By the end of this component, students will be able to explain why and how materials are selected and how they enable outcomes (technological products) to function as expected.
Technological products are material objects that have been designed by people and developed through technological practice to serve particular functions.
A crucial relationship between the (chemical) composition and structure of the materials used and their performance properties exists in every technological product.
For this reason, students (technologists) need to be able to evaluate different materials and select the most suitable for their purpose. Students also need to understand how:
- existing materials can be modified
- new materials formulated
- their choice of materials impacts on the design, development, maintenance, and disposal of their outcome.
Carol Rimmer talks about understanding the materials in technological products.
As 21st Century learner,s I feel it’s important that our students know about the design, development, maintenance, and disposal of technological products – and in order for them to do that, they need to know the relationship between the materials used in those technological products and the performance properties that they will bring to that product and how that product will perform in the end.
Some technological products are defined as material objects.
As textiles is my area of expertise I find it easier to think about it in a textile way, and that if a technological product is a material, so what is the material, especially if that material is wool.
So, wool can be a fibre, that’s a material. Wool can be generated into a yarn and as a material whether it’s woven or knitted.
If the technological product is a hat or a toy, felted material can be used, and wool is transformed by using heat and moisture into a material. The resulting material isn’t particularly strong because of the random nature of the fibres, but all the original performance properties of the wool fibre are retained.
So, for example, the scaly exterior of the wool fibre is what is used in the felting process. The overlapping scales of the wool fibre will lock with each other in the heat and moisture transformation process, and that helps form the material.
We still get the warmth of wool because we have the scaly nature of the wool which traps air, we still have the resilience from the crimp in the wool, and we still have the resistance to water, which is due to the lanolin that is present in wool. So, although we have a fabric, it is still the existing wool fibre is what is used in the fabric, and we still retain those performance properties in that technological product of the hat or toy.
If we take the wool fibre to the next stage, which is a spun yarn, and we think of the technological product as a carpet and the fact that we want resilience and durability, then we look at the original fibre, which comes from the Romney sheep. And the Romney sheep is chosen because it produces a particularly coarse and strong fibre, which is then cleaned and scoured and spun into a yarn, which is used for carpeting. Even the way that the yarn is twisted, in this case a Z-twist, which is a stronger, springier yarn, is considered because the end product is a carpet.
We still want those properties if we are spinning a yarn for baby wool. We still want resilience, we still want softness, we still want comfort from the yarn, but we’ve got a different end purpose. So this time, in thinking that the end product is for babies, then we choose the merino wool, which is a finer, longer, wool fibre that has the same amount of crimp, sorry, that has more crimp than the Romney, and it is particularly soft and easy on the babies skin and can be washed.
So those are two examples of end products, technological products, where the wool fibre is used in a different way but going through a very similar process.
So with the babies wool, the spun yarn is knitted into the end product, and the knitting process itself enhances the purpose of the materials used because the knitting structure – the loose loops – then adds to the softness of the garment and also helps to trap air, so again contributes to the comfort of the garment for the baby. So once again we have the wool fibre that is spun and then it’s knitted for the purpose of the end product.
So then if we take this into a tailored jacket which is woven, we again have the spun yarn that is then woven, and the weave for the jacket is selected depending on the end purpose.
If it’s a school uniform jacket then they'll choose a twill weave because a twill weave is the strongest weave.
They’ll also manipulate the fabric in areas of stress. So collars and pockets will be interfaced. So the interfacing is fused or sewn on, therefore giving the properties of the wool fabric some extra strength in areas of high stress. So the technological product is the jacket, but our students need to understand that in order to select the material for the jacket, they need to be knowing about the chemical composition of the fibre – how it’s spun, how it’s then woven, and then how it’s manipulated by the use of interfacings to be fit for purpose at the end product.
So then we have to start thinking about how do we know these things, and in the classroom we teach the students about evaluative tests, subjective and objective.
And the subjective ones are always the ones that come straight to mind. When we are looking, particularly in textiles, we’re always drawn in by colour, texture, the look and the feel of the garment, and if it suits the wearer, and those types of things. But when we are evaluating things like crease resistance, resiliency, we need to be using objective tests. We need to be using, or be aware of, commercial testing because it’s formal testing that can tell us how that particular material relates to the end product, and it will also tell us if there is something better on the market.
So when we’re looking at materials specifications, we need to make sure that our students are doing relevant testing for the item that they may be producing or the technological product. So crease resistance is quite an easy one to do, and it’s often one that’s wanted.
Washing, yes – put it in the family wash, have a test piece and test to see if it’s going to shrink – but there’s no point in doing a test for something that isn’t relevant for the particular specification of the technological product. So as teachers we need to be mindful that we are giving our students the right information and the right experiences, and there’s plenty of information on those tests in textbooks, on the Internet that we can get our students doing relevant testing.
Our students need to know about the chemical composition of materials and how they have been formed, transformed, and manipulated in order to understand how those materials are going to perform in the technological product.
The area of textiles, for example and materials, is vast, certainly can’t cover everything in the classroom. But I think our challenge as teachers is to make our students aware of what’s happening in the world about the smart materials that are being developed at the moment, and there’s always interesting stories in the news about new materials that will capture their imaginations, and they're used in the most unusual ways and not necessarily in the way that they are going to be used in the classroom. The whole area of smart materials in medicine is huge at the moment.
So be aware of what’s happening, what’s being reported on the news, bring those into the classroom and give the students the opportunity to think outside the classroom.
Acknowledgment: This paper is derived from an earlier version by Dr Vicki Compton and Cliff Harwood.