Ryan Pang
3/13/14
DES40A
Prof. Cogdell
Raw Materials in the Toothbrush
Dental cavities and tooth decay caused from bad oral hygiene are the most common medical conditions experienced by Americans and the single most common disease of childhood. If not treated, poor oral health is gum disease, which can be mild in the initial stages, but lead to much more severe problems if untreated.[1]The importance of maintaining good dental health is a necessary duty for all people and animals alike. Because of the importance of practicing good oral hygiene, the growth of technology allowed Babylonian people as early as 3500 B.C., to have used tools such as chew sticks found in a tomb in Egypt dating from 3000 B.C.[2] Overtime, the earliest invention of thefirst bristle toothbrush, resembling the modern toothbrush, was found in China. The materials used for this brush consisted of hog hair for bristles and bamboo or bone for handles and at the time was a big technological advancement in its time.[3]As time went on, mass production of the toothbrush started in 1885 in the United States using boar bristles which did not do well with bacteria, had a common tendency to fall out eventually, also in which handles were made out of wood and ivory.[4] The on-going search for a long lasting material for the use of a toothbrush has been long-winded. Finally, in 1990, celluloid handles gradually replaced bone handles in toothbrushes. Natural animal bristles were also replaced bysynthetic fibers, usuallynylon, byDuPontin 1938.[5] In the dental industry, the uses of these new synthetic materials have become standardization in mass production of the toothbrushes.
Synthetic plastics we use today are made from inorganic and organic raw materials, such as carbon, silicon, hydrogen, nitrogen, oxygen and chloride. The basic materials used for making plastics are extracted from oil, coal and natural gases.[6] After recent advances in the dental industry, toothbrush handles are now usually made out of a moldable, recyclable thermoplastic material known as polypropylene and polyethylene. Polyethylene (PE) is a polymer of long chains of the monomer ethylene. Polyethylene is one of the world’s most common plastics, with a wide range of uses and over 60 million tons produced worldwide every year but requires a modification in the properties that are responsible for the PE resistance to degradation.[7]This material is made from naphtha, otherwise known as petroleum which is extracted from crude oils.[8] By applying strong temperatures in the naphtha, ethylene is released. Once in a factory ethylene is transformed into polyethylene which means: "a lot of ethylene parts”.[9]Many plastics such as polyethylene are inert and prone to microbial attack, leading to their unwanted accumulation in the environment. Ethene is a very simple two-carbon organic molecule (C2H4) that does not have to be derived from petroleum. However, the high molecular weight, 3-dimensional structure, hydrophobic nature and lack of functional groups in the LDPE interfere with microbial attack in which microorganisms play a significant role in the biological decomposition of material.[10]Nonetheless polyethylene is flexible, translucent / waxy, weatherproof, good low temperature toughness (to -60°C), easy to process by most methods, low cost, good chemical resistance.[11]Themelting pointof polypropylene is very high compared to many other plastics, at 120°C which is very useful for washing the material without high temperatures causing the plastic to warp.[12]The use of polyethylene is an innovative idea in a sense because the polymer has more beneficial characteristics over the detrimental. Many can see why companies still choose polyethylene but the fact that the plastic is not biodegradable, which is where polypropylene shines.
