The pyroelectric behavior of as-received 2-mil polyvinylidene fluoride films was studied as a function of the poling treatment. It is shown that poling induces a thermally reversible electric polarization in addition to an electric polarization which vanishes upon the first heating of the sample. Experimental evidence is given that the reversible polarization involves charge injection from the electrodes in addition to a field-induced structural change (probably the formation of oriented crystalline form I). For short poling times ([inverted lazy s] seconds) the mechanism of charge injection appears to be dominant. Initial results of the temperature and voltage dependence of the dc conductivity and of the temperature dependence of the dielectric loss at 50 and 100 Hz for unpoled and poled 2-mil polyvinylidene fluoride (PVF2) films are presented.

will be approximately 0.2 in systems where the carbonyl is isolated from similar groups along the chain and where the molecular mobility is high. In solid polymers, the quantum yield will be reduced to very low values at temperatures below the glass-transition temperature of the polymer because of the restriction in molecular mobility. We suggest that the scission mechanism in such copolymers involves the breaking of either a-8 or i3-7 carbon-carbon bonds through an intermediate transition state consisting of either a sixor a sevenmembered ring through a y-or 5-hydrogen atom. We further conclude that transfer of excitation energy along a polymer chain will be possible in systems where similar chromophores are located in adjacent positions along the backbone. When such is the case, one may expect to get substantial changes in the quantum yields for the observed photochemical processes.

SynopsisA nylon 66 composed of uniformly sized spherulites approximately 50 p in diameter was examined before and after cold drawing by light and electron microscopy of thin sections and by low-angle x-ray diffraction. Spherulites retained their identity through drawing, but the spherulites elongated less than the bulk specimen indicating that relative motion of spherulites must have occurred. The observation of dilations (0.3 p long) at interspherulitic boundaries support this contention. The thin-section electron micrographs indicated that the spherulites were composed of radiating lamellae approximately 95 A. thick. After drawing, the lamellae were preferentially oriented both parallel and perpendicular to the draw direction. Lamellae parallel to draw had thinned to approximately 70 A. while lamellae perpendicular to the draw had apparently thickened to 150 A. .Three low-angle x-ray diffraction patterns yielded quantitative agreement with the electron-micrograph data. The pattern from the undrawn nylon was a diffuse ring corresponding to a 95 A. spacing. On the drawn specimen, with the beam parallel to draw, a ring corresponding to the 150 A. spacing was obtained, while with the beam perpendicular to draw two arcs were recorded a t spacings of 70 and 150 A. The drawing was done at room temperature and proceeded by neck formation and propagation, yielding a 4: 1 draw ratio.

No abstract

Unusual morphologies have been shown to be produced in high density polyethylene near its melting point and under selective conditions of orientation and pressure existing in an Instron capillary extrusion rheometer. Points of study involve the remarkably high optical clarity and tensile moduli for the morphologies produced in these filaments. Details of the crystallization procedure are provided. The morphologies resulting from the Instron procedure have been analyzed by several different techniques. X-ray, calorimetry, microscopy and modulus data are discussed. The transparent filaments are composed of a large number of microfibers having a high degree of crystalline orienlation parallel to the capillary axis. Electron diffraction and calorimetric studies indicate that a portion of the strands have an unusually high degree of order. Structural models for the strands are also proposed. ZUSAMMENFASSUNG:Es wurde gezeigt, daB sich in Hochdrnck-Polyathylen in der Nahe der Schmelztemperatur und unter bestimmten Bedingungen in bezug auf Orientierung und Druck, wie sie im Instron-Extrusions-Kapillar-Rheometer vorliegen, ungewohnliche morphologische Strukturen ausbilden. Die bemerkenswert hohe optische Transparenz und die Spannungsmoduln der in diesen Faden vorliegenden morphologischen Gebilde waren Gegenstande der Untersuchungen. Einzelheiten des Kristallisationsverfahrens werden beschrieben. Die morphologischen Strukturen, die sich bei dem Jnstron-Verfahren" herausbilden, wurden mit Hilfe von rontgenographischen, kalorimetrischen, mikroskopischen und mechanisbhen Messungen untersucht. Die transparenten Fasern setzen sich aus einer groBen Zahl von Mikrofibrillen, die einen hohen kristallinen Orientierungsgrad parallel zur Kapillarachse besitzen, zusammen. Elektronenbeugung nnd kalorimetrische Untersuchungen zeigen, daB ein Teil der Fasern cinen ungewohnlich hohen Ordnungsgrad besitzt. Es werden Strukturmodelle fur die Fasern vorgeschlagen.