The pH can also have an important effect upon charge density and therefore upon adsorption. The Chemistry of Paper provides an overview of the process of making paper from a chemical perspective. The production process itself is also highly sophisticated, involving what is in essence a high-speed filtration process yielding a weak wet fibrous network. Non-woody fibre, although relatively small in volume is nevertheless important, particularly in the developing world where the use of indigenous raw materials can substantially reduce the amount of foreign exchange spent on importing costly wood pulp. It is very important for us that all real regarding J. Both hardwoods and softwoods are used for making paper and they have very different fibre morphologies and thus very different paper-making properties.
This book is an informative and entertaining overview for students and others who require an introduction to the chemistry of paper manufacture. I would also like to thank Professor Kit Dodson University of Toronto , Dr. This is not simply residual material left from incomplete washing although there may be some because it is found even in well-washed pulps, but it is the result of the mechanical forces of refining. I t is derived from plant sources and therefore has both morphological complexity and physical and chemical complexity. For the purpose of this text therefore, paper will be defined in1 2 Chapter 1 terms of its method of production, that is a sheet material made up of a network of natural cellulosic fibres which have been deposited from an aqueous suspension. This opening chapter is a brief introduction to the nature of paper, its history and to its modern day use. Most of the newly introduced fibre will also probably continue to be derived from wood, although annual crops can be expected to play an increasingly important role.
The manufacture of paper involves a large amount of chemistry, including carbohydrate chemistry, pigments and resins and colloid and surface chemistry, as well as elements of environmental and analytical chemistry. I t is usually measured by polyelectrolyte colloid titration, which has been discussed earlier in this chapter, and the result expressed as a mole percent of charged groups or as equivalents or milliequivalents per unit mass. Non-woody plants can also be harvested relatively quickly- usually one or two years after planting-whereas trees require ten to twenty years to reach sufficient maturity. It is necessary for k l to be much larger than k2 which is usually the case for polyelectrolytes. Over 80% of the wood for all industrial uses comes from the forests of North America, Europe and what was formerly the Soviet Union. .
For example, the polyethyleneimines are more strongly adsorbed at pH 7 than at pH 4. The book explores several chemical processes involved in the production of paper: the delignification of the wood fibres performed at elevated temperature and pressure, the bleaching of the cellulose-rich pulp using environmentally-friendly systems, the formation of the pulp into sheets of fibres strengthened by extensive inter-fibre hydrogen bonding, and finally the coating of the sheets in a manner appropriate to their end use. Dissolution from Pulps and FibresDuring refining, soluble substances are dissolved from pulps to the extent of about 2-5% by weight of the pulp, but in some cases this may be higher. Reycled fibre usage million tonnes Recycledjbre usage Yo ~~ Year World pulp World paper and production from board consumption virgin fibre million tonnes million tonnes 1992 1991 1990 1989 1988 1987 1983 1978 163. T o avoid frequent breaks, and to obtain good product uniformity therefore requires some of the most advanced control engineering technology available today. Paper is generally made either from logs that are unsuitable for sawing or peeling or from residues arising from these processes. The book explores several chemical processes involved in the production of paper: the delignification of the wood fibres performed at elevated temperature and pressure, the bleaching of the cellulose-rich pulp using environmentally-friendly systems, the formation of the pulp into sheets of fibres strengthened by extensive inter-fibre hydrogen bonding, and finally the coating of the sheets in a manner appropriate to their end use.
Goethals, Pergamon Press, Oxford, 1980, p. However, particle size is much more important than particle shape in influencing the numbers of particles per unit mass. Its achievement then was to collect the considerable advances in understanding which had been made in the chemistry of papermaking in previous years, and provide, for the first time, a sound physico chemical basis of the subject. Because of the need to obtain specific characteristics in the final product, for example water absorbency or wet strength, there is a great difference in the chemistry and method of production of these grades. Note: For a disc-shaped particle the aspect ratio is the ratio o disc diameter:disk thickness and f o r a f rod-shaped particle it is the ratio of rod length: rod diameter.
The Chemistry Of Paper Roberts J C can be very useful guide, and the chemistry of paper roberts j c play an important role in your products. A great deal of chemistry is involved in this formation process, especially as it is often necessary for the sheet to be modified in order to give it properties which are appropriate to its end use. This book is an informative and entertaining overview for students and others who require an introduction to the chemistry of paper manufacture. The manufacture of paper involves a large amount of chemistry, including carbohydrate chemistry, pigments and resins and colloid and surface chemistry, as well as elements of environmental and analytical chemistry. It is the subject of what papermakers call wet-end chemistry. The techniques used to determine furnish charge are usually one of those described below.
This may not always be easy to determine for complex co-polymers with no clearly defined repeat unit. It is common to use highly charged cationic polyelectrolytes as a pretreatment to reduce the anionicity of the system. Providing an overview of the making of paper from a chemical perspective, this book deals with both the chemistry of paper as a material and the chemistry of its production. Mit dem amazon-Kindle ist es aber nicht kompatibel. A breakdown of world fibre usage is given in Table 1. However, as it is the colloidal fraction which requires to be flocculated to assist retention during drainage, it is still a useful measurement.
The characteristics of hardwood and softwood fibres are discussed at greater length in Chapter 2. The solid phase is then separated and the residual polyelectrolyte in the filtrate is backtitrated: Fibre or filler Filtrate +C-+ -+ Filtrate +A Complex From a knowledge of the stoichiometry of the reaction between A and C, the charge of the furnish can be determined. The component fibres are finally formed from a wet suspension into a bonded network sheet structure whose mechanical strength is provided by both the fibres themselves and by extensive inter-fibre hydrogen bonding. The titration relies upon the formation of a 1:l complex, which is generally true provided that the ionic strength is low. The charge density, which is also known as cationicity or anionicity depending upon the sign of the charge, is the ratio of the charged groups to the total number of repeat units in the polymer.
The important chemistry involved in this process is firstly the retention of col loidal material during filtration and secondly the modification of fibre and sheet properties so as to widen the scope for the use of paper and board products. Aqueous and Solvent Coatings L. The E-mail message field is required. The method can be applied to charges of solids such as fibres and fillers by equilibrating a known excess of cationic polyelectrolyte for anionic paper furnishes with the furnish. This causes a potential difference to be established across the plug the streaming potential V s. Approximately two thirds of this is either sawn or peeled.
Reviews of the The Chemistry of Paper So far about the book we've got The Chemistry of Paper comments consumers haven't however remaining their report on the sport, you aren't read it nevertheless. This new edition has been thoroughly updated with much new material added. However nothing could be further from the truth. Providing an overview of the making of paper from a chemical perspective, this book deals with both the chemistry of paper as a material and the chemistry of its production. The pulp is then often bleached, and the chemistry of this process has changed considerably over the past decade because of the adverse environmental impact of chlorine-based bleaching systems. Roberts, Blackie, Glasgow, 1992, pp. Neither does the book deal with the chemistry of pulp preparation from wood, from other plant sources or from recycled fibres , for there are also many excellent texts on this subject.