1. 1 Nazmul Ehsan, Southeast University

2. 2 Nazmul Ehsan, Southeast University 3. 3 Nazmul Ehsan, Southeast University 4. 4 Nazmul Ehsan, Southeast University 5. 5 Nazmul Ehsan, Southeast University 6. 6 Nazmul Ehsan, Southeast University 7. 7 Nazmul Ehsan, Southeast University 8. 8 Nazmul Ehsan, Southeast University 9. Cuticle 9Nazmul Ehsan, Southeast University 10. 10 Nazmul Ehsan, Southeast University 11. The cortex the internal cells - make up 90% of the fibre. There are 2 main types of cortical cells ortho-cortical and para-cortical. Each has a different chemical composition These two types of cells form in two distinct halves.The cells expand differently when they absorb moisture, making the fibre bend - this creates the crimp in wool 11 Nazmul Ehsan, Southeast University 12. 12 Nazmul Ehsan, Southeast University 13. The cortical cells are surrounded and held together by a cell membrane complex The cell membrane complex contains proteins and waxy lipids and runs through the whole fibre. The cell membrane complex allows easy uptake of dye molecules. 13 Nazmul Ehsan, Southeast University 14. 14 Nazmul Ehsan, Southeast University 15. Inside the cortical cells are long filaments called macro fibrils. These are made up of bundles of even finer filaments called microfibrils, which are surrounded by a matrix region. 15 Nazmul Ehsan, Southeast University 16. 16 Nazmul Ehsan, Southeast University 17. The matrix consists of high sulphur proteins.This makes wool absorbent because sulphur atoms attract water molecules. Wool can absorb up to 30% of its weight in water and can also absorb and retain large amounts of dye. This region is also responsible for wools fire-resistance and anti-static properties. 17 Nazmul Ehsan, Southeast University 18. 18 Nazmul Ehsan, Southeast University 19. Within the matrix area, there are embedded smaller units called microfibrils. The microfibrils in the matrix are rather like the steel rods embedded in reinforced concrete to give strength and flexibility. The microfibrils contain pairs of twisted molecular chains. 19 Nazmul Ehsan, Southeast University 20. 20 Nazmul Ehsan, Southeast University 21. Within the twisted molecular chains are protein chains that are coiled in a helical shape much like a spring. The helical coil the smallest part of the fibre gives wool its flexibility, elasticity and resilience, which helps wool fabric keep its shape and remain wrinkle-free in use. 21 Nazmul Ehsan, Southeast University 22. 22 Nazmul Ehsan, Southeast University