Plastics

[nc43bsa]

Does anyone here know how to determine what plastic an object is made from?

I'm attempting to repair a part from a 30 year old Cadillac that has been discontinued by GM, and I can't find a used part.

[cliffrod]

Smooth on offers a variety of products for production and reproduction, all professional quality product and support.  Check out their website for information about possible solutions to your project-
https://www.smooth-on.com/

Simple testing of product, although it may require sacrificing some of the original material-
https://www.twi-global.com/technical-knowledge/faqs/faq-how-using-simple-manual-tests-can-i-identify-an-unknown-plastic-material

[guzzista]

Well equipped body repair shops have pro  plastic welding equipment that can make for a perfect repair. Worth checking out.  As per mending, JB Weld Plastic Bonder 2 part epoxy does a great job  regardless of plastic type. When combined with  metal mesh backing or Simpson Tie perforated plate or similar DIY perforated  thin metal it can make for a super strong repair. My 30 year old Corvette was literally held together by JBWeld plastic bonder

[pehayes]

If you can make a reasonable bodge repair, perhaps the piece can then be cast in plaster or such and poured with new plastic.  I have a two part (powder and solvent) casting kit (Plast-Aid) that molds small plastic things hard as a rock.  Seriously strong stuff.  Watch here:  https://www.youtube.com/watch?v=1YGzjWeK-nY

Patrick Hayes
Fremont CA

[RinkRat II]

       Might check around your area for someone with a 3D printer, depending how big the part is.

       Paul B

[Paul_Tim]

Have a good look on the inside surface of the part, most automotive plastics have been marked with part number, manufacturing date code and a code identifying the material for the past 30+ years.
I've a set of fairing parts for a 32 year old Yamaha next to me in the workshop, they tell me it's ABS and I've two date codes 07-91 and 04-96 indicating that some have been replaced at some point in its life.

There are a number of websites with decoders for the material.

Good luck.

[Tom]

Check the reverse side of the part.  There should be some info about the type of plastic.  Check this out.  https://www.youtube.com/watch?v=lkaKLowAsrI  or   https://www.youtube.com/watch?v=0A9yvmLR-K0

[LowRyter]

Well equipped body repair shops have pro  plastic welding equipment that can make for a perfect repair. Worth checking out. As per mending, JB Weld Plastic Bonder 2 part epoxy does a great job  regardless of plastic type. When combined with  metal mesh backing or Simpson Tie perforated plate or similar DIY perforated  thin metal it can make for a super strong repair. My 30 year old Corvette was literally held together by JBWeld plastic bonder

that

[averb]

Toms suggestion is a good one, however if you can't find a marking and at 30 years old there's a reasonable chance you wont, try this chart - https://partec.qld.edu.au/wp-content/uploads/2018/08/Plastics_Identification_Flow_Chart.pdf  The one Cliff posted earlier misses out on quite a few materials commonly used in automotives

Cheers

Steve

[bigbikerrick]

This company Polyvance ,has a great chart for identifying plastics for repair
Rick.

https://www.polyvance.com/identify.php

[JJ]

Sorry...I could not resist....Classic movie scene...

https://www.youtube.com/watch?v=eaCHH5D74Fs

[Tom]

He says it's $16 from Harbor Freight.

https://www.youtube.com/watch?v=aIMl9vtRqPg

More plastic welding techniques. 

https://www.youtube.com/watch?v=7IMAtlPSORs