Starch-Based Foams

Starch-based foam loosefill packaging shapes are also available. While starch was not traditionally considered a plastic, the technique for producing these foams involves plasticizing the starch with water (and sometimes additional plasticizing agents) in an extruder and molding it. Starch foam shapes and cushions compete with loosefill PS and molded PS cushions. 

The major advantage of starch-based foams is that they are considered by many to be more environmentally friendly, in part due to their water solubility. A related disadvantage is their tendency to be susceptible to moisture sorption, which may even result in collapse in environments with very high humidity. There have also been concerns, for some starch-based cushioning materials, about rodent or insect infestation. 

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In packaging, Ecoflex can be used as a coating material to make paper, cardboard or starch-based foam tougher and protect against fat, moisture and temperature variations. These are useful properties for hamburger boxes, coffee cups, packaging for meat, fish, poultry, fruit or vegetables, food dishes and fast-food boxes. 

Loose-fill packaging was one of the first successful areas of application for starch-based biodegradable polymers. Loose-fill starch-based foam is used for packaging consumer products as an alternative to polystyrene and polyethylene. While, biodegradable plastics have made some inroads into these markets, the future prospects for their growth in loose-fill are not so exciting as they are in some other areas of packaging. 

Explosion puffing is the oldest technique used to create starch-based foams from starch feedstock with low moisture content. A typical example of this is making popcorn a kernel explosion puffs naturally at about 177 °C and requires only 10-15 % moisture to achieve maximum volume [146]. Explosion puffing can produce low-density starch-based foams within several seconds, however the performance of the foamed products is poor. 

Glenn and Orts [153] describe another technique for making starch-based foams using a compression-explosion process. Starch feedstock is compressed in a heated mould at 230 °C under a 3.5 MPa clamping force for 10 s, which is then... 

The properties of foams made from pure starch are limited however mechanical properties are poor and starch foam is very sensitive to changes in relative humidity. To improve these characteristics, starch is chemically and physically modified or blended with other additives or polymers. This approach has proven to be very effective. Various starch-based foams have been introduced in the market, mainly in loose fill applications ... 

As an alternative to these materials the objective in this research will be to produce starch based resilient thermoplastic foams based totally on native potato starch. This is done in two steps the production of expandable thermoplastic starch beads by extrusion and foaming of the expandable beads after conditioning in a successive foaming step. The properties of these foams will be studied as a function of processing parameters and material composition. A further objective is to determine the ultimate properties of pure starch based foams. 

The characteristics of the developed material demonstrate that pure potato starch can be used for the production of foams without the need of modified starches or blends with other additives or polymers. This will make new applications for thermoplastic starch based foams possible. 

Starch-based foams can provide compostable packaging for the fast-food industry The extruded starch foam can be coated with a outer layer of acetylated starch to provide water resistance, or a foamed starch-acetylated starch hlend can be so coated (76,77). Starch has also been coated with the microbial polyester PHBV to provide resistance to hot and cold water a natural resin, shellac, prevents delamination (78) (Fig. 8). 

There has been a growing interest in the development of starch-based products in recent years. Starch-based foams have been seen as a potential alternative to expandable polystyrene. PLA/starch (native and acetylated) composites can be foamed with both physical and chemical foaming agents in conventional processing equipment [5, 87-91]. 

Mitrus y Moscicki (2014) showed, for example, that the appUcalion of extrusion-cooking technique to process starch-plasticizer mixtures can be one of the most economical and efficient ways to produce TPS loose-fill foams. Then extrusioncooking technique can be successfully employed for starch-based foams production. 

Besides being readily biodegradable in the environment, starch-based foams offer superior antistatic properties. However, they are brittle and their densities are higher than expanded polystyrene (EPS) [14]. 

Fang Q, Hanna MA. Preparation and characterization of biodegradable copolyester-starch based foams. Bioresour Technol 2001 78 115. 

The main use of thermoplastic starch alone is in foam applications. Starch-based foams have been found to be an effective alternative to PS foam in loose-fill protective packaging. Starch-based foams offer the advantage that they are readily biodegradable if they escape into the environment. They also offer superior antistatic properties. Starch-based foam, however, has some disadvantages it is brittle and the density is higher than PS. Foamed, starch-based articles are prepared by heating starch in an extruder in the presence of water with subsequent extrusion. 

One of the most crucial properties in packaging applications is bulk density. A comparison of bulk densities of expanded polystyrene loose-fill with starch-based foams is given in Table 6.1. 

An important starch-based foam is Novamont s Mater-Bi Class V grade material. The content of thermoplastic starch is more than 85% [12]. Novamont in Italy has patented... 

Lee, S. Y., Eskridge, K. M., Koh, W. Y., and Hanna, M. A. 2(X)9. Evaluation of ingredient effects on extruded starch-based foams using a supersaturated split-plot design. Industrial Crops and Products 29 427-436. 

Zhou, J., Song, J., and Parker, R. 2006. Structure and properties of starch-based foams prepared by microwave heating from extruded pellets. Carbohydrate Polymers 63 466-75. 

Kraft fiber or kraft pulp is darker than other wood pulps, but it can be bleached to make very white pulp. Fully bleached kraft pulp is used to make high-quality paper where strength, whiteness, and resistance to yellowing are important. The kraft process is an industrial method amply used to extract cellulosic pulp from wood. Kaisangsri et al. (2012) mixed kraft fiber with cassava starch solution, later chitosan solution was added, and a hot mold baking was used to form the cassava starch-based foam by using an oven machine with controlled temperature. 

Kaisangsri et al. (2012] studied the biodegradable foam tray from cassava starch blended with natural fiber (kraft fiber] and chitosan. They observed that the addition of chitosan into the cassava-starch based foam decreases L values but increases a and b values, also cassava starch-based foams mixed with high concentrations of chitosan were yellow color because chitosan imparts this coloring (Fig. 15.7]. 

Figure 15.7 Effect of chitosan concentration and fiber content on (A] lightness (Z, ), (B) redness (a ), and (C) yellowness [ft ) of cassava starch-based foam. Reprinted from Kaisangsri et ai., 2012, with permission from Eisevier.

A wide variety of materials have been examined with starch. Nevertheless, the combination with chitosan and the use of natural fibers as reinforcement helps to improve compatibility, in addition to achieving the production of new composites. For example, kraft fiber improved quality and properties of cassava starch-based foam for applicable of fresh cut fruits that were comparable to polystyrene foam. Keratin fiber reinforcements, had good compatibility with... 

Fang Q, Hanna M A (2001), Characteristics of biodegradable Mater-Bi and starch-based foams as affected by ingredient formulation , Ind. Crops. Prod., 13, 219-227. 

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 in relation to EPS loose-fiU products. EPS- and starch-based foams have differences, but the differences do not compromise performance. 

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