Non stick coatings for injection molding? Yes! Just recognize the difference between ‘lubrication’ and ‘release’ and you need never fail again.
Today, there are a number of hard coatings for you, the mold maker, to choose. Many are conformal in nature and replicate surface geometry and finish. Many, too, resist thermal oxidation and can wear well. But what about release? You know, actual non-stick properties, like an egg cooked in a fry pan?
The answer for injection molding is not lubrication. And here is why.
Lubrication is defined as a means to reduce friction or wear. That is true. But it is meant to be a substance between two bodies in relative motion, a load bearing interface between two solid, cohesive surfaces. And that is not what you find when you heat the mold surface above your material glass transition temperature (Tg). Which is why hard coatings designed exclusively for lubrication fail.
Depending on the compounds you are molding, ‘sticking’ failures can manifest in a number of ways: skinning, loss of polymer mobility, lower gloss and surface roughness. Hard coatings ‘with lubrication’ can negatively affect heating and cooling which, alone, can alter depth and visibility of weld lines.
On the other hand, hard coatings for non stick can make significant improvements to finish. Surface flaws can be eliminated. And that means no more painting. Structural imperfections, too, like molded in stresses, which lead to warping or distortion, can be a thing of the past.
Unfortunately, mold makers who have had negative coating experiences are reluctant to re-consider. No different than those currently experiencing satisfactory but marginal performance. Why change, they say. Especially when you believe you have tried or know about all the coatings available, today, like plating, Teflon or PTFE, PVD or PACVD.
So, where is your answer? Just ask around. You will not have to look far. The answer, you will discover, is with those who understand surface forces, the characterization of adhesion, non stick coatings for injection molding.
Post time: 02-01-2017