Method and apparatus for producing high modulus bixial fabric
AssigneeHitco
InventorsRichard J. Larsen, Robert W. Mitchell
Life of this patent
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Abstract
The transverse properties of high modulus fabric such as graphite are significantly improved by continuously processing the material through a multiple roller unit under warp tension while restraining fill shrinkage by wrapping the material no less than 180.degree. around each roll and by minimizing unrestrained inter-roll travel by controlling the inter-roll span. Graphite precursor fabrics such as polyacrylonitrile (PAN) can be stretched as high as 45% in the warp direction with as little as 1-2% shrinkage in the fill direction. The invention also relates to simultaneous stretching and preoxidation of the precursor fabric under tension and while minimizing fill shrinkage.
Claims10
A continuous and dynamic method for developing high biaxial modulus in a woven graphite precursor fabric comprising the steps of:
- 1. stretching the fabric while heating the fabric to a temperature of at least 175.degree.F;
- 2. preoxidizing the fabric by heating the fabric to a temperature of at least 400.degree.F and applying an oxidizing atmosphere to the fabric, steps (1) and (2) being conducted while simultaneously applying a warp tension of at least 5 pounds per inch up to the breaking strength of the fabric to the fabric;
- and
- passing the tensioned fabric around at least 180.degree. of the alternate upper and lower surfaces of at least two closely spaced rolls, the tangential distance between said rolls being no more than 12 inches and stretching said fabric in the warp direction up to 50% while restraining fill shrinkage to no more than 2%.
An apparatus for continuously processing graphite precursor fabric;
- at least two rolls arranged to receive said fabric wrapped over at least 180.degree. of the alternate upper and lower surfaces of adjacent rolls;
- roll support means disposed to support the adjacent rolls such that the tangential distance between adjacent rolls is no more than 12 inches;
- means to tension the wrapped fabric from at least 5 pounds per inch to below breaking strength to stretch the fabric in the warp direction up to 50% while restraining fill shrinkage to no more than 2%;
- means for applying an oxidizing atmosphere to the tensioned heated fabric.
Dependencies are inferred from the claim text.