I need to do a little repair work on my interior panels. I have a plastic welder and want to try and fix some cracks, but I need to know what the original plasitic is.  Does anyone know is it Polypropelene or ABS or PVC?

 

Thanks

 

Steve

Do they have any numbers or symbols on the inside. Newer parts have codes on them to identify the material. I don't remember if the original panels do...

C

Not sure what they are but I used fiberglass and epoxy to repair all the plastics in my blue on blue 71'  Worked out very well. 

Edited April 14, 20159 yr by er34gtt2000jp

I don't think it's any of the above.  It's 70's era, stiff and it likes to crack.  That indicates styrene (or polystyrene, if you like) -- same as plastic model kits.  I'm not optimistic about repairs of thin styrene sheet using a plastic welder.  There are several old threads about repairing cracks in these panels.  The accepted wisdom is to use a glued-on bridging sheet, applied strategically on the inside (hidden) surface.  An old credit card or hotel key card is about the right thickness and flexibility.  JB Weld (5-minute type will be ok here) recommended, although Gorilla Glue might be a good alternative (good bond, more flex).  If you use JB Weld, score both glue application areas with a single-edge razor blade (cross-hatch pattern) in order to give the glue some 'traction' on the shiny surfaces.

I've had good results repairing plastic air ducts in the engine bay using screen door material as a backing along with a mixture of Shoo Goo and POR15 thinner to make spreading easier.  I plan to use the same technique on any plastic interior panels with may need the same attention.

Interesting, thanks for the input.

 

My cracks are relatively small, less than an inch and are around where the plastic rivets hold them in place. I was planning on melting in some fine stainless screening on the back and then supporting it with additional source plastic. Filling and refinishing the front will be a different project that I'll take on when I'm ready to repaint the entire interior.

 

I may sacrifice my back speaker panel and use that plastic as filler. I can test to see how it melts, I’m a little worried that the panels aren’t all original as some are all white and some appear to be painted black panels. Hopefully they are all mad of the same plastic.

 

Steve

Curious to try this stuff from Loctite on interior repairs:

"A two-part cyanoacrylate adhesive that sets in seconds and develops tremendous strength with just one drop. The activator primes hard-to-bond surfaces such as polypropylene and polyethylene.

Bonds leather, cork, paper, cardboard, wood, chipboard, fabric, metal, ceramic, rubber and plastics such as Plexiglassâ„¢, polycarbonate, polystyrene, PVC, polyethylene and polypropylene"

 

User reviews are mixed, but several people complained the glue hardened in the tube before they got it.