Solvent wiping

The other problem that can occur with metals is the presence of various machine oils on the surface, such as might be used in the automotive area. Oil serves as a low surface energy barrier to adhesion, in most instances. Abrading and solvent wipe are recommended or else degreasing. Removing the surface oil is... 

Solvent Wipe with MEK (Methyl Ethyl Wipe with MEK and Duralace... 

The application of surface treatments to mbbers should produce improved wettability, creation of polar moieties able to react with the adhesive, cracks and heterogeneities should be formed to facilitate the mechanical interlocking with the adhesive, and an efficient removal of antiadherend moieties (zinc stearate, paraffin wax, and processing oils) have to be reached. Several types of surface preparation involving solvent wiping, mechanical and chemical treatments, and primers have been proposed to improve the adhesion of vulcanized SBR soles. However, chlorination with solutions of trichloroisocyanuric acid (TCI) in different solvents is by far the most common surface preparation for mbbers. 

Solvent wiping. Rubbers tend to swell by application of solvents and the mechanical interlocking of the adhesive is favored. Although chlorinated hydrocarbon solvents are the most effective, they are toxic and cannot be used toluene and ketones are currently the most common solvents. The treatment with solvents is effective in the removal of processing oils and plasticizers in vulcanized mbbers, but zinc stearate is not completely removed and antiozonant wax gradually migrates to the mbber/polyurethane adhesive interface. Table 27.1 shows the moderate increase in adhesion produced in SBR by MEK wiping. 

On the other hand, if the mbber contains paraffin wax, the surface treatment with sulfuric acid promotes its migration to the surface creating a weak boundary layer able to produce poor adhesion. Solvent wiping with petroleum ether after surface treatment removes this antiadherent moiety but a progressive migration from the bulk to the mbber surface with time occurs. 

Solvent wipe (MEK, MIBK, trichloroethylene) Low- to medium-strength... 

Abrasion of surface (sandblasting, coarse sandpaper, etc.) plus solvent wipe Medium- to high-strength... 

Parts molded from polyetherimide can be assembled with all common thermoplastic assembly methods. Adhesives that are recommended include epoxy, urethane, and cyanoacrylate. However, service temperature must be taken into consideration in choosing an adhesive because PEI parts are generally used for high-temperature applications. Good adhesion can be effected by simple solvent wipe, but surface treatment by corona discharge, flame treatment, or chromic acid etch will provide the highest bond strengths. 

Simple Solvent Wipe Test. The simplest test method to determine the extent of cure is to rub a cotton swab that has been soaked in a suitable solvent (e.g., methyl ethyl ketone) against the surface of the cured adhesive. If the adhesive softens, it is very far from a fully cured condition, and the degree of softness is a very gross indication of the degree of cure. 

Polyvinylchloride, polyvinylidene chloride, polyvinyl fluoride Trichloroethylene, methyl ethyl ketone 1. Abrasion grit or vapor blast or 100-grit emery cloth followed by solvent degreasing. 2. Solvent wipe with ketone. Suitable for rigid plastic. For maximum strength, prime with nitrile phenolic adhesive Suitable for plasticized material... 

Butadiene styrene Toluene 1. Abrasion followed by brushing. Grit or vapor blast or 280-grit emery cloth followed by solvent wipe. 2. Prime with butadiene styrene adhesive in an aliphatic solvent. 3. Etch surface for 1-5 min at RT following method 2 for natural rubber. Excess toluene results in swollen rubber. A 20-min drying time will restore the part to its original dimensions... 

Chlorosulfonated polyethylene Acetone, methyl ethyl ketone Abrasion followed by brushing. Grit or vapor blast or 280-grit emery cloth followed by solvent wipe. General-purpose bonding... 

Polybutadiene Methanol Solvent wipe. General-purpose bonding... 

In order to check the paintability of parts molded with Q2-7119, test panels molded with and without silicone fluid were post-cured, solvent wiped with toluene, primed with PPG Durethane 600 Primer and then top coated with Durethane 300 blue metallic flake or white. Painted samples were exposed for 2 years in Florida Direct Black Box 5° South and then evaluated for appearance and adhesion. Results of these tests showed no difference between control and IMR-containing panels. Paint adhesion was excellent. 

The test method used was a solvent wipe test where specified pressures and solvent concentrations are applied to each coated sample. Data generated was number of seconds to pinhole distortion which relates to amount of cure. Figure 4 elucidates the results. 

Historically, surface treatments to improve adhesion of coatings to plastics consisted of mechanical abrasion, solvent wiping, solvent swell that was followed by acid or caustic etching, flame treatment, or corona surface treatment. Each of these treatments has limitations, thus providing a strong driving force for the development of alternative surface preparation methods. Many of the common methods mentioned are accompanied by safety and environmental risks, increased risk of part damage, and expensive pollution and disposal problems. 

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