Andreas Noll

Thermo-molded self-healing thermoplastics containing multilayer microreactors

Here in this work we propose a thermally molded self-healing thermoplastic polymer containing a multilayer microcapsule-type microreactor. The latter consists of an isolated monomer and catalyst system. As the first proof-of-concept composites, commercial plastics polystyrene (PS) filled with glycidyl methacrylate (GMA)-loaded microreactors are reported. The specially designed structure of the microreactors enables them to be robust enough to survive the thermal processing already widely used in the plastics industry, like melt mixing under shear and compression molding. Upon damage of the composites and microreactors, the GMA monomer is released to the cracks and its atom transfer radical polymerization is triggered when it passes by the catalyst layer. The polymerized GMA serves as a macromolecular adhesive, which not only fills up the interstitial gap of the cracks but also is anchored to the sub-surface of the matrix forming mechanical interlocking, offering satisfactory healing efficiency at room temperature. By changing the species of healing monomer, catalyst and wall substances, the microreactors can meet the versatile requirements of different polymers, so that the approach is provided with broad applicability.

Poly-para-phenylene-copolymers (PPP) for extrusion and injection moulding Part 1 – molecular and rheological differences

Abstract Poly-para-phenylene (PPP) is at room temperature the stiffest and hardest thermoplastic polymer known. Two types of PPP (PR-120 as an extrusion and PR-250 as an injection moulding grade) are commercially available. In this paper, their thermal and rheological performance was evaluated as a function of their molecular characteristics. The lower viscosity of the PR-250 material is in agreement with its lower average molecular weight Mw, and this material exhibited a slightly higher glass transition temperature and thermal stability than material PR-120. The latter, on the other hand, possessed a much higher stiffness, as revealed by dynamic mechanical thermal analysis tests.

Poly-para-phenylene-copolymers (PPPs). Part 3: scratch and wear resistance

Abstract Two types of poly-para-phenylene (PR-120 as an extrusion and PR-250 as an injection moulding grade) were previously investigated with regard to their thermal, rheological and mechanical properties. In the last part of this paper series, the tribological properties, in particular the scratch resistance and wear under abrasive, sliding and rolling conditions, were evaluated as a function of the materials’ molecular characteristics. In general, PR-120 exhibited a better scratch and wear resistance, which is expected due to its higher molecular weight. However, other factors also seem to play an important role, although convincing correlations between the scratch and wear behaviour and the morphological and mechanical properties could not be found so far. All the properties tested were mirrored to those of polyetheretherketone and other polymers tested under similar conditions.

Poly-para-phenylene-copolymers (PPP) for extrusion and injection moulding. Part 2: mechanical behaviour

Abstract Two types of poly-para-phenylene-copolymers (PR-120 as an extrusion and PR-250 as an injection moulding grade) are commercially available. In this paper, their mechanical properties were evaluated as a function of their molecular characteristics. The higher viscosity PR-120 possesses a higher strength, modulus and hardness, which is in agreement with its lower molecular flexibility compared to PR-250. On the other hand, the latter version shows a better fracture toughness. All tests were carried out at room temperature.

Effective multifunctionality of poly(p-phenylene sulfide) nanocomposites filled with different amounts of carbon nanotubes, graphite and short carbon fibers

The aim of this work was the fundamental research on multifunctional properties of poly(p-phenylene sulfide) (PPS) composites using commercially available multi wall carbon nanotubes (MWNT) in combination with microscale short carbon fibers (SCF) and graphite (Gr) as fillers. Systematic combinations of the three fillers were investigated to explore the efficiency of the respective single fillers in combined systems. It could be demonstrated that MWNT are the most effective filler for realizing electrical conductivity, whereas SCF are favorable to improve mechanical and tribological properties. Gr is good for improving the tribological properties too. The multimodal filled composites resulted in the best property profile. Existing synergies between SCF and MWNT regarding electrical conductivity, especially near to the percolation threshold, were modeled.

Crystallization Behaviour of TiO2 Nanoparticle Reinforced Polypropylene

Composites of isotactic polypropylene (iPP) with different TiO2 nanoparticle loads (0.5 vol.%, 2 vol.% and 4 vol.%) were compounded by optimized twin screw extrusion. The crystallization behaviour of these semicrystalline nanocomposites was examined by differential scanning calorimetry (DSC), scanning electron microscope (SEM) and polarized optical light microscope (POM) combined with a hot stage module to pursue in-situ the structure development. Wet chemical etching was applied to highlight morphological details like spherulites and lamellar structures for SEM observations. An obvious influence of TiO2-nanoparticles on the crystallization could be verified.