By means of differential calorimetric and X-ray examinations it was shown that poly(buty1ene terephthalate) (PBT) and bisphenol-A-polycarbonate (PC) are only compatible in the melt if they stay in the melt for a short period of time. During mixing in the melt, transesterification begins and block copolymers are formed. A characteristic glass transition temperature is observed for each individual blend. Butylene terephthalate (BT)-blocks are crystallizable; however, with an increasing share of bisphenol-A-carbonate (BPAC) the specific melting enthalpy of the BT-blocks decreases. Within copolymers with a high BPAC content, the BPAC segments crystallize considerably faster than in pure PC. By means of diffraction measurements with synchrotron radiation, the mechanism of stress-induced a-P-modification change in pure PBT and in block copolymers with high BT-contents could be explored.
ZUSAMMENFASSUNG:Differentialkalorimetrische und rdntgenographische Messungen ergeben, dal3Poly(butylenterephtha1at) (PBT) und Bisphenol-A-Polycarbonat (PC), wenn sie aus einer gemeinsamen LZjsung gefallt werden, unvertraglich sind. In der Schmelze beginnt wahrend des Durchmischens der Komponenten Umesterung. Es bilden sich Blockcopolymere, die einen Glasubergang rnit einem fur jede Zusammensetzung charakteristischen T,-Wert zeigen. Die Butylenterephthalat (BT)-Blocke in den Copolymeren sind kristallisierfahig; jedoch wird ihre spezifische Schmelzenthalpie rnit zunehmendem Bisphenol-A-carbonat (BPAC)-Massenanteil kleiner. In den Copolymeren rnit hohen BPAC-Massenanteilen kristallisieren die BPAC-Segmente erheblich schneller als im reinen PC. Mit Hilfe von Rontgenbeugungsuntersuchungen rnit Synchrotronstrahlen konnte der Mechanismus fur die spannungsinduzierte a-P-Modifikationsumwandlung im reinen PBT und in den Blockcopolymeren rnit hohem BT-Gehalt aufgeklart werden.
Die Haupt‐ und Seitenkettenkristallinität bei den isotaktischen Poly(1‐alkyläthylen)en vom Poly(1‐dodecyläthylen) bis zum Poly(1‐eicosyläthylen) wurden thermoanalytisch und röntgenographisch untersucht. Die DSC‐Kurven der aus der Schmelze abgeschreckten Proben zeigen 3 Umwandlungspeaks 1. Ordnung. Bei niedrigen Temperaturen liegt in den Proben eine Modifikation vor, bei der die Seitenketten dicht gepackt parallel angeordnet sind. Erwärmt man die Proben, so findet eine Modifikationsumwandlung statt. Es bildet sich eine Modifikation aus, bei der die Hauptketten Helixkonformation annehmen und die Seitenketten rhombisch kristallisieren. Bei den höheren homologen Poly(1‐alkyläthylen)en überwiegt mit zunehmender Anzahl von CH2‐Gruppen in den Seitenketten die Seitenkettenkristallinität.
Cooling slowly from the melt and annealing at 250 K for a month isotactic polyhexylethylene becomes partially crystalline. The degree of crystallinity, calculated according to the method of Hermans and Weidinger, is 0.3. The wide‐angle x‐ray diffraction diagram shows seven reflections, not completely independent of one another. These x‐ray data do not allow an exact determination of the structure. The main chins possibly form quaternary helices (e. g., 4/1 or 7/2 helices) and the side chains are arranged in triclinic structure. The unit cell may be monoclinic: a ∼ 0.56 nm, b ∼ 3.8 nm, c ∼ 0.76 nm (in case of a 4/1 helix), β ≃ 97° The melting temperature is 278 K and the heat of fusion amounts to 30 J/g.
Polyamide-6 (PA-6) and polyamide-4 (PA-4) doped with alkali halides were investigated by X-ray diffraction, thermal analysis, infrared and far infrared spectroscopy at various temperatures (10 K-300 K). The solubility of the alkali halides in PA-4 is better than in PA-6. Small ions are molecularly dispersed in PA-6 and PA-4. Alkali ions are coordinated to the oxygen, halide ions to the nitrogen of the amide group. The degree of crystallinity of the polyamides depends on the concentration of the alkali halides and the ion radii. Alkali halides stabilize modifications of the polyamides with not fully extended chains. In polyamides crystallized from the melt some alkali halides stabilize the y-modification or similar structures. The modification is nearly independent of the alkali halide concentration and will not be destroyed by washing out the alkali halides. If the polyamides are crystallized from formic acid, alkali halides promote a pleated sheet structure with antiparallel chains. The factor group of the layer is D, , indicated by a low temperature splitting of the % vibration modes.
Isotactic poly(1 -eicosylethylene) shows three polymorphic modifications. The orthorhombic modification I is formed during melt crystallization at a cooling rate 4<2,5K.s-'. The dimensions of the unit cell are calculated to be a = 0,75 nm, b = 8,s nm and c =0,67 nm. The heat of fusion is 145 J . g-', the melting point is 363 K. The monoclinic modification I1 is crystallized from the polymer solution (a=0,53nm, b=10,8nm, c=0,77nm, /3=94"). The heat of fusion amounts to 120J.g-', the melting point is 356 K. Modification 111 is formed during rapid quenching of the melt. The side-chains crystallized closely packed in layers. Modification 111 shows no main-chain crystallinity. The heat of fusion is 40 J . g-I, the melting point is 348 K. The crystal field splitting in the Raman spectrum of modification
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