Patents Assigned to PMCMA Research Group
  • Plaster molding composition
    Patent number: 4148660
    Abstract: A fiber-free plaster molding composition which comprises by weight approximately 50-70% gypsum plaster, 5-25% fine expanded perlite, and 5-30% of a non-fibrous filler such as mica, silica, fly ash, pyrophyllite or mixtures thereof. The composition of this invention has good dry blending properties, slurry characteristics, and wet and dry mold features, making it a suitable replacement for fiber-containing molding compositions for low fusion metal casting molds.
    Type: Grant
    Filed: December 19, 1977
    Date of Patent: April 10, 1979
    Assignee: PMCMA Research Group
    Inventors: David R. Lankard, Walter A. Hedden
  • Plaster molding composition
    Patent number: 4081283
    Abstract: A fibrous talc-free plaster molding composition comprises by weight approximately 50-70% gypsum plaster, 5-20% fibrous wollastonite, 5-25% fine expanded perlite, and 0-40% of a filler selected from the group consisting of sand, fly ash, pyrophyllite and mixtures thereof. The composition of this invention has good dry blending properties, slurry characteristics, and wet and dry mold features, making it a suitable replacement for fibrous talc-containing molding compositions for low fusion metal casting molds.
    Type: Grant
    Filed: February 23, 1976
    Date of Patent: March 28, 1978
    Assignee: PMCMA Research Group
    Inventors: David R. Lankard, Walter A. Hedden