Sea freight packaging

Materials World magazine
,
1 Jul 2014
containers on a ship

Melanie Rutherford speaks to Professor Bernd Sadlowsky, Managing Director of German packaging advisory body BFSV, about the materials developments currently underway to improve the protection of seashipped goods in an increasingly carbon and price-conscious industry.

Shipping is one of the earliest methods of transporting freight and remains one of the most economical ways to transport goods for commercial or industrial use, from fresh fruit to heavy-duty machinery. Transporting freight to the destination country in the same condition as it left the port requires some special considerations. ‘The correct choice of packaging materials as well as the construction and quality of the packaging are essential for a safe and damage-free transportation,’ says Professor Bernd Sadlowsky, Managing Director at German advisory body BFSV Packaging Institute. ‘Most damage in sea transportation is caused by mechanical and climatic stresses.’ These stresses are many and varied. Temperature and humidity, for instance, will change depending on region and local climatic conditions. Take the example of shipping in an unventilated, closed container from Dresden to Beijing. In winter, temperatures can vary from -5°C to 45°C during one journey. In the summer months, it can vary from 10°C to 50°C.

Until the 1970s, the majority of bulk-shipped goods could be found loaded into stacked wooden crates and corrugated board boxes. It was around this time that sea freight containers were introduced, effectively reducing stacking loads. ‘This saw the use of new wooden packaging materials, such as oriented strand board and plywood instead of solid wood,’ says Sadlowsky. ‘Wood-based materials have several benefits, including homogeneity, their availability in various dimensions, stability across those dimensions, reduced anisotropy of the raw material and lower costs.’ The introduction of these materials brought about efforts to improve the qualities of corrugated board to make it suitable for overseas transport, including waterresistant properties and gluing methods.

Since its invention by American Albert Jones in 1871, corrugated board has been one of the most important and popular packaging materials for transporting goods, largely due to its low cost and sustainability credentials. Wooden packaging is popular for heavier goods, as it is reusable and sustainable. Plastic is less popular for freight – not only is it less sustainable, but it can fragment if damaged and requires cleaning if it is to be reused. Foils, meanwhile, are generally only used to keep the freight together.

All aboard

Currently, more than two thirds of goods worldwide are packed in corrugated board. A 2014 report published by German corrugated board association Verband der Wellpappen-Industrie, which compared international sales volumes of corrugated board from 2011, showed that Europe sold 42.9 million square metres that year – second only to China, which produced 53.6 million square metres, and ahead of the USA sales volume of 33.4 million square metres.

There are several reasons why corrugated board has stood the test of time. Sadlowsky explains, ‘Its special construction provides excellent strength properties to withstand pressure and bending loads in all directions. Other advantages of corrugated packaging are its recyclability, machinability, good damping characteristics and versatility in terms of design.’

Existing packaging materials are constantly being improved, especially where the composition of the individual components varies. For example, the fibre composition of corrugated board and the type of bonding can be modified to improve its strength properties. Sadlowsky explains, ‘For sea freight, this is characterised by an increased virgin fibre content and a wet-strength adhesion to withstand the loads during transportation. In addition, composite materials are increasingly coming under focus, such as shipping boxes made of corrugated cardboard reinforced by wooden components.’

Due to the growing volume and frequency of imports and exports worldwide, more packaging is needed that is able to withstand higher loads during transport and storage, including humidity and changing temperatures. Humidity is the biggest influence, says Sadlowsky. ‘The fibres in the board adapt their moisture to the ambient humidity, and increased moisture leads to creep, resulting in loss of strength. But even under these extreme conditions, packaging cannot collapse and must carry the commodity safely and undamaged to the destination. However, in an attempt to keep freight costs low, savings are most often made on the packaging. This increases the risk of transport damage, an issue that is often neglected.’

Environmentally aware

Like every other sector that leaves a carbon footprint in its wake, the sea freight industry is under pressure to reduce its environmental impact. With consumers and manufacturers increasingly environmentally aware, packaging recyclability and carbon footprint are at the centre of several R&D projects, with particular focus on materials suitable for protecting sea-shipped goods. ‘The main R&D objectives in this field are to increase or improve strength while reducing use of raw material and lowering costs,’ explains Sadlowsky. ‘To achieve this materials saving without increasing the risk of transport-induced damage to the product requires investigation of the material’s strength, particularly over the long term.’

BFSV is conducting several R&D projects with the aim of improving temporary corrosion protection, to prevent moisture and temperature-induced damage of sea freighted goods during transport and storage.

The first is the development of a rule on the interpretation of volatile corrosion inhibitor (VCI) substances in packaging of metallic products, taking into account previously untestable parameters. VCI materials can be incorporated into polyethylene, polypropylene, polyurethane, paper and foil. VCIs are transported from the packaging into the surrounding space, and then absorbed by the product’s metallic surface, effectively protecting it against corrosion and oxidation. Sadlowsky explains, ‘The new test method will allow us to reliably study the effects of VCI substances via repeatable tests, alongside other testable parameters that impact the corrosion protection effects of VCI products. For example, we will be able to determine the optimum time required to build the necessary corrosion protection according to the distance between the metal sample and the VCI carrier.’ While development of the tests is still in its early stages, it is hoped that it will improve the reliability of VCI material use and, therefore, greater acceptance of the method.

The other two areas of R&D focus on predicting the long-term behaviour of corrugated board packaging (for example, during warehouse stacking or worldwide transport), and on the implementation of an authoritative calculation benchmark for wooden packaging for heavy loads. ‘The creep behaviour and the long-term sustainability of corrugated cardboard can currently only be estimated based on short-term tests or extensive long-term studies,’ says Sadlowsky.

To enable a reliable, time-saving and space-saving assessment of creep, prototype creep rupture test apparatus on edge crack torsion (ECT) specimens is under development. These specimens comprise of rectangular laminates with an edge delamination at the mid-plane. Torsion loading on these specimens leads to relative transverse shear sliding of the delaminated faces. Based on European and international standards, the new test method will allow manufacturers to accurately ascertain the long-term strength of their packaging in a much shorter time. ‘Being able to predict how corrugated board and wooden packaging will be affected throughout the life of the pack will reduce the amount of testing required and speed up the test process,’ says Sadlowsky. ‘It should also make predicting the long-term strength of packaging more accurate than was previously possible. This time- and cost-saving test method will help avoid unnecessarily oversizing packaging and, in turn, reduce raw material weight and therefore costs. However, further investigation is necessary to bring the measured creep rates of the specimens in strong correlation with that of corrugated board packages.’

The author would like to thank Frank Volkmann and Viktoria Köstner for their contributions to this article. For further information, email koestner@bfsv.de