Morpho-Structural, Thermal and Mechanical Properties of PLA/PHB/Cellulose Biodegradable Nanocomposites Obtained by Compression Molding, Extrusion, and 3D Printing

Abstract

Biodegradable blends and nanocomposites were produced from polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB) and cellulose nanocrystals (NC) by a single step reactive blending process using dicumyl peroxide (DCP) as a cross-linking agent. With the aim of gaining more insight into the impact of processing methods upon the morphological, thermal and mechanical properties of these nanocomposites, three different processing techniques were employed: compression molding, extrusion, and 3D printing. The addition of DCP improved interfacial adhesion and the dispersion of NC in nanocomposites as observed by scanning electron microscopy and atomic force microscopy. The carbonyl index calculated from Fourier transform infrared spectroscopy showed increased crystallinity after DCP addition in PLA/PHB and PLA/PHB/NC, also confirmed by differential scanning calorimetry analyses. NC and DCP showed nucleating activity and favored the crystallization of PLA, increasing its crystallinity from 16% in PLA/PHB to 38% in DCP crosslinked blend and to 43% in crosslinked PLA/PHB/NC nanocomposite. The addition of DCP also influenced the melting-recrystallization processes due to the generation of lower molecular weight products with increased mobility. The thermo-mechanical characterization of uncross-linked and cross-linked PLA/PHB blends and nanocomposites showed the influence of the processing technique. Higher storage modulus values were obtained for filaments obtained by extrusion and 3D printed meshes compared to compression molded films. Similarly, the thermogravimetric analysis showed an increase of the onset degradation temperature, even with more than 10 °C for PLA/PHB blends and nanocomposites after extrusion and 3D-printing, compared with compression molding. This study shows that PLA/PHB products with enhanced interfacial adhesion, improved thermal stability, and mechanical properties can be obtained by the right choice of the processing method and conditions using NC and DCP for balancing the properties.

Correlation between Processing Parameters and Degradation of Different Polylactide Grades during Twin-Screw Extrusion

“…Polylactide is more and more commonly used in the production of composites reinforced with lignocellulosic fillers of natural origin [34][35][36][37] as well as in the production of blends with different polymers characterized by a significantly higher recommended processing temperature [38][39][40] or in contrast those more susceptible to thermal degradation [41,42]. The most commonly used technology for manufacturing biopolymers and their composites at an industrial scale is co-rotating twin-screw extrusion, due to its high throughput and mixing efficiency [43,44].…”

Extending Cellulose-Based Polymers Application in Additive Manufacturing Technology: A Review of Recent Approaches

“…Furthermore, 3,6-dimethyl-1,4-dioxane-2,5-dione as L-lactide monomer was surface grafted on CNF also was able to improve the homogeneity in the PLA matrix, and it was found that the crystallinity of the extruded filaments increased about 100% [ 89 ]. On the other hand, PLA, poly(3-hydroxybutyrate), and CNC crosslinked with dicumyl peroxide was investigated for its properties through various fabrication techniques, as shown in Figure 4 [ 90 ]. While the dicumyl peroxide addition improved the homogeneity of CNC in the polymer matrix and enhanced the interfacial adhesion between the polymers.…”

“… Schematic representation of PLA/PHB blends and nanocomposites preparation and processing of films, filaments, and 3D-printed meshes [ 90 ]. …”

Printability, Mechanical and Thermal Properties of Poly(3-Hydroxybutyrate)-Poly(Lactic Acid)-Plasticizer Blends for Three-Dimensional (3D) Printing

“…Bioplastics are already used in an increasing number of branches, e.g., packaging, catering products, agriculture, coatings and adhesives, toys, textiles, electronics, automotive, building and construction, medical applications, and many other sectors. Biopolymers PLA (poly(lactic acid)) and PHAs (polyhydroxyalkanoates) are generally well-researched and are the prime leaders of biopolymers production capacity growth [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ].…”