Ultrasonic characterization of the crystallization behavior of poly(ethylene terephthalate)

Based on previous observations that the ultrasonic signals are sensitive to the crystallization of polymers (Tatibouet, J., Pich\ue9, L. Polymer 1991, 32, 3147), we have expanded our efforts to study the detail relationship between the ultrasonic signals and crystallization process in the present work. The nonisothermal and isothermal crystallization of virgin poly(ethylene terephthalate) (PET) and PET samples after degradation were studied by using a specially designed pressure-volume-temperature (PVT) device, with which an ultrasonic detector was combined. The results showed that the evolution of the ultrasonic signals not only can be used to probe the crystallization process, but also can qualitatively characterize crystallization rate, crystallinity, crystallite size and amorphous. DSC measurement was used to verify such results. Ultrasonic signals could be as a complementary tool to polymer chain movement and well be applied to characterize the crystallization behaviour. Furthermore, the ultrasonic measurement has the potential use to characterize crystallization of products in-line during processing (i.e., injection molding, microcoulding).Sur la base d\u2019observations pr\ue9c\ue9dentes indiquant que les signaux ultrasoniques sont sensibles \ue0 la cristallisation des polym\ue8res (Tatibouet et Pich\ue9, Polymer 1991, 32, 3147), on a poursuivi nos efforts afin d\u2019\ue9tudier en d\ue9tail la relation entre les signaux ultrasoniques et le processus de cristallisation. On a \ue9tudi\ue9 la cristallisation isotherme et la cristallisation non isotherme d\u2019\ue9chantillons de poly(t\ue9r\ue9phtalate d\u2019\ue9thyl\ue8ne) (PTE) vierge et d\u2019\ue9chantillons de PTE apr\ue8s d\ue9gradation au moyen d\u2019un dispositif pression volume-temp\ue9rature sp\ue9cialement con\ue7u et d\u2019un d\ue9tecteur \ue0 ultrasons. Les r\ue9sultats montrent que l\u2019\ue9volution des signaux ultrasoniques peut non seulement servir \ue0 suivre le processus de cristallisation, mais aussi permettre de caract\ue9riser qualitativement la vitesse de cristallisation, la cristallinit\ue9, la taille des cristallites et le caract\ue8re amorphe. On a utilis\ue9 des mesures de CCP pour v\ue9rifier ces r\ue9sultats. Les signaux ultrasoniques pourraient servir d\u2019outil compl\ue9mentaire pour le mouvement de la cha\ueene polym\ue8re et pourraient \ueatre utilis\ue9s pour caract\ue9riser le comportement \ue0 la cristallisation. De plus, la mesure ultrasonique peut \ueatre utilis\ue9e pour caract\ue9riser la cristallisation de produits en ligne pendant leur traitement (p. ex., moulage par injection et micromoulage).Peer reviewed: YesNRC publication: Ye

Ultrasound as a complementary tool to internal mixers for investigation of thermal mechanical degradation of PET

Peer reviewed: YesNRC publication: Ye

PS Foams Blown from HFC-134a/HFC-32 Blends: Foams Properties

Peer reviewed: YesNRC publication: Ye

Heterogeneous nucleation in foams as assessed by in-line ultrasonic measurements

The conditions prevailing during the nucleation stage of the thermoplastic foam extrusion process in which a physical foaming agent is involved are one of the key steps in the design and optimization of the process. The conditions that induce phase separation and bubble nucleation are obviously linked to the solubility parameters, i.e., temperature and pressure at a given foaming agent content, conditions that can be probed during degassing experiments. It has been reported that adding a nucleating agent can significantly modify these degassing conditions. An in-line detection method based on ultrasonic sensors has proven to be sensitive to the onset of the phase separation. This method was used to investigate the influence of both talc and foaming agent concentrations on the nucleation cell density and degassing conditions for polystyrene\u2013HFC-134a mixtures. A qualitative model based on foaming agent concentration gradient near the nucleating agent particles is proposed.Peer reviewed: YesNRC publication: Ye

Ultrasonic Characterisation and Sensors: PLA Crystallization

While low-density foam extrusion of amorphous poly(lactic acid) (PLA) has been performed with success, foaming its semi-crystalline counterpart still remains problematic. Blowing agents such as carbon dioxide affect the crystallization kinetics of PLA which has a strong impact on the processing window. The effect of dissolved CO2 molecules on the crystallization kinetics of PLA, as well as the decrease of the glass transition temperature, were investigated using an original device that combines ultrasonic and volumetric measurements. Contrarily to high-pressure DSC measurements, applied pressure and CO2 concentration can be studied independently with this device. Ultrasonic parameters such as sound velocity are very sensitive to crystallization and were thus used to monitor the crystallization kinetics. The crystallization rate was found to tremendously increase with a moderate addition of CO2 and the results are compared with classical DSC measurements. Impact on foam processing is also finally addressed.Peer reviewed: NoNRC publication: Ye

Foaming Biodegradable Polymers: Effect of Dissolved Carbon Dioxide on Crystallization of Poly(Lactid Acid) as Probed by Ultrasonic Measurements

Peer reviewed: NoNRC publication: Ye

An in-process ultrasonic approach to investigating the relaxation of orientation and disorientation of polymer melts

Peer reviewed: YesNRC publication: Ye

Influence of the Hydrogenation Step on Selectivity during the Nonoxidative Oligomerization of Methane to Alkanes on Pt/SiO2Catalysts (EUROPt-1)

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Real-time Ultrasonic Diagnostics of Polymer Extrusion and Injection Molding Processes

Peer reviewed: NoNRC publication: Ye