Plastics & Polymers

Atoms are the building blocks of chemical elements. Molecules contain atoms bonded together. A polymer is a large molecule made from many repeating units. A monomer is a small molecule that can participate in forming a polymer. Not every polymer is a manufactured plastic: proteins and cellulose are examples of naturally occurring polymers.

In addition polymerisation, suitable unsaturated monomers join without producing a small-molecule by-product. Ethene has a carbon–carbon double bond; its polymer is poly(ethene), with repeating –CH₂–CH₂– units. The double bond is changed as units link, and the atoms must still be accounted for. The drawn repeat unit is not a whole finished molecule.

The hall’s bead chain is an analogy for repeating units, not a scale drawing of bonding or a recipe for chemical synthesis. Chain length, composition and arrangement influence properties. Use paper diagrams only; never melt, burn or chemically process plastics for this lesson.

Thermoplastics generally soften when heated and can be reshaped under appropriate processing conditions. Their chains are not joined into the same permanent extensive network characteristic of a cured thermoset. Thermosets have cross-linked structures and do not simply remelt like thermoplastics; strong heating can cause decomposition.

Chain interactions, cross-links, crystallinity and additives affect stiffness, temperature response and toughness. A flexible polymer is not necessarily weak in every sense. Reinforcement can change performance but also complicate processing or recycling. The material name alone may not specify the properties of a particular product formulation.

Choose a material according to the required service conditions. A kitchen handle, packaging film and electrical insulation have different demands. Avoid treating “plastic” as one substance. Compare evidence for named properties while keeping real product safety and processing under professional control.

A formulation specifies the proportions of its components. Percentages are shares of a whole; they must be interpreted consistently by mass, volume or another basis. A classroom batch described as 10% additive by mass has additive mass equal to 0.10 times total batch mass. Do not confuse 10% of the total with 10% added on top of the original polymer mass.

Moulding forms some materials into shapes, but temperature, pressure and time depend on the material and method. Cooling, shrinkage and tolerances matter. The classroom can analyse a fictional process diagram without giving real processing instructions. GE’s former Plastics business history is separate from general polymer chemistry and from current ownership.

For calculation practice, define total mass and composition before computing. Check that all component masses sum to the total and that percentages sum to 100%. An accurate calculation does not make a formulation safe or suitable. Treat numbers here as invented classroom data, not an industrial recipe.

A product’s lifecycle includes raw material sourcing, manufacture, transport, use and end-of-life handling. Durability can reduce replacement, but persistent waste can also create problems. Recycling needs appropriate collection, sorting and compatible processing. Contamination, mixtures and additives can reduce the usefulness of recovered material.

Biodegradable describes degradation under specified biological conditions; it does not automatically mean rapid breakdown in the sea or a home compost bin. A recycling symbol can identify material type without proving local collection accepts the product. Reducing unnecessary use and reusing suitable items are also strategies.

For an evaluation, compare alternatives for the same function and identify where evidence is missing. GE completed the sale of its Plastics business to SABIC in 2007; this hall preserves a former-business connection, not a current GE ownership claim. Chemistry lessons explain general principles rather than authenticate a pictured product.