Note: Descriptions are shown in the official language in which they were submitted.
CA 02473319 2004-07-09
:'~i?~:':Ie:litt.'si'. (i~~!illl?lW. ilta?lc~t'iW ?~ ij~';ii~lt:c.{~:
Fi'tures: ~, ~, '~y, L-1. '~J'~-~, ~;
3' ~ . ~. ~t
r-
al~G.~U ;Gel
LlnSCann~.ble items
re;:~.ivzd v=i~u this application .
___ _..__ ____.._.__ ~F'~'IU~'~ °r~~inal documear; in File Prep.
Section on the I(3s',~i.oor~.__..._-. _..
Docuneat~ re;:u v~;=:. cede dema>?dc ae pou~ran~ ~tre balaties
(Cotnraaade: L~~ doclTm.eal~ o>-~~~ain.'u_~ dart is secric~n de pr~parauoa des
do~~izr~ a~~
IOzme ~t:~~e j
CA 02473319 2004-07-09
rNTR,OD'CJC'x)tUN'
Composites, particularly natural fiber-reii~.forced plastics have been getting
att~entia» since
1941 (Joseph et al. ~U~4). The interest fn natural fiber-reinforced polymer
composites is growing
rapidly due to their high performance in mechanical properties, significQnt
processing
advantages, excellent chemical resistance, low cast and low density. They haws
long served
many useful purpoces, but the appli:catiarz of material technology for the
utilization of natural
fibers as a reinforcement in a polymer matrix has taken place in recent years.
The use of biofibers derived from annually renewable resources, as reinforcjng
element
in therntaplastic matrix composites provides positive environmental benefts
and rtiw material
utilization. Recent reports indicate that cellulose-based natural fibers can
very well be used as
reinforcement in polymer composites, replacing (to some extent) mare
expensive: and non-
renewable synthetic fibers uch as glass due to the potential for xecyciahility
of the matterial
forms (lVtunker et al, 1 X9.8). Cellulose-based natural fiber is a~sa a
potential resource far rrtakang
low cast composite materials. These advantages place the natural fiber
composites among the
high performance composites having economic and environmental advar~cages.
A major restriction in tlae successFul use of natural fibers in durable
composite
applications is their high moisture absorption and poet dimensional stability
(swilling)
(Panigrahi et a1. 2002). Flax fibers can be incorporated in polymers to form a
biodegradable
matrix. But a high level of moisture absorption and insufficient adhesion
between untreated
fibers and the polymer matrix may lead to biacampasites having high water
absorption
characteristics that reduce their utility in many applications. Chemical
Ireatment of the fiber can
help stop the moisture absorption process, chemically modify fiber surfaces
and increase the
surface roughness in order to increase the interfacial adhesion between the
fiber and matrix,
1
CA 02473319 2004-07-09
resuttmg tn iriupraved mechanical pcrfonnance of fiber-reinforced oamgosites.
The objective of this study is to deterrnino the cffccts of pre-treated flax
fibers on the
mcchanioal properties of fiber-reinforced LLDPE, HDPE and LLDPEIHDPE
composites. This
research work should answer the question; do chemical treatments of flax
fibetv have any
influence on the composite properties?
1V.I~TERIA:~S AI~rD METHODS
IVI~teriai P"reparatian
Flax fibers were derived from linseed flax grown in Saskatchewan and
decorticated on a
standard scutehing mill at Duraf her in Canora, SK, Canada. The f bars were
first washed
thoroughly with 2% detergent water and dried in an air oven at 7t1°C
for Z~ 11. The dried fibers
were designated as untreated fbers. Then flax fibers were subjected to
sequential extraction with
1::2 mixture of ethanol and ben.~ene -for ?2 h at Sit°C; folHowed by
washing with double distilled
water and air drying to remove waxes and water soluble polymers prior to
chemical treatments.
Reagent grade chemicals are used for fiber surface rrcadifications, r~amsly,
odium hydroxide
(NaOI-~), benzoyl chloride, ethanol, dicumyl peroxide, acetone, alcohol and
the coupling agent,
triethaxy vinyl silane (Aldrich Chemical Co. Ltd;),
In this series o.f experiments, high-density polyethylene, linear low~density
polyethylene
(HI?PE x7b1.27 and LLDPE 8460.29, Exxon Mobil, Torovto, ON) and LLDPFIHDPE
25087
(NOVA Chemicals Ltd,, Calgary, AB) were used as major matrix materials for
reinforcement.
2
CA 02473319 2004-07-09
Experimental Design and Aada Analysis Methnds
The experimental dosign is a factorial arrangement of treatments conducted in
a randomized
fashion. Table 1 shows the outline of the experimental design fdr one xype of
treated fiber. The
same design was used ,for the other chemically treated fibers.
Taiile 1. Experimental design for one type of treated fiber.
