Delo confirms dispensing properties of filled adhesives

Tests by industrial adhesive manufacturer, Delo, and dispensing company, ViscoTec, demonstrate that fillers do not cause mechanical abrasions to dispensing systems.

Delo partnered with ViscoTec, a dispensing company that manufactures systems and components required for conveying, dosing, applying, filling and emptying medium- to high-viscosity fluids, to perform experimental tests analysing adhesive abrasions to systems. The tests confirm that even highly filled adhesives can be dispensed reliably and precisely over the long term without causing mechanical abrasions to dispensing systems, reports Delo.

Automotive and electronics industries have a constant need to meet the demands found in temperature stability and media resistance. At the same time, properties like electrical or thermal conductivity or adapted expansion co-efficients need to be achieved, prompting adhesive manufacturers to fill their products with additional raw materials like metal or minerals. These robust materials are considered abrasive and have been thought to be difficult to dispense, but the recent tests conductred by Delo and ViscoTec has proved that assumption wrong.

ViscoTec used two of its dispensing units in the testing, eco-PEN and RD, with two elastomer stators each. Six epoxy resins from Delo with filler content between 25 to 50 per cent were used.

The stators were placed in the adhesives for 168 hours. General chemical suitability for long-term contact was observed as well as the change in mass, the dimensional accuracy and the hardness and elasticity of the elastomers. No abnormalities or deviations from the tight production tolerances were found, eliminating the idea that chemical reactions between two components would affect results.

A series of 24, long term tests included cyclic dispensing operations, each included two seconds of dispensing, followed by a one second pause to simulate typical dispensing behaviour of an automated manufacturing process. Just under 300,000 dispensing cycles make up each test series, corresponding to approximately 30kg of dispensed adhesive for the eco-PEN dispenser and approximately 240kg for the RD dispensers. Every 20 hours, three dispensing shots were weighed and compared over time. The test results confirmed accurate and repeatable dispensing for all test pairs.

Karl Bitzer, head of product management at Delo, said, “Before and after the endurance tests, the rotors, made of hard chrome-plated stainless steel, and the elastomer stators of the dispensing units were measured. After 300,000 dispensing cycles, there was no sign of wear on the rotors and a miniscule sign of wear on the stators that fell within the tight manufacturing guidelines”.

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