1. PHOTOSENSITISED GRAFT COPOLYMERIZATION
OF ACRYLIC ACID ONTO CARBOXYMETHYL
STARCH
M.A. ElSheikh*, J.T. Guthrie* and A. Waly**
University of Leeds, Colour Chemistry Dept.,
Leeds, LS2 9JT, UK
**National Research Center, Textile Research
Division, Dokki, Cairo, Egypt.
*Address in UK *Address in Egypt
University of Leeds, National Research Center
Colour Chemistry Dept. Textile Research division
Leeds, LS2 9JT, UK Dokki, Cairo, Egypt
Tel. : 00441132332939 Tel. : 002023371211-4960
Fax : 00441132332947 Fax : 002023370931
Email : CCDMAE@LEEDS.AC.UK
2. 2
Contents
Introduction
Why UV
High Graft Yield
Efficient use of materials (low
homopolymer under right circumstances)
Mild Effect relative to chemical initiation
methods
Simple processing
Cost effective
Water-based options
4. 4
Preparation of Poly(acrylic acid)- CMS
Sample handling
Grafting
Carboxymethyl Starch (CMS) [prepared from
Native Starch (NS)], DS=0.2, [-COOH] = 115
mmole/100g CMS and η= 158 mPa s.
CMS was in the form COONa.
Photoinitiator (PI) dissolved in the required amount
of water.
CMS added gradually under continuous stirring
and left till completely soluble.
Acrylic Acid (AA) added gradually under
continuous stirring and left for 10 min.
5. 5
Mixture was transferred to a photochemical reactor
and subjected to UV source under gentle stirring
for known time periods.
Reaction stopped.
Homopolymer separated from the graft copolymer.
6. 6
Analysis
All samples monitored for Total Conversion percent
(TC%) of Acrylic Acid and for their Carboxyl
Content (-COOH, mmole/100g CMS)
Selected samples monitored by:
SEM
Thermal Analysis (DSC)
IR spectroscopy
7. 7
Reaction Mechanism
PI exited state
PI operated by H-abstraction from this exited state.
PI designed to bind to starch, i.e. H-abstraction
involves starch.
Radicales formation by C----H homolytic cleavage on
starch backbone.
Grafting occurs at the radical centers.
Little homopolymerization since the bulk of the PI is
on the starch polymer chain.
8. 8
Results and Discussion
Factors Affecting Total Conversion and
COOH content:
Studies
Effect of PI concentration.
Effect of Acrylic Acid concentration
Effect of Material : Liquor ratio
Effect of reaction temperature
Effect of reaction Time.
9. 9
Effect of Photoinitiator Concentration on
the Carboxyl Content of the Grafted CMS
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60 70
PI %(OWS)
5g CMS, DS=0.2, COONa= 115 (mmole/100g
CMS), η=158 (mPa s); AA, 60% (OWS); M:L
Ratio, 1:50; Room Temperature; Time, 3h.
COOHcontent(mmole/100gCMS)
10. 10
Effect of Photoinitiator Concentration on
the Total Conversion (%) of Acrylic Acid
0
20
40
60
80
100
0 10 20 30 40 50 60 70
PI %(OWS)
5g CMS, DS=0.2, COONa= 115 (mmole/100g
CMS),η=158 (mPa s); AA, 60% (OWS); M:L
Ratio, 1:50; Room Temperature; Time, 3h.
TC%
20. 20
Characterization
-COOH Content
COOH content due to grafting using
UV/photoinitiation reaches 600 mmole/100g CMS
at optimum conditions compared by 87
mmole/100g CMS using Chemical initiation (see
part II).
Homopolymer formation minimal.
24. 24
Advantages of the polymerization process
used
High viscosity of the composite achieved.
High adhesion of the composite achieved.
High Swelling in water of the dry composite or dry
graft copolymer achieved.
High graft yield, low homopolymer formed.
Mild conditions used to get high quality product.
Trials will be done to use the sun light instead of Hg
lamp as a source of UV.
Conclusion
The process can be recommended for providing
CMS-PAA graft copolymer with high graft yield.
25. 25
Applications
Sizing agents in the paper and textile
industries.
Printing thickeners for pigment
dispersions.
Adhesives.
Ion exchange materials.
26. 26
Acknowledgments
Egyptian Government for funding the research at
Leeds University.
Egyptian Government for providing funds for
attendance at the American Chemical Society
Meeting in San Francisco.
Professors in National Research Center (NRC),
Textile Research Division (TRD) and University of
Leeds, Colour Chemistry Dept. for supervision:
Prof. Dr. J.T. Guthrie (University of Leeds, Colour
Chemistry Dept.)
Prof. Dr. A. Waly (NRC, TRD)
