P1250095226ixXHZ

1
Silane Treatment Effects on Glass/Resin
Interfacial Shear Strengths Subir Debnath1,
Stephanie L. Wunder1, John I. McCool2, George R.
Baran3 1Department of Chemistry, Temple
University, Philadelphia, PA 2Department of
Industrial Engineering, Penn State Great Valley,
Malvern, PA 3College of Engineering, Temple
University, Philadelphia, PA

Preparation Testing of Microbond Shear Strength
Samples - Place fine resin (60/40
BisGMA/TEGDMA) beads of about 0.1 to 0.4 mm
embedded length on the fibers. - Cure the beads
for 4 min in a light curing oven, let sit
overnight. - Attach one end of fiber to a
cardboard tab inserted in the top grip of a
tensile testing machine. - A special bottom grip
(figure below), consisting of two glass slides
that could be moved horizontally, was used. The
top grip was used to position the bead just
below the slides, which were closed until they
just touched the outer surface of the fiber.
- The load was measured at a crosshead speed of
1 mm/min. - The peak debonding load (F) from the
load-displacement curve was recorded and used to
calculate the interfacial shear strength (?) from
the following equation ? (F/?dl),
where d is the fiber diameter and l is the
embedded length of the resin bead.

Results
Abstract   Silane coupling agents are used to
improve adhesion between a polymer matrix and the
filler. Objective to measure interfacial shear
strengths of glass fiber/resin interfaces
following seven glass surface treatments.
Methods glass fibers approximately 30 mm in
diameter and 8 cm long were silanated using
various concentrations (1, 5 and 10) of either
3-methacryloxypropyl-trimethoxysilane (MPS) or
glycidoxypropyltrimethoxysilane (GPS) in acetone
(99.8). Rubber (poly(butadiene/acrylonitrile),
amine terminated, MW 5,500) was also attached
to the fiber surface via GPS molecules to observe
the effect of an elastomeric interface on shear
bond strength. A bead of resin (60/40
BisGMA/TEGDMA) approximately 0.2 to 0.4 mm in
length was cured onto the treated fibers.
Approximately half of the specimens were soaked
in 5050 ethanolwater for one month. Sample
sizes ranged from 13 to 20. The load required to
dislodge the resin bead was converted to shear
bond strength. Results interfacial shear
strengths ranged from 12 MPa for untreated fibers
to 20 MPa for fibers treated with 5 MPS.
Tukeys multiple comparison test showed that the
5 MPS treatment yielded a significantly higher
fiber-resin shear strength than all others. After
soaking, the shear strengths of all except
untreated interfaces were lowered. Conclusions
silanated interfaces are more susceptible to the
deleterious effect of soaking than non-silanated
interfaces. This work was supported by USPHS DE
09530.
Conclusions   -   For unsoaked fibers,
interfacial strength is poorest, and similar for
the as is fibers, 5 GPS and control rubber
treated fibers as in these cases, at least one of
the surfaces has no covalent linkage, either to
silica (control rubber) or the matrix (as is
and 5 GPS). -   5 MPS treated samples exhibited
highest interfacial strength. -  A rubbery
interface had only minimal effect on the
interfacial strength. - Soaking decreases the
interfacial shear strength for all the samples,
with 10 MPS showing the largest drop before and
after soaking.   Future Work   - Correlation of
interfacial strength values with elastic modulus
and fracture toughness for composite samples
prepared using same filler surface treatments.
- Average shear bond strengths of treated glass
fibers before and after soaking.
Introduction   Inorganic fillers in dental
composites are typically coated with silanes in
order to improve the bond to the resin matrix and
increase the service life of the composite1 an
attendant benefit is the improved dispersability
of silanated fillers in matrix monomers2. The
resulting materials possess superior mechanical
properties and wear resistance, and increased
resistance to water sorption3 when compared with
composites containing non-silanated fillers. In
general, the stronger the filler-resin interface,
the greater the improvement in static4, impact5,
and fatigue properties6. Numerous methods have
been developed for evaluating the quality of the
filler-resin interface, and these have been
recently reviewed7. The microbond test was
developed for fibers with small diameters, and
relies on the ability to displace a small resin
droplet that has been cured around a
fiber8.   The effectiveness of silanation
protocols has been indirectly assessed, usually
by subjecting composites to soaking or boiling
water treatments, then measuring the strength of
the composite9,10. The implied assumption has
been that weaker, or more readily degraded
interfaces, will result in lower composite
strengths. In this study, we employ the
microbond test to evaluate the shear strength of
the interface between glass fibers and a
BISGMA/TEGDMA matrix following fiber surface
treatment by various silanating protocols, both
before and after soaking in 5050 (v/v)
methanol-water mixture.


