Enhancing the Mechanical Properties of Biodegradable Polymer Blends Using Tubular Nanoparticle Stitching of the Interfaces

Abstract

"Green" polymer nanocomposites were made by melt blending biodegradable poly(lactic acid) (PLA) and poly(butylene adipate-co-butylene terephthalate) (PBAT) with either montmorillonite clays (Cloisite Na(+)), halloysite nanotubes (HNTs), the resorcinol diphenyl phosphate (RDP)-coated Cloisite Na(+), and coated HNTs. A technique for measuring the work of adhesion (Wa) between nanoparticles and their matrixes was used to determine the dispersion preference of the nanoparticles in the PLA/PBAT blend system. Transmission electron microscopy (TEM) images of thin sections indicated that even though both RDP-coated nanotubes and clay platelets segregated to the interfacial regions between the two immiscible polymers, only the platelets, having the larger specific surface area, were able to reduce the PBAT domain sizes. The ability of clay platelets to partially compatibilize the blend was further confirmed by the dynamic mechanical analysis (DMA) which showed that the glass transition temperatures of two polymers tended to shift closer. No shift was observed with either coated or uncoated HNTs samples. Izod impact testing demonstrated that the rubbery PBAT phase greatly increased the impact strength of the unfilled blend, but addition of only 5% of treated clay decreased the impact strength by nearly 50%. On the other hand, an increase of 9% relative to the unfilled blend sample was observed with the addition of 5% treated nanotubes. TEM cross-section analysis confirmed that the RDP-coated clay platelets covered most of the interfacial area. On one hand, this enabled them to reduce the interfacial tension effectively; on the other hand, it prevented chain entanglements across the phase boundary and increased the overall brittleness, which was confirmed by rheology measurements. In contrast, the RDP-coated HNTs were observed to lie perpendicular to the interface, which made them less effective in reducing interfacial tension but encouraged interfacial entanglements across the interface, resulting in "stitching" of the interface and an increase in the Izod impact of the blend.

Flame Retardant Polymer Nanocomposites and Interfaces

“…Given that the aspect ratio of exfoliated clay platelets could be several magnitudes larger than that of clay tactoids, it is easier for the micro-cracks to enlarge and propagate under external stress in the exfoliated polymer/clay blend. Moreover, a similar result was also found in binary polymer blends with clay [47]. When C-Na + , C-RDP clay and C-30B clay were added to a biodegradable PLA/poly(butylene adipate-co-butylene terephthalate) (PBAT) blend, C-30B performs best in reducing the domain size and increasing compatibility between two polymers, as can be seen in Figure 9.…”

“…For binary polymer systems, the morphology of the polymer phase separation and filler location play a significant role in the rheological response. In previous section, Guo, et al [47,56] showed that the addition of C-30B and C-RDP could effectively increase the compatibility between PLA and PBAT, while reducing the impact strength due to the strong barrier effect at the polymer interface. HNTs and H-RDP were not as effective at reducing the domain size and increasing the polymer compatibility, but the impact strength was enhanced with the "stitching" effect of nanotubes.…”

Roles of Interfacial Tension in Regulating Internal Organization of Low Bandgap Polymer Bulk Heterojunction Solar Cells by Polymer Additives

“…The interfacial tension between the two polymers can be then determined via the Young's equationwhere γ pcdtbt and γ ps are, respectively, the surface tensions of PCDTBT and PS, γ inter is the interfacial tension, and θ is Young's contact angle between PCDTBT and PS. γ pcdtbt and γ ps were first measured as a function of temperature using the two‐liquid (water and diiodomethane) contact angle method, where the surface tension of a given polymer can be computed by using the measured θ of polar (i.e., water) and nonpolar (i.e., diiodomethane) liquids on the polymer thin film. γ pcdtbt and γ ps for varying PS MW (from 50K to 7M Da) were determined at five different temperature points (between 20 °C and ≈50 °C) and linearly extrapolated to higher temperatures as shown in Figure a.…”

Porous fibers surface decorated with nanofillers: From melt‐spun PP/PVA blend fibers with silica nanoparticles

“…A large number of water-soluble polymers are available as sacrificial polymers, such as polyvinyl alcohol (PVA), 10,11 poly(ethylene oxide), [12][13][14] polyvinylpyrrolidone, 15 and sulfopolyester 16,17 to avoid any toxicity problem during the process. Nanoparticles give polymer materials additional properties (e. g., electrical, 18,19 mechanical, 20,21 flame retardant, 22,23 and antimicrobial 24,25 ). The porous material has a high specific surface area, and the internal structure is an ideal host for the integration of these nanoparticles.…”