Angela Yuan
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Professor Cogdell
Design 40a
Raw Materials and other Related Information on Dry Food/Snack Packaging
The ultimate goal of packaging is the protection of food and minimization of food waste. These goals rely heavily on the materials chosen to do the job. Due to modern synthetic factory processing, there is an increasing detachment with the process and materials of our technologies. The origins and embodied energies of essential everyday items are not well understood anymore. Many earlier materials such as paper, cloth and glass are still used today, but the trends of modern food packaging are leaning heavily on a new material, plastic. &#;After World War II, polypropylene, polyester, and other plastic polymers were commercialized as films, sheet, and bottle materials&#; (Brody, 263). Plastic is one of the most popular and commonly used materials used in modern food packaging. Depending on the job, there are a variety of different plastics with their own respective properties of production, potential for recycling and establishment of waste. Plastic food packaging is largely dependent on the needs of the specific food product. From jars, bottles, films and trays, plastics are applied to a diverse range of packaging needs. On top of this, plastic can be made of numerous types of materials and the list is expanding and evolving everyday. Food companies tend to produce a variety of products with needs specific to their unique foods and so this becomes too broad of a topic with regard to plastic materials. Rather than one specific company, this group research targets the snack food genre exclusively. To focus the scope further, this group will clarify on the energies and materials of dry food/snack bag packaging, attempting to obtain a better understanding of its life cycle.
The long scientific names can be quite intimidating but beneath the shiny sheets of finished plastic lay the processed story of their raw materials. Currently, the vast majority of dry food packaging is simply variations on polyethylene polymers. This material has desirable characteristics such as strength, resistance to oxidation, cheapness and versatility. Polyethylene varies chemically to suite the rigidity preferences of the food product. Because a big factor in dry food storage is the preservation of crunchiness, high-density polyethylene (HDPE), ethylene vinyl acetate (EVA), and ethylene acrylic acid copolymers (EAAC) are just some less popular examples that can be found in smaller parts of packaging for foods such as crackers, cereals and other snacks. (Mullen, Mowery) Some snacks are also packaged with an extra plastic film in congruence to the stiffer polyethylene package for the quality of extra toughness and heat salability. This film is typically made of biaxially oriented polypropylene (BOPP). Variations on polypropylene by themselves are also popularly used as snack packaging. In summary, I have derived the major materials in snack packaging to be polyethylene and polypropylene, each with their unique properties.
Polyethylene (PE) is an extremely adaptable and varied material made of synthetic chained polymers derived from fossil fuel byproducts. It is a family of polymers based on ethylene (CH2 = CH2) that can be assembled into a variety of different styles of chains depending on the needs of the product being packaged. These chains can be linear or branched, homopolymer or copolymer. By manipulating the style of chain, polyethylene can take on denser or thinner crystalline characteristics (Hernandez). In the case of food packaging, low-density polyethylene and high-density polyethylene are used. Depending on the desired characteristics, any level of density in between can be made to best satisfy product needs. The raw polyethylene is delivered in granules and powders to special sites after the chemical production process. After the raw plastic material is delivered to the production site, it is combined with the necessary plasticizers and turned into processed plastic (Piringer, Baner, 10). Phthalates are commonly used as plasticizers; diethylhexyl phthalate (DOP) of which is the most widely used (Hernandez). The secondary material produced by this process forms the basis from which many varieties of plastics splinter off. Low-density polyethylene (LDPE) is a branched homopolymer version of the raw polyethylene. It is a plastic processed through the addition of radical producing initiators. This usually includes the addition of monomers into the chain. In the past, plant based materials were used to create the monomers but modern synthesis of monomers is exclusively fossil fuel based, using mainly oil, gas and coal. Low-density polyethylene is typically used in the form of film and utilized for its ability to resist puncture. For the production of stiffer high-density polyethylene (HDPE), the process is taken one step further by the use of metal oxide catalysts. Though most factories end there, sometimes, depending on the needs of the product, the processed plastics can be modified even further through a system called crosslinking. This step of the process however is difficult to explain regarding the chemical materials involved due to the highly specialized and often proprietary additives.
&#;It is especially difficult to make a definitive comprehensive list of all starting materials (positive list) used to make polymeric package materials by three dimensional crosslinking, which could be transferred into a product. In addition to the numerous oligomers coming from the combined intermediate steps there is a variety of combination possibilities and mixtures of polymer starting materials, together with the corresponding processing aids (catalysts, crosslinkers) and additives (stabalizers, plasticizers) which further complicate the inclusion of all these compounds into food regulations and quality analysis systems (Pirigner, Baner, 13).
This particular material-processing step may be considered a failing in my research, to find the minute traces of other chemicals and additives that individual companies may use. These additives become variables in the recycling process discussed later in this paper.
