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The Role of Hot Ovens in the Powder Coating Process

April 28, 2017

Of all the stages in the powder coating process, the oven baking station is the most satisfying, for this is where the curing work takes place. With that bold statement said, we need to back up this claim with some facts that illustrate the role of hot ovens in powder coating. We'll talk about temperatures and time, dwell length and cycle periods, and really get into that all-important cross-linking process.

The Expanded Role of the Powder Coating Oven

In basic terms, the role of any powder coating oven is to liquidise the adhering powder until it flows and covers a workpiece. However, things get complicated when we adopt a detail-oriented viewpoint. Yes, the heat exuded by the oven raises the sealed interior past the powder's melt point, but what happens then? It flows, reaches an intelligently designed viscosity, at which point the cross-linking stage is initiated. Back at that flow point, though, there's a "bring-up" and "dwell" period, timed events that ensure the melting point is held. Basically, cure dynamics is a science, a field that has no room for guesswork, so these periods and their associative temperatures points should be known if the finishing process is to maintain a repeatably professional look.

Demystifying Cross-Linking

This chemical bonding mechanism takes place in the hot powder coating oven when the liquidised material enters its reactive phase. The curing material bonds on a molecular level to every other melted granule, plus it bonds to the cleaned surface of the workpiece. Manufacturers tend to use the words "curing" and "cross-linking" interchangeably, which is their right, but a true cross-linked coating is one that uses a thermosetting base, not a thermoplastic material. Thermoplastics, according to lead powder coating experts, melt and fuse like plastic, then they form a smooth, protective membrane. Obviously, the thermosetting medium produces a better bond, one that chemically reacts to create an impermeable shell. Meanwhile, back in an oven that's processing a thermoplastic resin, the coating is thick and impact-resistant, but the fused results aren't quite as bond-proficient as a similar thermosetting material base.

It's true that a commercial hot oven, one designed specifically for powder coating, doesn't use the same kind of cooking methods we see in a regular kitchen. However, there are recipes in use here. They're recipes that use time and temperatures to fluidise and cross-link special resins. There's even cross-linking ingredients in this special recipe. They ensure full chemical reactance and uniform curing, the kind of properties that benefit both the thermosetting and thermoplastic backbones of a top-tier powder coated film.

GP Industries Pty Ltd

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1 Regal Court,
Vermont South VIC 3133

Phone: (03) 9802 1355

Fax: (03) 9802 6027

Email: gp_ind@bigpond.com

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Bayswater North VIC 3153

Phone: (03) 9761 7676

Fax: (03) 9761 7671

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