ALPATEC MG 2.1 Bedienungsanleitung PDF herunterladen (Seite 6)

UNITEX nr. 1 - 2014

Eco-efﬁcient hybrid coatings for

durable textile applications by UV curing -

Hybritex

F. Goethals

, K. Eunger

, S. De Vrieze

, M. Vanneste

, A. Schumann

, A. Wypkema

Introduction

UV curing is a photochemical process that can be

applied to cure inks, adhesives and coatings.

Similar

to thermal curing the resins are cross-linked, resulting

in a xed and polymerized lm (gure 1). However,

UV curing offers some major advantages over thermal

curing. For one, UV curing is very fast and will therefore

signicantly reduce the production time. Secondly, UV

formulations are either solvent-free or water-based,

resulting in a very low VOC emission. UV curing

systems also require less energy and space compared

to large and high energy consuming thermal ovens.

This makes UV curing a sustainable and eco-friendly

curing technology.

Figure 1: cross-linking of oligomers by UV radiation

To be UV curable, the formulations must contain

suitable resins and a photo-initiator to initiate the

polymerization reaction. Monomers, viscosity modiers

and functional additives can be added, allowing to

modify and tailor the coatings.

By adding functional additives, properties like ame

retardancy, hydrophobicity, abrasion resistance or UV

stability can be obtained.

Sol-gel systems are interesting additives to give added

value to UV coatings, especially towards abrasion

resistance. Traditional sol-gel systems are metal oxide

based (mostly silicon or titanium).

The main advantages of sol-gel systems are the ease

to functionalise them. This means that they could

also possess antibacterial, ame retardant, water,

oil and soil repellent properties. The combination of

functionalized inorganic sol-gel systems with organic

UV curable resins results into so-called hybrid systems.

Applications for UV curing in the textile industry

UV curing is already well-known and frequently applied

in many industrial branches such as the graphic sector

and the wood sector. However in textile industry, this

technology is not widely adapted yet. One of the

reasons is that UV coatings were initially developed

as hard, protective coatings which were as such not

suitable for application as exible textile coatings.

As UV resin manufacturers are also looking for new

markets, they are developing UV curable resins for

exible substrates. As a result, resins are available on

the market offering interesting opportunities for the

textile industry. Using viscosity modiers and diluting

agents (like monomers) formulations for both coating

and nishing can be developed.

In this paper, we present results of a study aimed

at developing UV formulations containing sol-gel

additives for textile substrates. High- and low-viscosity

formulations were prepared and these were applied on

polyester fabrics by knife-over-roll coating and pad-

bath nishing. After UV curing the inuence of the

coatings and nishes on the abrasion resistance was

tested and evaluated.

High-viscosity formulations – textile coatings

Figure 2: set-up for knife-over-roll coating of fabric samples

High-viscosity formulations, suitable for fabric coating

by knife-over-roll (gure 2), can be either 100% or

water-based systems. 100% systems are solvent-free

and usually need to be diluted with reactive monomers

to obtain the right viscosity. Water-based formulations

are often too low in viscosity and a thickening agent

needs to be added. After application, water-based

coatings need to be dried before UV curing to remove

the water (e.g. by thermal heating or IR radiation).

It was found that the product Ebecryl 210 (urethane

acrylate, Allnex) is a good 100% binder for coating

polyester fabrics. To this formulation, two different

sol-gel systems (provided by Devan Chemicals) were

added in different concentrations. After coating, full

curing was achieved by illuminating the fabrics for 4s

under a Hg UV lamp (gure 3).

Figure 3: set-up for UV curing of fabric samples

The abrasion resistance was tested by a modied EN

530-2 test. The coatings were sandpapered with type

F02 paper stopping after 500 cycles. The reduction

in weight was determined for the different coatings

(gure 4).

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