Handling FR Polyester Fabrics in the Laundry.
Flame retardant textiles are to be found wherever there is a greater need for care and protection. These specialist fabrics help to lessen the risk of fire and to reduce its severity so that major catastrophes can be avoided. Due to these factors, flame retardant textiles are being increasingly used by hospitals and institutions in those areas considered to have a high flammability risk. In particular, hospitals and institutions are using flame retardant materials for curtains and patient bed screens as the use of vertical hanging textiles for these purposes creates a potential danger for initial flame ignition and flame spread from floor to ceiling.
There are many types of flame retardant textiles on the market today which derive their performance features from either chemical finishes on the fabric or inherent fibre properties.
Provided that the flame retardant materials can be conveniently laundered and processed correctly, it is generally considered that inherently flame retardant fabrics are preferable, as they overcome the concerns usually related to the long term durability of coated and impregnated chemical finishes.
Polyester staple fibres and filament yarns have been developed to provide inherently and permanent flame resistant textiles that also possess the general characteristics of normal polyester. These modified FR Polyesters are marketed under a variety of brand names. Polyester is a very strong, elastic fibre which has high abrasion resistance, good durability and exceptional dimensional stability. It is unaffected by dilute or medium concentrated mineral acids and has good resistance to hot or cold dilute alkalis. Polyester produces easy care fabrics that have excellent resistance to light, natural drapability and good crease resistance properties.
Therefore, when the basic polyester properties are combined with a permanent flame retardant the resultant fabrics are an ideal choice for curtains and bed screens.
Permanent flame retardancy is given to FR Polyester by the inclusion of a comonomer containing phosphorous within the framework of the polymer. It is directly linked into the polymer chain and cannot be removed.
FR Polyester textiles are produced in a variety of colours, weights and designs to suit every style and mood and yet all the variety of fabrics comply with the required Australian Standard AS 1530 Part 2 and 3 Building Standard for flammability and also Australian Standard AS3789.9, Textiles for health care facilities and institutions – curtains and patient bed screens – Fabric performance properties..
To provide the best means of laundering FR Polyester fabrics the following care instructions are provided as suggested guidelines on which to develop the most successful processing methods so that the fabric’s characteristics are consistently retained.
Hospital curtains and bed screens have to be laundered and reprocessed on a regular basis, so as to be thermally disinfected and cleaned for aesthetic purposes. It is of paramount importance that all textiles of a ‘special’ nature can be processed successfully through industrial laundry facilities in a manner that is convenient to the laundry and cost effective in both the short and long term.
FR Polyester fabrics can be laundered in a similar manner to hospital uniforms, which are usually manufactured from 65% Polyester/35% Cotton fabrics, and in many instances industrial laundries have already adopted a “uniform wash system” for processing hospital curtains and bed screens. However local consideration needs to be given to ‘drying’ FR Polyester fabrics so as to minimises laundry processing and while still providing the best possible finish for the products being processed.
On receipt of soiled laundry from a hospital or institution the first step is to separate the items according to the degree of soil condition and fabric composition. The FR Polyester fabrics should be separated from any heavy, greasy soiled articles and, where possible, they should be processed together in full loads due to the fabrics particular wash performance and drying characteristics.
This classification process is carried out to save giving the lightly soiled fabrics the heavy soiled wash formulae, and also because the polyester fibres have a particular attraction for all oils and greases. In a mixed soiled load any oil in the washing machine not held in suspension by detergent will be attracted to the polyester fibres and remain there as ‘redeposition’.
Polyester fibres are known as being oleophilic (oil loving) and very susceptible to redeposition, which is one of the most difficult types of soiling to remove. In addition, if FR Polyester is washed with all cotton articles there will be a tendency for the polyester fabric to attract lint and the load may come out linty.
When washing polyester articles it is recommended that the washing machine is underloaded to minimise the problem of creasing. Underloading by up to 25% may be beneficial in an open pocket machine but up to 50% may be necessary in some pocket-type machines.
Overloading of a washing machine can give rise to a form of creasing known as pressure creasing. This is often mistaken for thermal shock creasing with a result that time can be wasted attempting to rectify the problem by paying attention to the cooldown stage. Pressure creasing is characterised by creases extending along the weave direction rather than in a randomised distribution.
The laundering of FR Polyester fabrics also requires the selection of specially formulated detergent compounds. These types of wash chemicals are usually blended from non-ionic or anionic detergents, silicates and phosphates which provide excellent detergency without the high levels of alkalinity usually found in standard wash formulas. In washing there are three things that work together to remove the soil— i.e. water level, water temperature and wash chemicals.
It is important to have a balance between these three items so that the best overall performance can be achieved.
Most hospital and commercial laundries usually wash bed screens and curtains in a uniform wash cycle which has hot wash temperatures of around 60 degrees C. However, to comply with current thermal disinfection guidelines it is necessary to wash at 70 degrees C for a minimum of 10 minutes and for hospital work in particular this criteria needs to be built into the appropriate wash cycle.
Polyester fabrics are strongly susceptible to thermal shock creasing caused by rapid cooling during washing and wrinkles put into the fabric in this way are extremely difficult to remove later, therefore a controlled lowering or cooldown sequence needs to be incorporated into the wash cycle, particularly after the hot wash and during the rinsing stages. When processing polyester fabrics it is essential to cool down the load gradually after a hot wash to a temperature where thermal shock creasing is not likely to occur, and before adding cold rinse water in quantity. Fabric temperatures must be below 60 degrees C before extracting or before cold rinsing occurs.
Cooldown can be achieved in two ways. The preferable method involves slow addition of cold water to the machine with weired overflow to achieve a final temperature of 60 degrees C at a maximum reduction rate of 6 degrees C per minute.
The alternative method involves the slow addition of cold water giving the temperature decrease at the same maximum rate but allowing the dip to rise. Intermediate dumping of liquor to drain may be necessary in this procedure.
After washing the load should be hydroextracted briefly so that the residual moisture content of the fabric is about 30-40%. The duration of high speed extraction must be limited to avoid pressure creasing. One minute extraction at high speed is frequently sufficient to achieve the required residual moisture content.
A suggested wash cycle for processing FR Polyester fabrics is summarised as follows:
|Wash Formula for Trevira C.S. and F.R. Fabrics|
|Operation||Dip||Temperature||Time (min)||Washing Agent|
|5||Hot Wash*||Med||70˚C||10 minimum||Detergent|
|* If bleaching is required to remove stubborn stains then it is recommended that Hydrogen Peroxide is used (1mL per kg) during the Hot Wash stage 5 and the temperature is increased to 80 degrees C. In these instances care should be taken with the subsequent cool-down process.|