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8/13/2019 2. PET - PreformManufacturing & Blowing
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PET BOTTLE QUALITY TOOL
Page 1PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
PreformManufacturing
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Page 2PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Packaging Quality Tool
Preform Manufacturing
Guiding
PrinciplesUnderstand
Raw Materials
Process
Supplier
Approval
Concerns 1) Resin morphology- Degree of Crystallinity
2) Hydrolytic Degradation:
- Drying of PET
- Moisture Content
3) Intrinsic Viscosity(IV):
- IV reduction
Preform/PET BottleManufacturing
RawMaterials
1) Starting materials for PET
are Paraxylene & Ethylene
2) Starting materials form two
intermediates (EthyleneGlycol & Terephthalic Acid)
which react to form a
monomer
3) Monomer is polycondensed
to form a long polymer
called Polyethylene
Terephthalate (PET)
Capability to manufacture
PET bottles that
meet PBI specifications
1) Resin Storage
2) PET Resin Drying
3) Injection molding of preforms
4) Preform in plant testing
5) Preform storage & distribution
6) Preform/PET bottle receipt
and inspection
7) Preform storage
8) Preform Pre-heating
9) PET Bottle Blowing
10) PET Bottle Storage
1) Resin to be dried to < 50ppm2) Thermal degradation (heat abuse)
will lead to: a) Reduction in I.V. &
b) Acetaldehyde (AA) generation
3) Maximum drop of 0.02 dl/gr. allowed
4) Preforms must be purchased from
PBI qualified suppliers
5) Preforms should be conditioned
over night prior to blowing
6) PET bottles stored in a dry
environment
Maintain Quality of the
Package after Receipt
at the Beverage Plant
1) PET Bottle receipt, inspection
and storage
2) PET bottle rinsing/washing
3) Bottle filling
4) Filled PET bottle storage
1) Receiving and inspectionCOC/COA ; minimum
incoming inspection
2) Base bursting
QualityAssurance
BeveragePlant
Use Only PET bottles
that Meet PBI
Specifications
1) PET bottles outsidespecifications
2) Stress-cracking
3) CO2 loss
PET bottle specifications
Parameter
Bottle Appearance
Dimensions
Bottle HeightMajor Diameters
Bottle Weight
Fill Height Capacity
Perpendicularity
Wall Thickness
Material Distribution
Internal Pressure
PBI PET bottle
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Page 3PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
(2) Understand the suppliers capability to
consistently supply PET bottles that meet
PBI specifications
Guiding Principle
Preform Manufacturing
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Page 4PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Preform Manufacturing
Agenda
Preform Manufacturing Overview
Unit operations
Acetaldehyde (AA) Preform in-plant testing
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Page 5PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Typical Description of a Preform
Neck Support
Ring
Gate
Body
Neck Finish
Locking Ring Neck Finish does not
change after injectionmolding process
Preform body is stretched inblowing process
Gate area does not changeafter injection molding
process
Preform Manufacturing
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Page 6PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Bottle Finish Dimension Letters
The standard neck finishes are:- BPF: British Plastic Federation
- PCO: Plastic Closure Only
www.threadspecs.com
Preform Manufacturing
Band
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Page 7PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
How are Preforms Made and Their Critical Parameters
PET Resin Injection Molding
of Preforms
Injection Molding
of Preforms PreformPreform
Preform
Handling &
Storage
Preform
Handling &
Storage
PET Resin
Receipt
&
Storage
PET Resin
Receipt
&
Storage
Moisture: 14ppm
Preform Manufacturing
I.V.: 0.80-0.84+/-0.02
dl/gr.
Acetaldehyde:< 1 ppm
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Page 8PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Receipt and Storage of PET Resin
Process: PET resins are shipped in corrugated boxes, bulk tank trucks
and bulk rail cars to the preform manufacturing facility
Resins are stored in silos with a capacity of 75 tonnes(approx.)
