Nanoclays are nanoparticles of layered mineral silicates. Organically-modified nanoclays (organoclays) are an attractive class of hybrid organic-inorganic nanomaterials with potential uses in polymer nanocomposites. A plethora of literature regarding the apparent compatibilizing effect of organo-nanoclays in immiscible thermoplastic blends currently exist. A recent report has shown that adding organo-modified nanoclays could promote blend droplet morphology refinement and stabilization, as well as enhancement of interfacial adhesion; similar result to what is observed when adding a macromolecular compatibilizer. However, the extent to which clay nanoparticles can be considered as full compatibilizers is somewhat unclear up to now.
To this effect, Professor Thierry Aubry at University of Western Brittany, France, presented a critical review and expert opinion on clay-mediated compatibilization of immiscible polyethylene/polyamide blends with droplet morphology. In his overview, he particularly focused on a specific polymer couple, namely polyethylene (LDPE or HDPE) and polyamide (PA6 or PA12), and on a specific morphology, that is the droplet-like morphology. His work, partly based on studies performed by his own research group over the past decade, is currently published in the research journal, Applied Clay Science.
In his approach, Professor Aubry considered all aspects of clay-mediated compatibilization of polyethylene/polyamide blends with droplet morphology. Additionally, he also considered the end-use mechanical properties for the investigation of interfacial adhesion. He discussed experimental results from structural investigation techniques at different length scales, as well as rheometric and mechanical tests. The mechanisms responsible for compatibilization were also addressed for both PA matrix and PE matrix blend-based nanocomposites. Lastly, the clay-mediated compatibilizing effect, in terms of droplet morphology refinement and stabilization, as well as improvement of interfacial adhesion, was compared to graft copolymer-mediated macromolecular compatibilization.
Generally, the author reported that the mechanisms responsible for the compatibilizing effect of organo-modified nanoclays mainly depend on the matrix nature and on the preferential affinity of nanoclays towards one of the two polymer phases. Interestingly enough, commercial nanoclays with marked selective affinity towards PA dispersed phase in PE matrix blends with droplet morphology seem to fulfill all the expected functions of a true compatibilizer.
In summary, Professor Aubry paper presents an excellent overview of the literature dealing with the compatibilizing effect of commercial organo-modified nanoclays in polyethylene/polyamide blends with droplet morphology. Exquisite comparisons were made and presented for studies dealing with PA- against those dealing with PE- matrix blend-based nanocoposites. Overall, Professor Aubry concluded that polar organo-nanoclays were very good candidates for compatibilizing PE matrix blend-based nanocomposites and could even challenge macromolecular compatibilizers; at least provided that clay migration to the interface could be achieved during processing, which is still poorly controlled.
Thierry Aubry. An overview on clay-mediated compatibilization of polyethylenepolyamide blends with droplet morphology. Applied Clay Science, volume 175 (2019) page 184–189.