Polypropylene (PP) is a somewhat more limited material with regards to food packaging applications due to its proneness to low temperatures, though it does demonstrate useful qualities in its own right. It a good barrier against water vapor and has fat resistant properties, both of which are useful characteristics concerning snack/dry food packaging specifically. &#;Properties of polypropylene make it a useful polymer for many applications. Polypropylene can be UV-stabilized; reinforced with talc, minerals, or fibers; foamed; biaxially oriented; or combined with elastomers for applications in the automotive, packaging, textiles, construction, appliance, and medical industries&#; (Calafut, 93). Polypropylene is a synthetic material made by polymerizing propylene, which is a gaseous byproduct of petroleum refining. This raw material is then combined with a catalyst under certain heat and pressure to join together many propylene molecules to form one large molecule (Maier, Calafut, 3). It is then reacted with an organometallic transition metal catalyst and arranged into a chain with other polypropylene molecules. The most commonly used catalysts are Ziegler-Natta catalysts, which are heterogeneous combinations of magnesium chloride, alkylphthalates and alkoxysilanes. After the addition of these, the style of chain can then be oriented into whichever crystalline structure is best suitable for the dry food/snack product. At this point, the polypropylene is useful as a type of plastic with a good weight to strength ratio and high resistance to heat.
The next step of lamination and graphics printing is of huge concern to the graphic artist. Though there are many different style of graphic presentation on plastic snack/dry food bags, the most common methods include labels, headers or graphics carriers. Headers are extended seal areas at the top of a bag that allow space for the attachment of a paperboard graphic message. These parts are typically made of paper or cardboard. Labels are automatically attached preprinted labels that are typically made of the same material as the plastic bag, in this case, polyethylene or polypropylene (Kuhr). Graphics carriers require more materials and a slightly more complicated process as an additional layer is added to the packaging. The order from outer layer to inner layer is as follows: graphics carrier, printed image, adhesive layer, barrier layer, and optional sealing layer, respectfully. The graphics carrier is most commonly made of an extremely thin layer of oriented polypropylene (OPP) to protect the image beneath from scuffing and add a glossy finish to the aesthetics of the bag. Oriented polypropylene is a slightly modified version of the base polypropylene described earlier, chemically oriented into a certain fashion to maximize the crystalline reflective characteristic (Dunn). The next layer of the packaging is the printed graphic. Ink-jet printing is the most versatile and widely used method for food packaging. Several other older processes include, letterpress, flexography, lithography, hot die stamping, gold blocking and gravure. These techniques all depend on the porousness of the plastic surface though they all use similar solvent inks composed of volatile organic compounds (VOCs) (Paine, Paine, 49). Volatile organic compounds used in printing are manmade solvents of aliphatic hydrocarbons, ethyl acetate, glycol ethers, and acetone (Stoye, Marwald, Plehn). The next layer is the adhesive layer that binds the barrier surface with the graphics carrier. Higher quality adhesive laminates are typically made of a thick layer of casted molten polyethylene. Other cheaper adhesives are commonly based on polyvinylidene dichloride (PVDC or SaranTM). These layers are all combined and glued together with the barrier layer to create a finished and decorated food package (Dunn). For smaller snack packaging such as individually wrapped candies and cookies, a layer of acrylic is applied to the barrier layer (Hernandez). Acrylic is made of liquid polymer plastic similar to the family of polyethylene. Though it is able to express bright and vibrant designs, it is especially prone to scuffing and folding. Graphics and laminates add an extra layer of complexity to the production of snack food packaging.
Regarding the recyclability of plastics, two broad categories are typically used, those based on thermoplastic polymers and those based on thermoset polymers. Thermoplastics are made of threadlike chain molecules that are tangle together in a way that characterizes the ability to melt back into base material and harden when cooled. Most food packaging is made with thermoplastic polymers, of which both polyethylene and polypropylene are categorized under. The resulting phase of the glossy plastic is called the glass stage. This property allows for polyethylene packages to be easily recyclable as opposed to thermoset polymers that have been processed to an irreversible point (Krochta 870). Most thermoplastic polymers are recycled via pyrolysis, the process of bathing the plastic materials in a low oxygen corrosive environment. Today, a technique called fluid catalytic cracking (FCC) is used in the process of plastic pyrolysis. In one particular control experiment regarding HPDE and LDPE, Achilias, Roupakias, Megalokonomos, Lappas, and Antonakou use the popular FCC catalysts: silica-alumina, alumina and several types of zeolites. &#;The oil and gaseous fractions recovered presented a mainly aliphatic composition consisting of a series of alkanes and alkenes of different carbon number with a great potential to be recycled back into the petrochemical industry as a feedstock for the production of new plastics or refined fuels&#; (Achilias, Roupakias, Megalokonomos, Lappas, Antonakou, 542). This process results in a mixture of desirable liquid and gaseous products with varying rates of purity and quality. The reason for this variation and difficulty comes from the proprietary mystery additives that were discussed earlier in the paper. These extra additives that some companies use often contain chemicals that skew the purity of the end mixture, producing a lower quality recycled plastic blends. Yields and purity also range in percentage depending on the chemical bath and or other process used (Achilias, 538). Currently, the recycling of plastics is very much an experimental process; it is largely dependent on the firm/company that receives the waste and variables within the waste plastic. Criticism of plastic recycling has been received over the potentially lower quality &#;down cycled&#; plastic that is inevitably produced from the system. The perfect system for recycling plastics is still an elusive goal.
