Product Profile of a Plastic Shopping Bag (HDPE)

Product Profile of a Plastic Shopping Bag (HDPE) Samantha Pearson Plastic shopping bags/carry bags are used extensively in todays’ world. They are produced in many different sizes and colours, determined by its purpose and marketing campaign of the purchasing firm/industry. Carry bags are made of plastic that is flexible and relatively tough1. The plastic is identified as High Density Polyethylene (HDPE), indicated by the Voluntary Plastic Container Coding System2 (used to identify different plastics for recycling) on the carry bag itself. High Density Polyethylene is listed as 2 on the coding system2. How HDPE is made Polyethylene is made of monomers of ethylene. Monomers of ethylene are obtained from petroleum through a cracking process or by modifying natural gas such as methane or ethane3. Polyethylene can be made into three different types of polymers under different conditions, namely High Density Polyethylene, Low Density Polyethylene (LDPE) and Linear Low Density Polyethylene (LLDPE). High Density Polyethylene is produced from petroleum and under low pressure conditions (pressure of about 10-80atm) 3 whereas Low Density Polyethylene is produced under high pressure conditions. At the higher end of the low pressure and higher temperatures (about 80atm and 60-200 °C) a Phillips catalyst is used to create an active site for polymerisation6. The process that uses the Phillips catalyst is known as the Phillip Process. The Phillips process was made industrial by Phillips Petroleum Company in 19614. A Phillips catalyst is a highly active catalyst made of chromium oxide on silica with a high surface area. The active site is the chromium carbon bond where the transitional metal (chromium) oxidation state is reduced by a reaction with olefin (a synthetic fibre made from polyethylene) 5 which makes the active site more reactive4. A Phillips catalyst is prepared before it enters the reactor due to the complexity of the silica support that needs to be the correct structure for optimum polymerisation5. In a Phillips process plant an ethylene feed stream is fed into a reactor with a stream of diluted pre-made catalyst. Polymerisation takes place in the reactor and exit s as a slurry. The slurry is then dried and pellets are collected at the end4. The advantage of the Phillips process is that the catalyst does not have to be deactivated or removed from the slurry as the silica base increases the activity of the catalyst and all of the catalyst reacts with the monomer ethylene4. Polyethylene with less branching is produced in this process when compared to the Zeigler Natta catalyst process4. At the lower end of the low pressure and lower temperature (about 1-10atm and 60-70 °C) a Ziegler Natta catalyst is used6. A Ziegler Natta catalyst is a combination of a transition metal compound from Groups IV to VII and a co-catalyst made of an organometallic compound from Groups I to III. In general titanium tetrachloride or titanium (III) chloride and a trialkylaluminum is used7. The catalyst, like the Phillips catalyst, also needs a support with high surface area; magnesium chloride, magnesium chloride or silica as they maximise the surface area and therefore the active sites on the catalyst7. The Zeigler Natta catalyst is prepared in the same reactor as the polymerisation occurs4. In this process; an ethylene feed stream is fed into a reactor with feed streams of metal alkyls and Group IV to VI metals (Titanium) forming the catalyst on its support in the reactor. Slurry exits the reactor where the catalyst is deactivated (to stop chains’ reacting together which keeps t he molecular weight distribution fairly constant). The slurry is then dried and power is collected at the end4. In industry today High Density Polyethylene is produced by slurry polymerisation with a silica base catalyst and the Phillips process is used more often than the Ziegler Natta catalyst process4. Polymerisation Mechanism Polymerisation occurs as a free radical chain-growth reactions. Chain growth reactions occur as successive linking of monomer molecules to the end of the growing chain8 and occur in three stages. Stage one is the initiation stage where a radical reacts with ethylene to produce a monomer radical to continue the reaction8: R†¢ + H2C=CH2 → R-H2C-H2C†¢ [1.1] The rate of initiation is defined by the rate equation: [1.2] Where f is the initiator efficiency, [I] is the molar concentration of the initiator and [M†¢] is the total concentration of all the chain radicals and kd is the rate constant9. Stage two is the propagation stage where monomer radical adds to another monomer radical. The active centre moves to the end of the chain continuously and there is only one active centre at a given time8: R-H2C-H2C†¢ + H2C=CH2 → R-H2C-H2C-H2C-H2C†¢[1.3] The rate of propagation is defined by the rate equation: [1.4] Stage three is the termination stage where chain growth is ended