1. CORPORATE TRAINING AND PLANNING
Polyesters
Polyesters are among the more versatile synthetic polymers.
The common methods of synthesising simple esters are used to make polyesters.
These include direct esterification (1), transesterification (2) and the reaction of alcohols (3) with acyl chlorides or anhydrides (4).
CORPORATE TRAINING AND PLANNING

2. Commercially important Polyesters
Poly(ethylene terephthalate) (PET)
Poly(trimethylene terephthalate)
Poly (ethylene napthalate-2,6-dicarboxylate) (PEN)
CORPORATE TRAINING AND PLANNING

3. Commercially important Polyesters
Poly (butylene terephthalate) (PBT)
Poly (4-hydroxybenzonate)
Polycarbonate
CORPORATE TRAINING AND PLANNING

4. CORPORATE TRAINING AND PLANNING
Polyethylene Terephthalate (PET)
Linear polyesters were studied by Carothers during his classical researches for development of Polyamides.
But it was Whinfield and Dicson who developed PET at Calico Printers Association, England I 1941 (As Fibres, Terylene and Dacron and as Film, Melinex and My lar, with the expiry of the basic ICI patents on PET there was considerable development in terephthalate polymers in the early 1970’s.
More than a dozen companies introduced PBT as an Engineering Plastics during this time.
The fiber in the name of Kodel and Film in the name of Kodar was developed by Kodak. .
CORPORATE TRAINING AND PLANNING

5. CORPORATE TRAINING AND PLANNING
Polyethylene Terephthalate (PET)
PET was also the basis of glass filled engineering polymer (Rynite) introduced by DuPont in 1970’s. Towards the end of 1970’s PET was used for the manufacture of biaxial oriented bottles .
CORPORATE TRAINING AND PLANNING

6. CORPORATE TRAINING AND PLANNING
Monomer Ingredients for PET
The ingredients which are used for PET are ethylene glycol and dimethyl teraphthalate.
HO – CH2 – CH2 – OH
Ethylene glycol
Dimetyl terephthalate
CORPORATE TRAINING AND PLANNING

7. Chemistry of Preparation of PET
The PET polymers is produced by the reaction of ethylene glycol and Terephthalic acid or Dimethyl terephthalate in the presence of metal acetate catalyst. This process is called ester exchange process.
In this process, a low molecular weight diester, known as the monomer is first produced by reacting 1 mol. or dimethyle terephthalate with about 2.1 – 2.2 mol ethylene glycol at 150°C in the presence of catalysts, such as antimony trioxide and cobaltous acetate.
CORPORATE TRAINING AND PLANNING

8. Chemistry of Preparation of PET
In addition to this diester, di-2-hydroxyethyl terephathalte, some oligomers of following general structure, are also produced.
HO-(CH2 ) 2 -O[O-C- O -COO-(CH2 ) 2 -O] n-H
When n = 1, 2, 3
Methanol formed during the condensation is removed using a distillation column. The monomer is then heated to 270° - 280°C with removal of volatiles under reduced pressure down to 1 mm Hg. Heat and vacuum are employed to increase the molecular weight with concurrent removal of volatile products such as water /alcohol and glycol.
n CH3OOC - O - COO CH3 + n HO - CH2 - CH2 - OH
O O
- [C - O - C - O -CH2- CH2 - O -] n + 2n CH3 OH
CORPORATE TRAINING AND PLANNING

9. CORPORATE TRAINING AND PLANNING
Manufacturing of PET
PET Polymers are manufactured by a stage-wise melt polymerization process consists of transesterification, pre-polymerization and finishing polymerization steps.
Continuous melt polycondensation process for PET manufacture.
CORPORATE TRAINING AND PLANNING

10. CORPORATE TRAINING AND PLANNING
Manufacturing of PET
In the transesterification stage dimethyl temphthalate (DMT) or terephthalic acid (TPA) is converted into bishydroxy ethyl terephthalate in the presence of metal acetate catalyst.
Ethylene glycol (EG) DMT, and catalyst are fed at a molar ratio of 1.7 to 2.0:1 (with TPA this ratio is 1-3 to 1.5:1) and a temperature of °C. This stage takes 3-4 hr.
The reaction byproduct methanol (Water When TPA) is used is separated from EG vapors in a reflux column.
CORPORATE TRAINING AND PLANNING

11. CORPORATE TRAINING AND PLANNING
Manufacturing of PET
After adding stabilizer and additives, the prepolymer is forced through a superfine fitter to the second (pre-poly condensation) stage.
The poly condensation reaction is performed under vacuum (15-25 torr) and elevated temperature. (280 – 300°C).
The resulting EG is removed by a vacuum pump while the prepolycondensation product – a low molecular weight (DP= 30) relatively non-viscosity material (40 poise) is pumped to the finishing poly condensation stage after a residence time of about 2 hrs.
CORPORATE TRAINING AND PLANNING

