Heating Polycarbonate forms holes?? 3

[plasticnoob]

Sorry guys but i am not sure where i should post this.
I have a lot of polycarbonate parts with minor scratches so I try to remove the scratch by heating it.

Due to the lack of equipment, i was using a heat gun to heat up the polycarbonate hoping to reach its glass transition temperature. However i discovered that holes were formed instead. May i know what is the reason for this?

 

[patprimmer]

Because it melted.

flame polishing PC has several problems.

1) PC melt is very viscous so it does not tend to flow to smooth out.
2) PC absorbs water from the air over a reasonably short time. On heating this out gasses and forms bubbles on the surface and the gas also erupts like a mini volcano.


Using a hair dryer also has problems as it is a weak source of heat and the plastic transfers heat through its thickness due to the slow heating, this allows the material to melt all the way through. To flame polish you need to very quickly melt the surface while the matrix is still cold. A naked hot flame is the way to do that, hence the name, flame polishing.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[wongs9982]

put a pin inside the hole,
then use flame to burn the flash.

should repair the mold by welding.

 

[JMEMolds]

x2 on the naked flame, and for the same reasons. A heat gun / hair dryer simply isn't going to work.

J&M Enterprises
Thermoforming Tools

http://www.jmenterprises.net

 

[plasticnoob]

I see. Thanks for your help! i shall try using naked flame