Properties of radiation cured vinyl-divinyl copolymers. Part I. Thermomechanical properties of crosslinked methyl methacrylate polymers
Radiation copolymerization (crosslinking) of methyl methacrylate (MMA) with a series of divinyl monomers containing 1 to 4 ethyleneglycol connecting units between the terminal reactive divinyl units was found to provide numerous improvements in the thermomechanical properties of the copolymers. Thermoplastic poly-MMA was converted to a thermoset copolymer with only small additions (2 to 5%) of the divinyl crosslinking agent. When the measured thermomechanical properties (glass transition temperature, Tg, thermal distortion temperature, TDT; and thermomechanical deformation degree, TDD) of the above crosslinked copolymers were related to the respective crosslink densities (expressed by the copolymer connection number, CN/sub co/) the crosslink efficiency increased in terms of the above parameters in a reverse order as observed for acceleration, i.e., TEGDMA < TrEGDMA < DEGDMA < EGDMA. This observation is readily explained by the relation between segmental mobility of the respective macromolecules of the copolymers formed and the critical thermomechanical parameters which can be determined for such solid copolymers. Segmental mobility of the crosslinking agent increases with increasing molecular bridge length and hence the increased temperature sensitivity of the copolymers to thermal softening and distortion as the bridge length increases from a single ethyleneglycol (EGDMA) to four ethyleneglycol (TEGDMA) units in the bridge connecting the vinyl functions of the divinyl monomers. For all copolymers of this study, the linear thermomechanical deformation coefficient, representing thermal deformation between the plastic and rubbery states, remained relatively constant across a broad temperature interval until the respective TDT temperatures are reached, and decreased exponentially with the divinyl monomer concentration in the copolymer regardless of the connecting bridge length.
- OSTI ID:
- 5345221
- Journal Information:
- J. Radiat. Curing; (United States), Vol. 7:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
METHYL METHACRYLATE
CHEMICAL RADIATION EFFECTS
VINYL MONOMERS
COPOLYMERS
CROSS-LINKING
CURING
GLYCOLS
MECHANICAL PROPERTIES
TEMPERATURE EFFECTS
TENSILE PROPERTIES
ALCOHOLS
CARBOXYLIC ACID ESTERS
CHEMICAL REACTIONS
CHEMISTRY
ESTERS
HYDROXY COMPOUNDS
METHACRYLIC ACID ESTERS
MONOMERS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
POLYMERIZATION
POLYMERS
RADIATION CHEMISTRY
RADIATION EFFECTS
400600* - Radiation Chemistry
360403 - Materials- Polymers & Plastics- Mechanical Properties- (-1987)