12. CORPORATE TRAINING AND PLANNING
Manufacturing of PET
The finishing polymerization stage, which is operated at 0.5 – 1 torr, requires special wiped film or extruder type reactor in order to handle the high viscosity of the polymer ((DP = 100), few thousand poise).
Many manufacturer have devised their own proprietary agitation systems to minimize the build-up of the solidifying polymer layers.
The EG vapours contaminated with oligomers are drawn off through a special condensing system and sent to a recovery unit
The polymers melt can be sent to a direct spinning plant or transformed into pellets.
CORPORATE TRAINING AND PLANNING

13. Relations of Structure and Properties of PET
There are various classes of linear polyesters.
The concentration of ester groups has predominant effect on the properties of linear polyesters.
For the aromatic classes of linear polyester, decreasing the concentration of ester groups apparently leads to a reduction in melting point.
However, in such aromatic linear polyester the decrease in concentration of ester group is accompanied by the p-phenylene group concentration.
It is found from aliphatic polyester that the ester group concentration has little effect on the melting point.
In fact a decrease in ester group concentration leads to a slight increase in the melting point.
CORPORATE TRAINING AND PLANNING

14. Relations of Structure and Properties of PET
It is found that in an ester group the in chain ether link –C-O-C- increase the chain flexibility compared with a polyethylene chain to decrease the heat of fusion.
At the same time there will be some increase in inter chain attraction via the carbonyl group which will decrease the entropy of fusion.
Since these two effects almost cancel each other out there is almost no change in ester group concentration.
With all linear series of polyester as the no. of methylene groups in the repeating unit increases so the polymer becomes more like a linear polyethylene (polymethylene).
CORPORATE TRAINING AND PLANNING

15. Relations of Structure and Properties of PET
It is also observed that Tm (melting point) of a polymer with an odd no. of methylene groups in the aliphatic portion of the repeat unit is lower than for the polymer with one more but an even no. of methylene groups.
Generally, the highest melting points are obtained where the in-chain aromatic ring is of the p-phenylene type.
The materials have a disadvantage of sensitivity to water and alkaline solution.
These materials are crystalline and only proton donors that are capable of inter action with the ester groups are effective solvents.
CORPORATE TRAINING AND PLANNING

16. Characteristics of PET (For Identification)
The PET is a semicrystalline material, normally amorphous with low crystallinity and high transparency.
It is identified by sweet smell, when burns, orange flame, soot forming and melt drips.
It is scratch resistant
Melting point is 220°C
It is having short and long term thermal limit temperature respectively 135°C and 100°C
CORPORATE TRAINING AND PLANNING

17. Characteristics of PET
Outstanding chemical resistance to organic and inorganic liquids
Water repellent
Sterilizable by ethylene oxide and X-rays
Inherent good electrical property
Ability to orient
Good tensile strength
Superior strength and stiffness
Excellent dimensional stability
Excellent melt strength with slower crystallization rate
Good impact strength even at low temperature
High tear strength
Heat resistant
Flame retardant
Outstanding clarity
High gloss
CORPORATE TRAINING AND PLANNING

18. CORPORATE TRAINING AND PLANNING
Properties of PET
Properties Units Values
Specific gravity
Tensile strength MPa 51 Tensile modulus MPa Flexural modulus Mpa Elongation at break % 7
Impact strength izod, Notched, kg.cm/cm 9.25
Hardness R 105
Deflection temperature under load 0C
(1.82 Mpa)
Vicat softening point °C 75
Coefficient of linear expansion mm/mm/ 0C x 10-5
Water absorption, 24hrs % < 0.1
Refractive index
Dielectric strength KV/mm 26
Dielectric constant Hz 3.3
Power factor
Volume resistivity Ohm.m
Melting point 0C 265
Glass transition temperature °C 67
CORPORATE TRAINING AND PLANNING

19. CORPORATE TRAINING AND PLANNING
Properties of PET
Mechanical Properties
PET exhibits a high modulus up to 75°C, when it is crystalline and 40°C, when it is amorphous even when they are mechanically stressed for a long period.
Thermal Properties
PET has excellent dimensional stability.
Electrical Properties
PET has high dielectric strength and high volume resistivity. The dielectric properties are adequate for many electronics applications.
CORPORATE TRAINING AND PLANNING

