A Dynamic Study of Crystallization of Poly(ε-caprolactone) and Poly(ε-caprolactone)/Poly(vinyl chloride) Blend

Abstract

ABSTRACT:The crystallization of poly(c-caprolactone) (PCL) and a compatible blend of PCL with poly(vinyl chloride) were studied by a small angle X-ray scattering (SAXS) method with synchrotron radiation and by microscopic observation. By the SAXS method, the peak of the scattering intensity, arising from the long period in the sample, was observed during crystallization. The maximum intensity of the peak, Jm, increased with crystallization time t, and reached a constant value Jm(oo) at time 2r( 12 (r( 12 is the time necessary for Im to reach Jm(oo)l2). The value of r( 12 increased abruptly with an elevation of the crystallization temperature T, for both pure PCL and the blend, and r(12 for the blend was larger than that for pure PCL at the same T,. The change of Jm against t, was analysed by the Avrami equation, the exponent n being about 2 for the blend at every T, and pure PCL at higher T,. For pure PCL at lower T,, n increased with the decrease ofT,. In the microscopic observation of both pure PCL and the blend, the spherulite radius increased linearly with t,, and the linear growth rate G of spherulite decreased with T,. A correspondence was found between T, dependence of r(12 and that of 11G.KEY WORDS Crystallization I Microscopic Observation I Polymer Blend I Samll Angle X-Ray Scattering I Synchrotron Radiation I In compatible polymer blends, the crystallization of components, together with the liquid-liquid phase separation, control the morphology organized and hence the various properties of polymer blends. 1 • 2 The dynamics of the phase separation has extensively been studied by a laser light scattering technique and the mechanism has been elucidated for many systems. 3 -6 The dynamics of crystallization, on the other hand, has been studied mainly by an optical microscope, a dilatometry, and a differential scanning calorimetry (DSC).2.7.s These methods are based on the macroscopic or overall change during crystallization, and the change of finer morphology, for example, lamella thickness, could not be measured. Recently, the small angle X-ray scattering (SAXS) technique with a strong source such as synchrotron radiation has become available. 9 -16 The strong sources have made possible the observation of the change of the fine morphology at the initial stage of crystallization against crystallization time. Schultz et a/. 17 · 18 studied the crystallization of a linear polyethylene at various temperatures Teo and found that the crystallization behavior at higher Tc was different from that at lower Tc. At higher Tc, the long period and the lamella thickness were nearly invariable during crystallization; but at lower Tc, the long period decreased with time because of the appearance of new lamellae in the amorphous regions between lamellae. Elsner et a/. 11 • 12 studied the crystallization process of oriented and unoriented poly(ethylene terephthalate) (PET) with synchrotron radiation and found that the 451

Spherulite Structure in Compatible Mixtures of Poly(ε-caprolactone) and Poly(vinyl chloride)

“…The crystallization rate of PCL in the blend may be responsible for the formation of the extinction ring in the spherulite structure of the blend. 6 In summary, the spherulite structure with a Maltese cross and distinct extinction rings could be observed in PCL/PVC blends with 0. 70 < <PrcL < 0.99, whereas no extinction ring could be observed in pure PCL and blends with <PrcL < 0.…”

Dynamic Mechanical Study of Block Copolymer Crystallization Confined within Spherical Nanodomains

“…Details of the equipment and the instrumentation are described in our previous publications. [25][26][27] The SR-SAXS curves measured were corrected for background scattering and absorption by the sample, but not for the smearing effect because SAXES employed a point focusing optics. The SAXS curves were finally obtained as a function of s defined by s ¼ ð2=!Þ sin , where 2 is the scattering angle and !…”

Experiências simultâneas de espalhamento de raios X e calorimetria diferencial de varredura (SAXS/WAXD/DSC) com resolução temporal utilizando radiação síncrotron

“…Em todos os casos os valores de n foram não inteiros, indicando que ocorrem paralelamente mecanismos de crescimento e/ou nucleação secundária superficial [9] . Para a PCL o valor fica em torno de 2,5, independentemente da temperatura de cristalização, sendo coerente com outros resultados descritos na literatura [10] . Para a blenda em temperaturas de cristalização inferiores ou iguais a 39 °C o valor de n é semelhante ao da PCL pura, porém, para temperaturas de cristalização maiores que 39 o C o valor de n diminui indicando mudanças no mecanismo de nucleação e crescimento da PCL, o que provavelmente é causado pela presença das cadeias do PECl.…”