11:30 AM - SF03.04.04
Cottonid—A New Old Paper-Based Material System
Matthias Langhansl1,Ronja Scholz2,Frank Walther2,Cordt Zollfrank1
Technische Universität München1,Technische Universität Dortmund2
Cottonid, vulcanized fiber and leather stone - many names exist for one of the oldest known plastics. In 1859, the Englishman Thomas Taylor described for the first time the production of this material on the basis of rag paper, which he produced by soaking cellulose fibers in a zinc chloride bath and pressing several layers under heat. Nowadays, unsized specialty paper made from cotton, pulp or a mixture of both serves as a renewable raw material for industrial production. Chemically, Taylor described the parchmentization of cellulose fibers.
The treatment with zinc dichloride may only last until the fibers have reacted superficially, otherwise the cellulose chains are degraded and the material is damaged. The exact mechanism of parchmentization has not yet been identified in detail. During the process a tremendous swelling can be observed followed by the decomposition of the paper sheet. The result of this conversion process of the cellulose fibers is a considerable change in the material properties, from soft and flexible to horn-like and hard.
The manufacturing process and the material itself is very sustainable. The zinc dichloride, used as a catalyst, can be completely recycled. The washing water is also almost completely reused. The finished material is free from chemical residues and consists only of cellulose and, for marketing purposes in some cases, pigments. Also zinc dichloride is a cost effective and a safe “solvent” compared to commonly used for dissolving cellulose. The industrial manufacturing process is established and optimized for more than 100 years in terms of energy- and resource efficiency.
In this context, the presented talk will provide an overview of the fundamental changes of the cellulose, the resulting customizable properties of Cottonid and its possible applications. Almost all properties of the material can be tuned. Through variation of the parchmentizing process, it is possible to set the crystallinity of the material. With this in mind, we can set the mechanical properties, hygroscopicity, optical properties, electrical properties and even the duration of the biodegradation. The process-structure-property relationship of the resulting material is characterized by infrared spectroscopy, differential scanning calorimetry and x-ray diffraction. In addition, structural properties after manufacturing are analyzed by scanning electron microscopy.
Cottonid can be used for almost every suitable application from packaging to autonomous actuation devices. Due to the adjustable hygroscopicity and the associated swelling, Cottonid can also be used as a functional material. It can work as a humidity sensing actuator as the active layer in a bilayered composite. Because of its good resistance against chemicals, grease and oil, a possible application in the packaging industry can lead to a further development of the material. Furthermore, Cottonid can be joined and machined similar to wood. Cottonid fiber is currently used as a support material for grinding wheels due to its toughness and because of its spark-quenching properties for welding helmets. The oldest use is as a sealing material in the water pipe technology.
In summary, Cottonid is a promising material in the field of biological and sustainable materials. Due to the topicality of the issues of environmental protection and sustainability, these materials are experiencing a renaissance. It has great potential to replace conventional petroleum-based materials as a green alternative. Additionally, the reaction route via zinc dichloride can be transferred to the wide area of all cellulose composites and might lead to a new, more sustainable way for their fabrication.