Petroleum-derived synthetic plastics

Polyhydroxyalkanoate(s) (PHA) are one of the potential environmentally friendly alternatives to petroleum-derived synthetic plastic. Their biodegradahility and production from renewable resources make them extremely desirable substitutes for synthetic plastics. However, the use of PHA as a substitute is hindered by the overall manufacturing cost, which is far more expensive than the manufacture of non-biodegradable synthetic plastics. 

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). 

Another significant trend is the current program to increase the production of benzene from petroleum 16). Increasing requirements for the production of styrene, phenol, and other intermediates have made it essential that new sources be found to supplement current supplies of this aromatic hydrocarbon, and the only apparent source is from petroleum processes. To meet current needs of the military and civilian program the United States Petroleum Administration for Defense has been asked to increase petroleum benzene from the current rate of 12,000,000 gallons to 100,000,000 gallons per year 84). Present production from petroleum is small in comparison with that from other sources, but these proposed expansions may add materially to the output of petroleum-derived intermediates that will ultimately go to the manufacture of plastics and synthetic rubber. 

Compression-molded soy protein plastics are rigid and brittle without plasticizers present in the formulation (Paetau et al., 1994). Water absorption of early protein plastics could not be reduced to the very low levels that were obtained with synthetic, petroleum-derived resin products however, color, dyeing, and strength properties were good and production costs were relatively low (Johnson Myers, 1995). 

A composite material is a two-phase or multiphase compact material with its components (phases) separated by interfaces which can be formed naturally or be manmade. One of the composite material phases is the matrix (phase I). It exists in the solid (crystalline or amorphous) state of aggregation. Within the matrix, particles are distributed discretely. This is phase II or disperse phase [23]. Biocomposites are composite materials made from natural fiber and petroleum-derived nonbiodegradable polymers like PP, PE, and epoxies or biopolymers like poly lactic acid (PLA), cellulose esters. Composite materials derived from biopolymer and synthetic fibers such as glass and carbon come under biocomposites. Biocomposites derived from plant-derived fiber (natural/biofi-ber) and crop/bioderived plastics (biopolymer/bioplastic) are likely more ecofriendly, and such biocomposites are sometimes termed green composites [24]. 

Petroleum is a thick, viscous hquid mixture of literally thousands of compounds, most of them hydrocarbons, formed from the decomposition of marine plants and animals. Petroleum and petroleum-derived products fuel automobiles, aircraft, and trains. They provide most of the greases and lubricants required for the machinery of our highly industrialized society. Furthermore, petroleum, along with natural gas, provides close to 90% of the organic raw materials used in the synthesis and manufacture of synthetic fibers, plastics, detergents, drugs, dyes, and a multitude of other products. 

Starch can be used as a biodegradable additive or replacement material in traditional oil-based commodity plastics. If starch is added to petroleum-derived polymers (e.g., PE), it faciUtates disintegration of the blend, but not necessarily biodegradation of the polyethylene component Starch accelerates the disintegration or fragmentation of the synthetic polymer structure. Microbial action consumes the starch, thereby creating pores in the material that weaken it and enable it to break apart... 

Cyclic Hydrocarbons. The cyclic hydrocarbon intermediates are derived principally from petroleum and natural gas, though small amounts are derived from coal. Most cycHc intermediates are used in the manufacture of more advanced synthetic organic chemicals and finished products such as dyes, medicinal chemicals, elastomers, pesticides, and plastics and resins. Table 6 details the production and sales of cycHc intermediates in 1991. Benzene (qv) is the largest volume aromatic compound used in the chemical industry. It is extracted from catalytic reformates in refineries, and is produced by the dealkylation of toluene (qv) (see also BTX Processing). 

