POLYMER COMPOSITES 2 Mannu Seminar - I

POLYMER COMPOSITES:

1 POLYMER COMPOSITES SEMINAR – I Feb. 2011 By MANINDRA TRIHOTRI Ph.D. Scholar No. 0113205003 Department of PHYSICS Maulana Azad National Institute of Technology, BHOPAL

OUTLINE:

2 OUTLINE Introduction Development of Polymers Composites Polymer + Composite Recent Trends Future Applications & Conclusion Reference

HISTORY OF POLYMERS:

3 HISTORY OF POLYMERS The Nobel Prize in Chemistry (2000) "for the discovery and development of conductive polymers“ Hideki Shirakawa Alan J. Heeger Alan G. MacDiarmid We are used to polymers (plastics) being somehow the opposite of metals. They insulate, they do not conduct electricity. Yet Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa have changed this view with their discovery in 1977 that a polymer, polyacetylene, can be made conductive almost like a metal. A. J. Heeger, A. G. MacDiarmid, H. Shirakawa; J. Chem. Soc., Chem. Commun. 1977 , 578 – 580 (1,2)

POLYMERS:

4 POLYMERS A Polymer is a substance composed of molecules with large molecular mass composed of repeating structural units or monomers connected by covalent bonds. Industrial Important Polymers Plastics Elastomers/Rubber Thermoplastics Thermosettings Depending upon how they are structurally & chemically bonded. Its nomenclature is based on the types of monomers. It is in the study due to its conducting properties after 1977 (1,2) .

Amazing Result:

5 Amazing Result Polyacetylene Iodine-doped Polyacetylene Polyacetylene conductivity increases by nearly ten orders of magnitude after iodine doping. http://nobelprize.org/nobel_prizes/chemistry/laureates/2000/public.html (3)

What makes polymers conductive ?:

6 What makes polymers conductive ? The conductivity depends on the number of charge carriers in the materials & their mobility. Two conditions to become conductive : 1- The first condition for this is that the polymer consists of alternating single and double bonds, called conjugated double bonds.

What makes polymers conductive ?:

7 What makes polymers conductive ? Conducting polymers are (almost) all conjugated having extended delocalized pi bonds (sp 2 hybridized) along the polymer backbone.

What makes polymers conductive ?:

8 What makes polymers conductive ? In conjugation, the bonds between the carbon atoms are alternately single and double. Every bond contains a localised “sigma” (σ) bond which forms a strong chemical bond. In addition, every double bond also contains a less strongly localised “pi” (π) bond which is weaker. π bond metal chain Conjugated polymers have a low electrical conductivity of around 10 -10 to 10 -8 siemens/cm & they were called as semiconductor (4) .

What makes polymers conductive ?:

9 What makes polymers conductive ? 2- The second condition is that the plastic has to be disturbed - either by removing electrons from (oxidation), or inserting them into (reduction), the material. The process is known as Doping . There are two types of doping: 1- Oxidation with halogen Br 2 , I 2 , H2So 4 , AlCl 3 (or p- doping). 2- Reduction with alkali metals – Na , K, Li, ( n -doping).

What makes polymers conductive ?:

10 What makes polymers conductive ? The game offers a simple model of a doped polymer. The pieces cannot move unless there is at least one empty "hole". In the polymer each piece is an electron that jumps to a hole vacated by another one. This creates a movement along the molecule - an electric current.

Doping process:

11 Doping process The halogen doping transforms polyacetylene to a good conductor. Oxidation with iodine causes the electrons to be jerked out of the polymer, leaving "holes" in the form of positive charges that can move along the chain. The iodine molecule attracts an electron from the polyacetylene chain and becomes I 3 ֿ . The polyacetylene molecule, now positively charged, is termed a radical cation, or polaron .

Doping process:

12 Doping process The lonely electron of the double bond, from which an electron was removed, can move easily. As a consequence, the double bond successively moves along the molecule. The positive charge, on the other hand, is fixed by electrostatic attraction to the iodide ion, which does not move so readily. Highest values reported for the conductivity upto now are for stretch oriented polyacetylene of about 80 K Siemens/cm.

Factors that affect the conductivity:

13 Factors that affect the conductivity 1- Density of charge carriers. 2- Their mobility. 3- The direction. 4- Presence of doping materials. 5- Temperature.

