The concept of a crystal-amorphous (also order-disorder) interface was first proposed by Flory [1962] for binary semi-crystalline/amorphous blends. The order-disorder interphase was defined as the region of loss of crystalline order.
In blend systems where the crystallizable polymer forms the continuous phase (i.e., blends with a crystallizable matrix), both the nucleation behaviour and the spherulite growth rate have been shown to be affected by the presence of a dispersed phase compared to the crystallization of the neat crystallizable component. Here, migration of heterogeneous nuclei from one blend phase to the other and the disturbance of the crystallization growth front due to the presence of dispersed blend phase are the most important phenomena that influence the crystallization behaviour of the matrix. These phenomena, however, mainly affect the final semicrystalline morphology; the crystallization behaviour of the matrix is usually only slightly affected by effect of a slightly lowered crystallization temperature.
In general, the major influence of blending is a change in the spherulite size and semicrystalline morphology of the matrix. Following the theoretical predictions the thickness of this region increases only slightly when stiffer chains are considered. Due to the higher degree of order of segments of the crystallizeable component in this zone, the penetration of the amorphous component is limited.
When the melt of a crystalline polymer is cooled to a temperature between the glass-transition and the equilibrium melting point, the thermodynamic requirement for crystallization is achieved.
The crystallization of miscible and immiscible polymer blends can differ remarkably from that of the neat crystallizable component(s). The overall crystallization kinetics of blends can often be described by the Avrami equation:
Where:
?: is the weight fraction of crystallinity at time t,
n: is the Avrami index depending on the type of nucleation and the crystal growth geometry.
k: is the Avrami constant related to the crystallization rate:
Where :
tn1/2 : is the half time of crystallization (the time for half the crystallinity to develop), which is often used as a measure for the overall rate of crystallization.
Avrami equation can be rewritten as:
Plotting the left part of this equation against log t should result in a straight line, from which both Avrami parameters, n (slope) and k (intercept),can be obtained.
In table bellow, some literature data on the Avrami constants and the half time of crystallization are presented.
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