Surface modification, fluoropolymer

Surface modification of fluoropolymers either by ionizing radiation (gamma radiation or electron beam radiation) [20,21] or by chemical reactions [22], introduces reactive sites for additional chemical reactions or improves wear [20]. 

There are two types of adhesives by which fluoropolymers bond contact adhesives and bonding adhesives. The distinction between these two adhesives is that contact adhesives can be applied without modification of the surface of the plastic, while bonding adhesives require surface modification. 

Brewis, D. M., Loughborough University, UK, Surface Modification of Fluoropolymers for Adhesion, paper presented at the Fluoropolymers Conf (1992)... 

Kang ET, Zhang Y. Surface modification of fluoropolymers via molecular design. Adv Mater 2000 12(20) 1481-94. 

Surface modification of the polymeric membranes via molecular design is one of the most versatile means to improve the surface properties without affecting bulk properties. Surface modification of fluoropolymer membranes, especially for fully fluorinated polymer membranes, such as PTFE membranes, has been of particular interest, due to their physical and chemical inertness. Surface modification of fluoropolymer membranes can be classified into two categories surface coating and surface grafting. 

Surface modification and functionalization of fluoropolymer membranes can be achieved via two main approaches, viz., (a) the grafting from and (b) the grafting to approaches (Scheme 8.5). The grafting from method incorporates active sites... 

It is necessary to modify the surface of fluoropolymers to obtain stronger adhesive bonds. Modification or surface treatment alters the structure of the polymer at the surface enabling formation of true adhesive bonds. Mechanical abrasion imparts little improvement and chemical etching is required. Chemical resistance of perhalogenated polymers such as PTFE, PFA, FEP, and PCTFE mandates the use of highly potent agents. 

Fluoropolymers crosslinked with polyamines are particularly suitable for use in the manufacture of tubing employed as aircraft hoses, to carry fuel lubricants at high temperature and under high pressure, and in the aircraft construction industry. They can also be used as strong adhesive joints without prior surface modification. 

Brewis DM. Surface modification of fiuoropol-ymers for adhesion. Paper presented at the Fluoropolymers Conference. UK Loughborough University 1992. 

Some atmospheric plasma treatments allow in-line surface modification of almost any wire insulation material. Examples include polyamides, polyesters, and the fluoropolymers most difficult to treat. A treated surface can then accept inkjet printing for marking purposes. Table 5.13 shows a comparison of the marking durability on ethylene tetrafluoro-ethylene copolymer (ETFE) and fluorinated ethylene propylene copolymer (FEP) for untreated (U), flame treated (FI), and plasma treated (PI) conditions. Some wires have been cross-linked by irradiation (IR) to enhance cut-through resistance of the insulation. Wire suppliers have been identified in each case and all ink was UV curable. 

Thermoplastic materials often have a lower surface energy than do thermosetting materials. Thus, physical or chemical modification of the surface is necessary to achieve acceptable bonding. This is especially true of the crystalline thermoplastics such as polyolefins, linear polyesters, and fluoropolymers. Methods used to increase the surface energy and improve wettability and adhesion include... 

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