Sikaflex®-552 AT
Elastic STP adhesive for vehicle-assembly bonding
Sikaflex®-552 AT is an elastic 1-component Silane Terminated Polymer (STP) adhesive especially designed for bonding large components in vehicle assembly. It is suitable for bonding coated metal, GRP, ceramic materials and plastics. It bonds well to a wide range of substrates with minimal pre-treatment.
- Good adhesion to a wide variety of substrates without primer
- Isocyanate- and solvent-free
- Can be painted
- Capable of withstanding dynamic stresses
- Ageing- and weathering-resistant
PRODUCT BENEFITS
- Good adhesion to a wide variety of substrates without primer
- Isocyanate- and solvent-free
- Can be painted
- Capable of withstanding dynamic stresses
- Ageing- and weathering-resistant
Areas of Application
Sikaflex®-552 AT is suitable for joints that will be subjected to dynamic stresses. Suitable substrate materials are metals, particularly aluminum, metal primers, paint coatings, sheet steel, ceramic materials and plastics. It bonds well to a wide range of substrates with minimal pre-treatment.. Seek manufacturer’s advice and perform tests on original substrates before using Sikaflex®-552 AT on materials prone to stress cracking. Sikaflex®-552 AT is suitable for experienced professional users only. Tests with actual substrates and conditions have to be performed ensuring adhesion and material compatibility.Product Details
| Chemical base | Silane Terminated Polymer | |
| Color (CQP001-1) | White, black | |
| Cure mechanism | Moisture-curing | |
| Density (uncured) | 1.5 kg/l | |
| Non-sag properties (CQP061-1) | Very good | |
| Application temperature | ambient | 5 ─ 40 °C |
| Skin time (CQP019-1) | 30 minutes A | |
| Open time (CQP526-1) | 20 minutes A | |
| Curing speed (CQP049-1) | (see diagram) | |
| Shore A hardness (CQP023-1 / ISO 48-4) | 50 | |
| Tensile strength (CQP036-1 / ISO 527) | 3 MPa | |
| Elongation at break (CQP036-1 / ISO 527) | 600 % | |
| Tear propagation resistance (CQP045-1 / ISO 34) | 15 N/mm | |
| Tensile lap-shear strength (CQP046-1 / ISO 4587) | 2 MPa | |
| Service temperature (CQP509-1 / CQP513-1) | -50 – 90 °C | |
| Shelf life | cartridge unipack drum / pail | 15 months B 12 months B 9 months B |
| CQP = Corporate Quality Procedure | A) 23 °C / 50 % r.h. | B) storage below 25 °C |
CURE MECHANISM
Sikaflex®-552 AT cures by reaction with atmospheric moisture. At low temperatures the water content of the air is generally lower and the curing reaction proceeds somewhat slower (see diagram 1).
Diagram 1: Curing speed Sikaflex®-552 AT
CHEMICAL RESISTANCE
Sikaflex®-552 AT is generally resistant to fresh water, seawater, diluted acids and diluted caustic solutions; temporarily resistant to fuels, mineral oils, vegetable and animal fats and oils; not resistant to organic acids, glycolic alcohol, concentrated mineral acids and caustic solutions or solvents.
Application
Surface preparation
Surfaces must be clean, dry and free from grease, oil, dust and contaminants.
Surface treatment depends on the specific nature of the substrates and is crucial for a long lasting bond. Suggestions for surface preparation may be found on the current edition of the appropriate Sika® Pre-treatment Chart.
Consider that these suggestions are based on experience and have in any case to be verified by tests on original substrates.
Application
Sikaflex®-552 AT can be processed between 5 °C and 40 °C but changes in reactivity and application properties have to be considered. The optimum temperature for substrate and sealant is between 15 °C and 25 °C.
Consider the viscosity increase at low temperature. For easy application, condition the adhesive at ambient temperature prior to use.
To ensure a uniform thickness of the bondline it is recommended to apply the adhesive in form of a triangular bead (see figure 1).
Figure 1: recommended bead configuration
Sikaflex®-552 AT can be processed with manual, pneumatic or electric driven piston guns as well as pump equipment.
The open time is significantly shorter in hot and humid climate. The parts must always be installed within the open time.
Never join bonding parts if the adhesive has built a skin.
For advice on selecting and setting up a suitable pump system, contact the System Engineering Department of Sika Industry.
Tooling and finishing
Tooling and finishing must be carried out within the skin time of the adhesive. It is recommended using Sika® Tooling Agent N. Other finishing agents must be tested for suitability and compatibility prior the use.
Removal
Uncured Sikaflex®-552 AT can be removed from tools and equipment with Sika® Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically.
Hands and exposed skin have to be washed immediately using hand wipes such as Sika® Cleaner-350H or a suitable industrial hand cleaner and water.
Do not use solvents on skin!
Overpainting
Sikaflex®-552 AT can be best painted within the skin formation time. If painting process takes place after the sealant has built a skin, adhesion could be improved by treating the joint surface with Sika® Aktivator-100 or Sika® Aktivator-205 prior to paint process. If the paint requires a baking process (> 80 °C), best performance is achieved by allowing the sealant to fully cure first. All paints have to be tested by carrying preliminary trials under manufacturing conditions.
The elasticity of paints is usually lower than that of sealants. This could lead to cracking of the paint in the joint area.