Partly Crystalline Materials

Since fibers consist primarily of oriented crystallites, it is unfair to classify them as heterophase. However, the generalizations of time-temperature superposition that work so well with amorphous polymers do not apply to fibers. Fibers do exhibit viscoelasticity qualitatively like the amorphous polymers. It comes as a surprise to some that J. C. Maxwell, who is best known for his work in electricity and magnetism, should have contributed to the mathematics of viscoelasticity. The story goes that while using a silk thread as the restoring element in a charge-measuring device. Maxwell noticed that the material was not perfectly elastic and exhibited time-dependent effects. He noticed that the material was not perfectly elastic and showed time effects. The model that bears his name was propounded to correlate the real behavior of a fiber. 

The relationship between density, linear density, tenacity, and strength fora round fiber of diameter D can be illustrated. An ordinary nylon fishing line of density 1.14 g/cm with a diameter of 0.850 mm has a rating of 60.0 lb (force) at break. 

In conventional engineering units, the strength is also given by 

Fracture studies of highly oriented nylon 6 flbers were performed by Zhurkov and coworkers [27-29]. They found that the stress dependence of the fracture time exhibits characteristics of a kinetic process. The extrapolated stress data at different 

FIGURE 10.17 Strength versus humidity for common fibers. (Data from Zurkhov, S. N., and E. E. Tomashevskii, in A. C. Strickland and R. A. Cook, eds., Proceedings of Conference on the Physical Basis of Yield and Fracture, Physical Society, London, 1966, 200.) 

---

They display a high non-flammability, and for a partly crystalline material, an unusually high impact strength. The high stability of the melt permits one to process the material using conventional methods (injection molding, extrusion). Accordingly, poly(arylene ether ketone)s are used in the automobile, electrical, and electronic industry. 

The most important structural characteristics of thermoplastics that are dependent on the processing conditions are (i) molecular orientation, (ii) residual stresses and (iii) crystal structure and degree of crystallinity (of partly crystalline materials). 

Photograph 7-95 Polished section of clinker particle after KOH-sugar solution extraction, leaving partly crystalline material (arrow) and brightly reflecting residual ferrite (center). (S A6713)... 

The untreated material shows unique features, as it exhibits a nearly perfect Debye relaxation centered around 400 MHz at 4.2 K. This nearly ideal behavior is very surprising because, in general, at low as well as at high temperatures, the structural variations of amorphous and partly crystalline materials tend to broaden the loss-frequency curves. 

When a signal in the radio-frequency range is to be transmitted over long distances in coaxial cables, the dielectric loss becomes particularly objectionable. The maxima in dielectric loss often parallel the maxima in mechanical loss for the same material. We expect maximum losses at transition temperatures (Figure 11.5) for both electrical and mechanical deformations. In Figure 11.6, we can see the increase in apparent main Tg (about 120°C) with increased frequency in the behavior of tan 8 for a partly crystalline material. 

The crude product separates as a solid from the reaction medium and is recovered by filtration, and it is then washed thoroughly with ether and dissolved in 350 ml 1 N HCI. Then, approximately 250 ml of the aqueous solvent is removed with a rotary evaporator and the evaporation residue combined with 125 ml methanol and filtered through decolorizing charcoal. The product is precipitated as the HCI salt by the addition of 7 parts of acetone. The resulting crystalline material is removed by filtration dried at 40°C with vacuum, and has a melting point of about 242°C and Is used without further purification. 

A mixture of 84 parts of 3,3-diphenyl-3-cyanopropyl bromide, 41 parts of 4-piperidino4-pi-peridinecarboxamide, 64 parts of sodium carbonate, a small amount of potassium iodide and 1,200 parts of anhydrous toluene was stirred, and heated under reflux for 48 hours. At the end of this time the reaction mixture was allowed to cool to room temperature, and 500 parts of water were added. The resultant precipitate was removed by filtration, and triturated with diisopropyl ether. The crystalline material thus obtained was removed by filtration, and re-crystalli2ed from 320 parts of acetone, to give 1 -(3,3-diphenyl-3-cyanopropyl)4-piperidino-4-piperidinecarboxamide, melting at about 149°C to 150°C. 

A solution of the above ester (207.8 grams) and 64.5 grams of sodium hydroxide in 80 cc of water and 600 cc of ethanol is refluxed for 9 hours. The carboxylic acid of 2-phenyl-cyclopropane is liberated with 200 cc of concentrated hydrochloric acid. The 2-phenyl-cyclopropanecarboxylic acid contains 3 to 4 parts of the trans isomer to 1 part of the cis isomer. The acid is recrystallized from hot water. The pure trans isomer comes out as crystalline material (solid) while the cis isomer stays in solution. 

The second crop of crystalline material is contaminated with a small amount of ethyl p-aminobenzoate and is usually red-orange in color. It is of sufficient purity to be used in Part B. 

In the phrase "liquid-crystalline", the "crystalline" adjective refers to the fact that these materials are sufficiently ordered to diffract an X-ray beam in a way analogous to that of normal crystalline materials. On the other hand, the "liquid" part specifies that there is frequently sufficient disorder for the material to flow like a liquid [145]. The disorder is typically in one dimension as is the case, for example, with rod-like molecules having their axes all parallel but out of register with regard to their lengths. 

By a careful fractionation of normal horse serum, involving as an essential part of the process a separation of closely related substances by the Schtitz168 foam technique, Bader, Schiitz and Stacey16 obtained a crystalline mucoprotein with high choline esterase activity. This appears to be the first mucoprotein obtained without the use of heat or alcohol, and while it is not yet claimed that the crystalline material is indeed the enzyme itself, arguments are advanced to show that the enzymic activity is closely bound up with mucoprotein structure. 

If the origin of micropores is in crystalline material e.g. zeolite in amorphous matrix, their presence can be controlled by XRD. As it is seen from Fig.4, the highest peak 111 of NaY zeolite shows observable intensity for a content of zeolite of about 5%. But if micropores are part of amorphous mesoporous material, XRD is ineffective. 

Figure 1. Cooling rate and crystallization temperatures fora variety of metallic glasses , note that modest cooling rates can result in non-crystalline materials for sizeable parts.

The fracture patterns of noncrystalline or partly crystalline, partly amorphous materials are unpredictable. Conchoidal fracture is typical of glass and yields odd-shaped flakes of various sizes. 

H is the heat given off by that part of the polymer sample which was already in the crystalline state before the polymer was heated above T. With this number H it is possible to figure out the percent crystallinity it is divided by the specific heat of melting, H, which is the amount of heat given off by a certain amount of the polymer. So the mass of crystalline material, m, follows as ... 

In CVD, solids are formed from gaseous compounds. In chemical vapour transport, a solid or solids interact with a volatile compound and a solid product is deposited in a different part of the apparatus. It is used both for preparing compounds and for growing crystals from powders or less pure crystalline material. 

An early success of quantum mechanics was the explanation by Wilson (1931a, b) of the reason for the sharp distinction between metals and non-metals. In crystalline materials the energies of the electron states lie in bands a non-metal is a material in which all bands are full or empty, while in a metal one or more bands are only partly full. This distinction has stood the test of time the Fermi energy of a metal, separating occupied from unoccupied states, and the Fermi surface separating them in k-space are not only features of a simple model in which electrons do not interact with one another, but have proved to be physical quantities that can be measured. Any metal-insulator transition in a crystalline material, at any rate at zero temperature, must be a transition from a situation in which bands overlap to a situation when they do not Band-crossing metal-insulator transitions, such as that of barium under pressure, are described in this book. 

---