Progress in Bionanocomposite Technology: a Novel Bio-Organo-Modified Layered Double Hydroxide for Poly(butylene succinate) Reinforcement

The substitution of the fossil-derived polymers with materials from renewable resources is a great challenge, and many efforts are carried out to improve their technical performances, usually quite poor respect to the petro-based polymers. Among biopolyesters, poly(butylene succinate) (PBS) is interesting because it shows balanced performances in terms of thermal and mechanical properties as well as good processability and biodegradability. However, insufficient stiffness, low melt strength and viscosity, as well as low gas barrier properties are some of the lacks of PBS. The nanocomposite technology allows overcoming such deficiencies and represents an opportunity to obtain high-performing materials. For this purpose, bionanocomposites based on PBS and a novel organo-modified layered double hydroxide (LDH) have been prepared by in situ polymerization (Figure 1). In order to enhance the compatibilization of the inorganic filler with the polymer matrix, an oligomer of PBS was intercalated between the layers of the clay. Composites with different percentages of filler (1, 3, 5, 10 wt%) and two different divalent cations (Zn or Mg) were prepared. The thermal, rheological and mechanical properties of the samples were investigated. The results showed that the materials feature a high thermal stability, in particular those containing Zn2+ cations. Rheological investigations highlighted a significant chain extender effect of the filler toward the matrix, thus revealing a huge reinforcing effect imparted by the clays, especially for composites with Mg2+ cations. Such findings were also supported by an increase up to 30% of the tensile and flexural strength for a PBS composite loaded with 3 wt% of Mg/Al-LDH, thus suggesting a uniform level of dispersion and a pronounced interfacial interaction between the filler and polymer [1-3]. The setting up of these biocomposites allows widening the field of application of PBS to sectors requiring better performances as well as barrier effect and opens such new strategy to other biopolymers.