Effect of Biobased SiO2 on the Morphological, Thermal, Mechanical, Rheological, and Permeability Properties of PLLA/PEG/SiO2 Biocomposites

Abstract

Nowadays, companies and researchers are concerned about the negative consequences of using synthetic polymers and direct their efforts to create new alternatives such as biocomposites. This study investigated the effect of biobased SiO2 on the properties of poly(L-lactic acid)/SiO2 (PLLA/SiO2) and poly(L-lactic acid)/SiO2/poly(ethylene glycol) (PLLA/SiO2/PEG) composites. The SiO2 was obtained from rice husk incineration and mixed with PLLA at various concentrations (5, 10, and 15 wt.%) via melt extrusion before compression molding. Furthermore, PLLA/SiO2/PEG composites with various PEG concentrations (0, 3, 5, and 10 wt.%) with 10 wt.% SiO2 were produced. The sample morphology was studied by scanning electron microscopy (SEM) to analyze the dispersion/adhesion of SiO2 in the polymer matrix and differential scanning calorimetry (DSC) was used under isothermal and non-isothermal conditions to study the thermal properties of the samples, which was complemented by thermal stability study using thermogravimetric analysis (TGA). Rheological analysis was performed to investigate the viscoelastic behavior of the composites in the melt state. At the same time, tensile mechanical properties were obtained at room temperature to determine their properties in the solid state. DSC and X-ray diffraction analysis (XRD) were combined to determine the crystalline state of the samples. Finally, gas permeation measurements were performed using a variable pressure (constant volume) method to analyze the permeability of different gases (CO2, CH4, O2, and H2). The results showed that SiO2 decreased the PLLA chain mobility, slowing the crystallization process and lowering the gas permeability while increasing Young’s modulus, thermal stability, and viscosity. However, PEG addition increased the crystallization rate compared to the neat PLLA (+40%), and its elongation at break (+26%), leading to more flexible/ductile samples. Due to improved silica dispersion and PLLA chain mobility, the material’s viscosity and gas permeability (+50%) were also improved with PEG addition. This research uses material considered as waste to improve the properties of PLA, obtaining a material with the potential to be used for packaging.

Utilization of Spent Coffee Grounds as a Sustainable Resource for the Synthesis of Bioplastic Composites with Polylactic Acid, Starch, and Sucrose

“…The T m of SPT-5%, 10%, and 15% were 156 • C, which occurred in the second peaks (Figure 3c). The T m of the PLA-TPS was 152 • C. Morales et al [44] found that the melting point of neat PLA is 150 • C. This indicates that SCG can slightly delay the melting of bioplastics.…”

“…Ma et al [55] explained that adhesion of polymers could be enhances if the matrix was higher so that the interaction between the polymers would improve. SCG is a dust particle which can lead to a larger total surface area by adding more matrix, allowing the SCG to have a better bond with another polymer [44]. Based on the statistical data, the addition of 5 and 15% SCG was significantly different, while 10% SCG was not significantly different from 5 and 15% SCG.…”

“…The glass transition temperature (T g ) is the temperature at which the amorphous portion of the polymer structure becomes more mobile, causing side groups to slide and rotate [42]. The T g values of PLA-TPS and SPT-5%, 10%, and 15% were between 58-60 • C. However, neat PLA has a T g of 59.9 • C [44]. The T g showed no significant effect as the SCG content increased.…”

“…The highest tensile strength of the SPT bioplastics was achieved using SPT-5% (4.9 MPa). Neat PLA has a high tensile strength of 93 MPa, while neat poly l-lactic acid (PLLA) has a tensile strength value of 3.6 MPa [44]. PLA-TPS composites have a tensile strength value of 38.3 MPa (Figure 5b).…”

Synthesis of Ni-Cu-CNF Composite Materials via Carbon Erosion of Ni-Cu Bulk Alloys Prepared by Mechanochemical Alloying

“…Composite materials of various natures attract a growing interest of researchers and industrialists due to their unique properties and wide range of possible applications [1][2][3][4]. In turn, carbon nanomaterials (CNMs) possess high surface area, tailored porous structure, good electrical conductivity, etc.…”