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hydrophobicity, oleophobicity, wettability/
hydrophilicity, pilling and static charges, by
hydrolysing polymers without affecting the bulk
properties, having the advantage of being eco-
friendly compared with conventional chemical
treatments (Guebitz and Cavaco-Paulo, 2008),
(Heumann et al, 2006), (Vertommen et al, 2005).
Other authors (Heish and Cram, 1998) confirmed
that the increasing of the hydrophilicity after
modification of polyester with lipases was superior
to the one achieved with conventional chemical
treatments (alkaline treatment: 3N of NaOH during 2
hours).
Our new approach focus on the surface
modification of PET fabrics by enzymatic treatments
using three different enzymes (Texazym PES and
Aspergillus niger, Aspergillus oryzae, respectively),
in order to form new polar groups (carboxyl and
hydroxyl) at the surface, capable to establish
hydrogen bonds with water and capable to improve
surface adhesion. The study was undertaken to
analyze and compare the effect of enzymatic
treatments applied in a textile material (100% PET
fabric), by studying the morphological and chemical
changes at the surface, the mechanical properties
and surface energy, in order to establish whether or
not the material can be functionalized and its surface
adhesion properties can be improved.
2 EXPERIMENTAL
The enzymatic treatment aims to improve the
hydrophilicity without harming the mechanical
properties of the material. For that purpose, it was
investigated a new approach by studying the effect
of the three types of enzymes, esterases and lipases
(Texazym PES sp5, Aspergillus niger and
Aspergillus oryzae), varying the incubation time and
the enzyme concentration.
The chemical modifications were investigated by
measuring the contact angle and the wicking height.
The indirect determination of the formed carboxyl
and hydroxyl groups was measured by staining with
a cationic dye (Methylene Blue) and a reactive dye
(Reactive Black 5), respectively, and by measuring
the surface energy by the Owens-Wendt method.
The surface morphological changes were analyzed
by scanning electron microscopy (SEM).
2.1 Materials
The substrate (textile material) used in this work was
a 100% poly (ethylene terephthalate)
fabric, Batavia
Twill, with the characteristics indicated in Table 1.
The substrate was pre-washed with 1 g/L Plurafac
LF 400, at 50ºC during 60 minutes, with mild
mechanical agitation (25 rpm). Subsequently, the
substrate was rinsed and washed under running
water, followed by a thermofixation at 170ºC during
15 minutes.
2.2 The Enzymes
The enzymes selected for this study, were an
esterase (Texazym PES sp 5 from inoTEX Ltd.) and
two lipases (Aspergillus niger and Aspergillus
oryzae from Sigma). These enzymes were applied
according to the literature reviewed under the
conditions of pH and temperature indicated by the
manufacturer. In Table 2 are presented the principal
characteristics of the enzymes used.
It was studied the action of Texazym PES,
Aspergillus oryzae and Aspergillus niger, applied at
different concentrations (0.06, 0.09, 0.12, 0.15 and
0.18 U) and different incubation times (30, 60, 90
minutes and 24 hours) with a liquor ratio of 1:25.
The enzymatic treatments with Texazym were
performed at 30ºC, using 50 mM of sodium acetate
buffer solution (pH 5.5). The enzymatic treatments
with Aspergillus niger and Aspergillus oryzae were
performed by incubating 2 g of polyester fabric at
45ºC and 40ºC, using 50 mM phosphate buffer (pH
7.0).
Immediately before and after treatments all
samples were placed in a standard atmosphere
(
20 ± 2º C, 65% HR) during 24±2 hours.
Table 1: Fabric characterization.
Characterization Test Method Value
Warp direction
Linear Mass (Tex)
Density
(Yarns/cm)
Diameter (Den)
NP – 4105
NP – EN
1049-2
NP – 3160
48.47
21.4
3.3
Weft direction
Linear Mass (Tex)
Density
(Yarns/cm)
Diameter (Den)
NP – 4105
NP – EN
1049-2
NP – 3160
36.67
32
3.3
Weaving
construction
Mass per area
(g/m
2
)
Composition
NP EN 1700
NP EN 1701
NP EN 1808.
2247 and
2248
Batavia twill
211.65
100%
Polyester
IMPROVING SURFACE ENERGY AND HYDROPHILIZATION OF POLY(ETHYLENE TEREPHTHALATE) BY
ENZYMATIC TREATMENTS
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