PET Resin and Preform knowledge. by Opara Emmanuel

PET Resin and Preform knowledge. by Opara Emmanuel Contact information, map and directions, contact form, opening hours, services, ratings, photos, videos and announcements from PET Resin and Preform knowledge. by Opara Emmanuel, Industrial Company, Port Harcourt.

Chemist|| QAQC Analyst|| PET Resin & Preform Quality specialist|| FSSC certified internal Auditor|| Proficient in the use of Profle Projector, Sample Prewatcher for Preform analysis.

Is all about Quality & A-Z of Preform quality
15/03/2026

Is all about Quality & A-Z of Preform quality

25/02/2026

Production and Importance of Preforms Over Glass Bottles

1. What is a Preform?
A preform is a small, test-tube–shaped plastic piece made from PET (Polyethylene Terephthalate). It is later heated and blown into the final bottle shape using stretch blow molding. Preforms are commonly used for water, soft drinks, juices, and edible oils.

2. Production Process of PET Preforms
Step 1: Raw Material Preparation
PET resin pellets are dried to remove moisture (very important to prevent defects).

Step 2: Injection Molding

The dried PET resin is melted in an injection molding machine.
The molten plastic is injected into a preform mold.
The mold forms the neck finish, threads, and body of the preform.

Step 3: Cooling and Ejection

The preform is cooled inside the mold.
It is ejected and ready for storage or transport.
Step 4: Stretch Blow Molding (Bottle Production)

Preforms are reheated.
They are stretched and blown into bottle molds using high-pressure air.
Final bottle shape is formed.
3. Importance of Preforms Over Glass Bottles
1️⃣ Lightweight
PET bottles are significantly lighter than glass.
Reduces transportation cost and fuel consumption.
2️⃣ Lower Breakage Risk
Plastic does not shatter like glass.
Safer during handling and transportation.
3️⃣ Cost-Effective Production
Preforms are mass-produced efficiently.
Lower manufacturing and logistics costs compared to glass.
4️⃣ Storage and Transport Efficiency
Preforms occupy less space before blowing.
Bottle production can happen close to the filling plant.
5️⃣ Design Flexibility
Easy to produce different bottle shapes and sizes.
Suitable for branding and customization.
6️⃣ Energy Efficiency
Producing PET bottles generally consumes less energy than glass bottle production (which requires very high furnace temperatures).
7️⃣ Recyclability
PET is recyclable and widely collected.
Supports circular economy initiatives.
4. Limitations of Glass (Compared to PET Preforms)
Factor
PET Preform Bottle
Glass Bottle
Weight
Very light
Heavy
Breakage
Does not shatter
Easily breaks
Transport cost
Low
High
Production energy
Moderate
Very high
Safety
High
Risk of injury
5. Conclusion
PET preforms play a critical role in modern beverage and liquid packaging. They offer:
Lower production and transport costs
Better safety
Reduced breakage
Flexible manufacturing
Efficient large-scale supply
This is why many beverage and water companies prefer PET preforms over traditional glass bottles.

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24/08/2024

• CHARACTERIZATION OF PET

How is PET characterized?
PET is characterized by the following properties:
• Intrinsic Viscosity (I.V.)
• Definition: A measure of the capability of a polymer in solution to enhance the viscosity of the solution. Intrinsic viscosity-increases the increasing polymer molecular weight. The viscosity behavior of macromolecular substances in solution is one of the most frequently used approaches for characterization. The intrinsic viscosity number is defined as the limiting value of the specific viscosity/concentration ratio at zero concentration. It thus becomes necessary to find the viscosity at different concentrations and then extrapolate to zero concentration. The variation of the viscosity number with concentration depends on the type of molecule as well as the solvent. In general, the intrinsic viscosity of linear macromolecular substances is related to the molecular weight or degree of polymerization. With linear macromolecules, viscosity number measurements can provide a method for the rapid determination of molecular weight when the relationship between viscosity and molecular weight has been established. Intrinsic viscosity is calculated by determining ηsp/C and extrapolating to infinite dilution.
•
• where:
c = concentration of polymer in grams per 100 milliliters of solution
•
I.V. is a measure of average length of molecular chains or molecular weight. It determines the viscosity of molten polymer and mechanical strength of the bottle. Although PET resins with different I.V. (say 0.70 to 0.90) are being used for bottles, the most popular I.V. is 0.8 dl/g.
• Acetaldehyde (AA) Content
AA gets generated during polycondensation process as a byproduct of thermal degradation and gets trapped in PET when molten polymer is cooled. Since it has low boiling point (@ 21oC) and sweet fruity odor, it can influence the taste of packed products if present in excessive amounts. The current production technologies ensure that AA content is less than 1 ppm in PET bottle grade resins.
There is a possibility of generating AA during processing of PET into pre-forms/bottles due to the presence of vinyl ester end groups in the polymer chain, which degrade at molding temperature. In order to minimize generation of this potential AA, the vinyl ester end groups should be kept to minimum in the polymer.

• Colour
The colour should be as close to neutral as possible. This colour is generally measured on a L, a, b scale, 'L' representing white and black colors, 'a' representing red and green colors and 'b' representing yellow and blue colors. The L, a, b values are controlled in such a way that the bottles will have as close to neutral colour as possible.

