Araldite 2029-1 Two-Component Gap-Filling Polyurethane Structural Adhesive

This cold-curing structural adhesive is suitable for metal bonding, shows adhesion to copper and brass, and supports manual or robotic dispensing.

Araldite 2029-1 from Huntsman Advanced Materials is a cold-curing, two-component polyurethane structural adhesive consisting of a grey resin component and a beige hardener component. When mixed, it forms a dark grey paste. The product is positioned as a gap-filling rigid structural adhesive with medium open time, high strength on metals, and adhesion to copper and brass.

Product data show a mix ratio of 100:82 by weight and 100:100 by volume; the viscosity of both Components A and B is 60 Pa·s at 25°C; the mixed specific gravity is 1.32; the pot life is 40 minutes for 10 g at 25°C; and the lap shear strength at 23°C is greater than 15 MPa. The product is available in cartridges incorporating mixers and can be applied as a ready-to-use adhesive with the aid of tools recommended by Huntsman Advanced Materials.

That surface treatment is critical to bond strength and durability. At the very least, joint surfaces should be cleaned with a good degreasing agent such as acetone, isopropanol (for plastics) or other proprietary degreasing agents to remove all traces of oil, grease and dirt. Low-grade alcohol, gasoline (petrol) or paint thinners should never be used. The strongest and most durable joints are obtained by either mechanically abrading or chemically etching the degreased surfaces, and abrading should be followed by a second degreasing treatment.

That a layer of adhesive 0.05–0.10 mm thick will normally impart the greatest lap shear strength to the joint. Huntsman stresses that proper adhesive joint design is also critical for a durable bond. Joint components should be assembled and secured in a fixed position as soon as the adhesive has been applied. The adhesive may be applied manually or robotically to pretreated and dry joint surfaces. All tools should be cleaned with hot water and soap before adhesive residues have had time to cure; removal of cured residues is difficult and time-consuming. If solvents such as acetone are used for cleaning, operatives should take appropriate precautions and avoid skin and eye contact.

Typical cured properties are based on standard specimens, for example aluminium specimens that were sandblasted, cured for 16 hours at 40°C and tested at 23°C. Typical average metal-to-metal lap shear strengths are approximately in the 18–24 MPa range. In plastic-to-plastic tests, typical values are approximately 24–27 MPa for CFRP and EP-GRP, about 10 MPa for UP-GRP, and about 4–6 MPa for several engineering plastics, with some tests showing substrate failure. The temperature curve shows typical lap shear strength of about 27–28 MPa near 0°C, about 10 MPa at 60°C and about 5 MPa at 80°C. After 100 thermal cycles from -30°C to 70°C, the typical value is about 27 MPa; after 90 days of heat ageing at 70°C, the typical value is about 29 MPa; and after 90 days of tropical weathering, about 12–13 MPa. 

The product should be stored in original sealed containers, with the expiry date indicated on the label. Uncured materials should not be allowed to come into contact with foodstuffs or food utensils, and measures should be taken to prevent uncured materials from coming into contact with the skin. The wearing of impervious rubber or plastic gloves and the use of eye protection will normally be necessary. The skin should be thoroughly cleansed at the end of each working period by washing with soap and warm water; the use of solvents is to be avoided. Disposable paper towels, not cloth towels, should be used to dry the skin. Adequate ventilation of the working area is recommended.