A speaker adhesive technical data sheet can run to two full pages and tell you nothing usable. It will list viscosity without a shear rate, adhesion as "excellent to most substrates", and cure as "fully cures in 24 hours" with no temperature attached. None of those numbers can be compared to another supplier's numbers, and none of them predicts what happens when the material meets your dispensing head, your cone material and your oven.
Six fields do predict that. They are the same six whether you are buying lead-wire adhesive, a damper grade, a water-based surround adhesive or a two-part epoxy, and they share one property: each is meaningless without its measurement condition. A viscosity is a number plus a spindle, a speed and a temperature. A pot life is a number plus a mass and a temperature. Strip the conditions off and you are left with decoration.
This matters concretely for anyone evaluating Aosibo Adhesives, a Dongguan supplier whose range maps bond by bond onto a loudspeaker driver. No technical data sheet was provided for any of its grades at review, and the company has no website to check one against. Its own stated position is that viscosity, cure schedule, pot life and substrate data are shared at inquiry, and that mix ratio, pot life, fixture time, full-cure schedule and substrate compatibility are all order-specific. That is a defensible way to run a specialty adhesive business. It also means the TDS is something you request rather than something you download — so the useful skill is knowing exactly what to demand in it, and how to tell a real one from a hollow one when it lands.
Three fields that describe the material in the container
Field 1 — Viscosity, with the condition attached
Viscosity determines whether the material can be dispensed by the equipment you already own, whether the bead holds its shape on a vertical surface, and whether it wicks where you do not want it. It is the single most quoted and most under-specified value on any adhesive datasheet.
A usable entry looks like: 4,500 mPa·s, Brookfield RVT, spindle 4, 20 rpm, 25 °C. An unusable entry looks like: 4,500 cps.
The reason is that most adhesives are non-Newtonian. Viscosity falls as shear rate rises — that is the property that lets a thixotropic paste sit still on a top plate and still pump through a needle. Two products both labelled "4,500 cps" can behave completely differently at the shear rate inside your dispense tip. Ask for the measurement condition, and if you dispense at high shear, ask whether a thixotropic index or a two-point viscosity (low speed and high speed) is available.
Insider detail: for water-based surround adhesives in particular, ask what the viscosity is after the material has been stirred and left standing for an hour. Waterborne dispersions can be shear-sensitive and can shift over a shift on an open pot. That number is rarely on the sheet and is usually available if you ask.
Field 2 — Solids content, for anything waterborne or solvent-borne
Solids content — non-volatile content — tells you how much material stays behind after the carrier evaporates. It sets the dry film thickness you actually get from a given wet bead, and it sets the drying load your line has to remove.
Two suppliers quoting the same price per kilogram at 35 % and 50 % solids are not quoting the same price. The higher-solids product delivers roughly forty per cent more dry adhesive per kilogram and asks your dryer to remove correspondingly less water. On a surround line where drying is the bottleneck, solids content is a throughput number, not a chemistry number.
Ask for the test method alongside it — typically a gravimetric determination with a stated sample mass, oven temperature and dwell — because "solids" measured at 105 °C for one hour and at 150 °C for thirty minutes are not the same figure. For a reactive two-part system, solids content is usually irrelevant and its presence on the sheet as "100 %" is fine and expected.
Field 3 — Open time and pot life, with mass and temperature
Open time is how long the applied bead stays receptive to the second substrate. Pot life applies to mixed two-part systems and is how long the mixed material stays dispensable. Both are strongly temperature-dependent and, for pot life, strongly mass-dependent — the reason two-part systems behave so differently in a 100 g cup and a 2 g bead is set out in more detail in the piece on two-part epoxy AB systems on a driver line.
What a usable sheet states: the value, the temperature, the relative humidity if the system is moisture-sensitive, and for pot life the mixed mass. What a hollow sheet states: "long open time".
If your plant runs without climate control — and many driver lines in South China do not — ask for the value at 30 °C or 35 °C as well as at the lab standard. A supplier who has that data has run the test. A supplier who has not will say so, which is itself useful information.
Three fields that describe the bond it becomes
Field 4 — Cure schedule, as fixture time and full cure, each at a named temperature
One number called "cure time" is not a cure schedule. A cure schedule has at least two points:
- Fixture time — when the joint holds well enough to move to the next station. This must come with the strength threshold that defines it and the substrate pair it was measured on, or it cannot be compared between suppliers.
- Full cure — when the published mechanical properties are reached. This must come with a temperature and dwell, ideally as both an ambient schedule and an accelerated oven schedule.
If a grade can be oven-accelerated, the sheet should give the alternative schedule explicitly — for example an ambient route and a route at a stated oven temperature and dwell. That pair is what lets you decide whether an adhesive fits the cure capacity you actually have, rather than the capacity you would need to buy.
Field 5 — Bond performance on named substrates, with test method and failure mode
"Excellent adhesion to a wide range of substrates" is the phrase that tells you the sheet has nothing behind it. A usable entry names both substrates, gives a strength value, cites the test method, and states the failure mode.
Test methods worth seeing referenced: ASTM D1002 or ISO 4587 for single-lap shear on rigid adherends; ASTM D903 for 180° peel; ASTM D897 for tensile butt joints. For a driver, the relevant pairs are specific and unglamorous — tinsel lead to paper cone, phenolic-impregnated spider to steel frame, rubber or foam surround to a treated paper cone, steel top plate to ferrite. Generic figures on aluminium-to-aluminium lap shear tell you almost nothing about any of those.
