Chemistry Science Fair Project
Organic alternatives to the PVC plasticizer DEHP

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Title: Test if the PVC plasticizer DEHP can be replaced by organic alternatives that do not significantly compromise plastic performance in the areas of dimension change, glass transition temperature, and extraction resistance.
Subject: Chemistry
Grade level: High School - Grades 10-12
Academic Level: Ordinary
Project Type: Experimental
Cost: Medium
Awards: 2nd place, Canada Wide Virtual Science Fair (2007)
Affiliation: Canada Wide Virtual Science Fair (VSF)
Year: 2007
Description: This study attempts to find safe, biodegradable and high-performance DEHP alternatives. Two synthetic diblock copolymers were tested, along with epoxidized Carthamus tinctorius oil (ECTO), which was synthesized via a chemo-enzymatic reaction. PVC films with these alternatives were cast, and performance tests of dimension change, glass transition temperature, and extraction resistance were conducted. Although the diblocks were of slightly lower performance than DEHP, ECTO was of higher. At 10% concentration, films with ECTO were twice as flexible. Our results show that a lesser amount of ECTO, a more environmentally friendly substance, not only achieves better plasticizing effects than DEHP, but is also an effective heat stabilizer. ECTO can be used in applications requiring a hydrophobic plasticizer; the two diblocks can be used in hydrophilic applications.

Bis(2-ethylhexyl)phthalate, commonly abbreviated DEHP, is an organic compound with the formula C6H4(CO2C8H17)2. It is the most important "phthalate," being the diester of phthalic acid and the branched-chain 2-ethylhexanol. This colourless viscous liquid is soluble in oil, but not in water. It possesses good plasticizing properties. Being produced on a massive scale by many companies, it has acquired many names and acronymns, including BEHP, di-2-ethyl hexyl phthalate, as well as dioctyl phthalate (DOP).

Due to its suitable properties and the low cost, DEHP is widely used as a plasticizer in manufacturing of articles made of PVC. Plastics may contain 1% to 40% of DEHP. It is also used as a hydraulic fluid and as a dielectric fluid in capacitors. DEHP also finds use as a solvent in lightsticks.

DEHP has a low vapor pressure, but the temperatures for processing PVC articles are often high, leading to release of elevated levels, raising concerns about health risks (see outgassing). It can be absorbed from food and water. Higher levels have been found in milk and cheese. It can also leach into a liquid that comes in contact with the plastic; it extracts faster into nonpolar solvents (eg. oils and fats in foods packed in PVC). Food and Drug Administration (FDA) therefore permits use of DEHP-containing packaging only for foods that primarily contain water. In soil, DEHP contamination moves very slowly because of its low solubility in water. Therefore, leaching from disposed plastics in landfills is generally slow. The US EPA limits for DEHP in drinking water is 6 ppb. The U.S. agency OSHA's limit for occupational exposure is 5 mg/m3 of air.

Plasticizers are additives that increase the plasticity or fluidity of the material to which they are added, these include plastics, cement, concrete, wallboard and clay bodies. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different.

The plasticizers for plastics soften the final product increasing its flexibility.

Plasticizers for plastics are additives, most commonly phthalates, that give hard plastics like PVC the desired flexibility and durability. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing of the "free volume"), and thus significantly lowering the glass transition temperature for the plastic and making it softer. For plastics such as PVC, the more plasticiser added, the lower its cold flex temperature will be. This means that it will be more flexible, though its strength and hardness will decrease as a result of it. Some plasticizers evaporate and tend to concentrate in an enclosed space; the "new car smell" is caused mostly by plasticizers evaporating from the car interior.

Source: Wikipedia (All text is available under the terms of the Creative Commons Attribution-ShareAlike License)

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