Poly(lactic acid) (PLA) has a significant potential as a biodegradable polymer, but its high cost and slow biodegradability restrict its use in disposable products. This study establishes a novel route to accomplish both objectives by the addition of low‐cost soy fillers into PLA, which reduced material cost and increased the degradation rate of resulting soy‐PLA fibers. Due to partial thermal degradation of soy fillers at PLA melt temperature, they could be melt‐compounded into PLA up to 5 wt%. Fine continuous fibers (D ∼ 25‐50 μm) were successfully produced via melt spinning, and further melt‐consolidated into prototypical nonwovens. The tensile strength of soy‐PLA fibers containing soy reside and soy flour were 56 ± 9 and 44 ± 5 MPa, respectively. Although slightly lower than that of neat PLA fibers (74 ± 2 MPa), the fibers possessed adequate tenacity for use as nonwoven fabrics. Fiber modulus remained unaffected at about 2.5 GPa. The soy‐PLA fibers displayed a relatively rough exterior surface and provided a natural‐fiber feel. The overall degradation of soy‐PLA fibers was accelerated about 2‐fold in a basic medium due to the preferential dissolution of soy that led to increased surface area within the PLA matrix indicating their potential for use in biodegradable nonwovens.
With shrinking size of electronic devices, increasing performance and accompanying heat dissipation, there is a need for efficient removal of this heat through packaging materials. Polymer materials are attractive packaging materials given their low density and electrical insulating properties, but they lack sufficient thermal conductivity that inhibits heat transfer rate. Hexagonal boron nitride (BN) possesses excellent thermal conductivity and is also electrically insulating, therefore BN-filled polymer composites were investigated in this study. Results showed successful continuous extrusion of BN-filled linear low-density polyethylene through micro-textured dies that is a scalable manufacturing process. Through-thickness thermal conductivity measurements established that 30 vol% BN content led to an over 500% increase in thermal conductivity over that of pure polymer. Textured film surface provided about a 50% increase in surface area when compared with non-textured films. This combination of increased surface area and enhanced thermal conductivity of BN-filled textured films indicates their potential application for improved convective thermal transport.
Herein, a series of poly(vinyl alcohol) (PVA)–lignin
hydrogel
composites was synthesized by crosslinking both unfractionated and
fractioned lignin of varying molecular weights directly with PVA via
a condensation reaction involving glutaraldehyde (GA) as the crosslinker.
The fractionated lignin was obtained from a liquid–liquid extraction
process of bulk lignin obtained from Kraft black liquor. The mechanical
properties of the hydrated PVA–lignin composites were characterized
using ultimate tensile strength (UTS) testing, dynamic mechanical
analysis (DMA), and mechanical indentation. Most notably, soft composites
containing 40 wt % fractionated lignin and 3 wt % GA exhibited 2 orders
of magnitude increase in UTS when compared to neat PVA. The storage
moduli obtained from DMA were used to calculate the molecular weight
between crosslinks (M
C) of the various
soft composites, where a direct correlation between enhanced mechanical
properties and lower M
C for soft composites
containing fractionated lignin was observed. Finally, the hydrated
network structure of the hydrogels was directly imaged using scanning
electron microscopy. These images showed a more disrupted network
structure for soft composites containing unfractionated lignin, potentially
explaining the unpredictability in mechanical properties observed
for these composite hydrogels.
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