Project Title: Poly(vinyl chloride) Bioplasticizers II
Experimenters: Robyn Thom and Thomas Sun

School: Sir Winston Churchill Secondary
Grade Category: 10-12
Team Size: 2
Subject Area: Earth/Energy/Environmental Sciences
Project Type: Experimental
Language: English
Software Used: Microsoft Frontpage, Adobe Photoshop
Hardware Used: Digital Camera, Scanner
Language: Website written in HTML

Abstract:
Poly(vinyl chloride) (PVC) is among the top three most widely used plastics globally. Construction, medical devices, and automobile parts are only a few of the sectors that make extensive use of PVC. A phthalate ester, di(2-ethylhexyl) phthalate (DEHP), is often added as a plasticizer by as much as 40% by weight to impart flexibility.

However, DEHP, a known toxin and carcinogen, leaches into the atmosphere, causing severe environmental contamination, impacting wildlife, aquatic species and human health. An environmental assessment was done on the degree of DEHP contamination in local soil and water samples. Our experimentation on the release behaviour of DEHP confirmed that it leaches out of the PVC polymer matrix rapidly. 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.          

We hope that our findings can resolve the prevalent DEHP contamination problem by going to the source of the problem: to replace the chemical altogether.