Lesson 2: Green Plastics and 12 Principles of Green Chemistry

12 Principles of Green Chemistry:

1. It is better to prevent waste than to treat or clean up waste after it is formed

2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product

3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment

4. Chemical products should be designed to preserve efficacy of function while reducing toxicity

5. The use of auxiliary substances should be made unnecessary whenever possible and innocuous when used

6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure

7. A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable

8. Reduce derivatives – Minimize or avoid unnecessary derivatization if possible, which required additional reagents and generates waste

9. Catalytic reagents are superior to stiochiometric reagents

10. Chemical products should be designed so at the end of their function they do not persist in the environment and break down into innocuous degradation products

11. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances

12. Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions and fires

Formation of Plastics:

– By either addition polymerisation or condensation polymerisation

Pros and Cons of Bioplastic

Pros:

  • reduces or eliminates Greenhouse Gases in production
  • requires less or no petrochemicals
  • biodegradable
  • can be utilized as fuel
  • slow release of Carbon Dioxide allows sufficient time for plants to absorb Carbon Dioxide

Cons:

  • cost
  • use of fertilizer and pesticides for crops
  • release ethane gas

Problems with Conventional Plastic

  • complex entanglements of polymer chains make it hard to decompose
  • rely heavily on petrochemicals
  • needs processing
  • recycling is energy-consuming and costly
  • releases toxic chemicals
  • non-biodegradable

Production of Bioplastic from Milk and Vinegar

Procedure:

  1. Mix 100 ml of milk and 20 ml of vinegar in a beaker
  2. Heat up the mixture until 50-60 degree Celsius   15067_732022160148045_2085284890_n
  3. Pour the milk through a filter funnel lined with filter paper 1231562_732022190148042_1082352354_n
  4. Residue on the filter paper can be molded into any shape and will harden when driedphoto (1)

Concept behind experiment:

Milk contains many molecules of a protein called casein. Casein is negatively charged so casein molecules repel each other and don’t stick together. When hot milk and vinegar are added together, the casein molecules unfold and reorganize into a long chain. Vinegar is an acid which means it contains many positively charged H+ ions which will neutralise the negative charges and lower the pH such that the casein molecules attract one another and become curdles. This allows the protein particles to come together and form a big sticky network. The casein in milk does not mix with the acid and so it forms the white precipitate (curds) seen in the residue. Each casein molecule is a monomer and the polymer made is made up of many of those casein monomers hooked together in a repeating pattern.

Sources:

http://www.sciencebob.com/experiments/plasticmilk.php

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p101.shtml#background

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