Annealing above the crystallization

It is known that elevating the crystallization temperature [42,49] or annealing above the crystallization temperature [50] of PE results in a thicker folded-chain lamella of up to —200 nm. In addition to the higher temperature, if high pressure is applied, crystals can grow as thick as several micrometers in the chain axis direction [2-4,51]. 

Small Angle Scattering During Annealing Above the Crystallization Temperature... 

The films are in amorphous state uuder the as-deposited condition however, if they are annealed above the crystallization temperature, nano Fe or CoFe grains are deposited, and other components inhibit the grain growth. This basic concept is used for the preparation of Fe-based nano-crystalline alloys, such as Fe-Cu-M (M=Nb, Zr, Hf, Ta)-Si-B (B = 12-13 kG) [11] and Fe-M (M=Ta, Nb, Hf)-N(C) (B = 15-16 kG) [12]. These films are mainly prepared by sputtering or evaporation. Rapidly quenched ribbons such as Fe-Cu-M (M=Nb, Zr, Hf, Ta)-S i-B (B = 12-13 kG) [13] are formed by the same technique. Furthermore, sputtered CoAlO, FeAlN, and... 

Ammonium hydroxide has also been used in place of NaOH or KOH [20,24,26]. In reported contrast to films deposited from alkali metal hydroxide, these films, prepared at or slightly above room temperature, were photoconductive (photosensitivity ca. 10) as deposited without need for air-annealing [26]. The crystal size of films deposited at different temperatures was measured (XRD line broadening) to be 10-15 nm (30°C), 17 nm (40°C), and 39 mn (50°C) [24,26]. The presence of strain in the crystals was inferred from the same XRD measurements [24]. 

Comparison between the Crystallization from the Melt or the Glass. The crystallization studies at low temperatures can either be performed on samples cooled from the melt to the crystallization temperature or on quenched samples which are annealed to the crystallization temperature. Each method would be indicated for the particular region where equilibration to the crystallization temperature would be faster without having induced crystallinity in the amorphous polymer. In general, crystallization from the melt is better at temperatures above that which gives the maximum in growth rate, and crystallization from the glass is better for temperatures lower than the maximum. 

The crystalline polymer may exist in two forms a and p. The higher melting cx-form, having an orthorhombic unit cell, is formed when the polymer crystallizes out of the melt or solution. The thermodynamically unstable P-form occurs when quenched amorphous polymer is annealed above the glass-transition temperature annealing at 115 °C transforms the P-form into the a-form. The average size of lamellae formed in isothermal crystallization is 1000-2000 A in lateral dimensions, with a thickness of 100 A. 

Because of the complexity of the system it was not possible to correlate the different values unequivocally with identified morphological structures. However, it seems to be reasonable to attribute "" which appears after annealing above the glass transition of PC - to small PC crystals. The growth of these crystals was proved by isothermal dynamic... 

It was later confirmed by Ide and Chung [119] that these observations were also valid for thermotropics. Small-diameter rods of a longitudinal PLC (a copolyester based on 2,6-hydroxynaphthoic acid, terephthalic acid and p-aminophenol) were annealed above its crystal melting temperature in the nematic state for different periods of time. The dependence of the Young modulus at room temperature on the... 

Stress-strain relationships are determined by DMA and temperature scans reveal glass transitions, crystallization and melting information. Blends of polypropylene and rubber have been studied by where the intensity of one of the two crystallization exotherms was used as a measure of the polypropylene domains and compared to the size determined by TEM cryomicrotomy and osmium tetroxide staining methods [25]. Isothermal annealing of PET above the crystallization temperature was shown to influence the morphology and increase thermal stability by combined SAXS and DSC analysis [26]. An excellent text edited by Turi [21] described the instrumentation and theory of thermal analysis and its application to thermoplastics, copolymers, thermosets, elastomers, additives and fibers. 

Crystallization of cellulose acetates (d.s. 2.2—3.0) has been achieved by annealation in the presence of either nitromethane or nitromethane-n-butanol in overcooled dilute solutions. Cellulose acetate I crystallized over the whole range of compositions when annealed above the glass temperature thermal treatment of cellulose acetate II brought about crystallization of samples of d.s. 2.6, whereas heating in the presence of polar liquids resulted in crystallization over the whole range of compositions. Cellulose acetate I was converted into cellulose acetate II on heating in ethanol, and cellulose acetate II crystallized spontaneously from acetone at room temperature. A comparison of the crystalline forms obtained from cellulose acetates of different d.s. was also made. 

Crystal Beta 111 solution annealed above the transus is... 

Isothermal annealing of PET above the crystallization temperature was shown to influence the morphology and increase thermal stability by combined SAXS and DSC analysis... 

To erase information by the transition amorphous — crystalline, the amorphous phase of the selected area must be crystallized by annealing. This is effected by illumination with a low power laser beam (6—15 mW, compared to 15—50 mW for writing/melting), thus crystallizing the area. This crystallization temperature is above the glass-transition point, but below the melting point of the material concerned (Eig. 15, Erase). 

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