In flexible PVC formulations, a single plasticizer does not always meet every expectation. A product must flex and process well at room temperature and still be usable in the cold without stiffening. In phthalate-free formulations, a common way to strike this balance is to use DOTP and DOA together. This article outlines the logic of this blend.
Primary and secondary plasticizers
In formulations, plasticizers are often thought of as primary and secondary. The primary plasticizer gives PVC most of its flexibility and forms the backbone of the formulation. A secondary plasticizer is added at a lower level to strengthen a specific property. With its general-purpose character, DOTP is often used as the primary plasticizer, while DOA is added as a secondary plasticizer to support cold flexibility.
What DOTP contributes
DOTP is a phthalate-free, general-purpose plasticizer. It makes PVC flexible and forms the basis of the formulation in many applications. For its identity and uses, see our DOTP plasticizer page and our article What Is DOTP Plasticizer?
What DOA contributes
DOA is an adipate plasticizer known for helping PVC stay flexible at low temperatures. This matters for products used in cold climates, outdoor applications or cold storage. Added to a formulation, DOA helps reduce the product’s tendency to stiffen in the cold.
How is the ratio set?
The DOTP-to-DOA ratio is set according to the product, its conditions of use and the target properties. As a general rule, the DOA level can be raised as the need for cold flexibility grows, but raising it can also affect other properties, so the ratio should be confirmed through trial runs and tests. Parameters such as volatility, migration and processing behaviour are also taken into account.
Which products use the blend?
- Cables and cable sheathing: cables that must bend in cold environments.
- Seals and profiles: parts that must stay flexible in the cold.
- Artificial leather: coatings that should stay soft in cold weather too.
- Plastisol products: plastisol items expected to stay flexible in the cold.
DOA and DOTP in plastisol
In plastisol formulations, the choice of plasticizer also affects the paste’s viscosity and gelation behaviour. Plastisols can be based on DOTP, on DOA or on a blend of the two. The blend ratio is set to balance both the flexibility of the final product and the processability of the paste. For details, see our PVC plastisol page.
Steps in a formulation trial
- Define the product’s conditions of use and target properties.
- Create a DOTP-based starting formulation.
- Try different ratios by adding DOA according to the cold flexibility need.
- Test flexibility, processability and other critical parameters.
- Set the final ratio based on the results.
Planning supply together
For producers using DOTP and DOA together, planning the supply of both is practical. You can state the quantities, packaging preferences and quality criteria for both products in the same quote request. Packaging and quantity are clarified in the quote.
Building a trial plan
A systematic trial plan helps set the blend ratio. For example, several trial recipes with different DOA and DOTP ratios are prepared, and cold behaviour, hardness, surface appearance and ease of processing are observed for each. Comparing the results in a table helps select the balance that suits your product requirements. It is recommended that this process be led by your technical team using your own test methods.
Once the chosen ratio goes into production, consistency can be monitored with periodic checks.
Frequently asked questions
Can DOA be used on its own?
It can, but in most formulations it is preferred as a secondary plasticizer together with a general-purpose plasticizer such as DOTP.
What ratio is recommended?
The ratio depends on the product and conditions of use; it should be determined by trials and tests.
Conclusion
Using DOTP and DOA together is a practical way to balance general properties and cold flexibility in phthalate-free PVC formulations. See our DOA plasticizer page for details, and send your needs via the quote form.