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Product category: Adhesives, threadlockers and other consumables
News Release from: Huntsman Advanced Materials | Subject: Araldite 2015
Edited by the Engineeringtalk Editorial Team on 24 August 2004

Structural epoxy helps create
battery-free torch

Bonding technology from Araldite adhesives has played a key role in the development of a battery-free flashlight.

Bonding technology from Araldite adhesives has played a key role in the development of a battery-free flashlight The NightStar flashlight, powered by a magnetic charging system, is being used by soldiers, mariners, miners, outdoor enthusiasts and emergency responders worldwide for reliable lighting in challenging situations

Manufactured by Applied Innovative Technologies, the NightStar produces more than 20min of high-brightness light after being shaken for only 30s.

The magnetic charging system uses zinc-plated, rare-earth ceramic magnets bonded in either end of a polycarbonate (PC) housing with Araldite 2015 structural epoxy adhesive.

Supplied by Huntsman Advanced Materials, the toughened epoxy maintains its bond strength even when exposed to extreme temperatures, shocks and vibration.

Steve Vetorino, Vice President and R and D Director at Applied Innovative Technologies said: "Araldite 2015 epoxy adhesive plays a significant role in the reliable performance of our NightStar flashlight, supporting its use in the most demanding environments and applications".

"During development we tried numerous different magnet and adhesive combinations".

"Huntsman's Araldite epoxy adhesive was the only material that provided the required performance".

"In fact, in shear tests, the ceramic magnets tore apart before bonds broke.

The epoxy has the added benefit of being cost effective and easy to handle".

During assembly, a PC housing is placed in a holding fixture and a repulsion magnet in another jig to ensure its precise orientation.

Bond surfaces require no pretreatment but care is taken to handle magnets with gloves to prevent fingerprint contamination.

To prepare for bonding, technicians install a 50ml dual-barrel cartridge containing premeasured amounts of Araldite 2015 epoxy resin and hardener in a dispensing gun.

A static mixing nozzle is added to the cartridge front, adhesive is mixed in the nozzle and technicians apply a small amount of mixed epoxy to magnet surfaces.

The housing is then brought down onto the magnet so that it is securely seated in a small pocket in the bottom of the PC tube.

Vetorino explains: "The magnet is pressed into the housing so that adhesive spreads across the bottom and up around the sides, increasing the bonded surface area for greater strength".

Huntsman's Araldite 2015 epoxy adhesive is well suited for this process because its viscosity allows the material to easily flow in and fill gaps.

Technicians follow the same process to bond the second magnet in the top of the flashlight.

Flashlight sections then cure at room temperature for about eight hours before moving into final assembly.

The cured epoxy has a lap shear strength of 21.7MPa at 25C and maintains its high bond strength even at elevated temperatures.

It also exhibits good peel strength with a roller peel of 25 pli.

One of the toughest flashlights on the market, the NightStar flashlight has one moving part, a high-strength, neodymium charging magnet.

When the flashlight is shaken, the charging magnet rebounds between Araldite epoxy adhesive-bonded repulsion magnets, generating electrical energy as it repeatedly passes back-and-forth through a wire coil.

The energy in the coil is then stored in a high-energy capacitor that is corrosion-resistant, able to operate in extreme hot and cold temperatures and can be recharged several hundred thousand times.

When charged, the capacitor powers a light emitting diode (LED).

A specially designed acrylic lens and reflector project light from the LED into a concentrated, uniform beam measuring 3.66m in diameter at a distance of 15.24m.

The virtually unbreakable LED has a lifetime of tens of thousands of hours and is available in three colours: bright white, super-bright green or red to meet the needs of military personnel and hunters.

The NightStar flashlight also features a unique switch design that uses an on/off slider containing a magnet in combination with an internal reed switch.

When the reed switch is activated, energy from the capacitor flows into and powers the LED.

The switch is nonsparking and watertight, permitting the flashlight's use in mines, military installations and fuel depots where explosive materials are present.

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