"Gluing" Lexan (TM)

[Ed Harrow]

One of my few friends asked my advice re: repairing a failed joint in the companionway hatch for his boat. I told him I had no experience, but there was a very good chance someone here would know.

The hatch broke at a joint, failing similarly to the way wood joints fail when glued with epoxy or the like, a bit of wood remaining attached to the epoxy.

Thanks - Ed

[Billy Bones]

You don't say what part is lexan. You seem to suggest that lexan is being glued to wood. Yes?

I used to use a chemical (sodium something-er-other?) that doubled as a parts cleaner, for gluing polycarbonates together. A bit in a syringe along the joint would weld the components together amazingly well. Several people here know alot about plastics and hopefully will chime in with the name of the stuff. For gluing lexan to wood I'd use 5200 or something similar.

hope this helps at least a little.

[shadow99]

Ed, what your buddy needs is a etching adhesive. 3M makes a product called "Scotch-weld DP8005" it's a 2 part epoxy 10:1 mix, with a special applicator. It's made to bond Lexan, polypropylene, polyethelene, & most thermoplastic elastomers, to anything. I used some several yrs ago on a machine tool, the fumes are quite nasty :eek: , so where a respirator. Grainger carries the stuff, other industrial suppliers might also.

Rick

[thechemist]

Different plastics require different solvent cements, and some do not dissolve in any solvent. Lexan, a polycarbonate material, is solvent-cemented with ethylene dichloride [EDC]. Usually one makes a solvent-polymer premix wherein one dissolves enough lexan sawdust in EDC to thicken it up a bit. This may be on the order of 40-50-60% by weight of polymer. You may need to let it sit for some days in a well-sealed container, opening daily to stir a bit, to finally get a nice syrup. Plastic pipe cements for PVC and ABS piping are made in a similar manner, but from different solvents.

[John Blazy]

Excellent responses guys - you are all correct in many, yet different aspects. I have years of hands on experience with solvent-welding of acrylics, PVC, and polycarbonates as well as to wood, particularly in my profession. The solvent-based epoxy Rick mentioned probably works very well, similar to a product called "Weld-on", and The Chemist is right on with a similar concoction, although we mostly use off-the-shelf pure solvent cements that have a mixture of Methylene Chloride, MEK and other fun beverages. These super thin solvent cements work great in that they wick into the joint, softening and "welding" by melting the existing plastic, as opposed to the possibly better solution of adding Lexan sawdust.

The real trick in bonding PC, PVC, or Acrylic to wood lies in what BillyBones hinted at. I did a production run of Art Deco hall mirrors some years back and needed to apply a plywood cleat to the inside surface of wood veneered 4" PVC pipe that held the whole weight of these hundred pound mirrors. Needless to say I was trusting the glue joint to never fail lest a three grand mirror crash in a clients home.
The cleat to screw into was 3/4" x 1" x 30" plywood and I did a number of test joints, and broke them to check adhesion failure. Did a few using pure PVC cement (pre-thickened like what the Chemist describes), a few using only PL Premium (polyurethane construction adhesive very similar to 3M 5200, a fraction of its cost, and stronger than @#$%) on scored surfaces and few - insert light bulb flashing over my head - where I applied wet Premium on the ply, laying into wet PVC cement on the PVC and clamping. The first two joints failed under moderate stress, and the wet-on-wet system simply could not be destroyed - total substrate failure, not joint failure.

The Mirrors hang to this day (at least the couple I have left)

So use this W-O-W system with a plywood cleat to the Lexan, and screw into the plywood. No chance of the screws cracking the plastic this way either.

[Dave Fleming]

Question: does Lexan expand and contract with the humidity as regular old Plexiglas does?
I recall making several 'venturi screens' for fishing boats out of blue plexi and had a number of failures before finding out about the expansion thing. Had WL Fuller make me some drills especially ground to drill plexi and had a saw blade made specifically for plexi too.
Things went much better after that. But it did not stand up to abrasion from harsh cleaners either.

[Ed Nye]

Use Weldon # 3, 4, and 16 to structurally glue Lexan. Read the thread from couple of years back

Gluing Acrilic (http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=003585)

Ed

[ 04-10-2003, 04:51 PM: Message edited by: Ed Nye ]

[shadow99]

Dave, Lexan is more temperature stable than Plexiglass, but it still moves alittle. It's more scratch resistant than plexi, & cost more too.
The drills used to make holes in Lexan/Plexi are only different at the tip of the drill. 118 degree drillpoint is standard, 135 degree for harder materials, plastics use 75-80 degree drillpoints with a thinned web at the drill tip.
You could grind them at home on a grinding wheel, and tune them up on a beltsander, with alittle practice and lots of patience :D .

Rick

[Ed Harrow]

Sorry I wasn't as clear as could be. This is Lexan/Lexan. When the joint failed, it was the Lexan at the joint that failed, not the bonding agent.

