**5. Conclusions**

Although the use of starch in loose-fill products gives advantages in the form of biodegradability and environmental protection, these products have been criticized for their imperfection compared with EPS loose-fill products. EPS- and starch-based foams have differences, but the differences do not compromise performance.

These products differ with respect to composition and method of manufacture. Foam and bulk densities, which are higher by a factor of two to three times than either EPS-based foams, are attributable to the density of starch, which is 50% higher than polystyrene

The foam samples conditioned at 50% relative humidity for one week at room temperature and then tested yielded up to 73% recovery after 1 h of force removal. The recovery was reduced with the reduction in starch content. Water can be a good plasticizer for starch, and PLA could reduce water diffusion into the starch phase. After immersing the foams in distilled water at room temperature for one week, however, foams with PLA showed instant recovery to their original shape after one minute of force removal regardless of PLA/starch ratio.

The addition of poly(hydroxyamino ether) (PHAE) to starch improved the foam resiliency considerably from 69,7% (only starch) to 93,5% at a PHAE content of 7% of the starch used

Friability is a measure of the fragmentation of foam during handling. Fragmentation of loose-fill during handling and use is an important product quality concern among endusers. Tests made by Tatarka and Cunningham (1998) indicated that the friability of commercial starch-based foams ranged between 0,003 and 2,3%. Although these values are lower than EPS-based foams, they are not significantly different. After conditioning, the friability of these starch-based foams increased significantly when exposed to 80% r.h. and 23°C 50% r.h. and 35°C. Quantitatively, starch- and EPS-based foams fragmented similarly at 2 to 6 % of the total weight, but starch-based foams broke down into a fine dust, whereas

Willet and Shogren (2002) founded that friability of starch/polymer foams is high for all tested formulations and starches at 10% r.h. Of the control starch foams, only the high amylose starch has friabilityof less than 95%. Under these conditions, the starch matrix is well below its glass transition temperature and its brittle. As the relative humidity increases to 50%, the equilibrium moisture content of the starch rises, and the foams are consequently less brittle. The friability decreases significantly, but only the high amylose starch foam displays negligible friability (0,4%). The addition of polymer generally reduces friability at 50% r.h. Corn starch loss-fills with the greatest density also exhibited greater friability, while corn starch foams with low densities had insignificant levels of friability. Friability decreases as polymer surface concentration increases. The presence of a ductile polymer on the foam surface may retard the formation of cracks and fragments under impact by the wooden blocks. One cannot, however, rule out indirect effects of the polymer on foam structure, i.e. lower foam density and thinne

Although the use of starch in loose-fill products gives advantages in the form of biodegradability and environmental protection, these products have been criticized for their imperfection compared with EPS loose-fill products. EPS- and starch-based foams have

These products differ with respect to composition and method of manufacture. Foam and bulk densities, which are higher by a factor of two to three times than either EPS-based foams, are attributable to the density of starch, which is 50% higher than polystyrene

(Nabar & Narayan, 2006).

virgin EPS-based foams broke into large fragments.

cell walls as contributing to the greater flexibility of the foam structure.

differences, but the differences do not compromise performance.

**4.5 Friability** 

**5. Conclusions** 

homopolymer and to the direct water-to-steam expansion process, which creates a predominately open cellular structure that stops foam expansion. Starch-based foam loosefill is very hygroscopic. Foam density of starch-based products is significantly increasing between 10 and 30% after conditioning at high humidity.

The compressive stress of most starch-based foams does not differ significantly from EPS products. Chemically modified starches gives foams with good retention of compressive stress over a broad humidity range.

The resiliency of starch-based foams with values between 69,5 and 71,2% are, as a group, about 10% lower on a relative basis than EPS foams. Although starch-based foams absorbs 13 to 16 wt % moisture after conditioning at 80% r.h. and 23°C, these products are retaining between 62 and a 67% resiliency.

Both starch- and EPS-based foam fragmentation amounts to 2 to 6 wt %, but starch-based breaks down into a fine dust, whereas EPS-based foams breaks into large fragments.

