Lesson video

Hello, thank you for joining me for your design and technology lesson.

My name is Mrs. Conway, and I will be guiding you through your learning today.

So our lesson outcome today then is, I can explain how polymer material properties can be enhanced.

And these are our key words: properties, combine, modify, reinforce, and structural integrity.

I'll go through each one of these as we work through the lesson.

So the first thing we're going to look at then is the combining of materials.

Now, materials don't always have the perfect properties for the job that we want them to do.

Sometimes they're too weak, too flexible, not hard-wearing enough, or can't handle heat or moisture.

Now, by enhancing material properties, we can make products stronger and last longer, as well as improve their safety and their performance.

It also allows innovation in design and function.

Now, properties are words that are used to describe how a material appears, so physical or characteristic, or behaves when worked, so working or mechanical properties.

Now, there are three ways that a material's properties can be enhanced.

So combining, which is when we join them together, modifying, which is changing, and reinforcing, which is making it stronger.

Okay, quick check for understanding on that then.

Which three methods are used to enhance material properties? A, compare, model, and reinforce; B, combine, manufacture, repeat; C, combine, modify, and reinforce; or D, compare, modify, and reuse.

Pause the video here.

Just take a moment to think about your answer.

And the correct answer, it was C.

So the three methods that are used to enhance material properties are combine, modify, and reinforce.

Well done if you got that right.

Now, composites are materials made by combining.

And we combine a matrix, which is a binder, and reinforcement for strength, to create a material that basically gives overall improved properties.

Now, an example of a composite, well, a composite is a little bit like a chocolate chip cookie.

The dough is the matrix or the binder and the chips are the reinforcement.

They are the added strength.

However, it can also be a bit like a lava or layer cake where the reinforcement is encapsulated, in the case of the lava cake, or layered through like the matrix, and that's like the example of the layer cake there.

Now the images below show a broken hole of a boat that has been made from glass-reinforced plastic or GRP.

Now, if you have a little look at this, the matrix is the resin and the reinforcement are the glass fibres, which hopefully you can see on that picture that shows the closeup on the right.

You can hopefully see the little glass fibres in there.

And they're blended together to result in a lightweight and corrosion-resistant material.

Okay, another quick check for understanding.

In a composite material, what is the role of the reinforcement? Is it A, to hold the structure together, B, to give strength or other useful properties, C, to add as a decorative layer, or D, to make the material more flexible? Pause the video here just to think about your answer.

And the correct answer then was B.

The role of the reinforcement is to give strength or other useful properties.

So other examples of blended matrix reinforcement composites include: carbon fiber-reinforced plastic, or CRP.

Now this combines layers of woven cloth of carbon fibres, which are the reinforcement, and resin, which are the matrix, and it results in a high strength, lightweight material and can be used for things like prosthetics.

Kevlar is another example as well.

Now, Kevlar, you may have heard of before, it's made from layers of woven Kevlar fibres, which is the reinforcement combined with a resin, which is the matrix.

And that results in a tough, lightweight material and can be used for things such as bulletproof vests.

Now, composite materials can have the matrix and reinforcement laminated or laid together, or encapsulated, which is enclosed.

So the encapsulated was the example of the lava cake and the layered together or the laminated was the example of the layer cake.

Now, board games are usually made from a paper-based board and a thin polymer layer, like polyethylene, laminated together.

Now, the polyethylene provides a moisture-resistant protective layer.

Formica is made from layers of paper or fabric and melamine resins that are compressed with high pressure.

And this actually results in a hard, heat-resistant surface that is often used for things such as kitchen worktops.

Now this particular process in the image you may know as lamination or may normally refer to it as being laminated, but it's actually an example of encapsulation.

The PET polymer pouch encloses the paper and card completely within it.

So that would be encapsulation, not lamination.

Okay.

Quick question for you then.

Why is Kevlar suitable for use in body armour? A, it is tough and lightweight, B, it is biodegradable, C, it conducts electricity, or D, it melts at low temperatures.

Pause the video here.

Just take a moment to think about your answer.

And the correct answer was A.

Kevlar is suitable for use in body armour because it is extremely tough, but also still lightweight.

Now, a polymer-based composite can have fibres from other materials blended with it to improve its properties.

So wood-plastic composites are a mixture of wood fibres and thermoplastics such as polypropylene, and it's used in decking, fencing, and outdoor furniture.

