Annals of Warsaw University of Life Sciences - SGGW

within the adhesive network It is assumed that in the first grade of degradation N-methylol
groups are dissociated at the end of the chain, and later formaldehyde is released from inside
of the structure of macromolecule.
Perforator method is most often used laboratory method for determination of released
formaldehyde. ROFFAEL et al. (2010) tested samples glued with UF adhesive after
conditioning in the environment with different values humidity. Systematic investigations into
the influence of moisture content on the perforator value showed that the relation between
moisture content and perforator values can be represented by a straight line. The emission in
the chamber rose with increasing (measured uncorrected) perforator value.
MATERIAL AND METHODS
In experimental work we tested UF and MUF adhesives and hardener R-60. Natural
polymers were added into adhesives in the form of skin collagen hydrolysate (HC). The
hydrolysate was a liquid: collagen amount 26 %, solid content 43 %, pH = 5.2. Hardener was
modified with activator (AG) based on glutaraldehyde (VIPO a.s.). Activator was added into
hardener in amount 1 %, 3 %, or 5 %.
Plywood was pressed from beech or birch veneers; adhesive spread 160 g.m -2 ,
temperature 105 °C (UF), 130 °C (MUF), specific pressure 1.8 MPa, pressing time 5 minutes.
Formaldehyde content determined by FESYP method according to STN EN 120 standard, dry
mater content according to STN EN 322 standard, formaldehyde emission from glued boards
by chamber method according to STN 49 0030 and EN 717-1.
RESULTS AND DISCUSSION
Formaldehyde content in plywood glued with UF and MUF adhesives with modified
hardener (Hr1 and Hr3) are presented in table 1.
Tab. 1 Formaldehyde content in plywood glued with UF and MUF adhesives with AG
Adhesive mixture Requirement of the
standard [mg/100g a.d.]
fd content
[mg/100g a.d.]
fd content
relative value [%]
UF + HrR 2.08 100
UF + Hr1 1.90 91
UF + Hr3 8,0
1.98 95
MUF + Hr1 3.14 -
MUF + Hr3
3.89 -
From the obtained results, we can see that AG influences the quality of glued joint.
Addition of 1 % AG resulted in decrease of formaldehyde content by 9 %, the addition 3 %
AG in decrease by 5 %. The situation of MUF adhesives is very similar to UF adhesives;
lower content of AG caused the lower content of formaldehyde.
Further experiments were aimed at research on the influence of collagen hydrolysate
on the formaldehyde content in plywood. HC was added into adhesive mixture in the amount
of 5 %. The results are given in table 2.
Tab. 2 Formaldehyde content in plywood glued with UF adhesive with AG and HC
Adhesive
mixture
Requirement of the
standard [mg/100g a.d.]
fd content
[mg/100g a.d.]
fd content –
relative value [%]
UF+ HrR 2.08 100
UF +Hr1 + 5% HC 1.78 85
UF +Hr3 + 5% HC 8,0
1.54 74
UF +Hr5 + 5% HC
1.89 91
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