Nanosilk-Grafted Poly(lactic acid) Films: Influence of Cross-Linking on Rheology and Thermal Stability

Abstract

This article reports a novel fabrication of branched cum cross-linked poly(lactic acid) (PLA) with nanosilk fibroin with graft chain topology by reactive extrusion process. It could be possible by the addition of a small amount of radical initiator (dicumyl peroxide (DCP)). Grafting of silk nanocrystals (SNCs) on PLA macromolecules that provides remarkable improvement in the rheological and thermal properties of the latter are confirmed by 1H NMR and Fourier transform infrared investigation. Significant improvement is observed in zero shear viscosities, and the crossover point shifts to lower frequencies as compared to the branched and cross-linked PLA system. Along with SNC grafting, the crystallization process is also enhanced and stable crystals appeared during cooling, which results in a single melting peak. The rate of crystallization of PLA has been improved although the percentage crystallinity reduces with DCP content, as higher grafting and cross-linking restricts the chain segmental motion, which is critical for crystallization process. Furthermore, SNC grafting increases the reprocessability performance of PLA and provides higher rheological properties as compared to the branched and cross-linked PLA at all reprocessing cycles.

Recent Advances in Bioplastics: Application and Biodegradation

“…Chain extenders such as diisocyanate, epoxy resins, and others are frequently used to increase the molecular weight of PLA [265]. The post-polymerisation modification usually refers to cross-linking using irradiation, which reduces the mobility of PLA, thereby improving its toughness, processing performance, and thermal stability [266,267].…”

Compostable composites of wheat stalk micro‐ and nanocrystalline cellulose and poly(butylene adipate‐co‐terephthalate): Surface properties and degradation behavior

“…33 Figure 1 presents the typical morphological illustration of one of the composites on the basis of SEM analysis. GPC analysis was carried out using Shimadzu LC Solution Chromatograph with refractive index detector (RID-10A), at 1 mL/min eluent flow rate and 40 μL sample injection volume.…”

“…With increase in the soil burial period [ Figure 9(a,b)], the amount of the fillers decrease which completely vanish after 4 months of soil burial [see Figure 9(c,d)]. 33,66,67 The samples became mechanically unstable and brittle upon soil burial for 4 months. 33,66,67 The samples became mechanically unstable and brittle upon soil burial for 4 months.…”

“…The instrument was calibrated with polystyrene (PS) standards. 33 Figure 1 presents the typical morphological illustration of one of the composites on the basis of SEM analysis. The lower and higher magnification SEM micrographs depicting the internal morphology of the composite comprising 40 weight fraction MCC (i.e., the sample M-40) is shown in Figure 1.…”

“…At the same time, the PBAT matrix gets teared in random way further implying that the cellulosic filler augments the degradation of the PBAT. 33,66,67 The samples became mechanically unstable and brittle upon soil burial for 4 months. Thus, even the sample collection after more than 4 months of degradation was not possible.…”