Polycarbonate

polycarbonate

1. POLYCARBONATE Presented by:- Himanshu Kr. Bhatt 1508003

2. I ntroduction Polycarbonates  ( PC ) are a group of thermoplastic polymers containing carbonate groups in their chemical structures.  Polycarbonate , an amorphous thermoplastic, is considered to be a well proven technical plastic. PC used in engineering are strong, tough material, and some grades are optically transparent.( Lexan* 9030 ) Alternative titles : Lexan, Merlon, ZELUX ,PC

3. History In  1953 , polycarbonate was discovered independently by Dr. H. Schnell of Bayer AG, Germany and by D. W. Fox of General Electric Company, USA. It has been used in commercial applications since the late 50's.  Polycarbonate was initially used for electrical and electronic applications. polycarbonate’s outstanding combination of beneficial characteristics made it the material of choice for many other applications like CD/DVD, all type of data storage device, water bottles , car head lamps and many more.

4. Structure A polycarbonate molecule is composed by a Bisphenol A part and a carbonate group.

5. Structure cont. Bisphenol A contains two aromatic rings, which are responsible for PC’s stiff backbone. The Bisphenol A group also contributes to PC’s inability to crystallize. This amorphous structure gives the polymer its particular transparency. The Characteristic high glass transition temperature (Tg = 145ºC) of PC is caused by the minimal molecular rotation about the bonds .

6. Synthesis Polycarbonate is synthesis by two ways : 1- Transesterification (or ester exchange) 2- Phosgene method

7. Transesterification Transesterification is the process of exchanging the organic group R″ of an ester with the organic group R′ of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst . Alcohol + ester diff. alcohol + diff. ester

8. Cont. In the transesterification mechanism, the carbonyl carbon of the starting ester (RCOOR 1 ) undergoes nucleophilic attack by the incoming alkoxide (R 2 O − ) to give a tetrahedral intermediate, which either reverts to the starting material, or proceeds to the transesterified product (RCOOR 2 ).

9. Cont.. Here in case of polycarbonate the reaction takes place between Bisphenol-A (alcohol)and diphenylcarbonate (ester) gives a polycarbonate as follows:-

10. + Bisphenol-A diphenylcarbonate carbonate Bisphenol-A POLYCARBONATE NaOH

11. Mechanism

12. 2 + + -

13. +

14. Phosgene method The main polycarbonate material is produced by the reaction of bisphenol A (BPA) and phosgene COCl 2 The overall reaction can be written as follows:

15. Mechanism

16. Advantage and Disadvantage Transesterification Advantages Solvent Free Potentially Phosgene Free Disadvantages Intermediate Molecular Weight Phosgen Advantages High Molecular Weight Excellent Optical Clarity and color Disadvantages Phosgene based Uses H 2 O and CH 2 Cl 2

17. Processing

18. Process description BPA and DPC are fed into the preparation tank where they are thoroughly molten . In order to achieve the high-purity monomer required for the production of high-quality polycarbonate suitable purification steps such as distillation, filtration and melt crystallization are considered.

19. The pre-heated raw materials are fed in liquid form in a defined molar ratio into the transesterification reactor where they are mixed with catalysts and heated up to the desired transesterification temperature . During the formation of polymer chains phenol begins to split-off . After the transesterification has been finished the short polymer chains, the so-called oligomers, are discharged and fed into the prepolycondensation I reactor for the next reaction step

20. Using higher temperatures and a lower vacuum, molecules of mid-size chain length are built-up . The product is then transferred to the prepolycondensation II reactor for further chain growth and subsequently to the final polycondensation reactor .

21. The final polycondensation reactor is used to achieve the desired polymer chain length and hence the desired properties of the Polycarbonate Both the prepolycondensation II stage and final reactor are equipped with a horizontal disc-ring agitators that provide a high surface area to ensure easy mass transfer and chemical reaction.

22. Manufacturing Extrusion The molten PC is passed through a die that gives the material its final shape. After this, the melt is cooled rapidly. Long pipes and sheets are created by this process Molding The PC melt is pressed into a mold with the defined shape of the final product. The melt is then cooled inside the mold. This process is ideal for specific parts such as automotive and computer parts

23. Characteristics of PC High mechanical stability Good thermal stability Excellent impact toughness Good weathering stability High light transparency (panels are transparent)

24. Cont.… High dimensional stability Low moisture absorbtion Good dielectric properties Self-extinguishing Good resistance to high energy radiation

25. Physical and Mechanical Properties G ood tensile strength without excessively high rigidity. E xceptionally good impact resistance . The stress-strain behavior of PC is characterized by a wide creep range between the yield point and fracture The sear module is temperature dependent and shows rapid reductions in rigidity above +120ºC.

26. Due to their high impact resistance, PC panels are some of the most shatter-proof glazing materials . Uncrystallized polycarbonate has excellent transparency and have high refractive index of about 1.584. The relative rigidity of the chain causes high viscosity in the liquid state . Non- toxic in nature and easily coloured. Highly recyclable and cost effective.