All starch-based foams have a significantly higher foam and bulk density and open cell and moisture content than EPS-based foam. Both product types have similar compressive stress, resiliency, and friability. Starch-based foams are more sensitive to changes in relative humidity and temperature than EPS-based foam, but the higher amount of absorbed moisture does not compromise its mechanical integrity.

Generally, extrusion technique can be successfully employed for starch-based foams production. The physical properties of loose-fills, such as density, porosity, cell structure, water absorption characteristics and mechanical properties are highly dependent on the raw materials and additives. Mechanical behaviour of foamed pellets can be adjusted effectively by controlling the cell structure through using different additives. At room temperature and 50% relative humidity, some mechanical properties, such as compressive strength or compressive modulus of elasticity are comparable to commercial EPS foams.

Starch-based foams can be prepared from different starch sources replacing 70% polystyrene with biopolymer starch. Functional starch-based plastic foams can be prepared from different starch sources depending on their availability.

Starch-based foams with polymer addition (for example: PS, PMMA, PHEE) exerts improved properties in comparison with 100% starch foams. The addition of polymers significantly increases radial expansion and gives low density foams. Compressive strength is depending primarily on foam density, and not on starch type or polymer structure. Friability is reduced when polymer is present in the foam.

Foams of PLA/starch can be successfully prepares by using water as a blowing agent in the presence of talc, which acts as an effective nucleation agent. Water is a good blowing agent for the PLA/starch system. Talc at 2% gives the PLA/starch foam fine foam cell size and uniform cell size distribution.

The addition of Mater-Bi is affecting the foam expansion characteristic. High levels of MBI are resulting in low radial expansions and high densities. The resiliency is improving as the levels of MBI and moisture contents are increasing. The MBI-starch foams have the potential to be used as an environmentally friendly loose-fill packaging material.

Starch Protective Loose-Fill Foams 93

Mitrus, M. (2009). TPS and Its Nature. In: *Thermoplastic Starch. A Green Material for Various* 

Mitrus, M. & Moscicki, L. (2009). Extrusion-Cooking of TPS. In: *Thermoplastic Starch. A Green* 

Nabar, Y.; Narayan, R. & Schindler, M. (2006). Twin-Screw Extrusion Production and

Nabar, Y.U.; Draybuck, D. & Narayan, R. (2006). Physicomechanical and Hydrophobic

Shogren, R.L. (1993). Effects of moisture and various plasticizers on the mechanical

Shogren, R.L.; Fanta, G.F. & Doane, W.M. (1993). Development of starch based plastics – a

Shogren, R. L.; Lawton, J. W. & Tiefenbacher, K. F. (2002). Baked starch foams, starch

Tatarka, P. D. & Cunningham, R. L. (1998). Properties of Protective Loose-Fill Foams. *Journal of* 

Van Soest, J.J.G. Benes, K. & de Wit, D. (1996). The influence of starch molecular mass on the

Van Soest, J.J.G.; Bezemer, R.C.; de Wit, D. & Vliegenthart J.F.G. (1996). Influence of glycerol

ISBN 1566760089, Lancaster-Basel, USA-Switzeland

No.8, (May 1993), pp. 276-280, ISSN 1521-379X

2001), pp.17-24, ISSN 1098-2329

1995), pp. 3543-3552, ISSN 0032-3861

1995), pp. 1-9, ISSN 0926-6690

GmbH&Co. KGaA, ISBN 978-3-527-32528-3, Weinheim, Germany

2002), pp. 355-361, ISSN 0144-8617

438–451, ISSN 1548-2634

131-137, ISSN 1521-379X

*Industries*, Janssen L.P.B.M., Moscicki L. (Eds.), 77-104, Wiley-VCH Verlag

*Material for Various Industries*, Janssen L.P.B.M., Moscicki L. (Eds.), 77-104, Wiley-VCH Verlag GmbH&Co. KGaA, ISBN 978-3-527-32528-3, Weinheim, Germany Moscicki, L. (2011). *Extrusion-Cooking Techniques. Applications, Theory and Sustainability*. Wiley-VCH Verlag GmbH&Co. KGaA, ISBN 978-3-527-32888-8, Weinheim, Germany Myllärinen, P.; Partanen, R.; Seppälä, J. & Forssell P. (2002). Effect of glycerol on behaviour

of amylose and amylopectin films. *Carbohydrate Polymers*, Vol.50, No.4, (February

Characterization of Starch Foam Products for Use in Cushioning and Insulation Applications. *Polymer Engineering and Science*, Vol.46, No.4, (February 2006), pp.

