JEC COMPOSITES MAGAZINE - Issue #41 - June 2008 - 70

Control g…/… Monitoring nanofiller dispersion/ distribution in molten polymers More information Fig. 7: Two series of four consecutive images (top to bottom) acquired by one of the CCD cameras in the dark. Left: Siliconöl M10000 (PDMS 10 Pa-s) filled with GT5700 (negative images, final concentration 6 ppm ca). The whole Visiovis is visible in the images. Right: injection of 10 ml of a masterbatch (Siliconöl M10000 filled with 0.25% wt of photo-functionalized Cloisite® 30B). Zoom on the screw profile First image processing Interpretation key: the smaller the integral standard deviation of luminosity, the more homogeneous the mixture and the more efficient the distributive mixing. Limit: integral standard deviation will never be smaller than a certain value, due to the difference of the mixture (never completely black) compared to the screw profile (always completely black). This treatment is not morphology sensitive: two images with different textures may give the same results in terms of luminosity. Second image processing Interpretation key (perfect miscibility): the lower the representative frequency, the more homogeneous the mixture and the more efficient the distributive mixing. Interpretation key (reduced miscibility): the higher the representative frequency, the finer the texture and the more efficient (even if not complete) the distributive mixing. Limit: the contrast between the mixture and the screw profile produces a Heaviside function, which corresponds to an artifactual permanent texture of the image. frequency value and plots such values as a function of the image number (i.e. the number of screw revolutions). Theoretically, a zero frequency corresponds to perfect mixture homogeneity; per contra, high frequencies reflect the presence of regular and fine textural units. In reality, it is impossible to obtain a truly zero frequency, since images have finite dimensions. If a zero frequency is obtained, it should be interpreted as a relative value. The regularly acquired on-line fluorescence spectra are useful to evaluate the temporal evolution of nanofiller dispersion by the emission signature of the fluorescent molecule used to photo-functionalize clays (Rhodamine). Any chemical and/or physical change of Rhodamine molecular environment may produce a significant change in its fluorescence emission. Clay intercalation and/or exfoliation (consequences of dispersive mixing) may be detected by identifying any emission change due to the expansion of clay interlayer space and the diffusion of polymer macromolecules into clay galleries. Fig. 8: Typical results obtained by the image processing based, respectively on the standard deviation of luminosity (left) and based on the Fourier transformation of textured images (right). Injection of 10 ml of a masterbatch containing PDMS (Siliconöl M10000, 10 Pa-s) and 0.25% wt of photofunctionalized Cloisite® 30B. Screw rotational speed 20 rpm ca highest frequencies are able to represent the finest details. The Fourier transformation highlights any regular, repetitive structure which appears in the image considered as a 2D signal, function of the two space coordinates. The anamorphosis of each picture of a given series is operated, eliminating any problem of aspect ratio of the analysed images and making each picture frequentially isotropic. The program performs the Fourier transformation of each modified image, calculates the logarithm of the squared norm, subtracts the noise calculated on a reference image, calculates the average of each frequency value and plots the averaged values as a function of the frequency. It associates to each picture of a given series the most representative average Conclusions Visiovis is an original and innovative tool that makes it possible to visualize viscous fluids flowing in a screw/barrel system. We adapted this equipment to the analysis of (nano) filler dispersion/distribution mechanisms in molten thermoplastic polymers or uncured thermoset resins, by slightly changing its configuration and performing some original clay photo-functionalization trials by cation exchange in the presence of a fluorescent molecule. Contacts: antonella.esposito@insa-lyon.fr References [1] E.T. Thostenson, C. Li, T.-W. Chou, JEC Composites Magazine / No41 May 2008

JEC COMPOSITES MAGAZINE - Issue #41 - June 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #41 - June 2008