either by two radicals adding together or disproportionation where an atom transfers to another chain9. The rate of termination is defined by the rate equation: [1.5] The overall structure of High Density Polyethylene is: Figure 1: Structure of Polyethylene10 Figure 2: Structural Formula of Polyethylene10 Morphology of HDPE and how it suits a carry bag application High Density Polyethylene is very few short branches, if any. This results in the polymer being more crystalline than amorphous and in some areas of the polymer, it may be crystalline. The glass transition temperature (when the material becomes amorphous) of HDPE is -100 °C and the melting transition temperature (when the material turns to a liquid phase) is 130 °C11. These temperatures make HDPE an ideal polymer to make carry bags out of as the temperature that it is used in is never/rarely over and below these ranges. HDPE has significantly different properties to other polymers made in similar ways (LDPE and LLDPE). HDPE is flexible, translucent, and weatherproof; a good resistance to chemicals, relatively tough (has a tensile strength of 0.20-0.40 N/mm2)1. HDPE has a thermal coefficient of expansion of 100-20010-6 and a density of between 0.944 and 0.965g/cm3.1 The properties above are all suited for the application of High Density Polyethylene carry bags. A good tensile strength allows for relatively heavy objects to be placed into the bag without it breaking, small amounts of heat does not change its properties, it is weatherproof, allowing it to get wet with no changes to its properties, the flexibility allows for easy use, storage and functionality whereby it can be cut to create handles. A translucent appearance allows for it the plastic to be coloured as the produces seem fit which they can use for advertising purposes and make the final product aesthetically appealing if its purpose needs to be. How the finished product is made High Density Polyethylene pellets are sold by the firm that owns the plant to a manufacturer that produces plastic shopping bags/carry bags. The pellets are melted and mixed until they are completely homogenous mixture. The mixture is then heated to above 350 °C in a furnace12. The melted mixture vaporises into a tube made of the same mixture (but solid) situated above the furnace and gradually cools down the higher up the tube the vapour gets, where it condenses. Rollers flatten out the tube resulting in a film thin HDPE. While in the rolling area of the process, the film is cut to the desired/required thickness and collected on a roll. The thickness of the roll of thin plastic film is dependent on the manufacturing specifications (each roll roughly produces 35000 bags12) and is cut and a new roll starts forming automatically. The completed roll moves onto printing, where the thin film gets a specific colour/pattern dependent on the consumer. Alcohol based ink (which has to keep flowing to retain its viscosity rate – to ensure the same concentration is used and all the bags are identical) is used to print on these thin films12. Ink is transferred onto the film by ink rollers. Once printing is done, it is once again rolled up. The printed film then moves to another department where it is cut into the specified sizes and a machine with a punch, punches holes on the one side to make handles. And a sealing machine binds the edges of the bag together through heat12. Additives added to the final product In some cases to increase the tensile strength of the plastic (for heavy duty carry bags), Low Density Polyethylene may be added to the pellets of HDPE during the melting stage12. Alcohol based ink is added to give the product aesthetic appeal. Biodegradable additives such as prodegradant concentrates (PDC’s) 13 which are metal compounds which help the oxidation process of degrading plastic, added to make plastic bags more environmentally friendly. Due to the application of the product, additives such as UV stabilisers are not needed and plasticisers are not needed due to the flexibility property HDPE already has. Alternative materials to make the product Due to polymers being an environmental hazard, shopping bags/carry bags have been made with brown paper (paper bags). However this does not have the desired properties as they break easily and are not weatherproof and they do not have any chemical resistance to them. Advantages of using HDPE High Density Polyethylene (HDPE) is a polyethylene thermoplastic. Thermoplastics soften, when heated, to a liquid and flow and harden, when cooled, to a solid. They can undergo this heating and cooling cycle (curing process) which little to no change in the final product – the process is reversible as no chemical bonds are formed or broken14. This results in the plastic being easily recycled. The product can be aesthetically modified. Remoulding and reshaping can be done to them14. Weatherproof and chemically resistant High-impact resistance Light weight