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

Mechanical properties (tensile strength and modulus) of Chitin Whiskers fibre-reinforced poly(acrylic acid) with different fibre loading and different gauge lengths are compared with theories of reinforcement. The addition of random oriented Chitin Whiskers to poly(acrylic acid) matrix increased in tensile strength and elastic modulus of the composite. There was a steady increase in tensile stress and Elastic modulus within the volume fraction range investigated. The properties of the composite at different gauge lengths were studied. Within the same volume fraction, the tensile stress decreases as the gauge length increases. It is the reverse for the Elastic Modulus. Irrespective of filler loading and the theoretical modelling equations the tensile stress can be predicted at 40 mm gauge length. For the Elastic Modulus, the prediction of the property varies within the gauge lengths investigated. At higher filler loading, a smaller gauge length is required to predict the Elastic modulus. The comparative study between the tensile stresses obtained by experiment and selected theoretical models showed that the Parallel and Series models of the Rule of Mixture produced more accurate prediction, followed by Halpin-Tsai and modified Halpin-Tsai models. Guth's model was the least as the percentage deviation from the experimental data was very high when predicting the Elastic modulus. The density of the nanocomposite films were 1.08g/cm3, 1.023, and 1.024g/cm3 respectively, for 3%, 6%, and 9% weight filler and were in agreement with the theoretical data.