THE 36TH ANNIVERSARY
Experience a moment with UPLB SChemES! This virtual exhibit will let you explore not just our organization, but also one of the important Chemical Engineering topics.
Increasing demand for natural resources affects the sustainability of Earth. Packaging is important in our daily life, wherein plastics are commonly used. This is very alarming, especially in the Philippines wherein we have unsustainable plastic production and consumption caused by insufficient solid waste management. Thus, awareness of sustainable PET packaging leads you ahead. PET is an energy-efficient material for packaging. It has a great sustainability profile due to its strength, adaptability, and recyclability.
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Polyethylene Terephthalate, commonly known as PET or PETE, is a thermoplastic polymer that is widely used as packaging for a variety of products. This includes, but is not limited to, packaging for foods, beverages, cleaning and hygiene products, and cooking ingredients. PET has been approved by health-safety agencies throughout the world and its safety is demonstrated time and again through extensive studies and regulatory testing and approvals.
WHERE DOES PET COME FROM?
Polyethylene terephthalate is made from combined ethylene glycol and terephthalic acid under the influence of high temperature and low vacuum pressure. To produce PET, antimony oxide is used as a catalyst.
PET vs. Other Packages
PET vs. PVC
PET plastic has the ability to take colorants very well and demonstrates excellent adherence qualities for external printing. It is FDA- approved food graved plastic which makes it safe for storing food. This plastic is versatile when it comes to use. It can be thermoformed into a variety of shapes may it be a package for food, electronics, retail and other products. It is lightweight, transparent and shatterproof.
It has lower heat resistance compared to PVC. The production of PET plastic, partially derived from crude oil which is harmful for the environment. Although PET is more expensive than PVC, it is more environmentally friendly since it does not lose its fundamental properties during the recovery.
PVC or polyvinyl chloride is a rigid plastic designed to withstand impacts. It has excellent tensile strength and good resistance to chemicals and alkalies. It ranks well for hardness and durability. This material can be seen in creating cables, roofing materials, commercial signage, flooring, faux leather clothing, pipes, and more.
It emits hydrogen chloride when burned which might be a health hazard. Due to its smell and lower resistance to temperature, it is not safe for storing food. Most state authorities do not accept PVC in consumer recycling programs. Clear PVC has often a light tint while PET is virtually clear.
PET vs. PP
PET most commonly available plastic in the world. plastic cups are slightly better than PP containers. It shows higher durability and is shatterproof. It also has better oxygen barrier properties, the ability to retain the taste and aroma of food, and resistant to acids, grease, and oils.
In terms of heat resistance, it can only withstand 160 degrees Fahrenheit while PP can withstand up to 176 degrees Fahrenheit. Even if PP resists heat better than PET, PET plastic resists cold much better than PP. PET plastic is not easy to print on so it uses paper, cardboard, or thin plastic in order to give a brand.
PP – Polypropylene Plastic, the second most widely used plastic in the world, was produced via condensation polymerization of ethylene glycol and dimethyl terephthalate. It is also used for soft drink bottles, the production of fibers for clothing in textile industry, production of containers for food and beverage storage. It is also lightweight, low toxicity, high melting point and is highly transparent. PP plastic can
PP plastic may be printed in a variety of colors. In terms of branding PP is a better choice but once printed it cannot be repurposed since it is already permanent.
It has low resistance to aromatics and chlorinated solvents. It also shows vulnerability to UV degradation. PP in comparison is more opaque because of its poor bonding properties, it is well known to be challenging to paint. Still, it is used as it gives distinctive look to the cup.
PET vs. LDPE vs. HDPE
PET bottles are 20-30% cheaper and lighter in weight than HDPE. 1.8 billion pounds of PET bottles and containers are recovered every year and have a recycling rate of 55%.
Due to its transparent appearance, it can show off the product and ensure the customers that their product were safe. Products that require sturdier plastic such as dried products are more applicable to use PET as packaging.
LDPE – Low-Density Polyethylene is a type of thermoplastic that is created from the monomer ethylene. Unlike PET, it has opaque, natural-colored plastic. This kind of plastic is squeezable so it can be used as garbage bags, cling wrap, squeeze bottles, mulch film, irrigation, tubing, and refuse bags. LDPE is also FDA-approved and BPA free which makes it safe for storing food like PET. LDPE packaging usually cost more but the material is at high-quality.
HDPE – High Density Polyethylene is also one of the most versatile plastic in the world. Its advantages are good oxygen barrier, squeezable, great impact strength, and easily recycled. Just like PET and LDPE, it is also BPA free and FDA approved, so it is safe for food packaging.
It is more expensive due to high raw materials. Although it is recyclable, the rate of bottles recovered is only 31%. The rate of landfill of HDPE is high compared to other plastic packaging materials. They are also 100% recyclable but it requires intensive processing techniques to achieve desired purity with increased operational costs than PET.