20. CORPORATE TRAINING AND PLANNING
Properties of PET
Water Absorption
PET is hygroscopic and in its melt states the resin hydrolyses.
Optical Properties
The light transmission of PET differs greatly according to chemical composition.
CORPORATE TRAINING AND PLANNING

21. CORPORATE TRAINING AND PLANNING
Properties of PET
Permeability to water vapour and Gases
PET is less permeable than PVC-U.
The permeability of film is 40µm/1.58 mil.
The permeability to water vapour is higher than that of the polyolefins but lower than that of PC, PA, POM. PET films are largely odor-proof which leads to their frequent use in packaging materials in combination with PE films
CORPORATE TRAINING AND PLANNING

22. CORPORATE TRAINING AND PLANNING
Properties of PET
Chemical Properties
PET is resistant to weak acids and alkaline solutions, oils, fats, aliphatic and aromatic hyrocarbons, carbon tetrachloride.
It is not resistant to strong acids and alkaline solutions, phenol, long exposure to hot water.
The crystalline polyalkyle terephthalates are susceptible to hydrolysis which precludes their use in aqueous solution temperatures above 70°C for in steam.
PET does not show any pronounced tendency to stress cracking.
CORPORATE TRAINING AND PLANNING

23. CORPORATE TRAINING AND PLANNING
Properties of PET
Weathering Resistance
The relatively high resistance to weathering can be increased by the use of carbon black to protect against UV.
Resistance to High energy Radiation
PET is relatively resistant to high energy radiation. It is degraded more strongly only at absorbed energies of more than 100 KJ/ Kg. After 7 to 8 MJ/Kg it decomposes into powder.
CORPORATE TRAINING AND PLANNING

24. CORPORATE TRAINING AND PLANNING
Properties of PET
Flammability
PET burns with a sooty orange-yellow flame, it drips and smells sweetly aromatic. Flame retardant grades donot drip and meet the requirements of UL 94 V-0.
Toxicity
PET is suitable for applications involving contact with food stuffs and is physiologically inert.
Sterilization
PET can be sterilized in an ethylene oxide atmosphere or by irradiation.
CORPORATE TRAINING AND PLANNING

25. CORPORATE TRAINING AND PLANNING
Additives of PET
1. Functional additives
2. Fillers
3. Reinforcements
CORPORATE TRAINING AND PLANNING

26. CORPORATE TRAINING AND PLANNING
Functional Additives
1. Anti-oxidants
2. UV absorbers
3. Flame retardants
CORPORATE TRAINING AND PLANNING

27. CORPORATE TRAINING AND PLANNING
Fillers and Reinforcements
1. Mica - Fillers
2. Thermoplastics glass fiber - Reinforcements
CORPORATE TRAINING AND PLANNING

28. CORPORATE TRAINING AND PLANNING
Grades of PET
The PET is available in the following grades.
Injection moulding grade
Extrusion grade
Stretch blow moulding grade
CORPORATE TRAINING AND PLANNING

29. Processing considerations of PET
PET can be processed by the following techniques :
Injection moulding
Stretch blow moulding
Thermoforming
Extrusion
CORPORATE TRAINING AND PLANNING

30. Processing considerations of PET
PET resins are primarily for injection moulding.
PET is hygroscopic and in its melt state the resin hydrolyzes.
PET resin supplied in moisture porof containers can have a moisture content upto 0.04%, but hydrolysis can occur at a moisture level above 0.02%.
Therefore, even virgin PET directly from suppliers containers, as well as regrind, should be dried to level of less than 0.02% and maintained at that level.
Dehumidifier hopper is recommended with injection moulded PET.
Drying time values from 4 hrs. for wet resin to 2 hrs. for virgin resin at 135°C.
CORPORATE TRAINING AND PLANNING

31. Processing considerations of PET
The moulding must be carried out with dried material and because of the free flowing nature of the melt, restricted nozzles should be used and a back flow valve fitted to screw injection moulding machine.
Cylinder temperature are about 260 – 290°C.and mould temperature as high as 140°C to promote a controlled crystallization.
A significant degree of crystallinity occurs in the mould. Therefore, mould temperature should be selected carefully in order to enhance crystalline formation.
Mould temperature also influence cycle time and products quality, particularly warpage shrinkage, surface gloss depth or colour and chemical resistance.
CORPORATE TRAINING AND PLANNING

32. Processing considerations of PET
Although resin grades from the same supplier show the same melt temperature, PET from different suppliers shows different melt temperature ranging from 260 – 290°C .The recommended typical injection moulding cylinder temperature also differ between suppliers.
An interesting feature of PET is that according to the moulding conditions two quite dissimilar products one amorphous, the other transparent, may be obtained, this beings a consequence of having a Tg of about 80°C.
Because of the low melt viscosity injection moulding screw for PET should be fitted with back flow valves and the barrel nozzles should have shut-off-valves.
CORPORATE TRAINING AND PLANNING