Properties of Starch Foams Extruded with Different Biodegradable Polymers. *Journal of Applied Polymer Science*, Vol.102, No.1, (July 2006), pp. 58–68, ISSN 1097-4628 Nashed, G.; Rutgers, R.P.G. & Sopade, P.A. (2003). The plasticisation effect of glycerol and

water on the gelatinisation of wheat starch. *Starch*, Vol.55, No.3-4, (March 2003), pp.

properties of extruded starch. In: *Biodegradable polymers and packaging*, Ching Ch., Kaplan D.L., Thomas E.L., (Eds.), 141-149, Technomic Publishing Company Inc.,

reexamination of selected polymer systems in historical perspective. *Starch*, Vol.45,

modifications and additives improve process parameters, structure and properties. *Industrial Crops and Products*, Vol.16, No.1, (January 2002), pp. 69–79, ISSN 0926-6690 Song, J. H. (2005). Lightweight sandwich panels based on starch foam. *Proceedings of CIMNFC LINK seminar*, Warwick University, Warwick, 19th April 2005 Souza, R.C.R. & Andrade, C.T. (2002). Investigation of the gelatinization and extrusion

processes of corn starch. *Advances in Polymer Technology*, Vol.21, No.1, (October

*Applied Polymer Science*, Vol.67, No. 7, (February 1998), pp. 1157–1176, ISSN 1097-4628

properties of extruded thermoplastic starch. *Polymer*, Vol.37, No.16, (December

on melting of potato starch. *Industrial Crops and Products*, Vol.5, No.1, (September

#### **6. References**


Avérous, L.; Fringant, C. & Moro, L. (2001). Starch – based biodegradable materials suitable

Bastioli, C.; Bellotti, V.; Del Tredici, G.; Montino, A. & Ponti, R. (1998). Biodegradable

Bastioli, C.; Bellotti, V.; Del Tredici, G. & Rallis, A. (1998). Biodegradable foamed articles and

Bellotti, V.; Bastioli, C.; Rallis, A. & Del Tredici, G. (2000). Expanded articles of

Bhatnagar, S. & Hanna, M. A. (1995). Properties of extruded starch-based plastic foam. *Industrial Crops and Products*, Vol.4, No.2, (February 1995), pp. 71–77, ISSN 0926-6690 Bhatnagar, S. & Hanna, M. A. (1996). Starch-Based Plastic Foams From Various Starch Sources. *Cereal Chemistry*, Vol.73, No.5, (May 1996), pp. 601-604, ISSN 0009-0352 Cha, J. Y.; Chung, D. S.; Seib, P. A.; Flores, R. A. & Hanna, M. A. (2001). Physical properties of

foamed plastic materials. US Patent 5,736,586

process for preparation thereof. US Patent 5,801,207

No.3, (August 2000), pp. 219-227, ISSN 0926-6690

Vol.77, No.12, (June 2000), pp. 2575-2580, ISSN 1097-4628

Vol.27, No.8., (May 1999), pp. 336–383, ISSN 09598111

ISBN 0-913250-67-8, St. Paul, Minnesota, USA

(July 1999), pp. 317-325, ISSN 0144-8617

2000), pp. 1809-1815, ISSN 0022-2461

for thermoforming packaging. *Starch*, Vol.53, No.8, (August 2001), pp.368-371, ISSN

biodegradable plastic material and a process for the preparation thereof. Europe

starch-based foams as affected by extrusion temperature and moisture content. *Industrial Crops and Products*, Vol.14, No.1, (October 2000), pp. 23–30, ISSN 0926-6690 De Graaf, R.A.; Karman, A.P. & Janssen, L.P.B.M. (2003). Material properties and glass

transition temperatures of different thermoplastic starches after extrusion processing. *Starch*, Vol.55, No.2, (December 2002), pp. 80-86, ISSN 1521-379X Fang, Q. & Hanna, M.A. (2001). Characteristics of biodegradable Mater-Bi-starch based

foams as affected by ingredient formulations. *Industrial Crops and Products*, Vol.13,

pectin/starch blends plasticized with glycerol. *Carbohydrate Polymers*, Vol.41, No.4,

from bark and starch. I. Highly resilient foams. *Journal of Applied Polymer Science*,

extruded high amylase starch for loose-fill packaging material. *Lebensmittel-Wissenschaft und-Technologie,* Vol.28, No.2, (September 1994), pp. 163-168, ISSN

performance of thermoplastic starch. *Journal of Materials Science*, Vol.36, No.7, (July

