injection molding PVC

All our molds were made of stainless steel, can still rust from the HCL but will take longer. Clean your molds well and use rust preventive too.

Purge barrel with a GP ABS after PVC, never leave PVC in the barrel.

Add radius whereever you can in the part design as well as your runner system. This will help reduce shear also. We also used peripheral venting whereever we could on the part, as well as vented the runners. PVC gases easily.

Alot of this we learned from our PVC supplier (decades ago, BFGoodrich, they later became Geon.) PVC has a bad rap unfortunately; but Goodrich taught us (and we were willing to listen and learn) that is it not a bad material at all, if you run it the way it needs to be run, you will have no problems (we didn't for the 11 years I stayed with that company). I agree with what everyone else said too.

I've was new to this process as well and the few things i've noticed. If the part you are molding is thin walled , there will be a problem of silver streaking.Get a good balance between injection speed and the mold cooling. Also The HCl formed during pvc molding can cause the mold to rust real soon and in no time you will have problems because of the acid vapor, the solution for this would be use mold material that do not react with hcl or get the mold platted.

vachan

I've read some really great articles about uPVC windows for homes. I would suggesting clicking that link i provided and i hope this would help you on injecting molding parts out of PVC. Good luck!

Before you buy something I think you have to research first about it and ask experts. You can even ask the sales boy/girl for it so that when you use it you will know what to do. Actually there are guides here about uPVC windows guide.

The assistance you seek is easily available on the internet. More Specifically on IDES.COM, Or any major PVC supplier. If you're new to this business you know more about the internet than us knuckle dragging luddites who grew up reading paper.

Do your keyboard thumping.

If you follow their guidelines and still have problems, THEN ask the question on this forum.

Bill

i am new with seting up to run pvc on injection molding . so i need some advices please help .

What are general processing parameters for PVC? I am running a WIDESPEC material. Barrel heats, melt temp, mold temperatures
I'm assuming slow screw and injection speed and low back pressure.
How should I purge after running PVC?
Thanks to everybody for all their help.

What is HCL?

You were cautioned about degadation and nasties if allowed to really degrade. It really smarts the eyes and nose/lungs if you screw up !!! Good ventilation helps with that but also one or the byproducts of degrading is HCL (now airborne) and the fact that any non-plated steel is subject to attack. Once the HCL gets free - look for rust on everything nearby (ie. tiebars, platens, molds, nearby presses, etc.)

Should there be a draft hood above the machine that is running the PVC?

Use a low compression screw with free-flow check ring with either flexible or semi-rigid PVC. Keep residence time and shear to a minimum. Use the lowest barrel settings possible. Never let the melt set over 5 minutes idle, if its going to be longer put the heats in standby.

Don't mix with acetal !

I agree with Bill, get some info. from the material supplier.

On an important side note. *** DO NOT MIX WITH ACETAL AND HEAT UP *** Will cause violent reaction.

There's nothing particularly magic about PVC. People do it routinely. However if you are sloppy with it - overheat it - it degrades into some exceptionally nasty chemicals.

Follow directions and you're fine. Don't follow the tech data and you're in trouble.

This is probably good advice for any plastic you're molding.

Bill Tobin
WJT Associates.