Optimisation of low carbon Biodegradable flexible films from waste feedstocks for high-speed processing into single use flexible packaging

A big part of Unilever's recyclable flexible plastic packaging is not being collected, efficiently sorted and recycled, ending up in landfill or leaking into the environment. This problem is more severe in geographies where infrastructure is not in place. Unilever has strategically prioritised the innovation of flexible packaging, such as single-use sachets, because these are inherently difficult to recycle and represent a particularly urgent environmental challenge. Flexible packaging for Unilever products makes up nearly a footprint of 200,000 tonnes of plastic annually.
One of Unilever's key materials of choice for the development of net-zero biodegradable flexible packaging solutions is polyhydroxyalkanoates (PHAs). PHAs are polyesters produced by bacteria from waste feedstocks, can be processed and sealed like plastics and are biodegradable in marine and soil environments. One disadvantage of PHAs compared to current plastics used in flexible sachets is their poor moisture barrier performance.
Unilever has been working on improving the barrier properties of PHA films (the specific grade is commercially sensitive) by developing PHA composite films, dispersing fillers (commercially sensitive) within the PHA matrix. This composite approach resulted in films with improved barrier performance, but decreased mechanical performance, rendering them not suitable for conversion into sachets. In order to be compatible with current sachet manufacturing and filling lines, PHA composite films should meet key mechanical performance requirements.
The objective of this project is to optimise PHA composite films to make them compatible with existing supply chain and manufacturing processes without compromising their packaging performance. The project innovates by using a composite and processing materials approach using low-carbon biodegradable materials:
a) ICL will embed different PHAs and biodegradable polymers within the PHA-filler matrix to improve film flexibility;
b) Biobased plasticisers will be added into the composite to reduce film brittleness. Plasticity is important in process scale up for high-speed conversion of packaging films. In parallel to a) and b), as part of the experimental design, the loading fraction of the fillers will be varied to optimise barrier and mechanical performance simultaneously.
c) Nanofibre spinning will be explored at the Manchester Royce Hub on the key film formulations developed at ICL as a route to induce crystal alignment and biaxially stretched films which are expected to have higher mechanical properties. The tensile properties, fracture-resistance, moisture and gas barrier properties of the flexible composite films, as well as their thermomechanical properties will be characterised and optimised.
The structure-property-processing relationship of the biodegradable composite films will be quantified, allowing for the optimum formulations for process scale up to be identified. The specific facilities to be used are Scanning electron microscopy (SEM), Atomic force microscopy (AFM) and Wide-angle X-ray scattering (WAXS) to study the (fracture) morphology and crystallinity of the composite films, as well as the interaction between the different polymers to allow for the engineering of better performing films.
The melt rheometer, blown film extruder and developmental nanofibres spinning will also be used to process formulations into films. Nanofibre spinning will be explored as a route to induce crystal alignment and biaxially stretched films which are expected to have higher mechanical properties and can be tailored. The advanced nanofibres to devices suite will also be used for production scale up, the Mechanical evaluation suite will be used to study the thermomechanical properties of the films, fibres and consolidated fibres, and the SEM facilities will be used to study the morphology of the films, fibres and consolidated fibres.