Current synthetic nonwoven fiber
production methods typically require
transforming preformed polymers into a processable melt or solution
state by heating or adding organic solvents, respectively, to facilitate
fiber spinning. The significant energy demands and the use of volatile
organic compounds render these processes suboptimal. Furthermore,
conventional synthetic fiber manufacturing processes are limited to
thermoplastics because cross-linked thermosets do not flow; however,
the superior thermal and chemical resistance of cross-linked fibers
render them attractive targets. In this study, we describe a “cure
blowing” process that addresses these limitations by producing
cross-linked fibers at room temperature with little or no solvent,
using a lab-scale spinning die resembling those used for commercial
melt blowing, an approach that currently produces >10% of global
nonwovens.
Specifically, a photocurable liquid mixture of thiol and acrylate
monomers was extruded through an orifice and drawn by high-velocity
air jets at ambient temperature into liquid fibers which were cross-linked
into solid fibers by in situ photopolymerization during flight toward
the collector. The effect of process parameters on the fiber diameter
and morphology was investigated to understand the fundamental principles
of cure blowing. Two intrinsic process limitations were identified
in the drive to produce smaller yet uniform fibers, and strategies
to circumvent them were identified. We anticipate that cure blowing
may be an industrially relevant and environmentally friendly method
for producing cross-linked polymeric nonwovens for a wide range of
applications.
Incorporating graphene-based nanomaterials into thermosetting resins is challenging at an industrial-scale. To address this issue, we prepared a styrene masterbatch containing chemically modified graphene oxide (mGO) and added it to unsaturated polyester and vinyl ester resins via simple mechanical mixing to generate homogeneous mGO/resin dispersions. For comparison, oven-dried or freeze-dried mGO was also blended into resin using the same mechanical mixing conditions. At low mGO loading levels of 0.02−0.08 wt %, composites made with oven-dried or freeze-dried mGO show the highest increase in fracture toughness but also the most severe decrease in flexural strength, whereas composites prepared from the mGO masterbatch show the best dispersion homogeneity and better retention of flexural strength while exhibiting only slightly less increase in toughness. The masterbatch process offers an economical way of producing high-quality mGO/resin dispersions.
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