Product Design

Product Design

1. Paper and Board

   • produced primarily from hard and softwoods
     • sometimes,cotton,straw and hemp are used which produced papers with different properties

2. wood is made up of cellulose fibres that are bounded together by lignin

   • to produce paper ,these fibres needed to be separated to form a mass of individual fibres called WOOD PULP.
     • Softwood fibres are longer and offer greater strength.
     • Hardwood fibres are shorter offering a smoother, opaque finish.
     • wood pulp is produced by three methods
       • mechanical
         • Logs of coniferous trees are SATURATED WITH WATER and DE-BARKED. The wood is grounded down which SOFTENS THE LIGNIN. The mechanised forces SEPARATE THE FIBRE to form 'ground wood' pulp. Larger pieces are re-circulated for additional screening. The resulting pulp can be used for LOW-GRADE PAPER such as newspaper so the pulp is bleached, with PEROXIDE and SODIUM HYROXIDE.
           • This is the most widely used method in the UK
       • chemical
         • after DE-BARKING, the hard and softwood logs are cut into 2cm chips ALONG THE GRAIN.These are pounded into FRAGMENTS and SCREENED.The resulting pulp is stored and treated with either an ACID or an ALKALI to break down the LIGNIN.Most chemical pulp is made by ALKALINE KRAFT PROCESS or SULPHATE to 'cook' the wood pulp. The amount of fibre produced is LOWER than with MECHANICAL METHODS,but the fibres are LONGER,STRONGER and contain fewer IMPURITIES.
       • waste
         • Recycled paper and board used for waste pulp is often used for LOWER GRADES of paper as its STRENGTH,DURABILITY and COLOUR are NOT AS GOOD as virgin fibres (those produced using mechanical and chemical methods).
           • Waste pulp is often mixed with virgin fibres to produce BETTER QUALITY PAPER as FIBRES become SHORTER,WEAKER and LOSE THEIR PAPERMAKING QUALITIES.
             • manufacturers blending a variety of pulps and process them along with bonding agents and coloured pigments