Both plastics are similar but Polypropylene is not as sturdy as polyethylene. Major oral care companies decided to take a more sustainable route and pick the use of polypropylene because the material is easily recyclable and has benefits that make it the better choice than polyethylene in many situations. Polypropylene (PP), a thermoplastic material that is produced by polymerizing propylene molecules, which are monomer unites, into very long polymer molecule or chains.[13]There are many ways to link these monomers together but polypropylene is made with catalysts that produce crystallizable chains. By linking these chains, the product forms into a semicrystalline solid that give it a good physical, mechanical and thermal properties. The material is used in many different settings, both in industry and in consumer goods, and it can be used both as a structural plastic and as a fiber.[14]Polypropylene is highly fatigue-resistant and can stand up to continuous flexing, it’s used to make most of the “living hinges” you’ll find on the market (think flip-top plastic caps on ketchup bottles, shampoo and toothpaste, or the snap-open lids on Tic-tac dispensers). This polymer is also widely used in both small and large appliances. Small appliances include electric drip coffee makers, can openers, blenders, mixers, tools such as electric drills and toothbrushes. Larger appliances include parts in dishwasher liners, which take place of porcelain interiors, and in washing machine agitators, soap, bleach dispensers, and other parts.[15]
Polypropylene has excellent and quite desirable physical, mechanical, and thermal properties when used in room-temperature applications. Polypropylene is very resistant to acids, bases, and other harsh chemical solvents, and since it’s also nonconductive, it can often be used as a dielectric. The plastic is known to have a melting point at around melting point of 140°-160°C, depending on if the polypropylene is a hom*opolymer or a copolymer.[16]The difference between a hom*opolymer and a copolymer is that a hom*opolymer is formed from only one type or monomer which in contrast to a copolymer contains at least two monomers.[17]Toothbrush handles range from hom*opolymer and copolymer properties depending on manufacturer. However unlike copolymer polypropylene, hom*opolymer polypropylene is now one of the most widely used polypropylenes out in the market today. hom*opolymer propylene is made in several different reactor designs using catalysts that link the monomers together, resulting in polymer chains that are crystallizable. Polymer chains weave up and down into close-packed arrays known as “crystallites”. Once polypropylene is cooled from a melt, crystallization occurs. The higher the temperature, the more rapid crystallization occurs. The stiffness of polypropylene typically increases as the level of crystallinity increases. Stiffness generally decreases as the crytallizability (tacticity) decreases or, in random copolymers, as ethylene content increases, crystallizability decreases.[18]In injection molding, rather than making this polymer stiff, the polymer is first softened and conveyed with a screw in a manner similar to extrusion, and the polymer is pushed through a runner system into a cavity or multiple cavities of a mold. The mold is then cooled, and eventually the mold separates and solid parts are ejected and stacked.[19]
Additional materials on a toothbrush include the bristles which are now made of a specific synthetic polymer known as nylon. Nylon is the world’s first synthetic fiber and was discovered on February 28, 1935, by a former Harvard professor working at a DuPont Corporation research laboratory.[20]Nylon is also one of the most commonly used polymers in the market today and specifically, the most common used material used in the bristles of a toothbrush is nylon 6-12.[21]Chemists call it Nylon 6 because the adipic acid and hexamethylene diamine each contain six carbon atoms per molecule. Each molecule has over 100 repeating units of carbon, hydrogen, and oxygen atoms, strung in a chain. A single filament of nylon may have a million or more molecules.[22]Nylon was created when you combine the chemicals amine, hexamethylene diamine, and adipic acid. This mixture creates a polymer chain using a process in which individual molecules join together with water as a byproduct.[23]There has come of many beneficial features that nylon provides. As is polypropylene, nylon is known for its strength, heat resistance, chemical resistance and its wear resistance.[24]Types of nylon range depending on chemical properties. For example, commercially there are nylons which include nylon 6, nylon 4/6, nylon 6/6, nylon 6/10, nylon 6/12, nylon 11 and nylon 12. The numerical classification for these nylon types are derived from the number of carbon atoms in the diamine and dibasic acid monomers used to manufacture it. Not only is nylon 6-12 used in toothbrush bristles, but they also appear to be the bristles in paintbrushes, eyeliner, and other makeup brushes. Tynex, a type of DuPont nylon filament, is a type of 6-12 nylon. Tynex 612 is not affected by chlorinated solvents, petroleum hydrocarbons, ester solvents, or detergents.[25]Some of these nylon filaments are not permanently affected by continuous exposure to temperatures up to 65°C but do slightly degrade on long exposure at high temperatures. Over several months at 100°C, they begin to show slight loss in strength and as the temperature increases, degradation increases. Melting point of this type of nylon is approximately 212°C.[26]Nylon 6/12 is an excellent candidate material for applications requiring good physical properties, high heat resistance, moisture and chemical resistance and good dimensional stability.
In conclusion, for the production of toothbrushes synthetic materials used in the industry has gone a long way. Fortunately, because of the technological advancement in the world over time, chemists have introduced polymer based resin products that have changed the way we think plastic and how they are made today. Most toothbrushes are made with plastics such as polyethylene, polypropylene and nylon bristles. The problem is that the use of plastics and how the materials are derived, there will be a day in time where we can only use so much fossil fuel to create products before we run dry. There can only be so much room in our environment to dump plastics into designated landfills. The development of the toothbrush has improved and chemists, scientists, and designers continue to find more alternative routes to create a far more sustainable material for toothbrushes and in other products that use plastic. We are very fortunate to be in a day in time where technology is everywhere. Young students, and all alike are the future and all it takes is the idea that there is a better way to produce something which leaves our own creativity to take over. For now, we can only hope to discover new methods to develop a toothbrush that can either be completely recyclable, that can interchange the unusable, so that companies use less material, but yet still end up with a product that can last a lifetime.
