Packaging Technology and Engineering. Dipak Kumar Sarker

species of bacteria are thought to be able to digest PET as a food source; this opens up more avenues for improved recycling or disposal by species found in the natural environment that degrade the waxy and wax‐like materials.

The next cluster of packaging materials includes PP, PS, and polyvinyl chloride (PVC). PP as a packaging material is resistant to chemicals, heat, and moisture. It is a plastic that has moderate rigidity, being used for ketchup bottles, medicine bottles, yogurt pots, and lids. It has the lowest density among plastics used in packaging and accounts for up to 11% of all plastics. PS packaging can be seen in rigid containers and in expanded insulating foam. In a non‐expanded form it is a very tough, highly transparent, and bright plastic used for protective packaging (egg cartons and meat trays) and may account for up to 10% of all plastics. PVC packaging exists in two forms – hard and elastic varieties (constituting 5% of all plastics) – and is often used to make bottles for vegetable oil and shampoo; it is also used in pharmaceutical push‐out‐packs. PVC was initially discovered by Henri Victor Regnault and later refined for potential use by Eugen Baumann. Approximately 40 years later in 1926 Waldo Semon mixed different additives into PVC to make it more pliable; this resulted in an easier‐to‐process material and allowed its widespread use (5% of all plastics). Concerns in the 1970s over the vinyl chloride (C₂H₃Cl) monomer (frequently referred to as VCM), bisphenol A ((CH₃)₂C(C₆H₄OH)₂), and dioxin (dioxin‐like compounds, e.g. 1,4‐dioxin) present in the material have somewhat spoilt the reputation of PVC as the superpackaging material that it is. From the 1970s, VCM exposure was linked to a rare form of liver cancer, known as angiosarcoma. The US Environmental Protection Agency classified VCM as a known human carcinogen from this time onwards, with factory workers being the most common victims of VCM over‐exposure.

      1.2.2.7 Composite Packaging

      Composite packaging is made from combining at least two different and often physically distinct materials. The goal in combining various materials is to increase the mechanical and chemical properties of the materials over those observed in any single material. Sometimes composite materials also demonstrate unique properties not seen with either individual material through an effective synergism in the physical properties of each material. Commonly used examples include plastic–aluminium composite packaging used for steam retortable pouches; cardboard–PE composite packaging used for Tetra Brik® cartons; paper–PE composite packaging, frequently used for medical sachet pouches; plastic–paper–aluminium composite packaging used for UHT sterilised product cartons; and paper–aluminium composite packaging used as the webbing for pharmaceutical push‐out packs. In some more modern combinations hemp and flax woven materials are embedded within plastic to produce more rigid materials and a range of contemporary ‘bioplastics’ make use of this composite structure.

      1.2.2.8 Novel Materials: Bioplastics and Oxo‐Degradable Polymers

In recent times, the term ‘bioplastic’ has become increasingly prevalent in packaging industry circles. These substances are innovative polymeric materials that can mimic the properties of conventional plastics. However, these materials are made from products or by‐products of raw materials from renewable sources. In many applications, bioplastics can be used as a like‐for‐like substitute for hydrocarbon‐derived plastics. Bioplastics can also be produced from many plant‐originated raw materials; notably, starch has a very significant place among them. Cellulose and simple sugars are the other important raw materials for a range of polymers. Bioplastics can be thought of as a viable alternative for a wide range of renewable raw materials derived from simple species for potential packaging uses. At present, and most probably because of societal uptake, their cost remains two to three times higher than that of conventional materials [12]. Biopolymers currently gathering much interest as alternatives to polyolefins include polycaprolactone, polyamide, polylactic–glycolic acid, polycaprolactone (PCL), and polylactic acid (PLA). Importantly, with regard to the persistence of plastics in the environment and according to European standard EN 13432, these materials can be degraded under particular conditions and reduced to a compost.

