Deformation-Induced Phase Transitions of Polyamide 12 at Different Temperatures: An in Situ Wide-Angle X-ray Scattering Study

Abstract

Deformation-induced phase transition of polyamide 12 (PA 12) was studied with in situ wideangle X-ray scattering (WAXS) at temperatures below and above glass transition temperature. Irrespective to the testing temperature, a transient R 00 phase occurred in the early plastic deformation stage, whose lifetime is decreasing with the increase of temperature. At temperature below glass transition temperature, the transient R 00 phase further transforms into a mesomorphic state with increasing the strain, while high temperature promotes the transient R 00 phase transforming into γ 0 phase. The different final states at temperatures below and above glass transition temperature is due to the competition and coupling between external work and thermal activation. External work from tensile deformation is responsible for the appearance of the transient R 00 phase and the final mesomorphic state at temperature below glass transition temperature, while thermal activation drives the transition from the transient R 00 phase to γ 0 phase. All these phase transitions occur in the plastic deformation region, which shows a close correlation between the mechanical response and the structural evolution during tensile deformation.

Transcrystallization in nanofiber bundle/isotactic polypropylene composites: effect of matrix molecular weight

“…Nevertheless, a shoulder peak can be observed in Fig. 2d and this may be resulted from the stretching effect of the electrical force and the rotating needle [31]. Figure 3 shows the transcrystalline evolution at 133°C.…”

Transient microstructure in long alkane segment polyamide: Deformation mechanism and its temperature dependence

“…Along with the new evidence, the existing model was further improved and some hypotheses of lamellae slippage and melting-recrystallization were also introduced. From another point of view, phase transition triggered by stretching has also been extensively reported for many materials, such as polyamide (PA) [10,20,21], PP [17,22,23], and poly(ethylene terephthalate) (PET) [24,25]. These varying crystal structures may endow polymers with unique physical properties.…”

“…For instance, Hsiao et al [24,25] summarized that multiple phase transitions and microstructure evolution of PET below or above Tg included the transformation among amorphous, nematic, smectic and crystalline phases. It is noted that the structure response of LCPA during elongation has been widely investigated by Li [10] and Mo [20] with particular attention to the crystal transition. For PA12, during stretching, phase transition takes place and a transient phase (a 00 phase) is formed in the intermediate phase, which may influence the drawing ability [10].…”

Hybrid carbon fibre/nylon 12 single polymer composites

“…The photos also show meridional peaks (in the vertical direction) which are clearly visible at 171, 174 and 176C, but are absent for the sample made at a compaction temperature of 179C. The white arrow on the photo from the sample at 174C shows the position of the first meridional peak, and this was measured to occur at a value of 2 of 5.8 and can be associated with the (020) reflection [28]. The photos confirm major crystalline melting of the fibres has occurred by a compaction temperature of 179C, in good agreement with the DSC results.…”

“…The sample made a 171C shows equatorial peaks (horizontal) at a value of 2 of 21.4 (associated with the oriented PA12 fibres) plus more diffuse equatorial peaks at a higher 2 value of around 25.5 associated with the carbon fibres. The PA12 equatorial peak is associated with the (001) crystalline reflection [28]. As the compaction temperature is increased it can be seen that the equatorial spots gradually transform into rings (at 179C) suggesting the oriented structure associated with the fibres has been lost as the fibres are melted and recrystallised in a random orientation.…”