Different products rely on different variations of plastic to best ensure protection, quality and shelf life stability. The origins of materials have become lost to us as synthetic concoctions become further and further distanced from common knowledge. Within the realm of snack food bags alone, there are a myriad of styles and blends of plastics, made of countless chemically convoluted materials. Many see the abbreviations tacked onto the bottoms of familiar food item packages but the process and implications of the life cycle are lost to them. In summary, snack food plastics, like other food packaging plastics, are synthetically made and chemically derived. The chemicals used are fossil fuel based or petroleum byproducts. Fortunately, many of these types of plastics have a high potential for recyclability though the process&#;even now&#; is far from sustainable. The word plastic becomes meaningless with regards to the materials and energies required to mass-produce this immensely popular material. It is therefore important to educate oneself on the raw materials of food packaging. The materials however, should not go without proper explanation of process, if this is to be a quality life cycle analysis. The energies needed to refine, produce and transport these materials by machine will be discussed in the second part of this group research.
Bibliography
Achilias, D. S., et al. "Chemical Recycling of Plastic Wastes Made from Polyethylene (LDPE and HDPE) and Polypropylene (PP)." Journal of Hazardous Materials 149.3 (): 536-42. ScienceDirect. Web. 8 Mar. . <http://dx.doi.org/10./j.jhazmat..06.076>.
Brody, Aaron L. Food Packaging Trends. N.p.: Taylor and Francis Group, . Print.
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Min, Sea C., Young T. Kim, and Jung H. Han. Packaging and the Shelf Life of Cereals and Snack Foods. N.p.: Taylor and Francis Group, . Print.
Mullen, Michael A., and Sharon V. Mowery. Packaging. New York: Marcel Dekker, . Print.
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Hualei supply professional and honest service.
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Ilene Eng
Professor Cogdell
Des 40A
13 March
Fabricating Plastic Snack Packages
Snacks are sold all over America. They are crunchy, crispy, sweet, salty, and delicious. That is why people buy them all the time. Their packaged form is convenient for busy people on the go. Unlike dairy, wheat, and vegetables, snacks can stay fresh for months and years. Everyone takes these goods for granted, but they do not think about the process in making the package that keeps their goodies nice and fresh. Even the design on the package plays the role of attracting the customer with vibrant colors and enticing &#;eat me&#; signs written all over them. The chemistry of plastic packaging in snacks is more than just a clear plastic with a pretty picture on it; it consists of a series of complicated steps that requires all kinds of energy that start with crude oil and end up in supermarkets. Throughout this essay, I will attempt to explain every step of the energy processes used into making packaged snacks and their design. There are four major industries is plastics packaging: plastic resin and film producers; flexible and rigid packaging converters; packaging machinery manufactures; and food processors (Jenkins 101). The inputs to this whole process consist of raw materials, labor, money, and energy.
The first step is extracting the oil. This is a laborious process. All kinds of energy are at work. Even before the drilling begins, the land has to be set up (Jent, &#;How is Oil Extracted from the Ground?: Triple Diamond Energy&#;). Some land may have to be cleared for accessible roads. This way, vehicles can get by easily. There also has to be accessible water. This is used to mix with the earth and create mud to make the drilling process easier. Water also allows the drill to penetrate deeper into the earth. When the land is ready to be drilled, a large pit called a cellar is around the site for crew workers to work (Jent, &#;How is Oil Extracted from the Ground?: Triple Diamond Energy&#;). A drill truck comes in to drill a shallow area for a conductor pipe. This pipe supports the rig. That rig is brought in and placed over the drill site. Then it descends, working its way downward. The spinning blades and water create a lot of mud, so it is removed with a pump-based circulation system (Jent, &#;How is Oil Extracted from the Ground?: Triple Diamond Energy&#;). This whole process requires chemical (fuel for vehicles, metabolism in people), kinetic (motion of wheels, people, water, the descending drill), and electrical energy (battery operated engines, electric cars).
This is an example of an oil rig on land. <http://science.howstuffworks.com/environmental/energy/oil-drilling4.htm>
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