Introduction to Polymer Science and engineering
- 2. Course Outline • Introduction to polymer, history, definition, modern aspects • Polymer Terminology • Nature of bonding forces in polymer • Classification of polymers • Chemical structures of polymers • Polymerization mechanisms • Properties of polymer • Advantages and disadvantages of polymers • Processing and manufacturing of polymers • Characterization of polymer • Application of polymers • Advanced Polymers • Environmental effects • Polymer recycling
- 3. Why we need to get introduced to polymer science? • Thinking and going back about the ages of mankind, we will see that human civilization was marked by several ages, and those are all based on the materials which are mostly used for their day to day living and self defence. For example, we have the • Stone Age, • Bronze Age, • Iron Age (Steel , Aluminium ) • Polymer material Age (Carbon based materials) • Probably going forward we will have the age of elements, which includes silicon, uranium, lithium, and so on. However currently, we are in the age of polymers.
- 4. • Lord Alexander Todd, who was the President of Royal Society of London, and Nobel laureate in chemistry in 1957 once said that • Now it is known that polymers are one of the most important materials in our everyday life. Irrespective of different industries or various research areas, the basic understanding of polymers is very much essential for getting success in regular activities.
- 5. Polymers are the materials of choice • One of the biggest success stories in new materials developed over the last century. • Polymers have replaced and are increasingly replacing conventional materials like wood, metals, stone, or ceramics in more and more applications. • At present, when we think about any new material application, polymers are very often the choice of the material. • Polymers are everywhere. Plastics, rubber, paints, surface coatings, resins, adhesives, synthetic fibers and several specialty applications
- 7. Why are polymers so popular? • When we think about any material applications, we need that the materials should have high strength. That means, • It should be able to bear a large amount of load. • It should be resilient, which means it should give comfort, soft feeling, and preferably we can have materials that will have transparency, and of course if anybody wants to have all these properties at a lower cost. • The conventional non-polymeric materials like metal, ceramics, glass, wood, etc., do not satisfy all these characteristics. For example, if you consider glass, they are having very high strength and can bear a high load but the problem is that it is brittle. • So, we need to be very careful while using, otherwise glass breaks and there is a hazard involved in that. • To talk about metal, metals are very difficult to get in a transparent condition, and also prolonged use in ambient conditions results in corrosion. Besides of course, these materials are much heavy material. We want a material which would be light so that it can be carried easily and transport cost comes down. So, polymers give or satisfy all these properties.
- 8. • Other beneficial properties of the polymers are that they are durable. The polymers are made of mainly carbon, along with hydrogen, oxygen. Most of the regular plastics or polymers which we use are hydrophobic in nature. As a result, they are resistant to hydrolysis and are stable against electrochemical corrosion. • They are very light. So, if we consider the strength versus weight, the polymer gives the maximum strength versus weight ratio. For a given weight of the material, we can achieve high strength in polymers. Polymers give the design flexibility because the melting temperature or processing temperature of polymers is much lower. • So, we can make products of polymers at a low cost and spending much lower energy and because of the easy melting of the polymers, a lot of polymeric products can be designed as per choice. So basically it gives you design flexibility.
- 9. • Polymers are generally thermal and electrical insulators which is a big advantage. • Additionally, it gives feedstock flexibility as most polymers are made from petroleum fractions, though they can be also made from natural gases and coal. Some polymers can also be made from agricultural and forest products and biomass as an alternative resource. • Mostly polymers are made from synthesized petroleum products. So that means, polymers are part of the petrochemical industry.
- 10. What are polymers? • The word “Polymer” is derived from two Greek words, ‘Poly’ that means many (numerous) and ‘Mer’ which means units. • Polymers are a large class of materials consisting of many small molecules (called monomers) that can be linked together to form long chains, thus they are known as macromolecules. Atypical polymer may include tens of thousands of monomers. Because of their large size, polymers are classified as macromolecules.
- 11. What are polymers? Polymers are very large molecules made of many smaller repeating units. ‘poly’ – many ‘mer’ – part. Each individual part is called a monomer. Polyethylene – one type of ‘plastic’ Typical number of repeat units: 1,000- 100,000
- 12. • Macromolecule that is formed by linking of repeating units through covalent bonds in the main backbone • Properties are determined by Molecular weight Length Backbone structure Side chains Crystallinity
- 13. Consequence of short and long chains
- 14. • If we want to compare a small molecule and a polymer molecule, we imagine small molecules as grains of rice in a bowl. We can put a spoon and easily take out a spoon of rice from it. That is possible because the rice grains are small, so they do not entangle with each other and we can easily separate them. The individual molecules, in this case, the rice grains, behave independently. They do not interfere with the movement of other molecules. • Now when we compare polymeric molecules, because they are large, it is found that they are entangled like if we have a bowl of noodles. Then we put the spoon and want to take it out, we cannot take a single chain of noodles from the sample or the bowl. Because of the large length, they are entangled with each other. So polymer molecules are completely entangled and as a result the molecules cannot move independently. • Now this gives the advantageous properties like strength of the polymers and the toughness of the polymers. The polymer chains, as they are entangled, if you apply some force, they can easily dissipate the force and exhibit high strength and toughness and so on. The high molecular weight helps in providing superior properties like high tensile strength, impact-resistant, toughness, melt viscosity, high melting temperature, etc.,
- 15. Polymer terminology • mer: a unit • monomer: one unit (The small molecule which combine with each other to form polymer molecules ) • trimer: three units • tetramer: four units • polymer: many units (A long chain molecule formed from many monomers joined together) • pre-polymer: growing towards being a polymer • oligomer: few units fixed in size (low molecular weight) • High polymer: Polymer with high molecular weight
