Plastics that dissolves in water?

[Winniepego]

Hi,

Thanks for reading this!

I have discovered that PVA (polyvinyl alcohol) is a form of plastic (more like a film form) that dissolves in water depending on the temperature and the PVA concentration, it is often use in the fishing accessories to packaging and washing powder etc. I wonder if there's other plastics that also dissolves in the water but can be produce in the injection moulding or a form of vaccum casting?

PVA tend to have a very narrow thermal window gap so it cannot be produced in the injection moulding as the molten PVA will contact the cold surface die tool and solidfies quickly before it started to move and fill the mould cavity within making itself very vicsious. I wonder if there's such water soluble plastics that has got a good brittle resistant strength and compressing strength.

It is interesting to hear from everyone's shares and experiences!

 

[Demon3]

There are many water soluble polymers inclucing: poly(vinylpyrrolidone), poly(ethylene oxide) and carboxymethyl cellulose but, as far as I know, none are injection moldable. In 3D printing sometimes they use a water dissolvabe support polymer but I think that's not actually water soluble, it is a polyester that degrades when put into very alkaline water so the polymer molecules are degraded into small fragments rather than dissolved.

Chris DeArmitt - PhD FRSC

Plastics & Materials Consulting

http://www.phantomplastics.com

Plastic Training Seminars

http://www.plastictraining.com

 

[ornerynorsk]

Demon3, we have such a printer with dissolvable support material. You are correct, we keep the bath at pH ~12.6, and heat it at 70c. That, together with agitation fully dissolves the material in about 4 hours.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Paulkuklych]

Polyvinyl Butyral is injection moldable and water soluable.

Paul Kuklych

http://www.improve-your-injection-molding.com

 

[Demon3]

According to what I find online and also a friend of mine who works a lot with PVB it is not water soluble.

Chris DeArmitt - PhD FRSC

Plastics & Materials Consulting

http://www.phantomplastics.com

Plastic Training Seminars

http://www.plastictraining.com

 

[Paulkuklych]

Please take a look at this grade of PVB it claims to be water soluable: Mowital BG 14 S. My apologies if the information is wrong but are we talking about the same thing: water soluble and dissolves in water? The original question asks about a plastic that dissolves in water.

Hope this helps.

Paul Kuklych

http://www.improve-your-injection-molding.com

 

[Demon3]

If one were to hydrolyse a PVB to the point where it's almost polyvinyl alcohol then it would be water soluble. For the commercial PVB grades, they will not be polar enough to dissolve in water. See here for example, even when soaked in water for 24 hours, the PVB grades only take up 5% water. If they were soluble they would take up 100% or more.

http://www.kuraray.us.com/wp-content/uploads/2013/09/MOWITAL-TDS.pdf

Chris DeArmitt - PhD FRSC

Plastics & Materials Consulting

http://www.phantomplastics.com

Plastic Training Seminars

http://www.plastictraining.com

 

[Pud]

I have heard (but not tried it) that chocolate can be injection moulded - the screw shearing being enough to make it mouldable.
I think PEG is water soluble, but no idea if mouldable.
Most waxes will melt in hot water, as will some metal alloys.

Application would be useful to know.

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.