Is it polypropylene ?.

I’m looking t make a guard that goes from the lower end of the swingarm up to the rack, and needed to fit between the stays and the tyre, but all the current types are too stiff. I’m also finding most standard guards are a bit on the narrow side so maybe if i just bought a sheet of this stuff i could custom cut something that would suit better.

Its this type.

Can you adapt a crud catcher?
( the down tube sort)
It’s sorted me out , especially the ones with the rubbery front edge.

Flexible chopping board 🤔. That’s what I made mine from. Think I bought it from a high street discount store with lots of X’s in the name?

I was once told that plastic supermarket milk cartons are ideal for DIY flexi mudguards , however the choice of colours is a bit meh .

Polystyrene (not expanded) sheet, HDPE?

I’d just go and have a poke about the various packing items in your fridge and cupboards, see what feels about right then look at the marking to see what it’s made from, you can normally find sheets of most common plastics online.

… plastic supermarket milk cartons are ideal for DIY flexi mudguards

They’re okay for the mudguard image in the OP, the natural folds can be incorporated in the design. I tried one for a mudflap below a front mudguard but the shape was too flat/flexible and it blew onto the tyre in a crosswind.
I’ve also seen brick DPC strip used which works better as a mudflap

Polystyrene (not expanded)

HIPS is too brittle.
Most likely PP sheet, or maybe HDPE.

I’ve also seen brick DPC strip used which works better as a mudflap

That sounds like an idea for extending the road mudguards for a bad winter ride, my mate is a proper twunt for not using long enough winter guards, why do some people just ‘not get it’ ?

Can you adapt a crud catcher?

No, too rigid. And its pre-formed shape was causing problems fitting. What i want it to do is form around the inside curve of the seat stay brace, so it really needs to be flat and flexible.

DPC strip

Too flexible.

Flexible chopping board

Most seem to start at 3mm which is just too thick for form easily. The normal mudguard type is polypropylene, so im going to opt with that. I can get 600mmx3000mmx1mm from ebay for about £14

Most likely PP sheet, or maybe HDPE.

It would be PP. HDPE is too rigid,that pretty much what they make chopping boards out of. It can be thermal formed, but not what i need for this job. 1mm PP is likely going to form better as its going to be a complex curve. ie wheel shape, plus curve to the stay shape.

I’d just go and have a poke about the various packing items in your fridge and cupboards

I havent actually checked, but im sure its a type of PP.

Thanks all. Pretty much got the idea now for what i need, and ebay looks like the place to get it.

If you want something that you can form into a permanent shape you could try using a piece of kydex for this too.

I made one from an IKEA chopping board. Only about 1mm thick, flexibility about the same as a commercial mudguard.

I was up in the garage earlier and happened upon an old Btwinn foldy fender that still had it’s sticker on, and it PP, so. A sheet of 1mm poly prop should do…

I used a coloured transparent plastic A4 ring binder from Tesco to make guards like that in the past. Thin enough and durable.

Have a look at priplak. It’s a pp sheet material available in a range of thicknesses and colours.

Those type of mudguards are made from polypropylene co-polymer. It will have LDPE in the mix, low density polyethylene, to give it more flexibility and better impact resistance.

I used the plastic card my knee pads came on.

ive used DPC brick strip, and its fine.
Milk carton rips too easily, and looks like milk carton.
I dont find the DPC is too flexible, though i havent gone super long, and it is supported by the curve shape it is formed into.

I wouldnt go buying a big roll of it though, i only used it cause i had it lyaing around.