Elastomeric biodegradable starch/bentonite nanocomposites. Structure-thermo-mechanical correlation and degradation...

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Corn starch (CS) based films are biodegradable but often lack mechanical strength and thermal stability.
• Nanoclay incorporation is a common strategy to enhance polymer properties.

Purpose of the Study:

• To develop and characterize novel elastomeric nanocomposite films using corn starch and bentonite nanoclay.
• To investigate the effect of bentonite nanoclay content on the structural, thermal, mechanical, and degradation properties of CS films.
• To evaluate the potential of these nanocomposites for food packaging and coatings in sub-ambient conditions.

Main Methods:

• Layered silicate nanocomposite films were prepared using corn starch, bentonite nanoclay, and glycerol as a plasticizer.
• Structural characterization (exfoliated vs. intercalated morphology) was determined by bentonite content (c_bentonite).
• Thermal properties (TGA, T_g), mechanical properties (Young's modulus E, stretchability, fracture energy), and biodegradability were evaluated.

Main Results:

• The developed films were elastomeric with stretchability of 60-90% and glass transition temperatures (T_g) between -75 to -85 °C.
• Exfoliated morphology (c_bentonite < 2 wt%) improved thermal stability, while intercalated morphology (c_bentonite > 3 wt%) was observed.
• Bentonite increased Young's modulus and reduced extensibility, with maximum toughness and modulus at 2.9 wt% bentonite.
• The nanocomposite films demonstrated biodegradability under both aerobic and anaerobic conditions, with slower degradation for the intercalated nanocomposite at 2.9 wt% bentonite under anaerobic conditions.

Conclusions:

• Corn starch-bentonite nanocomposites offer tunable properties for biodegradable applications.
• The optimal bentonite content (2.9 wt%) yields enhanced mechanical properties and toughness.
• These materials are suitable for developing advanced biodegradable food packaging and coatings for sub-ambient applications.