Silos are typically made of aluminum and/or stainless steel
Preform Manufacturing
Dried at -40C dewpoint and 180C (356F)
PET ResinPET Resin Injection Molding
of Preforms
Injection Molding
of PreformsPreform
PreformPreform
Handling &
Storage
Preform
Handling &
Storage
PET Resin
Receipt& Storage
PET Resin
Receipt& Storage
PET ResinDrying
PET Resin
Drying
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Page 9PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Receipt and Storage of PET Resin
Concern:
Bulk tankers should be cleaned prior to loading andtransportation
Good manufacturing practices should be followed in thetransfer of resin to the silos. Avoid soil contamination, i.e.stones being pick up in the transfer process
Stainless steel flexing should be used in the resin transfer
process. Avoid using rubber hosing as it wears quickly
Preform Manufacturing
Dried at -40C dewpoint and 180C (356F)
PET ResinPET Resin Injection Molding
of Preforms
Injection Molding
of PreformsPreform
PreformPreform
Handling &
Storage
Preform
Handling &
Storage
PET Resin
Receipt& Storage
PET Resin
Receipt& Storage
PET ResinDrying
PET Resin
Drying
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Page 10PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Process:
Drying involves placing the PET polymer in a drier of between
0.5 and 4 metric tons capacity and blowing hot dry air throughit
It will typically take between 5 to 7 hours in the drier for thePET polymer to obtain the correct moisture level (< 50ppm) forprocessing
Carefully controlled drying is an essential requirement in orderto remove the moisture from the granules
Faulty drying cannot be reversed later on in the conversionprocess (PET resin to Preform)
The most common type of drying method used is the Heated
Air with Desiccant Dehumidifying process
How is Drying of PET Resin Accomplished?
Preform Manufacturing
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Page 11PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
How is Drying of PET Resin Accomplished?
Concern:
The presence of a high moisture level in the resin will result in:
- Reduction of the Intrinsic Viscosity (I.V.) of the PETmaterial which will result in poor material distribution within
the PET bottle (accelerated CO2 loss with the finished
beverage).
Dried at -40C dewpoint and 180C (356F)
PET ResinPET Resin Injection Moldingof Preforms
Injection Molding
of Preforms Preform
PreformPreform
Handling &Storage
Preform
Handling &
Storage
PET Resin
Receipt
& Storage
PET Resin
Receipt& Storage
PET ResinDrying
PET Resin
Drying
Preform Manufacturing
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Page 12PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Injection Molding of Preforms
Process:
PET resin is melted, compressed in an extruder and theninjected into water cooled cavities where it quickly solidifies toform a preform
Preforms are then stored and later transported to a PETblowing operation for stretch-blowing into PET bottles
Preform Manufacturing
Dried at -40C dewpoint and 180C (356F)
PET ResinPET Resin Injection Moldingof Preforms
Injection Molding
of Preforms Preform
PreformPreform
Handling &Storage
Preform
Handling &
Storage
PET Resin
Receipt
& Storage
PET Resin
Receipt& Storage
PET ResinDrying
PET Resin
Drying
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Page 13PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
PET ResinPET Resin
ScrewScrew
Barrel (~ 290C/554F to 320C/608F)Barrel (~ 290C/554F to 320C/608F)
PreformPreform
Gate sectionGate section
SprueSprue
Injection Molding of Preforms
ExtruderExtruderCavityCavity
Core PinCore Pin
Preform Manufacturing
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Page 14PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Concern:
Minimize resin degradation(thermal) which will result in:a) I.V. reduction (0.02dl/gr. Max. allowed), andb) high acetaldehyde
Preform clarity issues due to poor cooling of the preforms
Injection Molding of PreformsPET ResinPET Resin
ScrewScrew
Barrel (~ 290C/554F to 320C/608F)Barrel (~ 290C/554F to 320C/608F)
PreformPreform
Gate sectionGate section
SprueSprue
CavityCavity
Core PinCore Pin
Preform Manufacturing
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Page 15PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Agenda
Preform Manufacturing
Preform Manufacturing Overview
Unit operations
Acetaldehyde (AA) Preform in-plant testing
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Page 16PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
What is Acetaldehyde (CH3CHO)?
Acetaldehyde (AA):
In its pure state Acetaldehyde (AA) has a sharp fruity sweetapple taint
The rate of formation of AA is dependent on the PET resinformula and drying efficiency
AA is only formed in significant quantities during the preforminjection molding process
At room temperature (20C/68F), Acetaldehyde is a
colorless vapor which is soluble in water Acetaldehyde (AA) is a product of thermochemical (high
temperature abuse) degradation
Preform Manufacturing
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Page 17PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Preform Manufacturing
What is Acetaldehyde (CH3CHO)?