Sources Cited
"Biological Degradation of Plastics: A Comprehensive Review."Biological Degradation of Plastics: A Comprehensive Review. N.p., n.d. Web. 13 Mar. 2014. <http://www.sciencedirect.com/science/article/pii/S0734975008000141>.
“DuPont Tynex® 612 Nylon Filament.” http://www2.dupont.com/Filaments/en_US/assets/downloads/Toothbrush/DuPont%20Tynex%20612.pdf/. PDF file.
Kumar, Jayanth V. (2011). "Oral hygiene aids". Textbook of preventive and community dentistry (2nd ed.). Elsevier. pp. 412–413.
Mark, H. F. Encyclopedia of Polymer Science and Technology. Hoboken, NJ: Wiley-Interscience, 2011. Print.
"Oil and Natural Gas History, Education Resources, Museum News, Exhibits and Events."AOGHS. The American Oil & Gas Historical Society, n.d. Web. 13 Mar. 2014. <http://aoghs.org/oil-and-natural-gas-petroleum-products/petroleums-nylon-fiber/>.
Panati, Charles. Extraordinary Origins of Everyday Things. New York: Harper & Row, 1987. 208-09. Print.
Samadi, Dr. David B. "Dental Hygiene Important for Whole Body, Not Just Your Smile."Fox News. FOX News Network, 28 Mar. 2012. Web. 13 Mar. 2014. <http://www.foxnews.com/health/2012/03/28/dental-hygiene-important-for-whole-body-not-just-your-smile/>.
[1]“Dental Hygiene Important for Whole Body, Not Just You Smile,” http://www.foxnews.com/health/2012/03/28/dental-hygiene-important-for-whole-body-not-just-your-smile/
[2]Panati, Charles.Extraordinary Origins of Everyday Things. HarperCollins. pp.208–209.
[3]Kumar, Jayanth V. "Oral hygiene aids”. Textbook of preventive and community dentistry (2nd ed.). Elsevier. pp. 412–413.
[4] “History of Dentistry,” http://inventors.about.com/od/dstartinventions/a/dentistry_2.htm
[5] Kumar, Jayanth V. "Oral hygiene aids". Textbook of preventive and community dentistry (2nd ed.). Elsevier. pp. 412–413.
[6] R.B. Seymour, Polymer science before & after 1899: notable developments during the lifetime of Maurtis Dekker, J Macromol Sci Chem, 26 (1989), pp. 1023–1032
[7] “Biodegradation of Low-Density Polyethylene (LDPE) by Mixed Culture of Lysinibacillus xylanilyticus and Aspergillus niger in Soil,” http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0071720
[8] “The ABC of polyethylene,” http://www.plasticseurope.org/information-centre/education-portal/resources-room/abc-of-plastics/the-abc-of-polyethylene.aspx
[9] “The ABC of polyethylene,” http://www.plasticseurope.org/information-centre/education-portal/resources-room/abc-of-plastics/the-abc-of-polyethylene.aspx
[10] Shah AA, Hasan F, Hameed A, Ahmed S. Biological degradation of plastics: a comprehensive review. Biotechnol Adv 26: 246–265.
[11] “Raw Materials – Polymers,” http://www.bpf.co.uk/plastipedia/polymers/default.aspx
[12] “Plastic Properties of High Density Polyethylene (HDPE),” http://www.dynalabcorp.com/technical_info_hd_polyethylene.asp
[13] Karian, Harutun G., Handbook of Polypropylene and Polypropylene Composites, Revised and Expanded (2nd Ed.)
[14] “Polypropylene (PP),” http://www.bpf.co.uk/plastipedia/polymers/pp.aspx
[15] Karian, Harutun G., Handbook of Polypropylene and Polypropylene Composites, Revised and Expanded (2nd Ed.) pg. 25-26
[16] Karian, Harutun G., Handbook of Polypropylene and Polypropylene Composites, Revised and Expanded (2nd Ed.)
[17] “Polyplastics: Solution Platform for Engineering Plastics,” www.polyplastics.com/en/product/lines/diff2pom/
[18] Karian, Harutun G., Handbook of Polypropylene and Polypropylene Composites, Revised and Expanded (2nd Ed.) (pg. 16)
[19] Karian, Harutun G., Handbook of Polypropylene and Polypropylene Composites, Revised and Expanded (2nd Ed.) (pg. 25)
[20] “Nylon, a Petroleum Polymer,” http://aoghs.org/oil-and-natural-gas-petroleum-products/petroleums-nylon-fiber/
[21] Palmer, R. J., Polyamides, Plastics. Encyclopedia of Polymer Science and Technology.
