Recent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability

doi:10.1016/j.carbpol.2011.01.030

Carbohydrate Polymers

Volume 85, Issue 1, 22 April 2011, Pages 7-16

https://doi.org/10.1016/j.carbpol.2011.01.030 Get rights and content

Abstract

Recent environmental regulations, societal concerns and growing environmental understanding throughout the world have triggered renewed efforts in plastic industry to develop new products and processes compatible with our environment. This review outlines the new developments in thermoplastic starch, polyvinyl alcohol based blends and nanocomposites. 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 (such as mechanical properties, moisture sensitivity), some physical or chemical methods such as cross-linking, incorporation of new nanoparticles can be applied. With these new techniques, materials with a great variety of property profiles could be realized and they were even able to compete, both in price and in performance, with synthetic polymeric materials in different applications.

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.

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ReviewRecent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability

Abstract

Introduction

Section snippets

Starch based materials

PVOH based materials

Plasticizers for starch–PVOH blends

Starch–PVOH based nanocomposites

Biodegradability of starch–PVOH blends and nanocomposites

Applications and future prospects

Conclusions

Acknowledgement

Bioresource Technology

Food Chemistry

Biotecnology Advances

Carbohydrate Polymers

Polymer Degradation and Stability

Materials Science & Engineering

Carbohydrate Polymers

Composites Science and Technology

Carbohydrate Polymers

Carbohydrate Polymers

Journal of Cereal Science

Carbohydrate Polymers

Bioresource Technology

Polymer

Carbohydrate Polymers

Carbohydrate Polymers

Composites Science and Technology

Journal of Food Engineering

Polymer

Bioresource Technology

Composites Science and Technology

Carbohydrate Polymers

Polymer

Carbohydrate Polymers

Polymer Degradation and Stability

Polymer

Journal of Fermentation Technology

Carbohydrate Polymers

Carbohydrate Polymers

Polymer Testing

Carbohydrate Polymers

International Journal of Hydrogen Energy

Carbohydrate Polymer

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

Review
Recent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability