Presentation on theme: "1 Polymers Chapter 8- Part 1 Manufacturing Processes, 1311 Dr Simin Nasseri Southern Polytechnic State University."— Presentation transcript:
1 Polymers Chapter 8- Part 1 Manufacturing Processes, 1311 Dr Simin Nasseri Southern Polytechnic State University
Manufacturing Processes Prof Simin Nasseri POLYMERS Fundamentals of Polymer Technology Thermoplastic Polymers Thermosetting Polymers Elastomers Guide to the Processing of Polymers
Manufacturing Processes Prof Simin Nasseri Polymer A compound consisting of long ‑ chain molecules, each molecule made up of repeating units connected together There may be thousands, even millions of units in a single polymer molecule The word polymer is derived from the Greek words poly, meaning many, and meros (reduced to mer), meaning part Most polymers are based on carbon and are therefore considered organic chemicals
Manufacturing Processes Prof Simin Nasseri Natural polymers! Natural Polymer: Silk fiber is produced by silk worms in a cocoon, to protect the silkworm while it metamorphoses in a moth. The gooey liquid in okra, is a natural polymer used as a food thickener for thousands of years!
Manufacturing Processes Prof Simin Nasseri A tire is actually one giant network molecule, a molecule so big it takes two hands to pick it up! A bowling ball contains only one molecule, too. Polymer
Manufacturing Processes Prof Simin Nasseri Types of Polymers Polymers can be separated into plastics and rubbers. As engineering materials, it is appropriate to divide them into the following three categories: 1.Thermoplastic polymers 2.Thermosetting polymers 3.Elastomers Plastics Rubbers
Manufacturing Processes Prof Simin Nasseri Thermoplastic Polymers - Thermoplastics Solid materials at room temperature but viscous liquids when heated to temperatures of only a few hundred degrees About 70% of the tonnage of all synthetic polymers produced This characteristic allows them to be easily and economically shaped into products They can be subjected to heating and cooling cycles repeatedly without significant degradation Symbolized by TP
Manufacturing Processes Prof Simin Nasseri Thermosetting Polymers - Thermosets Cannot tolerate repeated heating cycles as thermoplastics can When initially heated, they soften and flow for molding Elevated temperatures also produce a chemical reaction that hardens the material into an infusible solid If reheated, thermosets degrade and char rather than soften Symbolized by TS
Manufacturing Processes Prof Simin Nasseri Elastomers (Rubbers) Polymers that exhibit extreme elastic extensibility when subjected to relatively low mechanical stress Although their properties are quite different from thermosets, they share a similar molecular structure that is different from the thermoplastics Some elastomers can be stretched by a factor of 10 and yet completely recover to their original shape! Wow !!
Manufacturing Processes Prof Simin Nasseri Examples of Polymers Thermoplastics: Polyethylene (PE), polyvinylchloride (PVC), polypropylene (PP), polystyrene, and nylon Thermosets: Phenolics, epoxies, and certain polyesters Elastomers: Natural rubber (vulcanized) Synthetic rubbers, which exceed the tonnage of natural rubber
14 Why are polymers important?
Manufacturing Processes Prof Simin Nasseri Reasons Why Polymers are Important: Plastics can be molded into complex part shapes, usually with no further processing Very compatible with net shape processing On a volumetric basis, polymers: Are cost competitive with metals Generally require less energy to produce than metals Certain plastics are translucent and/or transparent, which makes them competitive with glass in some applications
Manufacturing Processes Prof Simin Nasseri General Properties of Polymers Low density relative to metals and ceramics Good strength ‑ to ‑ weight ratios for certain (but not all) polymers High corrosion resistance Low electrical and thermal conductivity
Manufacturing Processes Prof Simin Nasseri Limitations of Polymers Low strength relative to metals and ceramics Low modulus of elasticity (stiffness) Service temperatures are limited to only a few hundred degrees Viscoelastic properties, which can be a distinct limitation in load bearing applications Some polymers degrade when subjected to sunlight and other forms of radiation
Manufacturing Processes Prof Simin Nasseri Polymer notes! (the first one was made in Australia) Note Printing Australia (NPA), produced Australia's first polymer banknote in 1988, setting a new world standard in banknote technology. The numerous benefits of polymer banknotes include improved security, durability, cost effectiveness, processibility and environmental responsibility.
Manufacturing Processes Prof Simin Nasseri Polymer notes! By 1996, Australia had issued the world's first complete series of circulating polymer banknotes. NPA has also produced polymer notes for Thailand, Papua New Guinea, Sri Lanka, Malaysia, Singapore, Brunei, Indonesia, Kuwait, Samoa, New Zealand, Romania, Bangladesh, Solomon Islands, Mexico, Nepal, Vietnam, and Chile.