[22] “Nylon, a Petroleum Polymer,” http://aoghs.org/oil-and-natural-gas-petroleum-products/petroleums-nylon-fiber/
[23] “Nylon, a Petroleum Polymer,” http://aoghs.org/oil-and-natural-gas-petroleum-products/petroleums-nylon-fiber/
[24] “Nylon 6/12 (PA) — Polyamide 6/12,” http://www.rtpcompany.com/products/product-guide/nylon-612-pa-polyamide-612/
[25] “DuPont Tynex® 612 Nylon Filament,” http://www2.dupont.com/Filaments/en_US/assets/downloads/Toothbrush/DuPont%20Tynex%20612.pdf
[26] “DuPont Tynex® 612 Nylon Filament,” http://www2.dupont.com/Filaments/en_US/assets/downloads/Toothbrush/DuPont%20Tynex%20612.pdf
Luayo Zhang
DES 40a, winter 2014
Research Paper
Professor Christina Cogdell
Embodied Energy in The Life Cycle of Toothbrushes
Toothbrush is one of the most important oral cleaning tools. Everyone has his or her own toothbrush, which would usually be replaced at least every 4 months. This means toothbrush is in a huge demand globally. There are millions of toothbrushes being made and shipped everyday. Manufacturing of toothbrushes dominates a large part of energy usage. Shipping, recycling, and discarding toothbrushes also relate to energy consumption. Although toothbrush is a small product, its production scale is quit large. Studying energy that is embodied in the life cycle of toothbrushes maters because the process from manufacturing to discarding toothbrushes requires a significant amount of energy, which could be reduced through better designs. Starting from the materials that are used in manufacturing toothbrush, I went through different stages of its life cycle , such as manufacturing, transportation, use, recycling, and waste management. I found out that most energy is consumed in the processes of manufacturing, transportation, and recycling.
Manufacturing and Recycling:
The materials that are used in making toothbrushes are mostly plastics, which require energy to be synthesized. The main materials are polypropylene, polyethylene and Nylon. Polypropylene and polyethylene is usually used in making handles. Nylon, specifically nylon 6, is the main material of bristles. In Hamman’s report Energy of Plastics, he indicates that: “About (8.0 x 1010 kg)(4.5 x 107 J/kg) = 3.6 x 1018 J of energy were diverted to polyethylene-based plastics in 2008.” (Hamman). Producing 35 ounce (1 kg) polyethylene requires 12.5 kilowatt-hours (4.5 x 107 J). If a toothbrush handle weight 0.3 ounce, preparing for making a polyethylene handle requires 0.11 kilowatt-hours. According to the report The Propylene Chain by Office of Energy Efficiency and Renewable Energy, when one pound of polypropylene is made it will consume 23,898 Btu, which equals to 7 kilowatt-hours. If polypropylene is going to be used as the material of toothbrush handle, again the handle averagely contains 0.3 ounces polypropylene, making one toothbrush handle will take about 0.06 kilowatt-hours. According to the research of Assessing Energy Requirements and Material Flows of Selective Laser Sintering of Nylon Parts by Telenko and Seepersad, the specific energy consumption of nylon is 85 MJ/kg. After converting and calculation, it turns out that producing 1 ounce nylon will take about 0.7 kilowatt-hours. Usually a toothbrush contains less than 0.1 ounce nylon, 0.07 kilowatt-hours will be needed when papering for one toothbrush. While toothbrushes contain less nylon than polypropylene, nylon needs more energy than propylene to be synthesized. The synthesis of materials for making one toothbrush with polyethylene handle will use 0.18 kilowatt-hours, but only 0.13 for making one with polypropylene.