Now it's low maintenance and stable, and because of the polymer fibres, it can be moulded to mimic the wood grain of timber.

So it looks really smart.

People would think it's timber, but actually it has much more improved properties than that.

Okay, so why is wood plastic composite, or WPC, often chosen for outdoor decking instead of natural wood? Is it A, it is softer and easier to cut, B, it is cheaper than all natural woods, C, it resists moisture, or D, it doesn't rot or splinter.

Pause the video here just to take a moment to think about your answer.

And the correct answer, it's actually really useful because it resists moisture and also it doesn't rot or splinter.

Okay, it's gonna be over to you now to have a go at some tasks.

First thing I'd like you to do, I'd like you to explain what a polymer-based composite is, referring to the terms matrix and reinforcement in your answer.

So you've got some key vocabulary to include in your answer there.

Secondly, I'd like you to describe two benefits of using a composite material.

Now, I'd also like you to use examples in your answer there.

And lastly, I'd like you to answer this question: what is the difference between laminating and encapsulating with polymers? And you can use labelled diagrams to support your answer.

Okay, it's gonna be over to you now.

So pause the video here and good luck with these tasks.

Okay, let's go through each one of these tasks in turn.

And I've got some example answers for you for each one.

So the first thing I wanted you to do was to explain what a polymer-based composite is, referring to the terms matrix and reinforcement in your answer.

So a polymer-based composite is a material made by combining a polymer matrix, the binder, with a reinforcement, such as fibres, to improve strength and performance.

The matrix holds the structure together whilst the reinforcement adds strength and stiffness.

So just compare your answers to mine.

Have you been able to explain that in enough detail and have you made sure that you've included those terms matrix and reinforcement in your answer? Okay, secondly, I'd asked you to describe two benefits of using composite materials, and I also asked you to use examples in your answer.

So the first example or the first benefit I've given there is it's lightweight but strong.

And the example I've given is CFRP, which is used in aircraft because it is strong, yet much lighter than metal.

And the other benefit I've given is resistance to corrosion and rot.

So such as WPC, which is ideal for outdoor decking as it doesn't splinter or decay like natural wood.

So again, just check, have you given two benefits and have you used examples in explaining it? And your last task, then, what is the difference between laminating and encapsulating with polymers? And I asked you to use labelled diagrams to support your answer.

So the example answer says: Laminating involves bonding layers of material together, EEG board and polyethylene film for strength and protection.

Encapsulating, however, it means fully enclosing a component in a polymer layer, e.

g.

a sheet of paper inside PET film.

And we've got some examples here with the diagrams on what they could possibly look like.

So first of all, we're showing lamination, which shows that polyethylene film cover covering the board.

Where as the encapsulation, the component is sealed inside all the way around by a polymer.

So again, just compare your answers to the ones in front of you and see, have you got all of the details that you need there? So next, now we're going to look at modifying materials.

Now, modifying the material means changing its structure or its composition, which is what it's made from, to improve how it performs. And the changes usually take place at a molecular level and include things such as additives, heat treatments, and chemical treatments.

So we'll take each one of these in turn.

Polymers are often modified with additives to improve colour, for example, as well as flexibility, UV resistance, fire resistance, and also antistatic.

Now, commonly-used additives include plasticizers.

Now, plasticizers, these increase in flexibility.

So for example, in cables, flexibility is really important and is needed so plasticizers are used there.

Stabilisers, now these prevent polymers from becoming faded under like UV, and also they can sometimes become brittle from that sunlight as well.

And fillers, these reduce cost and sometimes also improve strength.

Okay, quick check for understanding then.

What is the purpose of adding a plasticizer to a polymer? A, it makes it harder, B, it changes its colour, C, to reduce UV damage, or D, to increase flexibility, Pause the video here.

Just take a moment to think about your answer.

And the correct answer was to increase the flexibility.

And we looked at the example of the charging cable.

So heat treatment is another example, and this is used to alter the molecular structure of polymers to change their properties.

Now, heat treatment can change strength and also rigidity.

And a common method to heat treat polymers is curing.

Now, cross-linking is a chemical reaction where polymer chains form strong permanent bonds between each other.

Thermosetting polymers like epoxy resin or melamine resins are liquids, and can use heat to help them cure, which is to set.

