ReviewRecent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability
Introduction
Use of plastics has been under attack for some time because of lack of recycling facilities or infrastructure, non-recyclability, non-renewability, non-biodegradability or incorporation of toxic additives. Current trends indicate steady growth will occur in the use of biodegradable plastics with increasing availability of suitable materials and because of societal and legislative pressure (Rasato, 2009).
Starch is a widely used material for making biodegradable plastics. Starch is cheap, renewable and biodegradable, but pure starch lacks the strength, water resistibility, processability and thermal stability. To improve some of these drawbacks, starch was often blended with some biodegradable synthetic polymers such as poly (ɛ-caprolactone) (PCL), poly (lactic acid) (PLA), polyvinyl alcohol (PVOH), which have good potentials for plastic and packaging applications. PVOH is a material with a high technological potential as a water-processable or melt-processable polymer. Due to its excellent optical and physical properties, PVOH is successfully used in a wide range of industrial fields. However, PVOH is relatively expensive, and has low biodegradation rate and poor moisture barrier properties. To reduce cost and to enhance its eco-friendliness, and performance, PVOH is often modified with other polymers (such as starch) and nanoparticles.
Biodegradable plastics are now available based on thermoplastic starch, PVOH, and their blends. These materials provide environmentally advantageous biodegradable alternatives to conventional non-biodegradable materials such as polyethylene (PE) for many applications. This review will highlight the major developments in starch, PVOH based polymer blends, nanocomposites and their biodegradability. The processing and probable applications will also be discussed.
Section snippets
Starch based materials
Among all natural biopolymers, starch has been considered as one of the most promising one because of its easy availability, biodegradability, and lower cost. Starch is the major form of stored carbohydrate in plants such as corn, wheat, rice, and potatoes. Starch is composed of a mixture of two polymers of α-glucose – linear amylose and a highly branched amylopectin. Amylose molecules consist of 200–20,000 glucose units which form a helix as a result of the bond angles between the glucose
PVOH based materials
PVOH cannot be made by polymerization of vinyl alcohol, since this species does not exist in the free state. PVOH instead is prepared by partial or complete hydrolysis of polyvinyl acetate to remove acetate groups.
Most commercially available PVOH polymer grades are atactic, and the degree of crystallinity and physical properties depends on various factors such as the production processes used to make the precursor polyvinyl acetate and convert it to PVOH, the degree of hydrolysis, the molecular
Plasticizers for starch–PVOH blends
Since 1980s, starch–PVOH has been studied primarily for producing films by means of solution casting because PVOH easily degraded during the melt processing. However, from an economic viewpoint, solution processing is likely unacceptable, mainly due to the additional high processing cost and low efficiency in comparison to thermoplastic processing. In order to decrease the melting temperature of PVOH and increase the flexibility and workability of starch and PVOH, a number of plasticizers, e.g.
Starch–PVOH based nanocomposites
To further improve the moisture barrier and mechanical properties of starch–PVOH blends, polymer nanocomposite concept could be an option to be applied to the blended system.
Biodegradability of starch–PVOH blends and nanocomposites
Starch can be readily metabolized by a range of microorganisms to fermentation products such as ethanol (Bai et al., 2008, Jamai et al., 2007), hydrogen (Tadasa and Takeda, 1986, Yang and Shen, 2006) and methane (Amon et al., 2007). PVOH is also susceptible to biological degradation, however, the process was slow (Gartiser, Wallrabenstein, & Stiene, 1998). Furthermore, the overall number of PVOH-degrading microorganisms was rather limited in comparison to the widespread species able to degrade
Applications and future prospects
In general, starch–PVOH blends are biodegradable materials and have many advantages. They can be used in multiple applications. Starch–PVOH blends are being explored for replacement of LDPE films in applications where mechanical properties are critical for intended use and good moisture barrier properties are not necessary. This type of product has already been commercialized by Novamont SA (Novara, Italy) and marketed as water-soluble laundry bags. Starch–PVOH films can also be used in
Conclusions
Technology is now available for the production, processing, converting and forming of a variety of biodegradable thermoplastic formulations based on thermoplastic starch and PVOH blends. These materials show a broad and versatile range of physical properties and other advantageous characteristics at acceptable cost and biodegradation rate and can be employed in a wide range of applications. To further improve their properties, some physical or chemical methods such as cross-linking,
Acknowledgement
We would like to thank United States Department of Agriculture (USDA) for funding this project through USDA-NRI COMPETITIVE GRANT 2008 (Grant no. 20081503). This is Contribution Number 11-139-J from the Kansas Agricultural Experiment Station, Manhattan, Kansas 66506.
References (89)
- et al.
Methane production through anaerobic digetion of various energy crops grown in sustainable crop rotations
Bioresource Technology
(2007) - et al.
Biodegradable starch/clay nanocomposite films for food packaging applications
Food Chemistry
(2005) - et al.
Ethanol fermentation technologies from sugar and starch feedstocks
Biotecnology Advances
(2008) - et al.
Comparative study on the films of poly (vinyl alcohol)/pea starch nanocrystals and poly (vinyl alcohol)/native pea starch
Carbohydrate Polymers
(2008) - et al.