Filler Plastic Test
~DPE
$enxoylation treated
fibers '
LLI Tensile Strength
JpE
( 10% perceatogc
of fiber -r
at Yield
S~Yoparceatnge oteoupling ~,r,;Y]~'~jDPE
agent)
l~Iain Treatments: 'r'~ (Silane treatment); Tz (Betuoylatian);
T3 (peroxide treatment); T~ (Untreated) = ~
Sub-treatments; S, (HDPE); S2 (LL,I~I'E); 53 (LLDPE/~DI'E) - 3
Treatments eombirtation = 4 types of fiber X ~ types ofplastiG = 12
~Tis'i~ ~1s2~ TlS3y ~~51~ T2~2~ T3~3s T3~1~ T'352, T3s3r T4~1~ ,~4~~-'2r
T4°~-3
Five samples will 6e tested for each sample, according to the appropriate
ASTIVI standard.
Tensile Test = I 2 X S replicates = 60.
Fiber Surface Treatment
Generally, the first step is the mercerization process (pre-treatment
process.) for all of
fiber surface treatments which causes changes in the crystal structure of
cellulose. Then the
different chemicals can be used ot1 the fibers surface in order to improve the
interfsae properties.
3
CA 02473319 2004-07-09
Shane treatment: Fibers v~ere pre-tread with 5% NaOI-1 for about half an hour
in order to
activate the OI~I groups of the cellulose and lignin in the fiber. Fibers were
then washed many
times in distilled water and finally dried.
The pre-treated fibers were dipped in alcohol water mixture (6~0:4a)
containing tri ethoxy
vinyl silane coupling agent. The pH of the solution was maintained between 3.5
and ~, using the
METREPATC Phydrion buffers and pH indicator strips. Fibers were washed in
double distilled
water and dried in the oven.
Henxoylatlon: An amount of pre-treated fiber were soaked in 18% Na4H solution
for half an
hour, filtered and washed with water. ~fhe treated fibers were suspended in I
O°!a l~aG~H solution
and agitated with benzoyl chloride. The mixture eras kept for i S min,
lyItertad, washed
thoroughly with water and dried between filter papers: The isolater3 fibers
were thcx~ spr~.lced in
ethanol for 1 h to remove the umrcatcd bcnzoyl chloride and finally were
washed with water and
dried.
Peroxide treatment: Fibers were coated with dicumyl peroxide from acetone
solution after
alkali pre-treatments. Saturated solution of the peroxide in acetone was used.
High terryperature is
favored for decomposition of the peroxide.
Composite Preparation
Pre-treated and untreated fibers were ground by the ~rindin~ mill (Falling
Number,
Huddinge, Sweden) and oven dried aI ~0°C for 24 h to reduce the
moisture content to less than
2°J°. Mixtures of thexrn.oplt~stic powder and 10% by weight of
flax ~bcrs were pre-dist~~ibuted by
using a food t,Iender {blaring Products Corporation, New Yorlc, N~. This is
done tv aid in
homogeneous mixing of fibers and thermoplastics during extrusion process. The
silane-coupling
4
CA 02473319 2004-07-09
agents were also be added in a proportion of ~% by weight as "resin additive".
The blend was
fed to the laboratory mixing extruder (LMT} (Dynisco, Franklin, IvIA) using a
bane! to die
temperature pra~le of 1?S°C with a screw speed of 1~0 rpm. Blends
prepared in this manner
were extruded using a strand die. Extruded strands were then pelletized. The
pellets were ground
using a grinding mill (Retsch GmbH 5657 hIAlIN, t~J'est ~rermany) attd the
ground product was
used in rotational rnoldin~. The powder of ~bc:rlthermoplastic was obtziined
by extrusion,
pelletizing and grinding of this blend.
Bincomposites Manu~'acturing lay ftotation.al Molding
Dog-bone shaped test samples were prepared using a rotational molding machine
(Parkland
Plastics in Saskatoon. SIC, Canada). It is a carousel-typo molding rnochine
with fow separate
ass that can cash rotate ax two separate axes; while completely closed in an
oven at DSO °C for
30 min.
Microstructure of Fiberreitiforced 'Composites
As a supplementary tool, the microstructure of the modified fiber-polyzrfer
rnatri.K interface
was examined using a ~ scanning electron microscope (SFN1505 FhiIips, Holland)
at the
accelerating voltage of 30 KV. The sample surfaces wet~e vacuum coated with a
thin layer of
gold on the surface of interest using a Sputter Coatex 51508 (Edwards, USA) to
provide
electrical conductivity and did not significantly affect the resolution.
Scanning electron .micragraph of fiber-rcinfotecd composites may show the
interfacial
bonding between flax Fber and polymer matrix to indicate the extent of i'~ber-
matrix adhesion.
S
CA 02473319 2004-07-09
Tensile Test
Specimens were conditioned for 7 days at 23°C and 50% relative humid;ty
prior to
performing tensile tests. Composites hrving 10% fiber by weight loading were
p~epar~ed and
properties wore evaluated by mechanical tests. The appropriate ASTM methods
wexe Followed,
and at Least five replicate specimens were tested far each property and the
results were presented
as average of tested specimens. The test conducted eat standard laboratory
atmosphere of 23 °C
and SOQ1° relative humidity.
