A combination of analytical methods and molecular modeling calculations has provided a detailed picture of the supramolecular and microscopic structure of precipitated lipophilic carotenoids. The nanoparticles have a core/shell structure (see schematic representation) in which the particle core (120 nm) consists of a variety of molecular aggregates of different sizes, and the shell (40 nm) consists of an adsorbed gelatin layer.
A quantitative estimate is made of the increase Δτ0 of the critical resolved shear stress for the case of solid solutions containing spherical and coherent precipitates. The interaction between edge dislocations and the coherency strain fields is believed to be the strengthening mechanism. The calculation is applied to experimental measurements on Al‐Zn and CuCo alloys. For small particles (R/b < 20) the dislocations tend to cut through the precipitates, whereas for larger particles the Orowan mechanism becomes predominant.
ZUSAMMENFASSUNG:Abgeschrecktes, nahezu amorphes 6-Polyamid wurde durch Tempern (10 Miu. bis 2000Stdn.) bei 46 5 T, < 225°C kristallisiert. An diesen Proben wurden Schmelzpunkt, Schmelzwarme, spezifisches Volumen, Kristallstruktur und Langperiode gemessen.Die bei T, < 150°C gebildeten Kristalle mit y-Struktur sind so instabil, da13 ihr Schmelzpunkt mit den zur Verfugung stehenden Aufheizgeschwindigkeiten nicht ermittelt werden kann. Der Schmelzpunkt der bei T, > 190°C entstandenen Kristalle rnit iiberwiegend cc-Struktur liegt nach Messungen in Abhangigkeit von der Aufheizgeschwindigkeit je nach Tempertemperatur uud Temperdauer zwischen 208 und 250°C.Rei Proben mit a-Struktur besteht ein anderer Zusammenhang zwischen Schmelzwarme und spezifischem Volumen als bei Proben mit y-Struktur. Das spezifische Volumen va der amorpheu Bereiche von in or-Struktur kristallisierten Proben ist kleiner (0,901 cm3/g) als bei in y-Struktur kristallisierten Proben (0,917 cm3/g). Der Gleichgewichtsschmelzpunkt der a-Struktur betragt 260°C. Die freie Oberflachenenergie 0 : wurde zu 47 erg/cm2 ermittelt. Der unendlich groBe 6-Polyamidkristall mit a-Struktur besitzt eine Schmelzwarme zwischen 55 und 64 cal/g, je nachdem, welche der in der Literatur angegebenen Xxistalldichten als richtig angesehen wird. Eine genaue Kristallinitatsbestimmung kann bisher weder aus dem spezifischen Volumen noch aus der Schmelzwarme durchgefuhrt werden.In den DSC-Kurven der getemperten Proben treten oberhalb der Tempertemperatur die bekannten endothermen Vormaxima a d . Untersuchungen in Abhangigkeit von der Aufheizgeschwindigkeit und an methoxymethylierten Proben zeigen, da13 die oberhalb bzw. unterhalb T, = 160°C entstandenen Vormaxima unterschiedliche Ursachen haben. SUMMARY:Melting point, heat of fusion, specific volume, crystal structure, and X-ray small angle period of 6-Polyamide have been measured on samples annealed a t 46 5 T, 5 225°C for 10 min to 2000 hrs from the nearly amorphous quenched state.The crystals grown at T, < 150°C with y-structure are so instable, that their melting point cannot be determined within the available heating rates. Depending on annealing temperature and annealing time the zero-entropy-production melting point of cc-crystals is varied between 208 and 25OoC. The relation between heat of fusion and specific volume is different for samples with a-and y-structure. The specific volume v. of the non-crystalline regions depends on the structure of the crystals. It is smaller for samples with cc-structure (0.901 cm3/g) than for samples with y-structure (0.917 cm3/g). The equilibrium melting point of the a-structure is 260°C. For the free surface energy cz a value of 47 erg/cm2 has been determined. The infinitely large 6-polyamide crystal with a-structure has a heat *) Revidiertes Mauuskript vom 17. November 1970. 31K.-H. ILLERS und H. HABERKORN of fusion between 55 and 64 cal/g, depending on which of the different crystal densities, that have been reported in literature, will be accepted. An exact determination of crystallinity ...
SYNOPSISThe neck-like deformation process occurring in high-speed melt spinning of polyamide 66 and polyamide 6 filaments was investigated at take-up speeds of 4200 to 5500 m/min by on-line laser light scattering, thermographic contrast compensation, and wide-angle X-ray scattering ( WAXS ) measurements. New information about the onset of crystallization along the spinline was obtained by measuring simultaneously diameter and temperature profiles in the neighborhood of the neck. Crystallization rates, as a function of take-up speed, are estimated for both polyamides. Based on the present experimental results of diameter profiles, temperature profiles, and WAXS patterns, a picture of the physical mechanism responsible for the neck-like deformation of high-speed melt spun polyamides is proposed.
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