Problem 1:A commonly used plastic that we did not talk about in class include a category known as high density polyethylene, designated under the acronym HDPE. In comparison to other common plastic types, HDPE is highly popular because it is sturdy and is a non-leaching translucent kind of plastic. Able to resist UV penetration, HDPE is commonly used to create anything from detergent bottles to yoghurt tubs to construction hard hats to hula hoops. As such, because it bears extreme tolerance to UV penetration, HDPE plastic is considered to be an ideal kind of material to produce food and beverage storage containers because the material is considered to be dishwater-safe and can hold up to temperatures ranging from -148 to -176 degrees Fahrenheit.

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Note that HDPE plastics are recyclable materials and bear the number “2” as their recycling number. Other common uses for this kind of plastic include water bottles, snack stack food storages, etc. 76% of HDPE is used for filming, 8% for extrusion coating, 5% for injection moulding, 4% for wire and cable and 7% for other kinds of produce. HDPE is produced by three main kinds of processes where hydrogen is mixed with ethene. In most cases, HDPE uses two types of catalysts. One is called the Ziegler-Natta organometallic catalyst made up of titanium and aluminum. The other is called the Phillips-type catalyst, which is basically an inorganic compound. Although HDPE materials are not known to leach any chemicals, the chemicals that are part of the make-up will start to break down with multiple, repetitive use. Overall, HDPE like other polyethylene materials is partially crystalline. Higher crystallinity increase density and the stability and endurance of its mechanical and chemical components.

Problem 2:
Bio-based or starch-based plastics are typically made from corn, soy or potatoes. Environmentalists have been concerned with the plight of the planet and as such have been leading figures in the latest decades doing work in the realm of composting using food as a means of creating plastics. Although bio-based polymers face challenges from, say, peutroleum-based polymers, a leading report by Lux Research showcases that the former can take over the latter. In any case, these kind of plastics break down 60 per cent or more of their material via composting usually within only 180 days, but in order to do so the materials require water, heat and aeration. According to the American Society for Testing and Materials (ASTM), a bio-based material is an organic material in which carbon is derived from a renewable resource (such as composting) via a biological evolutionary process. Examples of bio-based plastics include Spudware, which again is compostable and was used in the 2005 X-Games, an intensive competitive sport. You can find Spudware forks, spoons and knives everywhere nowadays. Market products used to make bio-based materials include corn, potatoes, rice, tapioca, palm fiber, wood cellulose, etc. Items such as Spudware are popular because they can also be washed and reused.

Problem 3:
Sand castings are usually produced in specialized factories, known as foundries, where 70% of metal castings are created via the sand casting process, which is usually cheap and has been used for centuries. In sand casting, sand is primarily used to define a cavity in the mold (a hole that can grow in size) and is usually produced via the use of a furnace, metal, patterns and a sand mold. There are six basic steps inherent to the process:
Create a pattern in the sand so as to create a mold you can work from.
Incorporate the pattern and sand in what is known as a gating system.
Take away the pattern.
Fill the mold cavity with molten metal.
Let the metal cool down.
Break the sand mold into parts and remove the casting, which will leave in your hands the solidified casting. The sand mold separates along a parting line, which is the point at which you may remove the solidified casting.

Problem 4:
Household window frames made of aluminum are to be used because they reduce the world’s carbon footprint, they are durable and are relatively easy to maintain. Also, they are generally speaking affordable and are known throughout the world for their design flexibility, their recyclability and their wide range of finishing touches. On the flip side, aluminum windows do not hold in heat well. In other words, their thermal conductance is very high. As such, aluminum windows do not work well in cold climates. By contrast, vinyl windows are popular because they offer amazing versatility. You can order vinyl windows to be rigid, flexible or customized for any application and, as an added bonus, you can order vinyl in a wide variety of color, pattern and texture. However, vinyl windows have an environmental impact given that it they are not a natural product. Given that New Mexico’s climate can go from very hot to very cold and that the weather is usually extremely windy, I would not use aluminum windows due to their inability to keep the cold out. As such, I would definitively use vinyl windows. That said, if I lived in Hawaii, given that it is not a cold climate, I would go for aluminum windows given that they are generally resistant to impact (high winds, for example, which tend to occur in Hawaii and should be considered as an important factor when buying windows).

Problem 5:
An 18 wheeler is typically known as a transport truck, made with 18 wheels. For such a truck, I would use a ductile material because it can yield at what are called normal temperatures. I would use low-carbon steel because it exhibits a fine linear stress-strain relationship until a specific yield point. On a truck, where the trucker has to often step on the gas or on the brakes suddenly, it is important to have a metal such as low-carbon steel that can respond to triggers easily and without too much energy or force.

    References
  • “7 Most Common Plastics and How They Are Typically Used.” http://www.reuseit.com/product-materials/learn-more-the-7-most-common-plastics-and-how-they-are-typically-used.htm
  • “Plastics and Oils.” Oilology Essentials. http://www.oilologyessentials.com/plastics-and-oils
  • Tokiwa, Yutaka et.al. “Biodegradability of Plastics.” International Journal of Molecular Sciences 10.9 (2009), 3722-3742.
  • “The Benefits of Aluminum Windows.” Capral Aluminum. http://www.capral.com.au/The-Benefits-of-Aluminium-Windows
  • Thryft, Ann R. “6 New Bio-Based & Renewable Plastics.” Design News. http://www.designnews.com/author.asp?doc_id=277313