Once cured, or set, they cannot be reshaped or recycled easily, unlike thermoplastics.

So thermoset polymers are heat resistant and used for electrical fittings, for example, and also panhandles, where, actually, that heat resistance is incredibly important as a property.

Why can thermosetting polymers like epoxy resin not be reshaped after curing? A, They are too soft after curing, B, they lose their chemical structure over time, C, cross-linking creates permanent bonds between polymer chains, or D, they contain metal particles that harden the resin.

Pause the video.

Just take a moment to think about your answer.

And the correct answer was C.

So thermosetting polymers like epoxy resin cannot be reshaped after curing because cross-linking creates permanent bonds between polymer chains.

Well done if you got that right.

Polymer-based materials can also have chemical treatments to enhance their properties as well.

So resins can also have a photo-hardening chemical added to it so it could be cured quickly under UV light, like those that are used in dental composite fillings, for example.

Polymers such as nylon can be treated with a chemical coating to make them fully waterproof.

So perfect for umbrellas.

Okay, over to you for a few more tasks then.

First thing I'd like you to do is I'd like you to explain how plasticizers and stabilises change the properties of polymers.

Secondly, I'd like you to explain why thermosetting polymers cannot be reshaped once they have been cured.

And in your answer, I'd like you to really refer to the structure of the polymer, and the process of cross-linking.

And lastly, I'd like you to explain how chemical treatments can enhance the properties of polymer-based materials.

And I'd like you to give two examples in your answer for this.

Okay, it's over to you.

So pause the video here and good luck with this task.

Okay, let's have a look at these in turn.

So the first task then was to explain how plasticizers and stabilisers change the properties of polymers.

So my example answer is: plasticizers make polymers more flexible and less likely to snap.

Stabilisers protect polymers from breaking down due to UV light or heat, helping them last longer in outdoor environments.

So just check if you've explained those in the same amount of details as that example answer there.

You may have even given example of products that use plasticizers and stabilises, I didn't ask you to, but you may have included those.

The second task then was to explain why thermosetting polymers cannot be reshaped once they have been cured.

And in your answer I asked you to refer to the structure of the polymer and the process of cross-linking.

So my example answer says, "Thermosetting polymers cannot be reshaped after curing because the cross-linking process creates strong permanent bonds between the polymer chains and these bonds form a rigid structure that doesn't soften when reheated.

This is different from thermoplastics which do not have cross-links and can be reheated and reshaped." Again, just compare your answer to the example there.

Have you included the same level of detail and all of those key points? And lastly, I asked you to explain how chemical treatments can enhance the properties of polymer-based materials.

And I asked you to specifically give two examples in your answer.

So chemical treatments can improve polymer properties by improving their performance.

For example, some resins have photo-hardening chemicals added so they can cool quickly under UV light such as in dental fillings.

Another example is nylon, which can be coated with a chemical to make it fully waterproof.

So you've got two examples in that answer there.

And also it's been explained how those can enhance the properties of polymer-based materials.

So lastly then we're going to look at these keywords: structural integrity.

Now materials can be reinforced to enhance their properties, and we've already looked at that during this lesson.

Reinforcement involves adding an element or altering the structure of a material to improve its performance under stress.

And reinforcement techniques can be applied to a variety of materials, including: timbers, polymers, papers and boards, textiles, and metals.

So there's a range of different materials that can be reinforced.

Okay, quick check for understanding then.

Why might materials need to be reinforced? A, It improves aesthetics, B, it makes them stronger and last longer, C, to reduce costs for the consumer, or D, it makes them more environmentally friendly.

Pause the video here.

Just have a quick think about that question.

And the correct answer, it was B.

So materials need to be reinforced to make them stronger and also last longer.

Now, reinforcing materials improves their structural integrity and structural integrity refers to how well something stays together and holds up without breaking.

So for polymers, the techniques used to ensure structural integrity are particularly prevalent in hollow structures that require being strong and also lightweight.

For example, children's toys.

Quick check for understanding on that, then.

What does structural integrity refer to in materials and structures? A, the ability of a structure to maintain its shape under normal conditions without breaking, B, the aesthetic appearance of a structure, C, the ability of a structure to resist environmental changes like temperature and moisture, or D, the cost effectiveness of building a structure.

Pause the video here just to take a moment to think about your answer.

And the correct answer was A.

