Design Life-Cycle
assess.design.(don't)consume
Jennifer Jeon
DES40A
Professor Cogdell
7 December 2018
The Life Cycle of Nitrile Gloves: Materials
In industries ranging from food service to health care, professionals pervasively use nitrile gloves in their day-to-day use. Nitrile as a material is especially favored in industries in which cross-contamination poses a risk because of its contrasting durable yet disposable nature. Due to its chemical makeup and the raw materials associated with nitrile gloves, such gloves are resistant enough to offer adequate protection against most mild chemicals and infectious materials. In the production of nitrile gloves, synthetic materials are used as a way to preserve raw materials and circumvent human allergies, and thus allows for a glove that is now the universal standard in protecting against potentially hazardous material. Specifically, the main materials used in making nitrile gloves are acrylonitrile and butadiene, which is where nitrile rubber sources its unnatural durability and resistance to substances such as oil or blood.
Nitrile gloves were first introduced as an alternative to latex gloves, which were universally used for medical procedures and examinations. Latex naturally occurs in the rubberwood tree Hevea Brasiliensis, which is native to Amazon rainforests. However, with the popularity of latex that includes not just gloves, but also balloons, condoms, and other rubber-based materials for commercial use, such trees were overharvested and inflated the price of latex (Rainforest Alliance). Due to the increasing demand and following rapid depletion of naturally recurring latex, scientists sought to source a new material in order to preserve latex. Nitrile gloves are made in a similar fashion as latex gloves; however, nitrile gloves are made using synthetic materials.
One component of the synthetic material used in nitrile gloves is acrylonitrile, an organic compound that contributes greatly to nitrile gloves’ unnatural resistance to fluids such as blood and oil. In gloves with higher acrylonitrile content, they possess higher strength and lower permeability to gases (Britannica - nitrile rubber). On its own, acrylonitrile is a poisonous compound with molecular formula C3H3N. It does not naturally occur; it is a colorless liquid with distinguishable, onion-like odor. The Environmental Protection Agency (EPA) classifies acrylonitrile as a probable human carcinogen and warns consumers that it may be linked to lung and prostate cancer, although contact with pure acrylonitrile has also caused mucous membrane irritation, headaches, dizziness, and nausea (PubChem). Acrylonitrile is synthesized through what is known as the SOHIO acrylonitrile process, named after the scientists and engineers who developed this process at Standard Oil of Ohio, an oil company part of the Standard Oil Company. In the SOHIO process, the main raw materials used are naturally recurring propene, ammonia, water, and air. These materials, along with a catalyst - commonly bismuth phosphomolybdate (Britannica - bismuth) - are passed through a fluidized bed reactor only once. They are kept in the reactor for only 2 - 20 seconds, before being exposed to aqueous sulfuric acid, effectively dissolving the reactants. The products of this reaction are acetonitrile, acrylonitrile, and carbon oxides, and hydrogen cyanide. The unused products are either incinerated or released into the atmosphere. Then, excess water is removed and acrylonitrile and acetonitrile are separated through distillation. Acetonitrile is used as a solvent in the purification of butadiene, the second main component of nitrile.
