You’ve got the perfect bottle design—but have you checked the AA level? If your PET preform smells odd or affects sensitive formulations, the problem could be acetaldehyde.
AA (Acetaldehyde) is a byproduct formed during PET preform production. High AA levels can cause off-odors or react with sensitive cosmetic ingredients. For cosmetics, AA should generally be kept below 8 ppm. Testing and resin quality are key to controlling it.
Let’s explore what AA is and why it matters more than most people think.
Outline
What Is AA (Acetaldehyde) in PET Preforms?
Acetaldehyde (AA) is a volatile organic compound produced when PET is heated during injection molding. It’s naturally occurring but becomes problematic when it:
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- Builds up in the preform
- Migrates into the product
- Causes smell, taste, or chemical instability
While it’s mostly a concern in bottled water, certain cosmetic products—like natural serums, alcohol-based sprays, or essential oils—are also sensitive.
How Is AA Formed During PET Production?
AA is mainly created in the melting and injection stage of the preform process. Factors influencing its generation include:
- Resin drying – Incomplete drying increases degradation
- Barrel temperature – Overheating PET resin forms more AA
- Injection speed – Excessive pressure or hold time raises AA
- Poor mold cooling – Slows down solidification, increasing byproducts
Using the right parameters on your PET preform injection molding machine can significantly reduce AA.
Why Should Cosmetic Brands Care About AA Levels?
Here’s what can go wrong with high AA in cosmetics:
- Unpleasant odor inside an otherwise scent-free formula
- Interaction with actives like vitamin C or plant extracts
- Consumer perception issues—smells like plastic or “chemical”
- Shelf-life reduction if AA accelerates oxidation
If your cosmetic packaging is designed for clear liquids, aromatherapy, or pH-sensitive products, you must request low-AA preforms.
What Is a Safe AA Level for Cosmetic Packaging?
There’s no universal legal standard for cosmetics, but here’s what the industry follows:
| Application | Recommended AA Level |
| Bottled water | < 3 ppm |
| Carbonated beverages | < 6 ppm |
| Cosmetic packaging (general) | < 8 ppm |
| Sensitive/natural formulas | Preferably < 5 ppm |
You can request an AA content certificate from your supplier before placing a large order.
How to Test and Control AA in PET Preforms?
AA is typically measured using gas chromatography. Some large-scale suppliers do in-house testing, while others use third-party labs.
Tips for control:
- Use resin designed for low-AA output (ask for data sheet)
- Keep injection molding temperature stable
- Dry resin thoroughly (4–6 hours at 160°C)
- Optimize mold cooling channels
Advanced systems like Husky or KGI Preforms’ automatic injection lines often include AA reduction modules.
What to Ask Your Supplier About AA Management?
Before finalizing your preform supplier, ask the following:
- What’s the average AA level in your preforms?
- Do you offer low-AA grade PET resin options?
- Can you provide test reports or data sheets?
- Do you run regular QA checks for AA content?
- Can you produce <5 ppm AA for sensitive formulas?
Also, ask if they’ve worked with cosmetic or pharmaceutical clients, as these industries require tighter AA control.
Conclusion
AA level may be invisible, but its impact is real. A plastic scent in your face mist could be enough to lose a customer. Work closely with your supplier, define your limits, and always test. Want help sourcing low-AA PET preforms? Let me guide you—drop a message anytime.