An Instron Universal testing maehinc (SATEC Systems, Inc., Crrove City, Pty;)
was used
to perform the tensile strength test at a crosshead speed of ~ mrnlmin as
described in ASTIvI
procedure Dfi38-99 (ASTM, 1999), and each test was performed until tensile
failure occurred.
Each sample was manufactured by wc~y of rntational rnoldfng, and the familiar
dog-bone shape
was ucili~ed 1-n the testing procedure.
dig I. Tensfte test rising Inctron testing machine
6
CA 02473319 2004-07-09
'V~ater Absorption of Composites
Water absorption characteristics of composites arc altered by the addition of
additives such
as flax fiber fillers because these additives show a greater aftnity to watex.
The samples were dried in an oven at 70°C for 24 h and nrrmediately
weighed. In order to
measure the moisture absorption of composites, all samples were immersed in
water for abort 24
h xt room temperature as described in ASTM procedure D~70-~9 (ASTIvi, t 9~9).
Excess water
on the surface of the samples was re~no~ed before weighing. The moisture
absarption was
calculated according to the following:
Wet wcig~c -- Initial wei~xt
increasein weight (percent) = x 100
Initial weight
RESLY~'~''S Alvl~D Dh~GIUSS~U~1
Composite Microstructure
ribcr-matrix interface plays an important role in eampasite properties. .~
strong fiber-
matrix interface band is critical far high mechanical properties- of
corrtposites. Figure 2-5 show
the SEM photographs of fiber-matrix interae~ipn studies of uzttreated and
surface treated flax
fiber-reinforced composites. Scanning electron micrographs of the tensile
fracture of treated
composites revealed the failure mechanisms. Fiber breakage was the main
failure criteria
observed. Untreated flax composite indicated that theca was very pour adhesion
between fiber
and matrix. While chemically treated flax composites showed better fiber-
matrix interaction as
observed from the gflod dispersion of fibers in the matrix system, thereby
predicting micropores
at the interface.
7
CA 02473319 2004-07-09
Fig 2. SEfvI rrzicrogragh of LLDPE with 10% Fig 3. SEM micrograph of L~,D~"E
with
untrcatcd flax in eompos9ces 1U% Shane treated flax in com~asites
Fig 4. SEM tnicrograph of LLDPE ~i#h x0% Fig 5. SEM microgranh of LLDP)~ writh
Bettxoylation treated flax in composites I0% Prcrxide treated flax in
composites
Tensile Test
Tensile testing was performed with varying methods of Chemical treatment iaa
order to
develop a sense of horv the chemical treatments of flax fiber affected the
tensile strength. Figure
6 describes the tensile strength at yield of fiber-reinforced Lr:I7PE, HD~'E
and LLl3PElHDPE
composites. Compared to the untreated fiber-based composite having IO% by
weight fiber
loading, tensile strength at yield was improved by these treatments. This is
probably ~tue to the
8
CA 02473319 2004-07-09
increased fiber-matrix adhesion. The variation in tensile properties could be
expE~ined on the
basis of the changes in chemical interactions at fiber-matrix interface on
various treetrnents. The
tensile stren~h of flax fiber-reinforced composites is determined both by the
tensile strength of
the fiber attd by the presence of weak lateral fiber bonds (Mohanty et al.
20fl.1). The variations in
the tensile strength at yield of the composites on different modifie$tion were
attributed to the
changes in tha chemical structure and bondahility of tho fiber. Also tho
tensile properties of
natural fber-reinforced plastic corn~osites could be improved by the use of
silazie cot~plin~
agent.
_ ~-~ ~~ h~
"rt ~ ~ N G O n1
~! [~.. ~ M 01 h M ,.., h~ 00
D0. ~..' O~..C ~ r h ~'
~i3 .-. ~p va ,,ti ~p aD r'
b
rr
Q?
-1a
b
w
A
D untreated ~ s~azte treatment Cl Benroyl~,tivn Cl Peroxide txeatmerlt
Ftg G. Comparison of tensile stt~ength ~t yield of 10% fiber with different
t.hermoptast'ies.
9
LLD.PE HDPE LLI7PEIHD~'E
CA 02473319 2004-07-09
Water Absarptian of Compasrtcs
During chemical treatment of the flax fibar, the hcrrlicellulase and lignin
were separated
and cellulose was used for the biocomposite. Figure 7 shows the moisture
absorption of
composites at the room temperature. The moisture absorption of the chemically
treated flax
fiber-based composites was lower than that of the untreated fiber-based
composites. S~trnng
intermolecular fiber-matrix bonding decreases the rate of moisture absorption
in biocornpositc. h
shaves that chemical treatments of flax fiber can decrease the water
absorption of the
biocomposites.
0.2 ~,
N
0.15 ~ ~ _, ~ ,~ °
m ~cJ' o~..e O_ M _ ~ ~ ; O
G ga~~°° '~.ooQ° 'd'O
W oo ; y sn ~ ~ ~ r, . a
a
o. x °:~. ~ ~ °. ,af
h~~~ .0 p R~ ~ Y ~ t
I ,
~J i
a.os ~ ~ ;,~~~ : 2~z
k~b~ ,~~Gi
h ~':
-~H x. 4 ,;.