Energy embodied in manufacturing toothbrushes is closely related to their manufacturing plants. Taiwan Turnkey-Project Information website, provides detailed information of machines that involve in the process of toothbrush manufacturing plant. Usually a toothbrush manufacturing plant, works 8 hours daily, requires 2 injection molding machines, 1 hot stamping machine, 6 toothbrush tufting machines, and 2 bristle trimming machines. The injection-molding step needs to be completed using injection molding machines. The website shows that a injection molding machines and its related equipments can make up to 15,360 toothbrush handles in 8 hours. During these 8 hours, 160 kilowatt-hours will be consumed. In the next step, air-pressure hot stamping, the machines can produce 12,000 pieces in 8 hours by consuming 6 kilogram-hours energy. When 6 tufting machines work together, 15,000 pieces toothbrush will be processed and 8.4 kilowatt-hours will be used. The trimming machine can trim 28,800 pieces in 8 hours using 6 kilowatt-hours. In the last step, the packing machine will consume 24 kilowatt-hours in 8 hours. If a toothbrush manufacturing plant worked one day for 8 eight hours, at least 15,000 toothbrush could be made and 204 kilowatt-hours would be consumed. That’s 0.013 kilowatt-hours per toothbrush. Injection molding is the major step that takes up 89% of the whole process. The injection molding machines are high energy consuming because of the heat regions, which is the main component of the machine, responsible for changing the shape of the plastics.
Transportation:
Toothbrush shares the same as transportation method with other the small products. Since there is not specific information about energy consumption of transportation of toothbrushes, I am trying to approach this problem in a general way. According to Dr. Jean-Paul and Dr. Claude, “Almost all transportation modes depend on a form of the internal combustion engine, with the two most salient technologies being the diesel engine and the gas turbine, since they are the lynchpin of globalization” (Jean-Paul, Claude) It indicates that toothbrushes are shipped in the same way—in vehicles powered by fossil fuels. “Gasoline produces around 46,000 Btu per kilogram combusted, which requires from 16 to 24 kg of air” (Jean-Paul, Claude). That means one ton of gasoline could produce about 13,000 kilowatt-hours. The most energy consuming shipping method is maritime shipping, which most likely used by transportation of toothbrushes since most of toothbrushes are made in China and needed be distributed across ocean to western world. According to The Geography of Transportation Systems website, a normal size container ship will use 225 tons of fuel per day when it’s traveling in a normal speed (45km/hour). If there was a ship transporting toothbrushes from factory in China to USA, it would travel at least 11,572kms and take 10 days. The ship would consume 2,250 tons of fuel and 2.9x107 kilowatt-hours would be used.
Use:
Since many of the toothbrushes are made for use manually except for those electric ones, most of toothbrushes don’t require additional energy input. The only energy source that is involved when people are using manual toothbrushes is the kinetic energy generates by human bodies. This kind of energy varies on different people, and it’s hard to be measured, but what could be measured is the energy consumption by electric toothbrushes. According to Home Energy Use Guide, an electric toothbrush’s approximate wattage is only 1 watt. It only takes 0.001 kilowatt-hours while using it for one hour. Usually people use their toothbrushes twice a day, 6 minutes total. The energy consumption of electric is very low each time when the toothbrush is used.
Recycling:
The embodied energy in toothbrush made from recycled plastic is only about half that of the in ones that are made from virgin materials. Polypropylene and polyethylene as main materials of toothbrushes are also main materials that would be recycled. According to the ImpEE project of the Cambridge-MIT Institute and University of Cambridge, the process of recycling goes into steps like: “used plastic, polymer collecting and sorting, recycled plastic granules, plant for use of recycled plastics, then products from recycled plastics in the end”. The project also shows the specific embodied energy of recycle polypropylene and polyethylene: “PP 75-83 MJ/Kg, PET 79-88 MJ/Kg. Recycled PP about 35-45 MJ/Kg, recycled PET about 60-64 MJ/Kg”. If toothbrushes are made of recycle plastics, factories could save up to 50% of energy in the manufacturing process. While recycled materials seem to use lower energy than the virgin materials, the project indicates that: “the lower price reflects the lower quality of the recycled material, limiting its use”. It’s a challenge to reducing energy usage while maintain the quality of the products that made from recycled plastics.
Waste Management:
Since the materials that are used to make toothbrush are recyclable, used toothbrushes can usually be recycle so that waste management follows almost the same aspects of toothbrush recycling. There isn’t specific information of energy that I’m able to find during my research, probably because most of the energy goes into recycling but not discarding the toothbrushes. Waste management could be part of the recycling process that mentioned in the previous paragraph—the step of polymer collecting and sorting.
