Nonwoven is a flat fabric-like material which is not manufactured using weaving or knitting technologies; it is composed of a flat sheet of fibres (e.g. polyester, viscose) bonded together by mechanical, chemical or heat treatment. Nonwoven fabrics can be defined therefore as a particular category of products which does not require the conversion of fibres to yarn in its manufacturing cycle.
The first types of nonwoven fabrics date back to approximately 1930 at the time when some researchers studied a way to produce leather substitutes and reduce textile production costs by getting rid of the costly fibre to yarn conversion and weaving phases.
The success of nonwovens is mainly due to the possibility of providing functional products with significant advantages in terms of cost; a direct consequence of the relative simplicity of their manufacturing processes and their high potential. Nonwovens are mainly used in the “disposable” items sector (bandages, dressings, cleaning materials).
There are numerous manufacturing processes for nonwovens, all of which nonetheless consist in three steps: forming the sheet or base, binding it, post treatments to improve the product.
During the sheet formation phase, the fibres are spun into a flat sheet or web resulting in a semi-finished product with a fibre bonding which is too weak to be used without further manufacturing processes. In the bonding phase of the sheet, the sheets formed in the previous step must be bound in order to obtain a strong bonding.
The most common techniques are:
a) chemical bonding, where bonding is achieved by means of a wetlaid process consisting in the application of a binder to the sheet either by dipping or spraying in order to join the fibres;
b) mechanical bonding where the fibres are mechanically intertwined and entangled;
c) needle punching, which results in very thick soft products e.g. cotton wool for particular applications;
d) thermal bonding, thanks to which process the fibres which form the sheet are welded together using heat treatment. Following this stage, in order to obtain a finished product with particular properties and characteristics, various operations can be carried out including: embossing, printing, coupling with other treatments to influence properties such as porosity, breathability, absorbency, liquid repellence etc.