Читать книгу Packaging Technology and Engineering - Dipak Kumar Sarker - Страница 25

Paper at first appears to be a simple material but this is an underestimation of a complex polymeric resource that has a colourful and extensive history, with the material undergoing many processing revisions and refinements across the centuries. The first paper was constructed from woven and intertwined papyrus reeds and this even pre‐dates the well‐known originators of wood‐pulp paper in north‐eastern China. The process of making 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.