Plastics surface preparation

Adhesive gluing Difficult to bond plastic, surface preparation very crucial. Proper selection of glue necessary. Consider improved design to avoid the need for gluing or use welding. 

S.3.3 Reinforced plastics. Adhesives that give satisfactory results on the resin matrix alone may also be used to bond reinforced plastics. Surface preparation of reinforced thermosetting plastics consists of abrasion and solvent cleaning. A degree of abrasion is desired so that the reinforcing material is exposed to the adhesive. 

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

Coating plastics, metals, etc. steps generally involve surface preparation, preheating substrate, powder applications, and post-heating. 

Avseenko et al. (2001) immobilized antigens onto aluminum-coated Mylar films by electrospray (ES) deposition. Various surface modifications of the metallized films were studied to determine their abilities to enhance sensitivity. The plastic surfaces were firsf cleaned by plasma discharge treatment, followed by coating with proteins (BSA and casein) or polymers such as poly (methyl methacrylate) or oxidized dextran, or they were exposed to dichlorodimethyl silane to create hydrophobic surfaces. Protein antigen was prepared in 10-fold excess sucrose and sprayed onto the surfaces to form arrays with spot diameters between 7 and 15 pm containing 1 to 4 pg protein. 

Figure 3.29. Photographic representation of a blow-fill-seal machine, which can be particularly useful in the aseptic filling of liquid products (refer to text for details). While used fairly extensively in facilities manufacturing some traditional parenteral products, this system has not yet found application in biopharmaceutical manufacture. This is due mainly to the fact that many biopharmaceutical preparations are sold not in liquid, but in freeze-dried format. Also, some proteins display a tendancy to adsorb onto plastic surfaces. Photo courtesy of Rommelag a.g., Switzerland...

Research Focus Preparation of amphiphilic block copolymers to increase the wettability and printability of a plastic surface containing thermoplastic blends. Originality Thermoplastics containing amphiphilic block copolymers as antistatic... 

Surface Preparation of the Substrate. This is extremely important for all methods of paint and coatings application. The failure of a paint system is often due not to the paint itself, but because of a failure in surface preparation. For example, an anticorrosive paint applied to a rusty surface will not be effective if the rust falls off taking the new paint with it. For wood and plastic surfaces, old paint or a weathered surface layer may have to be removed. For older metal objects, the removal of corrosion is often required. Sandblasting is one method to remove both the old paint and any corrosion. For new metal objects, a phosphate or chromate layer is often chemically bonded to the metal to provide a surface to which a coating can easily adhere. 

Values from tables of friction coefficients always have to be used with caution, since the experimental results not only depend on the materials but also on surface preparation, which is often not well characterized. In the case of plastic deformation, the static coefficient of friction may depend on contact time. Creeping motion due to thermally activated processes leads to an increase in the true contact area and hence the friction coefficient with time. This can often be described by a logarithmic time dependence... 

The original edition of Plastics Surface and Finish was an attempt to review progress towards this objective—a book of some 242 pages (not including the Index) published in London by Butterworths in 1971 and prepared jointly by Dr S. H. Pinner and the present editor (editorial credit was settled by placing the surnames in alphabetical order). It contained contributed chapters as follows ... 

Often, one must consider the time, trouble, and expense that may be necessary to use an adhesive. For example, certain plastics may require expensive surface preparation processes to allow the adhesive to wet the surface. Applications requiring high-temperature service conditions may require an adhesive that necessitates an elevated-temperature cure over a prolonged period. 

As with metal substrates, the effects of plastic surface treatments decrease with time, so it is important to carry out the priming or bonding as soon as possible after surface preparation. The surface preparation methods suggested in App. F are recommended for conventional adhesive bonding. Greater care must be taken in cleaning thermoplastics than... 

Epoxy and nitrile-phenolic adhesives have been used to bond polyolefin plastics after plasma surface preparation. Shear strengths in excess of 3000 psi have been reported on... 

TABLE F2 Surface Preparation Methods for Plastic Substrates... 

TWO SEPARATE ALTERED or damaged layers classically have been recognized on metal surfaces formed by cutting- or polishing-type processes namely, an amorphous-like "Beilby" layer and a plastically deformed layer. Modern work indicates that the Beiiby layer is not, in fact, formed by the common important methods of surface preparation but that a deformed layer always is. The detailed structure of this layer is reviewed. Some consideration is also given to residual elastic stresses, surface topography, and embedded abrasive. 

The subject is complicated by the very wide diversity of processes that may conceivably be used for surface preparation. Attention will be confined here to processes in which the new surface is machined by cutting, particularly by operations such as grinding and abrading which involve the use of abrasives, or is polished by methods in which the surface is worked against a fine abrasive. It has been accepted in the past that the possibility of the presence of two physically distinct layers must be recognized on surfaces produced by these processes namely, an outer layer known as the "Beilby Layer" and a layer of material which differs from the unaffected substrate only in that it has been plastically deformed. R will be necessary to consider these two layers separately. 

The preparation of a suspension of leucocytes from solid tissues is comparatively straightforward (Section 3.3.). The preparation of other cells from solid tissues is more difficult the procedures depend on the tissue and the type of cell required (1). Most methods involve the use of proteolytic enzymes that may destroy surface antigens. Frequently, better results are obtained if the cells are put in short-term culture. Section 3.4. gives a method for preparing cells grown on a plastic surface. 

Use Chemical intermediate in preparation of resins, plasticizers, surface-active agents. 

---