Preform AA specification:
Average AA < 10ppm, no one cavity > 14ppm
The presence of a high concentration of AA wouldindicate;
Poor processing conditions which could also result in a largedrop in the resin I.V. value (when resin is converted to apreform)
In the injection molding equipment certain cavities will
consistently produce high AA values in preforms These cavities are called High (Hot) or critical cavities
In performing AA analysis, one of these criticalcavities should be sampled once a week per mold to
determine AA concentration
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Page 18PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Haze Defect type: Hazy preforms
Description: Appears with varyingamounts ofcrystallinity in the
preform sidewallCause: Resin not dried
properly prior to
processingConcern: Stress cracking of
the filled PET bottle
Concerns From Preform Production
Preform Manufacturing
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Page 19PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Concerns From Preform Production
Defect type: Short Shots
Description: Neck finish notcompleted
Cause: In-sufficient polymerwas packed duringthe injection fill time
Concern: Poor bottle/closureseal - High CO2 loss
Short Shots
Preform Manufacturing
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Page 20PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Agenda
Preform Manufacturing
Preform Manufacturing Overview
Unit operations
Acetaldehyde (AA) Preform in-plant testing
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Page 21PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
PET ResinInjection Molding
of Preforms
Preform
Preform
Handling &
Storage
PET Resin
Receipt
& Storage
PET Resin
Drying
Typical In-Plant Testing Regime at the Preform Supplier
Test: Frequency: Equipment:
Preform weight A full round/day/mold Weighing Balance
Preform wall thickness 5 Preforms/day/mold Magna-Mike, Panametrics
Finish dimension During mold change over Callipers, Profile projector
Visual inspection A full round/shift /mold Magnifying Glass
I.V. Critical cavity/week/mold as a minimum As per ASTM D-4603
Acetaldehyde (AA) Critical cavity/week/mold as a minimum Gas Chromatograph
Preform Manufacturing
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PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Preform Manufacturing
Preform Handling and Storage
Normally packed in polyethylene plastic bags
which are closed to the surrounding environment Polyethylene liner is used to prevent dust and dirt
contamination
Preforms should not be stored in direct sunlight Stored in a covered/closed warehouse with ideal
temperatures of between 5C/41F to 35C/ 95F
at Relative Humidity < 60% 12 months maximum for storage of preforms is
recommended (from date of preform manufacture)
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Page 23PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Preform Manufacturing
Preform Handling and Storage
Information that should accompany theshipment:
a) Name of Supplier/City/Countryb) Lot Identification:
c) Certificate of Compliance/Analysis (COC\COA)
Lot code
Neck finish type Shift Production date Color
Resin type
Preform quantity/boxes Preform weight Shipment date Injection machine/line
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Page 24PQT: PET Preform Manufacturing FINAL: SEPTEMBER 2002
Preform Manufacturing
What are the Key Take-Aways From This Module?
Under controlled drying and molding conditions theI.V. loss for dried PET resin conversion to a preform
shall be less than 0.02dl/gr. Preforms can be stored for up to 12 months in a
closed/covered environment warehouse with ideal
temperatures of between 5C/41F to 35C/95F atRelative Humidity < 60%
The rate of formation of AA is dependent on the PETresin formula and is formed only in significant
quantities during the preform injection moldingprocess
Preform Acetaldehyde specification:
Average AA < 10ppm, no one cavity > 14ppm
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PET BOTTLE QUALITY TOOL
Page 1PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
PET BottleBlowing
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Page 2PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Packaging Quality Tool
PET Bottle Blowing
Guiding
PrinciplesUnderstand
Raw Materials
Process
Supplier
Approval
Concerns1) Resin morphology
- Degree of Crystallinity
2) Hydrolytic Degradation:
- Drying of PET
- Moisture Content
3) Intrinsic Viscosity(IV):
- IV reduction
Preform/PET BottleManufacturing
RawMaterials
1) Starting materials for PET
are Paraxylene & Ethylene
2) Starting materials form two
intermediates (EthyleneGlycol & Terephthalic Acid)
which react to form a
monomer
3) Monomer is polycondensed
to form a long polymer
