The popularity of PET packaging

14 September 2003 (Last Updated September 14th, 2003 18:30)

Why is PET packaging the most widely used plastic packaging material? part of the answer is that its attributes are many and its future opportunities extensive.

Amcor PET Packaging

PET is the most adaptive and widely used plastic packaging material. Its popularity is driven by its well-known attributes, including clarity, shatter resistance, mouldability, recyclability and cost-effectiveness.

In fact, PET is the fastest growing packaging material worldwide. In 2002 some nine million tonnes of PET packaging resin were produced and converted. This is an increase of nearly 10 per cent over the prior year, and double-digit growth rates are predicted for the next five years.

In addition to packaging, PET is also a popular material for fibres used in clothing and carpets. It is so versatile that it can be recycled back into packaging or fibres depending on the demand for material.

Thermal stability

Many beverage manufacturers use a hot-filling process to package their products. Hot filling eliminates viable spoilage organisms in the product and the package. This process requires bottles to be heat-resistant and to withstand elevated temperatures during filling and handling operations. For the last decade PET packaging manufacturers have provided customers with containers that are filled at about 85°C.

In the past, vacuum panels were required to control the collapse of the hot-filled container as it cools. Vacuum panels can limit the design freedom enjoyed in other beverage applications. The industry has recently developed a ‘panel-less' technology — an opportunity to develop unique designs specially for the fast-paced market segments of juices, isotonics, ready-to-drink teas, enhanced waters and other non-traditional beverages.

The elimination of the vacuum panel has opened up creative design options and introduced a new generation of PET packaging, as it is ideally suited to customising shapes and sizes for a variety of market channels and applications.

Simultaneously with the panel-less initiative, PET converters are expanding the thermal stability of their products beyond the 85°C hot-filling environment into pasteurising and retort processing. Using a combination of design and processing know-how, PET packaging capable of withstanding pasteurising conditions was introduced in the late 1990s.

The first breakthrough came with the successful test market of a pasteurisable pickle jar and was followed by beer bottles. The PET industry now stands ready to provide packaging for food pasteurisation applications and is poised to bring PET packaging to retort applications.

Barrier capabilities

Although PET naturally has barrier capabilities adequate for a great many products, some products need additional barriers to maintain carbonation levels and to protect against oxygen permeation that might negatively impact product shelf life. The PET industry has met the barrier challenge with a multipronged attack that includes monolayer barrier resins, coatings and multilayer containers.

All barrier technology is either passive or active. A passive barrier technology blocks oxygen from entering through the walls of the container and carbonation from exiting.

On the other hand, an active system absorbs the oxygen located in the product, in the headspace of the container and in the sidewalls of the container. This is usually through an oxygen scavenger that binds to and destroys the oxygen molecules.

While a passive barrier system performs consistently over time, an active barrier system has its own shelf life. Multilayer remains the most established barrier technology. It literally involves injecting one or more middle layers between the two exterior PET layers. The middle layers may be recycled PET, passive barrier material, active scavenging material or any combination of the three.

Multilayer solutions are highly effective, but additional capital investment is necessary to equip standard injection systems with multilayer capability.

Coatings have had limited success in the marketplace to date, although new materials and technologies are continually being introduced. Some of the most promising incorporate a silicon material onto the surface of the PET container.

Monolayer barriers may well be the long-term solution. Several products have been introduced utilising both passive and active barrier materials. One key advantage of monolayer technology is that no additional assets are needed to inject the preforms or coat the containers. An additional advantage is that the barrier is in the preform. Applying the barrier after the bottle is manufactured may limit flexibility and increase cost.

Design flexibility

Since the advent of the contoured PET bottles for Coca-Cola, consumer products companies have recognised the value of shapes and designs in reinforcing their branding and differentiating their products on shelves. PET's capacity to be formed, shaped, embossed, debossed, texturised and processed using decoration techniques is unsurpassed.

PET's design flexibility became apparent with the advent of PET packaging in aseptic applications, where the product and the package are sterilised separately and then brought together in clean room conditions. Because the bottles do not have to be heat-resistant, there are more design and weight options.

Aseptic processing is in wide use and is expected to expand as new processing and sterilising technologies are developed and implemented. New emerging categories
made possible by aseptic packaging advances include low acid soya- and milk-based beverages, nutraceuticals and bioactive products.

Sustainability and productivity

Packaging is a fast-paced and competitive industry. One of the primary ways in which the PET industry has maintained its competitiveness is through aggressive lightweighting. The gramme weights of today's PET containers were unimaginable when these packages were first introduced. The 2l soft drink bottles weighed over 70g when they appeared; they now weigh 52g.

Another area in which the PET industry has excelled is in productivity improvements. Looking at injection moulding alone, PET converters have moved from 16-cavity tooling to 144 cavities with reduced cycle times in less than a decade. Blow moulding speeds are clocking 1600 containers per mould per hour, even for high-performance heat set containers. This is in sharp contrast to the 400–500 rates of the 1970s.

Recyclability is another important factor for sustainability. Nearly every PET packaging on the market today has been designed for recyclability. The industry has recognised the importance of keeping the recycle stream clean and has worked hard to ensure that the entire packaging — bottle, label and closure — are recyclable. The challenge to the industry is to use barrier, colour and other additives, while not significantly affecting the recycle stream.

Developing new opportunities

As a major global participant in the PET industry producing over 32 billion units annually, Amcor is committed to PET packaging. Amcor will continue to lead the industry in technology and innovation and to develop new opportunities for its customers and for the marketplace.