*Journal of Applied Polymer Science*, Vol.63, No.8, (April 1996), pp. 1047-1053, ISSN

protective packaging. *Plastics Rubber and Composites Processing and Applications*,

Fishman, M.L.; Coffin, D.R.; Konstance, R.P. & Onwulata C.I. (2000). Extrusion of

Ge, J.; Zhong, W.; Guo, Z.; Li, W. & Sakai, K. (2000). Biodegradable polyurethane materials

Harper, J. M. (1981). *Extrusion of foods*, CRC Press Inc., ISBN 0849352037, Boca Ration, FL., USA Lin, Y.; Huff, H.E.; Parsons, M.H.; Iannotti, E. & Hsieh, F. (1995). Mechanical properties of

Liu, Z.Q.; Yi, X.S. & Feng, Y. (2001). Effects of glycerin and glycerol monostearate on

Lourdin, D.; Bizot, H. & Colonna, P. (1997). "Antiplasticization" in starch – glycerol films?.

Lye, S. W.; Lee, S. G. & Chew, B. H. (1999). Characterisation of biodegradable materials for

Mercier, C.; Linko, P. & Harper, J. M. (1998). *Extrusion Cooking* (2nd edition). AACCH Inc.,

**6. References** 

1521-379X

Patent EP0989158

0023-6438

1097-4628


**1. Introduction** 

temperature of the starch.

with adaption for the specific characteristics of starch.

**6** 

 *Australia* 

**Thermoplastic Starch** 

*Applied Sciences, RMIT University, Melbourne* 

Thermoplastics are polymers that can flow when heated above a melting or vitrification temperature. They undergo plastic deformation, meaning viscous flow with often-complex rheology due to their large molar mass, entanglements, interactions and chain branches. Starch is a natural polymer with complex levels of structure that impinge upon thermoplastic deformation. Natural polymers are no different to synthetic polymers once some added levels of structural complexity are understood (Wunderlich, 2011). Starch is a semi-crystalline polymer that does not melt in the traditional sense to form a liquid. Starch melting does mean loss of crystallinity due to disruption of hydrogen bonds, however melting occurs in the presence of a moderate (10-30 %·w/w) water content. Starch crystals contain about 9-10 %·w/w of bound water, where bound water means water that does not freeze when cooled below 0 °C. Additional water is required for melting of starch at convenient temperatures below the boiling temperature of water and the degradation

Starches are applicable to thermoplastic processing, unlike other polysaccharides such as cellulose and various gums. Cellulose is a natural structural polymer designed for regularity of packing, chain stiffening and strong cohesion via hydrogen bonding. Cellulose is a structural polymer forming cell walls in plants and it cannot be melted at moderate temperatures when only water is present. Cellulose has interesting solution properties of practical importance since solution processing is the method for transforming cellulose into fibres and films. Starch is an energy storage polymer designed for reversible chain propagation and reversible structure formation to allow access to enzymes for its energy forming degradation. Starch is a biopolymer that is biodegradable, suitable for green packaging materials providing that it can be formulated and readily processed into usable forms. Traditional processing equipment such as extrusion and thermoforming can be used

Thermal processing of starch has been reviewed as to changes in microstructure, phase transitions and rheology as a consequence of processing technique, conditions and formulations (Liu, Xie, Yu, Chen, Li, 2009). Starch has a unique microstructure that contributes multiphase transitions during thermal processing that provides an illustrative model to demonstrate conceptual approaches to understanding structure-processingproperty relationships in all polymers. A unique characteristic of starches is their thermal processing properties that are considerably more complex than those of conventional

Robert Shanks and Ing Kong