Disadvantages of using HDPE HDPE is not biodegradable. Due to their light weight they can blow away in the wind and travel relatively far, causing pollution and many environmental hazards to living organisms. If heated they will melt Thermoplastics tend to me more expensive than thermosets14 Recycling HDPE needs an economic incentive as it can be more expensive to recycle plastic than to make new ones2. References British Plastics Federation. (2015). Polyethylene (High Density) HDPE. Available: http://www.bpf.co.uk/plastipedia/polymers/HDPE.aspx. Last accessed 2015/05/20. P Gaylard. (2009). Lecture 1. Polymer Science. University of Witwatersrand. p. 5, 27. P Lepoutre. The Manufacture of Polyethylene. Available: http://nzic.org.nz/ChemProcesses/polymers/10J.pdf. Last accessed 2015/05/20. Buffalo School. High Density Polyethylene. Available: http://wwwcourses.sens.buffalo.edu/ce435/Polyethylene/CE435Kevin.htm. Last accessed 2015/05/20. KBR. (2015). Olefins. Available: http://www.kbr.com/Technologies/Olefins/. Last accessed 2015/05/20. P Gaylard. (2009). Lecture 10. Polymer Science. University of Witwatersrand. p. 3. P Gaylard. (2009). Lecture 8. Polymer Science. University of Witwatersrand. p. 9-12. P Gaylard. (2009). Lecture 2. Polymer Science. University of Witwatersrand. p. 3. P Gaylard. (2009). Lecture 6. Polymer Science. University of Witwatersrand. p. 23-33. Macrog. Polyethylene. Available: http://pslc.ws/macrog/pe.htm Last accessed 2015/05/20. Michigan State University. (2013). Polymers. Available: http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/polymers.htm. Last accessed 2015/05/20. Discovery Channel (2010). How it’s made Plastic Bag Episode. Available: https://www.youtube.com/watch?v=8CfL5xl2N1Q Last Accessed: 2015/05/20 Maria Trimarchi Vicki M. Giuggio. (2009). Top 10 Eco-friendly Substitutes for Plastic. Available: http://science.howstuffworks.com/environmental/green-tech/sustainable/5-plastic-substitutes.htm#page=3. Last accessed 2015/05/20 Mordor Plastics. (2015). Thermosets vs Thermoplastics. Available: http://www.modorplastics.com/thermoset-vs-thermoplastics. Last accessed 2015/05/20. 2015

Reflection on Placebo Effect Essay

Does a Supportive Patient-Therapist Relationship Enhance Clinical Improvement? Kaptchuk (2008), Components of Placebo Effect: Randomised Controlled Trial in Patients with Irritable Bowel Syndrome. (PRO) Argument 1: Kaptchuk (2008) suggested that placebo effects (non-specific effects) include three components: a patient’s response to observation and assessment, the patient’s response to the administration of placebo treatment, and the patient’s response to the patient-practitioner interaction. Kaptchuk (2008) found that the symptoms of IBS patients in the condition with placebo treatment and supportive patient-therapist relationship ameliorated the most across all measures compared to patients with having only observation and the patients with only placebo treatment. Thus he claimed that a supportive patient-therapist relationship is the most potent component of placebo effects. Argument 2: After three and six weeks, only in the condition with placebo treatment and supportive patient-therapist relationship, the symptom severity score of 60% patients decreased 50. Also Kaptchuk (2008) found that after six weeks, the change in life quality of patient in condition with only observation and the life quality of patient in condition with placebo treatment was similar, but the life quality change of patient with placebo treatment and supportive patient-therapist relationship was observable. So Kaptchuk (2008) suggested that a supportive patient-therapist relationship can enhance clinical improvement. Argument 3: Kaptchuk (2008) also compared these IBS patients to the patients who received IBS drug treatment. He found that the patients with placebo treatment and supportive relationship had comparable symptom relief as those who with drug treatment. His finding was only applied to IBS patients with supportive patient-therapist relationship, thus he indicated that a supportive patient-therapist relationship could enhance the efficiency of clinical treatment. Critique (or Strength): The result of the study done by Kaptchuk (2008) clearly demonstrated the importance of supportive patient-therapist relationship in medical treatment. However, Kaptchuk conducted the study on IBS patients, because he believed that placebo effects are most likely to be demonstrable in disorders defined by subjective symptoms. As Kaptchuk (2008) stated in limitation that he did not know if his finding could be applied to other illnesses, I also think that if Kaptchuk conducted his study on patients with the disease that has external causes, the results will be more convincing. One of important causes of IBS is stress, a subjective etiology. Thus a supportive patient-therapist relationship may have greater influence on IBS patient than the patient with other diseases, like flu.

