This document discusses the development of biodegradable plastics from renewable resources as alternatives to conventional petroleum-based plastics. It describes the synthesis of elastomers from corn starch and polydimethylsiloxane (PDMS) which results in robust, biodegradable materials with an even dispersion of starch throughout the hydrophobic PDMS matrix. The document also examines blends of poly(lactic acid) (PLA), poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), and poly(butylene succinate) (PBS) which achieve a balance of thermal and mechanical properties, as well as methods to improve the properties of wheat gluten-based plastics.

1. The Chemistry and
Development of
Biodegradable Plastics
Denise Williamson
September 3, 2015
1

2. Introduction
• Conventional petroleum-based or “petro”
plastics are still in large scale production
• To curb consumption, sustainably produced,
biodegradable, non-toxic “bioplastics” are
ideal
2

3. Petro-plastics
• Conventional “petro-plastics” include
– Poly(styrene)
• Medical prosthetics, foam packaging
– Poly(ethylene)
• “Ziploc” bags, poly(ethylene terepthalate) for water bottles
– Poly(propylene)
• Reusable containers, carpeting
3

4. 4
Figure 1.
[a] poly(styrene),
[b] poly(ethylene terepthalate)
and [c] poly(propylene)

5. Plastics
• Plastics are polymers that can be molded when
hot and retain their shape when cooled.1
• To be functional for practical use, any plastic must
possess adequate:
– Hydrophobicity
– Thermal stability
– Mechanical strength
5
1. Brown, W. H.; Foote, C. S.; Iverson, B. L. Organic Chemistry, 4th ed.; Thomson Brooks/Cole: California, 2005.

6. Bioplastic Blends
• Successful blending of polymers to produce
functional bioplastics is challenging
• However, recent studies demonstrate that
complementary effects are possible
6

7. Corn Starch/PDMS Elastomers
• Synthesis demonstrated the successful
incorporation of a bio-based, hydrophilic filler
into a PDMS matrix
• Elastomer: polymer with crosslinked linear chain
molecules1
– Ensures elasticity
– Returns to its original shape after deformation
– “Rubber”
71. The Engineering Toolbox: Elastomers. http://www.engineeringtoolbox.com/elastomers-rubbers-d_1788.html (accessed Aug 10, 2015).

8. PDMS
• Poly(dimethylsiloxane)
– Silicone polymer used in manufacture of
microfluidic chips, shampoos, breast implants
8
Figure 2. PDMS

9. PDMS
• Flexible: a low energy barrier for rotation around
the Si-O bond1
• Hydrophobic: methyl groups line siloxane
backbone
• Biodegrades slowly but non-toxic
– Bacteria and enzymes in marine environments can
degrade PDMS2
9
1. Owen, M. J.; Dvornic, P. R. Silcone Surface Science; Springer Science and Business Media: Dordrecht, 2012.
2. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

10. Corn Starch
• Bio-based, sustainable, non-toxic filler
– 80-90% amylopectin and 10-20% amylose1
– -D-glucose residues comprise both its amylose
chains and branched amylopectin fractions2
10
1. Lu, D. R.; Xiao, C. M.; Xu, S. J. Starch-based completely biodegradable polymer materials. eXPRESS Polym. Lett. 2009, 3, 366-375.
2. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on Corn
Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

11. Figure 3.
-D-Glucose
11Image Source: Lecture Notes #8: Carbohydrates. http://plaza.ufl.edu/tmullins/BCH3023/carbohydrates.html (accessed Aug 8, 2015)

12. 12
Figure 4.
Amylopectin
Image Source: Lecture Notes #8: Carbohydrates. http://plaza.ufl.edu/tmullins/BCH3023/carbohydrates.html (accessed Aug 8, 2015)

13. Corn Starch
• Can participate in surface hydrogen bonding
via its many hydroxyl groups
• Hydrophilicity makes granular corn starch
problematic in hydrophobic matrices1
13
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

14. Corn Starch
• Adsorbed moisture naturally present on
starch particles can:
– Generate bubbles during processing
– Degrade final products1
14
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

