Abstract
One of the main issues in preparing polymer-based nanocomposites with effective properties is to achieve a good dispersion of the nanoparticles into the matrix. Chemical interfacial modifications by specific coupling agents represents a good way to reach this objective. Actually, time consuming compatibilization procedures strongly compromise the sustainability of these strategies. In this study, the role of particles’ architectures in their dispersion into a poly-lactic acid matrix and their subsequent influences on physical-chemical properties of the obtained nanocomposites were investigated. Two kinds of silica nanoparticles, “smooth” and “wrinkled,” with different surface areas (≈30 and ≈600 m2/g respectively) were synthesized through a modified Stöber method and used, without any chemical surface pre-treatments, as fillers to produce poly-lactic acid based nanocomposites. The key role played by wrinkled texture in modifying the physical interaction at the polymer-filler interface and in driving composite properties, was investigated and reflected in the final bulk properties. Detailed investigations revealed the presence of wrinkled nanoparticles, leading to (i) an enormous increase of the chain relaxation time, by almost 30 times compared to the neat PLA matrix; (ii) intensification of the shear-thinning behavior at low shear-rates; and (iii) slightly slower thermal degradation of polylactic acid.
Highlights
Poly-lactic acid (PLA) is one of the most promising “green plastics.” It is a bio-compostable and bio-degradable linear aliphatic polyester, typically derived from renewable sources, such as corn, starch and sugar beet
Detailed investigations revealed the presence of wrinkled nanoparticles, leading to (i) an enormous increase of the chain relaxation time, by almost 30 times compared to the neat PLA matrix; (ii) intensification of the shear-thinning behavior at low shear-rates; and (iii) slightly slower thermal degradation of polylactic acid
Different types of inorganic fillers have been used for the production of PLA-based nanocomposites such as carbon nanotubes (CNTs) [6,7,8], graphene [9,10,11], natural rubber [12,13,14], silicates [15,16] and cellulose [17,18,19]
Summary
Poly-lactic acid (PLA) is one of the most promising “green plastics.” It is a bio-compostable and bio-degradable linear aliphatic polyester, typically derived from renewable sources, such as corn, starch and sugar beet. In order to achieve excellent dispersion of the filler, many strategies have already been employed These include conventional synthetic approaches such as melt-extrusion processes [28], co-extrusion and solution casting [29,30,31,32]; the inclusion of interfacial modifications by specific coupling agents, including oleic acid, rubbers, L-lactic acid oligomers and 2-methacryloyloxyethyl isocyanate [33]; and/or surface pre-treatments of the reinforcing phase [34,35]. In our previous study [26], we proposed a novel, straightforward strategy, to produce PBT/SiO2 nanocomposites by using the same polymeric components as endogenous coupling agents This approach hinders the typical irreversible aggregation of silica particles and at the same time allows one to obtain blends at higher filler content without any coupling agent. Melt-mixing methodology was used to synthesize nanocomposites with 3 wt% of both smooth and wrinkled nanoparticles, and textural features of all synthesizes sample were carefully investigated
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