Materials

PET

Mr. Wyeth, the inventor of the PET bottle, would not have believed all the possibilities his new PET bottle would bring to the packaging world. So much more than Soda Pop is put into these plastic bottles today. Some products and applications have more demanding requirements for their packaging. Oxygen permeation, the rate at which oxygen molecules migrate through the PET wall and Thermal Deflection, where heat softens the plastic material causing it to deform or flex inwards, are two typical problems concerning PET bottles.

To overcome these packaging challenges a new category of PET has been introduced called High performance PET.

BARRIER

Tomato-based products, some juices, beer and other foods are highly sensitive to oxygen. Products can change color, smell and even spoil with prolonged exposure to Oxygen. Enhancing the PET wall with barrier technologies reduces O₂ ingression and extends shelf life. Three main barrier technologies have been developed to reduce the O₂ permeation; Co-injection, Coatings and Oxygen scavengers, increase shelf life and enable conversion from heavy, breakable glass containers to lightweight and versatile PET.

Co-Injection

Layers of materials such as polyethylene-vinyl alcohol copolymers (EVOH) are injected between two layers of PET. This provides an additional barrier to Oxygen permeation. The final bottle may have 3, 5 or 7 layers, starting and ending with PET. The core material between the PET layers can range from 2 to 50% of the total weight of the bottle.

PROS	CONS
Internal barrier have no food contact	Not easily recycled.
Variable material types can be used	Material distribution issues
An original process and is well proven	Delimitation
	High equipment costs, requires a special injection machine and injection tooling and requires high unit volume.

Internal Coatings

One of two machines in the USA, Captive recently introduced a new system called Actis coating at our Atlanta GA facility. After a bottle has been manufactured, the bottle is then coated with a passive barrier of Carbon, which is chemically bonded to the internal walls. This process significantly reduces permeation rates for many substances and costs less than traditional methods listed above.

PROS	CONS
Excellent barrier for O₂, CO₂	Currently size limited: Max finish 43 mm and Max diameter is 2.993”
Can adjust coating amount for varied requirements	Bottle has a light tint
Cost effective	It is a Secondary operation
	Change parts required

Oxygen Scavangers

Oxygen scavengers are additives directly introduced to the PET resin during the injection process. O₂ scavengers absorb Oxygen from the product, bottle wall and the environment.

PROS	CONS
No additional equipment	Limited empty bottle shelf life
Absorbs Oxygen from the product and headspace	Requires good inventory control
Uses existing tooling Required less unit volume	May have minor haze look

THERMAL DEFLECTION

Some food and beverage products are filled at elevated temperatures to kill germs and or improve line fill speed efficiencies. At fill temperatures above 140°F (60°C) , some PET containers can soften. The bottle creates an internal vacuum as hot or warm fill products cool causing the bottle to distort. This is called Thermal Deflection.

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TERMINOLOGY	PROCESSING TEMPERATURE RANGE*	PET CONTAINER REQUIREMENTS
Cold FIll	70 to 90°F 21 to 32°C	• Mono Layer PET • Injection Stretch blow molding • Standard resin
Warm Fill	90 to 150°F 32 to 65°C	• Container design • Wall thickness • Pressure base • LN₂ dosing
Hot Fill	150 to 205°F 65 to 95°C	• Container design • Heat set technology • High performance resin • Crystallized bottle • Special perform design

*temperature can vary based on package design.

Warm Fill Technology

Liquid Nitrogen dosing and special bottle designs are ways to combat thermal deflection at warm fill temperatures.

LN₂ Dosing

Pressure base

For some warm fill applications up to 150°F (65°C), Liquid Nitrogen dosing can solve the thermal deflection problem. A drop of LN₂ is injected into the bottle just before it is sealed. When LN₂ atmosphere is exposed to oxygen it expands on average 18 times its original volume and adds positive pressure inside the container eliminating paneling.

The warm fill LN₂ advantage

Used for niche conversion markets (glass)

Products filled between 90 - 140°F (32 to 60°C )

Requires pressure base design

Little to no cost increase

Minimum vacuum panels

More design freedom than heat set bottles
- Improved top load and stacking capability
- Ability to lightweight

Graphic – LN₂ machine – need to get. Reynolds machine.

LN₂ Container Design

Using LN₂ dosing provides design freedom for your filling applications. Now your products can be warm-filled in attractive and flexible PET containers at up to 150 degrees F (65°C) without the need for extensive vacuum panels and the up-charge for heat-setting containers. However proper heat deflection, pressure base and understanding soft spots are still important design considerations. insert image

Hot Fill Technology

To successfully fill a bottle hot, it is important to have a heat-set bottle to handle the high temperatures. The heat set manufacturing process requires special machines and molds to strengthen and crystalize PET to withstand high temperatures.

Hot molds

A temperature-controlled oil circuit is used to increase a mold’s temperature between 257 and 266 °F .

Air-cooling system

A Stretch rod blows continuously exchanged air during the blowing process. This promotes faster cooling inside the bottle to facilitate the extraction of the bottle. **image insert**

Cooling the mold

High Performance Resin

For applications that are filled above 155°F, Captive uses a resin with specific copolymers to slow crystallization process and improve elasticity.

Container Design

Container design plays a major role in preventing thermal deflection. Utilize a combination of the following processes to overcome this challenge:

Develop a specific preform to create as little stress as possible during the blowing process.
Panels, ribs, and windows incorporated into the body of the container to add structural stability.
Container bases are designed to flex and pull into the container body as the product cools and creates the vacuum
The finish needs is crystallized