- 16. Polymer terminology • homopolymer: Polymers consisting of identical monomer units are called homo-polymers • Copolymers: monomers of different chemical unit structures are called hetero-polymers or copolymers. • Polymerization: The chemical reaction by which the monomers are combined to form the polymer is called polymerization. • Cross-link: A chemical bond that joins one polymer chain to another. Poly ethylene vinyl acetate
- 17. Based on the arrangement of monomeric units (structural units), copolymers can be classified as: Random copolymers In random copolymers, no definite sequence of monomer units exists. Poly (A-ran-B) A – B – A – A – A – B – A – B – B – A – A – B – A Alternating copolymers A regular alternating sequence of two monomer units Poly (A-alt-B) A – B – A – B – A – B – A – B – A – B – A – B
- 18. Block copolymers - Combination of one block of monomers and another block of monomers - They are often formed by ionic polymerization process. • Ex) AB diblock copolymers A – A – A – A – A – B – B – B – B – B • Ex) ABA triblock copolymers A – A – A – A – B – B – B – B - A – A – A – A
- 19. Graft Copolymers Two preparation methods 1) Monomer B can be polymerized from sites along the length of polymer A. 2) Two preformed polymers derived from A and B can be induced to react with each other to form a graft structure. A – A – A – A – A – A – A – A – A – A – A – A – B – B – B – B – B – B – B – B – B – B – B – B
- 20. History of polymers • Initially, polymer science was born in the great industrial laboratories of the world. • Polymers existed in natural form for a long time. For example, in our body, we have macromolecules like DNA, RNA, proteins, and polysaccharides, which play a crucial role in human, plants and animal life. • In ancient times these naturally occurring polymers were exploited by man for making several items, like they were used for clothing, decoration, shelters, tools, and also for printing materials, etc. • So the origin of today’s polymer industry happened in the 19th century
- 21. In 1907 the first fully synthetic polymers were invented by Leo H. Baekeland by reaction of phenol with formaldehyde, and the product was called Bakelite. In 1910 this product was commercialized.
- 22. The concept of macromolecules • The polymer industry was running well without a proper understanding of the nature of polymers. And for over a century, scientists believed that the polymers consisted of physically associated aggregates of small molecules like micelles or surfactants. • Only in 1920 Hermann Staudinger, a professor of organic chemistry at ETH Zurich, first conceived that the polymers are made of very large molecules containing a large sequence of simple chemical units linked together by a covalent bond. So, this is the first time somebody conceived that polymers are large molecules that were made of by linking the repeating units by covalent bonds. • That is the reason why Hermann Staudinger is considered as the father of macromolecular chemistry. • So he propounded the revolutionary concept that macromolecules can be formed by linking a large number of small molecules using covalent bonds. He could not give experimental evidence to prove the fact. So basically, from his intuition and imagination, he proposed and published a paper titled Uber Polymerization in the journal in 1920. That is the year, which has been considered as the start or beginning of macromolecules as a science.
- 23. • During the late 1920s, Staudinger provided additional evidence based on viscometry to confirm that the molecular weights remain unchanged during the chemical modification of polymers. • But at the end of the 1920s and during the 1930s Staudinger’s macromolecular concept found increasing acceptance by other chemists. That was especially due to the work by Herman Mark and Wallace H. Carothers and finally, in 1953, Staudinger was awarded the Nobel Prize for his discovery of his work on macromolecular chemistry.
- 24. • Later Paul J. Flory developed a fundamental understanding of both theoretical and experimental physical chemistry of macromolecules. So basically Staudinger along with these three other scientists Herman F. Mark, Wallace H. Carothers, and Paul J. Flory should be considered as the pillars of macromolecular chemistry.
- 25. • Now following this understanding, there was plenty of activities among scientists for developing new polymers. Also, there was large-scale polymer production happening during the 1950s to 1970s and which continued till the 1990s. • So basically, in this time-frame, the polymers were discovered which was facilitated by the cheap availability of petrochemicals. • Now, when we move forward to the new millennium and beyond 2020 polymer sciences are looking for newer applications or more specialized applications for polymers. So basically from 2020 onwards, we have the second century of polymer sciences.
- 26. What is textile? • Textile is the second basic needs of human being. It has such an important bearing on our daily lives that everyone needs to know something about them. • The basic meaning of Textile is woven or knitted fabric made from yarn. But apart from fibre, yarn and fabric or any other product made from these combinations are defined Textiles. Textile is also associated with clothing production. Fibre is the raw material of textile which may be natural or man-made.
- 27. What is Textile Industry ? • The industry is primarily concerned with the design and production of yarn, cloth, clothing, and their distribution. The raw material may be natural, or synthetic using products of the chemical industry. • The basic Textile materials are as follows: Fibre (Polymers) ↓ Yarn ↓ Grey Fabric ↓ Finished Fabric ↓ End Product
- 28. Textile fibres
- 29. Man-made fibres
- 31. Polyester Chips Natural and synthetic polymer Carbon
- 32. Conversion of polymer to products Weaving Knitting Non-Woven
- 33. The textile industry in Ethiopia • Based on Ethiopian country data, in the last 5 to 6 years, the textile, and apparel industry have grown at an average of 51% and more than 65 international textile investment projects have been licensed for foreign investors, during this period. • The growth in the textile industry is directly linked to the Government’s move to set up an industrial development strategy. This step of the Ethiopian Government to prioritize designing incentives and policies to attract investment in view of worldwide competition has played a big role in the development of their economic status.
- 34. What is Technical Textile? • Textile materials and products manufactured primarily for their technical application and performance properties rather than their aesthetic or decorative characteristics.
- 35. Types of technical textiles
- 36. Introduction of Plastics Materials
- 37. Introduction of Plastics Materials