15. • E-type or acetoxy-PDMS elastomers
• Synthesized by condensation polymerization
15
Corn Starch/PDMS Elastomers

16. • It was indicated that acetylation of the starch
particle surface occurred during synthesis of
E-type elastomers
– Increased compatibility between starch and
hydrophobic PDMS matrix1
– Resulted in an even dispersion of starch granules
throughout PDMS networks
16
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.
Corn Starch/PDMS Elastomers

17. Synthesis: E-type (acetoxy-PDMS)
Elastomers
17
Figure 5. Condensation of hydroxyl end-blocked
poly(dimethylsiloxanes) and methyltriacetosilanes1
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

18. Synthesis: E-type Elastomers
18
Figure 6. Hydrolysis of acetoxy-polyorganosiloxanes to silanols
and condensation with more acetoxy-polyorganosiloxanes.1
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

19. Figure 7.
a) ATR-FTIR spectra of pure PDMS, acetoxy-PDMS Elastomers
and pure starch1
19
1. Ceseracciu, L.; Heredia-Guerrero, J. A.; Dante, S.; Athanassiou, A.; Bayer, I. S. Robust and Biodegradable Elastomers Based on
Corn Starch and Polydimethylsiloxane (PDMS). Appl. Mater. Interfaces, 2015, 7, 3742-3753.

20. Plastics: Macromolecular Structure
• Solid state plastics vary in composition and can contain:
– Crystalline regions1
• Highly ordered, densely packed molecules
– Amorphous
• Regions where polymer chains are disordered
– Semicrystalline
• Intermediate zones
1. Brown, W. H.; Foote, C. S.; Iverson, B. L. Organic Chemistry, 4th ed.; Thomson Brooks/Cole: California, 2005.
20

21. Plastics: Thermal Behavior
• With an increase in temperature, plastics can undergo
three main phase transitions:
– Glass transition (Tg)1
• Polymer chains have gained mobility
• Goes from a rigid, “glassy” to a flexible, “rubbery” state
– Cold crystallization (Tcc)2
• Amorphous regions rearrange into ordered structures
– Melt transition (Tm)1
• Crystalline regions melt
21
1. Brown, W. H.; Foote, C. S.; Iverson, B. L. Organic Chemistry, 4th ed.; Thomson Brooks/Cole: California, 2005.
2. Wellen, R. M. R.; Rabello, M. S. The kinetics of isothermal cold crystallization and tensile properties of poly(ethylene
terephthalate). J. Mater. Sci. 2005, 40 , 6099-6104.

22. PHBV
• Poly(3-hydroxybutyrate-co-hydroxyvalerate)
– Harvested from microorganisms
– High percent crystallinity
– High heat deflection temperature (HDT)
• HDT is that at which a plastic will deflect 0.25 mm under
0.455 MPa1
22
1. Turi, E. A. Thermal Characterization of Polymeric Materials, 2nd
ed.; Academic Press: New York, 1997.

23. PLA and PBS
• Poly(lactic acid)
– Derived from corn or sugarcane
– Highly amorphous
– High stiffness
– Low impact resistance and HDT
• Poly(butylene succinate)
– Synthetically produced
– Superior flexibility and toughness
– Lowest melting point (Tm)
23

24. • Complementary and synergistic effects were
achieved by blending PHBV, PLA and PBS1
– Mechanical properties
• Improved toughness (flexibility) but retention of
stiffness (rigidity)
– Thermal resistance
24
PHBV/PLA/PBS Blends
1. Zhang, K.; Mohanty, A. K.; Misra, M. Fully Biodegradable and Biorenewable Ternary Blends from Polylactide,
Poly(3-hydroxybutyrate-co-hydroxyvalerate) and Poly(butylene succinate) with Balanced Properties. Appl. Mater.
Interfaces, 2012, 4, 3091-3101.

25. Figure 8.
PLA, PHBV and PBS1
25
1. Zhang, K.; Mohanty, A. K.; Misra, M. Fully Biodegradable and Biorenewable Ternary Blends from Polylactide,
Poly(3-hydroxybutyrate-co-hydroxyvalerate) and Poly(butylene succinate) with Balanced Properties. Appl. Mater.
Interfaces, 2012, 4, 3091-3101.

