Primer 760 – PU to Metal – 0.1kg

Features and Benefits

• Versatile – Bonds a wide variety of both polyether and polyester compounds, including RIM, eliminating the need to stock several adhesives in your plant.
• Tolerant to Process –  Accommodates a wide range of processing conditions, including prebaking.
• Durable Bonded – assemblies are particularly resistant to exposure to harsh environments, thus giving longer service life products.
• One Coat Only – a single dip or brush coat is required, thus minimising application costs.
• Non-Settling Product – does not require agitation saving application time and eliminating possible application errors.
• Fast Drying Allows – rapid turnaround times in the plant and minimises the need to keep large inventories of coated parts.

*Typical – not for specification
**Not Routinely tested – Theoretical value

Bonding with Primer 760

Metal Surface Preparation

Proper penetration on of the surfaces to be bonded is one of the most important factors influencing adhesion in any bonding process. For op mum performance the substrate must be prepared in such a way as to provide a receptive surface for the adhesive.
The importance of meticulous preparation on cannot be over­emphasised. Metal surface preparation on may be broadly divided into two classes; mechanical methods and chemical methods.

Mechanical Method

Mechanical methods include such operations as blasting with sand, grit and metal oxides; abrading with a wire brush, steel wool or backed abrasives; and machining or scoring with cutting tools. Chemical solvent cleaning is sometimes necessary with methods that are classified as mechanical.

Blasting with grid (steel or aluminium oxide) combined with solvent cleaning is a widely used and generally excellent method of preparing steel surfaces. It is especially useful for metals covered with rust, scale, oxide layers and similar corrosion compounds, or those badly soiled or contaminated with materials such as processing oils or corrosion protection greases. A typical sequence of steps is vapour degrease, grit, vapour degrease

Initial degreasing with Trichloroethylene (TCE) or Perchloroethylene (PERC) is intended to remove contaminants such as greases and oils. Such ac on may not be effective in removing soaps, and certainly not scale or corrosion. The primary purpose of this first cleaning is to remove materials, which would contaminate the media in the subsequent blasting opera on.

Blasting consists of impinging abrasive particles against the surface of the metal with a stream of air. Grit is preferred over shot because grit produces a rough open surface, while shot sometimes tend to peen the surface occluding contaminants. The most commonly used grid size is 30 ­ 40 mesh.

The second degreasing step is a safety factor designed to remove abrasive dust or any contaminants, which may have been present in the blasting medium. Grinding or abrading with wire brushes, steel wool, or abrasive cloth produces satisfactory bonding surfaces. Freshly milled or machine surfaces are also excellent for bonding, providing cu ng oils are properly removed. The same practices of degreasing should be followed as was discussed under grit blasting.

Chemical Method

Chemical methods utilise inorganic reagents in two types of chemical reaction:

• ­Conversion of the metal surface from an essentially free metallic or metal oxide state into metallic compounds.­
• Elimination of soils and surface contaminants by chemical ac on such as decomposition.
• A wide variety of chemical treatments are available to meet the needs of nearly every bonding application.
• Some of the types available include phosphatisation, alkaline treatment, acid rinse, chromate and phosphate conversion coatings, chemical etching and plating.

Selecting a Method

The choice of mechanical or chemical methods is dictated by several considerations:

• Economics: Chemical methods are generally less expensive than mechanical methods.
• Versatility: The same mechanical method may be applicable to many metal surfaces whereas chemical treatments tend to be substrate specific.
• Adaptability: Exis ng facilities may favour either mechanical or chemical processing.
• Performance requirements: Products vary widely in the degree of adhesion required, processing and surface preparation methods must be adapted accordingly.
• Environmental resistance: Chemical conversion often imparts enhanced resistance to harsh environments.
• Regulatory considerations: In some areas, waste disposal considerations may preclude the use of chemical treatment.

Protection Of The Prepared Surface

The freshly prepared surface must be protected against contamination and corrosion. Care must be exercised to avoid handling freshly prepared metal parts. The best way to accomplish this is by applying the adhesive as soon after surface preparation as is practical. PRIMER 760 provides a tough barrier to protect from contamination by dirt, oils or moisture to preserve the ability for bonding with applied RIM or castable urethane.
For more detailed discussion of substrate preparation, please contact Lord bulletin number DS10­7101.

Application of Primer 760

PRIMER 760 may be easily applied by brush, dip or spray ­using application equipment. No agitation of the adhesive is required prior to application. Optimum applied dry film thickness is 18 ­ 25 microns (µm).

Brushing

PRIMER 760 can be applied by brush as received or preferably slightly thinned with Oxitol Acetate and/or MEK prior to use. Use of a 4 : 1 ratio of adhesive to solvent is usually satisfactory.

Dipping

PRIMER 760 can be used as received for dip applications. As supplied, dipping will result in a dry film thickness of 18 ­ 25 microns on a vertical surface.

Spraying

PRIMER 760 should be diluted with an Oxitol Acetate / MEK (1 : 1) mixture until a viscosity of 20 ­- 22 seconds with a Zahn No. 2 cup is attained. This will correspond to a dilution ratio of 1 part PRIMER 760 to 1 part Oxitol Acetate / MEK thinner by volume.

Drying

Parts coated with PRIMER 760 should be air dried for 30 ­- 60 minutes. Forced drying can be accomplished at temperatures up to 120ºC.
NOTE: To prevent bubbling of the film, Primer 760 should not be applied to substrates hotter than 80ºC.

Prebaking Of The Coated Part

After PRIMER 760 has been applied, large metal parts, which act as heat sinks, are preheated prior to casting. The adhesive is pre­cured on the part and the overall environmental resistance of the bonded part is actually enhanced by this pre­cure. PRIMER 760 shows a wide tolerance for pre­bake, accepting pre­bake periods as long as 16 hours at 120ºC without adverse effect on adhesion.

Safety & Handling

• PRIMER 760 is FLAMMABLE
• Do not use near open flames, sparks or sources of heat
• Do not smoke during application
• Avoid contact with skin and eyes
• Wear protective gloves and goggles
• Wash thoroughly after use and before eating and smoking
• Avoid breathing of vapours and mists
• Use in a well ventilated atmosphere
• Wear a breathing mask
• Harmful or fatal if swallowed. If swallowed, do not induce vomiting, but seek medical advice immediately
• Do not return unused product to the original container
  Keep container closed when not in use

Refer to Material Safety Data Sheet (MSDS) on PRIMER 760 for full safety information on handling and disposal.