Crystal mat

Single-crystal mats are obtained by precipitation and subsequent filtration on a flat surface of the polymer from dilute solution (Bassett, 1981). Individual lamellae are formed with few connections from highly dilute solutions. In such a case, the... 

Figure 4.3. Schematics of an oriented single-crystal mat of a polymer as grown from solution. (From Ingram PeterUn, 1968.)...

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Grubb et al. [43] studied this question on single crystal mats of polyethylene. The samples, previously crystallized at 80 °C, were annealed in a flow of hot helium at different temperatures above 120 °C. WAXS was observed during recrystallization by means of a vidicon detector, the time resolution being 0.3 sec. A strong decrease of the intensity of the (110) crystal reflection and therefore of the crystallinity is observed during the first few seconds of the experiment. Simultaneously a rapid in-... 

Annealing a crystal mat for 30 minutes successively at temperatures of 100°, 110°, 120°, and 130°C. led to an increase in area of the y maximum (log dec.) and a shift of this peak to higher temperatures, until the temperature found for the melt-formed specimen was reached (69). 

In one investigation, using a viscoelastometer, crystal mats of polyoxymethylene from cyclohexanol solution showed a 7-loss modulus peak at 200°K. ( 102 c.p.s.) (40), reduced in magnitude but at approximately the same temperature as that for melt-crystallized material. However, results obtained for crystals, grown at 97°C. from a 1% Delrin 500 solution in a 3 1 phenol-ethanol mixture (5), indicated that the attenuation peak for crystals suspended in methanol and the associated dielectric loss peak are at lower temperatures than that for the loss peak in melt-crystallized material, in agreement with results for polyethylene. A sample prepared by... 

Samples of poly(4-methyl-l-pentene) (P4MP1) prepared from mats of dilute solution-crystallized polymer have been investigated by NMR and dynamic mechanical techniques. Dynamic mechanical data for crystal mats of P4MP1 were obtained with a vibrating reed apparatus by J. A. E. Kail of Imperial Chemical Industries, Ltd., Plastics Division, on a... 

It is well known (66) that the a-relaxation process of crystalline polymers consists of at least two processes, referred to as ai and U2 in the order of lower temperature, respectively. The ai-process (67-77) is pronounced in melt crystallized samples and is associated with the relaxation of grain boundaries, such as dislocation of lamellae with a frictional resistance related to disordered interface layers. The magnitude of the ai-process increases with the increase in the crystal defects. The o 2-process (71,73,78-83) is pronounced in single crystal mats and is ascribed to incoherent oscillations of the chains about their equilibrium positions in the crystal lattice in which intermolecular potential suffers smearing out. The magnitude of the Q 2-process increases with the increase in the lamellar thickness and/or the degree of crystallization (39). 

The results described above for highly drawn samples of HDPe (EDR > 12) seem to be consistent with such an assumption. However, in some cases, the important role of the shear vs. extensional deformation components (JO. In extrusion of spheruiitic HOPE and the compressive force in extrusion of powders of polyethylene single crystals (21) and ultrahigh MW polyethylene (22) has been suggested. Indeed, we have shown (23) recently that single crystal mats of various poiyethyienes, which couid not be extended by tensile force below can be effectively drawn even at room temperature up to... 

T. Kanamoto, A. Tsuruta, K. Tanaka, M. Takeda, R.S. Porter, On ultra-high tensile modulus by drawing single crystal mats of high molecular weight polyethylene. Polym. J. 15(4), 327-329 (1983)... 

Olf and Peterlin and Folkes and Ward considered a number of different models in an attempt to explain the molecular motions in the range — 196°C to 20°C, which are important in as much as they relate to the interpretation of the low temperature mechanical relaxation (the /-relaxation ) in this polymer. In single crystal mats and hexatriacontane, Olf and Peterlin suggested that the best explanation for the low... 

Kanamoto, T., Tsuruta, A., Tanaka, K., Takeda, M. and Porter, R. S. Super-drawing of ultrahigh molecular weight polyethylene. 1. Effect of techniques on drawing of single crystal mats. Macromolecules 1988 21 470-7. 

Huang YL, Seo HJ, Feng Q, Yua SH (2005) Effects of divalent rare-earth ions on spectral properties of PbW04 crystals. Mat Sci Eng B Solid 121 103... 

N. Bonanos and E. P. Butler [1985] Ionic Conductivity of Monoclinic and Tetragonal Yttiia-Zirconia Single Crystals, /. Mat. Sci. Lett. 4, 561-564. 

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