called Polyethylene
Terephthalate (PET)
Capability to manufacture
PET bottles that
meet PBI specifications
1) Resin Storage
2) PET Resin Drying
3) Injection molding of preforms
4) Preform in plant testing
5) Preform storage & distribution6) Preform/PET bottle receipt
and inspection
7) Preform storage
8) Preform Pre-heating
9) PET Bottle Blowing
10) PET Bottle Storage
1) Resin to be dried to < 50ppm
2) Thermal degradation (heat abuse)
will lead to: a) Reduction in I.V. &
b) Acetaldehyde (AA) generation
3) Maximum drop of 0.02 dl/gr. allowed
4) Preforms must be purchased from
PBI qualified suppliers
5) Preforms should be conditioned
over night prior to blowing
6) PET bottles stored in a dry
environment
Maintain Quality of the
Package after Receipt
at the Beverage Plant
1) PET Bottle receipt, inspection
and storage
2) PET bottle rinsing/washing
3) Bottle filling
4) Filled PET bottle storage
1) Receiving and inspection
COC/COA ; minimum
incoming inspection
2) Base bursting
QualityAssurance
BeveragePlant
Use Only PET bottles
that Meet PBI
Specifications
1) PET bottles outside
specifications
2) Stress-cracking
3) CO2 loss
PET bottle specifications
Parameter
Bottle Appearance
Dimensions
Bottle HeightMajor Diameters
Bottle Weight
Fill Height Capacity
Perpendicularity
Wall Thickness
Material Distribution
Internal Pressure
PBI PET bottle
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Page 3PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
(2) Understand the suppliers capability to
consistently supply PET bottles that meet
PBI specifications
Guiding Principle
PET Bottle Blowing
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Page 4PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Agenda
PET Bottle Blowing
Best Practice recommendationsfor incoming preforms
Operational Practices Preform receipt and inspection
Preform storage
PET bottle stretch-blowmolding
PET bottle storage
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Page 5PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Best Practice Recommendations for Preforms
PET Bottle Blowing
Preforms are purchased only from approved
suppliers Bottle blower is responsible for approving the
preform supplier.
Preforms must meet PBI Preform specifications COC/COA requirements are met on new preforms
either:
By supplier providing COC/COA with every lot, or
By COA testing being performed at the PET blowingfacility for each lot of preforms delivered
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Page 6PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
PET Bottle Process Overview
PREFORM
RECEIVING/
INSPECTION
PET BOTTLE
BLOWING
EMPTY PET
STORAGE
Process: Sampling
COC/COA
Incoming Tests
Preform conditioning
Preheating oven
Stretch-blowing
Concerns: Acetaldehyde
Intrinsic Viscosity
Visual Defects
Mixing preforms with
different I.V.s
Stretch rod and pre-
blow timing
PREFORM
STORAGE
Preform storage
Storage time/temp
Relative humidity
FIFO
BEVERAGE PLANT
Temperature
Humidity
Odor
FIFO
Empty PET
bottle storage
PET Bottle Blowing
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Page 7PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Obtain bill of lading
Verify truck cleanliness Verify the certificate of compliance/analysis
Check preform pallet labels for correct details
Receiving/Inspection
PREFORMS
PET Bottle Blowing
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Page 8PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
COC (Certificate of Compliance)
Written documentation showing contract terms Preform specification requirements (include preform
drawing reference number & resin type)
COA (Certificate of Analysis) Data for critical parameters:
Appearance
Dimensions (include neck finish) Intrinsic Viscosity of a) PET resin and b) preform
Acetaldehyde
Weight
COC & COA Requirements
PET Bottle Blowing
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Page 9PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Certificate of Compliance /Analysis
Provided by preform
supplier Does not replace
inspection criteria forthe PET bottle facility
Analyses must be from
that preform lot
Certificate of
Compliance &Analysis
PET Bottle Blowing
Certificate of Compliance/Analysis for Preforms
Supplier/Distributor ___________________ Bill of Lading No. ___________________ Shipped To (PET Blowing Plant) ___________________Date Delivered: ___________________ Batch No.: ___________________ Resin Type: ___________________
Preform Drawing No.: ___________________
This is to certify that the preforms contained in this shipment meets andconforms to all requirements called for in PepsiCo Beverage Internationalsspecifications dated_____.
Furthermore, the preforms in the specified delivery have been analyzed and the datarecorded for the specific standards shown below.
