This paper provides a review of cellulose, sources, extraction, molecular structure, cellulose whiskers, preparations, and morphology. The mechanical and thermal properties of cellulose reinforced composites are also discussed. Detail structure of Nano whiskers is also reported. As a renewable biomaterial, the most common source of cellulose is the plant. These plants include fruit fibers (coir), seed fibers (cotton), wood, leaf fibers (sisal), bast fibers (jute, kenaf, and hemp). Other sources of cellulose are from micro-organisms such as fungi, tunicates, bacteria, and algae. Cellulose whiskers are isolated from cellulose fibers by acid hydrolysis. Cellulose micro fibril structures are made of both amorphous and crystalline regions. The amorphous regions are vulnerable to hydrolysis by acids compared to the crystalline domains. Several techniques among which are Field Emission Scanning Electron Microscopy (FESEM), Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) have been used to study the morphology of cellulose whiskers. An interface between cellulose whisker and matrix is a transition zone between the matrix and the cellulose whiskers. It plays an important role in the overall mechanical properties of the composites. A soft interface domain will yield a greater resistance to fracture, while the composite will be low in stiffness and strength. On the other hand, a stiffer interface domain may cause the composite to be strong and stiff and less resistant to fracture. The addition of CW into polymers matrices has little or no effect on the glass transition temperature, (Tg) except on the modification of CW. Keywords: Cellulose, whiskers, mechanical, thermal, properties, biomaterials

This paper provides a review of chitin, sources, extraction, uses, applications, chitin whiskers and it preparations and the mechanical and thermal properties of chitin reinforced composites. Also reported here is the properties of CaCO3/chitin whiskers reinforced composites. Chitin can be extracted from shrimps, crabs cell walls, yeast and green algae or from Riftia tubes with a percentage varying between 20 to 40% depending on the source. Despite the denaturing of chitin, the most widely used method of extractiong chitin from seashells is the chemical method. Chitin whiskers known by different name in literature can only be prepared by using hydrochloric acid. The rod-like particles of chitin whiskers have an average lengths and widths of 200 ± 20 nm and 8 ± 1 nm respectively or more depending on the source of chitin. Chitin whiskers reinforced composites have greatly improved the mechanical and thermal properties of the composites especially at lower filler loading. The improved properties are attributed to effective stress transfer. http://dx.doi.org/10.4314/njt.v36i1.9