Karwon Composites supplies carbon, glass and aramid prepreg into the UAE, matched to the cure schedule you can run.
Prepreg is the most demanding material a composites buyer in this region will ever order, and it is the one most often ordered badly. It arrives frozen, it has a clock running on it from the day it leaves the mill, and a specification that omits one line can produce a roll that is technically correct and commercially useless.
This is a guide to specifying it properly, written for engineers and procurement staff buying into the UAE.
What prepreg actually is
Prepreg is reinforcement that has already been impregnated with a resin system at the mill, at a controlled resin content, and then partially advanced so it is tacky rather than wet. You lay it up, apply heat and pressure, and the resin completes its cure.
The appeal is control. Wet layup resin content varies with the person holding the roller. Prepreg does not. Fibre volume fraction is set at the mill, which is why aerospace and motorsport structures are built from it and why anyone chasing repeatable mechanical performance eventually moves to it.
The cost is logistics. That advanced resin keeps advancing, slowly, whenever the material is above freezing.
The six lines your specification needs
Most enquiries we receive give two of these. Give all six and a supplier can quote in one pass instead of three.
1. Reinforcement type and format. Carbon, glass or aramid. Unidirectional or woven, and if woven, the weave. A 2x2 twill and a plain weave at the same areal weight behave differently over a tight radius.
2. Fibre areal weight, in gsm. Not thickness. Areal weight is the number the mill produces to and the number that determines how many plies you need. Cured ply thickness follows from areal weight and resin content, and quoting thickness alone forces the supplier to guess at both.
3. Resin content, as a percentage. Typically in the low to mid thirties for structural prepreg. Higher resin content improves tack and drape and adds weight. Lower content is lighter and stiffer to handle. If you do not state it, you will get the mill's house standard, which may not match what you tested with.
4. The cure schedule you can actually run. This is where most specifications fail. There is no point ordering a system that cures at 120 degrees if your oven tops out at 90. State the temperature and dwell you have available, and let the supplier match a resin to it rather than the other way round.
5. Glass transition temperature required. Your service temperature drives this, not the other way round. See the section below, because this is the single most misunderstood number on any prepreg datasheet.
6. Roll width and length. Width determines waste. If your part is 900 mm across and the roll is 1000 mm, you are paying for material you will trim off on every ply.
The Tg question, and why the numbers look wrong
A datasheet will commonly show a resin curing at 80 degrees and reporting a glass transition temperature of 91 degrees. Buyers see this and assume a misprint or an error.
It is neither. Low temperature curing systems are specifically formulated to produce a Tg above their cure temperature. The 91 is the result of the 80 degree cure, not a separate target you have to reach.
There is a further complication worth knowing before you compare two datasheets. Tg is measured three different ways and the numbers are not interchangeable. DSC gives one figure. DMA storage modulus onset gives another, usually the most conservative. DMA tan delta peak gives the highest, sometimes twenty degrees above the onset value.
If you are comparing suppliers, make sure you are comparing the same method. A mill quoting tan delta peak against a mill quoting DMA onset will look like the better material and may not be. Ask which method the figure came from. A supplier who cannot answer that is reading you a number off a sheet rather than understanding the material.
For design purposes, the onset value is the one to work to, and your service temperature should sit comfortably below it.
Shelf life, out-life and the cold chain
Prepreg carries two clocks and they are not the same thing.
Shelf life is how long the material lasts stored at minus 18 degrees. Usually measured in months to a year.
Out-life is how long it can spend at room temperature, cumulatively, before the resin has advanced too far to process. Usually measured in days to a few weeks. Crucially, out-life accumulates. A roll taken out for two hours on four separate occasions has used eight hours of its out-life, and nobody is going to remember unless you keep a log.
Three practical consequences for buying into the UAE:
Ask what the material has already used. By the time a roll reaches you, it has been through a mill freezer, a freight forwarder, a port and a customs process. Ask the supplier how out-life is tracked in transit and what proportion is typically consumed before delivery. If they have never thought about it, that tells you something.
Confirm you can store it before you order it. A domestic freezer is not a prepreg freezer. If you do not have minus 18 storage, your usable window is out-life alone, and you should be ordering in quantities you can consume rather than stocking.
Understand the freight implication. Frozen transport is more expensive and more constrained than ambient. It shapes your lead time and your minimum sensible order quantity more than the material price does.
Carbon, glass and aramid, and where each earns its place
Carbon prepreg is the default for stiffness-critical structures. UAV airframes, tubes, motorsport components, anything where deflection under load is the binding constraint.
Glass prepreg costs less, weighs more, and is electrically insulating rather than conductive. That last property is the reason it is chosen far more often than people assume. Radomes, antenna housings, electrical enclosures and anything that must not interfere with a signal are glass, not carbon, regardless of budget.
Aramid prepreg is chosen for impact and abrasion resistance rather than stiffness. It absorbs energy where carbon fractures. It is also difficult to machine and cut cleanly, and it absorbs moisture, both of which need planning for at the design stage rather than discovering in production.
Hybrid constructions exist and are common in protective applications, typically aramid on the impact face with glass or carbon behind it.
What to ask any prepreg supplier before you commit
- Which resin system, and can I have the datasheet with the Tg measurement method stated?
- What is the shelf life at minus 18, and what out-life at ambient?
- How much out-life is typically consumed in transit to this region?
- What roll widths are available, and can you slit to a width I specify?
- Is the material shipped frozen, and what packaging and monitoring comes with it?
- What documentation accompanies each consignment?
- If I need a different cure schedule later, can the same reinforcement be supplied on a different resin?
The last question is worth more than it looks. It tells you whether you are talking to a mill with a resin range or a trader moving one product.
Sourcing prepreg into the UAE
There is no prepreg production in the Emirates. Every roll used here is imported, which makes the supply chain, not the material, the thing that determines whether your programme runs on time.
Karwon Composites supplies carbon, glass and aramid prepreg into the UAE, with the resin system, cure schedule and format matched to what you can actually run rather than what happens to be on a shelf. Documentation requirements are agreed at quotation stage.
Tell us the part, the oven you have and the service temperature, and we will work the specification through with you.