Project Title: Poly(vinyl chloride) Bioplasticizers
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:

Plastics are very heavily used in our global society. They are used in just about every industry—packaging, construction, and medical equipment are only a few examples. Plastics are easy to produce, cheap and very useful. The problem? They are not being recycled efficiently—resulting in buildup in landfills—and the majority of plastics are non-biodegradable. The disposal of non-biodegradable plastics is particularly harmful to wildlife, as they are often mistook for food and ingested. Our focus for this project was poly(vinyl chloride) (PVC) plastics because their plasticizers (chemicals added to plastics to give them specific properties) are non-biodegradable and pose potential environmental and health risks through leaching, making them harmful in terms of production, use and disposal.

Can dangerous, non-biodegradable poly(vinyl chloride) plasticizers be replaced by safer organic alternatives?

In our experiment, we focused on the common primary PVC plasticizer di(2-ethylhexyl) phthalate. It has been identified to be a reproductive toxicant and endocrine disruptive agent, and it is found in our water supply, aquatic environments and the atmosphere. Furthermore, PVC plastics that contain this plasticizer are non-biodegradable.

We replaced DEHP with peanut oil, sunflower oil, safflower oil and propylene glycol. The vegetable oils are samples of possible organic and natural vegetable oil plasticizers, and propylene glycol a biodegradable but synthetically produced one. After making PVC film sheets by dissolving the monomer vinyl chloride in a dicholoromethane solution and mixing in 10, 20, 30 and 40% by-weight ratios of plasticizer, we tested for clarity, flexibility and compression of the plastic films. For clarity, a spectrophotometer was used to record the amount of light absorbed at the 450nm wavelength. A micrometer was used to test the compressibility of film samples by the application of constant pressure. For flexibility, an apparatus was built that involved a zeta-meter to measure the deflection of samples under gravitational force from 0.25mg of water. Then by using the formula for flexural stress, the elastic modulus for each plastic sample was calculated. While it was hardly surprising that DEHP should have the best overall performance in the four tests we performed, we were pleasantly surprised by how effective safflower oil was. Safflower oil was closest out of the four alternatives in matching DEHP’s performance in all tests.

We find the results very encouraging, as safflower oil now poses as a potential organic plasticizer for PVC plastics. It is cheap, accessible, safe for human use, and environmentally friendly. If safflower oil were used as the plastic’s primary plasticizer, this would increase the plastic’s biodegradability, and also safety in the areas of production, use, and disposal. While safflower oil was definitely the best performer of the plasticizer alternatives tested in this experiment, we must caution not to completely disregard the other plasticizers tested. Sunflower oil, for instance, also showed a significant amount of promise as a potential PVC primary plasticizer. The plasticizers that showed different properties could be used in products other than PVC where properties such as flexibility or elasticity need not be so great.