By Lorrin Windahl.
So I mentioned in a previous post that polystyrene foam, which has been used for many years as a good impact resistant packaging material, is slowly being outlawed worldwide due to its low sustainability credentials. So what can be used as an alternative? One word – pulp.
You’ve probably seen moulded pulp used in packaging if you have recently bought a new phone or computer. The big organisations such as Dell and Apple, who are worried about their environmental impact (or more so their consumer’s perception of it), have started to adopt this material. So what exactly is pulp and why is it so much better?
Put simply, pulp is made up of different fibres, usually recycled paper, that are mixed together with water to create a slurry and then pressed into the desired shape. Egg cartons are probably the most recognisable packaging made from moulded fibre pulp.
There are two decisions that need to be made when using moulded pulp. They are the type & grade of pulp and the mould process.
Moulded pulp is most commonly made from recycled paper. At the low end you have recycled newsprint which is very cost effective but doesn’t give you a great finish. This is good for packaging that needs to support the product but is not seen by the consumer until they open the packaging. At the other end of the scale you have recycled office paper pulp which provides a better finish and is good if you are worried about the aesthetics of the packaging. But if you want an even higher grade pulp you could look at using bamboo or sugarcane pulp instead of paper which gives a higher definition finish. This is also suitable for food grade packaging because it is a virgin material unlike recycled paper pulp.
The moulding method used also has a big impact on the quality and finish of the moulded pulp. There are more choices here too. At the low end you can have a single sided tool that forms one side of the pulp. This is how egg cartons are made and if you check one out you will notice one smoothish side and one fairly rough side. Typically the smooth side, which is the one formed by the tool, is used on the visual side. After the pulp is formed it is air dried or heated in an oven. However, if it is important to have a good finish on both sides then there is the option of having a two step process. Instead of air or oven drying the moulded pulp is placed into a heated two sided tool. By compressing the part whilst drying it, the pulp becomes denser and higher tolerances can be achieved. It also creates a smooth surface finish on both sides and therefore higher quality parts are produced.
As a sustainable material I think pulp is very good. Not only does it use recycled and renewable content it is also biodegradable, compostable and recyclable. In practical terms it has a good impact and heat resistance. From an environmental point of view it can have a relatively low impact especially when the pulp is dried in the sun.
Although primarily used for packaging it is fantastic to see pulp weaving its way into product and furniture design too.