The following case study appeared in the August 2016 issue of the Adhesives & Sealants Industry magazine.
A large electronics manufacturer did all of its staking and potting of electronic components at one of its plants based in the U.S. The company had been mixing adhesives in-house for over 10 years using a legacy custom adhesive mixing machine.
When the machine broke down, the company initiated an internal review of its adhesive mixing process. The main objective was to determine alternatives to mixing in-house as the cost to replace the mixing machine was significant.
As a result of the internal review, however, the manufacturer discovered a number of challenges and potential hazards directly and indirectly impacting the company’s productivity and the health and safety of its technicians.
The adhesive resins the company relied on contained fillers that settled over time – a process similar to paint settling after a few weeks.
Re-dispersion of these clumped fillers into the liquid resin was challenging and time consuming for the technicians responsible for mixing and catalyzing the adhesives – even with the mixing machine.
In addition, the process review revealed that each technician performed the mixing and catalyzing process differently.
Although the process differences, which included time, technique and degassing, were sometimes subtle, they resulted in different flow and leveling characteristics while also increasing the potential for failure in the field.
The review also uncovered a number of potential contamination issues.
Since the resins and hardeners were only available in quantities significantly larger than the batch size, the containers needed to be opened repeatedly. Repeated use left hardened residue around the containers’ lips, lids, and caps.
This residue had the potential for falling into the batch. The hardened residue also prevented proper sealing of the containers – increasing the potential for atmospheric contamination and/or loss of volatiles.
Lastly, workers were exposed to chemical hazards due to manually transferring, mixing, and cleaning the mixing tools. While the mixing surfaces themselves were clean, residual splatter marks on the walls were evidence that the operators had a high risk of additional exposure.
A job hazard analysis showed workers required extensive training in chemical safety, equipment operation, and proper waste disposal.
As a result of this internal review, the process engineer recommended the manufacturer begin using pre-mixed and frozen (PMF) packaged adhesives.
One of the main advantages of PMF adhesives is they come pre-packaged in easy-to-use syringes ranging in size from 1cc to 55cc; syringes can be used manually or as part of a robotic dispensing system.
To create a PMF adhesive, a resin (Part A) and a hardener (Part B) of a system, typically polyurethanes, epoxies, polysulfides, and silicones, are mixed together.
The adhesive is degassed and then frozen to < -40°C. Freezing stops the reaction – allowing the material to be stored, without settling, for up to one year.
As a reactive adhesive cures, it will increase in viscosity until it’s no longer usable. By freezing an adhesive, the viscosity, when thawed, will be nearly the same as when it was first mixed.
When using a PMF packaged adhesive, the in-house mixing process is eliminated and operator exposure to chemicals is greatly reduced.
When needed, individual syringes are taken from their cryogenic storage, thawed at room temperature for 10 to 20 minutes, and then used.
In addition, PMF adhesives are more reliable because they’re mixed, degassed, and thoroughly tested prior to use.
Initially, the process engineer liked the idea of using PMF adhesives from Appli-Tec, as the product would solve the company’s challenges.
He did, however, have one concern: if the company were to switch to PMF adhesives, they needed to be stored in a cryogenic freezer, which would cost thousands of dollars.
To address this concern, Appli-Tec loaned the company a 1-cubic foot cryogenic freezer that plugged into a standard outlet and maintained a -70°C temperature.
With this freezer, the engineering team then tested the PMF adhesives for 60 days. At the conclusion of the trial period, the team determined the pre-packaged, frozen adhesives solved their challenges – and provided other benefits as well.
Many multicomponent adhesive systems are caustic, volatile and can irritate the skin or lungs when fumes are breathed. Because the adhesive was now in a small syringe versus large open containers, its exposed surface area was greatly reduced.
By outsourcing the adhesive mixing and moving to pre-packaged PMF adhesives, the company cleaned up its production area – eliminating the potential for future exposure and contamination.
Each batch of PMF adhesive was processed in a systematic and repeatable manner and tested at the time of manufacture, which removed the engineering team’s worry concerning product inconsistencies and potential failure in the field.
As part of its process, Appli-Tec conducts incoming inspection, including FTIR validation of each chemical before its use. The mixing environment is temperature and humidity controlled.
Mixing is performed to a documented procedure with every lot number, quantity and time recorded. Each mix is tested to both internal and external specifications.
Appli-Tec also provided the company with full end-to-end product traceability. All documents were kept on file for review, and a sample of each batch shipped was also kept in storage.
Disposing of hazardous chemicals is costly. Companies today must certify individuals who then designate the chemical and the waste stream to which it belongs. Companies must also bear the cost of removing these designated hazards and provide documentation to the proper regulating authorities.
Purchasing individual syringes based on application needs enabled the company to significantly lower the amount of material entering the waste stream.
When mixing had been done in-house, the technicians responsible often had people showing up each morning to “place orders.” If someone had an urgent need, all other people on the team would have to wait – creating a huge bottleneck in the company’s manufacturing process and increased stress for the mixing technicians.
By outsourcing the adhesive mixing process, and purchasing pre-packaged PMF adhesives, the company significantly improved its manufacturing productivity – which more than paid for the cryogenic freezer.
Outsourcing the adhesive mixing delivered another benefit as well: The mixing technicians became responsible for inventory control and ensuring the right adhesives were in stock for the various manufacturing teams.
Due to freeing up so much of their time, the technicians were trained for other tasks within the company – a win-win for everyone concerned.
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