The morphology of polymer nanocomposites is usually characterized by various methods like X-ray diffraction (XRD) or transmission electron microscopy (TEM). In this work, a new approach for characterizing nanocomposites is developed: the results of small angle x-ray scattering, on-line extensional rheometry (level of melt strength) and Young's modulus out of tensile test are correlated with those of near infrared (NIR) spectroscopy. The disadvantages of the common characterization methods are high costs and very time consuming sample preparation and testing. In contrast, NIR spectroscopy has the advantage to be measured inline and in real time directly in the melt. The results were obtained for different aggregate states (NIR spectroscopy and on-line rheotens test in melt state, tensile test, and XRD in solid state). Therefore, important factors like crystallization could not be considered. Nevertheless, this work demonstrates that the NIR-technology is perfectly suitable for quantitative in-line characterization. The results show that, by the installation of a NIR spectrometer on a nanocomposite-processing compounder, a powerful instrument for quality control and optimization of compounding process, in terms of increased and constant quality, is available.

Structural characterization in polymer nanocomposites is usually performed using X-ray scattering and microscopic techniques, whereas the improvements in processing and mechanical properties are commonly investigated by rotational rheometry and tensile testing. However, all of these techniques are time consuming and require quite expensive scientific equipment. It has been shown that a fast and efficient way of estimating the level of reinforcement in polymer nanocomposites can be performed by melt extensional rheology, because it is possible to correlate the level of melt strength with mechanical properties, which reflect both the 3D network formed by the clay platelets/polymer chains as well as final molecular structure in the filled system. The physical network made of silicate filler and polymer matrix has been evaluated by X-ray diffraction and transmission electron microscopy. Extensional rheometry and tensile testing have been used to measure efficiency of the compatibilizer amount in a polypropylene-nanoclay system.

In this study, different strategies to improve the mechanical properties of physically foamed high-density polylactic acid sheets were examined to produce polylactic acid foam sheets with tailor-made mechanical properties. The first part was the determination of the effect of different blowing agents (CO 2 and N 2 ) on the foam morphology. The second part of the study was the modification of the formulation. For this purpose, both a linear and a branching chain extender and a thermoplastic elastomer were used to improve the elongational properties (tensile modulus and strain at break) of the polylactic acid foam sheets. Additionally, the effect of the addition of cellulose fibers on the foam morphology and the mechanical properties was investigated. All experiments were carried out on a laboratory flat-film line. This extrusion line consists of a 30-mm single-screw extruder attached with a 250-mm flat sheet die. The results show a strong influence of the material formulation on the mechanical properties of the high-density foam sheets. Both the mechanical properties and foam morphology could be improved by the right material formulation. The addition of the thermoplastic elastomer leads to a better foam morphology and also to a reduced brittleness of the foam sheets. Furthermore, it could be demonstrated that cellulose fiber can be used as a nucleating agent for polylactic acid but causes a further decrease in the strain at break.

Layered silicates as nanoscale fillers have a great potential in improving polymer material properties. Depending on the composite structure (agglomerated, intercalated, or exfoliated) a significantly higher level of reinforcement of the virgin polymer can be achieved with a very small amount of filler. The morphology of the composites is usually characterized by XRD and microscopic methods (e.g., transmission electron microscopy). But the level of reinforcement of nanocomposites is not always proportional to morphology (delamination level of the silicate layers). A new approach for characterizing the material reinforcement level as a consequence of melt quality is to correlate the results of extensional rheometry (level of melt strength) with those of near infrared (NIR) spectroscopy. The advantage of the NIR technique is the suitability for in-line implementation by using quartz based optics and optical fibers for the signal transfer from the measuring probe to the NIR spectrometer. The presented results show a direct correlation between the reinforcement level determined by rheotens measurements and the data analyzed from off-line NIR measurements. The results of the chemometric analysis of the NIR data shows that this in-line capable optical method provides quantitative information on the quality of the nanocomposite. V

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