A comparative assessment of the use of suitable analytical techniques to evaluate plasticizer compatibility

The evaluation of novel phthalate-free plasticisers for PVC formulations is hindered by the lack of a reliable quantitative method for testing plasticizer exudation from PVC formulations. Two methods of improving upon the ASTM D3291 exudation test have been trialed using ATR-FTIR and GC-MS. The results of these methods are compared alongside a study of the glass transition temperatures (T-g) by dynamic mechanical analysis (DMA). FTIR is found to be unsuitable for determining plasticizer exudation as the method is not sufficiently sensitive to detect small changes in plasticizer distribution. Carbonyl peak positions in unstressed samples are instead investigated to determine the strength of interaction between the plasticisers and PVC chain. GC-MS is successfully used to quantify plasticizer exudation that could not be observed visually or by FTIR. Furthermore, these methods show limited correlation to each other, which highlights the importance of testing multiple aspects of compatibility when developing novel plasticisers for use in PVC.

Automated summary

The lack of a reliable quantitative method for testing plasticizer exudation from PVC formulations hinders the evaluation of novel phthalate-free plasticizers. Two methods, ATR-FTIR and GC-MS, were trialed to improve the ASTM D3291 exudation test. FTIR was found unsuitable due to its insensitivity to small changes in plasticizer distribution, while GC-MS successfully quantified plasticizer exudation that could not be observed visually or by FTIR. Testing multiple aspects of compatibility is important when developing novel plasticizers for use in PVC.