Blog Entry 5

HELLO! I have finally returned to blogging ever since term break started HAHA😝. 

Today, I will be sharing about what I have learned in the first 2 lessons in this new term. Firstly, in the first lesson, I learned about Materials for Design (MFD). While, in the second lesson, I learned about Design for Materials (DFM) and sustainable design.

In the beginning, I was very confused about the first 2 topics (MFD & DFM) as they sound so similar, but I quickly learn that they are both two very different things.

Material for Design (MFD)

For a product to function as designed, the choice of materials is critical. Material selection is about finding a material that meets the needs of the product design, widely available, easy to work with and also economically viable. In MFD, the aim is to select the most suitable materials that will not only allow the product to function as per its intended design, but also enhance its competitiveness through cheaper and easier manufacturing process.

The design of a chemical product involves 3 interrelated problems:

1. Selecting a material
2. Specifying a shape
3. Choosing a manufacturing process

Additionally, when selecting or choosing a material, there are many material properties we need to consider depending on our chemical product.

Examples of some material properties:

• Mechanical properties (Strength, Hardness, Young's Modulus)
• Thermal properties (Specific heat capacity, Thermal conductivity)
• Magnetic properties
• Fabrication properties (Ease of machining)
• Environmental properties (Toxicity, Corrosiveness)

In the material selection process, there are 3 stages to it:

1. Define material requirement for the design
2. Select and evaluate candidate materials (COWS matrix)
3. Choose the most economical material

This leads us to our CA2 Report Part 1. My group was tasked to select materials for a reusable face-shield for medical workers to protect them against COVID-19 virus. For this assignment, we only need to focus on the transparent sheet and the support for the forehead.

Table 1: Material requirements for reusable face-shield

Functions	To prevent any germs, bacteria or virus from having any contact with the user’s face.
Constraints	Face-shields are not as effective as surgical masks in protecting users from viruses.  Face-shields may affect the user’s visibility.
Objectives	To protect medical workers against COVID-19 virus.

Table 2: Explanation for the weightages of the criteria for the transparent sheet

Criteria	Weightage (%)	Explanation
Reusability	30	It has the highest weightage because the face-shield is to be used more than once and it needs to be able to sustain for a long period of time. Thus, having a high reusability means that the face-shield can be used multiple times which is why it is given a 30% weightage.
Transparency	30	It has the highest weightage as having a higher transparency allows the user to have a clearer vision. This is essential and important as the user will be moving around while wearing the face-shield. Therefore, transparency is given a 30% weightage.
Scratch Resistance	10	It has the lowest weightage as it affects the main purpose of a face-shield the least. However, it is still necessary to have a good scratch resistance. This is because it can minimize the damage to the transparent sheet if dropped accidentally. Hence, scratch resistance is given a 10% weightage.
Low Density	30	It has the highest weightage because the face-shield needs to be light so as to ensure that it can be worn easily and comfortably. Thus, having a low density is very important which is why it is given a 30% weightage.

Table 3: COWS Matrix for the transparent sheet

Criteria	Weightage (%)	Options
		Polyester film		Polyethylene Terephthalate (PET)		Polycarbonate film		Polyethylene terephthalate glycol     (PETG)
Reusability	30	Good  Score: 3 3 x 30% = 90%		Poor  Score: 2 2 x 30% = 60%		Excellent  Score: 5 5 x 30% = 150%		Excellent  Score: 5 5 x 30% = 150%
Transparency	30	76.3%  Score: 2 2 x 30% = 60%		89.3%  Score: 5 5 x 30% = 150%		88.5% Score: 4 4 x 30% = 120%		87.5%  Score: 3 3 x 30% = 90%
Scratch Resistance	10	M = 92.5  Score: 4 4 x 10% = 40%		M = 92.5 Score: 4 4 x 10% =40%		M = 67  Score: 2 2 x 10% =20%		M = 110 Score: 5 5 x 10% = 50%
Low Density	30	1.38g/cc Score: 2 2 x 30% = 60%		1.33g/cc Score: 3 3 x 30%= 90%		1.20g/cc Score: 5 5 x 30% = 150%		1.26g/cc Score: 4 4 x 30% =120%
Total	100	250		340		440		410

After using the COWS matrix, Polycarbonate film is the most suitable material to be used for the transparent sheet of the face shield as it has the highest score of 440. Polycarbonate film is also rated the best for reusability and low density. Although polycarbonate film is not the best for transparency and scratch resistance, it is still acceptable.

