer of the 3 mm thick samples because of the slightly
delayed temperature increase in this plane.
1
1
2
fiber discs
Figure 7 - Overview (left) and detail (right) of the Composites Testing System.
4
4
3