Sikaflex®-250 PC
Warm applied adhesive with exceptional application properties
Sikaflex®-250 PC is an elastic 1 component polyurethane adhesive that cures on exposure to atmospheric humidity. Sikaflex®-250 PC is applied at a temperature of 85 °C and develops extraordinary application properties and high initial strength. As such it is eminently well suited for medium to large production runs.
- Excellent application properties
- Suitable for automated application
- High initial strength
- Very short cut-off string
PRODUCT BENEFITS
- Excellent application properties
- Suitable for automated application
- High initial strength
- Very short cut-off string
Areas of Application
Sikaflex®-250 PC fits bonding applications in automated processes best. It can also be used for standard non automated lines. Seek manufacturer’s advice and perform tests on original substrates before using Sikaflex®-250 PC on materials prone to stress cracking. Sikaflex®-250 PC is suitable for experienced professional users only. Test with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.Product Details
| Chemical base | 1-component polyurethane | |
| Color (CQP001-1) | Black | |
| Cure mechanism | Moisture-curing | |
| Density (uncured) | 1.1 kg/l | |
| Non-sag properties | Very good | |
| Application temperature | product ambient | 85 °C 5 - 40 °C |
| Skin time (CQP019-1) | 10 minutes A | |
| Open time (CQP526-1) | 6 minutes A | |
| Curing speed (CQP049-1) | (see diagram) | |
| Shrinkage (CQP014-1) | 2 % | |
| Shore A hardness (CQP023-1 / ISO 48-4) | 55 | |
| Tensile strength (CQP036-1 / ISO 527) | 7 MPa | |
| Elongation at break (CQP036-1 / ISO 527) | 450 % | |
| Tear propagation resistance (CQP045-1 / ISO 34) | 15 N/mm | |
| Tensile lap-shear strength (CQP046-1 / ISO 4587) | 4 MPa | |
| Service temperature (CQP509-1 / CQP513-1) | -40 ─ 90 °C | |
| Shelf life | cartridge drum / pail | 9 months B 6 months B |
| CQP = Corporate Quality Procedure | A) 23 °C / 50 % r. h. | B) storage below 25 °C |
CURE MECHANISM
Sikaflex®-250 PC 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®-250 PC
CHEMICAL RESISTANCE
Sikaflex®-250 PC 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®-250 PC can be processed at climate conditions between 5 °C and 40 °C, but changes in reactivity and application properties have to be considered. The optimum climate and substrate temperature is between 15 °C and 25 °C.
Sikaflex®-250 PC need to be heated up to 85 °C prior the application. Application equipment must be hence capable to heat up the required amount of adhesive to the required temperature. For cartridges, this usually takes 60 minutes in a cartridge oven set at 85 °C. Cartridges can be re-heated form cold several times, but must not be kept at 85 °C for more than 10 hours in total.
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®-250 PC can be processed with hand, 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.
Removal
Uncured Sikaflex®-250 PC 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.