Polycarbonate or acrylic sheet?

[Monkey Mark]

I don't have much experience of either of these really.

I'm hoping to build a couple of things that I may decide to use one of these materials for a curved front/window.
I have read the differences between them with regards to scratch resistance, fading etc. But nowhere could I see anything on either their flexibility or how they react if heated when bending.

Can anyone shed any light on this please?

Cheers, Mark

 

[Lons]

Hi Mark

I assume when you say polycarbonate you mean solid sheet not multiwall as used on conservatory roofs!

There are many differences between polycarbonate and acrylic and much depends on how much of a radius you need on your window, what thickness of glazing material you envisage, size of unsupported plastic, how deep a rebate to fix, method of fixing, security issues and possible abrasion problems. Add budget to that as poly is more expensive like for like.

Thickness will determine radius possible and vise versa. Unless a tight radius you don't need to heat either but both possible as they are thermoformable plastics.

Acrylic is more rigid than poly but also more brittle. The flexibility of poly is one of it's strengths and preferable for security but because of that it scratches more easily, (there are variants with a coated surface to improve that), however because of the flexibility it needs a deeper rebate and ideally some mechanical fixing, it can also be attacked by solvents so care is needed. Note that both materials have one surface coated to protect against UV degradation so have to fixed that side out.

Plenty of information out there especially from ICI / Perspex or if you go on to the Amari Plastics site they have quite a bit from memory though will be Makalon rather than Perspex it doesn't matter. They have a branch on TVTE next to the retail shopping centre which is probably your nearest outlet, not too far away and the right side of those bl**dy roadworks for you. Also Bay Plastics just North of the Tyne Tunnel carries a lot of stock and have knowledgeable staff.

If you post some details of your project I might be able to offer advice as will others on the forum.

cheers
Bob

http://www.amariplastics.com/
http://www.bayplastics.co.uk/

 

[Monkey Mark]

Hi Mark

I assume when you say polycarbonate you mean solid sheet not multiwall as used on conservatory roofs!

There are many differences between polycarbonate and acrylic and much depends on how much of a radius you need on your window, what thickness of glazing material you envisage, size of unsupported plastic, how deep a rebate to fix, method of fixing, security issues and possible abrasion problems. Add budget to that as poly is more expensive like for like.

Thickness will determine radius possible and vise versa. Unless a tight radius you don't need to heat either but both possible as they are thermoformable plastics.

Acrylic is more rigid than poly but also more brittle. The flexibility of poly is one of it's strengths and preferable for security but because of that it scratches more easily, (there are variants with a coated surface to improve that), however because of the flexibility it needs a deeper rebate and ideally some mechanical fixing, it can also be attacked by solvents so care is needed. Note that both materials have one surface coated to protect against UV degradation so have to fixed that side out.

Plenty of information out there especially from ICI / Perspex or if you go on to the Amari Plastics site they have quite a bit from memory though will be Makalon rather than Perspex it doesn't matter. They have a branch on TVTE next to the retail shopping centre which is probably your nearest outlet, not too far away and the right side of those bl**dy roadworks for you. Also Bay Plastics just North of the Tyne Tunnel carries a lot of stock and have knowledgeable staff.

If you post some details of your project I might be able to offer advice as will others on the forum.

cheers
Bob

http://www.amariplastics.com/
http://www.bayplastics.co.uk/

Cheers Bob, what a fantastic answer!

I think for mu currently planned projects either would be suitable, but i like to know these things for future reference.

As for my current ideas there are 3 really.

First is simple. Just some replacement windows for a kids playhouse.

Second is for a planned thien baffle. Space permitting I'm going for a top-hat design with clear sides so i can see any blockages.

Third is a sub box for my son. Rectangular box with a window that wraps around from left side, across the front then right hand side. The window would be recessed into the back of the front casing (if that makes sense) Radious for the corners not yet determined but they needn't be too tight.

That's my little projects at the moment. Any pointers greatly appreciated.

 

[woodpig]

Acrylic is quite brittle and easily broken, I'd never use it by choice. Polycarbonate and Polyester (PETG) are much tougher and would be my choice for a playhouse.

 

[woodenstx]

Polycarb for the kids windows!

Perspex/acrylic is horrid stiff when you smash it as it effectively behaves like glass and goes to sharp shards. Polycarb is soft and lovely if you manage to break it (we use it to replace the side and rear windows in race cars :lol: )

for the baffling, perspex will probably do

For the sub, I'd go polycarb again for its strength etc.