PET vs. ALUMINUM vs. GLASS
PET plastic has a lower carbon footprint because it is lightweight in transportation which is less emissions. Unlike glass and aluminum, it requires lesser energy due to lower temperature in the process of melting the raw materials. It offers all the benefits of glass durability, reusability and transparency and still lighter, cheaper and more versatile.
Aluminum cans are also completely recyclable. Glass and aluminum do not break into harmful microplastics, unlike plastics. Cans are lighter than glass and aren’t made from fossil fuels.
Only 45% of aluminum cans are being recycled in the world. However, using recycled materials in producing aluminum cans can reduce its carbon footprint.
It also impacts environmentally since the raw materials came from mining. Also, the refining of bauxite ore contaminates water.
PET vs. Other Packages
Glass is 100%recyclable and it can be recycled without reducing the quality. But the recyclable process of glass uses a lot of energy because of the high temperatures needed to melt it.
Glass also uses raw materials from mining which leads to pollution. Materials such as silica sand and dolomite when inhaled can lead to lunch condition silicosis.
Transporting glass bottles causes a higher carbon footprint since it requires more fuel as it weighs heavier.
PET vs. CARDBOARD
PET plastic is energy-efficient packaging material since raw materials are derived from natural gas or crude oil. Due to its low weight-to-strength ratio, this plastic has an advantage when it comes to transport. It is infinitely reusable as it does not decompose over time.
Cardboard or brick cartons packaging is a multi-layered multi-material packaging, well known as tetra packs. It is composed of the outer layer which is made from wood and the innermost layer which is made from aluminum. The innermost layer is in direct contact with a food item, in plastic. The pieces of cardboard will take them six to eight months to break down completely.
Due to its opaque appearance, consumers can’t determine the quality of the product inside which might pose as hazardous. They are also bulkier and heavier which means a higher carbon footprint. Paper can only be reused 4-5 times and it reduces its quality every time.
Crude oil and natural gas are the sources of raw ingredients used to make PET. A typical misconception is that crude oil is mostly consumed by plastics and chemicals. However, when combined, they only represent less than 10% of yearly global usage. (PETRA, n.d.)
PET material has a relatively high density and manufactured by Ensinger in standard stock shapes for machining. They are available either as an amorphous or semi crystalline thermoplastic (Ensinger, n.d).
This process allows hollow plastic parts to be formed. The air pressure inflates the soft plastic into a mold cavity. It has two part plastic manufacturing process. (Thell, 2016)
Crete starting tubes of molten plastic, called Parisons. They serve as base for the extrusion blow molding process. After the fabricated of parisons and ready to be molded, the second part begins.
Air inflating of the tube or preform to the desired shape. It can be done by either 3 processes:
Extrusion blow molding
Injection blow molding
Injection stretch blow molding
It is mainly used to enhance the modling of PET. Screw type injection machines was used and usually needs to be hardened to avoid wear after long term use. (Ningbo Leadway Machinary Tech Co., 2021)
Barrel temperature (unreinforces grades: 240-280℃)
Barrel temperature of glass fiber reinforces PET: 250-290℃
Temperature of nozzles: Should not exceed 300 C
Melt temperature: 280-310 ℃
Mold temperature: 140-160℃ to obtain a crystalline PET (for technical applications)
Screw with an L/D ratio of 18-22 is recommended
For transparent applications, mold temperatures should lie betweel 10 and 50℃
Extrusion 3D Printing
PET is extruded to produce films and sheets (which can be thermoformed after) for food packaging applications. (Omnexus, n.d.)In the extrusion process, a hopper machine collects plastic beads or pellets melded together into one product.(Helmke, 2015)
PET is a thermoplastic resin therefore it can be melted and shaped repeatedly. With the plastic extrusion process, PET bottle flakes, and then an air compressor will turn the molten plastic into a synthetic fiber. (Milad & Simon, 2019)
PET is known to produce 3D Printed objects having high flexibility and toughness. PETG is PET copolyster with glycol modification. It is more heat-resistant and tough than PLA, but easier to print than ABS. The material also benefits from great thermal characteristics, allowing the plastic to cool efficiently with almost negligible warpage.(Omnexus, n.d.
How PET is recycled?
All scraps that constitute waste are collected. It is taken to a recycling plant for further inspecting and screening. According to the Department of Environment and Natural Resources (2021), the annual waste produced by a population of 100 million Filipinos is 21 million metric tons.
Once PET is collected, it will be compressed to ensure ease of transport. Due to its lightweight property, the efficiency of transport is assured. Furthermore, this course of action reduces greenhouse gas emissions from transportation (Petcore, n.d.)
As the PET is in the form of small crushed flakes, it is thoroughly washed to remove the ground-up lids, rings, labels, and residual glue. Moreover, it is processed by a high-temperature decontamination section to remove the post-consumer substances and flavors.