Test Items Specification Test Result
Appearance Free of visual defect
Weight < 30 grs: +/- 0.3 grs> 30 grs: +/-0.4 grs
Neck FinishDimension
As shown in PBI approved drawing
a) Resin IntrinsicViscosity
b) Preform IntrinsicViscosity
0.80-0.84 +/- 0.02 dl/grMaximum IV drop of 0.02 dl/gr from the
initial resin I (as per ASTM#D4603)
Acetaldehyde Avg. < 10.0 ppm with no individual cavity inexcess of 14.
* Only official PepsiCo Beverages International test methods must be used.
Certified by:
on(Signature) (Date)
______________________________ of_______________________________
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Page 10PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
T E S T I N G R E Q U I R E D
COC/COA
Incoming Preform Receiving Process
NO
COC/COA
Appearance
Weight
Appearance
Weight
Dimensions
Intrinsic Viscosity of
Preform
Acetaldehyde (AA)
PET Bottle Blowing
3 SAMPLES/LOT
10 SAMPLES/LOT
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Page 11PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Sample randomly 10 preforms per truck or trailer
delivery. Samples should be taken from the front,
end, and middle of truck.
Evaluate these samples for:
1. Appearance2. Dimensions (include neck finish)
3. Weight
4. Intrinsic viscosity5. Acetaldehyde (AA)
Recommended Sampling Plan with No COC/COA?
If results are out
of specification,then reject this lot
of incoming
preforms
A Lot is defined as a truckload (trailer) of preforms
PET Bottle Blowing
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Page 12PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Process Overview
PREFORM
RECEIVING/
INSPECTION
PET BOTTLE
BLOWING
BEVERAGE
PLANT
Process: Sampling
COC/COA
Incoming Tests
Preform conditioning
Preheating oven
Stretch-blowing
Concerns: Acetaldehyde
Intrinsic Viscosity
Visual Defects
PREFORM
STORAGE
Preform storage
Storage time/temp
Relative humidity
Mixing preforms with
different I.V.s
Stretch rod and pre-
blow timing
EMPTY PET
STORAGE
Temperature
Humidity
Odor
FIFO
Empty PET
bottle storage
PET Bottle Blowing
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Page 13PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Storage of Preforms at the Beverage Plant
PET Bottle Blowing
A First In, First Out principle should be applied in thecase of preform inventory
Preforms age during storage 12 months maximum
The degree of aging is dependent upon storagetemperature and relative humidity. Acceptable storage
conditions are: Storage temperature 5C/41F to 35C/95F
Relative Humidity < 60%
As the age of the preform changes so too might the pre-heating oven set up conditions prior to PET bottle blowing
Transit packaging containing preforms should not bestacked too high as preform necks can be damaged (oval)
UPDATED: MARCH 2003
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Page 14PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Process Overview
PREFORM
RECEIVING/
INSPECTION
PET BOTTLE
BLOWING
Process: Sampling
COC/COA
Incoming Tests
Preform conditioning
Preheating oven
Stretchblowing
Concerns: Acetaldehyde
Intrinsic Viscosity
Visual Defects
Mixing preforms with
different I.V.s
Stretch rod and pre-
blow timing
PREFORM
STORAGE
Preform storage
Storage time/temp
Relative humidity
BEVERAGE
PLANTEMPTY PET
STORAGE
Temperature
Humidity
Odor pickup
Empty PET
bottle storage
PET Bottle Blowing
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Page 15PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
PET Stretch-Blowing Process
PreformPreform Stretch RodStretch Rod MoldMold
Preform is heated(~ 105C/221F)
Preform is blown into a PET bottle(~ 65C/149F)
PET bottle blowing occurs in four steps:
1) Preform conditioning, 2) Preform heating, 3) Mechanical axial stretching &
4) Radial stretching using compressed air
PET Bottle Blowing
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Page 16PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Step 1: Preform Conditioning
PET Bottle Blowing
Process:
Preforms are stored in a warm dry area (Blowing hall preferably) for aminimum of 24 hours prior to pre-heating and blowing.