      Although it is currently considered impossible to produce sufficient raw materials to supply the current global need for plastics, even if all possible efforts were put into bioplastics production, their use alongside better recycling could achieve this end. Other materials called oxo‐(bio)degradables are produced by methods such as adding biological materials to those polymer materials obtained from petrochemical products. Oxo‐biodegradation is a type of degradation resulting from oxidative‐ and microbe‐mediated processes or phenomena in combination or in succession. The emergence of packaging materials made from composites and complex blends of fats and waxes with proteins such as zein (maize) or gluten (wheat) along with starch [13] and chemically modified hydroxypropyl‐ or hydroxyethyl‐cellulose is becoming commonplace [14] for sheeting and adsorbent hydrogel uses in packaged products. Foam ‘peanut’ insulation (Envirofill) and cushioning transport materials (see Figure 8.6) fabricated from thermoplastic starch for applications where expanded PS was previously used have provided good opportunities for growth as more than 220 million tonnes of plastic are used worldwide each year for these purposes. Starch‐based packaging that is often used for secondary packaging includes Bio4Pack (Germany). These bioplastics include starch (corn, pea, and potato) and natural fats (hemp oil, soya oil, etc.). They often make use of blends such as PLA and PCL or on occasion PET and mix this with starch. Starch‐based plastics routinely contain sorbitol or glycerol as plasticisers to increase flexibility [15]. Bioplastics still account for a very small proportion of the total plastics market share – approximately 2% of plastic use. Currently obtainable materials include bioplastics such as starch–PLA, called Biotec (Germany); a starch–PET/PE blend, called Plantic ES (Australia); starch–PCL, called Mater‐Bi (Italy); starch–(polybutylene adipate‐co‐terephthalate), called Ecoflex (BASF, Germany); a starch polyester (Bayer‐Wolff Walsrode, Germany); a starch polyolefin (Roquette, France); kenaf (Deccan hemp); and a fibre–PLA material (NEC Corp., Japan). Routine use of PET is hoped to be replaced with a sugar cane‐derived monoethylene glycol–PET material used for the soft drinks industries called PlantBottle (Dasani/Coca‐Cola Company, USA). Thermoplastic starches called Chisso (Japan) and another variant called Envirofill based on an expanded product (DuPont, USA) represent promising new candidate materials. Unfortunately, biopolymers of this type tend to degrade easily at 180 °C and consequently, at present, many are combined with oil‐derived plastics from a performance point of view and this informs design strongly [16]. European standard EN 13432 and ASTM 6954 describe the criteria and precisely controlled conditions used in prescribed tests for degradation at 60 °C in order for a material to be considered as biodegradable. The biopolymers suitable for packaging applications [15], including starch, chitin/chitosan, cellulose derivatives, PLA, PCL, poly(butylene succinate), and polyhydroxybutyrate, are discussed in detail in other publications.

References

      1 1 Risch, S.J. (2009). Food packaging history and innovations. Journal of Agricultural and Food Chemistry 57: 8089–8092. https://doi.org/10.1021/jf900040r.

      2 2 Goldsmith, R.E. (1999). The personalised marketplace: beyond the 4Ps. Marketing Intelligence & Planning 17 (4): 178–185. https://doi.org/10.1108/02634509910275917.

      3 3 Gustavo, J.U., Pereira, G.M., Bond, A.J. et al. (2018). Drivers, opportunities and barriers for a retailer in the pursuit of more sustainable packaging design. Journal of Cleaner Production 187: 18–28. https://doi.org/10.1016/j.jclepro.2018.03.197.

      4 4 Fadiji, T., Coetzee, C., Chen, L. et al. (2016). Susceptibility of apples to bruising inside ventilated corrugated paperboard packages during simulated transport damage. Postharvest Biology and Technology 118: 111–119. https://doi.org/10.1016/j.postharvbio.2016.04.001.

      5 5 World Health Organization. (2002). Annex