~~LDPE HaPE LLDP~JHDPE
17 untreated ~ silane treatment ~ Benza~~tic~n 0 Peroxicd~ treat~x~ent
Fig 7. Moistarc absorption of cosupositcs.
CA 02473319 2004-07-09
CONCJL~JSiCfNS
Fiber-matrix interface plays an important role in composite properties. The
ability to
control the chemical arid mechanical properties of the fiber-matrix interface
is crucial.
Morphological studies showed that the chemical treatments improved the fber-
m~tr'sx adhesion
and the dispersion of the particles.
Compared zo the untreated fiber-based composite; tensile properties rwere
improved with
a suitable fiber surface treatment. Silane; Benzoylation, and peroxide treated
fiber-based
composites offered superior physical and mechanical properties. lVfechartical
properties of
natural fiber-reinforced plastic composites could be improved by the uce of
silane eouplin~
agent.
The hydrophilic nature of biofibers leads to biocomposites having high water
absorption
characteristics that can be overcome by treating these fibers with suitable
chemicals to decrease
the hydroxyl groups of the fibers. The water absorp~tior~ and swelling of the
treated flt,~ fiber
composites is lower than that of composites based on untreated flax fibers.
In the present study, chemically treated flax fiber is used as a supplement to
plasiics, and
reinforcement in thernioplastic matrix in rotational molding process. The flax
fiber is already
being produced and can be obtained a relatively low cost compared to glass
fiber reinforcements. .
Thus, natural flber~reinforced bit~degradable matrix composites
(biocornposites} will get morc
attention in the future.
lI
CA 02473319 2004-07-09
The authors would like to ackna~wledge the Department of Civil Engineering and
biology at
the University of Saskatchewan for the use of their facilities arid equipment.
Financial support of
this study was given by Saskatchewan Flax Development Commission and the
Agriculture
bevelopment 1~und of Saskatchewan Agriculture, Food and Rural Rcvitali2ation.
The support of
Parkland Plastics and the University of Saskatchewan is also acknowledged.
11~F~~tENCES
ASTM standard B 256-97, 1997. Sca~ard Test Methods. for l~eterminittg the Izad
Peztdulum
Impact Resistance of Plastics. 1997 Annual $ook of ASfiM Standards, Textiles.
7(1 ): l-20
ASTNI standard D 63~-99, 1999. Standard Test l~fethad for Tensile properties
of Plastics. T~99
Annual Book of ASTM Standards, ~"eattiles. 7(1):46-S8
Joseph; K., L:I~.C. Mattoso, R..1:). Toledo, S.Thomas,.L.li_ de.Carvalho,
L.flthen, S. Kala and B.
Tames. 200. Natural fiber rei»fareerl therrnoplasfic Composites. Natural
Polymors and
Agrofibers Composites 159:01
lvIohanty; A.I~., M. Ir~iisra and 1,.T. Drzal. 2001. Surface rnodftcation of
natural fibers arid
performance of the rssul'rig liiocoxnposites: An Qvetview. Composite
~";nter~'ac~ex 8 (5): 313-343.
lvluttker, M., R Holtrnann and lxf. Michaeli. I99:S:, Improvement of the
fiberlmatrix:-adhesion of
natural fiber reinforced polymers. Proceeding of she d3r~ Inror»crrianal'
SAtYI~.h' s~mpc~sium, Iviay
31-yune 4.
fanigrahi, S., L.G. Tabil, W:f. Crerar .and S.Sokansanj. X002. Application of
Saskatchewan
grown flax fiber in rotational molding of polymer composites: Paper N~o. CS~E
02-302.
Saskatoon, SK: Canadian Society of agricultural Engineering.
12
CA 02473319 2004-07-09
IN'FRQD~CTIOiV
Flax fibers ire abundantly available in Canada, well known far their low cost
and high
strength characteristics. The interest in using natural flax fibers as
reinforcement in
hiacomposites has increased dramaticaliy and also represents one ofthe most
important uses: Hut
cellulasic fibers are hygrosCapic in nature; tnaisture absorption can result
in swelling of ihc
fibers which rnay lead to micro-~crackiag crf the composite and degradation of
mechanical
properties. This problem can be overcome by treating these Fbers with suitable
c~emicats to
decrease the hydroxyl groups which tray be involved in the hydrogen banding
within the
cellulose molecules. Chemical treatments may activate these groups or can
introduce new
moieties that can effectively interlock with the matrix. A number of fiber
surface treatments Iihe
silana treatment, benr_oylation and pero~idc treatment were carried out which
may result in
innproved mechanical performance of the f fiber and cornpasite. By Irmiting
the substitution
reaction on the surface of the fibers, good mechanical properties were
obtained and e~ degree of
biodegradability was maintained (Scandola et al. 2000). Research on a cast
effective
modification of natural fibers is a necessity since the main attraction for
today's ~ market of
biacomposites is the competitive cost of biofibers.
The possibility of fortlting mechanical and chemical bonding at the fiber
surface is mainly
dependent on the surface morphology and chemical composition of the f begs
(Edwards et al.