Table 4: Explanation for the weightages of the criteria for the support for the forehead

Criteria	Weightage (%)	Explanation
Compressive Strength	25	It is important to have a high compressive strength as the support will be compressed onto the forehead of the user. Having a high compressive strength also increases the comfortability for the user. Thus, it is given a 25% weightage.
Flexibility	30	It has the highest weightage as it is very important that the support is flexible as it needs to be able to mold into the shape of the user’s forehead to provide comfortability and ease of wear. These 2 qualities are very essential to have for the support. Therefore, flexibility is given a 30% weightage.
Low Water Absorption	20	Although having a low water absorption has the lowest weightage, it is still important for the support to have a low water adsorption. This is to prevent any sweat or water from being absorbed by the support. If water or sweat is absorbed, the support will be heavier which affects the comfortability. Moreover, when sweat gets absorbed, the support might get very smelly overtime. Hence, having a low water absorption is given a 20% weightage.
Shear Modulus	25	It is important for the support to have high shear modulus. This is because we do not want the support to suffer from permanent deformation as the face-shield needs to be reusable. Thus, shear modulus is given a 25% weightage.

Table 4: COWS Matrix for the support for the forehead

Criteria	Weightage (%)	Options
		Polyester Foam	Polyurethane Foam		Silicon Carbide Foam
Compressive Strength	25	0.814 MPa Score: 1 1 x 25% = 25%	24 MPa Score: 5 5 x 25% = 125%		3.45 MPa Score: 2 2 x 25% = 50%
Flexibility	30	0.00119 GPa Score: 1 1 x 30% = 30%	0.96688 GPa Score: 2 2 x 30% = 60%		4.825 GPa Score: 5 5 x 30% = 150%
Low Water Absorption	20	<= 1% Score: 5 5 x 20% = 100%	36% Score: 1 1 x 20% = 20%		<= 1% Score: 5 5 x 20% = 100%
Shear Modulus	25	0.009556 GPa Score: 1 1 x 25% = 25%	4 GPa Score: 5 5 x 25% = 125%		1.13 GPa Score: 3 3 x 25% = 75%
Total	100	180	330		375

After using the COWS Matrix, silicon carbide foam is the most suitable material to use for the support for the forehead as it obtained the highest score of 375. Silicon carbide foam is also rated the best for flexibility and low water adsorption. Although silicon carbide foam did not score the highest for compressive strength and shear modulus, it is still acceptable.

 Table 5: Explanation for the weightages of the economical criteria for the transparent sheet

Criteria	Weightage (%)	Explanation
Cost of material	70	It has a very high weightage. This is because, if the cost of material per kg is expensive, it means that the overall cost of the chemical product will be very high which is not economical. Thus, the cost of material is very important and crucial, and is given a weightage of 70%.
Ease of manufacturing	30	Although it has a relatively lower weightage compared to the cost of material, it is still important to have a higher ease of manufacturing. This is because with a higher ease of manufacturing, the material will be more available. Therefore, the ease of manufacturing is given a weightage of 30%.

Table 6: Economical COWS matrix for the transparent sheet

Criteria	Weightage (%)	Options
		Polyester film	Polyethylene Terephthalate (PET)	Polycarbonate film	Polyethylene terephthalate glycol (PETG)
Cost of material	70	1.25 to 1.88 USD per kg Score: 4 4 x 70% = 280%	0.725 USD per kg Score : 5 5 x 70% = 350%	2.05 USD per kg Score : 3 3 x 70% = 210%	4.38 USD per kg Score : 1 1 x 70% = 70%
Ease of manufacturing	30	Good Score: 5 5 x 30% = 150%	Good Score: 5 5 x 30% =150%	Medium Score: 3 3 x 30% = 90%	Low Score: 2 2 x 30% = 60%
Total	100	430	500	300	130

After comparing the different materials using COWS Matrix, we can conclude that polyethylene terephthalate (PET) is the most economical material among the materials chosen as it obtained the highest score of 500. It is rated best for both the cost of material and ease of manufacturing.

Table 7: Explanation for the weightages of the economical criteria for the support for the forehead

Criteria	Weightage (%)	Explanation
Cost of material	70	It has a very high weightage. This is because, if the cost of material per kg is expensive, it means that the overall cost of the chemical product will be very high which is not economical. Thus, the cost of material is very important and crucial, and is given a weightage of 70%.
Ease of manufacturing	30	Although it has a relatively lower weightage compared to the cost of material, it is still important to have a higher ease of manufacturing. This is because with a higher ease of manufacturing, the material will be more available. Therefore, the ease of manufacturing is given a weightage of 30%.

Table 8: Economical COWS Matrix for the support for the forehead

Criteria	Weightage (%)	Options
		Polyester Foam	Polyurethane Foam		Silicon Carbide Foam
Cost of material	70	6.89 USD per kg Score: 2 2 x 70% = 140%	2.94 USD per kg Score: 5 5 x 70% = 350%		7.19 USD per kg Score: 1 1 x 70% = 70%
Ease of manufacturing	30	Medium Score: 4 4 x 30% = 120%	Good Score: 5 5 x 30% = 150%		Low Score: 2 2 x 30% = 60%
Total	100	260	500		130

After applying the COWS Matrix, polyurethane foam is the most economical material as it scored the highest of 500. It is also rated the best for both the cost of material and ease of manufacturing.