27. Benzene rings restrict the flexibility of the molecule. Due to bisphenol-A it Is amorphous in nature. Due to rigid backbone T g =145   °C and T m = 225-250 °C Excellent resistance to shock even when cold.

28. Chemical P roperties Resistance to dilute mineral acid but poor resistance to aromatic, alkali, chlorinated hydrocarbons. Dilute Acid (good) Alcohols (good) Aliphatic Hydrocarbons (good) Oils and Greases (moderate) Dilute Alkalis (poor) Aromatic Hydrocarbons (poor) Halogenated Hydrocarbons ( poor)

29. PC absorbs only small quantities of water (<0.6%) and its mechanical properties are not affected by it . PC can be used for making objects frequently washed with hot or sterilized water, but a long period of time in hot water (0 > 60°C) causes a decomposition resulting in a drop in shock resistance . PC is fairly stable in the presence of ozone. Stability in UV light is not exceptional and PCs turn yellow fairly quickly . Certain grades are approved for medical use .

30. Thermal properties PC has good heat and cold stability . Above the glass transition point of +140ºC however, PC starts to soften rapidly. PC is practically self-extinguishable i.e., resistant to fire.

31. Dimensional properties Polycarbonate, as other amorphous polymer , offer limited retraction when molded(>0.6%) I ts low absorption of humidity gives it good dimensional stability in a humid atmosphere. PC has good creep resistance, especially when reinforced with fiber glass.

32. Electrical properties: Polycarbonate has good insulating properties little affected by variations in temperature or humidity. Dielectric constant is higher than PTFE and polyolefin

33. Application Electrical and Electronics components :- due to good insulating and high dielectric strength pc is used for making of- Protective case for mobile phones

34. Switch board Film capacitors Electric charger LED

35. TRANSPARENT ENCLOSURES

36. Construction materials PC’s outstanding strength makes it suitable for bullet-resistant or shatter-resistant glass application. PC wall for sound insulation

37. STRUCTURAL GLAZING

38. Data storage Compact disk Digital versatile disc

39. Medical application Filters housing, tube connectors, surgical staples (due to strength, purity, transparency, ability to stand all sterilization(steam, gamma-rays etc..) ) which shows its bio-inertness

40. General application.  Due to its low weight and high impact resistance, polycarbonate is the dominant material for making automotive headlamp lenses . The cockpit canopy of  jet fighter is made from a piece of high optical quality polycarbonate.

41. Passenger cars fleet of train is made of polycarbonate. PC’s relatively low weight in comparison to other high strength materials and its high ductility make it attractive to be used in lenses and windows

42. Polycarbonate Blends Polycarbonate is blended with other polymers to enhance its properties. Some of which are :- PC/ABS blend In a compounded blend of Polycarbonate and ABS. The PC contributes impact and heat distortion resistance, while the ABS contributes processability and chemical stress resistance, and cost reduction below PC.

43. P roperties of PC/ABS Impact resistance between ABS and PC Strength and stiffness between pc and abs Heat resistance superior to ABS, less than PC Flame retardant system more stable in processing than ABS

44. uses Portable appliances, flashlights, phones Laptop computer cases Keyboards, monitors, printer enclosures

45. automotive instrument panel retainers wheel covers small tractor hoods non-professional safety helmets

46. PC/PBT( polybutylene terephthalate) In a compounded blend of Polycarbonate and PBT. The PC contributes impact, stiffness and heat resistance, while the PBT contributes chemical resistance. The usual moisture sensitivity of the crystalline PBT is overcome by the PC in the blend .

47.   Properties of PC/PBT impact resistance low temperature impact resistance, ductility heat resistance chemical resistance

48. What is made with PC/PBT Automotive bumpers Automotive side moldings Lawn and garden tractor hoods

49. Hand tool housings Irrigation components Wire connectors

50. How do these properties compare to other materials ? One of the biggest advantages of polycarbonate is its impact strength. The following diagram compares the impact strength of polycarbonate to other commonly sold plastics .

51. Polycarbonate does have its disadvantages. It has only fair chemical resistance and is attacked by many organic solvents. It is also fairly expensive compared to other plastics. It has been as much as double the price of ABS . In applications where lower heat and impact are needed, ABS can be quite a bargain compared to polycarbonate.

52. How is polycarbonate sold ? In general, the primary distinguishing characteristic of a grade of polycarbonate is its melt flow . The only exceptions are glass fiber reinforced grades, which are sold based on the percentage of glass fiber used in the production of the plastic.

53. There are two major types of polycarbonate sold. Virgin polycarbonate is polycarbonate which has not been altered from the time of original manufacturing to the purchase of the product.  Polycarbonate regrind comes from polycarbonate that is taken from an end-user and ground into pellets

54. Thank you for your Attention!