200I). Therefore, the microscopic analysis of fiber surface topology arid
morphology is of
utmost importance in fibrous composites. The structural and chemical changes
that have
occurred on the surfaces of flax fibers upon treatment were characterized by
scanning electron
raicroscopy (BEM).
rlax fibers are incorporated in thermoplastic materials to form a
biodegradable matrix in
»,~"~p~"_~~,wu..N._.~w..~_..__ __ _.._..__ _._.
_____~.m,~..,~~~~,.~~"~.:~,,",.;,-.~.~.~,~..~~~~_.___.~____.u.
_;.
CA 02473319 2004-07-09
order to impart desired characteristics such as increased strength into the
composite. Mechanical
performance of a fiber..reanforced composite is mainly determined by the
properties pf fiber. 1t is
very important to know the strength of the fibers before being combined into
the thermoplastic
matri-x to better understand how the anal composite product behaves,
While much effort has been denoted to studding the mechanical behavior of the
materials,
a comparable understanding of the thermal behavior is lacking: 'I'o determine
the rnoictng point of
treated flax fibers, a di~'erentia.l scanning calorimeter (13SC) is the most
widely used of al!
therrno-analytical techniques and ideal for research and quality control
applications.
The present study investigvtes the different modification methods of flax
fib8~rs and their
effect on the mechanical performance and thermal behayiar of the fiber. The
specific e~bjective of
this work is to apply the SEM to analyze the surface morphology of flax fibers
upon trcatrr~cnt;
to apply the temperature variation ~ncthod tv obtain the melting temperature
of treated ~Iax
fibers; to use the Instron 1 Oll testing machine to measure the fiber bundle
tensile stxep~th and to
use the environmental test chamber to compare the moisture absorption of
treated and untreated
fibers.
___ _.._____.._____ .... _ .. w..d...~,~"vr~~... __.____...__~. .......:....
.. ~~...._.~,____.__ _~_...~...._.. _ _.
CA 02473319 2004-07-09
MA'Tl~~t.IALS AID METHf,~DS
Material Preparation
Flax fibers were derived from linseed flax gown in Saskatchewan and
decaxt~cated an a
standard seutching mill at Durafibre in Canora, Saskatchewan, Canada. The
fibers, were First
washed thoroughly with 2% detergent water and dried in an air oven ax
?0°C for 2~ h. The dried
fibers were designated as untreated fibers. Then flax fibers were $ub,~ected
to sequential
extraction with 1:2 mixture of ethanol and benzene for 72 h at 5~°C,
followed by washing with
double distilled water and air drying to remove waxes and water soluble
polymevs prior to
chemical treatments. Reagent ~rat3e chemicals were used for Iiber surfacE
madificatiorts> namely,
sodium hydroxide (NaOH), benzoyl chloride, ethanol, di.cumyl peroxide,
acetone, arid alcohol.
The structure of silane coupling agents, triethoxy vinyl silane (Aldrich
Chemical Co. Ltd.) is
shown in Figure 1,
ft,~,~0 ~~zh's
Si
Cf~'a
HfCsO
~'ig.1. Structure of silane entapling agents (Tri ethoxy vinyl silane)»
Finer Suri'acc'~'Sreatment
Generally, the first step is the mercerization pracess {pre-treated process)
for all of the fiher
surface treatments. Mercerization causes the changes in the crystal structure
of cellulose and then
the different chemicals can be used on the fibers surface in order to improve
the interfacial
properties,
CA 02473319 2004-07-09
SiIar~e treatment: Fibers were pre-treated with 5°fo NaOH for about
half an hour in order to
activate tho DH groups of the cellulose and lignin in the fiber. Fibers were
then wa:~hed many
times in distilled water and finaliy dried.
The pre-treated fibers were Clipped in alcohol water mixture (60:40)
containing tri ethoxy
vinyl silane coupling agent. The p~ of the solution was maintained between 3.5
and ~1, using the
aVIETREPAK Phydrion buffers and pH indicator strips. Fibers were washed ixs
dou~~lc distilled
water and dried in the oven.
t'llkoxy silanes are able to form bonds with hydroxyl groups. Silanes urtdergb
hydrolysis;
condensation and the bond formation stage. Silanols can form polysiloxane
structures by reaction
with hydroxyl group of the fibers (Sreekala et al. 2000). The possible
reactions are shown in
Figures 2 and 3. In presence of moisture, hydrolysable all:oxy group le~.ds to
the formation of
silanals.
~ c~~$
Chip=CSI-Si-(~C2H5 ~Z-~-->Cki2=C1:-i-S-~0-hI
OCxHs O-H
Fig. 2. Hydrolysis of silatte (Sreekala et al. 2000).
