Plastics, surface treatment

For some plastics, surface treatments were necessary—for example, chromic acid treatment for polypropylene. When fillers were present in the plastics the results with cyanoacrylates often were better (this was apparent in particular with polyethylene). 

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... 

Adsorption, where the preservative attaches itself to the surface of a plastic, tends to vary according to the type of plastic, constituents in the plastic, surface treatment, surface area of the plastic. Adsorption has been found with most mercurials, including Thiomersal, benzalkonium chloride and bromide, etc. Small amounts of chlorhexidine, benzoic acid and hydroxybenzoates have also had losses reported for certain plastics. 

Cell morphology of foamed PVC depends on concentration of a plasticizer, surface treatment of filler and foaming time and temperature. High concentrations of plasticizers produced poly disperse cell structure. Polyester plasticizer blends are useful for production of heat-shrinkable film. Plasticizer migration from geomembranes causes membrane shrinkage. ... 

As with metallic substrates, the effects of plastic surface treatments decrease with time. It is necessary to prime or bond soon after the surfaces are treated. Some surface treatments, such as plasma, have a long effective shelf life (days to weeks) between treatment and bonding. However, some treating processes, such as electrical discharge and flame treating, wiU become less effective the longer the time between surface preparation and bonding. 

Mineral fillers require surface modification when used as reinforcements in plastics. Surface treatment improves mechanical strength and... 

Glogauer [34] has reported on how an innovative atmospheric-pressure plasma technique allows in-line rubber and plastic surface treatment processes to become fully automated with total process control. The new process is claimed to achieve microfine cleaning, high surface activation and nanocoating in a more cost-effective and environmentally friendly way than traditional plasma activation techniques. 

Verein Deutscher Ingenieure (VDI), Verband der Elektrotechnik Elektronik Informationstechnik (VDE) Plastic surface treatment in precision engineering - Survey. 

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. 

Corrosion. Ammonium bifluoride dissolves in aqueous solutions to yield the acidic bifluoride ion the pH of a 5% solution is 3.5. In most cases, NH4HF2 solutions react readily with surface oxide coatings on metals thus NH4HF2 is used in pickling solutions (see Metal surface treatments). Many plastics, such as polyethylene, polypropylene, unplasticized PVC, and carbon brick, are resistant to attack by ammonium bifluoride. 

Plastic packagiag materials are thermoplastic, ie, reversibly fluid at high temperatures and soHd at ambient temperatures. These materials may be modified by copolymerization, additives ia the blead, aHoyiag, and surface treatment and coating. Properties of principal plastic packagiag materials are givea ia Table 1. 

Exact si2ing of mica products coupled with surface treatment procedures have led to a greater use for wet ground mica in plastic compositions, particularly automobile bodies. These quahty products demand a high dollar value. 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

Inhibited grades of 1,1,1-trichloroethane are used in hundreds of different industrial cleaning appHcations. 1,1,1-Trichloroethane is preferred over trichloroethylene or tetrachloroethylene because of its lower toxicity. Additional advantages of 1,1,1-trichloroethane include optimum solvency, good evaporation rate, and no fire or flash point as determined by standard test methods. Common uses include cleaning of electrical equipment, motors, electronic components and instmments, missile hardware, paint masks, photographic film, printed ckcuit boards, and various metal and certain plastic components during manufacture (see Metal surface treatments). 

Inorganic waste with metals from metal treatment and the coating of metals non-ferrous hydro-metallurgy Wastes from shaping and surface treatment of metals and plastics Oil wastes (except edible oils, 0500 and 1200)... 

If corona, plasma, or flame treatment is chosen as the surface treatment, it is important to bond quickly after the treatment. Waiting several hours will reduce the effectiveness of the treatment. In some cases, attempts to bond 24 h after the treatment can give the same poor bonding results as if the plastic had never been surface treated. If surface oxidation is not possible, priming the surface with a chlorinated polyethylene primer is a second choice [95]. 

Glass fibers and most other reinforcements require special surface treatment to ensure the bonding and compatibility of the fibers to the plastic in order to maximize performances. Treatments are also used to protect individual filaments during handling and processing (7,14). 

The CRC-Elsevier materials selector , 2nd edition, N.A. Waterman, and M.E Ashby CRC Press (1996) ISBN 0412615509. (Now, also available on CD-ROM). Basic reference work. Three-volume compilation of data for all materials includes selection and design guide. The Materials Selector is the most comprehensive and up-to-date comparative information system on engineering materials and related methods of component manufacture. It contains information on the properties, performance and processability of metals, plastics, ceramics, composites, surface treatments and the characteristics and comparative economics of the manufacturing routes which convert these materials into engineering components and products. 

Wastes from shaping and surface treatment of metals and plastics... 

---