Surface Modification and Physical Properties of Various
UHMWPE-Fiber-Reinforced Modified Epoxy Composites
S. P. Lin,1J. L. Han,2J. T. Yeh,3F. C. Chang,4K. H. Hsieh1,5
1Institute of Polymer Science and Engineering, National Taiwan University, Taipei, Taiwan 106
2Department of Chemical and Materials Engineering, National I-Lan University, I-Lan, Taiwan 260
3Department of Textile Science, Nanya Institute of Technology, Taoyuan, Taiwan 414
4Department of Applied Chemistry, National Chiao Tung University, Hsin-Chu, Taiwan 300
5Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 106
Received 11 July 2006; accepted 3 November 2006
Published online in Wiley InterScience (www.interscience.wiley.com).
surface treatment and chemical agent treatment—were used
to investigate their effects on the surface properties of ultra-
high-molecular-weight polyethylene (UHMWPE) fibers. In
the analyses, performed using electron spectroscopy for
chemical analysis, changes in weight, and scanning electron
microscope observations, demonstrated that the two fiber-
surface-modified composites formed between UHMWPE
fiber and epoxy matrix exhibited improved interfacial adhe-
sion and slight improvements in tensile strengths, but nota-
ble decreases in elongation, relative to those properties of the
composites reinforced with the untreated UHMWPE fibers.
In addition, three kinds of epoxy resins—neat DGEBA, poly-
Two surface modification methods—plasma
urethane-crosslinked DGEBA, and BHHBP-DGEBA—were
used as resin matrices to examine the tensile and elongation
properties of their UHMWPE fiber-reinforced composites.
From stress/strain measurements and scanning electron
microscope observations, the resin matrix improved the
elongation. ? 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104:
Key words: epoxy (DGEBA); polyurethane; ultrahigh-
molecular-weight polyethylene (UHMWPE) fibers; tensile
strength; interfacial adhesion in composites; plasma surface
treatment; chemical agent treatment
Epoxy resins are vitally important constituents in
many manufacturing composite materials. Because of
high glass transition temperature and being quite
hard and brittle by nature, many thermoplastic poly-
mers modified epoxy resin systems were developed to
improve the toughness. The polyurethane (PU) modi-
fied epoxy resins1,2exhibit a number of advantageous
properties, including high processability, low shrink-
age, good mechanical stability, and resistance to heat
and chemical agents. Fiber-reinforced polymer com-
posites are used widely because of their excellent
properties, such as light weights and high specific
strengths and moduli. Fibers that are excellent rein-
forcing materials include carbon fiber,3,4glass fiber,5–8
aramid fiber, and ultrahigh-molecular-weight poly-
ethylene (UHMWPE) fiber.9,10The advantagesof using
UHMWPE fiber are its high tensile strength, high ten-
sile modulus, light weight, and high resistance toward
chemical and physical degradation. Unfortunately, it
also exhibits several drawbacks, such as a low surface
energy and poor creep and heat resistances.
The interface between the reinforcing UHMWPE
fiber and a matrix plays an important role in deter-
mining the mechanical properties of a UHMWPE
fiber-reinforced composite. Many researchers have
attempted to improve the surface properties of
UHMWPE fibers through such processes as the T-peel
strength of composites increased with the corona dis-
charging treatment,11chemical grafting methods to
make the UHMWPE wettable or capable of reaction
with the matrix,12acid etching methods to roughen the
surface and increase wettability,13laser irradiation,
oxygen-plasma treatment of the UHMWPE fiber
increases the transverse tensile strength and failure
strain of UHMWPE fiber/vinylester composites and
changes the failure initiation site from the interface to
interior of the UHMWPE fiber,14and high-energy UV
irradiation method may decreases the tensile properties
but increases the crystallinity of the UHMWPE fiber.15
There are also many surface modification methods
about aramid fiber reinforced polymer composites
included plasma treatment,16UV radiation method,17
and chemical agent treatment.18,19Aramid fiber is a
polar fiber that adheres well to the polymer matrix in
the composite because of attractive hydrogen bonding
and other polar interactions.
Correspondence to: K. H. Hsieh (email@example.com).
Contract grant sponsor: National Science Council, Taiwan;
contract grant number: NSC 92-2622-E-011-020.
Journal of Applied Polymer Science, Vol. 104, 655–665 (2007)
C2007 Wiley Periodicals, Inc.
In this study, two UHMWPE fiber surface modifica-
tion methods included plasma and chemical agent
surface treatments were applied to investigate the
resulting surface properties using electron spectros-
copy for chemical analysis (ESCA), weight change
methods, and scanning electron microscope (SEM)
observations. In addition, we used three kinds of ep-
oxy resin matrices—neat DGEBA, PU-crosslinked
DGEBA, and BHHBP-grafted DGEBA—to examine
the tensile and elongation properties of various rein-
forced composites. SEM observations of fracture sur-
faces suggested the existence of improved interfacial
adhesion and wet-out properties.
The materials used in the research are listed in Table I.
Epoxy resin (DGEBA; diglycidyl ether of bisphenol A;
EEW ¼ 186) and PBA 1000 polyol (Poly(tetramethyl-
ene adipate) glycol, M.W. ¼ 1000) were heated and
degassed under vacuum overnight prior to use.
Preparation of PU-crosslinked DGEBA resin
Figure 1 displays FTIR spectra recorded during the
synthesis of the PU-crosslinked DGEBA. A broad
peak for the OH groups (3500 cm?1) of PBA 1000 polyol
appears in Figure 1(a) in the spectrum of the initial
state of the reaction. Purging with dried nitrogen gas
was performed to remove both air and moisture from
the reaction kettle before 2 equiv. of MDI and 1 equiv.
of PBA 1000 polyol were added [Fig. 1(b)]. In the mid-
dle stages of the reaction, the peak intensity of the sig-
nal of the OH groups (3500 cm?1) decreased gradually
and eventually disappeared while that of the NCO
groups (2270 cm?1) reduced to half of its original in-
tensity (based on the peak of the 1,4-disubstituted ben-
zene units at 840 cm?1); in addition, a signal for the
carbonyl groups (C¼ ¼O) of urethane linkages (1740
cm?1) was generated. At this point, DGEBA was
added into the reaction system, whose spectrum
appears in Figure 1(c). In the final stage of the reac-
tion, the peak intensity of the residual NCO groups
(2270 cm?1) reduced continuously until it finally dis-
appeared [Fig. 1(d)]. The changes in the peak inten-
sities of the carbonyl (1740 cm?1) and NCO (2270
cm?1) groups indicates the progress of the chemical
reaction toward the PU-crosslinked DGEBA. The mo-
lecular structure of the PU-crosslinked DGEBA is
Preparation of BHHBP-grafted DGEBA resin
4,40-Bis(6-hydroxyhexyloxy)biphenyl (BHHBP) was
synthesized from 4,40-biphenol and 6-chloro-1-hexa-
656 LIN ET AL.
Journal of Applied Polymer Science DOI 10.1002/app
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UHMWPE-FIBER-REINFORCED MODIFIED EPOXY COMPOSITES665
Journal of Applied Polymer Science DOI 10.1002/app