Design for Material (DFM)

In many instance, we want to use a certain material for a certain reason and because of that, we make changes and even compromises to the product design to accommodate the materials. These reasons can be cost, aesthetics and environmental sustainability. In DFM, we think about how the design can be modified slightly or even revamped so that the fully benefits of a material can be enjoyed.

In our CA2 Report Part 2, we had to select one material that appeals to us, find out how this material can be used as a replacement to a material in an existing product, and enhance the functionality of the existing product through some changes in the design.

	Group 2
Name of material	Super YUPO
Chemical name	Polypropylene Resin, synthetic paper
General description	A waterproof and food-safe synthetic paper that is highly UV, tear and shock resistant. Designed to be printed on single-sided, it was developed to be used with fast drying inks to create a super smooth, glossy finish.
General properties	Glue-free adhesion – High water and stain resistance – Very flexible due to thinness of the sheet – No need to treat the surface before printing
Opportunities	Potential to harness the “wow” factor of a material that can adhere freely to almost any surface. This clean, glue-free technology also offers opportunities to add a valuable eco story to products, while saving cost in production.
Source : https://ichatspedu.sharepoint.com/teams/digitalrepository/lib/Lists/Chris%20Lefteri%20Design%20Material%20Library/Attachments/12/Super%20YUPO.pdf
Discuss among the group how this material can be used as a direct replacement to a material in an existing product without any significant changes in the design.       Post-its are usually made out of pressure sensitive acrylate (PSA)  due to their ability to stick and restick. However this material is not waterproof and it has low tearing strength hence it can tear easily. When it comes in contact with water the post-it can lose its adhering ability. By replacing PSA with polypropylene resin which is a synthetic paper, the same level of adherence can be enjoyed while the product is waterproof and has greater tare resistance.
Discuss among the group how this material can be used to enhance the functionality of an existing product through some changes in the design.     YUPO is the recyclable, waterproof, tree-free Synthetic Paper with attributes and properties that make it the perfect solution for a variety of marketing and design.    Super YUPO is used for indoor and outdoor billboards, and displays.     + YUPO’s primary material is polypropylene. YUPO has outstanding durability, water-resistance and oil-resistance, protecting your valuable posters against wind and rain. YUPO posters last a long time and are PVC-free. + Distinguished Printability: YUPO has strength, as well as beauty. YUPO’s excellent printability includes outstanding reproducibility.  + Varied Line-Up: Besides the opportunity of choosing the thickness, there is also the degree of translucence, YUPO is ideal for back-lighted advertising displays. A whole variety of designs is yours for the choosing.   - Can only be used on surfaces that will be used in low temperature environments as humidity will affect adhesion. As a result it cannot be applied to outdoor products   A layer of gel medium can be added to protect the super YUPO from the low temperature environments, so that humidity does not affect adhesion on the Super YUPO paper.

Sustainable Design

In developing a product, choosing the correct materials is very vital. Sustainable design is the approach to creating products and sevices that have considered the environmental, social, and economic impacts from the initial phase through to the end of life.

Some of the sustainable design strategies:

Part 3 of our report required us to think through the ways and changes we can make to our chemical product design in CA1 (water filtration kit) more environmentally sustainable.

Substituting filter paper

Instead of using filter paper that needs to be thrown away each time after use, we can use a fine mesh metal sieve instead for water filtration. The most common material used to produce the sieves is stainless steel. Stainless steel 316 contains molybdenum which significantly boosts its corrosion resistance. The metal sieve size can be produced to emulate the porous properties of filter paper. Although plastic sieves exist, they tend to break easily since plastic’s tensile strength is relatively low compared to stainless steel which is not ideal as it is a hassle to constantly replace it. Moreover, plastic is a non-biodegradable material. It is also known that metal can be recycled continuously without losing its properties while plastic can only be recycled 2 or 3 times before it loses its properties hence proving to be a more sustainable product. Hence, a fine mesh metal sieve is preferred.

Substituting plastic tube
Instead of using a plastic tube to hold the raw materials, we can use a bamboo tube. Bamboos have a very high tensile strength due to its fibers and bamboos are relatively light. Additionally, bamboos have good elasticity, they will not snap easily when stress is applied. Comparing bamboo and plastic, manufacturing plastic requires more energy to produce and in fact, bamboo does not need to be manufactured as it can be found naturally, making bamboo more available to everyone. Bamboo is also highly renewable and it is biodegradable, while plastic is a non-renewable material and is non-biodegradable. Thus, a bamboo tube is a good substitute for a plastic tube for water filtration.