Preparation and Characterization of High Molecular Weight
Atactic Poly(vinyl alcohol)/Clay Composite Fibers
by Gel Spinning
Won Seok Lyoo 1, Dong Gyu Park1, Min Jae Kim1, Seok Kyun Noh2, Sung Soo Ham1,
Sang Woo Joo3, and Yong Sik Chung4
1
Division of Advanced Organic Materials, School of Textiles, Yeungnam University,
Gyeongsan 712-749, Korea
2
School of Display and Chemical Engineering, Yeungnam University, Gyeongsan 712-749,
Korea
3
School of Mechanical Engineering, Yeungnam University, Gyongsan 712-749, Korea
4
Department of Textile Engineering, Chunbuk National University, Jeonju 561-756, Korea
*E-mail: wslyoo@yu.ac.kr, Phone: +82-53-810-2786, Fax: +82-53-810-4761
Introduction
Recently, due to the development of composite techniques, there has been growing interest
in the field of composite and their special properties. At present, polymer/clay hybrids are one
of the most important classes of synthetically engineered materials. They can be transformed
into new materials possessing the advantages of both organic materials, such as light weight,
flexibility, and good mold-ability, and inorganic materials, such as high strength, heat stability,
and chemical resistance. Clay composite which incorporated hydrophilic organic polymer
exhibit enhanced interfacial interactions through hydrogen bonding as polymer molecules are
absorbed on the clay surface. Poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO)
have been studied extensively for their interactions with clay.
PVA is a semicrystalline polymer that is biocompatible and water-soluble, and it has a good
formation ability for fibrous materials. Its flexibility and toughness are good, so it is a typical
synthetic polymer that is used to improve the physical properties through mixing with other
materials that have poor physical properties.
In this study the effect of clay on the structure, morphology, and the thermo-mechanical
properties of PVA/clay composites (PCC) fibers by gel spinning was investigated. The
PVA/clay/dimethyl sulfoxide(DMSO)/water spinning dopes were prepared at 90 °C for 5 h
through the mixing of PVA particles and clay/DMSO/water dispersion solutions. The spinning
dopes and then filtered, and bubbles were removed. PCC solutions with clay contents of 0, 3,
5, 7, 10 and 20 wt% were analyzed with a rheometer to elucidate the effect of clay particles
on the viscoelastic properties of the spinning dopes. We also examined the relationship
between the properties and structures of the PVA/clay hybrid fibers with WAXD, FT-IR. The
structure and morphology of PCC fibers were observed with scanning electron microscopy
(SEM). More direct evidence for the formation of a true nanoscaled composite was provided
by the transmission electron microscopy (TEM). The thermal behavior of PCC fibers were
investigated with differential scanning calorimetry (DSC), and thermogravimetric analysis
(TGA). The mechanical properties of PCC fibers were determined with Instron MICRO350
automated materials testing system. The same analyses were also performed, for comparison
purpose, on hybrid samples containing the clay, prepared using the same processing
conditions.
Experimental
Materials
To synthesize high molecular weight (HMW) a-PVA having a number average degree of
polymerization of 4000, Vinyl acetate (VAc) was suspension polymerized in water at 40 ℃
with 2,2’-azobis(2,4-dimethylvaleronitrile) (ADMVN) as an initiator, and subsequent
saponification. The synthetic fluorinated mica (SOMASIFTM ME-100 purchased from COOP Chemical Co., Japan) is a layered silicate clay with chemical composition of Si (26.5
wt%), Mg (15.6 wt%), Al (0.2 wt%), Na (4.1 wt%), Fe (0.1 wt%), F (8.8 wt%) and cationic
exchange capacity (CEC) of 120 mequiv/100g.
Preparation of PCC solution
The PVA/Clay/DMSO/water spinning dopes were prepared at 90 °C for 5 h through the
mixing of PVA and PCC powders. The total concentration of PVA and Clay was 12 wt%, and
the weight ratios of PVA to Clay were 100/0, 95/5, 90/10, and 80/20, respectively. The
spinning dopes and then filtered, and the bubbles were removed.
Preparation of PCC fibers
The spinning solutions were filtered to remove any undissolved solids such as impurities.
And the bubbles were removed. Gel spinning was performed by the extrusion of the dope
from a nozzle 1 hole, of which the diameter was 0.55 mm with air gap of 15 mm at 90 °C, and
then immediately coagulated in methanol at -15 °C. The dopes were extruded in methanol and
then washed, and drawn, and its drawn ratio were 2. The obtained fibers were immersed in
methanol for 24 h to remove DMSO thoroughly and dried.
Characterization
The structure and morphology of PCC fibers were observed with scanning electron
microscopy (SEM). More direct evidence for the formation of a true nanoscaled composite
was provided by the transmission electron microscopy (TEM). The thermal behavior of PCC
fibers were investigated with differential scanning calorimetry (DSC), and thermogravimetric
analysis (TGA). The mechanical properties of PCC fibers were determined with Instron
MICRO350 automated materials testing system.
Results and Discussion
Cross section SEM images of undrawn PCC fibers with various clay contents were shown in
Figure 11. As clay content increases, it was found that cross section of PCC fiber was getting
rougher and aggregation was increasing. When clay is added more than 20 wt%, the
formation of cross section becomes distorted, and excessive clay aggregation causes
unstability in surface of polymer and clay, and mechanical property can be anticipated.
Figure 1. Cross-section SEM images of undrawn pure PVA and PCC fibers with various clay
contents: a, 0 wt%; b, 3.0 wt%; c, 5.0 wt%; d, 7.0 wt%; e, 10 wt%; f, 20 wt%.
This TEM photograph demonstrated that most of the clay layers were exfoliated and
dispersed homogeneously into the PVA fibers. The clay layers were also shown to be well
dispersed in the PVA fibers by the WAXD profiles, as discussed previously. For high clay
concentrations (≥ 10 wt%), however, some of the clays were well agglomerated structures
form and become denser in the PVA fiber above a critical concentration of 10 wt%.
Figure 2. TEM photographs of PCC fibers with various clay contents: a, 5 wt%; b, 7 wt%; c, 10 wt%.
Acknowledgements
This work was supported by grant No. RTI04-01-04 from the Regional Technology
Innovation Program of the Ministry of Knowledge Economy (MKE).
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