Water and Oil Repellent Finishing of
Textiles by UV Curing: Evaluation of the
Influence of Scaled-Up Process Parameters
112
Franco Ferrero ,*, Monica Periolatto and Lorenzo Tempestini
1 Department of Applied Science and Technology,
Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy; [email protected]
2 Jersey Mode Spa, Via delle Fonti 384, 59100 Prato, Italy; [email protected]
* Correspondence: [email protected]; Tel.: +39-011-090-4630
Abstract: In this work, various textile fabrics were coated with silicone and fluorocarbon-based
resins by photo-curing using ultraviolet irradiation. A great number of large fabric samples were
impregnated by padding with commercial finishing agents and then irradiated in air with a high
power, semi-industrial UV source. The add-on of various finishing agents was kept low to reduce the
treatment cost. White and dyed samples of different textile composition were treated and evaluated
in terms of conferred repellency, yellowing, or color changes. Most relevant process parameters
were investigated, utilizing the thermal process normally adopted at industrial level as reference.
The results were statistically evaluated by ANOVA using Minitab 16 software, in order to identify the
most influential parameters and to evaluate the real possibility of replacing the thermal treatment
with UV curing.
Keywords: cotton fabric; viscose fabric; coating; UV curing; water repellency; oil repellency
Introduction
Water and oil repellency are among the
most common functional properties
necessary for protective clothing.
These properties can be conferred by
the modification of the surface energy
of textile fibers, possibly confined to a
thin surface layer, so that the bulk
properties of the fabric, such as me-
chanical strength, flexibility, breathabil-
ity, and softness remain uncompro-
mised [1,2].
The modification routes should meet
the criteria of green chemistry as much
as possible. In particular, the use of
harmless solvents and non-toxic chem-
icals should be a characteristic of the
process. This principle, in agreement
with the ecological orientation of indus-
trial textile chemistry, limits in a signif-
icant way the number of viable strate-
gies and reactions. Among them, pho-tografting by UV light combines the
inherent benefits of photochemical ini-
tiation, namely a fast, versatile, effi-
cient process and the advantage of a
surface grafting that does not modify
the bulk properties nor degrade the fi-
ber structure.
Grafting has advantages over other
modification methods in several ways,
including easy and controllable intro-
duction of a high density of graft chains
with exact localization of graft sites on
the fabric surface. Furthermore, cova-
lent attachment of graft chains onto a
textile surface ensures the long-term
chemical stability of introduced chains.
This is in contrast to what may be as-
pected for physical coating on polymer
chains obtained by thermal treatment.
The use of UV irradiation appears to
be an excellent method for surface
grafting of functional monomers on tex-
tile fibers. Photochemically-produced
NCM-APRIL 2020
67triplet states of carbonyl compounds
of a suitable photoinitiator can abstract
hydrogen atoms from almost all poly-
meric materials (such as textile fibers)
so that graft polymerization may be ini-
tiated [3,4]. Moreover, when UV irradi-
ation is applied, high concentrations of
active species can be produced local-
ly at the interface between a textile fi-
ber and the monomer solution contain-
ing the photoinitiator, with the conse-
quence of a high yield for the process.
The mechanism of UV-initiated poly-
meric grafting and the grafting process
are shown in Figures 1 and 2, respec-
tively.
Besides the well-known advantages of
UV curing (space saving, easy instal-
lation of equipment, reduced waste,
high speed of treatment) [5], this pro-
cess consumes only about 25% of the
energy required by a conventional ther-
mal-based system using a fuel-fired