Polyolefin-starch blends, biodegradation Products

The properties of polyolefin/starch blends depend on starch content, degree of dispersion in the polymer matrix, on sample morphology, interactions between components, degree of crystallinity, presence of structural defects as well as preparation or processing conditions. Starch was initially added into polymers as a filler to decrease the price of products. Typical examples are blends of starch with PE, PVC and mbber. Since the 1990s, starch has been blended with conventional polymers to facilitate biodegradation of polymers, in particular polyolefins. 

Table 17.7 lists the products currently being examined in agricultural applications in Taiwan. Piaster SG and EPI TDPA are oxo-biodegradable polyolefins (see Chs 3 and 12) and have been shown to oxo-biodegrade after initiation by light and heat. PE-starch blends may contain transition metal ions... 

There have been more efforts to use blends such as Nova Chemicals Arcel (an ethylene styrene interpolymer in bead form) to create a more durable foam than EPS. EPP can be moulded into complex shapes, with the steam bonding of the beads (291). These packaging foams compete with polyolefin film products such as Jiffy foam (bubblewrap) and macrobubbles made by heat sealing 150 mm lengths of tubular LDPE film. As it is difficult or costly to recycle such foam products, in some countries there is a move towards biodegradable starch foams and moulded paperboard. 

In the last five years Asian countries, and specifically China and Korea, have performed impressively in the sector of blends of thermoplastic starch with polyolefins, in terms of intellectual property and products range offered to the market. The non compliance of these products with the international norms of biodegradability and compostability, however, did not permit a significant market growth in western countries where low environmental impact products have more market potential. 

Starch in granular state has been used as filling agent for polyolefin and as a component in synthetic polymer blends. In such cases, a small amount of starch (6-30%) is blended with synthetic polymers like polyethylene (PE) or polypropylene (PP), increasing the products biodegradability (Evangelista et al, 1991 Bagheri, 1999). 

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