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A thermoplastic polymer is a type of plastic that changes properties when heated and
cooled. Thermoplastics become soft when heat is applied and have a smooth, hard
finish when cooled. Thermoplastics are amazingly versatile and can be heated and remolded
over and over again. This polymer conveniently melts at 58 to 60o C.
Hot water above 78oC
Glass stirring rod
Warning: Do not overheat! The melted polymer may be hot! Instruct students
not to put the polymer into their mouths. It will bond to metal braces.
Students should not make bracelets or rings as the polymer will harden and
be difficult to remove.
What is happening?
A chocolate slab can be heated and shaped into an Easter egg. On a hot day the Easter egg, again, is transformed into a new shape. Some polymers can be melted, cooled and re-melted just as with chocolate.
Polymers that can be heated and reformed over and over again are known as thermoplastics. This group makes up the majority of man-made polymers. These polymers can be shaped into any form. After heating, it can be shaped by extrusion – that is forcing it through a die. A heated polymer can also be poured or pressed into a mold. This is called molding.
On the other hand, when heat is applied to a raw egg, it solidifies as it is transformed into a solid boiled egg. After cooling, it cannot be transformed into another shape by heating. A group of polymers behave similarly. This type of polymer is known as thermoset polymers. These plastics undergo an irreversible molecular change when sufficient heat is applied. Their molecules form cross linkages, and this creates a rigid, permanent structure. Just as a boiled egg can't be un-boiled, thermoset plastics can't be softened again once it is heated and formed. We use thermosets in applications where durability, heat resistance, and strength are determining factors, for example as pan handles, refrigerator insulation, car parts, and in the electrical and space industries.
Can be heated and molded over and over
Have long, unconnected molecule chains with few or no crosslinks
Can ignite and burn when heated
Examples: Styrofoam packing peanuts, polystyrene plastics, plastic bottles, etc.
Once formed it cannot be softened by heat
Have many crosslinks between the polymer chains, forming a rigid structure
Usually resists burning, but may char at high temperatures
Examples: Epoxies, polyesters, RIM Urethane
Real Life Applications of Thermoplastic Polymers
Many applications take advantage of the material remaining workable for a period when
cooled below the melting point. Applications are:
Can be re-used many times. If there is a need to dispose of the polymer then do so in
compliance with local/federal regulations. This product is not significantly hazardous for
the environment and is biodegradable in soil.
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Students can use Thermoplastic Polymer to plan and conduct an investigation to describe and classify different kinds of materials by their observable properties.
Students can analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.
Students can use Thermoplastic Polymer to make observations to construct an evidence-based account of how an object make of small set of pieces can be disassembled and made into a new object.
Students can use Thermoplastic Polymer in an investigation to construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot.
Students can use Thermoplastic Polymer to make observations and measurements to identify materials based on their properties.
Students can use Thermoplastic Polymer in an investigation to develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
Students can use Thermoplastic Polymer in an investigation to develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.
A solution needs to be tested, and then modified based on the test results in order to improve it.
Students can use Thermoplastic Polymer in an investigation to observe and communicate scientific information about why the molecular-level structure is important in the functioning of a material.
Thermoplastic Polymers can be heated and molded over and over again due to the structure of long, unconnected molecule chains with few or no crosslinks. When added to 60 degree water, the thermoplastic polymer melts and be molded by hand into shapes. It can also be cut and extruded. The object can then be re-melted using hot water from a coffee pot. During the heating and cooling process the translucent white material changes to a clear substance that is pliable. Polymer Pigment (HEA-5RED, 5YEL, 5BLU, 5BLK) can be added to tint the Thermoplastic Polymer.
This versatile polymer can be used to make objects as well as show properties of matter.
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