X-ray Studies of Crystallite Orientation in Cellulose Fibers. II. Synthetic Fibers from'Bacterial Cellulose Membranes

Abstract

As partial proof for the conclusions drawn in a previous paper (13), x-ray diagrams of natural fibers were compared with those of fibers synthesized from bacterial cellulose membranes. During the preparation of these "synthetic fibers," certain interesting observations regarding the plastic behavior of the crystallite suggested a further study of the type and degree relationship between deformation and orientation. It is the purpose of the present paper to describe briefly this extended investigation and especially to point out the significance of the results in that they appear to throw additional light on the question raised in the earlier paper (13), namely, what is the nature of the crystallite? Further information in this connection is not only of theoretical interest but also of practical importance, especially in the production of regenerated cellulose sheets and fibers.Aside from a study of the characteristics of cellulose fiber diagrams themselves-a critical review of which has been given elsewhere (14)-one of the useful methods of investigating the configuration of the crystallite is to observe with x-rays its plastic behavior. Unfortunately, owing to the existence of a complex, ever varying, cylindrical cell wall, harboring numerous non-cellulosic materials, it is extremely difficult t o draw definite conclusions when the method is applied to natural fibers. Although bacterial cellulose membranes have little macroscopic resemblance to natural fibers, they offer a unique opportunity for studying certain fundamental problems relating to the fine structure of natural cellulose for the following reasons : (1) they possess a well-formed, natural cellulose, crystalline structure; (2) they exist ~1 8 a uniform membrane in a highly swollen or gel condition; (3) plastic flow can be readily produced in the 1

More Than Meets the Eye in Bacterial Cellulose: Biosynthesis, Bioprocessing, and Applications in Advanced Fiber Composites

“…Bacterial cellulose membranes were described by Sisson as being “tough dense parchments, very resistant to the penetration of liquids.” So it comes as no surprise that it is the mechanical properties of BC, which attracted significant attention and numerous efforts have been poured into the research and development of BC for various applications. These include biomedical applications, the production of high quality papers, diaphragms for electroacoustic transducers, optically transparent films, stabilizers for emulsions and foams, and reinforcement for fine structures, such as fibers, polymer foams, and the matrices of composites .…”

“…Bacterial cellulose is predominantly left‐hand twisted, produced as nanofibers naturally with individual fibers ranging from 25 to 100 nm in diameter and several micrometers in length . Moreover, the randomly aligned BC nanofibers in as produced BC membranes can be easily orientated uniaxially or uniplanar if a stress is applied to the membrane during drying . When still wet, as produced BC pellicles can easily be disintegrated into loose nanofibrils.…”

“…A few plausible hypotheses have been put forward: i) to maintain close proximity to the surface of the culture medium where the oxygen concentration is highest, [3] ii) to protect against ultraviolet light, [4] and iii) to protect against heavy metal ions and improve nutrient transport by diffusion. [5] Bacterial cellulose membranes were described by Sisson [6] as being ''tough dense parchments, very resistant to the penetration of liquids.'' So it comes as no surprise that it is the mechanical properties of BC, which attracted significant attention and numerous efforts have been poured into the research and development of BC for various applications.…”

“…[5,24] Moreover, the randomly aligned BC nanofibers in as produced BC membranes can be easily orientated uniaxially or uniplanar if a stress is applied to the membrane during drying. [6] When still wet, as produced BC pellicles can easily be disintegrated into loose nanofibrils. This makes BC different from plantderived micro-or nanofibrillated cellulose, which has to be produced by homogenization or fibrillation of cellulosic plant biomass to obtain cellulose with nanometer dimensions.…”

X-ray texture investigations of bacterial cellulose

“…Both with regard to the principles of structure formation and the mechanical properties of a high-tech bacterial cellulose material, the orientational state plays an important role. Based on X-ray investigations of several cellulosic materials, Sisson [8] defined the possible orientational states of polymers in general, introducing designations slightly revised later by Heffelfinger and Burton. [9] Takai et al [10] demonstrated that membranes of bacterial cellulose exhibit basically a uniplanar orientation and an additional axial orientational component depending on the drying procedure.…”