A packaging demonstrator from the Sustainpack project. It incorporates a lightweight cardboard Kraftliner from Smurfit-Kappa, a cushioning material made from biodegradable polymer Mater Bi and an enzyme-based relative humidity indicatorSustainpack is a European research conglomerate that hopes to encourage widespread use of 'renewable' natural fibres in paper and board in packaging, by adding value and functonality. Rupal Mehta talks to some of the researchers involved and reports on the conference that concluded this four-year programme, held from 6-7 May in Prague, Czech Republic.

In an industry that is facing challenges to combine added functionality with environmental sustainability, the 30m euro, four-year Sustainpack project aimed to plug a gap in the packaging market. The initiative was a vast undertaking into the materials science and subsequent use of renewable natural fibres, combined with bio-based polymers, in the packaging of the future.

The consortium, part funded by the EU Sixth Framework Programme, comprised 35 European partners from packaging research organisations, academia and industry from 13 countries.

‘Fibre-based packaging needs to perform better with new fibres, improved barrier properties and increased interaction with the user. All without adding any non-renewable resources. The purpose is to ensure that fibre-based packaging is a dominant player,’ said Staffan Erenmalm, a member of the Supervisory Board at STFI-Packforsk, an R&D company covering paper, pulp and packaging, headquartered in Stockholm, Sweden.

But while his introduction to the conference which concluded Sustainpack, held from 6-7 May in Prague, Czech Republic, set the agenda for the event, it was inevitable that the notion of what is ‘sustainable’ would still be up for debate.

Taking stock

‘It is difficult to identify priorities as sustainability is all encompassing,’ said Paul Earl-Torniainen of General Mills Inc, an international marketer and manufacturer of food products based in Golden Valley, USA.

Materials such as steel, aluminium and PET are made from non-renewable resources but have established recycling streams. Meanwhile, bio-based polymers reduce the use of finite resources such as petroleum, and in turn carbon emissions, but some varieties open up concerns about diverting crops away from food and release methane as they biodegrade. A material advantage at one end of the lifecycle can therefore be offset by a disadvantage elsewhere.

Arno Melchior, Global Packaging Director at Reckitt Benckiser, UK, specialists in home cleaning, health and personal care products, provided an industry perspective from a non-Sustainpack partner. ‘We have launched a project called Carbon 20, which is to achieve a 20% reduction in our carbon footprint,’ he explained.

‘The objective is to use packaging materials for which a recycling stream exists in those countries where we sell our products – so we do not use biodegradable products at the moment. If there’s enough biodegradable material, we need a [national] recycling/composting stream. Consumers need guidance
from legislation.’

This view was echoed by Cecilia Giardi of R&D Strategic Projects at Novamont, in Novara, Italy, which manufactures Mater Bi – a biodegradable and compostable polymer based on vegetable starches. She said, ‘How do you build a sustainable base for bio-based plastics? It can only be achieved with a separate waste collection’.

She added, ‘If a normal plastic tray is contaminated with food, it goes to landfill. If you use a bioplastic, then it is homogeneous with the organic food waste as both fractions can be composted’.

Hooked up

Earlier this year, Reckitt Benckiser re-launched its Air Wick Freshmatic air freshener in Europe in a cardboard box, moving away from the traditional plastic blister pack. The team behind it optimised the amount of material used by moving the flaps of the box from the top and bottom ends to the sides and developed a ‘hooked’ design that eliminates the need for a hot melt adhesive to glue the walls together. In turn, the company reduced the size of the box from 400g/m2 to 300g/m2, which has saved 3,000t/year of cardboard, and diverted 300,000kg/year of hot melt glue away from landfill.

However, Melchior added, ‘Paper has the largest CO2 footprint in the distribution chain. In France, we distribute with our competitors so the lorry is not half empty’.

It is therefore a complex lifecycle assessment, he argues. ‘If we do an assessment in Germany and Brazil for the same packaging, I would get different results. Even on the same manufacturing site, I could get different results depending on where the [raw material] supplier is. We need to develop a standard value.’

Laying the foundations

With this in mind, as researchers presented their materials science advances and packaging demonstrators resulting from Sustainpack, many delegates questioned the ability for such materials to be industrially processed and the disposal methods required.

Much R&D and complex analysis remains to be done but significant progress has been made. Talking to Materials World, Kennert Johannson, Coordinator of Sustainpack from STFI-PackForsk, is optimistic about the future of the research.

He says, ‘If we develop a material that has good and competitive properties, I think there will also be methods developed to take care of them. We have had recyclability tests for the materials and so far found it is possible to recycle them. Coming from a nordic country we see incineration with energy recovery as equally important’.

He adds, ‘We have already seen EU research projects follow up on Sustainpack. Some findings are close to commercialisation. I think one crucial factor is to create an interest to go further with the findings’.

Technical research projects

Sustainpack comprised six technical research projects that encouraged collaboration across organisation and borders. Numerous packaging demonstrators were developed. The projects were:

Research coordination role – to determine the market needs and identify research requirements to direct the other technical research projects.

Lean and effective fibre-based packaging – creating a nano-facility to produce nanoscale cellulose and mineral structures, and exploring surface modification, multilayering and grafting of fibres.

