Impact of the Graphite Fillers on the Thermal Processing of Graphite/Poly(lactic acid) Composites

Abstract

To assess the impact of graphite fillers on the thermal processing of graphite/poly(lactic acid) (PLA) composites, a series of the composite samples with different graphite of industrial grade as fillers was prepared by melt mixing. The average size of the graphite grains ranged between 100 µm and 6 µm. For comparative purposes, one of the carbon fillers was expandable graphite. Composites were examined by SEM, FTIR, and Raman spectroscopy. As revealed by thermogravimetric (TG) analyses, graphite filler slightly lowered the temperature of thermal decomposition of the PLA matrix. Differential scanning calorimetry (DSC) tests showed that the room temperature crystallinity of the polymer matrix is strongly affected by the graphite filler. The crystallinity of the composites determined from the second heating cycle reached values close to 50%, while these values are close to zero for the neat polymer. The addition of graphite to PLA caused a slight reduction in the oxidation induction time (OIT). The melt flow rate (MFR) of the graphite/PLA composites was lower than the original PLA due to an increase in flow resistance associated with the high crystallinity of the polymer matrix. Expandable graphite did not cause changes in the structure of the polymer matrix during thermal treatment. The crystallinity of the composite with this filler did not increase after first heating and was close to the neat PLA MFR value, which was extremely high due to the low crystallinity of the PLA matrix and delamination of the filler at elevated temperature.

Antioxidant activity of mango seed wax additive on the properties of poly(lactic acid) transparent films for food packaging application

“…Kaczor et al studied the thermal stability of PLA/graphite composites at 230°C, and there was a reduction observed. [ 53 ] The antioxidant potential also decides the performance in OIT analysis. The incorporation of strong antioxidants like carnosic acid into polyethylene improved the induction time by 12‐fold.…”

Introduction to Modelling the Correlation Between Grain Sizes of Feed Material and the Structure and Efficiency of the Process of Co-Rotating Twin-Screw Extrusion of Non-Flammable Composites with a Pla Matrix

“…The conducted research shows that the addition of pre-expanded graphite reduces the melting enthalpy and the cold crystallization enthalpy in the second heating and increases the cold crystallization temperature. This effect may be due to the large size of graphite flakes (~400 μm), which makes it difficult to obtain sufficient dispersion of graphite in the polymer matrix [24]. For sample S1 during the first heating, the presence of two melting peaks was observed.…”

“…Among graphitic fillers, the expandable graphite attracts attention due to its flame retardant properties. If it is heated, the flakes will expand and cut off the access of oxygen, which is called as 'intumescent effect' [1,[24][25][26][27].…”

Cellulose/Expandable Graphite Composite Aerogels with Good Flame- Retardant and Filtration Performance

“…4a, the thermal decomposition process of EG can be divided into three stages. In the rst stage ( ), the mass loss accounted for approximately 1% at 0-230°, which is the direct volatilization of small molecules and water (Kaczor et al 2021). In the second stage ( ), the mass loss was approximately 25% at 230-500 ℃, which was primarily due to the expansion of graphite and was the largest of the three stages.…”