Effect of Organic Modifier and Clay Content on Non-Isothermal Cold Crystallization and Melting Behavior of Polylactide/Organovermiculite Nanocomposites.

M Jesús Fernández,M Dolores Fernández

doi:10.3390/polym12020364

Abstract

In clay/polymer nanocomposites, the crystallization behavior and kinetics of the polymer can be affected by the presence of clay, its content and the degree of miscibility between the clay and the polymer matrix. The effect of two different organomodified vermiculites on the non-isothermal cold crystallization and melting behavior of polylactide (PLA) was studied by differential scanning calorimetry (DSC). In the presence of vermiculites, the cold crystallization of PLA occurred earlier, particularly for the highest content of the most miscible organovermiculite with PLA. The cold crystallinity of PLA decreased at low heating rates, notably at high organoclay loadings, and increased at high heating rates, especially at low vermiculite contents. According to the crystallization half-time, crystallization rate coefficient (CRC), and crystallization rate parameter (CRP) approaches, the cold crystallization rate of PLA increased by incorporating vermiculites, with the effect being most noteworthy for the vermiculite showing better compatibility. The Mo model was successful in describing the non-isothermal cold crystallization kinetics of the PLA/vermiculite composites. The melting behavior was affected by the heating rate and the type and content of clay. The nucleating effect of the most compatible clay resulted in the less perfect crystallites. The activation energy was evaluated using the Kissinger and Takhor methods.

Highlights

Polylactide (PLA) is a linear aliphatic polyester with excellent mechanical properties, thermal plasticity and biocompatibility, that has received a lot of attention in the last decades due to its renewable origin and biodegradability [1,2,3,4,5,6,7]
According to the crystallization half-time, crystallization rate coefficient (CRC), and crystallization rate parameter (CRP) approaches, the cold crystallization rate of PLA increased by incorporating vermiculites, with the effect being most noteworthy for the vermiculite showing better compatibility
The formation of a most exfoliated structure is observed in the case of PLA/ETOVMT nanocomposite, indicating that the compatibility with PLA is higher for this organomodified VMT due to favorable interactions of the hydroxyl groups of the intercalated surfactant cations in the clay with carbonyl functions of polymer chains [40,41]

Summary

Introduction

Polylactide (PLA) is a linear aliphatic polyester with excellent mechanical properties, thermal plasticity and biocompatibility, that has received a lot of attention in the last decades due to its renewable origin and biodegradability [1,2,3,4,5,6,7]. The applications of PLA are somewhat limited by some of its properties, such as brittleness and slow crystallization [6,8]. One approach to improve some of the physical and mechanical properties of PLA is the preparation of nanocomposites in combination with nanofillers [9,10]. PLA is a semicrystalline polymer, and its physical/mechanical properties are determined by the extent of crystallization and the crystalline morphology. The addition of nanofillers to a polymer matrix affects its mechanical properties and the crystallization and melt behavior, and its applications [17,18,19,20]. The understanding of the crystallization of both polymer and polymer composites is necessary for establishing the relationship among the processing conditions, the developed structure, and the properties of the final products

Methods

Results

Conclusion