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

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.

Thermomechanical and Fire Properties of Polyethylene-Composite-Filled Ammonium Polyphosphate and Inorganic Fillers: An Evaluation of Their Modification Efficiency

“…Bending vibrations of these bands were expressed by the signals around 450 cm −1 . They were more pronounced for the composites filled with vermiculite, which is in line with our previous studies, indicating a powerful absorption band around 1000 cm −1 [26].…”

“…Before use, VM was subjected to milling with the knife mill Retsch GM200 with a knife rotational speed of 5000 rpm and 5 min, and was sieved by a Fritsch Analysette 3 mechanical siever using 100 µm mesh. The annealing process was carried out at a temperature of 1260 • C, and the chemical composition according to the manufacturer's data is 38.0-49.0% SiO 2 , 20.0-23.5% MgO, 12.0-17.5% Al 2 O 3 , 0.3-5.4% Fe 2 O 3 , 5.2-7.9% K 2 O, 0.0-1.2% FeO, 0.7-1.5% CaO, 0.0-0.8% Na 2 O, 0.0-1.5% TiO 2 , 0.0-0.5 Cr 2 O 3 , 0.1-0.3% MnO, 0.0-0.6% Cl, 0.0-0.6% CO 2 , 0.0-0.2% S. Broader information about the used fillers was presented in a previous works [25][26][27].…”

Grafted Lactic Acid Oligomers on Lignocellulosic Filler towards Biocomposites

“…Glass transition temperature (T g ), cold crystallization temperature (T cc ), and melting temperature (T m ) were determined for all biocomposites using DSC analysis. The crystallinity of the samples (X c ) was calculated according to the following Equation (2) [ 2 , 53 , 54 ]: where is a cold crystallization enthalpy; is a melting enthalpy; is a melting enthalpy of fully crystalline PLA, which is 93.6 J/g [ 55 ], and is a weight fraction of PLA in the biocomposites ( Table 4 ) or in neat PLA. Table 10 and Figure 8 show the results of DSC analysis.…”

Temperature Influence on Additive Manufactured Carbon Fiber Reinforced Polymer Composites

“…Several studies have shown that PLA, the polymer matrix employed in this FDM process, has a deflection temperature (HDT) near 55 • C [52,53]. HDT is a measure of the resistance of a polymer to deformation (stiffness of material) when subjected to stress loading at elevated temperatures.…”