26. • Thermal behavior of PHBV/PLA/PBS blends characterized by DSC
(Differential Scanning Calorimetry)
– Employed for the thermal analysis of polymers
• Melting thermogram
– Allows identification of Tg, Tcc, Tm
• Cooling thermogram
– Identification of temperature of crystallization (Tc)
26
PHBV/PLA/PBS Blends

27. DSC: PHBV/PLA/PBS Blends
27
Figure 9.
DSC melting (left) and cooling (right) thermograms for
A) PBS, B) PHBV, C) PLA, D) PLA/PHBV/PLA 60/30/10, E) PLA/PHBV/PBS 60/10/30,
F) PHBV/PLA/PBS 60/30/10 and G) PHBV/PLA/PBS 60/10/301
1. Zhang, K.; Mohanty, A. K.; Misra, M. Fully Biodegradable and Biorenewable Ternary Blends from Polylactide,
Poly(3-hydroxybutyrate-co-hydroxyvalerate) and Poly(butylene succinate) with Balanced Properties. Appl. Mater.
Interfaces, 2012, 4, 3091-3101.

28. • Best balance of thermal and mechanical properties
obtained by PHBV/PLA/PBS 60/30/10 blend1
28
PHBV/PLA/PBS Blends
Table 1. Heat Deflection Temperatures of PLA, PHBV, PLA/PHBV/PLA 60/30/10,
PLA/PHBV/PBS 60/10/30, PHBV/PLA/PBS 60/30/10 and PHBV/PLA/PBS 60/10/301
1. Zhang, K.; Mohanty, A. K.; Misra, M. Fully Biodegradable and Biorenewable Ternary Blends from Polylactide,
Poly(3-hydroxybutyrate-co-hydroxyvalerate) and Poly(butylene succinate) with Balanced Properties. Appl. Mater.
Interfaces, 2012, 4, 3091-3101.

29. Wheat Gluten
• Wheat gluten (WG) is renewable,
biodegradable and non-toxic
• Processing results in brittle materials prone to
moisture absorption1
29
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

30. Wheat Gluten
• Comprised of two main proteins:
– 60-75% Gliadins (monomeric; 28-55 kDa)
– 25-40% Glutenins (polymeric; 100 kDa-10 MDa)
30
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

31. PEMA
• Poly(ethylene-alt-maleic anhydride) is a
crosslinking agent
• Can form covalent bonds with proteins of
wheat gluten1
– Creates a network structure within wheat gluten
31
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

32. Figure 10.
PEMA [poly(ethylene-alt-maleic anhydride)]
32

33. SE-HPLC:WG/PEMA Blends
• WG/PEMA blends were characterized by Size-
Exclusion High Performance Liquid
Chromatography
• Proteins were extracted from samples with a
0.05 M sodium phosphate buffer containing
2% (w/v) sodium dodecyl sulfate (SDS)1
33
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

34. 34
SE-HPLC:WG/PEMA Blends
• For wheat gluten, an elution peak attributed to
glutenins was not seen for WG/5% PEMA blend
• Elution peak(s) attributed to the lower MW
gliadins progressively decreased as sample PEMA
content increased
• Crosslinking between wheat gluten and PEMA
“trapped” the proteins

35. Figure 11.
SE-HPLC Elution Profiles of WG and WG/PEMA Blends.1
35
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

36. Figure 12.
Phase morphology vs. propagating crack (--->) in
a) Wheat gluten (WG), b) WG/PEMA and
c) Intermolecular crosslinks in WG/PEMA.1
36
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

37. Wheat Gluten/PEMA Blends
• Dynamic mechanical analysis (DMA) testing
results of wheat gluten/PEMA blends
indicated that:
• Intermolecular crosslinking can increase
mechanical strength1
37
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

38. Table 2.
Flexural Stress, percent strain and flexural modulus of wheat
gluten, PEMA and WG/PEMA blendsa relative to poly(styrene).1
38
1. Diao, C.; Xia, H.; Noshadi, I.; Kanjilal, B.; Parnas, R. S. Wheat Gluten Blends with a Macromolecular Cross-Linker for Improved
Mechanical Properties and Reduced Water Absorption. Sustainable Chem. Eng. 2014, 2, 2554-2561.