Fibre-based composite films – incorporating nanofibres and bio-based polymers to compete with the properties of synthetic polymer films.

Protective coatings – to develop coating and printing technologies to enhance barriers and other functional properties.

3D composite packaging – comprising fibre-reinforced bio-based polymers.

Communicative packaging – to add value to packs with devices such as time-temperature and humidity indicators for food products, reducing food waste.

Modifying cellulose fibres for biocomposites through grafting and nanotechnology

Researchers at the French Engineering School of Paper and Printing (EPFG) and the University of Aveiro, Portugal, collaborated on research, as part of Sustainpack, to incorporate cellulose fibres into bio-based polymers such as PLA, Mater Bi starch and cellulose acetate butyrate, or biodegradable polymers such as polyester-like polycaprolactone or Mater Bi polyesters. The aim was to improve the mechanical properties of such ‘bioplastics’ to compete with petroleum-based alternatives for films and 3D packs.

Dr Julien Bras of EPFG says, ‘Cellulose fibres have several advantages – [they are] renewable, low density and already exist in industry. But they have one drawback – hydrophilicity, which creates problems of mechanical compatibility with hydrophobic polymers’. Bras explains that previous fibre modification techniques, such as co-polymerisation of fibres to the matrix that rely on fatty isocyanates and anhydrides, do not create a strong enough link between the materials. Two new techniques have been developed to ensure effective grafting of the fibres, covalent bonds and compatibility – a copolymerisation technique that uses a difunctional molecule and a proprietary ‘click chemistry’ technique. Grafting gives an enhanced Young’s modulus.

Bras adds, ‘We will also work on 3D packaging obtained by injection moulding [and] new ways of grafting to increase compatibility but also give active properties, such as antimicrobial and photoluminescence’. On this theme of active packaging, the team has already explored the potential for an anti-ripening pack using inorganic nanoparticles, such as non-toxic titanium dioxide, to improve the properties of cellulose fibres. By preparing a 3D composite with a biodegradable polymer, researchers found the nanoparticles did not impact on the mechanical
properties, but rather further delayed water penetration of the material. Titanium dioxide also destroys ethylene, which is produced by fruit and vegetables and accelerates ripening and decomposition.

Spot coating and nanoclays

‘Some of the bio-based barrier coating materials which are currently under development exhibit poorer heat sealability than conventional polymers,’ says Isabel Mira of the Institute for Surface Chemistry, in Stockholm, Sweden. She worked on a Sustainpack project to develop a novel spot coating technique that involves ‘localised application of protective or priming functions to target areas’. For example, materials commonly used as paper coatings – latex, a polymer dispersion and a water soluble polymer, such as polyvinyl acetate – have been formulated into a ‘heat-sealing ink’ that can be printed using flexography or ink-jet to reinforce paper-based packs along creases and folds, and reduce cracking of the barrier coating. This minimises the ‘use of non-bio-derived [barrier] lattices in packaging,’ adds Mira.

Professor Christopher Breen, of Sheffield Hallam University, UK, worked in a team that explored the use of nanoclays to enhance the barrier and mechanical properties of paper coatings and bio-based polymers. To make the clay particles more compatible with the polymers, researchers used a range of unusual modifiers, including chitosan derived from the shells of crabs and lobsters.

Microfibrillated fibres and biomimetics

A number of scientists involved in Sustainpack explored the use of microfibrillated cellulose fibres (MFC), such as from spruce pulp or carboxymethylated dissolved pulp with six per cent hemicellulose. These fibres are derivatives of the fibre walls. One project looked at replacing expanded polystyrene as a cushioning material in packaging with a MFC-reinforced vegetable starch polymer.

Professor Lars Berglund of the Royal Institute of Technology, in Stockholm, Sweden, explained how amylose-rich starch alone could not be used for foam production due to poor rheology during expansion. He said, ‘You need to monitor the stress-strain curve. Starch has a high density and low energy absorption. It absorbs a lot of water at ambient conditions.

‘You can solve this by looking at a plant structure – primary cell walls are strong and tough despite high moisture and cellulose content. What’s important is the network. It’s a sophisticated structure. Cellulose stiffness is equivalent to Kevlar,’ he added. By reinforcing the starch foam with MFCs from wood and freeze drying it, the team claim to have created a porous structure with strong mechanical
performance. Industrial-scale compression and injection moulding manufacturing
techniques have also been investigated.

Opto-active paper

On display at the Sustainpack conference was an opto-active paper, made from a combination of renewable materials such as microfibrillated cellulose, gelatine and carragennan, that changes colour when exposed to moisture. The colour change reverses in about five seconds and the different hues depend on the thickness of the thin interference films (about 100-200nm), which are created by spraying water-soluble polymers or particle dispersions on the paper. Papers that respond to other external stimuli could also be manufactured. Hjalmar Granberg of STFI-Packforsk in Sweden says, ‘Interference films are commercially available as security features on packaging and bank notes. Stimuli-responsive films are new and can be used for interactive displays, product safety, sensors and anti-counterfeiting’.

Further information:

Sustainpack