During the life cycle of toothbrushes, the process of manufacturing, shipping, and recycling are using significant amount of energy, while the use and waste management are not consuming a lot. In the processes of preparing materials and manufacturing, the total energy consumption is 0.193 kilowatt-hours for each polyethylene handle toothbrushes and 0,143 kilowatt-hours for each polypropylene handle ones. In the transportation process, fossil fuel is the main energy source that supports the whole process. The energy consumption of container ships that are used to transport goods like toothbrushes is quite immense and needs to be noticed. Manual toothbrushes don’t require additional energy when they are used. Electric toothbrushes require little energy as well. When used toothbrushes being recycled, it only takes half of the energy that is used in producing toothbrushes from virgin materials. Waste management, usually counts into part of the recycling process, in charge of mainly collecting and sorting polymer. From the perspective of energy consumption, a better-designed toothbrush should be made in materials that require less energy, such like polypropylene, but no polyethylene. Recycled materials are also a good choice since they can save energy up to 50%, but their quality needs to be improved in order to complete with virgin materials. Further more, toothbrushes could be made locally so that a large amount of energy could be saved from the process of transportation.
Works Cited
"-Toothbrush Manufacturing Plant." -Toothbrush Manufacturing Plant. N.p., n.d. Web. 12 Mar. 2014. <http://turnkey.taiwantrade.com.tw/en/Content.aspx?ID=29>.
Rodrigue, Jean-Paul, and Claude Comtois. "Transportation and Energy." Transportation and Energy. N.p., n.d. Web. 12 Mar. 2014.
<https://people.hofstra.edu/geotrans/eng/ch8en/conc8en/ch8c2en.html>.
Rodrigue, Jean-Pual, and Claude Comtois. "Maritime Transportation." Maritime Transportation. N.p., n.d. Web. 12 Mar. 2014. <http://people.hofstra.edu/geotrans/eng/ch3en/conc3en/ch3c4en.html>.
"Home Energy Use Guide." Salem Electric, n.d. Web. <http://www.salemelectric.com/residential/pdfs/energy_saving_tips/home_energy/HomeEnergyUseGuide.pdf>.
Hamman, Curtis W. "Energy for Plastic." Energy for Plastic. Stanford University, 24 Oct. 2010. Web. 12 Mar. 2014. <http://large.stanford.edu/courses/2010/ph240/hamman1/>.
The ImpEE Project, Recycling of Plastics. The ImpEE Project. The Cambridge-MIT Institute and University of Cambridge, n.d. Web. <http://www-g.eng.cam.ac.uk/impee/topics/RecyclePlastics/files/Recycling%20Plastic%20v3%20PDF.pdf>.
Telenko, Cassandra, and Carolyn Conner Seepersad. Assessing Energy Requirements and Material Flows of Selective Laser Sintering of Nylon Parts. Mechanical Engineering Department The University of Texas at Austin, n.d. Web. <http://www.me.utexas.edu/~ppmdlab/files/Telenko_SFF2010_Manuscript_FINAL.pdf>.
"The Propylene Chain." Energy and Environmental Profile of the US Chemical Industry. N.p.: Office of Energy Efficiency & Renewable Energy, n.d. 83-103. Web. <http://www1.eere.energy.gov/manufacturing/resources/chemicals/pdfs/profile_chap3.pdf>.
Nazgol Mojab
March 13 2014
DES 40A
Pro. Christina Cogdell
Wastes and Emissions in the Product Life Cycle Toothbrush
While most consumers only interact with a finished, marketed product, there is much more to a product than when it is finally purchased. In light of the current energy and environmental crisis, it is essential to understand and measure how a product, though it’s development, manufacturing, and distribution, impacts the environment. By measuring the total energy used to produce a product, we can reduce energy waste and costs and waste in the current and future design processes of consumer products. The calculation of a product’s manufacturing energy use, or it’s “embodied energy” , includes the acquisition of the raw materials, the processing of the raw materials, the electricity during manufacturing, processing, and distribution, as well as the energy required to recycle or remove the product’s manufacturing waste. Every consumer good has some energy costs from its lifecycle that can be measured and potentially, improved upon. Even something as seemingly common and simple as a toothbrush has embodied energy that can be tracked, measured, and hopefully, made more efficient.