CA 02473319 2004-07-09
O-H
Cel lulose -- _ _ _ ..p,~
Fibcrs_ _' _ _ _ He~cellulose -O~ H + C~-IZ=CH- ~i-O-,~I ---~'-
-~~ Lignin--_____ _p,,~Lr
H O-H
0-H
Cellulose------4--~ ~i-Ci-I=CHz
,
o_l~
.,. O_H
Tiber-----Hcmicellulose -O- Si-CH~CHZ
', O-H
0-H
Lignin-_____ .. p-... ~i_CH==CH,
0-H
~'ig. 3. Hypothetical reacti4n of fibers and silane (Srcekata et al. 2440).
I~enzoyl~tion: An amount of pre-treated fiber were soaked in 1E°/Q
NaOT~ solution for half an
hour; fltered and washed with watc~-. Tho treated fibers were suspended in
10°/n IVaOH solution
snd agltatcd with ber~zoyI chloride. The mixture was kept for 15 min,
filtered, washed
tharou~hly with water and dried between otter papers. The isolated fibers were
then soaked in
ethanol for 1 h to remove the untreated benzoyl chloride and finally were
washed with water and
dried.
The reaction between the cetlulosic -OI-I group of fiber and benzoyl chloride
is shown in
Figure 4.
CA 02473319 2004-07-09
Fibre - OH -r NaOH -----~" Fibre - O'Na~ -~- H2O
O
Fibre- O'1~'a'~ + C1C ~ / ---=- Fibre- O - C ~ ~ +hJaCl
Fig 4. A possible reaction between eelludnsic-UH groups and bcnzoyl ehxorfde
(Joseph et al. 2000).
Peroxide treatment: Fibers were coated with dieumyl peroxide from acetone
solution after
alkali pre-treatments. Saturated solution of the peroxide in acetone was used.
High temperature is
favored for derompositiort of the peroxade.
The decomposition of the peroxide and the subsequent reaction at the interface
is
expected at the time of curing of composites. This is shown in Fa~ure 5.
RO - OR ~ 2R0.
RO. + Cellulose - H ---~ R ° OH + Gellulase.
Fig S. Peroxide treatment rea~efion (~ree~ala et al. 2000j.
DSC ~xpet~irnenta~ Procedure
DSC is a thermoanalytical technique in which heat flow is measured as a
Function of
temperature or tune. DSC is useful in charaeterizin~ thermal properties of raw
materials,
mixtures of materials or finished products and also provides information
quickly and easily on a
minimum amount of sample.
One treated fiber sample of 7 to 10 mg was placed in an aluminum sample pan
and sealed
with the crucible SCalil7$ ~7TCS5; thl5 WiIS placed lnLO Itle DSc ~~I~ (TA
Instr'uTr~L'ntS, InC.
Newcastle; DE}. '.Che sample was heated at a controlled rate (5°Clrnin)
from room temperature to .
X00°C and a plat of heat flow versus temperature was produced. The
resulting therma~rarn was
CA 02473319 2004-07-09
then analyzed. For each sample at least three experiments were performed and
the results
averaged the melting point evaluated.
Fiber Surface lWlorphology
As a supplementary tool, the microscopic examination of modified and untreated
fibers'
surfaces were carried out by using the scanning electron microscope (SEM505
Philip, Holland)
at an accelerating voltage of IU I~~': The sample surfaces were vacuum coated
with ~ thin layer
of gold on the surface using a sputter caster SI~aB (Edwaxds, USA} to provide
electrical
conductivity arid did not significantly affect the resolution.
Fiber Bundle Tensile Teat
Flax fiber bundle tensile strength tests were preforrned by using a
computerwcontrolled
Instron Model 1011 (Instron Corporation, Cantr~n, 1VIA} with a gauge length of
40 mm and a
crosshead speed of 5 mmlmin (Figure 6). For every set of chemical treatment, a
minimum of
fifty specimens were tested for determining the fiber tensile strength. The
tests were cc~nduoted at
standard laboratory atmosphere of 23°C and 51 % relative hurr~idity,
The Tnstron was set up to display a force displacement-loading curve and to
read the load
at maximum or the break point. Looking at the shape of this curve is a method
to check the
accuracy o~ each individual test. yf the sample was tensioned unevenly, more
than one peak will
be seen on the graph. If the fiber have slipped between the clamp and the grip
fixture, then no
distinct break point will be seen on the graph and the test has been
compromised ('Ward et al.
2002).
CA 02473319 2004-07-09
Fig. b ~'ibcr bundle teasile strength test.
Unit Break.is calculated bar the following equation:
UB=FID........ ............,....................................... ..(l)
where. F= maximum breaking load {mN)
D= linear density or tax (mgjrn)
t113= unit break (mN'/tex)
The average unit beak of flax fiber bundle was estimated by use of this fiber
bundle
tensile test. Such as assuming the breaking point is located at the same spot.
This testing
procedure uses linear density to in effect measure the aroa.
Moisture Absorption
friar to testing, the fibers were dried in an oven at 70°G for 2~ h.
fiach sample gas planed
CA 02473319 2004-07-09
in a conditioning device for ~Z lt. Conditioning was conducted in the
extviroxunental test ahambcr
(Anglelantoni, ACS, IVIassa Niartar~a, Italy) at 23°C and relative
humidity values af' 33, 66 and
100%, respectively The weight of fibers was measured at dif~'erent time
intervals and the
moisture absorption was calculated by the weight difFerence.
