Polycarbonate0
An In depth report
Polycarbonate0 Will Bamber An In depth report
Introduction This report contains relevant designer information regarding to the thermoplastic polymer, polycarbonate (PC). The report will discuss the materials classification, methods of production, history, environmental impact, commercial uses, manufacturing uses, cost and fundamental properties. To reinforce the material qualities and uses, an in depth analysis of the common commercial product, the CD-ROM, has been undertaken to provide further understanding. This includes a manufacturing overview which essentially creates an full life cycle analysis in relevance to the material of discussion (Polycarbonate).
Polycarbonate Polycarbonates are linear, amorphous polyesters (Richardson, 2004). The plastic is classified in such a way due to its chemical makeup of a combination of esters and aromatic bisphenol. Polycarbonate is classified as a thermo plastic (Arnold, 1968) and is also known as an “engineering plastic”.
History
Fig 1. A polycarbonate CD
Polycarbonate discovery can be traced back as far back as 1898 when A. Einhorn produced a polycarbonate material through a reaction of resorcinol and phosgene (Richardson, 2004). Following World War II, two separate entities researched into the production of polycarbonate. Farbenfabriken Bayer in Germany and General Electric in the United States, both arrived at the same conclusion of producing production based polycarbonate through a reaction of bisphenol A. However, volume based production of polycarbonate did not begin until 1959 in the United States. Polycarbonate was originally used for electrical applications (Portal, 2013) due its ability to remain constant over a wide range of temperatures and humidity (Donald, Rosato, & Rosato, 2004). Applications included distributors and fuse boxes, displays and plug connections and subsequently for glazing for greenhouses and public buildings. Once its properties were truly recognized, polycarbonate begun to be introduced to many different applications. In 1982, audio records begun to be phased out due to the market introduction of the audio-CD. Optical storage systems took over the industry, which all depend on polycarbonate. Optical media technology developed rapidly, within 10 years this included CD-ROMs which was followed soon after by DVDs (Portal, 2013). Polycarbonate has been in used in vehicle headlights since the 1980’s and almost every car today, regardless of origin, contains polycarbonate headlights. In all, polycarbonate has enjoyed a steady and “successful” evolution over its 50 year market existence (PERP Program - Polycarbonate, 2013) to the point where 2.7 million tons of polycarbonate plastic is produced annually which equates to approximately 50% of all engineering plastics worldwide (Donald et al., 2004).
Polycarbonate0 An In depth report
Methods of production Interfacial Process The first process widely commercialized for the production of polycarbonate, involves reacting phosgene with bisphenol A (BPA). The interfacial process is the preferred process for the production of polycarbonate since it can be carried out at low temperatures using simple technology and equipment (Richardson, 2004). Both the Melt and Interfacial process is considered to be comparatively high in cost. The process is named so due to the reaction that occurs at the interface of the organic and aqueous phases (PERP Program - Polycarbonate, 2013). An important material in this process, Phosgene, is highly poisonous and was once used in World War I as a poisonous gas. It therefore, needs to be handled with extreme skill and care. The interfacial process of production is generally carried out in either a singular or multiple stage process and additionally can be completed in batch modes or continuously. These options have a larger economic effect on the process rather than chemical differences, however, the continuous method can contain more nitrogen than the batch process (PERP Program - Polycarbonate, 2013). Although every manufacture has their specific processes, the interfacial process essentially consists of five stages: • • • • •
Phosgene production or sourcing Polymerization (reaction between phosgene and bisphenol A) Polymer washing and separation Polymer recovery and drying Finishing and storage
Melt Process The original industrial process proposed for the production of polycarbonate was via melt transesterification between diphenyl carbonate (DPC) and bisphenol A (BPA) (PERP Program - Polycarbonate, 2013). Although the interfacial process has been the preferred method of production for many decades, melt technology has regained renewed interest since the mid 1990’s due to the corrosive by-products that the interfacial process produces. Unlike the interfacial process, melt technology uses no phosgene or chlorinated solvents to produce polycarbonate which effectively negates the growing environmental concerns and by-products the interfacial process causes, allowing for “newer, more efficient, catalysts and process designs” (PERP Program - Polycarbonate, 2013). Although the method of production may sound completely different, the resulting chemistry of polycarbonate is the same as with the interfacial process. Major differences reside only in engineering design differences and individual plant specifications. The melt transfer process (Melt transesterification) takes place in a two stage process. Firstly, diphenyl carbonate and bisphenol A are combined with a catalysts such as sodium in a melt reactor which causes a per-polymer and liberating phenol. The phenol is then removed from the equation through a distillation process. The chemical reaction stages can be viscous to the point where specialist equipment must be used. Once isolated from the phenol, the polycarbonate melt is spun in the form of strands and granulated (PERP Program - Polycarbonate, 2013). It is vital to both the interfacial and melt processes to have a high purity of bisphenol A in order for the plastic to possess a high clarity and long linear chains with no cross-linking substances (Richardson, 2004).
