Thursday, February 25, 2010

Purging Tip of the Week: #2

At the end of a shutdown purge, we recommend running the system empty before you cut the heats and go home. This is as opposed to leaving the barrel full of purging compound.

There are folks who are concerned that this will leave the metal surfaces inside the barrel vulnerable to corrosion but that's not the case. Those metal surfaces will still be coated and "sealed" by a protective layer of purging material.

The advantage to be gained from this procedure is that you’ll save time at startup. The system will get up to operating temperature more quickly when you don’t need to heat and re-melt a full barrel of material.

Tuesday, February 23, 2010

How Others See Us

Since you're visiting here, you probably spend every work-day involved with plastics. Thermoplastic materials are part of our lives and hold no mystery or menace for us. But, as part of preparing for this blog I did a search on Google News using the terms "plastics, polymers". Some of the results offer a window onto how the world outside of our industry views what we do. For example:

Clearly there's a lot of negativity in the "outside world" about our stock-in-trade. The same pressures that were applied to phthalates and PVC are being brought to bear on Bis-Phenol A and polycarbonate. Bans, fees and taxes on polyethylene bags are being proposed and imposed in more and more jurisdictions. And in a more hopeful vein, the mainstream media sit up and take note of developments in "greener" polymer technologies.

It's important to bear in mind that facts and logic play only a subsidiary role in this battle for mindset. What matter are broadly held perceptions. And it does no good to for us to tell one another that the benefits plastic materials bring to society vastly outweigh their potential for harm. That's called "preaching to the choir!"

Now, it's not that there's an existential threat to our industry. Plastics aren't going to "go away." But there is a question as to whether we can expect historic levels of growth in the coming decades...whether plastic solutions will be among the preferred options or confined to legacy applications and "last-resort" status.

If we'd prefer the former state of affairs to the latter then we have to PAY ATTENTION, starting right now, to the perceived societal and environmental effects of all our decisions. We need to get out in front of the problems by considering all impacts of our products and processes. As an industry we will have to embrace life-cycle stewardship.

This is going to be a long story, lasting for the rest of our careers. It'll be a lot more fun to watch if we're proactive rather than reactive. So - what can we do today?

Thursday, February 18, 2010

Purging Tip of the Week: #1

Most processors, when changing materials, will run the succeeding materials "back-to-back" - that is, by putting the following material right on top of the preceding material in the hopper. It turns out that this is not a great idea when using a purging compound. It's a better practice to run the machine dry, then introduce the purging product into the nearly empty barrel of the extruder.

The reason for this lies with the marvelous effectiveness of the modern plasticating screw as a mixer. If the purging compound is run back-to-back with the production resin, the screw will mix the daylights out of them, thereby diluting the purging compound and reducing its effectiveness.

We makers of purging products go to considerable trouble to formulate an effective material and it doesn’t help to dilute it with the remnants of the production resin.

To Begin With...

Welcome to NOVACHEM's blog! We're going to use this space to post observations that are specifically about purging problems and practices, and more generally about polymer processing and the plastics industry.

Please feel free to comment...we will value your contributions. It's our hope that we can make this blog informative, entertaining and occasionally provocative (after all, if not why bother?)