Surface primers

All methods of pretreating or modifying low-energy polymers before bonding are inconvenient, time-consuming and often expensive. The use of a surface primer, although inconvenient, is a much more desirable alternative that can be used on a production line. 

Other companies have discovered different primers that behave in a similar manner with cyanoacrylates. Henkel [56,57] has patented the use of imidazole derivatives and claim that bond strengths increase the longer the primer is left in contact with the substrate before application of the adhesive, in contrast to earlier primers. 

Toa Gosei [58] has covered primers comprising solutions of imidazole compounds in combination with chlorinated PP or methyl methacrylate/chloroprene copolymers. Koatsu Gas [59] has patented solutions of triethylphosphine and tri-N-propyl phosphine. 

Further credence was lent to this interpenetration theory when a similar effect was observed using a free radical-cured acrylic adhesive system [61]. In this system, the primer consisted of a solution of a copper (II) salt and the adhesive was based on methyl methacrylate monomer with a small amount of trifunctional monomer and a hydroperoxide/amine-based cure system. It was found that bonds formed on low-density PE result in substrate failure and that an interphase of mixed adhesive and PE is formed that is 1.5 mm-thick. 

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Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

Most commercially available silicone elastomers, and especially those which polymerize by addition-cure, do not, or weakly, adhere to most surfaces. Adhesion promoters known as surface primers are available and are often used to adhere the silicone to the protected... 

We tested 6 different silicone casting elastomers In conjunction with 3 surface primers. The materials and their designations are as follows ... 

The 6th material Is a condensation-cure product which has been previously used for medical Implant protection (I). As verified by lap shear tests, (described below), the first 3 elastomers provide minimal adhesion In the absence of a surface primer. The last 3 are self-prlmlng materials. To permit visual examination, we tried to select clear materials. All of the elastomers are clear except for types 5 and 6. 

Other than beads, porous polymer monoliths, which were photopolymerized in a COC chip, were used for solid-phase extraction. It is known that priming polymeric surfaces is not as simple as priming silica surfaces, which use a common surface primer agent, TMPM. Therefore, the grafting method as initiated by UV should be used to attach the polymer monoliths [588]. A similar strategy was used for sample pre-concentration of PAHs (e.g., pyrene). Pyrene (900 nM) was first concentrated by 400-fold in 24% ACN before switching to 56% ACN for CEC separation (see Figure 5.5) [148]. 

Polyurethane Methanol 1. Abrasion followed by brushing. Grit or vapor blast or 280-grit emery cloth followed by solvent wipe. 2. Incorporation of a chlorosilane into the adhesive elastomer system 1% by weight is usually sufficient. Chlorosilane is available commercially. Addition to adhesive eliminates need for priming and improves adhesion to glass and metals. Silane may be used as a surface primer... 

A good key or bond between the printing inks and the substrate to which they are applied is essential if detachment or pick is to be avoided. In certain instances surfaces need pretreatment (e.g. gas, or corona discharge) or a surface primer. 

The surface primer was prepared as a 40% methanol solution of a vinyl benzyl amine functional silane (Dow Corning Corporation Z-6032) by slowly adding methanol and then water. The mixture was allowed to stand for 24 hours to hydrolyze the silane and allow the low molecular weight oligomers to form. Samples of low density polyethylene (LDPE) film. 005" thick, supplied by U. S. Industrial Chemical Company (Resin NA140-00 containing no antioxidants) were prepared for use as the oleflnlc substrate. 

Polyolefin bonding has been advanced using cyanoacrylates through the use of surface primers. These primers promote adhesion to untreated polyethylene (PE), polypropylene (PP), and EPDM rubber. Table 7 shows comparison bonds using standard industrial-grade cyanoacrylates. 

Australian Fibreglass Supplies, Australia Tooling gel-coats, ISO NPG polyester for mold laminating, surfacing primers for plug work, mold release systems, waxes, polishes... 

Hawkeye Industries, USA Marine interior finishes, in-mold surfacing primers for post-painted parts, surfecing plaster plugs and models... 

There are many surface coatings that do this wallpaper, plastic sheet, chrome and silver plating. No coating material is more versatile than paint, which can be applied to any surface, however awkward its shape or size, by one process or another. Paint is a loosely used word covering a whole variety of materials enamels, lacquers, varnishes, undercoats, surfacers, primers, sealers, fillers, stoppers and many others. It is essential to grasp at once that these and other less obviously related products, such as plasters, concrete, tars and adhesives, are all formulated on the same basic principles and contain some or all of three main ingredients. 

Definition Prod, of polymerization of methylmethacrylate and trimethoxysilylpropylmethacrylate Uses Component of surface primers used with silicone polymers for repeated use food contact applies. 

For the whole family, 100 per cent liquid-to-solid conversion occurs by radical polymerisation of the vinyl group of the acrylic ester, a reaction catalysed by metal and inhibited by atmospheric oxygen. Typically, therefore, the adhesives cure only when the treated parts are assembled and air is excluded from the mating surfaces. The cure rate on non-metallic surfaces is generally too low for normal commercial use and here a secondary catalyst in the form of a surface primer is beneficial. With closely fitting parts, one metal surface is usually sufficient catalyst and when both surfaces are metallic, polymerisation is rapid at room temperature. Normally, components may be handled between five and twenty minutes after assembly with full strength after at least an hour - possibly very much longer with some materials. 

This rapidly developing group of materials, based on a variety of acrylic monomers, has viscosities which are fairly readily modified giving thin liquids, syrupy resins and thixotropic semi-solids. Some are truly single-component adhesives - the anaerobic versions (see Sections 5.1.2 and 5.1.12.1) - while others require some form of hardener. The hardener may be a surface primer or mixed directly into the adhesive. 

Initiators, accelerators, and inhibitors of cyanoacrylate polymerization are used to modify the cure speed and storage stability of these adhesives. They can also be used to broaden the range of materials which can be bonded with cyanoacrylates. Initiators are those materials which are capable of polymerizing cyanoacrylate esters upon contact. These are, therefore, applied either to the substrate surface ( surface primers ), or mixed with the adhesive just prior to application. Accelerators are materials which do not cause polymerization on contact with monomer, but which increase the cure rate once the adhesive is applied. These chemicals are most often compounded with the monomer in the adhesive formulation. The distinction between these two classes can be blurred, as some additions will not cause immediate polymerization on contact but will shorten shelf life in the long run. Anionic polymerization inhibitors are Lewis or Bronsted acids which retard or completely inhibit anionic polymerization. Radical inhibitors prevent polymerization by adventitious, radical sources and are used to prolong the storage stability of the adhesive they generally do not affect cure speed. 

Two other examples of heterocyclic-based initiators have been found. One is typified by triallyl isocyanurate (14) and the other is characterized by compounds containing either of the structures 15 or 16. Both of these types of initiators are described as being used either as surface primers or as components of two-part adhesives. 

A high quality polyester surface primer that provides outstanding filling and levelling properties, offering a rapid coat build-up for plugs and master mould surfacing. Adheres to epoxy resins and exhibits a heat distortion temperature of 150 C. 

Surface primers are now available which can act as an adhesion promoter. Loctite 770 (Henkel Loctite Adhesives Ltd) is a heptane-based primer which can be brushed or sprayed onto the surface of the rubber and then used with an ethyl-based cyanoacrylate. 

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