By Ralf H. Dahm, Derek M. Brewis
Fluorinated polymers have a couple of very important houses corresponding to first-class chemical resistance. despite the fact that, they're frequently tough to bond with no pretreatment. There are exceptions and untreated poly(vinylidene fluoride), for instance, will be effectively bonded with an amine-cured epoxide. the best ways to pretreat totally fluorinated polymers have been constructed within the Nineteen Fifties. a lot paintings, specifically on electrochemical and plasma remedies, has on account that been conducted yet up to now those haven't proved as potent because the early tools. partly fluorinated polymers could be handled like polyolefins, for instance, flame, and plasma remedies are very powerful. Aqueous and alcoholic options of team I hydroxides also are very potent. Fluoropolymers provides a mixture of houses together with hot temperature resistance, very good resistance to many chemical compounds and ultraviolet (UV) radiation, fireplace resistance and coffee friction. Fluoropolymers are quite dear and they're often utilized in specialized functions corresponding to linings for chemical plant, spacecraft coatings which are immune to atomic oxygen, fire-resistant coatings for cables, and naturally, non-stick features. There are greater than twenty diverse fluoropolymers which are commercially to be had. strong adhesion is needed in a couple of applied sciences related to fluoropolymers together with adhesive bonding, portray, printing, metallisation (via vacuum or resolution) and composite construction. despite the fact that, totally fluorinated polymers reminiscent of PTFE and FEP are notoriously tricky to stick to, whereas partly fluorinated polymers similar to PVDF and PVF can cause difficulties looking on the situations. to accomplish a passable point of adhesion, it's always essential to perform a pretreatment with either absolutely and partly fluorinated polymers. during this evaluation the foundations of adhesion are thought of first (Section 2). options that experience significantly elevated our knowing of adhesion to fluoropolymers are defined in part three. instances the place stable adhesion is completed and not using a pretreatment are tested in part four. despite the fact that, as pretreatments tend to be had to get the necessary point of adhesion, this evaluate is especially desirous about the big variety of equipment to be had to pretreat fluoropolymers (Section 5). A normal dialogue and conclusions keep on with. This Rapra overview document includes a concise, professional assessment, supported by way of an intensive bibliography compiled from the Polymer Library concerning adhesion to fluoropolymers. This bibliography presents additional info in this topical box. This overview may be of curiosity either to those that already use fluoropolymers and those that are contemplating utilizing them.
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Additional info for Adhesion to Fluoropolymers
Some chemical changes caused by the different plasmas under a particular set of conditions are given in Table 11. Kasemura and co-workers (266) used a domestic microwave oven with an output of 560 W at 2450 MHz operating at a pressure of 26 Pa to pretreat PTFE and FEP. As the pressure of the air was decreased from 133 to 26 Pa, the efficiency of the treatment increased as measured by lower contact angles with various liquids. 064 — 20 Adhesion to Fluoropolymers a 45 second treatment with argon.
Kanoufi, C. Sella, A. Thiebault and L. Thonin, Chemistry: A European Journal, 2000, 6, 5, 820. H. J. M. J. W. Allen, Applied Science Publishers, London, UK. 215. Conclusions • Sodium in liquid ammonia and sodium naphthalenide in a suitable solvent are the most effective pretreatments for fully fluorinated polymers. J. M. H. D. J. Hoy, Journal of Adhesion, 1981, 13, 67. J. Griesser, Y. E. R. M. Mau, Langmuir, 1991, 7, 11, 2484. LF low frequency m metre mm millimetre ASTM D2578, Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films, 2004.
There are many methods that could be used to enhance such polymers but the two usually used commercially are sodium in liquid ammonia and sodium naphthalenide in an aprotic solvent. These two methods are both very effective but are undesirable from the environmental viewpoint. The use of sodium and liquid ammonia is clearly hazardous during the treatment stage. Sodium naphthalenide solutions are less hazardous and relatively stable proprietary products may be purchased. However, these are expensive, and when the treated polymer is washed with water naphthalene is liberated.