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The dynamic properties of suspensions of rodlike cellulose microcrystallites (whiskers) are investigated using polarized and depolarized dynamic light scattering (DLS, DDLS) and transient electric birefringence (TEB). The whiskers were prepared by controlled sulfuric acid hydrolysis from cotton and tunicate cellulose fibers. Translational (D) and rotational (ϑ) diffusion coefficients in dilute suspensions were measured. For the cotton system, D = 5.5 × 10-8 cm2/s, ϑDDLS = 552 s-1, and ϑTEB = 536 s-1. With the use of Broersma's relations, the rotational and translational diffusion coefficients lead to values of the length L = 255 nm and the cross-section diameter d = 15 nm. For the tunicate-derived whiskers, D = 1.5 × 10-8 cm2/s, ϑDDLS = 11 s-1, and ϑTEB = 14 s-1. These values and Broersma's relations give L = 1160 nm and d = 16 nm. The DDLS and TEB techniques are in good agreement for the rotational diffusion coefficients, especially for the cotton whiskers. These results provide validation for using DDLS...

The interfacial properties of polystyrene/regenerate cellulose fiber composite materials are characterized using micromechanical tests such as the single fiber fragmentation and microbond (“microdrop test”). The cellulose fibers were grafted with different copolymers of different chemical structures as well as different molar masses ranging from 300 to 18,000 (ASA, jeffisocyanate, commercial poly)styrene-co-maleic anhydride and “home-made” poly(styrene-co-TMI). The two polystyrene based copolymers have been shown to be miscible with polystyrene. It was found that the higher improvement of the interfacial shear strength was obtained when the fiber is grafted with the higher molecular weight, i.e., the poly(styrene-co-TMI).

New polymer blends based on cellulose and poly(vinyl pyrrolidone) (PVP) were obtained using a mixture of N=methyl morpholine N-oxide (NMMO) and dimethylsulfoxide (DMSO) as a common solvent system. Materials are obtained after the removing of NMMO-DMSO in three of their different solvents, namely i) H2O, ii) a mixture 95/5 vol/vol hexamethyl phosphororri amide (HMPA) DMSO and iii) a mixture of 95/5 vol/vol dioxan/water.

A series of ten additives were mixed with cellulose solutions in N -methyl morpholine N -oxide (MMNO). Each of these solutions was spun to produce cellulose fibres which were tested for their properties. Most additives had no effect but the addition of NH 4 Cl led to fibres where the tensile strength and modulus had almost doubled when compared to fibres made without additive. Fibres prepared with CaCl 2 were also stronger, but not as much as in the case of NH 4 Cl. Tentative explanations are presented to account for such improvements.

The thermoplastic properties of cellulose solutions in tertiary amine oxides have been used for the elaboration of a new spinning system where post-stretching is possible. This is achieved at a temperature slightly above the Tg of the solution, i.e. when the relaxation of the cellulose chains is restricted. Preliminary results indicate that this new process may prove to be an attractive route to the production of cellulosic fibers with enhanced mechanical properties.