Here we present the concept of cross-linking high polymers at a critical degree right at the borderline between thermoplastics and elastomers to gain innovative new property characteristics. Critical cross-linking allows the polymer material to mostly retain its thermoplastic properties (crystallinity, stiffness, strength, etc.), but also offers the possibility to keep the macromolecules in constrained, stretched state for unlimited time. Due to the prevention of flow the stretched macromolecules cannot relax as they do in a typical polymer melt. This is important because self-organization of elongated polymer chains is often slower than relaxation processes. This way, we expect to imprint new properties into materials that are based on self-organization of stretched polymer chains without time constraint due to plastic deformation. To this end, high polymers are cross-linked with varying cross-linking densities and then investigated with dynamic mechanical analysis for determining the Young's modulus in dependence on temperature. Figure 1 depicts an idealized graph, showing that the material with the critical cross-linking density acts like the melt but does not yield.<br/>By taking the example of isotactic polypropylene (iPP) we will show that critical cross-linking provides the opportunity to gain multiaxially reinforced iPP upon uniaxial stretching (Fig .2).

Novel properties of polymers upon critical cross-linking right at the borderline between thermoplastic and elastomer

253rd National Meeting (2017)

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