The Effect of Surface Treatment with Isocyanate and Aromatic Carbodiimide of Thermally Expanded Vermiculite Used as a Functional Filler for Polylactide-Based Composites.

Mateusz Barczewski,Olga Mysiukiewicz,Arkadiusz Kloziński,Joanna Szulc,Radosław Biskup,Aleksander Hejna,Adam Piasecki,Sławomir Michałowski

doi:10.3390/polym13060890

Abstract

In this work, thermally expanded vermiculite (TE-VMT) was surface modified and used as a filler for composites with a polylactide (PLA) matrix. Modification of vermiculite was realized by simultaneous ball milling with the presence of two PLA chain extenders, aromatic carbodiimide (KI), and 4,4’-methylenebis(phenyl isocyanate) (MDI). In addition to analyzing the particle size of the filler subjected to processing, the efficiency of mechanochemical modification was evaluated by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The composites of PLA with three vermiculite types were prepared by melt mixing and subjected to mechanical, thermomechanical, thermal, and structural evaluation. The structure of composites containing a constant amount of the filler (20 wt%) was assessed using FTIR spectroscopy and SEM analysis supplemented by evaluating the final injection-molded samples’ physicochemical properties. Mechanical behavior of the composites was assessed by static tensile test and impact strength hardness measurements. Heat deflection temperature (HDT) test and dynamic thermomechanical analysis (DMTA) were applied to evaluate the influence of the filler addition and its functionalization on thermomechanical properties of PLA-based composites. Thermal properties were assessed by differential scanning calorimetry (DSC), pyrolysis combustion flow calorimetry (PCFC), and thermogravimetric analysis (TGA). The use of filler-reactive chain extenders (CE) made it possible to change the vermiculite structure and obtain an improvement in interfacial adhesion and more favorable filler dispersions in the matrix. This translated into an improvement in impact strength and an increase in thermo-mechanical stability and heat release capacity of composites containing modified vermiculites.

Highlights

Polylactide (PLA) is a biobased polymer that attracted attention recently because of its good performance and processing properties, and relatively high availability compared to the rest of the commercially used biodegradable thermoplastic polyesters [1,2]
This work is aimed to evaluate the possibility of simultaneous ball milling of expanded vermiculite with chain extenders to manufacture the filler for PLA-based composites
In modify the presented study,chemistry a novel mechanochemical methodexpanded was successfully applied to the surface and shape of thermally vermiculite, which to modify the surface chemistry and shape of thermally expanded vermiculite, which was was used as a filler in polylactide composites

Summary

Introduction

Polylactide (PLA) is a biobased polymer that attracted attention recently because of its good performance and processing properties, and relatively high availability compared to the rest of the commercially used biodegradable thermoplastic polyesters [1,2]. Despite many advantages that made PLA an exceedingly popular polymer, it has some disadvantages that significantly limit its use These include susceptibility to hydrolytic degradation during melt processing, high brittleness, and low glass transition temperature [2,3,4]. The most common modifications to the structure of the polylactide itself can be carried out by heterogeneous nucleation realized in order to increase crystallinity [5,6] or the use of chain extenders to increase its molecular weight [7,8,9,10] Another solution that allows increasing the range of applicability, mostly from the point of view of toughness improvement, is the production of reactive mixtures of polylactide with other biodegradable polymers [11,12]

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