Packaging Material
Due to the lack of barrier properties in commodity polymers, packaging material is usually manufactured in a multi-layer structure with other high barrier polymers and metals. These multilayer film has been widely used as a packaging material in various industries from food and beverage to pharmaceuticals. However, multi-layered packaging materials are generally low in recyclability and cause serious environmental pollution, therefore we have faced the challenge of improving the barrier performances as a mono-material. To improve barrier properties without using heterogeneous polymers that are hard to recycle. Small amounts of organic and inorganic fillers that are easy to separate during recycling were utilized in mono-material film to enhance barrier properties. But in order to enhance barrier properties with small amounts of filler, the uniform dispersion of the filler in the film is important. Our research group has devoted on various ways including research on processing conditions and modification of the materials. Recently, by utilizing biaxial stretching method, our group observed that, as the draw ratio increased, the behavior of the agglomerates of the filler located in the polymer matrix changed and the filler was dispersed along the second stretching direction. Also, our group has modified hydrophobic polymer in order to achieve the uniform dispersion of Cellulose Nanofiber(CNF) in the polymer matrix and improve affinity between polymer and CNF. Barrier properties of mono-material films were clearly improved due to this dispersion effect with our researches. Our group anticipate that these effort in high recyclable mono-material will lead to better carbon neutral society.
The deterioration of environmental pollution and the increasing interests of eco-friendly biodegradable materials let us get into the research on the biodegradable materials and processing for packaging applications.
The biodegradable polymer/nanofiller nanocomposites substituting the petroleum-based materials can be used for packaging applications with some additional processing. We have developed the poly(lactic acid)/cellulose nanofiber nanocomposites to satisfy the biodegradability and barrier properties. We have achieved not only this two properties but also mechanical properties for flexible packaging applications.
The biodegradable starch-based insulation foam substituting the expanded polystyrene(EPS) can be used for thermal insulation liners or boxes. We have developed the biodegradable polymer/starch foam to provide thermal insulation properties almost equal or surpassing the EPS.
Our experimental researches on these applications of biodegradable materials for various applications provide the key mechanisms for fabrication of innovative biodegradable packaging materials and the chances for sustainable developments of packaging industry.
Cellulose is a bio-based material and is widely seen as a substitute for petrochemical materials. In particular, cellulose nanofiber(CNF) shows high mechanical strength and barrier property due to its high crystallinity and strong hydrogen bonds between chains. However, CNF is extremely hydrophilic due to the presence of a large number of hydroxyl groups, which limits their use as a water-resistant material. Therefore, we introduce some inorganic fillers to control the permeability behavior. First, it is possible to improve water repellency by adsorbing spherical silica nanoparticles on CNF and modifying to be hydrophobic. We controlled the size and packing efficiency of silica nanoparticles by adjusting the synthesis conditions. In addition, when silica is introduced, the thermal stability and dispersity of CNF are improved. Second, diffusion coefficient can be adjusted by introducing a clay having a plate-like structure to form a tortuous path. In particular, when CNF is used as a matrix, it exhibits high gas barrier and oil resistance when maintaining a hydrogen-bond network. The introduction of impermeable fillers ensures that CNF maintains oxygen barrier property even under high humidity. CNF dispersion comprising various fillers is coated on a film to exhibit water repellent and oxygen barrier performance.