Repairs to Polystyrene fridge Parts

[Tim W]

Briefly: Perfectly good Fridge freezer has lots of rubbish clear plastic internal parts like this door shelf:

which the whole thing is pretty much a chuck out.

Model is discontinued, parts are unavailable so I am repairing again.

Previously repaired some broken polystyrene parts by patching with polystyrene from CD boxes and plumbers' solvent adhesive. These repairs were only partly successful, having lasted more than twelve months the polystyrene has become crazed and crumbly and cracks are opening up again.

I was proposing to repair this time with epoxy resin in conjunction with wood stifeners, plastic patches or maybe glass mat.

Will epoxy resin soften and destroy the polystyrene I am trying to repair? Is there a better way to repair these things?

I know it's polystyrene because it is marked PS.

Tim W

[Donwill]

If I remember rightly the solvent for Polystyrene is Benzene, nasty stuff.!! Don

[Chris K]

Do you really mean epoxy or are you referring to the car body repair kit stuff more widely available. The 'glass fibre' kits from Halfords etc are largely stabilised styrene monomer that is persuaded to polymerise with the hardner. This should bond well to polystyrene unlike the pipe solvent adhesive.

I'd try using the same technique as you used before but using the car body filler kits (without the powder filler).

CD case material is a bad choice as it is pure polystyrene and subject to stress cracking and crazing. The polystyrene sheets available in the sheds would be better. Glass fibre matting to add further strength would probably help but look a bit of a mess..

HTH

Chris K

[John Rumm]

Glass fibre tissue would probably be a better bet - like mat but a much finer finish.

[The Natural Philosopher]

hot glue.

as a model aircraft buff, the fast ways to repair PS have all been tried.

PVA works, but takes ages to dry. Epoxy works, but is bloody expensive Odourless CA works, but its enormously expensive and wont fill gaps. Ordinary CA will reduce styrene to mush. some contact glues..thixofix? the latex ones that smell of ammonia work pretty well. No gap fill Hot glue works briliantly, and ripped apart models will be flying in minutes. stronger than the plastic is, fills gaps and glue melting point JUST below styrene melting point.

[The Natural Philosopher]

almost anything dissolves polystyrene, but that is the last thing you want to to with EPS.

[Tim W]

Thanks Chris. I have a small quantity of industrial type epoxy resin and some glass tissue/mat (no filler/thickener) in the shed left over from some wood/boat type work so I was going to use that, not polyester or any car body kit.

Will the epoxy i) bond well to the polystyrene, with or without abrasion or solvent cleaning.? ii) desastrously soften or dissolve the existing polystyrene.?

I know it's a fuss over a bit of plastic shelf but it takes some quite hard use with teenagers in the house and if I can't mend it the fridge is barely usable.

Tim W

[Tim W]

Thanks John what I have to hand is proper epoxy and some quite fine glass tissue in fact not mat

Tim W

[Tim W]

[...]

Hot glue. Excellent. I will try it. Thanks.

Tim W

[The Natural Philosopher]

no. It partially dissolves it.

Epoxy is inert.

butt glue cut blocks with hot glue. Its that simple.

shed 'white' polystyrene is better insulant that pink or blue extruded, but any material works.

Cut with sharp knife and or sand 'gently' small saw - tenon - also works.

[The Natural Philosopher]

ultra light cloth is best of all.

[The Natural Philosopher]

not well, but well enough.

No.

thiought this was EPS, not a shelf?

[Tim W]

Thanks

Not EPS but Clear >PS< as above. Sorry for confusion. Now I think about it the idea that hot glue could be the best repair should have set off the alarms. No hot glue, epoxy it is. Thanks

Tim W

[The Natural Philosopher]

For CLEAR styrene go and get plastic model kit cement from a model shop.

And ignore everything else I said.

[Chris K]

If it really is epoxy, suspect not, particularly with temperature cycling, but you never know.... I thought some boat resin work was PS based. Does it smell strongly? Epoxies generally do not.

You really need something that dissolves PS to bond with it properly like the old PS cements for Airfix models, that is before they changed the solvent (Trichloroethane IIRC) to make glue sniffing unrewarding. The current stuff does not seem to be anything like as effective.

The waste pipe cements are meant for use with uPVC pipe & will not work well with PS.

Chris K

[Huge]

I've mended several shelves in our fridges with hot glue. Works a treat. If the joins are load bearing I sometimes "stitch" them by drilling holes across the crack and putting cable ties through the holes.