Читать книгу Packaging Technology and Engineering - Dipak Kumar Sarker - Страница 18

Plastic packaging had begun to be used widely across the globe after the 1950s and this has led to the present ‘mountains’ of undegraded waste that are still added to. Polyvinylidene chloride, or Saran®, was first used as a moisture barrier in 1946. In 1960 the two‐piece drawn and wall‐ironed (DWI) can was developed and in 1967 the ring‐pull opening was invented. Towards the end of the 1970s the plastic packaging sector had begun to grow, with the blow‐moulded PET bottle invented by DuPont. It was not until after the Second World War that general use of plastics in packaging applications started at a significant level. PE was mass produced during this period in Europe and became an easily obtained material from the late 1940s. At the beginning of this period it was a substitute for the wax paper used in bread packaging and still observed until the 1980s. The growth in plastic packaging use has accelerated at an astonishing pace since the 1970s. The technology available today and the requirements for a non‐perishable nature mean that many previously used materials (e.g. waxed paper) have been replaced by more suitable and economically viable materials such as glass, metal, plastic, paper, and cardboard. Before the 1950s packaging was essentially only used to protect the product during transport and storage. However, with the plethora of newer materials it has also begun to be used to advertise the product with the form, colour, printing, including fonts, and logos being a major part of the marketing process. This is simply because form‐differentiated packaging creates a distinction between the same types of products placed side by side on outlet shelves. The modern practice of favouring plastic as the packaging material of choice is, however, not without significant environmental concerns, with some amount greater than 15 million tonnes being present in the seas in 2017 and possibly as much as 30 million tonnes in 2019 according to recent estimates. The USA and Western European countries in 2000 consumed about 24% each of the world's plastics. Plastics such as PP are thought (based on chemical modelling and accelerated ageing study tests) to be able to persist in landfill for approximately 500 years. Single‐use plastics, which are discarded after one use (incinerated or sent for landfill), accounted for approximately 50% of all plastic packaging in 2019.

Glass‐based packaging is a form of packaging that has stood the test of time. This type of packaging first began to be used around 1500 BCE by artisans in Egypt. Glass, an amorphous silicate matrix, was first used in the form of a pot or vessel. Its fabrication starts when limestone, soda, sand, and silicates are co‐melted and shaped during the fluid phase at a temperature of many hundreds of degrees Celsius and allowed to cool into glass packaging. From about 1200 BCE, pots and containers started to be made from moulded glass on a semi‐commercial basis. Completely transparent glass was invented in the centuries following the development of reproducible blowing and with the aid of a ‘drawing pipe’ by the Phoenicians in 300 BCE. During the two millennia that followed, the development of clear (flint) glass, via augmented glass production techniques, has been incrementally improved and expanded to all manner of products. To date, the development of the automated rotary glass‐manufacturing machine in 1889 affected industrial‐scale glass manufacturing and, therefore, packaging the most of any of these innovations. Surprisingly, given its cost, after the 1970s glass packaging began to be used ubiquitously for the protection of high‐ and low‐value products and to aid the visibility of pack contents. It continues to demonstrate a wide variety of uses today and remains a form of packaging that can be recycled; in the modern era this is an important consideration.

Metal packaging, used in antiquity in the form of gold, silver, and pewter boxes as well as strong alloys such as bronze and brass for coverings and to protect many products, is finding new uses in modern packaging technology. Tin – an essential part of tin‐plated steel, the basis of almost all food cans – became a viable surface treatment following the production of tin in sheet form in Bohemia from 1200. Later, at the beginning of the 1300s, metal cans were first used to store food. These cans were different from those of the modern era but remained an unwritten ‘secret’ until the 1600s. William Underwood aided in the further development of the food can by the development of an improved process for fabricating steel plate. The notions of food cans and of canning were pushed to the forefront of public awareness in 1809 when Napoleon Bonaparte offered a reward of 12 000 French Francs (∼£1000), a huge prize in that period, to any inventor who could develop a method to protect army food supplies during envisioned military excursions and campaigns. The opportunity was seized by Nicolas Appert, a confectioner from Paris (portrayed in Figure 6.4), who presented a selection of pasteurised lidded glass jars, following on from initial investigations. He found that a steel can covered with a fine layer of tin was able to preserve food post heating in an aseptic process and without the can container rusting in the damp. A year later Englishman Peter Durand patented the familiar‐shaped cylindrical can with his coated tinplate as an invention. This development spawned a host of subsequent modifications and adaptations. The first printed box was made in the USA in 1866 but went on to be used for containment of many types of product. Fast‐forwarding to 1910, the tin box was found in commercial environments ubiquitously until the point when aluminium in a suitable form became available. The aluminium foil box was developed in the early part of 1950, and in 1959 the first aluminium can‐based food became available.

In the nineteenth century sharp objects combined with hammers were used to open metal packaging and tin cans, which was a highly unsatisfactory state of affairs. Later on and at least until the middle of the twentieth century, the ‘pig‐stick’ tin can opener – a brutal spear‐looking object, based on a steel spike and sliding blade – was used to open food products. The routine use of the pig‐stick device and the sharp serrated edge it created resulted in many hand injuries. The pivoting can opener was developed by E.J. Warner in 1858, followed by the ‘church key’ of 1892. The pivoting can opener was improved on in 1925 by the Star Can Opener Company, and yet further improved in the now familiar pliers‐form Bunker‐type modern can opener first developed in 1931 by the Bunker Clancy Company. Electric can openers were developed in the late 1950s and the side can opener was developed in the 1980s. Packaging with tear‐open lids was first developed in 1966 and has become increasingly evident in use over the last five decades.

Paper, which is still used universally in the present times, is the oldest conveniently reshaped packaging material available. In ancient Egypt in 5000 BCE, papyrus – a material based on marsh reeds – was used to wrap foods and hold objects together. Many millennia later in China, mulberry tree bark, reconstituted as paper, was used in the first and second centuries BCE to pack food. Paper‐making methodologies and techniques improved during the subsequent 15 centuries. These high‐quality papers and products and technological know‐how were then transferred to the Middle East. From there paper‐making techniques reached Europe, and then from Western Europe they reached England in 1310 and subsequently America in 1609. In 1817 the first commercial cardboard box was produced in England, almost 200 years after being made in a basic and simplistic form in China. The corrugated form of cardboard was invented in the 1850s, gradually replacing wooden boxes in the trade and transportation of goods such as fruit to the point at which, today wooden boxes are barely seen for food products. Selected examples of continuing wooden box or crate use do persist but these are relatively rare. The twentieth century has been the most prominent period for universal paper and cardboard use with the added advantage of recyclability and biodegradability. This is an important consideration since, in the UK in 2013 alone, approximately 750 000 tonnes of household waste, rich in plastic and paperboard materials, went for landfill disposal.