COMPOSITES:

14 COMPOSITES A macroscopic combination of two or more fundamental materials having an identifiable interface. One of the material called reinforcing face (Filler) is in the form of fibers/particles and are embedded in the other material called matrix phase (Polymer) They are considered structural engineering materials because they are designed for a specific engineering application.

Composite Structure:

15 Composite Structure Continuous phase – MATRIX Polymeric matrices can include both thermosetting and thermoplastic polymers. Thermosetting polymeric matrices include epoxies, polyesters, phenolics and silicones. Thermoplastic polymeric matrices include nylon 6,6, polycarbonate and polystyrene Discontinuous phase – FILLER They can act as a reinforcing material thereby improving the mechanical properties of the original materials. They can also reduce costs because they are generally cheap and plentiful and serve to extenuate the host material. They were of two types: Fibers which are used for reinforcement ( Glass, carbon or graphite and Kevlar) Non-fibers/particulate which act as reinforcing material or cost reducing material

NATURE OF POLYMER + COMPOSITE:

16 NATURE OF POLYMER + COMPOSITE Polymer Matrix Composite (PMC) is the material consisting of a polymer (resin) matrix combined with a fibrous reinforcing dispersed phase. Reinforcement of polymers by strong fibrous network in PMC gives the following properties: High tensile strength High stiffness High Fracture Toughness Good abrasion resistance Good puncture resistance Good corrosion resistance Low cost.

NATURE OF POLYMER + COMPOSITE:

17 NATURE OF POLYMER + COMPOSITE The main disadvantages of Polymer Matrix Composites (PMC) are: Low thermal resistance High coefficient of thermal expansion.

Recent trends in Polymer Composite:

18 Recent trends in Polymer Composite Researchers are investigating the electrical, dielectric, mechanical and thermal properties of different Polymer composite and nanocomposites using different matrix and filler combinations (5,6,7,10) . Scientists are also working on its application to field emission and biosensing (8) . They are developing a novel DNA sensor technology for simple and rapid gene detection. Mostly the researchers are using the CNT as a filler for their studies which makes it expensive.

FUTURE:

19 FUTURE Different types of fillers/nanofillers can be used to develop composites using thermoset and thermoplastic polymer. Different processes of making the composites can be used.

APPLICATON:

20 APPLICATON Group1 Electrostatic materials Conducting adhesives Electromagnetic shielding Printed circuit boards Artificial nerves Antistatic clothing Piezoceramics Active electronics Aircraft structures Group 2 Molecular electronics Electrical displays Chemical, biochemical and thermal sensors Rechargeable batteries and solid electrolytes Drug release systems Optical computers Ion exchange membranes Electromechanical actuators

BIBLIOGRAPHY:

21 BIBLIOGRAPHY H. Shirakawa, E.J. Louis, A.G. MacDiarmid, C.K. Chiang and A.J.Heeger, J Chem Soc Chem Comm (1977) 579 T. Ito, H. Shirakawa and S. Ikeda, J.Polym.Sci.,Polym.Chem. Ed. 12 (1974) 11–20 http://nobelprize.org/nobel_prizes/chemistry/laureates/ 2000 /index.html Sirringhaus,H. (2005) . “Device Physics of Solution-Processed Organic Field Effect Transistor”. Advanced Materials 17:2411 Nigrawal A.,Chand N. “Development and electrical Characterization of Carbon Soot Filled Polyester Graded Composite” Materials and Design (2010) . D. Kim, Y. Kim, Kyungwho Choi, J. C. Grunlan “American Chemical Society” Vol. 4 No.1 513-523 (2010) Wayne E. Jones Jr. , Jasper Chiguma , Edwin Johnson , Ashok Pachamuthu, Daryl Santos Materials ( 2010) , 3 , 1478-1496 R.B. Rakhi, K. Sethupathi and S. Ramaprabhu, Carbon , 46 , 1656-1663. ( 2008) Xai Na, JiaoQingjie, Zang Chongguang, Wang Chenglong, Liu Yuanyuan, Materials and Design (2009). P. Thomas, S. Satapathy , K. Dwarakanath, K. B. R. Varma eXPRESS Polymer Letters Vol.4, No.10 (2010) 632–643

THANK YOU:

22 THANK YOU