Macromolecular Chemistry and Physics · 1999 · 56 citations · 0 references
Natural SciencesMaterials EngineeringMaterials ScienceMaterials ChemistryPolymer ChemistryPolymer MaterialsDynamic Mechanical AnalysisElastomeric PolymersPolymer CharacterizationPolymer CrystallinityPolymer PhysicsStress RelaxationDynamic Mechanical CharacterizationDynamic Mechanical PropertiesElastomeric MaterialsPolymer Relaxation ProcessesPolymer ViscoelasticityStress Relaxation Of PolymersViscoelastic Properties Of ElastomersViscoelastic Properties Of Polymers
Elastomeric poly(propylene) with low percentages of isotactic pentads and high molecular weight was synthesized using unbridged “oscillating” metallocenes. The polymer sample with the highest [mmmm] content (22%) shows a small amount of crystallinity, which is highly influenced by the thermal history, and differs significantly in stress-strain and dynamic mechanical properties from all other samples. Polymers with lower isotacticity index, although lacking crystallinity in thermal analysis, differ in their viscoelastic behaviour from those of atactic poly(propylene). In dynamic mechanical analysis the γ relaxation at low temperature shows high sensitivity to low isotactic contents.