Polycarbonate0 An In depth report
melt process continued. Finally, original results of the melt process produced “sub-par” polycarbonate, as it was discoloured due to the extensive heat exposure and potentially impure reactants early in the process. This specific issue to the melt process has been nullified in recent years due to developments in catalysts systems, reactive carbonates and more effective processes. The process has evolved to the stage where its product equates to that of interfacial polycarbonate (PERP Program - Polycarbonate, 2013).
Isosorbide-Based Polycarbonate There has been a huge surge of interest into bio-chemical and green process for well-known products such as polycarbonate. This process essentially reduces the need for petroleum based reactants, replaced by natural resources. It also removes the need for the use of the toxic phosgene and controversial bisphenol A, which is widely used in current day polycarbonate production (PERP Program - Polycarbonate, 2013). One of the two main reactants user in biomass-based polycarbonate can be produced from renewable resources, namely sugar rather than petroleum-based feed-stocks. Although the demand for an isosorbride based polycarbonate is new, the idea behind it is not. The first attempt to prepare isosorbide polycarbonate by melt transesterification reaction with diphenyl carbonate (DPC) was carried out in 1967, which resulted in a brown white powder (PERP Program - Polycarbonate, 2013).
CD-ROm Manufacture (The Compact Disc Manufacturing Process, 2002-2012) 1. Premastering The manufacturer first insures the CD-ROM content is of an ISO standard, provided by the customer. This step is rather important as it ensures a quality guarantee for professionals who require a high level of quality data reproduction. 2. Mastering Customer information is then engraved with a laser light onto a glass master covered with a photosensitive layer. As a prevention device for piracy, plants engrave an International Federation of The Phonographic Industry (IFPI) number on ever glass disc. A fine silver coating is then applied to the surface known as vacuum evaporation. 3. Electroplating The glass master is then goes through an electrolysis process which adds a layer of nickel to the glass which is then separated to recover a negative of the CD. This is known as a stamper and essentially forms the “mold” for injection molding.
Fig 2. Mastering
Fig 3. Electroplating
4. Pressing Liquefied polycarbonate is then injected into the mould. In a process that takes less than 5 seconds, a CD is produced containing all the customers’ information. Anywhere from 550-900 discs can be produced per hour depending on the machine. Fig 4. Pressing
Polycarbonate0 An In depth report
CD-ROm Manufacture Con. 5. Metallization A further vacuum laid process is used to then make the CD readable. This disc is covered with a micro thin layer of aluminium. The aluminium surface acts as a mirror, reflecting the laser light back so the information can be withdrawn. 6. Varnishing In order to protect the CD and its carrying information from potential harm be that from dropping, bending or scratching, the disc is treated with a layer of varnish. The applied lacquer envelops the aluminium and seals it from the potentially harmful elements. Following this process, the disc is then ready for printing/branding. 7. Label Printing In either a silk screen of offset process with up to six colours, the final touches of branding/labelling is applied. This results in a professional and refined appearance which Finally looks like a product.
Fig 5. Metallization
Fig 6. Varnishing
8. Packaging/Shipping After a final quality control process for the stamper and randomly selected discs (for long production runs), the discs are packaged and sent on their way to their respective locations.
Environmental Impact of Polycarbonate Many manufacturers have stopped using polycarbonate for application relating to drinking apparatus or human intake due to the presence of bisphenol A which has been reported to radiated out of the material if subjected to high temperatures such as warming baby bottles. In terms of polycarbonate being disposed at a landfill, this is a nightmare for the environment as the material never biodegrades due to it being made of petroleum. Chemicals involved in the production of polycarbonate can leach into the environment causing obvious damage, many of which are consumed by surrounding wildlife (Azom, 2013). In relevance to this report, larger amounts of CDs are discarded worldwide that results in serious pollution issues. There are methods in the workshop into how to address these issues however currently they have been found to be ineffective.
Recycling of Polycarbonate and CD-ROMs Polycarbonate is rated as a difficult to recycle; however, extensive research is and has been done in regard to polycarbonate bottle and CD recycling in particular. One method involves chemically recycling to reform a polymer (Azom, 2013).
Polycarbonate0 An In depth report
Environmental Impact of Polycarbonate COn. A CD is made up from approximately 95% polycarbonate with dye and reflective layers making up the rest of the product. A novel way of dealing with the issue of CD recycling is to burnish the surface which removes the dye and reflective surface which are collected for further treatment. The burnished disc is then washed with ethanol that dissolves the dyes used in the production of the CD. Following an electrolysis process, the disc is essentially pure and left as is with all metals recovered (Azom, 2013).
