Environmental impact—plastics

Nature of science:

Risks and problems—scientific research often proceeds with perceived benefits in mind, but the risks and implications also need to be considered. (4.8)

• Plastics do not degrade easily because of their strong covalent bonds.
• Burning of polyvinyl chloride releases dioxins, HCl gas and incomplete hydrocarbon combustion products.
• Dioxins contain unsaturated six-member heterocyclic rings with two oxygen atoms, usually in positions 1 and 4.
• Chlorinated dioxins are hormone disrupting, leading to cellular and genetic damage.
• Plastics require more processing to be recycled than other materials.
• Plastics are recycled based on different resin types.

Applications and skills:

• Deduction of the equation for any given combustion reaction.
• Discussion of why the recycling of polymers is an energy intensive process.
• Discussion of the environmental impact of the use of plastics.
• Comparison of the structures of polychlorinated biphenyls (PCBs) and dioxins.
• Discussion of the health concerns of using volatile plasticizers in polymer production.
• Distinguish possible Resin Identification Codes (RICs) of plastics from an IR spectrum.

• The international symbol for recycle, reuse and reduce is a Mobius strip designed in the late 1960s. However, global recognition of this symbol ranks well below other symbols. What factors influence the recognition of symbols?
• How can nations address the problem of the plastic gyre in the Pacific Ocean?

Theory of knowledge:

• The products of science and technology can have a negative impact on the environment. Are scientists ethically responsible for the impact of their products?

Utilization:

• Syllabus and cross-curricular links:
• Topic 9.1—redox reactions
• Topic 10.1—organic compounds
• Topic 11.3—infrared spectroscopy
• Biology option C.3—impact of humans on ecosystems

Aims:

• Aim 7: Database of RIC codes and IR spectra can be used.
• Aim 8: The development of green chemistry has raised the awareness of the environmental and the ethical implications of using science and technology.

• Dioxins do not decompose in the environment and can be passed on in the food chain.
• Consider polychlorinated dibenzodioxins (PCDD) and PCBs as examples of carcinogenic chlorinated dioxins or dioxin-like substances.
• Consider phthalate esters as examples of plasticizers.
• House fires can release many toxins due to plastics (shower curtains, etc). Low smoke zero halogen cabling is often used in wiring to prevent these hazards.
• Resin Identification Codes (RICs) are in the data booklet in section 30.
• Structures of various materials molecules are in the data booklet in section 31.