Biomedical subjects

Lennart Salmén

Publications and source records attributed to Lennart Salmén.

5 recordsLinked to original sources

PubMed2004

The association of water to cellulose and hemicellulose in paper examined by FTIR spectroscopy.

The nature of water sorption to different materials has always been a complex matter to address, partly due to the different possibilities of hydrogen-bond formation. For cellulosic materials this is extremely important for its product performance. In order to gain a deeper understanding of the moisture adsorption mechanisms of cellulose and hemicelluloses, the molecular interaction between moisture and paper and between moisture and some wood polymers was studied using FTIR spectroscopy under stable humid conditions. It was found that all the moisture-sorbing sites adsorbed moisture to the same relative degree, and that the rate of adsorption was the same for all these sites. It was also noticed that the moisture is adsorbed in the form of clusters. A direct relationship was found between the moisture weight gain and the increase in the absorbance peaks for humidities up to 50% relative humidity after which the moisture gain increased faster, a fact that still remains to be explained.

Adsorption↗

PubMed2004

Characterization of the crystalline structure of cellulose using static and dynamic FT-IR spectroscopy.

The cellulose structure is a factor of major importance for the strength properties of wood pulp fibers. The ability to characterize small differences in the crystalline structures of cellulose from fibers of different origins is thus highly important. In this work, dynamic FT-IR spectroscopy has been further explored as a method sensitive to cellulose structure variations. Using a model system of two different celluloses, the relation between spectral information and the relative cellulose Ialpha content was investigated. This relation was then used to determine the relative cellulose Ialpha content in different pulps. The estimated cellulose I allomorph compositions were found to be reasonable for both unbleached and bleached chemical pulps. In addition, it was found that the dynamic FT-IR spectroscopy technique had the potential to indicate possible correlation field splitting peaks of cellulose Ibeta.

Cellulose↗

PubMedDate not supplied

Micromechanical understanding of the cell-wall structure.

For improving properties of pulp fibres, a better understanding of the relationships between its macroscopic mechanical properties, fibre ultrastructure, and properties of the wood polymers is important. This paper discusses such relations between elastic properties of fibres, their matrix structure and the wood polymer elastic constants. It is argued that an orientation of all of the wood polymers in the direction of the cellulose microfibrils is most likely. The elastic longitudinal modulus of cellulose is well described by the value of 134 GPa dominating the longitudinal fibre properties. In the transverse direction the amorphous polymers play a more important role.

Biomechanical Phenomena↗

PubMedDate not supplied

Load distribution in native cellulose.

The properties of cellulose materials are dependent on interactions between and within the cellulose chains. To investigate the deformation behavior of cellulose and its relation to molecular straining, sheets with fibers oriented preferably in one direction were studied by dynamic FT-IR spectroscopy. Celluloses with different origins (spruce pulp, Cladophora cellulose, cotton linters) were used. The sheets were stretched sinusoidally at low strains and small amplitudes while being irradiated with polarized infrared radiation. The cellulose fibers showed mainly an elastic response. The cellulose fibers showed mainly an elastic response. The glucose rings and the C-O-C bridges connecting adjacent rings, as well as the O(3)H.O(5) intramolecular hydrogen bonds are the components mainly deformed under stress, whereas the O(2)H.O(6) intramolecular hydrogen bonds play a minor role. The load distribution was also found to be different in the different allomorphic forms of cellulose I, namely, I(alpha) and I(beta).

Biomechanical Phenomena↗

PubMedDate not supplied

Pore and matrix distribution in the fiber wall revealed by atomic force microscopy and image analysis.

A method for the ultrastructural investigation of fiber cross-sections based on atomic force microscopy in combination with image analysis is presented. A uniform distribution of pores across the matrix material within the fiber wall was revealed by impregnation of pulp fibers with poly(ethylene glycol). The effects of chemical and mechanical processing on the pore and matrix structure and on the arrangement of the cellulose fibril aggregates were investigated. During chemical processing, changes in the fiber ultrastructure occur: a broadening of the pore and matrix lamella widths in combination with a reduction in their number and an enlargement of the cellulose fibril aggregates. It was found that pores formed during pulping are evenly distributed across the fiber wall in the transverse direction. In contrast, refining increases the pore and matrix lamella width in the fiber wall closest to the middle lamella an effect which gradually decrease in size toward the lumen side.

Cell Wall↗