Material Properties (Arnold, 1968), (Richardson, 2004) and (Donald et al., 2004) Advantages • • • • • • • • • •
High Impact Strength Excellent creep resistance Heat Resistance Available in transparent grades Continuous application temperature over 120C (248F) Very good dimensional stability Good Chemical Resistance Electrical Properties Weathering Resistant “Self-extinguishing”
Disadvantages • • • •
High processing temperatures Poor resistance to alkalis Subject to solvent crazing Require ultraviolet stabilization
Forming Qualities Suitable for: • Injection Molding • Extrusion • Vacuum Molding • Plastic Welding • Machining Industrial/Commercial Uses • • • • • • • • • •
CD’s DVD’s Blue ray Discs Equipment Housings Exterior Automotive Components Outdoor Lighting Fixtures Nameplates and Bezels Non-Automotive Vehicle Windows Vehicle Headlights Brackets and Structural Parts
Polycarbonate0 An In depth report
Material Properties Con. Industrial/Commercial Uses • • • • • • • • • • • • • • • • • • •
Medical Supply Components Plastic Lenses for Eyeglasses Electrical and Telecommunications Hardware Bullet Resistant “Glass” “Theft-proof” Packaging Bank Teller Screens F-22 Raptor Cockpit Canopy Bottles and Containers Small Motorized Vehicle Windscreens Drinking Glasses Lightweight Luggage, Mp3/Digital Audio Player Cases Ocarinas Computer Cases Riot Shields Instrument Panels Blender Jars Safety Helmets Drafting Film
Cost Regardless of the method of production, polycarbonate is considered to be comparatively high in cost.
Conclusion In conclusion, the thermoplastic polymer, polycarbonate, is a multipurpose plastic that has had a long production based life. Used in many commercialized products, polycarbonate is particularly used for uses that utilize high impact resistance, high impact resistance, creep resistance, transparency, temperature resistance and dimensional stability. Whilst possessing these particular properties, polycarbonate is an excellent injection mold plastic as demonstrated by the CD-ROM analysis. In terms of its environmental effect, current manufacturing processes involving the chemical, phosgene, is concerning and potentially harmful to users of polycarbonate products, the environment and the future of the material as commercial option.
Polycarbonate0 An In depth report
References Arnold, L. K. (1968). Introduction to plastics: Iowa State University Press USA. Azom. (2013). Polycarbonate, Plastic Recycling. Retrieved from http://www.azom.com/article.aspx?ArticleID=7963 The Compact Disc Manufacturing Process. (2002-2012). Retrieved 10th August 2013, from http://www. duplication.ca/cd-process.htm Donald, D., Rosato, M., & Rosato, R. (2004). Plastic product material and process selection handbook: Access Online via Elsevier. PERP Program - Polycarbonate. (2013, 2013). Retrieved from http://www.chemsystems.com/about/cs/ news/items/PERP09107 _P_olycarbonate.cfm Portal, T. P. (2013). The history of Polycarbonate. Retrieved from http://www.plasticseurope.org/what-isplastic/old-types-of-plastics/polycarbonate/the-history-of-polycarbonate.aspx Richardson, T. L. (2004). Industrial plastics: Theory and applications: Delmar Pub.
Bibliography Arabe, K. C. (2003, September 11th, 2003). Polycarbonate: 50 & Still Going Strong. Retrieved from http://news.thomasnet.com/IMT/2003/09/11/polycarbonate5 _/ epc.com. Polycarbonate production plants. Retrieved from http://www.epc.com/fileadmin/inhalt/downloads/pdf2_ 013/01P_olycarbonatee_ ng.pdf GEA. (2013). Production of Polycarbonate. ICIS.com. (2010, 21 September 2010). Polycarbonate Production and Manufacturing Process. Retrieved from http://www.icis.com/Articles/2007/11/06/9076147/polycarbonate-production-and-manufacturing-process.html news.discovery. (2013, FEB 11, 2013 03:00 AM). Fungi Digest Plastic Trash. Retrieved from http://news. discovery.com/earth/fungi-plastic-chemicals-bpa.htm Pressroom. (Monday, February 13, 2012 8:00 am). After Major Downturn, Global Demand for Polycarbonate Growing Again, Says IHS Chemical Report. Retrieved Services, P. T. a. (2010-2012). A GUIDE TO POLYCARBONATE IN GENERAL. Retrieved from http://www. ptsllc.com/intro/polycarb_intro.aspx
Figures 1. http://quaedam.files.wordpress.com/2009/01/cdrom.jpg 2-6. http://www.duplication.ca/cd-process.htm
Polycarbonate0 An In depth report