Good for business - good for the environment Lightweighting PET packages is a hot topic these days, but it is not a new trend. It has been going on for as long as there have been PET packages. In the past the interest in lightweighting rose and fell with resin prices. Now there is a new force in the market that is driving lightweighting – the need for more environmentally friendly packaging solutions. Lightweighting has both financial and environmental benefits. This article explores those benefits and the steps necessary to make the transition to a lighter bottle.

 

 

While there are a number of ways to be more environmentally responsible, one of the most obvious is to reduce the amount of material used in packaging. Lightweighting PET bottles means that less plastic is used in the manufacturing process and less plastic has to be recycled, reclaimed or dumped after use.
A further environmental benefit of lightweighting is energy saving. There is less energy used in the disposal or reclamation of the bottle after it is sent for recycling or waste management, and lighter bottles need less energy to produce. For every one gram of weight reduction in a preform approximately 500 kWh per million preforms can be saved - this is roughly the daily energy consumption of two 72-cavity preform moulding systems.

Also good for business

Although these energy savings are not insignificant, they pale in comparison to the potential cost savings that lightweighting offers in terms of reducing the amount of resin required.
For every one gram of weight reduction in a preform, the savings are approximately ,600 dollars in resin costs per one million preforms.

How to get there

Even though the commercial and environmental benefits are clear, there are some preform and bottle manufacturers who have not explored lightweighting because they fear that the conversion process will be either too complicated or too costly. However, moving to a lighter bottle is easier than it may seem. It does not, for instance, require a new machine, but merely involves modifications to the mould.

The key to a successful transition to a lighter weight bottle is to work in partnership with knowledgeable injection moulding and blow moulding equipment suppliers. PET bottles are produced using both processes, and lightweighting requires an analysis of the preform and the bottle.

The most obvious consideration is the physical performance requirement of the package. Meeting specifications such as burst strength, top load and side load is critical to the success of a lightweighting project. It is also important to determine whether the bottle will run down a filling, labelling and palletizing line with no loss in efficiency. Success in lightweighting cannot be claimed if the trade-off creates new waste elsewhere in the process.

Once these things have been analysed the next step is to consider the blow moulding of the bottle and, again, make sure that no loss of efficiency will result from the redesign of the package. Designers will often go through multiple iterations of a bottle design before finalising the right one. Today’s computer simulations reduce the number of iterations required, but prototyping is still needed to uncover all of the issues that a particular design may face.

 

Bottle weights for different beverages from 1996 to 20007

 

Preform design

The next step in the design process is to look at the preform and determine the right shape to optimise injection moulding performance while still meeting the other criteria already discussed. Making prototype preforms for blow moulding trials is a sound investment, as it will often help designers squeeze the last few fractions of a gram from the preform specification. Having the prototyping carried out by a leading injection moulding company such as Husky means that the designer can balance the needs of the injection moulding process with the needs of the blow moulding process, thus arriving at an optimum solution.

Today, there is a trend towards higher stretch ratios as part of the lightweighting of carbonated drink bottles. Increased stretching can improve the physical strength of the bottle, offsetting any loss in strength from the reduction in material. The downside to this has been that higher stretch ratios call for thicker preform walls and therefore slower injection moulding cycles. Husky’s high performance package on the HyPET preform systems helps to facilitate the use of lighter, higher stretch-ratio preforms through improved cooling and faster cycle times.

Ice River Springs – a company that realises the advantages

A good example of a water bottler taking the initiative on environmentally friendly packaging is Ice River Springs in Ontario, Canada. Ice River has just launched its lightest-ever, half litre water bottle at 11.8 grams - down from 13.5 grams in the previous design. 
“Reducing the weight of our 500ml bottle is a great example of how helping the environment can benefit everyone,” said Jamie Gott, President of Ice River Springs. “We are continuing to push for lighter weight bottles to help reduce our carbon footprint.”

PET packages will continue to get lighter as the technology leaders in the industry continue to develop new solutions that address the limiting factors as they arise. The continual improvement in the cost and performance of PET is one of the reasons that it will continue to be the packaging material of choice over glass, cartons, cans and HDPE.