Page 57 - Kutnar, Andreja, et al., eds., 2015. Proceedings of the 1st COST Action FP1307 International Conference - Life Cycle Assessment, EPDs, and modified wood. University of Primorska Press, Koper.

dy
of
interactions
between
PVAC
adhesives
and
wood
after
thermo-­‐

mechanical
(TM)
modification

Tomasz
Krystofiak1,
Barbara
Lis1,
Monika
Muszyńska1

1
Poznan
University
of
Live
Sciences,
Faculty
of
Wood
Technology,
Department
of
Wood

Based
Materials,
Division
of
Gluing
and
Finishing
of
Wood,
Wojska
Polskiego
St.38/42,

60-­‐627
Poznań,
Poland,
email:
tomkrys@up.poznan.pl;
blis@up.poznan.pl,

monika.muszynska@up.poznan.pl

Keywords:
veneer,
PVAC
adhesive,
densification,
wettability,
work
of
adhesion

Veneers
are
one
of
the
main
decorative
materials
used
in
the
furniture
industry
and
interior

design.
These
veneers
can
be
enhanced
using
modification
techniques
to
create
modified
veneers

characterized
by
improved
dimensional
stability
and
interesting
colour
schemes
affecting
the

visual
qualities
(Bekhta
et
al.
2014).
One
of
these
techniques
is
thermo-­‐mechanical
(TM)

modification
(Kutnar
and
Šernek
2007).
Industrial
experience
shows
that
TM
modification
has
an

impact
on
the
process
of
edge
veneering
and
formation
of
the
glue
lines
affecting
their

relationship:
substrate-­‐adhesive-­‐veneer.
The
phenomenon
of
wettability
plays
an
important
role

in
the
technological
process
associated
with
creating
glue
connections.
For
evaluation
this

parameter
the
value
of
the
contact
angle
(Θ)
is
commonly
used.
Contact
angle
is
an
important

parameter
required
for
the
analysis
of
phenomena
occurring
at
the
border
of
contact
veneer-­‐
adhesive-­‐on
the
basis
of
Young-­‐Dupré
equation
(Bekhta
et
al.
2015;
Liptáková
and
Paprzycki
1983).

In
this
work
tests
results
of
the
impact
of
thermo-­‐mechanical
processing
parameters
on
the

formation
the
wettability
of
beech
veneer
(Fagus
sylvatica
L.)
and
pine
veneer
(Pinus
sylvestris
L.)

and
indicators
determined
based
on
the
adsorption
theory
of
surface
interactions
such
as
surface

free
energy
(γs)
and
work
of
adhesion
(Wa)
is
presented.

Rotary
cut
veneer
sheets
of
pine
wood
with
dimensions
of
300
mm
by
300
mm
by
1.5
mm
and

with
MC
of
5
%
were
chosen
for
the
experiments.
Tangential
sheets
of
veneer
have
been
cut
in

150
mm
by
100
mm
rectangular
pieces
for
TM
densification
process
and
subsequent

measurements.
Each
veneer
was
thermo-­‐mechanically
densified
between
the
smooth
and

carefully
cleaned
heated
plates
of
a
laboratory
press
at
temperatures
of
150,
180,
and
210°C
and

pressure
of
3
MPa.
Samples
were
densified
for
3
minutes.
For
experiments
three
commercial

unmodified
PVAC
adhesives,
based
on
EVA
copolymers
and
catalysed
with
isocyanates
(EPI),
were

used. For all tests adhesive
was
applied
with
the
applicator
on
the
modified
surface
of
veneers
at

thickness
of
layers
of
120
μm.
The
dynamic
Θ
angle
of
unmodified
veneers
and
TM
sample
veneers

were
measured
with
PG-­‐3
goniometer
using
distilled
water
as
the
wetting
liquid.
A
drop
of
water

with
a
volume
of
3.5
ml
was
applied
on
veneers
by
integrated
micro-­‐dispensing
pump.
After
60

seconds
(s)
of
contact
with
the
substrate,
the
camera
recorded
its
behaviour.
The
Θ
angle,
the
drop

volume,
and
the
diameter
of
the
base
were
measured.
The
measurements
and
theoretical
formulas

45