307 is a solvent-free, hot-curing adhesive film with high temperature and media resistance. At room temperature it is not tacky and can be easily cut to the shape of the bond area. Tackiness is developed at ca. 120°C, just before curing. This adhesive is used for bonding piezo ceramics in ultrasonic wave sensors onto metal surfaces where very low mechanical damping is required over a broad temperature range. It is also used for high temperature resistant structural bonding of PTFE layers onto aluminium with long-term temperature resistance up to 240°C.
Caracteristics of Bismaleimide Film
- Temperature resistant to 240°C
- Very high bond strength at high temperatures
- Very resistant to various chemicals
- Good bonds to aluminium, PTFE (Teflon®), and glass
- Improved easy and clean processing
307 should be prefereably used on carefully degreased and pretreated surfaces. Better joints are obtained on mechanically abraded and degreased surfaces, while chemical etching leads to best results. It is recommended to follow specific directions for surface pretreatments of various materials.
Application of Bismaleimide Film
The adhesive film can be cut to the shape of the bond area either manually or automatically. The transparent support film must be removed and the yellow adhesive film placed on one substrate. The second substrate should be placed on the adhesive film and fixed by mechanical clamps (or similar tools) for curing. Alternatively, the substrates can be heated to 120 °C. Upon contact with the hot surface, the adhesive film becomes tacky and sticks to the surface. The second hot substrate should then be placed on the adhesive and fixed for curing.
The adhesive film requires a minimum curing temperature of 150°C. Post curing at 200°C improves its properties significantly – especially its temperature and chemicals resistance. Only low fixing pressure is needed during the curing. The curing duration depends on how fast the adhesive can reach the needed temperature in the bond line. This is mostly governed by the thermal conductivity and the geometry of the substrates. As a guideline, curing should last for at least 30 min after reaching 150°C and 200°C, respectively. For first tests a curing schedule of 2h at 150°C + 2h at 200°C is recommended. Suitable tests under real-life conditions should be conducted by the user.
We tested the stability of adhesive joints in strong acids (sulphuric acid, phosphoric acid, at pH 1) and elevated temperatures up to 60 °C with good results. From experiments at customers we also know that solvent resistance is very high (acetone, methyl ethyl ketone, and N-methyl pyrrolidone were tested). We do not have much information about resistance in basic media (pH 10). Fuel resistance was tested in biodiesel and regular diesel with excellent results as well. However, it is important to note that the surface preparation of the bonded parts has a strong influence on the resistance of the overall adhesive joint. Water and other aqueous media are especially known to penetrate into the bondline and destroy the adhesion, even if the adhesive layer itself is still intact. Surface treatment with adhesion promoters (silanes) can often help in such cases.
Other informations about Bismaleimide Film
307 may be stored in its original container between 4 and 35°C (do not freeze!). Avoid direct sunlight. Shelf life is 12 months. Expiry date is indicated on the label.
Spare amounts of the adhesive should be cured and then disposed of according to local regulations.
When using the adhesive wear protective glasses and gloves. Refer to further instructions in the MSDS.
Final Advanced Materials provides also a full rang of epoxy adhesives.