Blending with Biodegradable Polymers

Poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) or poly(ethylene succinate) (PES) are flexible biodegradable polyesters that have also been considered for blending with PLA. PBAT and PLA are immiscible polymers where PBAT phase formed small droplets in the PLA matrix. Drastic increase of elongation at break was observed (200% with only 5 wt% of PBAT) due to interfacial debonding mechanisms as the interfacial adhesion between the two polymers was low. The impact 

PLA blending with other biodegradable polymers leads to interesting mechanical properties. Nevertheless, the use of non-biodegradable or biocompatible compatibilizers is often required in order to optimize these properties. 

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Wang X.L., Yang K.K., Wang Y.Z., Properties of starch blends with biodegradable polymers, J. Macromol. Sci, Part C, C43, 2003, 385-409. 

Polymer blends, particularly olefins with biodegradable polymers, are gaining popularity as an approach to degradable packaging plastics. The materials are at best only partially biodegraded, but will lose form and bulk as the plastic disintegrates. This may be sufficient in landfill as volume diminishes, leaving room... 

Blending, Grafting and Copolymerisation with Biodegradable Polymers and Additives... 

A wide range of thermoplastic starch compounds have been claimed in recent years. Formulations of thermoplastic starch with linear, biodegradable polyesters, including polycaprolactone and PHBV,174 176 and with polyamides175 have been reported. Laminated structures have been claimed using thermoplastic starch or starch blends as one or more of the layers.175,177,178 The use of polymers latexes as components of thermoplastic starch blends has also been claimed.179 181 Blends with natural polymers are also claimed, including cellulose esters182,183 and pectin.184 A crosslinked thermoplastic material of dialdehyde starch and protein has been reported.185... 

Blends of poly(3-hydroxyalkanoic acid)s (PHAs) with various natural and synthetic polymers have been reported as reviewed in Refs. [21,22]. By blending with synthetic polymers it is expected to control the biodegradability, to improve several properties, and to reduce the production cost of bacterially synthesized PHAs. The polymers investigated as the blending partners of PHAs include poly(ethylene oxide) [92, 93], poly(vinyl acetate) [94], poly(vinylidene fluoride) [95], ethylene propylene rubber [94, 96], po-ly(epichlorohydrin) [97, 98], poly(e-caprolactone) [99], aliphatic copolyesters of adipic acid/ethylene glycole/lactic acid [100] and of e-caprolactone/lactide... 

Cellulose blends with synthetic polymers also constitute an example of biodegradable polymer blends. Miscibility of cellulose with polyvinylpyrrolidone [Masson and Manley, 1991a], poly(4-vinyl pyridine) [Mason and Manley, 1991b], PAN [Nishio et al, 1987], PVAL [Nishio and Manley, 1988], and polyethyleneoxide (PEG) [Nishio et al., 1989] have been reported. Starch blends with commodity polymers have been commercialized as a low cost method to promote partial environmental degradability. While a defi-... 

However, in addition to their thermoplasticity, representatives of PHAs have optical activity, increase induction period of oxidation, exhibit the piezoelectric effect and, what is most important, they are characterized as being biodegradable and biocompatible. At the same time, the PHAs have disadvantages (high cost, brittleness), which can be partially or completely compensated by using composite materials based on blends with other polymers, with dispersed fillers or plasticizers. Taking into account all the above, we have suggested to create a mixed polymer composite based on poly-3-hydroxybutyrate (PHB) and polyisobutylene (PIB). 

Thermoplastic starch is also blended with other polymers to improve its properties for particular applications. For example, a bag for collection of household food waste for composting that readily dissolved when it got wet would not function very well In applications such as this, the resins used for blending are also biodegradable, so that they do not interfere with the composting operation. In other cases, starch is blended with nonbiodegradable resins such as polyolefins. 

Numerous non-biodegradable blends with synthetic polymers [ARV 99, STP 97], such as polyolefins, have been commercialized. As is currently the case for oxo-degradable polymers, these blends have, in the past, caused great controversy, because they were falsely presented as being biodegradable. Sometimes, the term biofragmentable was apphed to these substances. 

Due to the poor mechanical properties and instability of native starches, it is frequently reinforced with fibers [134—136] or blended with synthetic polymers [137-140]. Recently, much emphasis has been put on blending starch with biodegradable polyesters like PLA [141, 142], PCL [120, 143-145] and PBS [143, 144]. The injection conditions depend on the polyesters incorporated generally, blending with these synthetic polymers decrease the overall viscosity of starch. 

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. 

Blending and compositing have been successfully used in starch-based materials. Starch was initially used a fillers blended with various polymers, especially with polyolefin. Blending starch with biodegradable polymers has attracted more and more attention. The interest in new nanoscale fillers has rapidly grown since it was discovered that a nanostructure could be built from a polymer and a layered nanoclay. These new nanocomposites show dramatic improvement in mechanical properties with low filler content. Cellulose is the major substance obtained from vegetable fibers, and applications for cellulose fiber-reinforced polymers have again come to the forefront with the focus on renewable feedstocks. Hydrophilic cellulose fibers are very compatible with most natural polymers. 

In recent ten years, xylans and mannans have been studied as potential raw materials for biodegradable films. Sometimes they are blended with other polymers or mixed with nanoparticles to achieve enhanced properties. This chapter covers the occurrence, structure and properties of xylans and mannans as well as recent smdies on xylan- and mannan-based blends, composites, and nanocomposites. 

PLA can also be blended with other polymers. BASF has introduced Ecovio, a polymer blend of 55% of BASF s biodegradable polyester Ecoflex and 45% PLA, in the market very successfully and has started a major investment to increase both Ecoflex and Ecovio capacities at its Ludwigshafen site in Germany in early 2009 [8]. 

Blends of biodegradable polymers with synthetic non-degradable polymers... 

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