39. PLA/DDGS Composites
• Biodegradation of PLA greatly accelerated by
incorporation of 20% DDGS
• Distiller’s Dried Grains with Solubles (DDGS) is
a cheap agricultural byproduct
• DDGS: cellulose (39.2-61.9%), protein (26.8-33.7%),
fatty acids (3.5-12.8%) and ash (2.0-9.8%)1
39
1. Lu, H.; Madbouly, S. A.; Schrader, J. A.; Srinivasan, G.; McCabe, K. G.; Grewell, D.; Kessler, M. R.; Graves, W. R. Biodegradation Behavior of
Poly(lactic acid) (PLA)/Distiller’s Dried Grains with Solubles (DDGS) Composites. Sustainable Chem. Eng. 2014, 2, 2699-2706.

40. PLA/DDGS Composites
• DSC characterization of PLA/DDGS 80/20 composite:
– Pure PLA and PLA/DDGS had each had a single
glass transition (Tg)1
– Demonstrated that PLA and DDGS were miscible
– Two-component, phase separated blend would
have shown two glass transitions
40
1. Lu, H.; Madbouly, S. A.; Schrader, J. A.; Srinivasan, G.; McCabe, K. G.; Grewell, D.; Kessler, M. R.; Graves, W. R. Biodegradation Behavior of
Poly(lactic acid) (PLA)/Distiller’s Dried Grains with Solubles (DDGS) Composites. Sustainable Chem. Eng. 2014, 2, 2699-2706.

41. Figure 13.
a) SEM micrograph of PLA/DDGS composite surface
(b) Biodegradation rate as % weight loss versus time (weeks).1
41
1. Lu, H.; Madbouly, S. A.; Schrader, J. A.; Srinivasan, G.; McCabe, K. G.; Grewell, D.; Kessler, M. R.; Graves, W. R. Biodegradation Behavior
of Poly(lactic acid) (PLA)/Distiller’s Dried Grains with Solubles (DDGS) Composites. Sustainable Chem. Eng. 2014, 2, 2699-2706.

42. Conclusion
• Bio-based materials such as corn starch and
wheat gluten may be successfully
incorporated into bioplastic blends
• Both improved mechanical properties and
thermal stability can be attained in blends of
three bio-based polymers
42

43. • The biodegradation of a bioplastic may be
accelerated by the addition of an agricultural
by-product
• These results suggest the value of further
research into bioplastics composed of PHBV,
PLA, PBS, PEMA, PDMS, wheat gluten, corn
starch and/or DDGS
43
Conclusion

44. • Flexural strength is a material’s ability to resist
bending
• Flexural modulus is the ratio of applied
flexural stress to percent strain
– Percent strain is given by the ratio of deformed
length to initial length
44
Plastics: Flexural Strength

45. • In plastic blends, mechanical strength
depends on phase morphology
– Phase morphology originates from intermolecular
dynamics
• Dynamic mechanical analysis (DMA) tests
measure the mechanical properties of plastics
45
Plastics: Mechanical Properties

46. Microfluidic chips
• Microfluidics deals with the flow of liquid inside micrometer-size (10 -6 m)
channels
• A microfluidic chip is a set of micro-channels etched or molded into a
material (glass, silicon or polymer such as PDMS, for
PolyDimethylSiloxane).1
• The micro-channels forming the microfluidic chip are connected together
in order to achieve desired functions (mix, pump, sort, control bio-
chemical environment)
• Biomedical use: “Lab on a chip,” allow integration of many medical tests
on one chip
• Cell biology: micro-channels have the same characteristic size as biological
cells; allows easy manipulations of single cells
46
1. Microfluidics and Microfluidic Devices: A Review.
http://www.elveflow.com/microfluidic-tutorials/microfluidic-reviews-and-tutorials/microfluidics-and-microfluidic-device-a-review/
(accessed Sept 2, 2015)