Petroleum-based plastics Poly

Generally speaking, bio-based plastics include starch-based plastics, protein (soybean protein) based plastics, and cellulose-blended plastics. They can also be blended with conventional plastics such as polyethylene (PE), polypropylene (PP), and poly(vinyl alcohol). However, such bio-based plastics are only partially biodegradable. The residual petroleum-based plastics remain as broken pieces, creating additional pollution. In addition, these plastics have intrinsic thermal and mechanical weaknesses, and they are now discouraged for applications. 

Back to Nature is the solution then Looking at a few numbers in Table 4.7 may prevent hasty judgments reading this questioa About 50 million t of plastics are produced in Europe each year from petroleum. The production of natural polymers is about 0.1% percent of this total virtually all of which is poly lactic acid. These numbers are not promising it would be lunacy to expect that polylactic acid (Fig. 4.30) or any other semi-synthetic and biodegradable polymer could replace petroleum-based plastics in any foreseeable future. 

Irrigation pipes are conventionally made from non biodegradable petroleum-based plastics such as poly(ethylene) or poly(propylene) (PP). As a result, conventional irrigation pipes that are discarded are generally not readily recycled into the environment and add to pollution stress of the environment. In addition, because petroleum is a non-renewable raw material, it is expected that raw material costs for producing irrigation pipes from petroleum-based plastics will increase (7). 

A continuous increase in oil prices and environmental concerns about the use of common petroleum-based plastics have recently led to a growing interest in bio-based plastics. Poly(lactic acid) (PLA), a plastic derived from fermented plant starch, is fast becoming one of the popular alternatives to traditional petroleum-based plastics. Even though PLA has been known for more than a century, it has only been used commercially in recent years in a number of biocompatible/ bioabsorbable biomedical device market, packaging applications, and so on. A number of factors contribute to the success of PLA in these applications, including its physical properties as well as favorable compostable and degradation characteristics [1]. 

Poly(L-lactide) (PLLA) is a biodegradable aliphatic polyester produced by ring-opening polymerization of lactide (i.e., with cyclic dimer of lactic acid) or by polycondensation of lactic acid. Although PLLA is a synthetic polymer, it is considered a renewable and bio-based plastic because its raw material lactic acid is synthesized from biomass or renewable resources such as sugars and starch. PLLA has some properties that are similar to some petroleum-based plastics, thereby making it suitable for a variety of applications in the medical, textile, and packaging industries. 

In 2002, the world production of polymers (not including synthetic libers and rubbers) was ca. 190 million metric tons. Of these, the combined production of poly(ethylene terephthalate), low- and high-density polyethyelene, polypropylene, poly(vinyl chloride), polystyrene, and polyurethane was 152.3 milhon metric tons [1]. These synthetic, petroleum-based polymers are used, inter alia, as engineering plastics, for packing, in the construction-, car-, truck- and food-industry. They are chemically very stable, and can be processed by injection molding, and by extrusion from the melt in a variety of forms. These attractive features, however, are associated with two main problems ... 

Extrusion is a cost effective manufacturing process. Extrusion is popularly used in large scale production of food, plastics and composite materials. Most widely used thermoplastics are processed by extrusion method. Many biopolymers and their composite materials with petroleum-based polymers can also be extruded. These include pectin/starch/poly(vinyl alcohol) (Fishman et al. 2004), poly(lactic acid)/sugar beet pulp (Liu et al. 2005c), and starch/poly(hydroxyl ester ether) (Otey et al. 1980), etc. In this study, composite films of pectin, soybean flour protein and an edible synthetic hydrocolloid, poly(ethylene oxide), were extruded using a twin-screw extruder, palletized and then processed into films by compression molding process or blown film extrusion. The films were analyzed for mechanical and structural properties, as well as antimicrobial activity. 

H., and Harrison, S.T.L. (2007) Environmental analysis of plastic production processes comparing petroleum-based polypropylene and polyethylene with biologically-based poly-P-hydroxybutyric add using life cyde analysis./. Biotechnol, 130 (1), 57-66. 

Recently, the possibility of replacing petroleum-derived synthetic polymers with natural, abundant and low-cost biodegradable products has gained much interest in both academic and industrial fields. " For instance, the production of plastics in Europe reached 57 million tons in 2012, mostly divided between polyethylene, polypropylene, poly(vinyl chloride), polystyrene and poly(ethylene terephthalate) production. These fossil-based plastics were consumed and discarded into the environment, generating 10.4 million tons of plastic waste, most of which ended up in landfills (Figure 1). 

The majority of petroleum-based compostable plastics belong to the polyester family, including Ecoflex , polycaprolactone (PCL), Ecovio , poly-butyrate adipate terephthalate (PBAT), and aliphatic copolyesters (The Impacts of Degradable Plastic Bags in Australia 2003). Table 4.14 lists several commercially available biodegradable or compostable plastic products. 

Poly(lactic acid) (PLA) is known to be biocompatible and biodegradable, and it can be readily broken down by a hydrolysis reaction. PLA is derived from renewable agricultural resources, such as com and cassava. Mass production of PLA can lead to high consumption of agricultural yields, which increases the farm economy. Moreover, the production of PLA helps to reduce CO2 emissions when used in place of conventional petroleum-based commodity plastics, as the agrieultural activities involve significant carbon fixation. 

Polymerization of a-hydroxycarboxylic acids, glycerol, 1,3-propanediol, and amino acids, either individually or as copol)oners, can generate commercially viable polymers [2]. Other researchers have shown that renewable-resource polymers, such as poly(lactic acid) and others, can be viably produced and these materials are currently on the market for biomedical and packaging apphcations [4,5]. Our goal is to develop low-cost bioplastics with comparable or even enhanced physical and chemical properties versus petroleum-based conunodity plastics. 

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