While the toothbrush is a very simple product in terms of its design, the main materials, mostly plastic based, for making a toothbrush are not environmentally friendly. Although there are some plastics that are recyclable, plastic does not easily or quickly biodegrade. During it’s manufacturing, one toothbrush causes 1.5 kilograms of waste. In addition, 94% of the materials extracted for use in manufacturing durable products become waste before the product is manufactured.[1] There is no specific source to tell you what specific waste though. Since the toothbrush requires replacing regularly, there is not only its type of waste challenge, but a high volume of waste to be dealt with. Ten handles of toothbrushes are made every 35 seconds, that works out to 27000 handles in 24 hours, so the 100% recyclable brand can make a huge impact. This supply is to keep up with the demand. Under the toothbrush’s current design and materials, there is a lot of potential improvement in it’s “embodied energy” calculations, as well as environmental impacts, if it’s disposal element were redesigned.3 It is this problematic waste issue that makes toothbrushes environmentally challenging.[2]
Polypropylene is one of the materials that is used in toothbrush. The toothbrush’s handle is made from polypropylene (#5). Polypropylene is a synthetic resin that is a polymer of propylene. It has been very effectively applied to the forming of fibers due to its good particular strength. Its resistance to high heat makes it commonly used for injection molding. The injection molding process has different stages including clamping, injection, and cooling. The process of injection molding for making a toothbrush starts with a vacuum that sucks the pallet of plastic up into the injection mold machine. The machine melts them up into some kind of plastic dough, then injects it into a stainless steel mold for maintain toothbrush handle’s at once. I faced some difficulties to track the emissions come from the injection molding, but what I think is injection molding is a high pressure and high-speed process, and a great deal of energy and heat is required which can be the waste of this process. What toxic gases release during this process? The general answer is that the CO yields from burning PP under different fire conditions [3]. Graph 1 shows that under well-ventilated condition the amount of CO that is produced is less than 0.1 grams per gram of polypropylene burns. 70% of carbon emissions come from resin manufacturing, and about 25% from our own facilities----representing mainly electrical use in injection and blow molding. Another 5% of the total emissions come from other services like logistics ---transporting raw materials to our plants and products to customs. [4] Also, in certain situations with some plastics, toxic fumes may be released during the molding process, but it depends on that specific plastic. To this point polypropylene is the most harmless plastic. There are so many studies over different plastics, and weather they are toxic or not, but it's very hard to say whether we should be worried from a health point of view about PP or not. Today, polypropylene demand is about 40milion t/y with a market share, among all the thermoplastic material, of about 26%, second only to polyethylene, which represents 39% of the market share. The expected annual growth in the next ten years is about 6%. Polypropylene is one of the most acceptable thermoplastic resins for a broad range of applications. This unique material can be steam-sterilized or autoclaved without damage and challenges environmental tension especially when subjected to most chemical tests.[5] CO2, NOx and SO2 emissions associated with plastic production. VOCs are likely emitted by thermal degradation of plastic polymers. Several species of VOCs emitted from melted plastics are concerned to be toxic.[6] Studies show that the potential for exposure to chemicals in the thermoplastic processing is very high, but not any accurate information is available. They don’t mention what chemicals release during this process, but analysis of national mortality data by occupational group shows and further of male bladder cancer deaths among plastics goods makers and further of female lung cancer registrations among plastics workers during this process. Polymer breakdown can happen when thermal processing is poorly controlled and recommended, leading to the potential release of airborn toxins, and resulting in irritation to the eyes, nose, and lungs.[7] Nylon 4-6 is what makes the bristle of the toothbrush, which is another type of plastic (melting temperature is 194 to 265). Hand of each handle has up to fifty-six holes for bristles. They melt colorful rubber pallets. They pumped liquid rubber into the mold with a white toothbrush handles, then press the rubber into the handles to form a grip. They use a semi clear plastic to produce another type of grip; one is softer and more pliable. Its called the gummy brush because the grip really does feel a bit like one of those gummy candies Then the machine selects between twenty three to twenty four bristles for each hole in the brush. With fifty-six holes per toothbrush, that adds up to over 1300 bristles for each brush. Many companies that use plastics in their products don’t provide an actual information of its manufacturing and processing because I was unable to find the waste of the nylon in manufacturing a toothbrush.
