What material(s) I can use to make this kind "hard" waterproof board at home?

Question

I need to make L plates (it is used for learner motorcycle riders in many countries) at home.

Previously, I made it using a thick 250 gsm paper. I got L printed on it. But with time it faded and when I washed my bike, it got ruined. The color and paper became useless.

Then I found another solution to fix the color problem. I didn't print it this time. I got a red colored tape. And pasted it on the paper. It solved the color problem.

But still the paper is not waterproof and I need slightly more thick board. Something like 300 gsm would be perfect.

Here's an example of what I would need: https://youtu.be/YYi_ZqrJycA?t=48

In this video, you can see the board is thick and I feel it's not some cardboard. So it is most probably waterproof too. He tried to twist it. It was very flexible.

I want material like that. I could not find it online. Maybe I don't know exactly what to search for.

The closest material I found out was this - made from some PVC material. But it is very small. I need at least 18 x 18 cm.

So are there any other alternative material or solution to make this kind of board/plate?

Answer 1

I've often seen on a couple of YouTube channels the practice of recycling plastic bottles by melting and applying pressure in a form. It's HDPE and carries a number two recycle symbol. One useful video covers most of the details involved.

An inexpensive toaster oven is frequently used to bring the material to the correct temperature, which is then poured onto baking paper. A plank or other suitable pressure plate is applied while the plastic cools. The video shows the use of a flat plate sandwich maker type appliance and a silicone baking sheet.

The only complication I envision is that the material does not bond well to anything other than itself. This might require that markings be placed on the base (white) board, comprised of the same material of a different color, then heat and pressure applied to melt the markings into place.

Very much waterproof and sturdy as the thickness can be adjusted by the creator.

Answer 2

Deviating from previous suggestions into one that would require some extra legwork, but would avoid risk of fumes or burn injuries/damage, I'd suggest closed-cell PVC foamboard, frequently known by the genericized brand name "Sintra." While buying it new can be a bit costly, you can typically get smaller pieces of it for cheap, if not free, from local sign printing businesses, as its common use is for outdoor signage. I've been able to source a wide variety of scraps in multiple colors from signage shops by simply asking if they have scraps. It's durable, can be painted easily with any plastic-adhesion paint or primer, and is relatively easy to work using basic woodworking tools, so edges can be rounded off to avoid scratching paint on the motorcycle itself.

Answer 3

One thing you may be able to readily find, or salvage, is corrugated plastic board (looks like corrugated cardboard, but made from plastic sheet instead of paper). It's commonly used for things like signs because it's rigid and durable. But in terms of things you can make at home, here are a few ideas to add to fred_dot_u's suggestion.

• Fuse plastic grocery bags into a stiff panel. Start with white bags, and cut off the printed area, which will show through. Cut off the bottom seam and the handles so you're working with a rectangular sheet. Fusing a lot of layers can make a sheet that has stiffness close to something like a plastic "manilla" folder. That's typically done with the bag layers between sheets of oven parchment and an iron at a low to medium setting. There are lots of online videos about fusing plastic bags.

  If you fuse with a high setting, the bags shrivel up and develop melt holes. But once a bunch of layers have been bonded at low heat, they maintain their size pretty well at higher heat (at low heat, the plastic softens enough to stick together with some pressure; at a temperature high enough to actually melt the plastic, it will behave like melted plastic, so don't get it that hot unless you're fusing layers thick enough to not develop melt holes).

  If you want something pretty rigid, like the example in the video in the question, you can make some panels as described above, then stack those between oven parchment and melt them together and press them in something like the food grill shown in the video in fred_dot_u's answer (probably not a good idea to use the grill for cooking food afterwards).

  Note that it takes a ton of plastic bags, so you'll be saving the planet once you collect enough. After cutting out the printed section, you can fold the resulting sheet so you're working with multiple layers. It can easily take a dozen of those to get a stiff panel. Fuse no more than about eight layers at a time, ironing one side, flipping it over and ironing the other, and repeating until it's fused.

  You can start with several of these panels and fuse them together in a similar fashion using slightly higher heat, and flipping the sandwich repeatedly so the heat migrates through and softens the mating faces in the middle. Once the panels start getting thick, it becomes more practical to fuse them together into even thicker panels using something like a food press.

  Be sure to cover the sandwich with something like a heavy book until it cools to room temperature because it warps and curls otherwise.

• You can fuse layers of Tyvek if you're careful, but it will take some experimentation and practice. About eight layers of fused Tyvek starts getting reasonably stiff. Use only plain white because any printing will show through.

  Tyvek doesn't seem to go through a softening stage like plastic bags, where the layers will stick together with a little pressure. When it reaches a certain temperature (a low setting on an iron), it will shrink a a bit, and then the layers will melt together. Starting with white Tyvek, the fused sheet becomes translucent.

• Make panels from HDPE jugs. Gallon jugs from milk, vinegar, bleach, household ammonia, and some other stuff are usually HDPE, and bleach and ammonia jugs, and sometimes milk jugs, are white. You should be able to cut panels of about the right size. If you start with a round jug, you can flatten the curve in the cut sheet by warming it slowly on both sides until it softens a little. Then lay it on a flat surface and cover it with some books until it cools.

  If the jug wall isn't stiff enough, cut several panels and stack them. If there's still a little curvature, put them back to back so they curve in opposite directions. Then fuse the edges together by running a soldering iron or hot knife along the edge (no need to melt the entire sheets together).

  If you're working with translucent sheets and need white, you can stick a piece of white paper between them (don't go all the way to the edges that you need to fuse). You can fuse three sides to create a pocket, insert the paper, than fuse the last side. You can create the "L" on the paper or stick tape on the inside of the sandwich.