• Crystalline
Crystalline should be above 50% so that the chips do not soften and form agglomerates during drying process prior to molding. The degree of crystalline is directly correlated to density of the polymer and is normally derived from density value. Crystalline Melting Point (Tm) For PET homopolymers, Tm is around 255oC whereas copolymers exhibit a value around 245oC.

• Glass-transition-temperature (Tg)
This is the temperature at which the amorphous polymer softens and becomes rubbery. Amorphous PET can be stretched mechanically at temperatures just above Tg as in the case of stretch blow moulded PET bottle. Tg of PET lies around 75oC.

• DEG Content
DEG content is maintained around 2% for homopolymer and around 1% for copolymers. It influences melting point, crystallisation rate and melt viscosity.

• Carboxyl (COOH) End groups
This should be kept below 30 because higher amounts can catalyse hydrolytic degradation of polymer at high temperatures in the presence of moisture.

• Polymer dust / fines
This should be kept to minimum so that the bottles produced are free from fish eyes / gels.

• At what temperature Intrinsic viscosity calculate determine?
Intrinsic viscosity determine at constant temperature at 25 deg C

• Which solvent commonly is used to dissolve the PET polymer
Phenol AR grade & O- Dichlorobenzene (60:40 by weight mixture)

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Your view vs The Chemist view
22/06/2024

Your view vs The Chemist view

Polymerisation Reaction
23/05/2024

Polymerisation Reaction

• How is PET obtained? PET is industrially obtained by two chemical routes:Trans esterification of dimethyl terephthalat...
23/05/2024

• How is PET obtained?
PET is industrially obtained by two chemical routes:
Trans esterification of dimethyl terephthalate (DMT) with ethylene glycol: this is an older route, used because of the difficulty in the obtainment of the acid with enough purity for the application. This route is still used by some companies.
Direct esterification of the purified terephthalic acid (PTA) with ethylene glycol (EG): a more modern route, preferred by most manufacturers of the PET resin, maybe due to the better quality of the resin obtained.
The substances react at high temperature and high pressure to obtain the amorphous PET. The resin is then crystallized and polymerized to increase its molecular weight and viscosity.
The terephthalic acid, in its turn, is obtained by the oxidization of p-xylene, while ethylene glycol (MEG) is synthesized from ethylene, and both are products of the petrochemical industry, as represented in the figure.
Oil
Refinery
Naphtha
Paraxylene Ethylene
DMT PTA MEG
Monomers
PET (IV = 0.63)
PET (bottle grade)
• How is PET manufactured?
The manufacturing process of PET consists of two separate steps called melt-phase Polycondensation and solid-state Polymerisation (SSP).

In Polycondensation, PET chips of lower Intrinsic Viscosity (IV), which are amorphous/transparent, are produced. In the second step i.e. SSP; these amorphous chips are upgraded into crystalline chips of higher IV and all the impurities are removed simultaneously. These upgraded chips are suitable for producing bottles, sheet strapping and monofilaments.

Polycondensation is carried out in two stages i.e. Esterification and Polymerisation. In Esterification, PTA and MEG react to form monomer with Bishydroxyethylene terephthalate (BHET). In the subsequent Polymerisation step, the monomer is polymerised into polymer (PET). These two steps are demonstrated in the following reaction:

Esterification Reaction

05/05/2024

Preform Defect : OVALITY.
A major Preform defect that blowers frequently encounter is neck(Finish) ovality.

Neck ovality occurs when the circular finish of PET preform becomes slightly or moderately oval due to high temperature, compressive forces, and/or humidity. If the ovalization is significant enough, the round blow nozzle on the blow molding machine cannot fit into the internal diameter of the finish.

Neck ovality most often is a post production defect caused by exposure to high temperature, compressive forces and high humidity.

A major problem PET Preform blowers face is Preform gate bursting. Preform gate bursting is one defect that is mainly mi...
26/04/2024

A major problem PET Preform blowers face is Preform gate bursting. Preform gate bursting is one defect that is mainly misunderstood, many operators attribute this bursting to less bottom thickness; though this could be the culprit, experience has shown that this is not always the cause.
The two major causes of Preform gate bursting are.
1. Gate Crystallinity
2. Air bubbles

Gate Crystallinity

Gate Crystallinity is a white crystalline formation appearing in the preform gate area.
Commonly found throughout the entire wall cross-section,
in the interior wall section, close to the core cap surface, and as a streak extending from the gate area into the preform body.

This defect occurs because of any or combination of the following factors.
a. Temperature of melt in mold nozzle tip too
cold during the time the melt is not flowing.
b. Temperature of melt in the mold nozzle tip
and/or preform gate area too hot causing a
deep white haze (especially in preforms with
thick wall sections).


In transparent Preforms, Gate crystallinity can easily be detected and corrected during processing, however in opaque Preform, detecting crystallinity is not an easy task.

Air Bubbles
Air bubbles are random bubbles or hollows appearing in the preform side wall/gate area caused
by entrapped air or gas formation.
This defect occurs because of any or combination of the following factors.
(a) Gas or air entrapped in the melt during the plasticizing process due to insufficient melt compression.
(b) Air drawn in due to excessive decompression.
(c) Premature melting of the resin due to
excessive extruder feed zone temperature.

Bubble can easily be seen in transparent Preforms but can be masked in opaque Preform.

18/04/2024

Defects in Preform are numerous and can be a nightmare to blower operators.

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