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Precision in small doses: Tips for the precise dispensing of two-part adhesives

Author : Paul Whitehead

01 September 2020

When dispensing small amounts of two-part adhesives or other materials, two key considerations are whether the material is mixed correctly, and the accuracy of the amount dispensed. Here, Paul Whitehead, Key Account Manager at Intertronics, shares his thoughts on the precise metering, mixing and dispensing of small amounts of two-part materials.

There is a growing demand for the precise metering, mixing and dispensing of small amounts of two-part technical materials like adhesives, potting compounds, encapsulants and sealants – including electrically or thermally conductive variants. This is driven by manufacturers in the electronics, medical device and automotive industries requiring increased functionality in seemingly ever-smaller formats. In parallel, these engineers are looking for high-accuracy material application in a robust and consistent process. They want precise quantities, uniformly mixed in the correct ratio, to be applied in exact locations. 

Two-part formulations can offer superior cured performance but can be difficult to process. A typical method involves weighing out the constituent parts, mixing in a container with a spatula and loading into a dispensing syringe barrel for application. There may be a vacuum degassing or centrifuge step to remove entrapped air. Some suppliers offer respite from this procedure by providing their materials in a pre-mixed, degassed and frozen packaging. However, there are extra costs associated with shipping and storage, which are partly offset by the material being ready to use after thawing. 

Once the material is mixed (or thawed), curing starts and the material’s viscosity will begin to increase. Changes in viscosity will mean the amounts dispensed directly from the syringe, or through a dispensing valve using air pressure, will vary, and it is difficult to maintain an accurate deposition. Moreover, the mixed material will have a limited working life, which can lead to waste as it cures too much for it to still be usable. 

Read the full article in the September issue of DPA.

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