For anyone who's cracked or broken a panel or other plastic part and wanted to repair it, there are two questions that have to be answered - first "What's it made of?" and second "What repair method should I use?"

To determine what it's made of, look on the backs of panels and other plastic parts. Here you will find somewhere near the part number, a code bracketed between these two symbols > < . This code tells you exactly what type of plastic has been used to manufacture this part. These codes are not really intended for the consumer, but for recycling purposes.

For anyone who would like some additional info on the types of automotive plastics, where they're typically used, and how recycling for the auto industry works, this document has some really good information -

Automotive Plastic Recycling
https://www.plasticsindustry.org/sites/ ... le-web.pdf

Plastic Codes -

>PC/ABS< = Polycarbonate/Acrylonitrile Butadiene Styrene [Glove Box, Parcel Shelf Brackets]
>PA6 GF50< = Polyamide 6, (Nylon) with 50% Glass Fibre reinforced (GF50). [Hood Release Handle]
>ABS< = Acrylonitrile Butadiene Styrene [Center Console parts]
>PA+ABS< = PA (Polyamide) + ABS (Acrylonitrile Butadiene Styrene). [Dash Side Panel that covers the fuse box]

As would be expected for parts that get hot or are subject to abrasion, you'll find codes to indicate additives in the plastics as is the case for the 2.0 TFSI Engine Cover where you'll find >PA6 GF10 M20<. And for the Under-body Splash Shield you'll find >PP-GM22<.

Additives include materials such as Glass (G or GF), Talc (T or TV) or Mineral (M or MF) which are added to increase desired characteristics of the plastic; e.g. glass fibers are typically used for additional tensile strength, talc is used as a stiffener and minerals are used for heat resistance and to minimize thermal expansion. The number-value suffix simply indicates the percentage of the additive in the plastic.

Some parts are composites where two different plastics have been bonded together. For the Roadster Side Flap Covers the primary component is ABS which is covered in vinyl and bonded to the ABS body. For parts like this where it might possible to repair the ABS, it's probably easier to just replace the entire part since the vinyl covering might be damaged during the repair.

In the case of the Glove Box Opening Damper, it's labeled "Out >ABS/POM<" , "In >POM/TPE/PA6+GF<". It's not until you open one up that you understand where all this is coming from. The outer housing is ABS/POM, but the inner piston assembly is POM/TPE/PA6+GF. So we have POM (Polyoxmethylene or Delrin), TPE (Thermoplastic Elastomer) and PA6+GF is our old friend Glass filled Nylon. Since TPE is a mix of plastic and rubber, it's a pretty safe bet that the TPE refers to the sealing ring.

As you can see, not all the plastic parts in the vehicle are made of the same plastics or plastic combinations and not every plastic part can be repaired. But now you can determine which plastic they're made of and determine the best method for repair. Below are a few PDF links on other plastic codes you'll come across and how to repair them.

Generally speaking, your typical hardware 2-part home epoxy won't work very well since it doesn't actually bond with the plastic. However there are bonding agents that will, but they are specific to the types of plastics being repaired.

Bonding -

>ABS< and >PE/ABS< can be bonded with ISP Weld-On 1707 or 4707 (the primary difference is viscosity). Bonding agents like these often incorporate acetone or MEK which will slightly dissolve the parent material, bonding or "melting" the parts together. This is why it's important to add more material to strengthen the repair either a bonding repair or plastic-welding the part.

While I have not used it myself, I have read good reports about "Tech-Bond Molecular Bonding System" from the USA. You can check out this video about how it works for rubber, insulation, PVC, polyethylene and Teflon -

https://tbbonding.com/
https://www.youtube.com/watch?v=v_v2EdyTQ84

Welding -

Plastic welding rods are very common and relatively cheap. You can pick up a pack of specific plastic welding rods (ABS, PC-ABS, POM, etc.) from plastic weld suppliers, eBay and Amazon. A pack of welding rods goes for around 5-10 GBP, and they can be welded with a common soldering iron as long as it can reach the melt temperature of the plastic. (Typically around 280°-350°C). Be sure to follow the instructions for crack prep and cleaning before you do the weld.

When welding rather long cracks, or around screw holes or anywhere there may be additional stress that might crack the part again, you can also add fine stainless steel mesh (like window bug screen) to reinforce the area.



Here's an interesting article on using a Dremil tool to friction weld plastic part together.
https://makezine.com/projects/make-34/s ... d-objects/

PDF on a wider range of automotive plastic repair -
http://people.okanagan.bc.ca/jfrancis/T ... s%2014.pdf

Source for plastic welding rods in the UK -
http://www.plasticsolutionsuk.com

Detailed information on automotive plastic codes courtesy of Scania trucks -
https://til.scania.com/idcplg?IdcServic ... 0000004_01


Lubrication for Plastic Components -

This topic comes up often in the Forum, and many people seem to think WD-40 is the best lubricant for everything. In fact, it may be more harmful than beneficial to plastics since it's petroleum based. ABS, Nylon and especially TPE do not react well to petroleum-based materials since some of these compounds can contain hydrocarbons in the form of alcohol, MEK or acetone which can destroy plastics.

Silicone and mineral-oil-based lubricants are they best choice since they won’t attack most plastics. White lithium is generally a good choice, just be sure it doesn't include zinc oxide, which is found in heat sink compounds.

Based on their plastics comparability chart (see below) the Super Lube® Synthetic Greases and/or Super Lube® Oils would be one option as they are are safe for almost all automotive plastics.

Lubricant Compatibility Charts
http://www.super-lube.com/files/pdfs/Su ... _Chart.pdf

Whatever you use, it's always a good idea if you don't know what's on the parts you want to lubricate, to remove what's already there first as best you can before you add a new lubricant. Mixing different lubricants can sometimes cause the combination to thicken or harden, thus reducing the lubrication effects.

Theres potentially a third question Swiss....."can it be soldered?"

viewtopic.php?f=19&t=1725297

Good write up by the way mate

@ Gaz78 Thanks! I was intrigued by the speaker panel soldering iron weld and figure I'd look into it just for my own knowledge. Questions about ABS plastic repairs come up now an then, and once I started digging, was surprised at just how many plastics and combinations of plastics are actually used throughout the vehicle.

But it was interesting to see just how many interior panels are combinations of different plastics used throughout the cabin. The real eye opener was just how easy most repairs are if you get the specific plastic welding rod and have a common soldering iron laying around. It puts to rest the idea of using epoxy glue to try and repair broken or cracked plastic parts.

Broke Door Card Grill....Now Repaired!
https://www.ttforum.co.uk/forum/viewtop ... &t=1725297

Glue + Paper always works for me. Best lube for plastic is MoS2 dry lube

Very interesting thread. Thanks for posting. Mentally filed for future use!

Another very helpful and informative post by Swiss, a big thumbs up