Download or read book Crystallization of Polyethylene Under Low Gravity Conditions written by Benjamin E. Goldberg and published by . This book was released on 1992 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Properties of Crystalline Polyethylene like Materials Under Industrially Relevant Processing Conditions written by Carlos Germosen Polanco and published by . This book was released on 2021 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyethylene-like materials with in-chain acetal units ( -O-CH2-O- ) precisely spaced by long methylene runs (between 12 and 26 CH2) crystallize from the melt in four different crystallographic forms (polymorphs) depending on the depth of undercooling. Using a Fast Scanning Calorimeter (FSC) we determined the critical cooling rates needed to develop the lowest temperature polymorphs from the melt, the mesomorphic-like disordered and hexagonal structures. The crystallization kinetics of high-temperature polymorphs, Forms I and II were obtained by classical DSC, and the crystallization kinetics of the low-temperature polymorphs, disordered, and hexagonal have been studied in this work by FSC. Isothermal crystallization studies in a wide range of temperatures revealed minima in the temperature gradient of the overall crystallization rates at all transition temperatures between polymorphs. The minima in the crystallization rates and heat of fusion are attributed to differences in nucleation barrier between polymorphs, and effects of self-poisoning. There is a step increase of melting temperature with increasing structural stability and a continuous increase in melting during annealing at a fixed crystallization temperature. The disordered structure and hexagonal crystals are metastable and upon annealing transform to the next stable phase as shown by a change in WAXD patterns. These kinetics studies serve to identify processing rates and properties of sustainable polyethylene-like materials crystallized at industrially relevant conditions.

Download or read book Crystallization and Melting of Polyethylene Under Pressure written by Theodore Davidson and published by . This book was released on 1968 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: The crystallization conditions which lead to extended-chain polyethylene under elevated pressure were elucidated further. The dependence of polyethylene density on crystallization pressure on slow cooling was extended up to 6980 bars. No further improvement of crystal perfection or extension of polymer chains were observed. At 5000 bars the temperature of crystallization was varied between 170 to 270C. Temperatures between 195 and 225C were found suitable for crystallization of extended chain polyethylene. A time sequence at 200C and 5000 bar revealed some insight in the formation of extended chain polyethylene. It is thought to involve a two step process of nucleation of folded chain lamellae, followed by solid state chain extension. High pressure differential thermal analysis apparatus has been developed for measurement up to 3700 bar. Folded as well as extended chain crystals of polyethylene were analyzed. Only the extended chain crystals show an initial increase in melting point in accord with the Clausius Clapeyron equation. (Author).

Download or read book Polyethylene Crystallized from the Melt Under Elevated Pressure written by Bernhard Wunderlich and published by . This book was released on 1963 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyethylene of the linear, low pressure type has been crystallized under pressure (up to 5400 atm.) from the melt. Crystallization conditions of constant supercooling and constant cooling rates were employed. The resulting solid was analyzed at atmospheric pressure. In contrast to solution crystallization under pressure above 2000 atm. extended chain lamellae of increasing thickness become dominant (see also preceding article). These show a maximum melting point of 140 C and in this research, densities of up to 0.994. Com bining these data on large crystals with the experimental maximum melting temperatures and thickness data on low and atmospheric pressure crystallized lamellae yields a surface free en ergy of91 ergs/sq cm for folded chain lamellae crystallized at low pressure. (Author).

Download or read book Microgravity Crystallization of Macromolecules An Interim Report and Proposal for Continued Research written by Benjamin E. Goldberg and published by . This book was released on 1986 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Melting and Crystallization of Polyethylene written by Bernhard Wunderlich and published by . This book was released on 1966 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extended chain polyethylene crystals yield on fracturing a striated surface. By statistical analysis it is shown that the striations are random and no compelling reason for assumption of interior grain boundaries. The rough fracture surface starts melting at 100 C or lower, 40 deg below the equilibrium melting point. The interior is unaffected by this annealing process. Measurements on micron-thin slices of extended chain crystals were carried out and showed less superheating before melting than large crystals and a decreased heat of fusion in the high temperature region. This supports a melting mechanism which calls for melting starting from chain ends or folds. The surface reorganization process is shown to be a two step process, melting followed by recrystallization into folded chain lamellae. The epitaxial lamellae thus grown are analyzed with respect to frequency of occurrence and fold length. From the instability of the rough surface it is concluded that under normal crystallization conditions, extended chain nuclei would be unstable.

Download or read book Pressure Induced Crystallization in Polyethylene written by S. Matsuoka and published by . This book was released on 1959 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Isothermal Crystallization of Polyethylene Under Uniaxial Extension written by Thomas Michael Remec and published by . This book was released on 1983 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Annealing and Crystallization of Polyethylene Under High Pressure written by Dennis Victor Rees and published by . This book was released on 1970 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystallization and Morphologies of Linear Low Density Polyethylene and Its Blends with High Density Polyethylene written by Marsha Stalker Bischel and published by . This book was released on 1997 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineered Materials Abstracts written by and published by . This book was released on 1995-07 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystallization of IPS and HDPE Under Non isothermal Conditions written by Spencer Yew Chye Chew and published by . This book was released on 1990 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Research Technology 1999 written by and published by DIANE Publishing. This book was released on with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Crystallization Conditions and Temperature on the Polymorphic Forms of Polyethylene written by J. G. Fatou and published by . This book was released on 1964 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental evidence (using wide-angle X-ray and dilatometric techniques) is presented to indicate development of a second crystalline form as a result of further crystallization from the melt, and the temperature interval covering its formation and disappearance. Three fractionated samples of polyethylene of viscosity average molecular weights 12 500, 425 000 and 1 000 000 and an unfractionated sample of Marlex 50 of molecular weight 180 000 were used. The extra reflections reported were not observed with rapidly cooled samples. (Author).

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1997 with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Convective Effects on Protein Crystal Growth Analysis and Experiments written by Jer-Sheng Lee and published by . This book was released on 1993 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: