Effect of Mixing Strategy on the Structure-Properties of the PLA/PBAT Blends Incorporated with CNC

Deniz Sema Sarul,Mohammadreza Nofar,Dogan Arslan,Reza Salehiyan,Emre Vatansever,Yusuf Kahraman,Ali Durmus

doi:10.32604/jrm.2022.017003

Deniz Sema Sarul, Mohammadreza Nofar + Show 5 more

Open Access

https://doi.org/10.32604/jrm.2022.017003

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Abstract

Polylactide (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blend nanocomposites including 3 wt% of cellulose nanocrystals (CNCs) were prepared by melt compounding method in a twin-screw extruder and an internal mixer. Blend nanocomposites were formulated by diluting three different masterbatches prepared by solution casting method that contained 7 wt% of CNC. These masterbatches were: (m1) PLA/PBAT/CNC masterbatch; (m2) PLA/CNC masterbatch; and (m3) PBAT/CNC masterbatch. These were to explore how different preparation methods affect the dispersion and localization of CNC and hence the properties of PLA/PBAT/CNC blend nanocomposites. Scanning electron microscopy (SEM) was used to study the structural changes of the blends. Rheological properties of PLA/PBAT blends and PLA/PBAT/CNC blend nanocomposites were also investigated. In the samples prepared by internal mixer, the rheological behavior of blend nanocomposite prepared through premixing of CNC particles with PLA showed a transition from liquid-like to a gel-like behavior. According to the rheological results and differential scanning calorimetry (DSC) analysis, it was found that the CNC overall enhanced the viscoelastic properties of blends and improved the PLA crystallization, respectively. Dynamic mechanical analysis (DMA) illustrated that the incorporation of CNC also enhanced the elastic modulus of PLA/PBAT blends specifically above the glass transition temperature of PLA. The expected improvements in mechanical properties did not occur due to the possible existence of residual solvent in the blends.

Highlights

We aimed to explore the morphological, rheological, crystallization, thermomechanical, and mechanical properties of PLA/PBAT blends and blend nanocomposites containing 3 wt% cellulose nanocrystals (CNCs) prepared through dilution of solution casted masterbatch via melt mixing method using (a) a twin-screw extruder (TSE) and (b) an internal mixer (IM)
Regardless of the type of used masterbatch, it was observed that the droplet size of dispersed phase in the neat blend prepared through IM was larger than that of the blend prepared by TSE
In the m3 strategy where CNC particles are pre-mixed with PBAT, there was no enough time in mTSE for CNC to migrate from PBAT to PLA

Summary

Introduction

Bio-based and/or biodegradable polymer studies have remarkably increased in recent years due to the concerns about environmental effects of petroleum-based polymers and consumption of crude oil. Polylactide (PLA) is one of the most promising bio-based polymers due to its 100% biobased synthetic route and fully biodegradable nature, reasonable mechanical strength, and commercial availability [1,2,3,4]. PLA lacks some crucial characteristics like flexibility, melt strength, and fast crystallization rate [3,5]. The economically and technically most viable method to overcome these drawbacks is the blending of PLA with high impact bioplastics like poly (butylene adipate-coterephthalate) (PBAT). Some studies have shown that blending of PLA with PBAT can improve the toughness of PLA, but significantly decreases the modulus and mechanical strength of PLA. It has been reported that PLA/PBAT blends are generally completely immiscible [3,6,7]

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