Thanks folks. Ed

[Dave Fleming]

This is Lexan/LexanUnderstood Ed, was just doing some mild hijacking to hear what others had to say about my long ago problems.

And yes I know about grinding drill bits but was never good at it. Was much easier and almost faster to have Fuller make me a 1/2 dozen ground properly. Now I have a Darex 2500 so can grind accurately all I want.
<insert winky gloating grin here>

[shadow99]

Boy Dave, sounds like you have all the fancy toys.
Darex 2500 huh, how many cookies that set you back? Unfortunely I never had the "privilage," of using one of those fancy drill grinders. I learned the hard way, boss handed me a box of assorted diameter drills, (right & left hand) :eek: OOps. He told me to sharpen all of them, he inspected every drill (there was many rejects). Two months later (having sharpened every drill within reach, everyday), I was told I was a pro, and was pro(de)-moted, to ENDMILLS :eek: :mad: !!!! Just what I wanted...
Someday when I get lazy, maybe I finally break down and buy one of those "fancy drill grinders."

:D
Rick

[Dave Fleming]

Rick, I got that thing about 1997 at a garage sale down here in 'insane Diego'. Just driving bye with SWIMPAL doing the driving, I was in my Rx drugged up period, and I spotted the sale with a ton of metal working machine tools. Had no space for a Bridgeport or a nice Colchester lathe so I spotted the Darex and innocently asked...how much for that thing and whats it for?!?
Fellow didn't know as he was selling for his mother. So I offered $50.00 USD he looked at it and said, nah gotta have $75.00 USD for it. I turned to SWIMPAL and batted my baby blues at her and she dug out the 75 clams. Hadn't been used at all! Complete with Borazon wheels, Diamond wheels, and collets for drills up to 1 inch.
We hustled that big packing box into the trunck of SWIMPAL's Passat and disappeared in a cloud of smoke.
<insert big ****e eating grin here>
PS: SWIMPAL reading over my shoulder says the Bridgeport was priced at,,,,,,,$1000.00 USD!!!!!
It was cherry too....sigh

[shadow99]

Ahh yes, a Bridgeport, no room in my garage for one of those yet :confused: . Luckily, I've managed over the past 10 years to convince the company I work for to increase the "usage" of our toolroom, (from a drillpress & bench grinder). To include 5hp mutli-speed Bridgeport mill (with power feeds on X & Y axes), a Harrison Gearhead 7hp engine lathe, Harig surface grinder, Citizen precision toolpost grinder, TIG welder, and other CNC's that we have in-house. The best part is I have full access to the facility (24/7), 7 miles from home (great for "Goverment-jobs.")
If I only had 3 phase power off my street I'd be set! :D

Rick

[stevenovascotia]

Rick:
If you ever really need three phase power for a machine it's now easier than you think. You can use an AC Drive to convert and have the added bonus of infinate speed control. 240V 1phase in, 240V 3phase out. I am soon going to convert all my stationary tools to 3 phase.

[shadow99]

Yeah, I've used rotary converters before. But have you seen the needle on an electric meter spin with one of those running :eek: (I have), and I was glad it wasn't my electric bill. They have "other" ways of creating the third-leg as well, but they are not as efficient, depending on the HP requirement.

Rick

[stevenovascotia]

Rick:
I'm not talking about a rotophase or add a phase. I am refering to a solid state ac drive used for speed control on 3 phase motors. Basically it converts the AC to DC with a rectifier, then reconverts back to controllable AC of whatever frequency you want - typically 0-400HZ. The rectifier doesn't care if you feed them single or three phase, just have to oversize slightly to account for the higher single phase Amps on the input. I apply them often as a way to run 3 phase machinery on single phase services. As a matter of efficiency, a single phase motor typically has an efficiency of around 50-60%, whereas the AC drive is typically 98%, and the three phase motor you're driving around 85-90%. The savings on power will pay for the AC drive in a short time if you use the machinery much. Added bonus - you can control the speed. You can also use one drive to power a variety of machines - just size it for the biggest machine and put a plug on the output of the drive to plug in the appropriate machine. I know what you mean about the rotary phase converters :( - their efficiency is around 35-40% if I recall. I don't know what the efficiency of the add a phase units is, but I woild guess no more than 50% for sure.

[Dave Fleming]

You fellows referring to a VFD?
Poke your nose into the USENET group: rec.crafts.metalworking and there is a FAQ which includes recipes for making your own phase converters. I have NO idea how efficient they are but the poster who designed it is a Boeing Fellow working on the Space Station, Fitch Williams by name. Probably Google would get you that info too.

[Ed Harrow]

An interesting twist, LOL. Thanks for the suggestions. smile.gif Ed

[Dave Fleming]

Sorry Ed, seems like I instigated a thread hijack.