As the accumulated waste is transported to the recycling plant, the separation of recyclable materials such as plastics, glass, and metals is conducted. They move at their respective recycling streams. A high-value recyclable polymer such as PET is segregated manually or by using an automatic system. Being meticulous is essential in determining the presence of other plastics because contamination of the PET recycling process is possible, which will limit the quality for reduction, efficiency is detrimentally affected, and it would be not valuable enough (Petcore, n.d.).
Bales of compressed PET are directed to the processing center in which the waste PET is converted into recycled PET (rPET). It is further separated with respect to their color streams and a plastic bottle shredder is used to create small crushed flakes.
After decontamination, it is melted into spherical like crystalline PET pellets which will be suitable for creating new materials such as PET bottles, fibers, etc.
PET pellets are shipped to the manufacturers that will use the rPET. Recycled PET meets the standards set by agencies and governments around the world that it is safe to use in food packaging
An endless bottle-to-bottle loop is deemed idealistic but possible; however, there are instances when the plastic collected and transported for recycling is substandard. Thereby, it is heated and converted into fiber which can be serviceable in creating seat belts, bags, carpets, roofing insulation, and clothing.
Waste PET is converted into renewable unsaturated polyesters by forming partial glycolysis. Which is turned into bio-based unsaturated esters. Once it is prepared, it is mixed with glass fibers and cured the material by free radical polymerization. Finally, the output is a high-performance product (Allen,2019).
Retrieved from: https://www.azom.com/article.aspx?ArticleID=15875
The following are the objectives of using wasting plastics into asphalt mixes: a) it will minimize landfilling b) being independent on nonrenewable resources, c) it will open to more options of asphalt pavement building. Furthermore, appropriate engineering performance (viscosity, rutting, fatigue cracking, thermal cracking, and moisture resistance) is a needed parameter to secure its quality. PET is granulated by 1.18-2.36 mm which is mixed in the asphalt mixture (Wu & Montalvo, 2021)
With an equal ratio of plastic waste and quarry dust, it offers a high compressive strength with melting point of 1400C. Furthermore, plastic paver block reduces plastic pollution and overall cost of production. All things considered, it is deem economical and eco-friendly to have this approach than the conventional paver blocks (Lognayan,2020).
Granulated PET is used as the construction material because it can withstand high amounts of load and pressure and is lightweight. Its low cost and durability make it suitable to use as a brick (Pokale, Gund, Gholve, & Chauhan, 2022).
Solar water disinfection
using PET bottles
Exposing the PET bottle filled with untreated water in sunlight for at least six hours destroys pathogenic germs, which makes the disinfection process effective. Given that it is effective, simple, and cost-efficient, it is suitable especially for developing countries (Kumar et.al., 2021).
Retrieved from: https://shoplt.arfotografi.com/content?c=sodis&id=1
Chemical engineering, by definition, is a multidisciplinary approach to real problems. Chemical engineers are indeed a powerful tool in solving environmental problems such as in plastic packaging, with their wide background on chemical reactor design, kinetics, simulation, control, modeling and especially, heat and mass balances. They are needed to research and apply these emerging technologies into the widely used processes in different industries.
Role of Chemical Engineers to Solving Problem on Packaging, Waste, and Pollution
Different methods of PET recycling are already being used such as hydrolysis, pyrolysis, and chemolysis. As chemical engineers, they are responsible for creating a scalable process of PET recycling that may be utilized in different industries. An example of this would be a study using Ionic Orrganocatalysts as a scalable process of PET depolymerization. Mainly, it focuses on enabling catalyst immobilisation and increased product recovery. In short, the role of chemical engineers applies these PET Recycling processes in an industrial scale.
Another part of the chemical engineer’s contribution to solving plastic waste problems is ensuring that their company could apply the Extended Producer Responsibility, wherein they remain owners of the bought plastic and must accept it back after use. The recovered materials could be used for recycling and reuse back to the production process. One good example of this is the Container Deposit System in the Netherlands that collects bottles and reuses them. However, many companies hold back to this thought because they know how costly this effort could be.
As beneficiaries of the innovative plastic packaging, we also have responsibilities to uphold when using them. As consumers, our main role is basically limiting consumption and demand. The more we use these products, the more the demand for their production increases, causing a never ending cycle of waste production and pollution.
Roles of Consumers and Government to Solving Problem on Packaging, Waste, and Pollution
Our first step must be awareness. Being aware of the pros and cons of plastic usage is proven to be beneficial for facing these environmental concern. By being aware of its disadvantages, we may be able to avoid being blinded by the convenience of its use and may be able to promote plastic waste reduction. Our next step would be action. Simply being aware of the problem is not enough to solve it. We must take part and participate in the recycling, recovery, and reuse of these materials. With that in mind, opportunities must be provided by the government and different organizations for consumers to be motivated to take part in this initiative. Addressing this huge environmental concern requires the participation of not the consumers but most expecially those in power.
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