Butadiene is the other organic compound essential in creating nitrile rubber; butadiene is used to ensure that nitrile gloves retain its elasticity and tear resistance. The butadiene used in the production of nitrile is known as 1,3-Butadiene, with formula C4H6. In its pure form, it is an odorless, colorless, and hazardous gas. Human exposure to butadiene gas can cause irritation in the eyes and throat; it is also a common air pollutant as motor vehicle exhaust is one of the more common sources of butadiene. Like acrylonitrile, it is also classified as a human carcinogen by the EPA (Pubmed). Due to its synthetic nature, butadiene is also made in a laboratory setting. Butadiene is a byproduct of the production of ethylene (C2H4), which happens through steam cracking. Steam cracking is the petrochemical process in which saturated hydrocarbons are broken down into smaller, usually unsaturated hydrocarbons (sciencedirect); it is the primary means of producing ethylene. Ethane is placed into a pyrolysis (also known as steam cracking) furnace along with steam and is then “cracked” at high temperatures that range from 1450 °F to 1525 °F. From this process, the pyrolysate - also known as the product from pyrolysis - is composed of hydrogen, ethylene, propylene, and butadiene. The pyrolysate then undergoes compression and distillation in order to separate the hydrogen, methane (C1 compounds - compounds with only one carbon atom), ethylene (C2 components - compounds with only two carbon atoms), and propylene (C3 compounds with only three carbon atoms); this leaves the crude, unpurified butadiene, which has four carbon atoms in its compound. Butadiene is then purified through extractive distillation, which is needed to separate larger quantities of heavier hydrocarbons and because the volatility of butadiene and C5 components are similar; this means that they will evaporate at the same time at a similar rate. Acetonitrile, the byproduct of the synthesis of acrylonitrile, is mixed with both the butadiene and the C5 components separately, thus changing their relative volatilities (ACS). Then, normal distillation occurs and outputs highly purified butadiene that is ready for polymerization.
Together, the monomers acrylonitrile and butadiene undergo free-radical emulsion polymerization in order to create nitrile, a polymer. Acrylonitrile and butadiene are emulsified in water in trains of continuous reactors, which are large polymerization vessels (UWaterloo). In the production of hot nitrile rubber, the polymerization vessels are heated to 30 °C to 40 °C and are allowed to react with each other for 5-12 hours, which allows for a roughly 70% conversion into a full polymer. The latex is then congealed with calcium nitrate and aluminum sulfate in an aluminum tank, which is then washed and dried as crumb rubber. The raw material is yellow and the specific properties of the nitrile formed are dependent on the acrylonitrile content. For optimal low-temperature flexibility and solvent resistance, the acrylonitrile content is about 33%; however, the higher the acrylonitrile content, the more resistant the nitrile will be to nonpolar solvents (Sciencedirect).
With the nitrile formed, the material is ready to be coagulated into gloves in a factory setting. This is done by running ceramic, hand-shaped molds first through water and bleach to remove any residue in order to ensure that the final product is pristine. Then, the molds are dipped into calcium carbonate and calcium nitrate in order to help the materials stick onto the models. The molds are then engulfed in a tank of the newly-polymerized nitrile and heated at high temperatures to form the gloves. The gloves then undergo either chlorination or polymer coating so that they are easier to wear. In chlorination, the now-dried gloves are exposed to either chlorine gas or aqueous solution to make the material slicker. Polymer coating adds another layer of polymers so that the material is more elastic. In the past, cornstarch was used to powder gloves; however, the threat of allergies, cross-contamination, and its role as an impediment in healing open wounds has led to manufacturers to use more synthetic methods (AMMEX). The gloves are then stripped off of the molds and are dyed using pigments according to size. There is no universal color legend for the sizes of nitrile gloves, as it varies by manufacturer (Sciencedirect).
Nitrile gloves are pervasively used in medical facilities and should also correspondingly be disposed of in a way that is sustainable and in a way that does not pose as a biohazardous threat. Researchers at Cell Signaling Technology (CST) have noted that they use between three to upwards of ten pairs of gloves every day (Labconscious). Additionally, caregivers use nitrile gloves to prevent cross-contamination and spread of bacteria when providing medical care. Because of how doctors use nitrile gloves when in contact with potentially dangerous material, nitrile gloves used in these situations must be disposed of in hazardous waste bins. However, when working with non-hazardous material, professionals will usually dispose of them in the trash, which will usually lead to such gloves to either be thrown in landfills or incinerated. In a study conducted by CST, researchers concluded that they were throwing away 5,000 pounds of gloves a year. Kimberly-Clark Corporation, an American personal care corporation, formed an initiative in which Kimberley-Clark branded gloves can be sent back to the company, and then be repurposed for plastic-based objects.
