Detection of polymer transition temperatures by infrared absorption spectrometry

Abstract

SynopsisInfrared bands in the 900-1100 cm-1 region are sensitive to thermal energy. These bands can result from intermolecular coupling, producing the crystal lattice, or from intramolecular coupling of the various atomic groups in a regular helix or coiled chain. I n either case an increase in temperature will disrupt the coupling mode, resulting in a form of structural relaxation and a reduction in the integrated absorbance. It is proposed that the temperature at which the peak areas begin to decrease be assigned as the T,. This is measured by continuously scanning a selected peak in the infrared spectrum of a polymer film while it is heated at a rate of about l"C/min. Using this technique polyamides (nos. 6,66, and 610) exhibited transitions in the 30-50°C range, and by studying the increase in the free NH region (3440 cm-' of nylon 66 two other transitions were detected a t 80 and 137OC; the latter represents a change in the nylon 66 crystal state. An amorphous film of poly(ethy1ene terephthalate) displayed a transition at 58-68°C (T,) and at 85"C, which is the crystallization temperature. Films of poly(viny1 acetate) and polyst.yrene exhibited transitions a t 25-37°C and a t 7OoC, respectively.

A molecular model for solid‐state polymerization of nylon 6

“…We r / R Radial profiles for [ W ] at different times, believe that using the local value of F,, in Eq. (18) instead of the spatial average value, b,,, will not lead to significant error in view of the fact that only a small region exists where pn is high, and the effect of p,, on p,,( t ) would be similar to that of K s / T & [see Eq. ( 18) and Fig.…”

Partial miscibility in a nylon‐6/nylon‐66 blend coalesced from their common α‐cyclodextrin inclusion complex

“…The aliphatic regions of the IR spectra of these samples are shown in Figure 7. Typically, in nylon polymers, the IR band around 2880 cm −1 is assigned to the CH symmetric stretch in CH 2 , and another band around 2940 cm −1 is assigned to the corresponding CH asymmetric stretch 20. Because both bands in the nylon‐6 spectrum are located at higher wave numbers than those in nylon‐66, even in the blends in which both nylon‐6 and 66 bands are all observed at higher wave numbers, each of these bands in the physical blend of nylon‐6 and nylon‐66 can be seen as two partially overlapped bands, corresponding to the two phase‐separated components in the blend.…”

New Insights into the Effects of Physical Aging on Glass Transition of Polystyrene by FTIR

“…As a result, the absorption of IR beam per unit area of the sample decreases, leading to a reduction in band intensity; [18] on the other hand, the increasing free volume provides more spaces for the segmental motions resulting in larger dipole moment changes, which may increase the band intensity. [25] In Fig. 1(a), the relative peak area decrease with temperature in the 70-90 • C region can be attributed to the dominance of the density effect.…”

“…Therefore, the influence of conformer changes can be avoided by studying this band. Since the peak area gives more accurate results, [25] the plot of relative peak area A/A 90 • C vs. temperature for 2847 cm −1 band is shown in Fig. 1(a), where A is the peak area for each temperature, and A 90 • C is the peak area for 90 • C. The heat capacity of aPS at various temperatures, calculated from DSC step-scan result, is depicted in Fig.…”