Until the end of World War II, coal tar was the main source of these aromatic chemicals. However, the enormously increased demands by the rapidly expanding plastics and synthetic-fiber industries have greatly outstripped the potential supply from coal carbonization. This situation was exacerbated by the cessation of the manufacture in Europe of town gas from coal in the eady 1970s, a process carried out preponderantly in the continuous vertical retorts (CVRs), which has led to production from petroleum. Over 90% of the world production of aromatic chemicals in the 1990s is derived from the petrochemical industry, whereas coal tar is chiefly a source of anticorrosion coatings, wood preservatives, feedstocks for carbon-black manufacture, and binders for road surfacings and electrodes. 

Petrochemicals in general are compounds and polymers derived directly or indirectly from petroleum and used in the chemical market. Among the major petrochemical products are plastics, synthetic fibers, synthetic ruhher, detergents, and nitrogen fertilizers. Many other important chemical industries such as paints, adhesives, aerosols, insecticides, and pharmaceuticals may involve one or more petrochemical products within their manufacturing steps. 

Most of the plastics and synthetic polymers that are used worldwide are produced from petrochemicals. Replacing petroleum-based feedstocks with materials derived from renewable resources is an attractive prospect for manufacturers of polymers and plastics, since the production of such polymers does not depend on the limited supply of fossil fuels [16]. Furthermore, synthetic materials are very persistent in the environment long after their intended use, and as a result their total volume in landfills is giving rise to serious waste management problems. In 1992,20% of the volume and 8% of the weight of landfills in the US were plastic materials, while the annual disposal of plastics both in the US and EC has risen to over 10 million tons [17]. Because of the biodegradability of PHAs, they would be mostly composted and as such would be very valuable in reducing the amount of plastic waste. 

Modem civilization consumes vast quantities of organic compounds. Coal, petroleum, and natural gas are primary sources of carbon compounds for use in production of energy and as starting materials for the preparation of plastics, synthetic fibers, dyes, agricultural chemicals, pesticides, fertilizers, detergents, rubbers and other elastomers, paints and other surface coatings, medicines and drugs, perfumes and flavors, antioxidants and other preservatives, as well as asphalts, lubricants, and solvents that are derived from petroleum. 

The fuels that are derived from petroleum supply more than half of the world s total supply of energy. Gasoline, kerosene, and diesel oil provide fuel for automobiles, tractors, tmcks, aircraft, and ships. Fuel oil and natural gas are used to heat homes and commercial buildings, as well as to generate electricity. Petroleum products are the basic materials used for the manufacture of synthetic fibers for clothing and in plastics, paints, fertilizers, insecticides, soaps, and synthetic rubber. The uses of petroleum as a source of raw material in manufacturing are central to the functioning of modem industry. 

It is a fact of modern society that many ordinary items of everyday use are obtained from complex chemical processes. Life-saving drugs, capsules and tablets, as well as perfumes, are derived from coal. From crude oil and petroleum gases, we obtain fertilisers, plastics, synthetic rubbers, pesticides, detergents, fabrics and coatings and paints. From seawater we can produce vital heavy chemicals including caustic soda, sodium chloride, sodium hydroxide, hydrochloric acid and so on. 

Before advent of cheap petroleum, many natural polymers were being used or being studied for use in plastics. Since then, synthetic polymers have dominated the marketplace. It should be possible to make the plastics that we need from cellulose, hemicellulose, starch, chitin, lignin, proteins, or other natural products.69 Ideally, the plastic or other product should have properties similar to or better than the one derived from petroleum that it is to replace. It should not require more energy to make or cost more. 

The first plastic made was cellulose nitrate, which is a derivative of cellulose, obtained from wood pulp. The first truly synthetic polymer material was phenolic resin, which was synthesized from phenol and formaldehyde derived from coal. Today, the source of organic chemicals for the production of polymers has shifted from these traditional sources to petroleum and natural gas. Petroleum as a raw material for organic chemicals (petrochemicals) is relatively cheap, readily available in large tonnages, and more easily processed than the other main source of organic chemicals — coal. 

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