Primers application

DataSource Literature Methods PCR primers Applications Loss Of Heterozygosity Species human TargetGene TP53... 

Primers can be used to protect both treated metal and nonmetal substrates after surface treatment. The use of a primer as a shop protectant may increase production costs, but it may also provide enhanced and more consistent adhesive strength. The use of a primer greatly increases production flexibility in bonding operations. Usually primer application can be incorporated as the final step in the surface preparation process. The primer is applied as soon as possible after surface preparation and usually no more than a few hours later. The actual application of the adhesive may then be delayed significantly. 

Figure 10.8 Scanned image of the surface of two alloy panels showing adhesion failure caused by the omission of O2 plasma treatment of the substrate prior to plasma film deposition and application of the primer (Deft 44-GN-72 MIL-P-85582 Type I Waterbased Chromated Control Primer), a) Panel after Skydrol LD4 fluid resistance test, which had the O2 plasma treatment prior to film deposition and primer application, b) Panel after scribed wet (24-h immersion in tap water) tape test, which had not been treated with the O2 plasma treatment prior to film deposition and primer application.

A nonchromated, water-borne primer applied to [2B] alloy samples, with the appropriate surface preparation and plasma deposition of an ultrathin plasma polymer, was also compared to controls prepared by depositing a chromated primer on chromate conversion-coated A1 substrate. The same comparison was also performed for IVD Al-coated 2024-T6 substrates (pure aluminum is deposited by ion vapor deposition process on aluminum alloy 2024-T6). In the latter case, the primer could not be removed from the IVD Al-coated panels that were treated with the plasma polymer prior to spray primer application. It is interpreted that the water-borne spray paint penetrates into the column structure of the top surface of the IVD Al-coated substrates when the surface energy was modified by the application of a plasma polymer. This effect could be viewed as interactive coating with a porous surface. 

Table 32.4 displays the adhesion test results for different spray primers applied to T/F plasma-treated bare 7075-T6 alloys. The results demonstrate that this special plasma polymer coating gave rise to excellent water-insensitive adhesion of all three spray primers used in this study Turco solution could not delaminate any of the primers over a period of 24h. In addition, up to 6 days aging of T/F plasma coatings in air prior to primer application did not degrade the excellent adhesion performance of the systems. 

Primer Air exposure time of T/F before primer application Dry Tape Test Rating After boiled in H2O for 1, 2, 4, 6, 8h Delamination time in Turco solution (h)... 

In dip coatings the article is completely immersed in a large tank containing a certain quantity of paint to be applied. The article is then pulled out excess coating drains back into the dip tank. This technique is used for metal primer application such as motorcar bodies. 

One invention consists of a multipurpose cleaner/primer for roofing membranes. These elastomeric sheets are normally powdered with talc to prevent interlayer sticking in the roll. Instead of using separate cleaning solvent followed by a primer application the... 

Most structural film adhesives require a primer. Adhesive primers are usually spray-applied by air or airless spray systems. Roller or brush apphca-tion is sometimes used in small areas, or where spray equipment is not available. The primer coat must be air-dried and sometimes over-baked to remove solvents. The thickness of the prime coat will usually affect the adhesive bond strength and must be controlled and verified. This is usually accomplished by periodically certifying the primer applicator, and by monitoring primer thickness after drying. ... 

Epoxy primer application on the surfaces to be reinforced, after having thoroughly cleaned and dried them... 

Aqueous dispersions are used in fiber bonding, paper coating, friction and abrasive applications, and laminates and wood bonding. Phenolic dispersions improve the strength of latex-contact adhesive applications. Epoxy-modified phenolic dispersions are prepared by dispersion of the phenolic epoxy resin. The systems are used for baked primer applications and bonding requirements. Minimum baking conditions are 20 min at 150°C (26). 

The major use of phenoxies is as a vehicle for coating formulations. They are exceptionally useful in primer applications where drying speed, compatibility with various kinds of top coats, and high adhesive strength are required. Phenoxies ate used in automotive and marine primers as well as in heavy-duty maintenance primers. 

Because of the need for preheated metals it is necessary to modify some equipment, but this should not be a major financial factor. There will however be some increase in energy consumption but this will be less than the costs involved for solvent entrapment. Because of the need to preheat metals, especially for primer application, it has been simpler, initially, to introduce waterborne top coats on solvent-based primer. 

Application of primers to warm metals is not a problem with most operating systems. The limiting factor with all waterborne systems is the retention of sufficient heat in the metal to be able to spray both primer and top coat without reheating the metal after primer application. 

Application of the primer coat to freshly prepared metal must be as quick as possible to prevent atmospheric agents causing corrosion. Oxide films (corrosion) are not usually securely adhered to the surface of the parent metal and thus can be easily pulled away. If the bonding primer has adhered to the corrosion layer it too will be pulled away from the desired contact between the primer and metal. This corrosion may not be visible to the naked eye, but can result in nnderbond corrosion continuing after vulcanisation. Obviously ambient conditions in the metal preparation area dictate the timing and speed of primer application. 

LS is also the main component of many pyrotechnic mixtures for primers often in combination with GNGT (e.g., SINOXIDE composition [62]). It is moreover used as a component of fusehead composition (Valenta Private Communication). Despite its excellent properties for primer applications and plenty of experience, the presence of lead is causing its replacement by non-toxic alternatives. 

There are primarily two types of chemistries for the coating materials. One is epoxy-based and the other is acrylic-based. In general, epoxy-based coatings provide superior corrosion resistance and are used in applications where high corrosion resistance is required. This chemistry, however, does not have good resistance to ultraviolet light, and is commonly used in primer applications where a topcoat will be subsequently applied, particularly if the coated object needs to withstand sunlight. 

A well known metal adhesion application is in washed primers. Application information is available. Additional information is provided in the general references and Refs. 37 and 38. The Navy has long recognized the need to pretreat a metal surface prior to painting to inhibit corrosion and promote adhesion and specifies wash primers in MIL-F-15328C and MIL-C-8514B. 

Nylon fabric uppers show serious adhesion problems. The best bonding is obtained by mild roughening followed by applying 2 wt% isocyanate primer. Application of two-component polyurethane adhesive is also necessary. 

Okamoto, H., Y. Sugiyama, et al. (1992). "Typing hepatitis C virus by polymerase chain reaction with type-specific primers application to clinical surveys and tracing infectious sources." J Gen Virol 73 ( Pt 3) 673-679. 

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