So structural integrity refers to materials and structures the ability of a structure to maintain its shape under normal conditions without breaking.

Polymers can be injection-molded into complex shapes.

And this means that features to ensure structural integrity can be incorporated into the moulding process.

Now gussets are an additional tabs used to reinforce corners, and you can just about see those in that little picture there.

And again, you may have seen these in real life.

Ribbing is wall-to-wall and that's additional material to provide extra strength.

And you can see there in the building brick, an example of that ribbing just to provide that additional strength.

Overmolding with a softer polymer can improve grip, which obviously improves the ergonomics of a product, but can also include more strength and flexibility at stress points.

Other types of polymer moulding processes can include features to enable structural integrity.

So this is an example of a thermoformed PET cup, which has a rolled edge on the rim and also ridges on the sides to provide strength.

Now obviously that does also improve the ergonomics of the product, but actually we're focusing on the strength that those elements provide there.

This is an example of a blow-molded PET bottle and has indentations, again, to prevent collapsing of that bottle.

Quick check for understanding on that, then.

What is the benefit of ribbing in injection-molded polymers? A, it improves the aesthetic appeal of the product, B, it makes the polymer more flexible, C, it makes the product more lightweight, or D, it adds extra strength by providing wall-to-wall material.

Pause video here.

Just take a moment to think about your answer.

And the correct answer was D.

It adds extra strength by providing wall-to-wall material.

Well done if you got that right.

Now, manipulation of sheet polymers can alter their strength too.

Corrugation is a technique that involves incorporating a fluted or wavy layer sandwiched between two flat sheets of material to increase its strength and stiffness without adding much weight.

So you can see in the diagram here, you've got that wavy or fluted middle layer, and then the outer layers are flat.

So here's example of corrugated polypropylene, and these can be used for things such as signage and also packaging.

And these have that corrugated fluted, wavy middle layer and those kind of flat outer layers.

You can just about see that there.

You can also see example of corrugated polycarbonate.

And now these can be used for things such as sheet roofing.

Manipulation of sheet polymers can alter their strength too.

So hexagons are a structurally strong shape.

They fit together perfectly without any gaps making them ideal for use in sheet materials.

Hexagons spread load evenly in all directions and they use less material to cover the same area compared to other shapes.

So here's examples of hexagons in use.

Nomex core is a polymer composite with a honeycomb structure, that hexagon pattern, and these are used in aircraft panels in things such as the floor, the walls, and the ceilings for high strength, low weight, and also fire resistance.

Okay, it's gonna be over to you now for the last tasks of today's lesson.

The first thing I'd like you to do is draw a labelled diagram to explain the structure of corrugated polypropylene and how it provides strength.

The second task, I'd like you to explain how ribbing and gussets improves the structural integrity of polymer-based material.

And lastly, I'd like you to give one use for Nomex and explain how its structure is suited for this application.

Okay, it's over to you now.

So pause the video here and good luck with this task.

Let's work through each one of these in turn then.

The first thing I asked you to do was to draw a labelled diagram to explain the structure of corrugated polypropylene and how it provides strength.

So here we've got the diagram.

We've got those outer flat layers and that fluted or wavy middle layer.

And just to explain there, the fluted layer between the flat sheets provides strength and rigidity.

Just compare your answer to the example in front of you and check you've got everything included on there.

The second task, then, I asked you to explain how ribbing and gussets improve the structural integrity of polymer-based materials.

So ribbing adds strength by providing extra material along the walls, preventing bending and warping.

Gussets reinforce corners, strengthening weak joints to prevent cracking.

So just again, compare your answer to the example there.

And lastly, I ask you to give one use for Nomex and explain how its structure is suited for this application.

So the example answer says, "Nomex is used in aircraft panels due to its unique honeycomb structure.

This structure is made up of hexagons that spread load evenly in all directions, providing high strength while keeping the material lightweight." Again, compare your answer.

Have you got the same level of detail? Have you missed any key points there? Okay, so let's summarise today's lesson.

Today we've been looking at enhancing the properties of polymers.

Now combining materials creates improved properties compared to individual materials alone.

And that is why we combine materials, to improve their properties in some way.

Material properties can be modified with the use of heat and/or additives, and reinforcing techniques can improve a material's structural integrity.

Well done for all of your hard work today.

Thank you so much for joining me, and I will see you soon.