Thermomechanical and optical properties of biodegradable poly(L‐lactide)/silica nanocomposites by melt compounding

Abstract

Poly(L-lactide) (PLA)/silica (SiO 2 ) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO 2 nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO 2 nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO 2 nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glasstransition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving C¼ ¼O of PLA with SiAOH of SiO 2 was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO 2 nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO 2 concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers.

Supermolecular structure and nucleation ability of polylactide-based composites with silica/lignin hybrid fillers

“…Also for PLA/-graphene composites, that relationship was noticed [12]. In terms of T m , the discrepancy between reference sample (177.5°C) and composites (173.9-175.3°C) was not very vast and consistent with other papers [21,49].…”

“…More considerable reduction in the T c was reported for PLA/nanosilica composites [49] and for PLA with cellulose nanocrystals (CNC) [14]. T c for PLA/ 3 % nanosilica and for PLA/1 % CNC composite shifted to lower temperature at ca.…”

“….5°C, what is analogous to PLA sample (63°C) and does not implicate any significant difference. Wen et al [49] tested samples of PLA filled with different amounts of nanosilica (1, 3, 5, 7, 10 %). Results obtained by that team were the same as those presented in this paper-T g remained almost unchanged, indicating that the chain segment mobility of polymer matrix was not influenced by the introduction of SiO 2 nanoparticles.…”

“…Crystallization process is based on competition between the nucleation effect and polymer chain mobility for crystalline growth. Silica that is the main constituent of hybrid filler is well known for enhancing the X c in PLA-based composites [49][50][51]. Particularly, nanosilica, due to its small size, has a large specific surface that is responsible for nucleating effect [52].…”

Optical transparency and mechanical properties of semi-refined iota carrageenan film reinforced with SiO2 as food packaging material

“…The same result was reported on the incorporation of SiO2 into the Poly(L-lactide) (PLA) matrix. The elongation at break increased only a little in the PLA/SiO2 nanocomposites, so it seems that there was an insensitive effect on the toughness with the incorporation of SiO2 into the PLA matrix [33].…”