There is a growing discussion in the hardware world around the lifecycle of materials used in products. Users are doing their research and demanding safer materials that have low carbon footprints. As awareness about the harmful side effects of certain materials grows, designers and manufacturers must seek alternative hardware materials that still meet their design requirements. The ultimate goal is to create a safe hardware ecosystem free from harmful or potentially harmful materials.

Cradle to Cradle, a book that discusses the regenerative approach to design, describes the inefficiencies of today’s approach-- where 90% of the materials we use ends up as waste. The authors describe a proposed future where the waste from our current products can be repurposed or recycled back into new products, resulting in a net-zero production of waste. Their thesis spurned the rise of ‘The Living Future Institute’ (LFI) which created a stringent product and building certification program to encourage the use of healthy materials in both products and the built environment. LFI found in their research a list of materials widely used in industry, yet harmful to both people and nature, which they compiled into what they call the Red List. Materials that make the list include those that produce toxic by-products during manufacturing, release harmful chemicals, or cause future detrimental effects. Because the toxic nature of these materials can have a significant negative effect on human health and the natural environment, LFI has banned Red List materials from certified products or buildings.

Here we highlight a few widely used materials that have made it on the LFI Red List. We discuss the reasons for their listing as well as suggestions for potential substitutes with similar albeit non-harmful properties.

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Polyvinyl Chloride (PVC)

PVC is a material used everywhere: piping in our homes, coating for electronic wires, and tubing for medical applications. However, the production of the chlorine used in PVC releases a type of chemical called dioxin. Although dioxins are carcenogenic and can cause reproductive, developmental, and immune problems, they are still used pervasively in everyday hardware. While PVC is widely available and relatively cheap, its other properties, such as its impact resistance, can be easily found in other materials. While copper is more expensive, it is widely used in the same applications as PVC (particularly piping) and has similar levels of heat and water resistance. Another viable plastic alternative is PEEK (polyether ether ketone), which has a similar density and higher tensile strength. Similar to PVC, PEEK is one of the few plastics that can be used in high pressure applications, although it has a melting point nearly twice that of PVC. While the trade-off of designing for sustainability is often cost, some of these alternate plastics have added physical properties that make them independently better options.

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Nylon 1/6

As one of the most ubiquitous thermoplastics, Nylon has made its way into products we encounter every day, from seatbelts to sporting bags. Nylon 1/6 made its way onto the Red List due to the formaldehyde required during its manufacturing process. Because Nylon 1/6 can be cheaply produced, has high impact resistance, and self-lubricating properties, manufacturers neglect the negative side effects when considering its use. Formaldehyde is known in many industries to be a particularly dangerous volatile organic compound (VOC). Aside from being a respiratory irritant, formaldehyde is a carcinogen and directly linked to deaths relating from neurodegenerative diseases like ALS. However, engineers can manufacture products with those same properties using Nylon 6 or or Nylon 6/6. While on the more expensive side, both materials contain almost the same mechanical properties such as thermal expansion, yield strength, tensile strength, and flexural modulus, and are cleaner, safer, and devoid of formaldehyde.

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Polycarbonate (PC)

Polycarbonate, a plastic praised for its high heat resistance, is a common material that we encounter every day in personal protective equipment, CDs, and electronic components. But recent news has shed light on the dangers of BPA (Bisphenol A), a chemical component of PC commonly found in food storage containers and water bottles. BPA used in polycarbonate plastics has serious health ramifications such as hormone disruption, infertility, and negative behavior effects on newborns. If a certain product is required to be food safe, designers should consider FDA-compliant HDPE and PEEK plastics, both of which are not on the Red List and do not contain BPA. Although PEEK is not as easily recyclable as HDPE, it is biodegradable enough to be used in medical applications and is a much greener alternative to PC.

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Polyurethane (PU)

Polyurethane in its many forms is used in several manufacturing applications, from foam sprays to solid blocks. However, Polyurethane is often blended or coated with flame retardants and contains isocyanate, a skin and respiratory irritant that can cause asthma. Furthermore, only certain forms of polyurethane are recyclable. Two possible alternatives to consider instead of polyurethane are ABS and Nylon 6/6. They both have higher thermal expansion properties, but Nylon 6/6 has very similar mechanical properties such as its flexural modulus and yield strength. ABS, on the other hand, is a highly used, durable material that is recyclable-- ever wonder what those keys on your computer keyboard are made of? That’s ABS.

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Delrin (polyoxymethylene)

Delrin is a high performing thermoplastic used for mechanical, electrical, and medical applications. It is also known as polyformaldehyde, and as we mentioned formaldehyde earlier, it is a dangerous substance. When Delrin reaches high temperatures, it release formaldehyde, which makes conditions dangerous when recycling the material because it has to be melted down. Many engineers use Ultem instead because it does not contain formaldehyde and expands significantly less under heat. Ultem contains a similar density, tensile strength, and flexural modulus as PEEK, and has the added benefit of affordability. Another high-performance, high-temperature thermoplastic that designers consider is Polyphenylene (PPE). Like Delrin, Polyproperlene (PPE) is often used in products that require the materials to withstand use over extended periods, like in manufacturing environments, commercial grade furniture, or transportation vehicles.

Table 1.

Red indicates Red List materials, and Green indicates non-Red List materials.

Material

Density (g/cm^3)

Tensile Strength (psi)

Yield Strength (psi)

Coefficient of Linear Thermal Expansion

Flexural Modulus (psi)

PVC (polyvinly chloride)

1.3-1.45

7,500

4500-8700

54-110

480k - 490k

Nylon 1/6

1.5

11,500

6,500 - 8,500

50-90

420k - 500k

PC (polycarbonate)

1.2

10,500

10,000

65-70

345k

PU (polyurethane)

1.0 - 1.2

7,400

6,900

57.6

420k

Delrin (polyoxymethylene)

1.4

10,700

10,200

81

400k

ABS (Acrylonitrile butadiene styrene)

1.06

6,500

7,000

72-108

320k

HDPE (high density polyethylene)

0.93 - 0.97

4,600

4,200

108-200

200k

LDPE (low density polyethylene)

0.91 - 0.94

2,000

1,300

108-200

48k

Copper

8.79

32,000

36,000

16-16.7

6,500k

Nylon 6/6

1.13 - 1.15

11,500

6,500 - 8,500

80-85

420k - 500k

Nylon 6

1.12 - 1.17

11,500

6,500 - 8,500

80-85

420k - 500k

PEEK (polyether ether ketone)

1.31

14,000

12,000-13,700

2.6

590k

Ultem (polyetherimide)

1.27

16,500

20,000

56

500k

PPE (polypropylene)

0.9

4,800

4,400

72 - 90

150k


The industrial world is adopting a more sustainable and environmentally conscious perspective on their processes and products. As the standards for sustainability increase, a product’s entire lifecycle must take into consideration its ability for reuse instead of single-use with an added emphasis on health safety.  The onus lies on manufacturers and designers to find the safer alternatives and ultimately make the right choices for their products.


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