This conditioning allows for the preforms to be of a more uniformtemperature profile when presented to the pre-heating oven
Concern:
Mixing preforms from different lots, different storage conditions (i.e.,
temperature), different resins, and preform age can result in thefollowing issues occurring with the blown PET bottle;
a) Crystallinity (Preforms too hot or cold)
PET bottle opaque in color
b) Pearlescence (Preforms too cold) Hazy effect throughout bottle
c) Poor material distribution
Cold or unevenly heated preforms
Difficult to adjust the blowing machine
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Page 17PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Step 2: Preform Heating
Process:
Pre-heating oven consists of 8 -10 heatingzones (infra-red lamps). Heat intensity inheating zones is adjustable to facilitatematerial distribution
Preform neck is protected from heat by
cooling shield
Concern:
Poor preform heating results in:1. Poor material distribution in PET bottle
2. Poor wall thickness in PET bottle
3. Pearlescence on PET bottle sidewall
Infra RedInfra Red
lampslamps
Neck shieldsNeck shields
PET Bottle Blowing
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Page 18PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Process:
Heated Preforms (110C/230F approx.) aretransferred to the blow-molding equipment.
Preforms are placed between two blow moldsection halves. Mold temperatures of 65-95C(149-203F) are typical.
Mold sections are closed and clamped.
Concern:
If mold temperatures are too high then excessive
shrinkage will occur, resulting in low fill heightcapacity issues in the PET bottle.
Any preforms that drop out of the transfer unit(between heating oven and stretch-blowingequipment) must be scrapped.
Step 3: Mechanical Axial Stretching
Preform(Heated)
Mold Closes
Around Preform
Mold
PET Bottle Blowing
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Page 19PQT: PET Bottle Blowing Manufacturing FINAL: SEPTEMBER 2002
Process:
Stretch rod is introduced via the preform neck which
longitudinally stretches the preform to the bottom ofthe mold
Axial molecular orientation takes place during thisstretching process
Air is then introduced into the bottle to distribute thematerial radially (around circumference)
Concern:
Rate that the preform is stretched is critical to thelevel of orientation in the PET bottle
Timing of the stretch rod and air blow, are critical informing a good PET bottle (moving material to theright places)
Step 3: Mechanical Axial Stretching
Air starts to
inflate preform
Stretch rod
(Pushespreform
downwards)
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Process:Occurs in 2 Stages:
1) Pre-Blow and 2) Main Blow:
Pre-Blow Typically 9 bar pressure
Radial orientation of molecules takesplace
Timing of pre-blow determines amount ofmaterial in base
Main Blow
Typically 40 Bar Pressure
Follows Pre-Blow
Gives the final definition to the bottleshape
Step 4: Radial Stretching Using Compressed Air
Air Air
Air drives preformsidewalls outwardsto the mold surface
PET Bottle Blowing
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Concerns:
In-correct timing between the stretch rod
initial movement and the pre-blow stage willresult in poor material distribution within thePET bottle. (Material begins to move early inthe blowing process to the PET bottle
shoulder and base areas - Results inaccelerated CO2 loss in filled PET bottles.
Inadequate venting of the air from the mold
can result in flat sidewalls at the parting lines.Defect known as Panelling which leads tofoaming issues at the filler
Step 4: Radial Stretching - Main Concerns
PET Bottle Blowing
Air Air
Air drives preformsidewalls outwards
to the mold surface
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What Happens to the Preform During PET Bottle Blowing?
Stretch Blow molding & Biaxial Orientation:
Preform is biaxially stretched during blow molding (circumferentially & axially)
This biaxial orientation impacts certain physical properties,i.e., Gas permeation through the sidewall is decreased
The degree of biaxial orientation is influenced by how fast the bottle isstretched (Axial direction) and blown circumferentially
PET Bottle Blowing
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Typical Types of Defects Found in Stretch-Blowing
Strangled
Neck:Too much
material in
top shoulder
area of PET
bottle
Defect Type: Visual Aid: Cause: Filled PET issue Remedy:
Pre-blow
too late
Preformsover orunder-heated
Correct
pre-blowtiming
Correct heatshields(reflectors)
Pre-blowtoo fast
Insufficient
blowpressure
Correctpre-blow timing
Adjust airpressure higher
Underblown
Feet:
Base area
of the PETbottle is
not fully
formed
Accelerated
CO2 loss, andPET fillingissues(foaming).
