Cellulose pulp reinforcement mechanical properties

Zimmermann et al. [134] have used cellulose fibrils obtained from sulphite wood pulp to reinforce water soluble polymers such as polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC). The mechanical properties of these nanocomposites were measured by tensile tests showing that the addition of fibrils increase the modulus of elasticity (E) up to three times and the tensile strength up to five times compared to the raw polymer. Zimmermann et al. [135] have determined the E values and the hardness of cellulose/HPC nanocomposites using nanoindentation technique. The results showed that the E values measured by nanoindentation were from two to three times higher than the E values measured by means of tensile tests. Stauss et al. [136] have explained that differences between tensile test and indentation results are due to the fact that they do not test the same material volumes and regions. The large volume used in tensile test includes defects such as pores, cracks and impurities. 

Cellulosic materials, such as cotton and wood pulp, when subjected to acid hydrolysis yield defect-free, rod-like crystalline residues called as cellulose nanocrystals. These are often referred to as microcrystals, whiskers, nanocrystals, nanoparticles, microcrystallites, or nanofibres. Their nanoscale dimension, high surface area, high specific strength, thermal, and mechanical strength along with gas barrier properties increase its merit towards its usage in advanced applications like reinforcement in polymeric matrix to form nanocomposite materials, chemical transformations and so on. 

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