Greetings experimenters and material experts,
I am looking for a single sided adhesive tape to seam together two sections of 6 micron Dupont type C mylar for the diaphragm in my speaker design. The seam lands on a spacer so it won’t be outputting sound but it is important for my build that the two sections of diaphragm are tensioned at that same time and this requires a seam. I have successfully done it with a variety of tapes, but when it comes to stretching the diaphragm the uneven tension at the seam is more than I would like. I’m looking for a tape that has similar stretch characteristics to mylar with a strong adhesive shear strength. I was hoping someone had experimented with this… perhaps in an attempt to repair ripped mylar or in a radially segmented build. Or is there another way to seam mylar and not drastically impact the stretch?
Any Ideas?
I am looking for a single sided adhesive tape to seam together two sections of 6 micron Dupont type C mylar for the diaphragm in my speaker design. The seam lands on a spacer so it won’t be outputting sound but it is important for my build that the two sections of diaphragm are tensioned at that same time and this requires a seam. I have successfully done it with a variety of tapes, but when it comes to stretching the diaphragm the uneven tension at the seam is more than I would like. I’m looking for a tape that has similar stretch characteristics to mylar with a strong adhesive shear strength. I was hoping someone had experimented with this… perhaps in an attempt to repair ripped mylar or in a radially segmented build. Or is there another way to seam mylar and not drastically impact the stretch?
Any Ideas?
HankF, Thank you so much!
I will try not to overtax your generosity with a million bonding questions... but do you think you could enquire about a suitable replacement for 3M Scotchgrip 4693 or 4693H, it is unfortunately un-sellable in California. The usage is for attaching 1/16" thick styrene strips to polly coated perf metal.
I will try not to overtax your generosity with a million bonding questions... but do you think you could enquire about a suitable replacement for 3M Scotchgrip 4693 or 4693H, it is unfortunately un-sellable in California. The usage is for attaching 1/16" thick styrene strips to polly coated perf metal.
brotron, sounds like hank will give u some good info. A while bake I was getting samples from 3M for a purpose very similar to what you are discribing. The biggest issue whith adhesive backings on these tapes for your application is "creep". The adhesives will sheer over time when u put tension on them thus u will loose that tension.
I cannot remember which 3M tape worked best but it wasnt an acrylic or an silicone adhesve. The one that held the tension over time best was a rubber based adhesive backing. anyway just look up 3M info on creep resistant tape backing. The rubber was not sun light resistant like the acrylic though so needs protection if expected to last.
In the end howver there is still some question as even the best creep resistant pressure sensative adhesives will creep some and a diaphragm tension chages a lot with just a little movment.
I know I have the info in my notes somewhere. If I find I will report back.
I cannot remember which 3M tape worked best but it wasnt an acrylic or an silicone adhesve. The one that held the tension over time best was a rubber based adhesive backing. anyway just look up 3M info on creep resistant tape backing. The rubber was not sun light resistant like the acrylic though so needs protection if expected to last.
In the end howver there is still some question as even the best creep resistant pressure sensative adhesives will creep some and a diaphragm tension chages a lot with just a little movment.
I know I have the info in my notes somewhere. If I find I will report back.
The creep over time wont be an issue for that seam as long as it can handle a couple of days, since ultimately both sides of the splice will be glued to a spacer... but it could be an issue for using tape with the membrane in general. I had planned to use contact cement instead of tape to attach the membrane to the styrene spacers. I wasn't so impressed with the initial holding power of thin double sided tape in my application, more for the styrene side than the membrane side. That being said there may be more creep with contact cement rubber but I hope not.
Meanwhile, here's a bit of reading for the weekend:
http://multimedia.3m.com/mws/media/372489O/adhesives-and-tapes-design-guide.pdf
http://multimedia.3m.com/mws/media/372489O/adhesives-and-tapes-design-guide.pdf
http://multimedia.3m.com/mws/media/142942O/dc-polyester-tapes-with-adhesive-830-442kw-442w-442dl.pdf
These are the tapes that I found to be the most sheer / creep resistant.
These are the tapes that I found to be the most sheer / creep resistant.
thats funny, I ran the serial from the tape I had order from McMaster and it turned out to be the 442kw with the 830 glue. It was what I initially planned to use for the spacer to diaphragm bond. I didn't love the way it was sticking to the styrene, if I switched to an acrylic spacer I might have better luck with all my bonds. Great reading guys! I was just laughing at a dinner party last night about what I read in bed at night.
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Input from app engineer:
"3M does not use the DuPont tradename Mylar, but we do make adhesive tapes out of the same polymer. My recall is that the thinnest film used in tape is about 0.0005” and sort of comparable to DuPont 48C. A tape with a thermosetting adhesive made with film of this thickness is 3M 74 Tape. (Data Page attached.) Based on thickness it is going to have 8 times the tensile modulus of the 6C in the speaker diaphragm, but it is going to be difficult to find something thinner as an adhesive tape. Alternatively, the user could cut strips of the 6C they already use and bond the strips to the spacer and to the two edges of the speaker diaphragm with a cyanoacrylate, like EC5. (Data Page attached.)
I understand the issue with SCAQMD Rule 1168 and 3M Adhesive 4693. I am attaching our document that addresses LEED, but also SCAQMD. I am not sure of the specific status of this manufacturer, but a lot of customers use 94. Here are a couple links and I am attaching a Data Page."
*3M? Hi-Strength 94 ET Adhesive
*3M? Hi-Strength Postforming 94 CA Adhesive Red Low VOC, 5 gal pail, 1 per case Bulk - NOT FOR CONSUMER/RETAIL SALE OR USE
He attached 4 .pdf files to his email. If you'll PM me your email address, I'll forward to you. I hope this helps.
"3M does not use the DuPont tradename Mylar, but we do make adhesive tapes out of the same polymer. My recall is that the thinnest film used in tape is about 0.0005” and sort of comparable to DuPont 48C. A tape with a thermosetting adhesive made with film of this thickness is 3M 74 Tape. (Data Page attached.) Based on thickness it is going to have 8 times the tensile modulus of the 6C in the speaker diaphragm, but it is going to be difficult to find something thinner as an adhesive tape. Alternatively, the user could cut strips of the 6C they already use and bond the strips to the spacer and to the two edges of the speaker diaphragm with a cyanoacrylate, like EC5. (Data Page attached.)
I understand the issue with SCAQMD Rule 1168 and 3M Adhesive 4693. I am attaching our document that addresses LEED, but also SCAQMD. I am not sure of the specific status of this manufacturer, but a lot of customers use 94. Here are a couple links and I am attaching a Data Page."
*3M? Hi-Strength 94 ET Adhesive
*3M? Hi-Strength Postforming 94 CA Adhesive Red Low VOC, 5 gal pail, 1 per case Bulk - NOT FOR CONSUMER/RETAIL SALE OR USE
He attached 4 .pdf files to his email. If you'll PM me your email address, I'll forward to you. I hope this helps.
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