Preparation of nanocomposites by melt compounding polylactic acid/polyamide 12/organoclay at different screw rotating speeds using a twin screw extruder

This study analyzes the effect of different screw rotating speeds on the clay dispersion and mechanical properties of nanocomposites prepared by melt compounding polylactic acid (PLA) with an organoclay in a co‐rotating twin screw extruder. Polyamide 12 (PA12) was used as an additive. Two different screw rotating speeds, 65 rpm and 150 rpm, were used in this study. According to the tensile strength data, the Young's modulus of the PLA/clay nanocomposites showed improvement at a screw rotating speed of 150 rpm. The Young's modulus improved with the addition of the organoclay to PLA matrix, but decreased when PA12 was added to the PLA matrix. The tensile strengths and elongations become small by adding organoclay to PLA matrix. The tensile strengths of the PLA/organoclay nanocomposites increased for the higher screw rotating speed (150 rpm). The d‐spacing of PLA/PA12/Clay nanocomposites was independent of the addition of PA12. The size of the clay aggregates in the PLA/PA12/Clay nanocomposites is smaller than that of PLA/Clay. Furthermore, the thermal stability of the PLA/Clay nanocomposite increases with addition of PA12, while on the whole, it had little influence on the tensile properties. POLYM. COMPOS., 29:1–8, 2008. © 2007 Society of Plastics Engineers     

An optimal deep learning framework for multi-type hemorrhagic lesions detection and quantification in head CT images for traumatic brain injury

Applied Intelligence - Traumatic Brain Injury (TBI) could lead to intracranial hemorrhage (ICH), which has now been identified as a major cause of death after trauma if it is not adequately...     

Two-dimensional photonic crystal resist membrane nanocavity embedding colloidal dot-in-a-rod nanocrystals

A novel technique for the fabrication of photonic crystal (PC) nanocavities coupled with colloidal nanocrystals is presented. A waveguiding resist membrane embedding highly emitting dot-in-a-rod nanocrystals was patterned through e-beam lithography and released through wet etching process. The proposed approach makes the PC structure independent of fabrication imperfections induced by etching steps. Micro-photoluminescence spectra revealed degenerated resonant modes (Q-factor approximately 700) whose fabrication-induced spectral splitting is comparable to the full width at half-maximum of the peaks. Active nanocavities tunable from visible to infrared spectral range on GaAs or Si substrates can be easily implemented by this technique.     

Effect of screw rotation speed on the properties of polystyrene/organoclay nanocomposites prepared by a twin‐screw extruder

We discuss the effect of screw rotation speed on the mechanical and rheological properties and clay dispersion state of polystyrene (PS)/organoclay (clay) nanocomposites prepared by melt compounding with a counterrotating‐type twin‐screw extruder. Poly(styrene‐co‐vinyloxazolin) (OPS) was used as an additional material. The Young's modulus of the PS/OPS/clay nanocomposites showed the maximum value at a screw rotation speed of 70 rpm in this study. This implied the existence of an optimized screw rotation speed for the melt compounding of the polymer/clay nanocomposites. For PS/clay systems without the addition of OPS, the peak intensity from clay increased and the distance between clay platelets in the nanocomposites decreased with the screw rotation speed. On the other hand, inverse results were obtained for PS/OPS/clay systems. According to the transmission electron microscopy photographs, the PS/OPS/clay nanocomposite at 70 and 100 rpm had fully exfoliated clay platelets. The dynamic rheological properties of the PS/clay nanocomposites were almost the same as those of neat PS. On the other hand, the storage and loss moduli of the PS/OPS/clay nanocomposites at the same frequency were larger than those of the PS/clay system. On the whole, the bonding between clay platelets and PS was important for increasing the viscosity and elasticity in the melts of the PS/clay system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1165–1173, 2006     

Preparation of poly(lactic acid)/poly(ethylene glycol)/organoclay nanocomposites by melt compounding

Poly(lactic acid) (PLA)/organoclay nanocomposites were prepared by melt compounding in a co‐rotating twin screw extruder. Two types of commercialized organoclay (dimethyl benzyl stearyl ammonium ion and dimethyl distearyl ammonium ion intercalated between clay platelets named as Clay A and Clay B, respectively) and two grades of poly(ethylene glycol) (PEG) with different molecular weight (M_w = 2,000 and 300,000–500,000 named as PEG2k and PEG500k, respectively) were used in this study. The Young's modulus improved by the addition of organoclay to PLA matrix. The Young's modulus decreased with the addition of PEG to PLA/organoclay nanocomposites. The tensile strength and elongation of PLA/Clay B nanocomposites increased with the addition of PEG2k. The effect of the addition of PEG on d‐spacing of PLA/organoclay nanocomposites is dependent upon the kind of organoclay. The sizes of clay agglomerations in PLA/PEG/organoclay nanocomposites are larger than those of PLA/organoclay ones in the same organoclay. Addition of PEG to PLA/organoclay nanocomposites during melt compounding will not be useful for the preparation of PLA/organoclay having fully exfoliated clay platelets. The shear thinning properties of the nanocomposites are independent of the addition of PEG. On the whole, PEG2k is good plasticizer for PLA/organoclay nanocomposites. POLYM. COMPOS. 27:256–263, 2006. © 2006 Society of Plastics Engineers