Matrix spiders
The matrix spinning is a process for preparing PTFE - fibers . This is generally a type of wet spinning process , specifically a modified viscose process . Due to the characteristic brown color caused by the spinning process , such PTFE fibers are often referred to as brown PTFE .
In the production of PTFE fibers, there is the difficulty that pure PTFE is not suitable for the melt spinning process due to its high melt viscosity and not suitable for the wet spinning process due to its resistance to solvents .
In matrix spinning, an aqueous PTFE dispersion is mixed with a viscose spinning mass in a ratio of 3: 1 to 24: 1 - based on the masses of PTFE and viscose - and pressed ( spun ) through spinnerets into an acidic spinning bath . Strictly speaking, no PTFE fibers are produced in this step, but viscose fibers in a wet spinning process. The viscose serves as a matrix for the PTFE ( bicomponent fiber) embedded in the fiber . However, these fibers only have a low tensile strength and also do not have the desired chemical properties of pure PTFE. Therefore, in a further processing step by heating the fibers to temperatures above the melting point of PTFE, on the one hand the PTFE is sintered , on the other hand the matrix of viscose decomposes, whereby a PTFE fiber with a low proportion of degradation products of the viscose is created. These degradation products ensure the characteristic brown color of the fiber. In addition to heating, the fiber is stretched (ie elongated by the application of tensile stress ), which together with the sintering of the PTFE leads to an increase in the strength of the fiber.
See also
literature
Hans-Karl Rouette: Handbook textile finishing . 15th edition. Deutscher Fachverlag, 2006, ISBN 3-86641-012-3 , Volume 1, Chapter 2.1.1.5.4, p. 76 f .