Jan Kurt Walter Sandler

Carbon-nanofibre-reinforced poly(ether ether ketone) composites

Poly(ether ether ketone) nanocomposites containing vapour-grown carbon nanofibres (CNF) were produced using standard polymer processing techniques. Evaluation of the mechanical composite properties revealed a linear increase in tensile stiffness and strength with nanofibre loading fractions up to 15 wt% while matrix ductility was maintained up to 10 wt%. Electron microscopy confirmed the homogeneous dispersion and alignment of nanofibres. An interpretation of the composite performance by short-fibre theory resulted in rather low intrinsic stiffness properties of the vapour-grown CNF. Differential scanning calorimetry showed that an interaction between matrix and the nanoscale filler could occur during processing. Such changes in polymer morphology due to the presence of a nanoscale filler need to be considered when evaluating the mechanical properties of such nanocomposites.

Crystallization of Carbon Nanotube and Nanofiber Polypropylene Composites

A variety of semicrystalline isotactic polypropylene composites containing carbon nanotubes and nanofibers were produced by melt and solution techniques. The effect of the nanofillers on the crystallization process was investigated by transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry. Under the processing conditions applied in this study, the surfaces of the carbon nanomaterials act as nucleation sites in bulk samples and highly oriented composite films. This conclusion is confirmed by the calculation of Avrami exponents and, in particular, by direct microscopy evidence.

Carbon-nanofibre-reinforced poly(ether ether ketone) fibres

Nano-reinforced fibres were spun from a semicrystalline high-performance poly(ether ether ketone) containing up to 10 wt% vapour-grown carbon nanofibres using conventional polymer processing equipment. Mechanical tensile testing revealed increases in nanocomposite stiffness, yield stress, and fracture strength for both as-spun and heat-treated fibres. X-ray and differential scanning calorimetry analyses were performed in order to investigate both the orientation of nanofibres within the polymer matrix and the matrix morphology. The carbon nanofibres were found to be well aligned with the direction of flow during processing. Significantly, the degree of crystallinity of the poly(ether ether ketone) matrix was found to increase with the initial addition of nanofibres although the crystal structure was not affected. The measured increase in composite tensile modulus is compared to injection-moulded nanocomposite samples made from the same blends. The results highlight the need to characterise the matrix morphology when evaluating nanocomposite performance and hence deducing the intrinsic properties of the nanoscale reinforcement.

A Novel and Effective Synthetic Approach to 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) Derivatives

DOPO and its derivatives generally exhibit an outstanding performance as flame retardants in various polymers. Starting from trivalent 10-alkoxy-10H-9-oxa-10-phosphaphenanthrenes, a broad range of DOPO derivatives was synthesized via transesterification with aliphatic alcohols and subsequent Michaelis-Arbuzov rearrangement using catalytic amounts of p-toluenesulfonic acid methylester. Due to the considerable differences in the nature of the alcohols employed, several procedures for processing them are presented.

Mechanical and Thermal Properties of CNT and CNF Reinforced Polymer Composites

In this research study carbon nanotubes and carbon nanofibres were investigated as possible reinforcements to improve the mechanical and thermal properties of several polymer matrix systems. A range of polymer matrices were examined and include polyvinyl alcohol, poly(9‐vinyl carbazole) and polyamide. To compare production methods, polymer composite films and fibres were produced. It was found by adding various mass fractions of nanofillers, that both the Young’s modulus and hardness increased dramatically for both films and fibres. In addition, the thermal behaviour was seen to be strongly dependent on the nanofillers added to the polymer matrices.

Rheological, mechanical and tribological properties of carbon-nanofibre reinforced poly (ether ether ketone) composites

Poly(ether ether ketone) nanocomposites containing vapour-grown carbon nanofibres (CNF) were produced using standard polymer processing techniques. At high shear rates no significant increase in resin viscosity was observed. Nevertheless, the addition of the CNFs results in a higher melt strength at 360°C. Electron microscopy confirmed the homogeneous dispersion and alignment of nanofibres in the polymer matrix. Evaluation of the mechanical composite properties revealed a linear increase in tensile stiffness and strength with nanofibre loading fractions up to 15 wt% whilst matrix ductility was maintained up to 10 wt%. An interpretation of the composite performance by short-fibre theory resulted in rather low intrinsic stiffness properties of the vapour-grown CNF. Differential scanning calorimetry was used to investigate crystallization kinetics and degree of crystallinity. The CNFs were found not to act as nucleating sites. Furthermore, unidirectional sliding tests against two different counterpart materials (100Cr6 martensitic bearing steel, X5CrNi18-10 austenitic stainless steel) were performed. The carbon nanofibres were found to reduce the wear rate of PEEK significantly.

