Thermomechanical tests and the physical state of hypercrosslinked networks

1 Thermomechanical tests and the physical state of hypercrosslinked networks 

The behavior of hypercrosslinked polymers under uniaxial compression and/or heating was studied using a technique that was specially developed 

In order to understand the pecuHarities in the deformation of hypercrosslinked polystyrenes, let us first consider the deformation of conventional network styrene copolymers (Fig. 7.38). The copolymer incorporating 3% DVB exhibits two physical states, glassy and rubbery, with a narrow transition zone 

The hypercrossHnked network with 100% degree of crosshnking shows a noticeable deformation already at 140°C under a load of lOg. Under 400 g pressure (which stiU is 20 times smaller than the breakdown limit at 25°C) the deformation starts at the temperature as low as -50°C. Note that the deformation of the slightly crossUnked styrene-3% DVB copolymer under this load starts in the temperature zone almost 130°C higher. 

The maximum deformation AD of this 100% hypercrosslinked polymer achieves the value as high as 30% when the temperature approaches 300°C. Although this deformation is characteristic of rubber-like elasticity (Fig. 7.38, plots 1 and 2), no typical plateau can be observed (plot 3). This statement is also valid for the whole set of plots obtained at varying loadings in the interval from 10 to 450 g per bead (Fig. 7.39). AH plots have a flat 

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