Question

Briefly describe each of the following: (a) elastomer, (b) thermoplastic, (c) thermosetting plastic, (d) plasticizer.

Short answer

(a) Elastomer: A polymer with elasticity, allowing it to return to its original shape after being deformed. Examples include natural rubber, silicone, and neoprene. (b) Thermoplastic: A polymer that becomes soft when heated and can be molded into various shapes, with reversible physical property changes. Examples include polyethylene, polystyrene, and PVC. (c) Thermosetting Plastic: A polymer that cannot be remelted and remolded after being cured, forming a rigid, infusible structure. Examples include phenol-formaldehyde, epoxy, and melamine. (d) Plasticizer: A substance added to polymers to increase flexibility and workability by reducing intermolecular forces. Examples include phthalates, adipates, and citrates.

Step-by-step solution

(a) Elastomer

An elastomer is a polymer with the property of elasticity, meaning it can return to its original shape after being deformed by stress. Elastomers have a low modulus of elasticity, making them flexible and easy to stretch. Examples of elastomers include natural rubber, silicone, and neoprene.

(b) Thermoplastic

Thermoplastic is a type of polymer that becomes soft and pliable when heated and can be molded or formed into various shapes. This change in physical properties is reversible, meaning it can be heated and cooled repeatedly without undergoing any significant chemical change. Examples of thermoplastics include polyethylene, polystyrene, polyvinyl chloride (PVC), and polypropylene.

(c) Thermosetting Plastic

Thermosetting plastic is a type of polymer that cannot be re-melted and re-molded once it has been set (cured) by heat or other means. When heated, thermosetting plastics undergo an irreversibly chemical change that creates a rigid, infusible, and insoluble structure. Examples of thermosetting plastics include phenol-formaldehyde, epoxy, melamine, and urea-formaldehyde resins.

(d) Plasticizer

A plasticizer is a substance, typically an organic compound, which is added to polymers to increase their flexibility, workability, or distensibility. Plasticizers work by reducing the intermolecular forces within the polymer, allowing the polymer chains to slide past one another more easily. This makes the material more flexible and easier to process. Examples of plasticizers include phthalates, adipates, and citrates.

Key concepts

Elastomers

Elastomers are fascinating materials widely recognized for their remarkable stretchiness and ability to return to their original shape after being deformed. This characteristic, known as elasticity, is what gives elastomers their name and makes them essential in everyday applications like tires, elastic bands, and waterproof seals.

Elastomers are unique because they have a low modulus of elasticity, a technical way of saying they're incredibly flexible and not too stiff. Imagine a rubber band; you can stretch it out, and when you let go, it snaps back to its original size and shape. That's an elastomer for you! Natural rubber, silicone, and neoprene are all prime examples of elastomers that showcase this impressive property.

The key takeaway here is that whenever you need a material that can endure stretching or compressing and then easily bounce back, elastomers are likely your best bet.

Thermoplastics

Thermoplastics are one of the most versatile materials in the manufacturing world thanks to their ability to melt, mold, and then solidify without losing their chemical properties. This amazing feature means you can heat, shape, and then cool thermoplastics over and over again, which is incredibly useful in recycling.

What sets thermoplastics apart from their cousin, the thermosetting plastics, is that they do not undergo a chemical change when heated. This reversible behavior is akin to how ice melts to water and can refreeze without changing its chemical structure. Common thermoplastics include the familiar polyethylene used in plastic bags, polystyrene in foam cups, PVC in pipes, and polypropylene in various containers.

If you've ever used reusable containers or stretch wrap in the kitchen, you've taken advantage of the convenient thermoplastic properties. So the next time you pop a container in the microwave, think of the incredible science that allows thermoplastics to be so reshapable and handy!

Thermosetting Plastics

Thermosetting plastics are a bit like baking a cake; once set, you can't just go back to the batter. These materials undergo a permanent chemical change when heated, leading to a solid form that's inflexible but incredibly durable and heat resistant – excellent for applications that must withstand high temperatures.

Unlike thermoplastics, thermosetting plastics cannot be remolded or softened by reheating, as their molecules form strong cross-linked bonds during the curing process. This irreversible chemical reaction eliminates the melt-and-reshape possibility, but you get a substance that's solid and resistant to melting. Items like electrical plugs, electronic circuit boards, and heat-resistant handles on cooking pots are made from thermosetting plastics such as phenol-formaldehyde and epoxy resins.

Remember, thermosetting plastics are the go-to materials when you need something that can take the heat without losing its composure, quite literally!

Plasticizers

Plasticizers are like the secret sauce that makes plastics more pliable and flexible. By being added to a polymer, plasticizers weaken the forces holding the polymer chains together, allowing them to move around more freely. This increased mobility results in a softer, more flexible material – think of how a stiff piece of plastic can be transformed into a bendable or squishy object.

It's important to know that plasticizers can greatly affect the properties of a plastic, influencing everything from how it feels to its durability. They are critical in creating products like vinyl flooring, wire coatings, and some medical devices, which all require a specific level of flexibility not inherent to the base plastic itself. Examples of commonly used plasticizers are phthalates and citrates, which have been crucial in developing a broad range of soft plastic products.

In short, without plasticizers, many plastics would be much less versatile and functional in our daily lives. So, next time you handle a flexible plastic product, chances are, there are plasticizers at work giving it those useful, bendy qualities.