Find the safe-to-use plasticizers
Not all phthalates are the same
Plasticizers are used to increase the workability and flexibility of PVC. There are different plasticizers with different chemical structures and different level of performance. Plasticizer properties vary according to their chemical structure and molecular weight, phthalates, epoxies, aliphtatics, trimellitates, polymeri cs etc.
Plasticizers can be subdivided into primary general purpose plasticizers that are suited to a very wide range of applications and processes because they offer optimal balance between cost, versatility, performance and secondary plasticizers that enhance processing (fast fusing, VM, …) or enhance specific flexible PVC properties (like Cold T° flexibility, flame retardancy, …). They are more often less compatible with PVC and usually impair all around properties of Primary General Purpose plasticizers. Other performance differences exist within the same plasticizer family. For example, phthalates include Low and high molecular weights ortho-phthalates and tere-phthalates.
What is the difference between low and high molecular weight ortho-phthalates?
The chain length of the alcohol chain involved in the creation of the plasticizer impacts the overall molecular weight of the final ortho-phthalate plasticizer. The higher the molecular weight, the better the retain properties after aging of the flexible PVC material. A high molecular weight ortho- phthalate contains from 7 and higher carbons in the alcohol backbone, below it is considered as a low molecular weight.
This difference is important as it influences not only the physical properties (volatility, solubility, …) but also the toxicology of the phthalates: low phthalates are strictly regulated under REACH and restrictions apply. With a low molecular weight phthalate, there is a risk of losing plasticizers under aging conditions due to a higher volatility or lower resistance to extraction. This high volatility and plasticizer weight loss is observed when the flexible PVC exposed to heat.
In contrary, a high molecular weight phthalate plasticizer is safe to use as it has low volatility properties.
Low versus High ortho-phthalates
Not only the HMW ortho-phthalates plasticizers are safe to use and safe in use, they provide increased permanency and durability as they exhibit lower volatility and resist heat aging conditions.
Exposure to plasticizers is essentially linked to plasticizer retention over time and this property is depending on the plasticizer compatibility with PVC and its resistance to migration and extraction. The latter are dependent on plasticizer’s chemical structure. Incompatible plasticizers will always exude from articles and come out, as soon as a mechanical stress is exerted on finished article. That’s why safety and performance are completely related when it comes to select the right plasticizers for your application. The key is to choose a performant plasticizer that is highly compatible with PVC and with low volatility to make sure it never leaches out of the finished article.
Phthalates plasticizers are among one of the most tested substance in the world with 50 years of research and 200 health and environmental studies confirming their safety. It also shows that alternatives have not yet been evaluated as extensively as DINP for example:
Several in-depth regulatory evaluations have also been performed by governments across the world over the last 10 years proving their safety:
The latest risk assessment committee conducted by ECHA in March 2018 concluded that Di-isononyl phthalate (DINP) does not warrant classification for reprotoxic effects under the EU’s Classification, Labelling and Packaging (CLP) regulation. It confirms the lack of evidence of adverse effects and that no classifications is required.