 

[Beau]

Hi cast acrylic is pretty good stuff. Made some windows for a boat some 10 years ago and they have been fine but on a very slight curve. Used both polycarbonite and Acrylic in the past and both were tough with the polycarb being exceptionally so. The hi cast acrylic scratched less easily and was more glass like to look through. I have loads of 250x250mm spare squares of 5mm Hi cast from a science project that got canceled so if anyone can make use of them would part with them for beer money.

 

[Sheffield Tony]

But nowhere could I see anything on either their flexibility or how they react if heated when bending.

Something to be aware of - unlike acrylic, polycarbonate absorbs moisture from the air. This can make it bubble as the absorbed water evaporates when heated to bend it.

 

[Claymore]

I have used both on my vacuumforming machine and for vacuumforming the Polycarb needed to be dried in a oven for 2hrs to get moisture out and then moulded quickly on my machine... you had one chance per sheet and very expensive too but was VERY tough stuff..... quite brittle to cut on the guillotine too,If you don't get the moisture out it blisters and is ruined. Acrylic is lovely stuff to vacuum form but I wouldn't use it for the kids stuff.

 

[Lons]

I'd use poly for the kids playhouse as said if the cost is acceptable, if not too large, you might get some offcuts or if up my way (North of Morpeth) I might be able to help though likely to be scratched material as it's 25 years since I was in the plastics industry. PM me if you are!

It's unlikely you'll need to heat poly to bend it for your purpose so no worries about bubbles forming. There are charts online giving recommended radius bends by thickness, I might still have those in my files. One thing I didn't say is that if fixing mechanically you can't drill close the the edge, ideally you want to be 10 - 12mm or you'll risk possible fractures. personally I've drilled much nearer for my own use without issue. There's a very strong 3M d/s tape available which worked very well when replacing glass with poly in metal bus shelters and avoided the need to mechanically fix.

Just as an aside, we used to fix a sheet of 900 x 600 x 6mm Lexan into a wood frame and invite people to attack it with a 10 lb club hammer, No one ever managed to break it though pretty well scratched. I tested the same rig as a lecturer at college on some enthusiastic 19 year olds determined to prove the teacher wrong, they never did :lol:

 

[user 19915]

Sorry to high jack your post but as we are on the topic of : Polycarbonate or acrylic sheet?
Can i ask what would you use for a cold frame if any
Mock

 

[woodpig]

Acrylic will probably let more light through than Polycarbonate so would be better for a cold frame. Just be careful with it.

An easy way to distinguish between the two is that if you look at Acrylic edge on it appears grey whilst Polycarbonate looks Purple. Don't know about PETG but don't discount it as some places sell it in place of Polycarbonate in some instances.

 

[Beau]

Sorry to high jack your post but as we are on the topic of : Polycarbonate or acrylic sheet?
Can i ask what would you use for a cold frame if any
Mock

Defiantly go for Acrylic. Much cheaper and more than tough enough. Surprised others don't think it tough enough for a window in a kids play house as it's hard to break unless smashing it with a hammer.

 

[Lons]

Acrylic will probably let more light through than Polycarbonate so would be better for a cold frame. Just be careful with it.

My memory suggests that isn't really the case woodpig though I'd have to do some research to be sure. In like for like clear sheet of equal thickness there is only 3 or 4 % difference in favour of acrylic so negligible and impossible to detect without specialist equipment.

EDIT: Just had a quick look and acrylic shows around 92% and polycarb 88% of clear glass while 6mm twinwall is around 85%, that's just one source though and different manufacturers may be not be the same. We sold GE Lexan

However, my recommendation for cold frames would be to use cheap twinwall polycarbonate for cold frames. Must use the clear variety and has to be installed with the UV protected side out. Many years ago I did some research for a local agricultural college who suffered frequent glass breakage and supplied 6mm twinwall sheets.
This material looks as if it won't let much light through but again from memory it was actually around 80% + and additional benefits were that it diffuses the light to give a more even spread and gives superior insulation. It is exceptionally light and strong. They bought some 4mm and 10mm sheets as well but did their own trials.

cheers Bob

 

[Monkey Mark]

Thanks guys. I'll likely go for polycarbonate for the three projects as i might as well buy one bigger sheet and hopefully keep the cost down.