Failure mode is the field almost nobody asks for and the one that carries the most information. A cohesive failure — the adhesive itself tears, leaving material on both faces — means the interface is stronger than the bulk and the number you are reading is a real property of the adhesive. An adhesive failure, where the bond peels cleanly off one substrate, means you measured the interface, and the value will move the moment your substrate supplier changes a surface treatment. Ask which one the quoted figure was.
Field 6 — Service conditions and shelf life
Two things belong here and both are contractual, not merely technical.
Service temperature and, for reactive systems, glass transition temperature. A driver bond runs hot under continuous power. An adhesive that softens near its glass transition temperature will creep under sustained load long before anything visibly fails. A continuous service temperature range is the minimum; a Tg value with the method used to obtain it is better.
Shelf life from date of manufacture, plus storage temperature. Not from date of shipment. On cyanoacrylates and two-part systems, remaining shelf life when the container is opened at your end matters more than transit time. Agree a minimum remaining shelf life on arrival as a contract term — a common formulation is a stated percentage of nominal shelf life remaining at the port of discharge — and require the date of manufacture printed on every container.
The comparison table: real TDS versus hollow TDS
| Field | What a usable sheet says | What a hollow sheet says | Why it decides something |
|---|---|---|---|
| Viscosity | Value + instrument + spindle + rpm + temperature | "Medium viscosity" or a bare cps number | Whether your dispenser can run it and whether the bead holds shape |
| Solids / non-volatile | % + gravimetric method, sample mass, oven temp and dwell | Omitted, or "high solids" | Dry film per wet gram; drying load on the line |
| Open time / pot life | Value + temperature + RH + mixed mass | "Long working time" | Operator dwell, batch size, scrap per shift |
| Cure schedule | Fixture time with strength threshold; full cure at named temperature and dwell; ambient and oven routes | "Cures in 24 hours" | Whether it fits your oven and your takt |
| Bond performance | Named substrate pair + value + ASTM/ISO method + failure mode | "Excellent adhesion to most materials" | Whether the number transfers to your actual parts |
| Service and shelf life | Continuous service range, Tg with method, shelf life from date of manufacture, storage temp | "Store in a cool dry place" | Field returns; how much of what you buy is still usable |
Four more tells that a sheet is decoration rather than data: no revision number and no revision date anywhere on it; no units on at least one value; identical numbers repeated across three or four different grades in the same family; and no distinction drawn between typical values and specification limits. That last one matters — a typical value is what the plant usually makes, a specification limit is what they will accept a complaint about. Ask which the sheet is quoting, and ask for the specification limits separately if the grade is going into a production bond.
One more thing the TDS is not: it is not the safety data sheet. Those are separate documents with separate purposes, and a supplier who sends the SDS when you asked for the TDS has answered a different question. Request both by name, per grade, and treat them as two line items on the document list you would build using what documents to request from a Chinese supplier before your first order.
Make the TDS request the first ask, not the fifth
Because no datasheet exists for these grades in public, the request itself becomes your first real test of the supplier. How a supplier answers a precise data request tells you more than any brochure: whether they have run the tests, whether they understand the application, and whether they will still be answering technical questions in month nine.
Send this, per grade, at first inquiry:
- Grade designation and pack format — including whether the MOQ unit is a bottle, cartridge, syringe or kilogram, since that changes the price basis entirely.
- Viscosity with instrument, spindle, speed and temperature; plus a second point at your plant temperature if you run without climate control.
- Solids content with the gravimetric method, for any waterborne or solvent-borne grade.
- Open time and pot life with temperature, humidity and mixed mass.
- Cure schedule — fixture time with its strength threshold and substrate pair, plus full cure at both an ambient and an oven route.
- Lap shear or peel figures on your two named substrates, with the ASTM or ISO method and the failure mode observed.
- Continuous service temperature and Tg, with method.
- Shelf life from date of manufacture and storage temperature, plus agreement on minimum remaining shelf life at arrival.
- Revision number and date on the sheet, and confirmation whether values are typical or specification limits.
- For any grade sold as halogen-free, the test report and the numeric threshold it was measured against — halogen-free is a measured claim, not an adjective.
Send both of your actual substrates and the cure window you have available at the same time. That combination — the substrate pair plus the constraint — is what lets a technically competent supplier narrow a range to one or two grades instead of sending the whole catalogue. Aosibo's factory profile on ChinaMakersHub sets out the loudspeaker range these requests apply to, from the lead-wire adhesive on the tinsel bond through the surround and magnet-circuit grades. Build the request into the same document set you would send with any specification — the structure in how to write a product spec sheet for a Chinese factory works unchanged for chemicals, with the six fields above dropped in as the acceptance criteria.
Common questions
What if the supplier says the data is order-specific and will be provided after the order?
That is a reasonable position for a formulation that is genuinely tailored, and an unreasonable one as a reason to withhold everything. Split the request: ask for the six fields on the closest existing grade now, marked as indicative, and for the finalised sheet on the tailored grade before you release the production order. If the supplier can provide the first, they have a lab. If they cannot provide either, you are buying blind and should price that risk into the first order size.
Should I accept a datasheet that has no revision date?
Treat it as provisional. A revision number and date are how you know which version of a formulation the numbers describe — without them you cannot tell whether a bond failure eighteen months from now involves the same material you qualified. Ask for the sheet to be reissued with a revision identifier and date, and keep the copy you qualified against with your retained sample.
Which of the six fields should I test myself rather than take on paper?
Bond performance on your own substrates, every time. Viscosity, solids and shelf life are properties of the material and travel reasonably well from a supplier's lab. Adhesion is a property of the interface — your cone treatment, your frame coating, your surface cleanliness — and it will not reproduce a supplier's figure reliably. Run lap shear or peel on your actual parts during the sample cycle, and run a humidity-aged set alongside the fresh one.