{
  "patent_number": "US 3819587",
  "country": "US",
  "title": "The Molecular Structure of Kevlar High-Strength Fiber",
  "original_title": "Wholly aromatic carbocyclic polycarbonamide fiber having orientation angle of less than about 45{20",
  "summary": "Stephanie Kwolek's 1971 patent for DuPont describing the molecular alignment and manufacturing of extremely strong, lightweight synthetic aramid fibers, which became famous as Kevlar.",
  "what_it_does": "This patent claims a synthetic fiber made from aromatic polyamides (aramids) where the polymer chains are highly aligned. Specifically, the chain-extending bonds from each aromatic ring are coaxial or parallel and oppositely directed (para-oriented). This alignment is characterized by an 'orientation angle' of less than 45 degrees, meaning the polymer chains lie nearly parallel to the fiber axis. This tight alignment gives the fiber incredible tensile strength (tenacity of at least 5 grams per denier) and stiffness (initial modulus of at least 300 grams per denier). When spun from a liquid crystalline solution, the molecules line up like logs in a river, creating a fiber that is five times stronger than steel on an equal-weight basis.",
  "what_it_does_not_cover": [
    "Does not cover aliphatic polyamides like nylon, where the carbon chains are flexible and do not contain rigid aromatic rings.",
    "Does not cover fibers with a high orientation angle (above 45 degrees), where the polymer chains are disorganized and lack high tensile strength.",
    "Does not cover meta-oriented aramid fibers (like Nomex) where the chain bonds are not coaxial or parallel, resulting in lower strength but high heat resistance.",
    "Does not cover inorganic high-strength fibers such as carbon fiber or glass fiber."
  ],
  "filed": "1971-09-07",
  "granted": "1974-06-25",
  "expires": "1991-09-07",
  "status": "expired",
  "holder": "EI Du Pont de Nemours and Co",
  "holder_url": "https://patentbrief.org/company/ei-du-pont-de-nemours-and-co",
  "inventors": [
    {
      "name": "S Kwoleck",
      "url": "https://patentbrief.org/inventor/s-kwoleck"
    }
  ],
  "times_cited": 141,
  "tags": [
    "materials",
    "aerospace",
    "automotive"
  ],
  "abstract": "Fibers of unique internal structure (evidenced by low orientation angle and/or high sonic velocity) and exceptionally high tensile properties (e.g., initial modulus) are prepared from spinning dopes of selected carbocyclic aromatic polyamides in suitable liquid media.",
  "url": "https://patentbrief.org/patent/us/3819587/kevlar-aramid-fiber-kwolek",
  "markdown_url": "https://patentbrief.org/patent/us/3819587/kevlar-aramid-fiber-kwolek/md",
  "google_patents_url": "https://patents.google.com/patent/US3819587",
  "relatedPatents": [
    {
      "patentNumber": "3671542",
      "countryCode": "US",
      "title": "How Stephanie Kwolek Invented the Liquid Crystal Solution for Kevlar",
      "url": "https://patentbrief.org/patent/us/3671542/kevlar-aramid-fiber"
    },
    {
      "patentNumber": "2130523",
      "countryCode": "US",
      "title": "How Wallace Carothers Invented Nylon",
      "url": "https://patentbrief.org/patent/us/2130523/nylon-polyamide-carothers"
    },
    {
      "patentNumber": "2929804",
      "countryCode": "US",
      "title": "How Spandex Elastic Fibers Are Chemically Engineered",
      "url": "https://patentbrief.org/patent/us/2929804/spandex-lycra-elastic-fiber"
    },
    {
      "patentNumber": "3733309",
      "countryCode": "US",
      "title": "How Plastic Soda Bottles Are Made Stronger Using Stretched Molecules",
      "url": "https://patentbrief.org/patent/us/3733309/pet-plastic-bottle"
    },
    {
      "patentNumber": "3953566",
      "countryCode": "US",
      "title": "Making Strong, Porous PTFE: The Gore-Tex Process",
      "url": "https://patentbrief.org/patent/us/3953566/gore-tex-expanded-ptfe"
    }
  ]
}