Ntuc Fairprice Essay

NTUC FairPrice is a social enterprise of Singapore National Trades Union Congress (SNTUC), the only trade union centre in Singapore. Founded in 1973, the vision of the organization was to moderate the cost of living. NTUC FairPrice is now the largest supermarket chain in Singapore, they consist of 1.FairPrice Supermarkets 2.FairPrice Finest 3.Cheers 4.FairPrice Xtra, 5.FairPrice Xpress 6.FairPrice Online 7.providing their service to 300,000 odd customers daily (Superbands). IKEA IKEA was founded in Sweden in 1943. Their uniqueness lies in their design furniture for flat packs for self assembly, by the customers (IKEA, 2011). IKEA’s business practice is known for cost control and continuous product development.IKEA is operating in 38 countries. Although IKEA’s primary intention is to have its end users to transport the furniture by themselves, in Singapore, where many of its consumers may not have their own transport, they also offer delivery service. Procurement, Purchasing And Sourcing FairPrice Firstly, we take a look at Fairprice’s logistic processes, Procurement, purchasing and sourcing. Searching suppliers and conclude agreement Suppliers require meeting Fairprice’s product quality requirements especially for their cold chain management. It helped Fairprice and suppliers gain competitive advantage by contribute quality products for a long period to the demand customers as it gave positive effect on its revenue.For each product group, only limited number of suppliers can supply. Receiving stock requirement from NTUC’s stores They are IT enabled where stock requirement are sent to DC based on their inventory management in which stocks reaches its reorder point needs to start ordering new stocks. Purchasing orders with suppliers Tracking their orders, invoices and payments via SAP Ensuring delivery sent at DC/Stores Perishable products are sent directly to stores. Non-perishable products like butter, cheese are sent to DC. Processing consumer returns and non conformance To process non conformance in which suppliers fails to meet Fairprice’s product quality requirements in their product and dealing with returns in stores using Goods Returned Note. Fairprice’s procurement assures to have a long last and continuous relationship with their suppliers. IKEA All products from IKEA are manufactured according the designed code of conduct â€Å"The IKEA way on Purchasing Home Furnishing Products†(IWAY), as it require main IKEA’s relationship with their suppliers. All suppliers must achieve the requirements.IKEA sources internationally with 5 countries which is China, Italy, Poland, Sweden, Germany. Their 2 main focus is to increase sustainability of their suppliers and increase uses of sustainable raw materials. IKEA aims building long term relationship with suppliers that share same values. They focus to encourage suppliers having developments become sustainable and independent of IKEA presence by committing to IWAY.IKEA’s auditor’s visits suppliers regularly to assure that IWAY’s requirements are met.The compliance and monitoring group (CMG) ensures that same audit requirements are used worldwide. There are 4 major categories of suppliers which is Home Furnishing with 13,800 suppliers, Food with 76 suppl iers, catalogue with 50 suppliers and Transport service with 263 providers. IKEA purchased products both regionally and globally so as to have low price with high quality.They have a purchasing unit called IKEA component in which develops raw materials and components for their product and acts as sub-supplier to IKEA suppliers manufacturing finished products. Inventory Management Fairprice The second logistic process that we are going to look into is the Inventory management. Fairprice and Ikea have designed their inventory management in a way that it will reduce costs and positively impact the company’s return on investment. Fairprice has 2 warehouses and they only hold finished goods in their warehouse. This enables the company to largely reduce the time Fairprice will need to hold the inventory. Inventory cost such as carrying cost and risk cost will be reduce. Fairprice’s inventory management adopts the push approach. The stocks from each outlets will reach a certain stock level where the store staff will make the orders to the GLS (Grocery Logistics of Singapore). GLS will have enough time to