PET bottlestability issues,acceleratedCO
2loss and
potentialstress-crackingproblems
Less fill heightcapacity
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Defect Type: Visual Aid: Cause: Filled PET issue: Remedy:
Typical Types of Defects Found in Stretch-Blowing
Crystallinity:Material
appears as
opaque or
milky white in
appearance
Preforms too hot
(Haze on outside) In-adequate
mold cooling
Pre-blowpressure high
Lower heating
power Check mold
cooling water
Adjust pre-blow pressure
Crystallinity
Off Center
Gate:Gate section is
not centered
correctly
Off Center Gate Pre-blow too fast
before stretchrod centers ongate
Preform slants
Correct pre-blow timing
Lower blowair pressure
Check mold& threadalignment
Potential stress-
cracking issues,and acceleratedCO2 loss
Poor material
distribution,accelerated CO2loss andpotential stress-cracking issues
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Neck Finish Dims.
Stress Cracking
Top Load
Burst Test
Fill HeightCapacity
Sectional Weights
Visual Inspection
Drop Impact Test
Dimensions(Height, Diameters)
One sample/mold/shift (8 hours)
One sample /mold/week
One sample/mold/shift (8 hours)
One sample/mold/4 hours
One sample/mold/shift (8 hours)
One sample/mold/2 hours
One sample/mold/shift (8 hours)
One sample/mold/shift (8 hours)
One sample/mold/shift (8 hours)
Callipers, Micrometer
0.2% NAOH, Stop Watch
Top Loader (e.g. Instron)
AGR Model 073
Weighing Balance, Water DensityTables, Thermometer
Weighing Balance, Cutting Tool
Magnifying Glass
Concrete slab, Temperaturechambers
Callipers, Micrometer, Height Gauge
Test: Frequency: Equipment:
Typical PET Bottle In-Plant Testing Regime
PET Bottle Manufacture - Stretch-blowing
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One Stage vs. Two Stage Process
Two Stage One Stage
PET Bottle Blowing
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Item: Two Stage: One Stage:
Level Of Bi-orientation Higher (Lower Preform Temp) Lower
Material Distribution Optimum (Preform Design) Some issues under neck
stretching
AA Level Low High
Moisture Pick Up During Preform Storage No moisture pick-up
Scrap Rate Low (< 1%) High (2 - 4%)
One Stage vs. Two Stage Process
PET Bottle Blowing
UPDATED: MARCH 2003
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80%
15%
3%
PET Resin
Other
Labour
Scrap
Cost Breakdown of a PET Bottle
Resin prices are a key cost when evaluating economics
PET Bottle Blowing
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Process Overview
PREFORM
RECEIVING/
INSPECTION
PET BOTTLE
BLOWING
Process: Sampling
COC/COA
Incoming Tests
Preform conditioning
Preheating oven
Stretchblowing
Concerns: Acetaldehyde
Intrinsic Viscosity
Visual Defects
Mixing preforms with
different I.V.s
Stretch rod and pre-
blow timing
PREFORM
STORAGE
Preform storage
Storage time/temp
Relative humidity
BEVERAGE
PLANTEMPTY PET
STORAGE
Temperature
Humidity
Odor pickup
Empty PET
bottle storage
PET Bottle Blowing
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Empty PET Bottle Storage
PET Bottle Blowing
First In, First Out principle should be applied in the caseof empty PET bottle inventory
PET bottles should be stored in a dry environment. Ideal
conditions are Storage temperature: 5C/41F to 35C/95F
Relative Humidity: < 60%
Keep PET bottles away from substances that emit strongodors and direct sunlight (PET transportation andwarehousing)
Lot Identification:
Lot code Neck finish type
Date
Shift
Production date
Color
Resin type
PET Bottle Weight
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Empty PET Bottle Storage
PET Bottle Blowing
PET bottles are normally packed into cardboard trayswhich are placed on wooden pallets (up to 8 layers in
height)
These pallets of empty PET bottles are normallystretch-wrapped and stored in the warehouse at no
more than 4 pallets high.
Silo storage is used as an alternative with somebeverage plants.
While no specific age limit exists, bottles more than 6months old may be subject to secondary shrinkage,rendering them unsuitable for use (Fill height issues)
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Key Take-Aways
PET Bottle Blowing
Preforms are purchased only from approved suppliers
COC/COA reduces the need on the PET blowingfacility to perform incoming testing on the preforms
Preforms should be stored for 24 hours in the same
room prior to PET bottle blowing PET bottles should be stored in a dry environmentAcceptable conditions are:
Storage temperature 5C/41F to 35C/95F
Relative Humidity < 60%