Relationship Of Shear Histroy, Morphology – Microstructure And Mechanical Properties Of Micro Injection Molded Parts
The relationship of shear history, morphologymicrostructure and mechanical properties of the microscale parts was investigated based on the polypropylene parts with thickness 0.2mm and 0.5mm molded under varied injection speed. Shear rate was analyzed using Moldflow. 0.5 mm parts showed skin-core structure in the thickness direction with imperfect shish-kebab structure appeared in the transition layer between skin layer and core layer, however, the transition layer of 0.2 mm parts shows columnar crystal. The whole shear level in shear history increased with injection speed increasing for all the parts with two thicknesses. The ratio of skin layer of 0.5 mm parts decreased as the injection speed increased, which result in the decreasing of yield stress, modulus, breaking strength and elongation at break. The ratio of skin layer of 0.2 mm parts increased with injection speed increasing, and results in increasing of yield stress, modulus and breaking strength, and decreasing of elongation at break.
Morphological evolution of HDPE parts in the microinjection molding: Comparison with conventional injection molding
To compare the difference of morphological evolution of HDPE micropart and macropart, micropart with 200 μm thickness and macropart with 2000 μm thickness were prepared. The PLM images of micropart and macropart exhibited a similar “skin–core” structure, but the micropart showed a much larger fraction of orientation layer. The SEM observation of core layer of micropart featured an unoriented lamellae structure and shear layer of micropart showed a highly oriented shish-kebab structure. The 2D-WAXD patterns of shear layer of macropart indicated twisted oriented shish-kebab (KM-I) structures, however that of micropart indicated untwisted oriented shish-kebab (KM-II) structures which was firstly found in microinjection molding. The diffraction pattern of the micropart exhibited stronger azimuthal dependence than the shear layer of macropart, indicating the most pronounced orientation of HDPE chains within lamellae. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Remote estimation of nitrogen and chlorophyll contents in maize at leaf and canopy levels
a b s t r a c t Leaf and canopy nitrogen (N) status relates strongly to leaf and canopy chlorophyll (Chl) content. Remote sensing is a tool that has the potential to assess N content at leaf, plant, field, regional and global scales. In this study, remote sensing techniques were applied to estimate N and Chl contents of irrigated maize (Zea mays L.) fertilized at five N rates. Leaf N and Chl contents were determined using the red-edge chlorophyll index with R2 of 0.74 and 0.94, respectively. Results showed that at the canopy level, Chl and N contents can be accurately retrieved using green and red-edge Chl indices using near infrared (780-800 nm) and either green (540-560 nm) or red-edge (730-750 nm) spectral bands. Spectral bands that were found optimal for Chl and N estimations coincide well with the red-edge band of the MSI sensor onboard the near future Sentinel-2 satellite. The coefficient of determination for the relationships between the red-edge chlorophyll index, simulated in Sentinel-2 bands, and Chl and N content was 0.90 and 0.87, respectively.