Polymer-pyrolysis derived fibers

Polymer Pyrolysis Derived SiC Fibers (PP-fibers) As shown 1976 by Yajima [54], pSiC fibers with a smaller diameter (8-30 pm) and without a central core can be manufactured by solid state pyrolysis of a polycarbosilane (PCS) precursor fiber. The melt-spun PCS fiber is first cured at 200°C in air to produce a thin layer to protect from melting later on, then heated up in inert atmosphere to 1500°C to convert the PCS in crystalline pSiC. The steps leading to the production of SiC can be summarized as follows ... 

Polymer Pyrolysis-Derived Silicon Carbide Fibers (PP-Fibers) As shown in 1976 by Yajima [76], P-SiC fibers with a smaller diameter (8-30 pm) and without a central core can be manufactured by the solid-state pyrolysis of a PCS precursor fiber. 

The effects of decomposition of polymer-derived fibers in long-term service in inert or reducing conditions can be simulated by long-term exposure to such environments at temperatures above the pyrolysis condition. 

Carbon molecular sieve membranes. Molecular sieve carbons can be produced by controlled pyrolysis of selected polymers as mentioned in 3.2.7 Pyrolysis. Carbon molecular sieves with a mean pore diameter from 025 to 1 nm are known to have high separation selectivities for molecules differing by as little as 0.02 nm in critical dimensions. Besides the separation properties, these amorphous materials with more or less regular pore structures may also provide catalytic properties. Carbon molecular sieve membranes in sheet and hollow fiber (with a fiber outer diameter of 5 pm to 1 mm) forms can be derived from cellulose and its derivatives, certain acrylics, peach-tar mesophase or certain thermosetting polymers such as phenolic resins and oxidized polyacrylonitrile by pyrolysis in an inert atmosphere [Koresh and Soffer, 1983 Soffer et al., 1987 Murphy, 1988]. 

Itaconic acid was isolated in 1836 from the pyrolysis products of citric acid (7) and the pol3mierization of the ethyl ester was observed by SwAETS in 1873 (2). While many patents relating to the acid and its esters as monomers have issued since that time, only recently have reports begun to appear in the scientific journals. The voluminous patent literature describes the use of polymeric itaconic acid derivatives in such applications as protective and decorative coatings, synthetic fibers, oil additives and rigid plastics as well as many others. Several summaries of the patent art and present commercial applications are available (3). Such information has been omitted from this review, which is directed primarily toward chemical behavior of the itaconic monomers and polymers. 

The evolution of CH4 during the pyrolysis step and the empirical formulas of pyrolyzed fibers suggest that carbon is only partly present in the backbone of the polymer (assuming that CH4 is formed from pendent methyl groups). Finally, the N/Si ratio in PCSZ based fibers, i.e. 0.46-0.49, is lower than that, 0.90-1.00, in the fibers derived from PSZ. 

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