Biodegradation of poly (vinyl alcohol) based blown films under different environmental conditions
Polymer Degradation and Stability
(1999) - et al.
Progress in nano-biocomposites based on polysaccharides and nanoclays
Materials Science & Engineering
(2009) - et al.
A first insight on composites of thermoplastic starch and Kaolin
Carbohydrate Polymers
(2001) - et al.
Key interactions in biodegradable thermoplastic starch/poly(vinyl alcohol)/montmorillonite micro- and nanocomposites
Composites Science and Technology
(2008) - et al.
Properties of starch based blends. Part 2. Influence of polyvinyl alcohol addition and photocrosslinking on starch based on materials mechanical properties
Carbohydrate Polymers
(2005) - et al.
Phase and glass transition behavior of concentrated barley starch–glycerol–water mixtures, a model for thermoplastic starch
Carbohydrate Polymers
(1997)
Plasticization and mobility in starch-sorbitol film
Journal of Cereal Science
Synthesis and characterization of polyvinyl alcohol/nanospherical cellulose particle films
Carbohydrate Polymers
Production of ethanol from starch by free and immobilized Candida tropicalis in the presence of alpha-amylase
Bioresource Technology
A study of the glass transition of amylopectin-sugar mixtures
Polymer
Preparation and characterization of ultra violet (UV) radiation cured bio-degradable films of sago starch/PVA blend
Carbohydrate Polymers
Glycerol-plasticized films prepared from poly (vinyl alcohol) mixtures: Effect of poly (ethylene-co-acrylic acid)
Carbohydrate Polymers
Improving the mechanical properties of thermoplastic starch/poly (vinyl alcohol)/clay nanocomposites
Composites Science and Technology
Effects of controlled storage on thermal, mechanical and barrier properties of plasticized films from different starch sources
Journal of Food Engineering
Nucleation of polyvinyl alcohol crystallization by single-walled carbon nanotubes
Polymer
The anaerobic degradability of thermoplastic starch: Polyvinyl alcohol blends: Potential biodegradable food packaging materials
Bioresource Technology
Carbon nanotubes for reinforcement of plastics? A case study with poly(vinyl alcohol)
Composites Science and Technology
The effect of citric acid on the structural properties and cytotoxicity of the polyvinyl alcohol/starch films when molding at high temperature
Carbohydrate Polymers
Computational modeling and experimental infrared spectroscopy of hydrogen bonding interactions in polyvinyl alcohol–starch blends
Polymer
Rheology and thermal transition state of polyvinyl alcohol-cassava starch blends
Carbohydrate Polymers
Enzymatic degradation of some nanocomposites of poly(vinyl alcohol) with starch
Polymer Degradation and Stability
Preparation and characterization of α-chitin whisker-reinforced poly (vinyl alcohol) nanocomposite films with or without heat treatment
Polymer
Anaerobic digestion of raw starch by Bacillus species
Journal of Fermentation Technology
Effects of plasticizers on the structure and properties of starch-clay nanocomposite films
Carbohydrate Polymers
Effect of nano-SiO2 on the performance of starch/polyvinyl alcohol blend films
Carbohydrate Polymers
Testing of polyvinyl alcohol and starch mixtures as biodegradable polymeric materials
Polymer Testing
Starch films reinforced with mineral clay
Carbohydrate Polymers
Effect of ferrous iron concentration on anaerobic bio-hydrogen production from soluble starch
International Journal of Hydrogen Energy
Syntheses of PVA/starch grafted hydrogels by irradiation
Carbohydrate Polymer
Radiation modification of starch-based plastic sheets
Carbohydrate Polymer
Effect of processing on the melt degradation of starch-filled polypropylene
Polymer International
Grafting of poly (methacrylic acid) on starch and poly(vinyl alcohol)
Starch/Starke
Preparation and properties of plasticized starch/multiwalled carbon nanotubes composites
Journal of Applied Polymer Science
Evaluation of biodegradability of polyvinyl alcohol/starch blends: A methodological comparison of environmentally friendly materials
Journal of the Polymers and the Environment
Poly (vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays
Journal of Applied Polymer Science
Starch-polyvinyl alcohol cast film-performance and biodegradation
Polymer Preprints
New approach to elaborate exfoliated starch-based nanobiocomposites
Biomacromolecules
Characteristics and degradation of hybrid composite films prepared from PVA, starch and lignocellulosics
Macromolecular Symposia
Effect of compounding and starch modification on properties of starch-filled low density polyethylene
Industrial & Engineering Chemistry Research
Cited by (468)
HPLC-PDA-MS profiling of Origanum dictamnus L. infusion and its encapsulation in electrospun nanofibers for oral administration
2024, Journal of Drug Delivery Science and TechnologyZinc oxide nanoparticle-reinforced pectin/starch functionalized films: A sustainable solution for biodegradable packaging
2024, International Journal of Biological MacromoleculesStructure, rheological properties, and biocompatibility of Laponite® cross-linked starch/polyvinyl alcohol hydrogels
2023, International Journal of Biological MacromoleculesStarch-gelatin blend films: A promising approach for high-performance degradable food packaging
2023, Carbohydrate Polymers