After weighing an ara analytical- balance, the moisture absorption was
calculated
according to equation 2.
Increase in weight (percent) = M' r ~' x 100 ....... ... . .. .... . ... . ..
. .. .. . . . . . .. . .. .. (2)
Md
whew= Mr-- mass of tl~e sample after conditioning (g) (wet weight)
M'o= mass of the sample before conditioning (g).(dry weight
1 __
CA 02473319 2004-07-09
~x~su»TS alvn n~scussxr~N
physical Modifieatioas:1~'ibers Surface lVlorphoiogy .
Scanning electron miexoscopic analysis examined the surface topology of
un#reated and
treated fibers. It is important to mention that the changes of surface
topo;~raphy affect the
interfacial adhesion. Aporaus structure is observed for untreated fibers.
There is saong evidence ~chac phy$ica3 microstructure changes occurred at the
fiber surface.
It can be clearly observed that silane treatment gave surface coating to the
fibers; drtd surface
features of f begs wexe not clearly visible. Since the flax fibers exhibited
micropores on its
surface, the coupling agent penetrated iota the pores and formed a
rnechanicall~r interlocked
coating on its surface. Benzoylatiarl treatment led to major changes on the
fiber surface. Smooth
fiber surface is seen due to the mass like substances deposited on the
'surface of the fiber. The
surface topography is entirely modified after dicumyt peroxide treatment. The
fibrall~r structure
of the individual ultimate fibers is revealed from the photograph and may be
duE to tho leaching
out of waxes and pectic substances. Ivlicropores; particles adhering to the
surface; groove like
portions and protruding structures made the fiber surface very rough.
CA 02473319 2004-07-09
Thermal.A:nalysis: lVlelti~g Point
The rncteriaIs tested were assumed to be thexmaliy hamageneous. The heat flaw
shawed
the rise of temperature as fttnctian ref time. Analysis of the DSC thermogram
showed that the
melting range of the flax i'ibers is displayed as an endothermic peak. The
primary disadvantal;e is
fiber's low melting point. Comparing the melting paint of untr~cated and
treated flax. ~tbers, it is
easy to observe that the latter had higher melting point as shown in Figure 8,
Atl increased
melting point mar lead to improved thermal properties of flax fiber-reinforced
composites.
- ~ ~ ~ ~ r ,.t-.,.: .,.",.m.,. ... .d .. ....t 's:
~.: .
.1
..,. ~., ~..
y
.. .
anas~tsd . ' iilepe ireas~nont ' ~ ~~uaa'~io~ tresime~ ' neto~dd~ crasanares .
Ftg. 8. Melting Point of uatrcated and treated flax fibers.
Fiber $undtc Tensile Strength Test
Fiber bundle strength was tested and the results are shown in Figure 9 with a
gauge
length of 40rnm at standard laboratory atmosphere of 23°C and 51 %,
relative humidity. Data
CA 02473319 2004-07-09
shown are averages based on fifty tests. The data show chat the higher
strength of silanc and
peroxide treated fibers rnay he a result of the removal of surface
imperfections after the
treatment. The increased uniformity of the fibers would Sive an increase to
strength; its points of
unconformity are rernowed during the treatment and this changes the
deformation behavior of~tlle
fibers. On the other hand, benzoylatinn could not give a high unit break of
flax fiber trundle due
to the brealca~e of the bond structure.
,m\~.~:. ~ .t mar;sY _ ,.:.ls. ..~'t~fk~:;~ t .l ,- I <t .. . ' ~~' ::r
Y~fr~~. ..
::i.,,
~'~.f
' .' .., rvLy : .. ...,..
' S . .:L.:.
!Y+ ,. ....
.~
~ri~m r~ fir- ~5 ~'~ r ~.r. ,y~ x ' ~.a ~ rr ~ r!~ ,
j.~~ ~n~f ..~:,;' ', ti,a~..r~lit~ t 1 tt ~.tx;h 3.y., ~~'~~~~~~. J ~~r ~~'
ar;.
~itrtt~'iS~ ~if ~.r:: 4, Sx f1~3~.~1~'a~.rr,.~Kn"i\Vr ,.. S.. ~f!~~ 4V1 .Y. ~'
b~....i - vY. r "~
t f ~ v.: J t ..' '.
> rt: t ' ; i ' '
Jt j f ,22,1:0T,
~~ ~y ~ ~ ' ' ~ .
< < t..
~f~~ a.~ a ~ 3a . - ~
x' . ~ ~T~ . ~ ,. ''~
.. ~ ,.. .
;a ~
..
,~ °* ~ .
~..w.f. .-~.~a_~.,. ~.., ~ .,'J,N..w . ,,:-,. ~. r ~ c~tl~w~iller(tni'~lsos? .
~< . .
. ~i~ated~..: :#~,~~ra#t~t~c, . ' kae~rci~otiaaxraa~ussnc~.v-
:.poru~Idraeoiniano'.. -.... . :x . .
