When it comes to electronic devices, sealing the hardware from moisture and environmental chemicals is critical to the reliability of the device. Most electronics are housed in enclosures made of metal or plastic, which is designed in such a way to protect the hardware and to offer an easy assembly process when manufacturing. Sealing these enclosures is typically accomplished with gaskets or bonding, depending on reworkability requirements.
Facilitating the bonding and sealing of an enclosure with one product leads to challenges: The adhesive should be high enough modulus and strength, so that the two components are held together firmly, but flexibility of the adhesive is critical when it comes to the ability to maintain a positive seal; This is especially the case when a product is flexed or dropped, in the case of consumer electronics..
Many people are familiar with 1-part, moisture curing silicone and polyurethane adhesives when it comes to flexible bonding and sealing:
Silicones have very good flexibility, which is a requirement of sealant, but they have issues bonding to plastic substrates. They can also degrade when exposed to various chemicals and UV exposure. To improve flexibility of silicones, ow molecular weight silicone is added to formulations and this can have outgassing issues which can cause production/assembly issues when bonding operations need to occur downstream. Silicone outgassing can also affect optical components and other electronics.
Polyurethane adhesives offer good bonding and flexibility along with being able to adhere to many substrates. The biggest issue with polyurethane adhesives is the chemical resistance with normal chemicals and skin oils that can be encountered with consumer electronics. Polyurethanes by their nature are also affected by moisture during the cure process and can form bubbles in the bundling which affects the sealing of the joint
Modified silane (MS) polymers are a newer chemistry that was developed to overcome the deficiencies of polyurethanes and silicones. These silane-terminated polymers are formed by attaching a silane group to a polymer backbone. This unique structure allows the adhesive to form robust bonds to a wide variety of materials, whilst having superior flexibility and tear strength that is needed to perform as a sealant.
Core benefits of MS Polymers:
good primer-less bonding to a variety of organic and inorganic substrates
High flexibility and tear strength
Low VOC
Excellent chemical and environmental resistance
Stable performance under High Temp, High Humidity (HTHH) conditions
Rapid moisture curing that can be accelerated with heat
Low shrinkage during curing
Meets RoHS, REACH and Low Halogens
Our partner, Everwide Chemical (Taiwan), are experts in MS polymer formulation and have a portfolio of over 70 different MS Polymers with features including (but not limited to): Tin Free, UL94-V0, thermally conductive, low/high viscosity, low shrinkage, high bond strength, color (white/black/clear). And when an exact MS polymer is required to suit unique customer requirements, rapid customized MS polymers are also available.
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