Ultimately, nitrile rubber gloves are the industry standard in a variety of professional fields. The chemical composition and its synthetic nature fortifies nitrile in ways that rubber latex could never be. Acrylonitrile and butadiene both enable nitrile to be unusually resistant to oil, fuel, and hazardous chemicals. Compared to natural rubber and latex, nitrile rubber is more puncture resistant and is less likely to cause an allergic reaction.
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Kaitlyn Weycker
DES 40A
Professor Cogdell
6 December 2018
Nitrile Gloves Life Cycle: Embodied Energy
Nitrile is a versatile material used in a variety of industries all due to its hypoallergenic properties and ease of creation. This is especially true in industries that need to maintain cleanliness, as nitrile rubber gloves are easily disposed and acquired. Though they are prevalent in professional industries, nitrile gloves can be bought easily online and in department stores due to their ease of creation. Nitrile rubber is made entirely of synthetic materials, alleviating some pressure on the environment, and so the creation process relies on a series of refinement and synthesis. The vast majority of energy used within a the life cycle of a nitrile glove is consumed by the creation of the synthetic materials that create nitrile rubber. Due to the massive energy usage of the initial processes to create nitrile, the overall energy consumed in the life of a nitrile glove is high.
The creation and refinement of base materials accounts for the largest portion of energy consumption in the creation of nitrile gloves. The base materials used to create nitrile, propene and butadiene, are generated as a byproduct of steam cracking, which is a massive industry because all synthetic rubbers need materials from this process. So massive, in fact, that steam cracking facilities consume nearly 10% of the energy used by the entire chemical sector, even though steam cracking reactions last only milliseconds in modern facilities. The reason steam cracking constitutes such a massive portion of energy use in the chemical industry is because the process is necessary for the production of a variety of commonly-used materials. Additionally, steam cracking has been found to consume the most energy out of any single process in the chemical industry. In order to preserve confidentiality, very few articles have been published with exact values for the energy usage of an average steam cracking facility, though qualitative measurements are more willingly shared. Due to the massive energy consumption of the steam cracking process alone, very little energy is required to form and transport the gloves in comparison.
The formation of the gloves themselves is nearly entirely automated by factory machines, and so consumes a large amount of electrical energy. However, most industrial factories purchase electricity from the local electrical companies, which are fueled mainly by natural gas, adding to the overall energy consumed to create gloves. Alongside the automated facilities, glove factories must also hand test the finished gloves for impurities as regulated by the FDA. This involves filling each individual glove with water to check for holes and structural integrity. Once the testing is concluded, factory workers must also package and store the finished gloves. Nitrile gloves, especially the disposable versions, are packaged and transported in bulk due to the lack of shelf life and the fact they are not reusable. Overall this reduces the amount of labor and energy consumption of the delivery process as more gloves are delivered at once.
The energy required to transport nitrile gloves and their production components varies greatly, mainly due to how easily accessible the gloves are. One can purchase gloves in common department and cleaning stores, as well as online. Online accessibility increases the overall amount of transport required for the product to sell, as any manufacturer can sell their products worldwide. In contrast, the majority of energy used to dispose of the gloves is consumed in transportation, mainly by waste removal services. This is only increased if the gloves are classified as toxic waste, as there are fewer locations to dispose such material and the trucks would travel further. However, no matter the distance or method of transportation, the fuel and energy consumption of the vehicles pales in comparison to the consumption of producing the materials.
Nitrile gloves can be disposed of as hazardous waste, and go through a separate process of transportation, treatment, and disposal regulated by local governments, usually resulting in thorough incineration. Nitrile gloves are also often incinerated or dumped in a landfill, and most of the energy consumed in order to properly dispose of the gloves is used in transporting the material to the proper sites. Incineration is the most common procedure for disposing of nitrile gloves, and naturally requires much more energy than simply dumping the waste, but has a much lower risk of leaving harmful waste material behind than letting the gloves decompose. Despite this, both processes with current technology still leave behind non degradable, toxic, or otherwise environmentally harmful wastes.