Moreover, packaging is a significant undeniable feature. It requires more resources such as plastic to create the packaging. Most manufacturing companies admit that they waste resources in the simple packaging of their goods. Usually packaging consists of a plastic and cardboard. It is like a whole other process. Because once you create a product, it creates the need for a whole other product just to be able to distribute it. Most of the time, however, the packaging has a lot do with the sales, distribution, and transportation. Packaging accounts for the largest share of the market segment with 37% of all plastic consumed, but I wasn’t able to find the specific number of waste for packaging toothbrushes.[8]
Since polypropylene is recyclable, Preserve Company, which is trying to reduce the harm caused by the industrial age, represent a program called “Gimme 5”. They produce plastic products from polypropylene recycling waste (#5) such as toothbrush handles. Their recycled plastic #5 uses at least “54 percent less water than virgin polypropylene, 64 percent less greenhouse gases (in CO2 equivalents) than virgin polypropylene, 75 percent less oil than virgin polypropylene, 48 percent less coal than virgin polypropylene, 77 percent less natural gas than virgin polypropylene, 46 percent less electricity than virgin polypropylene” [9]. Preserve uses life cycle inventory (LCI) datasets to detail the inputs and outputs of recycled and virgin polypropylene – everything used to make polypropylene as well as all the waste created by the manufacturing process (including water usage, energy usage, pollutants, etc.).[10] The amount of the polypropylene produced is 580 thousand tons, and the amount that recycled is 130 thousand tons. Carpeting and battery industries have long been active in developing recycling uses for polypropylene waste. The Carpet America Recovery Effort (CARE) reports that its partners have recycled materials use in the manufacture of carpeting. However, even within their activities, the amount of polypropylene in their recycle streams has dropped from 22% in 2006 to 8% in 2007 and 2008. Battery Council International (BCI), a similar organization for the battery industry, describes ho 97% of batteries sold I the USA are recycled, but the driving force is the recovery and reuse of the lead. The polypropylene cases comprise only a small percentage of the total weight but this polypropylene is recycled back into new plastic cases.[11]
Concerns over the impact of the growth of world’s population on the demand for raw materials and energy resources have risen. Solid waste has become a significant problem in most of the developed countries. If every American changes his/her toothbrush every three months, as dentists recommend, that adds up to almost 100 million pounds dumped into landfills.[12] Plastic solid waste (PSW) is derived from oil and has a recoverable energy, in some cases comparable to other energy sources. Direct burning via one or two stage combustion technologies can certainly reduce the volume of PSW as well as the dependence on fossil fuels, which as a result can lead to a better protection of natural resources and combined waste management systems. It is very important to consider recycling and energy recovery methods in plastic manufacturing and changing facilities. This is only considered a very functional way of waste treatment, when material recovery processes fail due to economical constrains. Plastic materials possess a very high calorific value (when burned); especially when considering that they are derived from crude oil. Since the heating value of plastics is high, they make a convenient energy source. Producing water and carbon-dioxide upon combustion make them similar to other petroleum based fuels.[13]
It was very challenging to track down specific numbers for every single materials in toothbrush since plastic is not eco friendly to our environment and there are more into it rather than just find a number. Thus judging by the analysis of each factor of toothbrush and total waste emissions, I feel it is fair to assume that toothbrush is obviously not waste-free, but still not extremely harsh to environment since the materials are mostly recyclable. To track down the numbers for the process and manufacturing, there is a company called Nexant. Their job is to provide you the information for your product’s process. They estimate the waste and emissions based on your materials and give you a report to calculate your waste.
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[1] Kutz, Myer. Applied Plastics Engineering Handbook: Processing and Materials.Amsterdam: Elsevier/William Andrew, 2011. Print.
[2] Leigh-Guerin, Alison. "Brush Up." Natural Health 37.7 (2007): 112. Academic SearchComplete. Web. 2 Mar. 2014.
[3] Stec, Anna A., and Jennifer Rhodes. "Smoke And Hydrocarbon Yields From Fire Retarded Polymer Nanocomposites." (2011): 295-300.
[4] Naitove, Matthew H. "Sustainable Injection Molding: Amcor Looks At The Big Picture." Plastics Technology 59.3 (2013): 42-44.
[5] Rajendran, S, et al. "Review Of Life Cycle Assessment On Polyolefins And Related Materials." (2012): 159-168
[6] Yamash*ta, Kyoko, et al. "Compositions Of Volatile Organic Compounds Emitted From Melted Virgin And Waste Plastic Pellets."
[7] Unwin, John, et al. "Airborne Emissions Of Carcinogens And Respiratory Sensitizers During Thermal Processing Of Plastics." (2013): 399-406.
[8] Brems, Anke, Jan Baeyens, and Raf Dewil. "Recycling And Recovery Of Post- Consumer Plastic Solid Waste In A European Context." (2012): 669-685
[9] "Recycle." Recycle. N.p., n.d. Web. 13 Mar. 2014.
10Kutz, Myer. Applied Plastics Engineering Handbook: Processing and Materials. Amsterdam: Elsevier/William Andrew, 2011. Print.
11 Al-Salem, S.M., P. Lettieri, and J. Baeyens. "Recycling And Recovery Routes Of Plastic Solid Waste (PSW): (2009)
13 Al-Salem, S.M., P. Lettieri, and J. Baeyens. "Recycling And Recovery Routes Of Plastic Solid Waste (PSW): (2009)
