Amorphous components

If the amorphous component contributes nothing to the measured property (as with heat of fusion), then Eq. (4.39) reduces to Eq. (4.37). Specific volume is an example of a property which has been extensively used in this way to evaluate 6. 

Crystallinity has been studied by x-ray irradiation (85). An initial increase caused by chain scission in the amorphous phase was followed (above 3 kGy or 3 X 10 rad) by a gradual decrease associated with a disordering of the crystallites. The amorphous component showed a maximum of radiation-induced broadening in the nmr at 7 kGy (7 x 10 rad). 

Typically, a semicrystalline polymer has an amorphous component which is in the elastomeric (rubbery) temperature range - see Section 8.5.1 - and thus behaves elastically, and a crystalline component which deforms plastically when stressed. Typically, again, the crystalline component strain-hardens intensely this is how some polymer fibres (Section 8.4.5) acquire their extreme strength on drawing. 

Solid-state NMR can be applied equally well to both crystalline and amorphous solids (10-17), and can be used to distinguish and quantify the crystalline and amorphous components of multi-component solids. Here we describe the... 

A factor analysis of the Raman spectra of a set of linear polyethylenes identified the existence of a third component in addition to the pure crystalline and pure amorphous components [78]. The characteristics of the Raman spectrum of the interphase were very similar to that of the crystalline spectrum indicating that the interphase retains a significant degree of order. Using the Raman method, the content of interphase in linear polyethylenes was found to increase with molecular weight [74—76,78]. For molecular weights below... 

The independence of the tan 6 transition ( -47°C) on composition for the HI block for these series of block copolymers is another indication of good phase separation existing between the amorphous component of HB and HI blocks. This latter statement seems in order for if there were any appreciable mixing between... 

An amorphous component such as silica-alumina is added to the catalyst, for a sort of pre-cracking of the large molecules (greater than about C25), which cannot enter the zeolite pores. The smaller fragments may then react in the zeolite. Middle distillates maximum yield is achieved by the use of dealuminated Y zeolites. 

When dealing with partially crystalline materials, such as those produced by milling, the effect of water uptake is intensified. The amorphous component likely absorbs greater quantities of water than its crystalline counterpart, leading to reduced Tg, increased molecular mobility, and both physical and chemical instability. 

The final measure of crystallization effects is assessed by appropriate rigorous stability data (for example, 6 months accelerated stability at 40°C and 75% RH). This may seem excessive, but measuring the degree of crystallinity is inherently difficult because of low analytical sensitivity (for example, of amorphous components below 5% w/w), and pure single-phase standards are difficult to prepare and subsequently measure. 

Solute or particulate accumulation onto an aggregated phase (or solid state) that grows together by the addition of material at the periphery. Both cohesive and adhesive forces are thought to be driving forces in accretion. Sea shells and kidney stones are also known to form as layers of crystallites and amorphous components by accretion of external substances. 

The influence of the solvent can be observed, for example, with a PS/PC-blend CH2CI2 allows a faster evaporation and leads to the expected turbid film consisting of the amorphous components PS and PC. Instead,THF and CHCI3 evaporate slower and, hence, allow the PC to partially crystallize, which results In an opaque film. 

Figure 1.66 Resolution of the X-ray scattering curve of a semicrystalline polyethylene sample into contributions from crystalline (110 and 200 planes) and amorphous components. From F. W. Bilhneyer, Textbook of Polymer Science, 3rd ed. Copyright 1984 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Crystallization behavior in miscible blends containing crystallizable components has been extensively studied [174-180]. Generally, when a crystallizable component is mixed with an amorphous component its melting temperature goes down and its crystallinity lowers. The same trend has been reported for blends with intercomponent hydrogen bonding such as PCL/STVPh [181], PCL/poly(hydroxyl ether of bisphenol A) [182] and phenoxy resin/PEO [183]. 

Tan 6 curves from dmta thermograms of blends based on combinations of HPL/PVA(> 0) are shown in Figure 5 (10). The tan 6 transition, which is another measure of Ts, is broadened by the presence of HPL component, and it increases above that of the parent polymers consistent with dsc data. This can again be explained with the presence of strong interactions between the amorphous components which coexist in a closely associated state. 

Ultimate properties, tensile strength, and ultimate strain typically decrease with the addition of HPL however, combinations of molecules with strong interaction between amorphous components may also exhibit enhanced ultimate properties. Injection molding produces superior material properties. 

Some commercial, linear (thermoplastic) polymers produce blends with lignin and lignin derivatives that fail to result in phase separation on macroscopic scale. Polyblends with lignin derivatives sometimes resemble plasticized or anti-plasticized materials. The greatest contribution lignin can make to thermoplastic systems is that of modulus and this is the same as that which lignin makes to the amorphous component of wood. 

Figure 2. Glow curves of various polyethelenes with different ratios of crystallinity-amorphous components. Temperature rises from left to right. Peaks 0, y, where a is caused hy crystalline component, and y by amorphous...

Fig. 16. Difference spectrum melt-quenched amorphous component spectrum minus solution-cast amorphous component spectrum.

The two component FID (and corresponding superposed broad line spectra), for some polydimethylsiloxanes (PDMS) arises from crystalline and amorphous components. Polymers highly crosslinked with dicumyl peroxide exhibit quite similar data, but after the removal of all unlinked material, the FID consists only of a single component, indicating an almost complete reduction in crystallinity due to the cross-linking 84). 

The spectrum analysis shows that the solution crystals comprise about 85% lamellalike crystalline region and about 15% interlamellar amorphous overlayer, with a very minor liquidlike amorphous component at room temperature. However, the structure of the amorphous overlayer seems to be somewhat different from that in the bulk-crystals. For the bulk-crystals the second moment of the medium component ascribed to the amorphous overlayer appreciably decreases with increasing molecular weight. The quantity for the solution crystals, however, stays unaltered at a value as high as 8.4 G2 even if the molecular weight becomes as large as 3.4 x 106. The... 

At the same time the reaction products of La interaction with PlOH do always contain the amorphous component, being presumably the polymeric form of La(OPr )3 [953] (it was described by Mazdiyasni as the product of thermolysis or dehydrogenation of soluble yttrium alkoxides). 

---