Reaction Scheme Silane Treatment
Measure load at crosshead speed of 1 mm/min

Failed Interface
Si
OH
OMe
Si
OH
O

Movable glass slides
Si
Si
Si
OH
MeO
Fiber
O
Si
O
O
OMe
Silane coated Fiber
Glass Fiber Surface
MPS
References   1. Chen, T.M. and G.M. Brauer,
Solvent Effects on Bonding Organo-Silane to
Silica Surfaces. Journal of Dental Research,
1982. 61 p. 1439-1443. 2. Mohsen, N.M. and R.G.
Craig, Effect of Silanation of Fillers on their
Dispersability by Monomer Systems. Journal of
Oral Rehabilitation, 1995. 22 p. 183-189. 3.
Wang, J.-W. and H. Ploehn, Dynamic Mechanical
Analysis of the Effect of Water on Glass
Bead-Epoxy Composites. Journal of Applied Polymer
Science, 1996. 59 p. 345-357. 4. Zhao, F. and N.
Takeda, Effect of Interfacial Adhesion and
Statistical Fiber Strength on Tensile Strength of
Uniderctional Glass Fiber/Epoxy Composites.
Part I Experimental Results. Composites Part
A, 2000. 31 p. 1203-1214. 5. Kessler, A. and A.
Bleddzki, Correlation Between Interphase-Relevant
Tests and the Impact-Damage Resistance of
Glass/Epoxy Laminates with Different Fibre
Surface Treatments. Composites Science and
Technology, 2000. 60 p. 125-130. 6. Keusch, S.,
H. Queck, and K. Gillespie, Influence of Glass
Fibre/Epoxy Resin Interface on Static Mechanical
Properties of Unidirectional Composites and on
Fatigue Performance of Cross Ply Composites.
Composites Part A, 1998. 29 p. 701-705. 7.
Pitkethly, M., A Round-Robin Programme on
Interfacial Test Methods. Composite Science and
Technology, 1993. 48 p. 205-214. 8. Miller, B.,
P. Muri, and L. Rebenfield, A Microbond Method
for Determination of the Shear Strength of a
Fiber/Resin Interface. Composites Science and
Technology, 1987. 28 p. 17-32. 9. Craig, R. and
E. Dootz, Effect of Mixed Silanes on the
Hydrolytic Stability of Composites. Journal of
Oral Rehabilitation, 1996. 23 p. 751-756. 10.
Mohsen, N. and R. Craig, Hydrolytic Stability of
Silanated Zirconia-Silica-Urethane Dimethacrylate
Composites. Journal of Oral Rehabilitation, 1995.
22 p. 213-220.  
Resin bead
Rubber Treatment
Interfacial area
OMe
Si
OH

NH2
Peak debonding load (F)
O
Si
MeO
NH2
O
Si
OH
OMe
Rubber Poly(butadiene/acrylonit-rile), amine
terminated ( MW 5,500 )
GPS
Glass Fiber Surface
H2N
NH
HO
O
Si
O
SiO2
- Raman spectra of A380 fumed silica silanated
with GPS (?), the rubber attached via method II
(?), and the neat GPS (?) and rubber (?). Bands
characteristic of the GPS, in particular the CH
stretching and bending vibrations are observed on
the silanated beads. In addition, the double bond
and cyano groups from the rubber, at 1660 cm-1
and 2225 cm-1, respectively, are also observed on
the rubber coated beads.

Materials and methods Various Fiber Treatments
Methods - Glass fibers were treated by various
methods to vary the nature of the fiber/resin
interface. Fibers were coated with various
concentrations (1, 5 and 10) of MPS (for which
there exists coupling between the silane and
matrix) or GPS (for which there is chemical
attachment to the silane but none to the
matrix). - Rubber treatment of fibers included
coating the fibers nonspecifically with rubber
(for which there is no chemical attachments to
the fiber), and coating fibers with silane and
rubber (for which there is chemical attachment to
the silica). - The load required to dislodge the
bead from the treated fiber was converted to
shear bond strength. - Samples soaked in 5050
(v/v) mixtures of ethanol and distilled water at
37 0C for a period of one month were also tested.
Rubber Treatment of Fibers
Acknowledgements   This investigation was
supported by Research Grant DE09530 from the
National Institute for Dental and Craniofacial
Research, Bethesda, Maryland, USA.   All the
materials used for making the dental resins were
kindly donated by ESSTECH, Essington, Pa.
Silane Treat-ment of Fibers
Method I
Method II
Control




Silanate
fibers

Silanate
fibers

Stir fibers and
React GPS
with 1
GPS in
, 5,10
Rubber for 2
with 1

with Rubber
EtOH

days in CHCl3
GPS in

MPS/
in CHCl3

Acetone

Centrifuge, evacuate
and heat cure at 110oC
Centrifuge, evacuate
Evacuate
for 2 hrs

React with
and heat cure at 110 oC
after
Fibers

for 2 hrs

washings

React with
rubber in
CHCl3
Evacuate
Evacuate
after
after
washings

washings

Evacuate
after
washings