E.i. Dupont De Nemours and Company

Other

Richard L Provost

Gary Lee Hendren

Leland A Taylor

Kim L Fried

A process for making a high heat resistant oil-impregnatable insulating board, having a dielectric constant less than 2.7, made from bleached polytetrafluoroethylene floc and aromatic polyamide fibrids and the resulting insulating board are disclosed.

High heat resistant oil-impregnatable electrical insulating board

High temperature resistant pressboard having a desirable combination of compression set values and oil absorption is prepared by a process whereby a low density pressboard is first prepared by forming a wet lap of multiple layers of a waterleaf containing 50-95% by weight water and pressing the wet lap at 100-200.degree. C. under a pressure of 10-60 kg/cm.sup.2, drying, ultimately at 270.degree.-320.degree. C. until substantially no further moisture is evolved and finally pressing at 270.degree.-320.degree. C. under a pressure of 8-350 kg/cm.sup.2 and optionally cooling under restraint.

Pressboard and process for its preparation

An aqueous slurry of 0.2 to 2.0 weight percent aramid fibrids and aramid floc in a weight ratio of 0.25 to 20, respectively, is refined in a disc refiner having grooved facing plates with surface dams, the distance between the facing plates being 0.20 to 1.0 mm.

Co-refining of aramid fibrids and floc

High strength, high modulus aromatic polyamide fibers are dyed by crimping the fibers while wet to at least 10 crimps per inch and maintaining at least 15% by weight moisture based on the dry fibers in the fibers at all times before dyeing.

Growing community of inventors

Midlothian, VA, United States of America

Richard L Provost