Hermans orientation factor

It can be assumed that the orientation of the amorphous regions is a result of the deformation of a rubber-elastic network. Therefore, it can be expected that crystallization during spinning occurs at the neck, where the deformation is maximal. The amorphous phase develops into a load-bearing factor which is related to its orientation, as expressed by Hermans orientation factor. 

The x-ray diagram [58] of coir confirms its two spiral-structured and layers. The degree of crystallinity of the coir does not appear to be very high. Harris [58], Chakravarty, and Hearle [35] report the spiral angle to be 45°. Varma et al. [178] report a more extensive X-ray analysis of treated and untreated fibers. The present crystallinity and Hermans orientation factor, /o, obtained are tabulated below ... 

Mendoza et al. (2003) used the Hermans orientation factor describe the measured results. The orientation factor is defined by... 

The velocity of sound depends on the modulus, and the velocity of sound is greater when it propagates along than transverse to the chain axis. In a semicrystalline polymer, both the crystals and the amorphous phase contribute in proportion to their relative contents. In that sense, the sonic modulus is similar to birefringence. The following expression relating sonic modulus ( ) and Hermans orientation factor for a semicrystalline polymer was derived by Samuels (1974) ... 

The orientation of chopped fibers developed during flow/processing can strongly influence various properties of compounds, such as modulus and tensile strength. In 1974 Brody and Ward [79] described fiber orientation in uniaxial fiber filled composites using Hermans orientation factors [80 to 82] originally developed to measure polymer chain orientation in man-made fibers (see Fig. 2.5(a)). 

A Bruker AXS wide-angle X-ray diffractometer with a Cu Ka average source (k = 1.5418 A) was utilized to look at the crystalline structure of the overall composite sample and to calculate the Herman orientation factor. The samples were run in transmission and reflection modes. In the reflection mode, the... 

Observations of infrared dichroism on pol3rmeric systems were first made about 1950 using pols peptides (53,54). Fraser (55,56) developed its use to measure orientation in polymers quantitatively and establish a relationship of dichroic ratio D to the Hermans orientation factor equivalent to equation 2. The first infrared dichroism studies on polyethylene were performed in 1954 by Stein and co-workers (57,58). The article (58) discusses the determination of uniaxial orientation in polyethylene films using wide-angle x-ray (wax) diffraction, birefringence, and infrared dichroism, and explicitly states the interrelation of the former two measurements through... 

Kejcwords amorphous orientation, crystalline orientation, Herman s orientation factor, infrared spectroscopy (IR), IR band assignment, optical birefringence, orientation, structure-property relationships in fibers, X-ray diffraction... 

Using the intensity as a function of angle, %, around each diffraction ring, Herman s orientation factor can be determined. Herman s orientation factor (P2) is defined in Equation 8.2 ... 

P. H. Hermans and co-workers described how the orientation factor /h may be computed from wide-angle x-ray diffraction, and developed a simple theory of birefringence (45-47). Orientation measured by x-rays and by birefringence were distinguished (46). The former represents the orientation of the crystalline regions and the latter the total orientation, including amorphous regions ... 

Absorption bands associated with a perpendicular transition dipole moment have Dg = 0, and the Herman s orientation factor is given by ... 

Fig. 7.13 Schematic representation of the Herman s orientation factor, related to polymer chain stretching direction.

The factor having the strongest effect is the elongation imparted in the process of production stretching. Second, the overall orientation is affected by the stretching rate. For the same draw ratio, the overall orientation grows with an increase in the stretching rate. The effect of the draw ratio on the value of Hermans function of orientation is illustrated by the values of/o, established by the authors and depicted in Table 7. 

The orientation by birefringence,/o (Hermans factor) [61], representing an average value for both crystalline and less-ordered regions and the x-ray-derived crystallite orientation, f. ... 

As noted before, MLCs and PLCs share essentially the same kinds of phases these are nematic, cholesteric, and a variety of smectic phases. These three names have been proposed by Friedel [1] in 1922 who imagined that such phases should exist—long before his concepts were confirmed by diffiractometric experiments. In all these phases the entire molecules (in MLCs) or the LC sequences in the chains (in PLCs) are oriented approximately— but not quite—perpendicularly to a preferred axis in space called director. The degree of alignment is characterized by the order parameter (also called the anisotropy factor) defined in 1946 by Hermans [36] as... 

---