Structure-property relationships of linear methyl-phenyl-vinyl siloxane terpolymers

Conference · Thu May 08 04:00:00 EDT 1980

OSTI ID:5380439

Hammon, H G; Hoffman, D M; S, Jessop E; Kolb, J R; Riley, M O

LLNL has an active interest in the synthesis and characterization of siloxane polymers with properties tailored to meet specific design requirements. We have synthesized a series of 15 random terpolymers of dimethyl-diphenyl-methylvinyl siloxane. In seven terpolymers the concentration of the methylvinyl repeat unit was varied from 0 to 5 weight percent maintaining phenyl content constant at 12 percent. The other eight terpolymers contained 0 to 18 weight percent phenyl repeat unit maintaining vinyl at one percent. As nearly as possible comparable molecular weights (5 x 10/sup 5/) were maintained. The gum stocks were reinforced with approx. 25 percent fumed silica. Silicones of different vinyl content were cured with a vinyl specific peroxide and characterized by swelling and mechanical properties. The moduli increased directly with vinyl concentration, but the longation to break decreased until at about two percent vinyl the rubber becomes extremely friable. Increasing the phenyl content in the silicone decreased the degree of crystallinity and increases the polymer class transition in accord with theoretical predictions. The major effect of incorporation of phenyl groups is the elimination of the polymer's ability to crystallize at about three percent phenyl. This extends the rubbery plateau to the glass transition (-117/sup 0/C) instead of the melting point (-44/sup 0/C).

• Research Organization: California Univ., Livermore (USA). Lawrence Livermore Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5380439
• Report Number(s): UCRL-84303; CONF-800814-2; CONF-800628-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360401* -- Polymers & Plastics-- Preparation & Fabrication-- (-1987)
ALKYL RADICALS
ELASTOMERS
GLASS
MELTING POINTS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHYSICAL PROPERTIES
POLYMERS
RADICALS
RUBBERS
SILICONES
SILOXANES
SYNTHESIS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VINYL RADICALS