Bernd Kretzschmar

In situ Synthesis of Poly(ethylene terephthalate)/layered Silicate Nanocomposites by Polycondensation

The goal of the work presented here was to develop nanocomposites consisting of layered silicates and poly(ethylene terephthalate) (PET). Two nanocomposite preparation methods were compared: first, the usual melt compounding technique, and second, in-situ synthesis of PET in presence of different types of layered silicates. Montmorillonite (MMT) without and with organophilic modification was employed as layered silicate. In most cases, PETs with acceptable properties (molecular weight and discoloration) were synthesized in presence of different MMTs although the molecular weights of the in-situ PETs were lower than the control sample. These materials were used as masterbatch for PET nanocom-posites with 5 wt.% inorganic content. The exfoliation in both types of nanocomposites was not complete, but they showed a good distribution of clay within the polymer matrix.

The Application of Di-isocyante Modified Agro-polymer as Filler For XNBR/PA-12 Thermoplastic Elastomer Composites

Lignocelluloses industrial waste flour of olive husk powder (LCF) was utilized as reinforcement in carboxylated nitrile butadiene rubber (XNBR)/Polyamide-12 (PA-12) thermoplastic elastomer composites. To improve the bonding quality between the LCF and the blend, the powder was chemically treated by two means, the former is the treatment with toulene-2–4-diisocyanate (TDIC), and the latter is mercerization with sodium hydroxide followed by neutralization with acetic acid. The untreated and chemically treated powders were analyzed with attenuated total reflectance infrared spectroscopy (ATR-IR). The morphology of the powders before and after treatment was studied with scanning electron microscopy (SEM). The LCF reinforced composites were prepared using computerized Haake internal mixer coupled with rheometer. The processing conditions were 178°C and rotor speed of 80- round per minute for 7 min. The melt mixing process was monitored by the torque-time plastograms of the Haake internal mixer. The development of the stock temperature during the mixing process was monitored using the rheometer of Hakke internal mixer. The structural changes of the XNBR/PA-12 composites were inspected by SEM and attenuated ATR-IR spectroscopy. The influence of the modified filler on the toughness and hardness of the prepared samples are reported. The resistance of the prepared composites to water and toluene swelling are evaluated as well.

Mechanical properties of ternary blends of ABS + HIPS + PETG

The effect of a commercial styrene/butadiene/styrene-based compatibilizer (Styroflex) on the tensile and impact properties of ternary blends of poly(acrylonitrile-co-butadiene-co-styrene) (ABS), high impact poly(styrene) (HIPS) and poly(ethylene terephthalate-co-cyclohexanedimethanol terephthalate) (PETG) was investigated. The tensile yield strengths and the moduli of the blends were of similar magnitude as the parent polymers. However, notched Charpy impact properties showed significant deviations with high synergy in ABS/PETG blends and strong antagonism in HIPS/PETG blends. Addition of Styroflex improved the impact properties of all blends containing HIPS and ABS. Dynamic mechanical analysis studies confirm the phase separated nature of ABS/PETG binary blends.

Utilization of Agrowaste Polymers in PVC/NBR Alloys: Tensile, Thermal, and Morphological Properties

Poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) alloys were melt-mixed using a Brabender Plasticorder at 180∘C and 50 rpm rotor speed. Alloys obtained by melt mixing from PVC and NBR were formulated with wood-flour- (WF-) based olive residue, a natural byproduct from olive oil extraction industry. WF was progressively increased from 0 to 30 phr. The effects of WF loadings on the tensile properties of the fabricated samples were inspected. The torque rheometry, which is an indirect indication of the melt strength, is reported. The pattern of water uptake for the composites was checked as a function WF loading. The fracture mode and the quality of bonding of the alloy with and without filler are studied using electron scanning microscope (SEM).

Properties of polypropylene clay nanocomposites modified with difunctional compounds

Three commercially available adhesion promoters based on silanes were used to modify montmorillonite. The short and highly reactive 3-aminopropyltrimethoxysilane (APS) is not able to expand the silicate layers. 3-(2-aminoethyl)aminopropyltrimethoxysilane (AEAPS) and 3-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS) can be used for a cation exchange reaction in montmorillonite, but the layer distance in the modified clay material is rather low, especially for AHAPS. So mixtures with surfactants were used to modify montmorillonite. With dimethyldistearylammonium chloride as comodifier three ways of preparation of silanized organoclay were tested. Two of them lead only to a rather low content of silane adhesion promoter according to elemental analysis. After compounding with PP-g-MA a reaction of the primary amino group of the silane with PP-g-MA can be shown by IR-spectroscopy. Some samples were made in an amount sufficient for preparing composites on a Berstorff extruder and specimens were made by injection moulding. These were tested according to CAMPUS conditions showing increased mechanical properties in comparison to not silanized montmorillonite nanocomposites, although TEM pictures prove a worse distribution of clay.

Investigation of Structure and Mechanical Behavior of Polyamide 6/ZnO and Polyamide 6/Al2O3 Nanocomposites

In this work we investigate mechanical properties and structure of PA6/ZnO and PA6/Al2O3 nanocomposites to understand the effect of different nanoparticles on the polymer matrix. Mechanical experiment results show that the mechanical reinforcement effect after loading ZnO nanoparticles is better than that of loading Al2O3 nanoparticles. At 10% ZnO loading, the elastic modulus increases to about two times of that of pure PA6, and the yield stress increases about 30%. And the elongation at break has no obvious decrease even at high ZnO loading. In order to understand the reason of better mechanical reinforcement after incorporating ZnO nanoparticles, microstructure and crystallization behavior of the samples were investigated. The results indicate that the better reinforcement of mechanical properties after loading ZnO was attributed to enhanced interfacial adhesion between ZnO nanoparticles and PA6 matrix at high ZnO content.

Modification of Polysulfones by Carboxylic Acids

The modification of aromatic polysulfones (PSU) in the melt in continuous mixing aggregates (on the small-scale: twin-screw microcompounder; on the large-scale: twin-screw extruder) by low-molecular weight dicarboxylic acids is presented. Owing to the drastic conditions experienced by the melt in the extruder operating at 320 °C, chain scission of the polysulfones as well as the formation of reactive groups attached to the PSU chains was expected, using either trimellitic acid anhydride or terephthalic acid as dicarboxylic acids. However, no functional groups indicating a reaction between the PSU and the carboxylic acids were detected in the melt-processed PSU compounds. Nevertheless, the resulting thermal and mechanical properties of the PSU compounds were influenced remarkably by the carboxylic acids due to their different mixing behavior with the PSU melt. The tensile stiffness and strength of the compounds were significantly increased in comparison with the PSU reference. PSU compounds containing the trimellitic acid anhydride (at concentrations exceeding 5.7 wt.%) showed a particularly high strength at break, while all compounds had a lower toughness in comparison with the neat PSU.