Packaging Technology and Engineering. Dipak Kumar Sarker

the ‘modern’ form of paper is thought to date back to the Han Dynasty (200 BCE to 200 CE). A Chinese court official, called Ts'ai Lun, in north‐eastern China fabricated fine‐grade paper sheeting by improving on an existing process dating from a century prior to his technological advancement. This paper was fabricated from fine‐fibre materials, such as mulberry, and the bark from nettles, hemp, and flax. The first recorded use of wrapping paper dates back to 100 BCE with paper made from hemp. The first paper book was dated at 256 CE and by 300 CE paper use was widespread in China and Japan. From about 750 CE paper use was seen to move from China via the ‘silk route’ to the Middle East. At approximately 900 CE paper was found ubiquitously in Egypt with an early form of paper packaging being used for wrapping spices and fruit dating back to 1035. From this point in time, paper use spread to Europe through the Spanish courts in 1085 and then on to the rest of Europe via France. By the late sixteenth century paper production in Europe was well established and there was a more formalised form of paper mill‐based production of paper in England, Denmark, the Netherlands, and Russia. In 1844 Friedrich Gottlob Keller and Charles Fenerty began undertaking experiments replacing cotton fabrics and substituting with an exclusive paper made only from wood pulp. Importantly, Henry Fourdrinier, a British engineer, and his brother, Sealy, invented and improved on a prototype of the casting Fourdrinier machine. The paper‐making machine changed the process from one of batch fabrication to one where continuous variable sized rolls of paper could be made with ease.

The basic raw material for making paper and cardboard packages is the polymer cellulose. Cellulose for paper pulp is usually obtained from specific species of trees and plants, which grow quickly, are easily replaced, and allow the material to be easily mechanically or chemically pulped. Favoured species include the cotton plant, which produces fine‐grade paper, and cellulose‐rich softwood trees, such as larch, pine, and spruce, or hardwoods, such as birch and poplar. Paper pulp may also be used to create cardboard that does not require the fine‐grained structure of refined paper. Both paper and paperboard boxes and cartons are among the most cost‐effective ways of packaging goods and have the added advantage of excellent recyclability. Commercial paper and cardboard for packaging applications require sound puncture or tear resistance and need to offer the pack contents protection from humidity and light.

      Corrugated cardboards are produced by two flat paper liners bonded to one another by a corrugated layer called fluting. The three or more layers are glued by a material usually made from maize starch or polymeric water‐based adhesive. This gluing function provides the material with strength and unity and enables the material to provide cushioned protection of the encased product against impact from the corrugated layer. Secondary packaging made of corrugated cardboard is very popular among manufacturers. This is mainly because of the cheapness of these packages but also the low weight to high strength ratio that provides adequate protection [4]. Key performance‐indicating test methods for packaging include puncture resistance to defy a force that will allow a tool of a specified shape and dimensions to puncture and pass completely through a test specimen. Similar test criteria can be applied to tear and bending deformation and bursting strength resistance along with crush resistance.

      1.2.2.5 Wooden Packaging

      Commercial wooden packaging is a rarely used commodity in modern times. Despite being one of the oldest packaging materials, its use for foods, pharmaceuticals, and medical devices is now virtually non‐existent. A combination of weight, fragility, risk of contamination during transport or reuse, and durability mean its only use is for luxury goods and some fruit or vegetable shipments. Wood used for packaging material is customarily treated with pesticides and insecticides to avoid infestation and to protect its contents. Examples of the persistent use of wood include pallets (for heavy goods), boxes (often for valued products such as tea and coffee), crates (fruit or wine), and barrels (beer, wine, and liquors).

      1.2.2.6 Plastic Packaging

      The plastic packaging used across the globe is made from processing various products from crude oil and gas. However, only about 5% of global oil resources are used in the production of plastic and an astonishing mere 3.5% of this small amount is lavished on the production of plastic packaging. Plastic can be used for both packaging body and closures and, with the aid of designer input with ever less material, to produce even more packaging. As a consequence of their ductility, malleability (plasticity), and ease of shaping, ‘plastics’ remain one of the most popular classes of materials for universal packaging needs. Plastic use as a ubiquitous packaging material did not start until the 1950s; it gained momentum up to the 1970s and is now globally a matter of prime concern with respect to its ineffective disposal and frequent single use.

Acrylonitrile (AN) and its related family of packaging materials are often used when pliability is required. There are many different types of AN‐based plastics and synthetic rubbers. Materials in this grouping include acrylonitrile–butadiene–styrene, a terpolymer (three different monomers) with extremely good chemical resistance and flexibility, or the copolymers styrene–acrylonitrile, which is more thermally resistant than polystyrene (PS) alone, and polyacrylonitrile or Creslan 61, which is thermally resistant but also possesses some unique metal‐binding properties. On combustion, as part of the energy‐recovery processes of waste plastics or thermal recycling because of the acrylonitrile (AN) group (CH₂=CH–C≡N), the compounds are known to liberate cyanide gas and carbon monoxide. In opposition to AN, polycarbonate (PC) packaging is easy to process, cover, and shape with heat‐forming capability. These types of plastic have a wide area of usage in the modern production sector, where toughness and a durable character with respect to impact are required. Consequently, PC plastic is now used for ampoules and ‘plastic glass’ mimics. This polymer is very transparent and light transmitting – actually being better than most types of glass. Water bottles used in homes and babies' bottles populating nurseries around the globe are made from PC material. The best property of PC lies in its durability to impact, which is why it is also used for prefilled syringes and industrial safety glasses.

      The PE group of packaging materials represents the single biggest category of plastic used in packaging but also universally across all sectors. Recycled PE is used for milk bottles, medicine bottles, and many general containers and can account for up to 61% of all plastics in the recycling stream. HDPE is a tough, malleable, abundant, and cheap material but its natural opacity due to light scattering means it cannot be used in products where transparency is needed. Nevertheless, it is one of the most widely used plastics of all those that are currently available to manufacturers. HDPE, which is a particularly tough version of PE, is also utilised for tubs used for cheeses and butter and boil‐in‐the‐bag food products and may account for as much as 29% of all plastics. Low‐density polyethylene (LDPE) is a semi‐opaque, tough, durable plastic but with an elastic, easy‐to‐cut character. LDPE plastics are used mostly in pack‐film materials by virtue of being smooth, elastic, and relatively transparent. LDPE plastics are also routinely used in the manufacture of bags and in the elastic lids of many types of jars. This type of plastic may account for an incredible 32% of all plastics and, along with HDPE, accounts for a significant portion of environmental plastics and micro‐plastics.

      PET packaging, depending on the thermal treatment, is an amorphous (transparent), semi‐crystalline (opaque), flexible, and valuable packaging material (representing 9% of all plastics used). Depending on PET film thickness it may be rigid or semi‐rigid and this can dictate its possibilities for end use. At a density of around 1.39 g/cm³ (cf. 2.7 g/cm³ for aluminium and about 2.8 g/cm³ for glass) it is a lightweight material that has excellent gas and humidity barrier properties. Simultaneously, it is mechanically tough and highly resistant to impact, making it ideal for bottles such as liquid pharmaceutical containers and carbonated drinks bottles as well as jars and trays. The semi‐crystalline form of PET, known as CPET, is used almost exclusively for oven‐ready meal trays because of its high thermal resistance. The now common PET bottle was first invented in 1973 but has since spread to use in some ‘plastic cans’ that consist of a transparent or printed PET body and aluminium lid, often with a pull‐ring (Minuman, Invento, Lino, and Sino Packaging). The most important advantage of PET usage is that it possesses sound multiple recycling characteristics; consequently,