consolidate all order from different outlets and enables them to make lesser trips for delivery, thus save the delivery cost and also prevent a stock out situation. IKEA IKEA adopts a special inventory whereby they manufacture their products by a push approach. The operational forecast and the tactical forecast are combined to create a final forecasts on store levels which will be aggregated, reconciled and compared with the same frames based on the retail and distribution services forecast group level. IKEA’s store operations focuses on the Pareto’s law by supporting high-flow facilities and low-flow warehouse that are more manual. In its high-flow warehouses, IKEA employs automatic storage and retrieval systems (AS/RS) to drive down its costs-per-touch. IKEA have large bins, which is sufficient enough to cover sales for one day as what is sold is captured by Point of Sales (POS) system and what comes into the store is also known via Warehouse Management System (WMS). Thus, very little cycle counting is done. However, IKEA is able to detect any abnormalities. For example, when the system expects a certain volume of a particular product to have been sold during a two day period and less products was actually sold, the system will trigger and will direct in-store logistics to head to the location to do manual checks. With this process and system, it enables the right goods to be in the store with higher certainty as compared to the traditional retail forecasting/replenishment process. Warehousing and Distribution Fairprice The third process is warehouses and distribution. FairPrice faced problems till 1993 as suppliers used to deliver their products to Fairprice stores directly. This recorded up to 200 deliveries everyday with more than 30,000 products to managed and their distribution system were unproductive and was prone to errors. After 1993, Fairprice’s manage the Grocery Logistic of Singapore(GLS) Distribution Centre which is central distribution centre(DC) .GLS manages 2 distribution centres at Penjuru and JooKoon. In 2002, Fresh Food Distribution Centre(FFDC) is Fairprice’s centralized refrigerated DC to implement only fresh food items which they need right temperature to kept fresh. This allowed Fairprice improvise their supply chain management of these perishable products through a better temperature management control. It’s essential knowing the temperature for perishable products. Products like milk, chilled pork and dairy products are delivered directly to the stores b y suppliers to avoid spoilage. There are 6 warehouse handled under FFDC with different controlled temperatures ranges between -20 to 18 degree Celsius. The temperature in each of the warehouse is controlled and observed assuring that products are kept safe at the right temperatures. This enables NTUC Fairprice increases its efficiency and manage its supply chain as moving stocks faster helps maintain the freshness and improve quality of products. They provide proper infrastructure to maximize storage management and able to improvise the process of handling the fresh food, especially with the right temperature therefore reducing spoilage. By having Hazard Analysis Critical Control Points (HACCP) certified, they devote maintaining good standard food safety and hygiene in DC. They operate 7 days a week and deliver more than 28 million cartons to the stores per year.

The Hero Of Ancient Literature - 1284 Words

Hero’s of Ancient Literature When surveying the nature and work of Gilgamesh, Rama and Odysseus, all of them have the main characteristics that qualify them as heroes. These heroes’ were determined to do what was right for their town and their families and were set on following their dreams that they had set for themselves. These heroes were looked up to and respected by the people that surrounded them. They were needed because they gave people something to seek for and provide as a positive figure. A true hero is someone who shows and presents faithful qualities and is a respectful person. Gilgamesh was the king and the leader of Uruk. He was also the role model of all the other men and even the women; they wanted to be like him. In the story of Gilgamesh it reveals two important things. The first thing is the ambition and passion to observe the Gilgamesh’s importance and greatness. 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