Thermoplastics and Recycling (Grades 6-12)

SPE & Girl Scout Councils

Thermoplastics and Recycling (Grades 6-12)

Goal: Scouts will understand how thermoplastics are used in manufacturing and recycling. 

Supplies: Polly plastic sticks*, water, something to heat water in, tongs, scissors, colored mica powder*. (*These items are in the Color Your World with Polymer Science kit found at the scout store.) 

Activity:  

Watch Thermoplastics and Recycling video.
Mold Polly Plastic into different shapes. Add color.

Procedure: Cut the white Polly Plastic sheets provided into squares about 1.5” square. Ask the girls to identify the physical properties of the thermoplastic stick before you put it in the boiling water. (Properties: rigid, smooth, rectangle shape, shiny, matte, etc.).

Using tongs, the troop leader will place the Polly Plastic stick in the heated water. Swish back and forth. The plastic will turn clear when ready to mold. Remove it from the water, letting the hot water drip off, then hand it to the scout to begin molding the plastic. The plastic will not be too hot to handle. Discuss the physical properties of the Polly Plastic after it was heated and how they changed. (Properties: soft, warm, moldable, etc.).

Put the mica powder on a plate. Reheat the plastic and have the girls quickly dip the warm plastic into the mica powder (you need very little). Mix the mica colorant into the plastic while remolding it. Observe how the physical properties are changing. Adding coloring in the form of mineral powder changes some properties of the plastic e.g., making it stiffer or harder to mold. Manufacturers add different things to plastics to change the properties of materials.

Plastics can be divided into two major categories: 

Thermosets. Once cooled and hardened, these plastics retain their shapes and cannot return to their original form. They are hard and durable. Thermosets can be used for auto parts, aircraft parts and tires. Examples include polyurethanes, polyesters, epoxy resins and phenolic resins. 
Thermoplastics. Less rigid than thermosets, thermoplastics can soften upon heating and return to their original form. They are easily molded and extruded into films, fibers, and packaging. Thermoplastics are 100% recyclable. In ideal situations thermoplastics can be repeatably melted and remolded into new products. This is the foundation of recycling. Examples include polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET). 
A cooked egg is a good thermoset example. After heating an egg, you can cool it or reheat it, but it will never return to its liquid state. It remains solid, just as thermoset polymers do. But if you cool melted cheese, it regains its solid form. Reheat it and it flows again, just like thermoplastics.

Outcome: Students understand that thermoplastics can be reheated and remolded into new products. 