Inexistence of glass transition temperature ?

Question

Viscoelastic materials such as polymers typically exist in two distinct states.The glass transition temperature (Tg) is often measured by DSC (Differential Scanning Calorimetry), but the DMA technique is more sensitive and yields more easily interperted data.But my polymer shows inexistence of Tg(from both DSC and DMA data), what does it imply?

P.S: My polymer is not crosslinked thermosetting plastics .

Answer 1

crosslinking:

" such behavior is not exhibited by crosslinked thermosetting plastics which, once cured, are set for life and will shatter rather than deform, never becoming plastic again when heated, nor melting."

Answer 2

(m) glass transition temperature A material’s glass transition temperature, Tg, is the temperature below which molecules have little relative mobility. Tg is usually applicable to wholly or partially amorphous phases such as glasses and plastics. For inorganic or mineral glasses, such as common silicon dioxide (SiO2) glass, it is the mid-point of a temperature range in which they gradually become more viscous and change from being liquid to solid. Thermoplastic (non-crosslinked) polymers are more complex because, in addition to a melting temperature, Tm, above which all their crystalline structure disappears, such plastics have a second, lower Tg below which they become rigid and brittle, and can crack and shatter under stress. Small molecular weight pure substances such as water have just one such condensed-phase temperature, below which they are solid crystals (or amorphous ice if cooled below Tg fast enough) and above which they are liquids. Above Tg, the secondary, non-covalent bonds between the polymer chains become weak in comparison to thermal motion, and the polymer becomes rubbery and capable of elastic or plastic deformation without fracture. This behavior is one of the things which make most plastics useful. But such behavior is not exhibited by crosslinked thermosetting plastics which, once cured, are set for life and will shatter rather than deform, never becoming plastic again when heated, nor melting.