33. CORPORATE TRAINING AND PLANNING
Surface Finishing of PET
The high chemical resistance of the polyalkylene terephthalates necessitates the use of special purpose lacquers to ensure good adhesion.
The same applies to hot embossing (temperature range of the die °C).
PET can be polished easily. Metallization can be only be carried out by high vacuum deposition.
Where high gloss surfaces are required on filled and reinforced product, an intermediate lacquer must be used.
CORPORATE TRAINING AND PLANNING

34. CORPORATE TRAINING AND PLANNING
Machineability of PET
Cutting
Cutting can be possible in PET with suitable equipments in a specified speed.
Joining
Welding
Moldings and semi-finished products can be welded and bonded. Unreinforced moldings can be joined by hot gas and heated tool welding. With increasing glass fiber and the flame retardant content, the welded joints decrease in strength. Friction and ultrasonic welding are efficient joining methods.
The conditions for heated tool welding are
Heated tool temperature °C
Contact pressure at start of heating bar
Contact pressure at start of welding bar
Heating up time (according to wall thickness) - 10 to 30 s
CORPORATE TRAINING AND PLANNING

35. CORPORATE TRAINING AND PLANNING
Applications of PET
Appliances
Automotive
Electrical/Electronics
Films
Furniture
Packaging
Miscellaneous
CORPORATE TRAINING AND PLANNING

36. CORPORATE TRAINING AND PLANNING
Applications of PET
Appliances :
Oven and appliance handles, coil forms for microwave oven transformers, small appliance structural framers, panels, chassis and housing and instrument covers.
CORPORATE TRAINING AND PLANNING

37. CORPORATE TRAINING AND PLANNING
Applications of PET
Automotive:
Structural parts such as luggage racks and grills, fuctional housing such as windshield, wiper motor housing , fuel filters, blade supports and bells, sensor, lamp sockets, relays, switches and solenoids
Grill opening retainer
Door module
CORPORATE TRAINING AND PLANNING

38. CORPORATE TRAINING AND PLANNING
Applications of PET
Electrical/Electronics:
Lamps sockets , coil forms for audio/video transformers, terminal blocks, electrical. Electronic connectors and thrust washers.
Electricals Connectors
CORPORATE TRAINING AND PLANNING

39. CORPORATE TRAINING AND PLANNING
Applications of PET
Films:
X-ray films, photographic films, magnetic tapes and printing sheets.
Food packaging
CORPORATE TRAINING AND PLANNING

40. CORPORATE TRAINING AND PLANNING
Applications of PET
Furniture:
Pedestal bases, sent pans, chair arms and castes.
CORPORATE TRAINING AND PLANNING

41. CORPORATE TRAINING AND PLANNING
Applications of PET
Packaging :
Carbonated soft drink containers, distilled spirits, toiletries, food products, mustard, pickle foods, peanut butter, spices, edible oil cocktail mixer and syrups.
Containers
CORPORATE TRAINING AND PLANNING

42. CORPORATE TRAINING AND PLANNING
Applications of PET
Miscellaneous:
General purpose pumps housing , mirror housings three dimensional circuit boards and structural components in office automation equipment, computer housing and structural components, containers, trays, blisters and drinking cups.
CORPORATE TRAINING AND PLANNING

43. CORPORATE TRAINING AND PLANNING
Applications of PET
Automobile engine cover
Heat shield
Gear box
Door washers
CORPORATE TRAINING AND PLANNING

44. CORPORATE TRAINING AND PLANNING
Blends of PET
PET/PC
Partially miscible blends (miscibility is controlled by the level of transesterification) with co-continuous morphology show improved processability, chemical resistance, crystallinity, elongation, low temperature impact and tensile strength.
Blends also show decreased shrinkage and high heat deflection temperature.
These blends are especially interesting for reinforced products because the warpage is significantly decreased.
CORPORATE TRAINING AND PLANNING

45. CORPORATE TRAINING AND PLANNING
Blends of PET
PET/Elastomers
These blends are formulated for extrusion, injection, compression, blow and transfer molding.
The blends contain up to 35 wt. of glass fiber.
They show good processability rigidity impact and tensile strength as well as excellent weatherability.
CORPORATE TRAINING AND PLANNING

46. List of Manufacturers/Suppliers of PET
CORPORATE TRAINING AND PLANNING
CORPORATE TRAINING AND PLANNING