There are some differences between stain protectors based on fluoropolymers in comparison with those based on either silicone or hydrocarbons. The most important difference is the oil repelling property.
A stain protector works on the principle of reducing the critical surface tension of the surface that is treated with it. In contrast a wetting agent will reduce the surface tension of the liquid which contains said wetting agent so that it may wet the surface with a higher critical surface tension.
The protection based on fluoropolymer creates a kind of barrier by reducing the critical surface tension: liquids may no longer wet the surface well and cannot spread out through wicking. In addition dry dirt will not adhere as well and is thereby removed easier.
It should be noted at this point that a stain protector is not able to seal a porous fibre or textile completely.
As long as capillary action is the only driving force the stain protector will prevent penetration into the textile or fibre and its spreading by wicking (the droplet effect). As soon as the spill occurs with force(such as dropping from a height, for example), is water-based, and is thereby pushed into the material, however, the stain protector will prevent deeper penetration and thereby facilitates removal but it will not have the droplet effect. Oily substances may actually penetrate more deeply, as oil has a lower surface tension and therefore will manage to overcome the barrier introduced by the stain protector.
This is evident from Table 1, which lists the critical surface tension for a number of materials and liquids. In general one can say that a difference in critical surface tension of about 18 dyne/cm will result in repellant action.
Table 1 - Critical surface tensions for a number of surfaces and liquids
Based on this value Table 1 illustrates that the critical surface tension of polypropylene is almost identical to those of the listed oils. Thus oils will wet polypropylene easier and absorb at the surface more readily.
If polypropylene is treated with a fluoropolymer then the critical surface tension is reduced, the difference between surface and liquid changes and oils will also be repelled from the surface.
If the polypropylene is treated with a silicone or hydrocarbon based product then the difference in critical surface tensions is only approximately 6 dynes/cm. A repelling effect does not occur.
One also has to differentiate between fluoropolymers depending on the area of application: products that have been formulated for carpets, like our Carpet Stain Protector, for example, lean toward soil repellency in addition to stain protection, as carpets are faced not only with the problem of staining but also soiling, which actually tends to play the more important role.
The appropriate fluoropolymer helps by reducing the adherence of soil to the fibre and thereby making it easier to remove the dirt.
Products for upholstery, such as our All Fabric Stain Protector, for example, are formulated with a stronger focus on stain protection, water- and oil-based, as upholstery tends to have more problems with staining in general, and oily stains in specific.
Considering the effectiveness of fluoropolymer-based stain protectors the most important factor is the concentration. In general 0.1 to 0.4% fluoropolymer concentration are sufficient to impart stain protecting properties on fibre or textile.
As most products on the market today are water-based the temptation to dilute is there. This should only be done if the directions for use on label or in product data sheet explicitly say so.
At this point it should be noted that most products offered on the market today are formulated as ready-to-use solutions.
A further influencing factor is the structure of the fibres. A smooth, even surface is ideal. A loop-pile is thereby better equipped to handle a stain protector than a velours is with the same treatment.
In order to obtain the best result the fibre/textile should be as clean as possible. Any residues from soil/dirt or cleaning product will have a negative influence on the stain protection.
When applying the stain protector, especially on a velours, the product should be applied with a fine sprayer and brushed into the pile afterwards in order to get the maximum effectiveness.
The best result from a stain protector based on fluoropolymer is obtained when the chains of fluoropolymer (molecules) are oriented towards the outside, that is towards the surface. This may be accomplished best when the material is fabricated, as here high temperatures (130°C) may be achieved without problems. This process is not realistic when treating an installed carpet or upholstery on site. For this reason the stain protective equipment from the manufacturer will always be more effective.