Characterization of the isothermal crystallization of poly(ethylene terephthalate) by microhardness measurements

Pastor, J. M.; González, Ana García; Saja, J.A. de

doi:10.1002/app.1989.070381211

Cited by 22 publications

(10 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This band is assigned to the aromatic ring mode 1 , 68 and it is generally used as a reference band due to the fact that it is independent of the thermal history and unaffected by any crystallinity changes. 69,70 The band at 1097 cm Ϫ1 , which is attributed to the combination of ring C-C stretching, ester C(O)-O stretching, and ethylene glycol C-C stretching modes, 47 is mentioned to be characteristic of the all-trans (TtT B ) conformation in the chain 2 and has been widely used as a measurement of the level of crystallinity. 2,16,65,69 However, there are some studies where it was believed that this band is only associated with the trans glycol conformations and not directly with the increase in crystallinity.…”

Section: Resultsmentioning

confidence: 99%

Vibrational Spectroscopic Study on the Origin of Stress Oscillation during Step-Wise Stretching in Poly(Ethylene Terephthalate)

2004

View full text Add to dashboard Cite

The origin of the phenomenon of stress oscillation during step-wise stretching at room temperature for amorphous poly(ethylene terephthalate) (PET) was investigated using vibrational spectroscopy. For the first time, transmission Fourier transform infrared (FT-IR), attenuated total reflection (ATR) FT-IR, and micro-Raman spectroscopies were used in order to investigate the correlation of the orientation of the molecular chains, their conformational transformations, and the appearance of stress-induced crystallization to the phenomenon of stress oscillation during the step-wise stretching procedure. The phenomenon of stress oscillation occurs when amorphous PET is exposed to mechanical stress during which the extension rate is increased in a step-wise manner. This phenomenon leads to the formation of a pattern of opaque and transparent stripes (''striated'' or oscillating region), clearly distinguished from the unstretched (''bulk'') and the ''necking'' regions. Both infrared and Raman spectroscopic investigations revealed that the main conformational transformations and a significant increase of the crystallinity occur simultaneously in the ''striated'' region. Polarized infrared experiments showed the presence of increased molecular orientation, which is more profound for the ''intense striated'' region. Finally, micro-Raman spectroscopy allowed the study of opaque and transparent stripes individually and showed that the opaque stripes are more crystalline. Thus, our findings provide conclusive experimental support for the theory, which directly correlates the appearance of the stress-oscillation phenomenon with the induction of crystallinity and heat release and is based on Barenblatt's model. Our study also provides new conformational assignments for the infrared bands in PET for the high-frequency region from 3200 to 3800 cm(-1). Specifically, the bands at 3336 cm(-1) and at 3298 cm(-1) have been attributed to the trans and gauche conformations, respectively.

show abstract

Section: Resultsmentioning

confidence: 99%

Vibrational Spectroscopic Study on the Origin of Stress Oscillation during Step-Wise Stretching in Poly(Ethylene Terephthalate)

2004

View full text Add to dashboard Cite

show abstract

“…19)] increases in intensity when annealing temperature rises, in accordance with several previous works (Refs. [27][28][29][30][31][32][33][34]. Although the 1117 cm-1 band has been usually used as a reference band in Raman spectra because it does not show changes with annealing treatment (Refs.…”

Section: Analysis Of Benzene Ring Vibration Modesmentioning

confidence: 99%

“…Although the 1117 cm-1 band has been usually used as a reference band in Raman spectra because it does not show changes with annealing treatment (Refs. [27][28][29][30][31][32][33][34], for maintaining the parallel analysis with the infrared study, the Raman band situated at 795 cm-1 is used as reference. The 11094/1795 intensity ratio in Figure 9 again shows the sigmoidal and linear evolution process in PET.…”

Section: Analysis Of Benzene Ring Vibration Modesmentioning

confidence: 99%

See 1 more Smart Citation

A comparison between PA‐FTTR and FT‐Raman spectroscopies in the structural analysis of annealed injected‐moulded poly (ethylene terephthalate)

Quintanilla

Rodríguez‐Cabello

Merino

et al. 1995

Macromolecular Symposia

View full text Add to dashboard Cite

With the introduction of the Fourier Transform technique in Raman spectroscopy (FT‐Raman) and the development of new methods in FTIR, such as FTIR with photoacoustic detection (PA‐FTTR), vibrational spectroscopy has been launched into a new era of application in polymer chemistry and physics. This work provides a comparative study between PA‐FTIR and FT‐Raman techniques in which the potentials and limitations of these two methods are investigated by following and analyzing structural variations that take place in annealed injected‐moulded poly(ethylene terephthalate) (PET). Both spectroscopic techniques appear to be suitable to detect structural changes that occur in PET submitted to different annealing temperatures. We suggest that these variations are directly related to conformational rather than crystallinity changes. The main drawbacks of PA‐FTIR are the lengthy adquisition time of spectra and the photoacoustic saturation that can appear in regions with quite high optical absorption coefficient. Conversely, FT‐Raman technique does not suffer from neither of these problems. However, the sensitivity to structural changes of certain infrared bands seems to be higher than that of analogous Raman bands and small structural details such as the regularity of chain folding, can only be detected in the infrared spectra.

show abstract

“…Variations in hardness have been observed that correlate with morphological variations caused by processing, including depth profiling in injection moldings and changing molding conditions [2][3][4][5] and drawing [6]. Other studies attempted to relate microhardness to microstructure and included preparation of different microstructures by careful control of the crystallization conditions [7][8][9][10]. Microhardness measurements have been used to study morphologyrelated properties in polymer blends [11,12].…”

Section: Introductionmentioning

confidence: 99%

Dynamic nanoindentation of some polyolefins

Bouaita

Bull

Palacio

et al. 2006

Polymer Engineering & Sci

View full text Add to dashboard Cite

Nanoindentation tests have been conducted on five different polyolefins, comprising a high density polyethylene, a low density polyethylene, a linear low density polyethylene, a polypropylene homopolymer and a polypropylene copolymer. The nanoindenter was fitted with a "Dynamic Stiffness Measurement" (DSM) facility that permits measurement of storage modulus and loss modulus at frequent intervals during an indentation test. The results were quite scattered, especially those for the loss modulus, and methods of processing the data to derive meaningful results were examined and are discussed. The storage modulus measurements were found to give the same stiffness ranking as the monotonic load-displacement data when comparing indentations on the same material. Some correlation was found between the storage modulus and fractional crystallinity. An averaging procedure was developed for the loss modulus values that appeared to give a consistent assessment of the dissipation properties of the different materials. Analysis of the monotonic component of the load-displacement data indicated that the nature of the deformation changed from mainly elastic/viscoelastic to mainly viscoelastic/plastic during the course of the indentation tests. POLYM. ENG. SCI., 46: 1160 -1172, 2006.

show abstract

Characterization of the isothermal crystallization of poly(ethylene terephthalate) by microhardness measurements

Cited by 22 publications

References 27 publications

Vibrational Spectroscopic Study on the Origin of Stress Oscillation during Step-Wise Stretching in Poly(Ethylene Terephthalate)

Vibrational Spectroscopic Study on the Origin of Stress Oscillation during Step-Wise Stretching in Poly(Ethylene Terephthalate)

A comparison between PA‐FTTR and FT‐Raman spectroscopies in the structural analysis of annealed injected‐moulded poly (ethylene terephthalate)

Dynamic nanoindentation of some polyolefins

Contact Info

Product

Resources

About