POLYMERS A long chain molecule made of repeat units called “mers” The first purely engineered material starting from simple chemicals like ethylene and propylene Traditionally a “polymer” is the pure primary material and a “plastic” is a polymer plus additives to improve its properties What are properties we associate with plastics?

THE AGE OF PLASTICS Polymers (plastics) differ in general from metals and ceramics by being: –Less in hardness –Less in strength –Less in temperature stability –Less in reactivity (than most metals) –Greater in %elongation –Greater in terms of being customized –Greater in terms of ease of processing –Less in density (generally a positive trait)

FIRST POLYMERS Bitumen Silk Rubber –Coagulate tree sap of hheve Tree from Haiti –Wore on feet –Early 1700’s back to France –1820 (1 st ) Macintosh Mix rubber and naptha Raincoats Sticky or brittle

WHAT IS A PLOYMER? C-C Ethane C=C Ethylene C-C-C PropaneC=C-C Propylen -C-C- polymerize What are the side groups? –H Polyethylene (PE) HDPE milk containers –Cl Poly vinyl chloride (PVC) Piping –CH3 Polypropylene (PP) Polypro clothing –Benzene Polystyrene (PS) Styrofoam –Fluorine (PTFE) Teflon Side group affect crystallization and thus properties

RUBBER AND CROSS-LINKING Rubber has a double bond in the backbone -C=C-C- This is critical Charles Goodyear 1830’s –How to make rubber less sticky and hold shape better –Used Sulfur to cross-link chains –Huge improvement Rubber became a critical material in transportation Supply issues in WW I and WW II led to synthetic rubber

INSTIGATORS OF THE PLASTIC AGE Charles Goodyear Better inventor than entrepreneur In and out of debt most of his life Felt a calling (spiritual) to improving the qualities of rubber Invented vulcanization of rubber Process involves sulfur and heat Produces material that is consistently tough, elastic, and stable with temperature.

CELLULOSE NITRATE 1868 Phelan and Collender –Billiard ball challenge $10K prize to replace Ivory –1846 Schonbein Univ of Basil –Dissolve paper in nitric and sulfuric acid –Made cellulose nitrate –Parkes in GB softened with camphor –Hyatt bade billiard balls Problem in synthesis replace Oh in cellulose with NO3 from nitric acid Explosive –1890 Chadonnet replaces nitrate with xanthate Invents first synthetic fiber Rayon

FIRST SYNTHETIC POLYMERS Not based on natural products 1930’s Fawcett and Gibson accidently polymerize ethylene Critical material in WW II for radar –Standard insulation for all radar cables Problem was side branching Variable properties Pile up of unused PE Ziegler Natta Catalysts invented in early 1950’s –Linear PE 100,000 mers –80% crystalline, HDPE Ziegler –Linear PP Natta

TUPPERWARE The composition of tupperware is either low density polyethylene (LDPE) or polypropylene (PP) allorca1999/forum1.html

LOW DENSITY POLYETHYLENE LDPE is defined by a density range of 0.910–0.940 g/cm 3 LDPE has a high degree of short and long chain branching This means the chains do not pack into the crystal structure as well as for example the very long chain high density polyethylene.crystal structure This results in a lower tensile strength and increased ductility.tensile strength ductility LDPE is used for both rigid containers and plastic film applications such as plastic bags and film wrap. In 2009 the global LDPE market was $22.2 billion Wikipedia

POLYPROPYLENE The density of polypropylene varies from g/cm3 Most commercial polypropylene is isotactic (the methyl groups are all on the same side)isotactic It has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high- density polyethylene (HDPE).crystallinitypolyethyleneLDPEHDPE Polypropylene is normally tough and flexible. Polypropylene is reasonably economical, and can be made translucenttranslucent Applications include clothing, carpeting, medical devices, rope, car batteries, wastebaskets, pharmacy prescription bottles etc. In 2009 the global PP market was ~$61billion

DUPONT Plunkett 1930”s –Accidently discovers Teflon –Kept secret until after war Carothers –C-C-C=0 (OH) + C-C-C=N (H) –Reaction condenses water –Created Nylon –Make and stretch Nylon

INSTIGATORS OF THE PLASTICS AGE Wallace Carothers Professor of Organic Chemistry –U. Illinois, Harvard DuPont Director of R&D Developed Nylon & Neoprene Lodged 50 patents Hated public speaking. Suffered from chronic depression. Frequently consumed alcohol to calm his nerves. Following the death of his sister and estrangement from his parents and wife of only 3 years, Carothers committed suicide at age 41 by ingesting cyanide dissolved in lemon juice.

THERMOSETS VS THERMPLASTICS Simpliest terms –Thermoplastics can be melted Most plastics in everyday life are thermoplastics 2 liter bottles can be melted down and reused –Thermosets are sufficiently cross-linked to prevent them from being melted Makes it difficult to reuse them again for the same purpose E.g. car tires can be ground up and reused but not melted down and reused

The appearance of a polymer occurs in ~800 AD with the use of gutta percha (a natural rubber). Ashby “Materials and the Environment” THE AGE OF PLASTICS

Summary THE AGE OF PLASTICS In the developmental history of materials, the age of plastics is less than 100 years old. The paradigm shift that occurred in this age involves man’s ability to synthesize new materials. Ashby “Materials and the Environment”

THE AGE OF PLASTICS Today, polymeric materials are produced in quantities rivaling all other materials. Ashby “Materials and the Environment”

Packaging represents the largest single use of plastics. Use is derived from weight, flexibility and sealing qualities.

PLASTIC Challenges The world consumes 100 million tonnes of plastic materials million tonnes in Europe, 5 million tonnes in the UK - and growing at 3 to 4 percent each year The amount of plastic wastes generated annually in the UK was estimated at 3 million tonnes in Although all types of plastics could be recycled, only 7 percent actually were. PVC, polyvinyl chloride, is the second most commonly used plastic in the world, and causes the most problems for health and the environment. It is the largest source of dioxin when burnt in incinerators and in accidental fires in buildings. The production of PVC involves transporting dangerous explosive materials such as vinyl chloride monomer (a carcinogen), and creating toxic wastes, notably ethylene dichloride tars.

THE PLASTIC BAG Compared to paper grocery bags, plastic grocery bags consume 40 percent less energy, generate 80 percent less solid waste, produce 70 percent fewer atmospheric emissions, and release up to 94 percent fewer waterborne wastes, according to the federation. According to Cobb's calculations extrapolated from data released by the United States Environmental Protection Agency in 2001 on U.S. plastic bag, sack, and wrap consumption, somewhere between 500 billion and a trillion plastic bags are consumed worldwide each year. In a landfill, single-use bags will take up to 1,000 years to degrade.

THE AGE OF PLASTICS The age of plastics has ushered in a heavy reliance on materials that are considered non-renewable. With the growing world population, this places enormous pressure on our natural resources. Ashby “Materials and the Environment”