Mesophase formation and its thermal transition in the stretched glassy polylactide revealed by infrared spectroscopy
(4979-4984) Polymer 52 #21 (2011)
Lv et al of the East China Institute of Technology and Tianjin University, China, studied the structural development in the glassy polylactide during stretching and subsequent heating by Fourier transform infrared spectroscopy.  Only when molecular chains in the amorphous phase approach their finite extensibility beyond a critical strain of about 1, accompanied by remarkable conformational ordering, can cohesive mesophase with certain molecular ordering be brought out to trigger strain-induced crystallization.  Upon heating cohesive mesophase endures melting during glass transition region where an endothermic peak is observed, and the extent of melting relies on its initial thermal stability and is in particular affected by the subsequent advent of strain-induced crystallization.  (RDC 10/6/2011)

Controlling Cavitation of Semicrystalline Polymers during Tensile Drawing
(7273–7287) Macromolecules 44 #18 (2011)
Rozanski and Galeski of the Polish Academy of Sciences, Poland, concluded that cavitation is initiated in amorphous phase from homogeneous nuclei that are fluctuations of free volume.  It seems that introducing a liquid penetrant into interlamellar regions should lead to filling free volume pores and to a decrease of intensity of cavitation. Polyethylene, polypropylene, and polyamide were selected for experiments. Modification of amorphous phases of polymers was conducted by introduction chloroform and hexane for polyolefins and water for polyamide. Chosen liquids penetrate amorphous phase of polymers but do not influence their crystalline phase. Samples whose amorphous phase had been filled with low molecular weight molecules remained transparent up to rupture without evidencing cavitation during tensile drawing. It appears that blocking cavitation in crystallizing polymers is possible by removing homogeneous cavitation nuclei by filling the free volume of amorphous phase of the material with low molecular weight liquids. The type of liquid is not relevant, except that it should not dissolve polymer crystals. The above observation is valid for polyethylene, polypropylene, and polyamide; however, it seems that other crystallizing polymers should also reflect similar dependencies.  By infusing low molecular weight penetrants, one may control cavitation. (RDC 10/4/2011)

Stretching-induced percolation in polyvinylidene fluoride and nickel composites
(2368–2373)   Journal of Applied Polymer  Science 120 #4 (2011)
Yu and Li of Ningbo University, China, stretched polyvinylidene fluoride (PVDF) and nickel (Ni) composites at 120°C.  There was an abrupt increase in dielectric constants and conductivities with stretching ratio called the stretching-induced percolation.  When SR was near the threshold, dielectric constants showed 17 times improvement and conductivities displayed four to five orders of magnitude enhancement at 100 Hz in low Ni fraction composites.  (RDC 3/21/2011)

Cavitation during Drawing of Crystalline Polymers
(1–9)Macromolecular Symposia 298 #1 (2010)
Galeski and Rozanski of the Polish Academy of Sciences, Poland reviewed cavitation in low molecular weight liquids under tension and in crystalline polymers during tensile drawing.  The amorphous phase of crystalline polymers at temperature above its glass transition temperature differs markedly from low molecular weight liquids. Cavitation in polymers seemingly is not of a heterogeneous character, unlike in unpurified low molecular weight liquids. The most probable reasons are: confinements of amorphous layers between crystalline lamellae and macromolecular chain entanglements, the factors that are absent in low molecular weight liquids.  (RDC 2/25/2011)