Overall the vast majority of energy used to create nitrile gloves is consumed by the steam cracking processes, which consume such a massive amount of energy that the worldwide transportation of nitrile gloves makes hardly a dent in the overall consumption. Despite that fact, very few raw or natural resources are used to produce nitrile gloves, which reduces strain on the environment. Additionally, it is possible to cleanly dispose of the gloves, further reducing environmental impact, though they are often sent to landfills.
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Nitrile Gloves (Waste and Emissions)
Auboni, Poddar
DES 40A
Professor Cogdell
5 December 2018
The availability of disposable gloves is fundamental to accomplishing basic tasks in fields where protection and safety are a necessity. Selection of glove type varies on a wide scale; depending on the material, different levels of protection can be provided. In certain fields, such as the medical field, gloves made out of latex or nitrile tend to be a common choice due to the high durability and protection they provide. Because of latex allergies and the higher chemical and puncture resistance that nitrile provides, nitrile glove use specifically has been on the rise. Though nitrile is known to be a more expensive and slowly biodegradable material, nitrile gloves have become an essential tool in the medical field for its qualities in protection (“The Development of Nitrile Gloves”). In the interest of the environment and the desire to continue to use nitrile gloves, it is best to implement changes throughout the process of creating the gloves that will help reduce the levels of emission and waste released into the environment.
The materials that nitrile gloves are composed provide the qualities that make this a glove of choice as opposed to the others; it is important, however to consider what emissions are released from these raw materials to examine its effect on the environment. Nitrile, formally known as Nitrile Butadiene Rubber (NBR), is a synthetic rubber that contains no natural rubber latex (“Nitrile Rubber”). This copolymer is created through a chemical reaction between acrylonitrile and butadiene (“What is Nitrile Anyway?”). Acrylonitrile is released into the air and water by the chemical plants that use them. According to the Agency for Toxic Substances & Disease Registry, acrylonitrile evaporates quickly in the air. In water, acrylonitrile normally breaks down in one to two weeks, but this is dependant on the amount that is released. If high concentrations are released at once, for instance during a spill, acrylonitrile will take longer to break down. Though small amounts of acrylonitrile do tend to be found in the water and soil near manufacturing plants, overall acrylonitrile pollution is unlikely to have any significant effects on the global environment (“Public Health Statement for Acrylonitrile”). Most butadiene is released by air into the environment during production and disposal and generally only take six hours to break down. It evaporates easily in water and soil and does not build up in the environment, but can be involved in the formation of ground level ozone. Because of this, butadiene can have a negative impact but only on a small and local scale (“1,3-Butadiene”). Though these findings make it clear that the potential of these emissions impacting the environment is low, there is still action that can taken to improve what can be done with the waste. For instance, Harold R Sheely proposes recovering the waste materials of nitrile found in wastewater by using a method where, “the nitrile-solvent mixture is distilled to separately recover the solvent and nitrile product”, which essentially allows for the solvent to be recycled (“Treatment of Waste Water from Nitrile Production”). This is an example of how byproducts can be retrieved from waste and recycled for continued use. Analyzing what byproducts are released from the raw materials is helpful when considering improvements that can be made to minimize waste and harm in the environment; it also alludes to the possibilities for improvements that can be made within the manufacturing of gloves itself and its transportation process which imaginably releases a lot more emissions.