Properties of Segmented Block Copolymers in PEEK/PSU Blends

As a method of compatibilization of immiscible polyether ether ketone (PEEK)/polysulfone (PSU) blends, the addition of segmented PEEK/PSU block copolymers based on amorphous bisphenol A-containing PEEK was studied. This approach was evaluated for blends consisting of PEEK and PSU homopolymers with different molecular weights and different amounts of compatibilizers (segmented PEEK/PSU block copolymers and reactive end-functionalized PEEK and PSU oligomers). The compatibilizers were added under varying melt-processing conditions and effectively allowed the homopolymers to interact with the segmented block copolymers in the blend. The influence of the compatibilizers on the phase behavior was examined in both binary and ternary blends. Interactions in the amorphous phase, which effectively induce an enhancement of the toughness properties of the final product, could be detected.

The influence of melt elongational properties on the morphology of PES cellular materials

Rheotens melt elongational experiments were performed to evaluate polyethersulfone with regard to its foamability. The effect of polymer molecular weight was correlated with the resulting foam cell morphology achieved under identical processing conditions in a batch process. It appears, that the melt strength of the polyethersulfone governs the average cell size, cell size distribution, as well as cell wall rupture during expansion and the corresponding compressive properties of the foam. These effects were further verified by a variation of the blowing agent content for polyethersulfone with a given molecular weight.

On the friction and wear of carbon nanofiber–reinforced PEEK–based polymer composites

: In the context of establishing novel polymer nanocomposites for successful industrial use, this chapter is aimed at providing a fundamental overview of comprehensive research regarding carbon nanofiber (CNF)-reinforced poly(ether ether ketone) (PEEK) composites for demanding tribological applications. Following a summary overview describing the potential of nanoscale additives for tribological systems in general, the intrinsic structure–property relationships of CNFs are discussed in order to set the frame for the subsequent experimental results regarding their use in PEEK. As demonstrated, successful PEEK–nanofiber composites have been developed, showing a clear enhancement in mechanical properties while minimizing other detrimental effects commonly observed with such nanocomposites. These nanocomposites also reveal a significant beneficial effect on the wear behavior of PEEK under dry sliding conditions. In addition to relating the observed enhancements in the tribological performance to the underlying microstructures and properties of the nanocomposites, evidence for a further optimization of such systems by combining the nanoscale filler with conventional tribological additives and reinforcements such as carbon fibers is provided. Lastly, based on the promising results regarding the wear behavior of such hybrid systems, the performance of advanced nanocomposite hybrid materials for an intended industrial tribological application is introduced and discussed.

CHAPTER 8 - On the friction and wear of carbon nanofiber–reinforced PEEK–based polymer composites

Abstract In the context of establishing novel polymer nanocomposites for successful industrial use, this chapter is aimed at providing a fundamental overview of comprehensive research regarding carbon nanofiber (CNF)–reinforced poly(ether ether ketone) (PEEK) composites for demanding tribological applications. Following a summary overview describing the potential of nanoscale additives for tribological systems in general, the intrinsic structure–property relationships of the CNFs are discussed To set the frame for the subsequent experimental results regarding their use in PEEK. As demonstrated, successful PEEK–nanofiber composites have been developed, showing a clear enhancement in mechanical properties while minimizing other detrimental effects commonly observed with such nanocomposites. These nanocomposites also reveal a significant beneficial effect on the wear behavior of PEEK under dry sliding conditions. In addition to relating the observed enhancements in the tribological performance to the underlying microstructures and properties of the nanocomposites, evidence for a further optimization of such systems by combining the nanoscale filler with conventional tribological additives and reinforcements such as carbon fibers is provided. Lastly, based on the promising results regarding the wear behavior of such hybrid systems, the performance of advanced nanocomposite hybrid materials for an intended industrial tribological application is introduced and discussed.