.. .,. :. .... ; :,.. ; w ~ ~. y ,°
Fig. 9 Average ~~it break of flax fiber bundle;
lVroisture Absorption
During chemical treatment of l~he nax fiber; the htxrliccllutase and lignin
lucre separated
and cellutose was used for the biocornposate. Before making the composite, the
moisture
absorption of flax fibers should be reduced. JFigure 10 shows the moisture
absarption of
CA 02473319 2004-07-09
untreated and treated flax fibers at different relative I~umidity: The
rnoisturc absorption of the
chcrnically treated flax fiber is lower than that of untreated fla ~c fihers.
It shows thist chemical
treatments can decrease the moisture ~bsorptxon of the fibers and we hope it
may also lead to the
biocornposites having low moisture absorption characteristics.
r:
G
d ~ ~ ;,
Q ~ ~ ~y ~~ ~ ~i
rn '
.O ~ ~ :. '.
c? o0
O ~,
.3 - r
'~7 t
~.t v ~ ~ i
SV ~L,,t y.!~Y~ P'~~i,
. . 'r ~ ~'.'.' k t.°~ I
p Untreated ~ Shane ~r~atment p ~enzoy~tinn p Peroxide treatment
Fig.10 Moisture absorption of untreated at~d treatedf flax fibers.
~3 66 1~0
CA 02473319 2004-07-09
Morphological and structural changes of the fibers were investigated by using
scanning
electron microscopy. The coupling agents were found to be effective to improve
the surface
properties of flax fiber and form a mechanically interlocked coating axi its
surface. 'fherefi~re,
physical microstructure changes occurred to the fiber surface by chemical
treatment.
A validation of the method was made on the samples witI~ dii~'erentiat
scanning;
calorimetry (DSC). The results obtained in this work show that the treated
flax filers have
higher melting point than the untreated one.
Silane and peroxide treatment on flax fiber bundle Iead to a higher tensile
strength
than that of the untreated fiber bundle. Comparatively lower tensile strength
is observed in
benxoylation treated fibers.
Ftax fiber is highly hydrophilic due to the presence of hydroxyl groups from
~celluiase
and lignin. Chemical treatment can reduce the hydrophi.lieity of the fiber by
treating these
fibers with suitable chemicals td decrease the hydroxyl groups iry the ixbers.
From the results of these experiments, it is quite evident that flax fiber has
a very
promising future and aan be used ,as a substituzc for glass fibers. Surface
modifications of
hydrophilic natural fibers have achieved some degree of success in rraaking a
superior
interface, mechanical properties and thermal properties, but lower cost
surface modif cation~
needs to be emphasized for biocomposites to replace glass fiber corr~posites
in many
applicatiorts in the future. ?~latural fiber-reinforced composites should be
developed and
characterised so as to produce cost~competifive biaeomposites for industrial
applications.
ACKNOWIr~AGIVX~NTS
The authors would like to acknowledge the Department of Biology at the
University of
Saskatchewan for the use of its facilities and equipment. Financial support of
this study was
CA 02473319 2004-07-09
Fund of Saskatchewan. Agriculture, Food end Rural Revitalization.
,~2ElF'ERENr~ES
Edwards, H.G.M., D.VtI. Farwell and l~. Webster. 1997. AFT Roman microseop~ of
untreated
natural plant fibers. .S~ectrnclrimic~a Actu, Pare A: Molecular and
h'iomoleculur Spectrvscapy
S3A (13): 2383-2392.
Joseph; lC., L.H.C. lvtattosa, R.T~. Toledo; S:Thomas, L:I-I. de Carvalho,
L.Plthen, S. Kola and
B. .lames. 2000.1'~latW al fiber re~nf~reed thermoplastic Composites. Natural
Polymers and
Agro~hers Composites. 159:201
Scandala, M.., G Frisoni, M. Baiar~o. 2000. Chemically modified cellulosic
reinfoFCements.
2a9thACSNcttional Meeting, San F'raneisco, CA, lvlareh 26-30.
Sreekala, M.S., Ivf.('~. Kumaran, S. Joseph and M. ,Tacob. 200Q. C7il palm
fibers reinft~reed
phenol formaldehyde composites: I~tluence of fibers surface modifications on
the mechanical
performance. Applied composite materials ?:295-329.
Ward, 3.. L.fs.Ta'bii, $. Panigeahi, 't~J'.J.Crerar, T. Powell, A.:T.Kovaes,
Alvin Ulrich, 2402.
Tensile testing of flax fibers: Presented' at the ~Sl9ElCSAE ~lTorth Central
Inner-sectiuncal
Conference, Saskatoon, SK; Se~ptam6er 27-2$, 2002.
CA 02473319 2004-07-09
1 All publications mentioned inthis specification are indicative of the level
of skin in the
2 art of this invention. Alt publications are herein incorporated by reference
to the same s xtent as
3 if each publication was specifically and individually indicated to be
incorporated by refer ence.
4 The terms and expressions used are, unless otherwise defined herein, used as
terms of d.acription
and not limitation. There is no intention, in using such terms and
expressions, of excluii ing
6 eduivalents of the features illustrated and described.