The manufacturing process of rubber gloves is intuitively understood to be a detailed process that requires a substantial amount of energy to fuel its mass production; with large amount of energy input comes large amounts of output, waste and emissions included. Many components that are necessary in the rubber industry produce byproducts that are released into the environment during the manufacturing stage of gloves. Two substances in particular are sulphur and zinc oxide. Facilities that process crude oil or natural gas often form raw sulphur and zinc is the most used metal in the rubber industry. These substances can be harmful to some water based organisms (“Processing of Rubber Materials”). Similarly, according to a study done on the, “Effects of Zinc-oxide Nanoparticles on Soil, Plants, Animals and Soil Organisms”, zinc-oxide has a negative effect on ecosystems. Water pollution is a common result of the production process which can easily be combated by specific maintenance by facilities. Glove manufacturers can clean the wastewater in their facilities to ensure that the water they release back to the environment is not more toxic than it was before (“Can Disposable Gloves Go Green?”). The most contributing byproduct of emissions released during manufacturing and transporting goods is the release of CO2 from use of fossil fuels. Oil, gas, and coal used in the rubber industry for the heating and production process and as a result, large releases of CO2 enter the atmosphere. Carbon black, for example, is a specific byproduct that is released during the combustion process in furnaces and is released into the air (“Processing of Rubber Materials”). Additionally, the emissions released during transportation of raw materials and final products contribute to the CO2 added to the atmosphere. These amounts are especially high because most glove factories reside in Southeast Asia, so gloves are shipped from facilities through ocean freight to reach destinations (“Start to Finish: The Disposable Glove Supply Chain”). Solutions such as establishing more local factories may help to reduce the amount of fuel needed because it helps eliminate distance. Another adjustment that can be made is further maximizing how many gloves can be delivered per shipment (“Can Disposable Gloves Go Green?”). While evaluating issues regarding waste and emissions that lie within the production and delivery process of nitrile gloves, it is just as imperative to consider what contributions the finished product make to the waste in the environment once it is ready to be disposed.
One of the main features of nitrile gloves is that it is to be designed to be disposed after a single use; with a product that calls for immediate disposal, analyzing what happens in that process is tremendously helpful in determining if adjustments can be made there to improve the effect nitrile gloves have on the environment. Generally, if a glove ends up contaminated, it is disposed the same way as the toxic material. Otherwise, nitrile gloves are either incinerated or found in landfills (“Ansell-Technical Center”). When nitrile gloves are thrown out into landfills, they remain intact and do not decompose. They gradually “shred” from exposure to the elements and sunlight, but they will not break down and disappear completely (“Processing of Rubber Materials”). A properly functioning incinerator should be able to consume all gloves and their byproducts. When nitrile gloves are incinerated, their byproducts include water and a small amount of carbon dioxide and other non-toxic chemicals. Therefore, incineration is considered the best form of disposal. The issue arises when gloves are being incinerated in a poor functioning incinerators. This leads to a release of hydrogen cyanide and carbon monoxide which are dangerous to the environment (“Ansell-Technical Center”). On the other hand, landfill decomposition will not form any toxic byproducts. The issue with landfills is the slow degradation rate of nitrile gloves. In 2013, Globus introduced the world's first biodegradable nitrile disposable glove. Rather than the usual rate of degradation of nitrile gloves, estimated to take hundreds of years, these gloves activate in landfills and take far less time (“Globus Introduces World's First Biodegradable Nitrile Disposable Glove”). Another form of action that helps minimizes the buildup of gloves in landfills are providing more recycling options in labs since nitrile is recyclable. In efforts to improve sustainability, the Kimberly-Clark Nitrile Glove Recycling Program was implemented at various university labs and provides recycling for nitrile disposable gloves. So far, this program has prevented 70,000 pounds of waste from landfills (“Kimberly-Clark Nitrile Glove Recycling Program”). Further installations of programs and products like these can significantly improve the state of landfills and overall maintenance of the environment, and shows that exploration of nitrile gloves can only improve what steps should be taken to move forward.
Nitrile gloves are an excellent resource for medical departments whose success is heavily determined by how safe and dependable their tools are. Nitrile glove serves as a top choice because of its durability and incredible resistance. It is a responsibility to consider what waste and emissions are released during the stages of nitrile gloves in order to determine what improvements can be made to preserve the state of the environment. Converting all of nitrile gloves into a biodegradable form, improving facilities management of their waste, and choosing to be mindful with transportation are just a few productive steps that can be made to ensure that these gloves can be available without the expense of severe damage on the environment. Examining all aspects of nitrile gloves at all its phases effectively guides thinkers in determining how one can enjoy the benefits of this product without it being at the expense of their ecosystem.
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