Glueing the plastic on brake lever shell

[Tosher99]

Anybody know enough about plastics, glue or trial and error, to know how to glue a broken off part of the shell of my microshift brake lever. it's not load bearing, is a clean break but shiny plastic.

Thanks

[gaz]

Welcome to the forum.

Plastic cement (to build model kits) or superglue. If possible bridge the break with a thin strip of plastic to increase the contact area. Any mend is unlikely to be as strong as the original.

For the best advice, upload some pictures to help others understand exactly what has broken.

[Cyclewala]

Glue alone will not be strong enough to withstand the day to day wear/vibration. I repaired a trigger shifter base with glue and then covered with clear vinyl wrap over the two parts. It’s the vinyl that gives the real strength because it reunites the two broken parts into one unit. It’s similar to the chainstay protector.

EBay is a good place for small samples.

[Brucey]

somewhere on the lever body there ought to be some marks to tell you what it is made of; it may turn out to be a weldable grade of plastic, but in any event, knowledge is power.

[2_i]

None of the solutions below is economically justified for your one-off, but it may be a way to acquire tools for an arsenal employed over the long term. There exist plastic hot repair and rework kits marketed primarily for repairing plastic automotive panels. They can include an iron, staples, meshes, and plastic rods to be melted - think of an elevated hot glue set. Another higher priced option is polyolefin glues, typically 2-component, applied with a glue gun that you may see at the dentist's office. I went through both of those routes on different occasions with success in repairing parts bearing modest loads.

Most plastics employed in everyday life are characterized by low surface energy and require special adhesives and the mentioned superglue and hot glue are polyolefin bonders but may not be strong enough for your particular situation. The links for examples (search yourself for more) of the above are below.

https://www.aliexpress.us/item/3256803096420931.html

https://www.aliexpress.us/item/3256804074966407.html

https://www.glueonline.co.uk/product/pe ... 4610-50ml/

[JohnR]

Personally, I would roughen the surfaces to be bonded together and then use slow-setting epoxy resin glue (eg the original Araldite) then into a clamp to hold it together until hard (a warm place will accelerate this). Roughening improves the bond between the glue and the plastic and I prefer the slow setting epoxy as there's more time to get everything lined up nicely and I have a gut feeling that it's stronger than the quick-setting version.

[alexnharvey]

Epoxy is not very good on plastic, especially if you are relying on a mechanical bond (scratched up surface). Plastics like nylon bins so poorly to it that they are used as peel layers during composite construction (vacuum bagging and infusion) or the vacuum bags themselves (polyethylene i think).

I believe mma structural adhesives may be better for many plastics.

Some plastics benefit/require activators which enhance bonding.