Johannes M. Kranenburg

Argon plasma sintering of inkjet printed silver tracks on polymer substrates

An alternative and selective sintering method for the fabrication of conductive silver tracks on common polymer substrates is presented, by exposure to low-pressure argon plasma. Inkjet printing has been used to pattern a silver nanoparticle ink. This resulted in conductive features with a resistivity less than one order of magnitude higher than the bulk value of silver without affecting the polymer substrate. This process may be employed in the production of conductive features with low material usage on common polymer substrates in, for example, printed electronics.

Elastic moduli for a diblock copoly(2-oxazoline) library obtained by high-throughput screening

Using depth-sensing indentation, the elastic modulus E of a diblock copoly(2-oxazoline) library was investigated in order to determine structure–property relationships. The adopted experimental procedure, dropcasting of the copolymer materials and determining the elastic modulus by depth-sensing indentation, was compatible with high-throughput experimentation. The elastic modulus of the investigated materials depended strongly on the side-group. Materials containing poly(nonyloxazoline) exhibited a lower modulus than materials without any poly(nonyloxazoline) block as poly(nonyloxazoline) was at room temperature above its glass-transition temperature Tg, while the other homopolymers in this study were glassy at room temperature. The elastic modulus also depended on the relative humidity (RH) of the testing environment; the stiffness of ethyloxazoline and methyloxazoline decreased significantly due to water absorption from the air. At lower RH, hydrogen bonding or polar interactions among the polymer chains resulted in a surprisingly high modulus for the poly(methyloxazoline). In addition, as anticipated, the elastic moduli of AB diblock copolymers were bounded by those of the A and B homopolymers, both at high and at low RH. The presented results indicate how, and to what extent, for these materials the E (and the change in E) at a given (change in) humidity can be adjusted by tailoring the composition.

Correlating the mechanical and surface properties with the composition of triblock copoly(2-oxazoline)s

The elastic moduli, surface energies, and phase morphologies of poly(2-oxazoline) triblock copolymers were investigated and compared to the corresponding homopolymers and diblock copolymers, at a constant degree of polymerization. The elastic moduli of ABA triblock copolymers were bound by those of the respective AB diblock copolymers and A homopolymers. These results show that the elastic moduli of these copolymers – obtained by instrumented indentation – depended on the interplay between phase-separation, crystallization and hygroscopicity, and can be adjusted by tailoring the composition. The surface energy strongly depended on the presence of a poly(2-nonyl-2-oxazoline) block. If such a block was present, the surface energy was reduced due to segregation of nonyl side-chains to the surface. This segregation was promoted by annealing. The crystallization of nonyl side-chains at the surface promoted the development of surface texture and an increase in surface roughness, as demonstrated by atomic force microscopy topographic imaging.

HIGH-THROUGHPUT KINETIC STUDY OF PEROXIDE CURING OF EPDM RUBBER

Abstract Mixing of EPDM and a peroxide curative via a solution route and subsequent curing were performed in a downscaled set-up. The resulting vulcanizates were characterized by a down-scaled hardness measurement and by Raman spectroscopy in a high-throughput experimentation compatible approach. The characterization results obtained on these vulcanizates agreed well with those obtained on corresponding vulcanizates prepared via conventional mill mixing. By indentation on vulcanizates cured for various curing times, a rheometer curve could be constructed. The conversion of the EPDM unsaturation and, thus, the extent of the addition reactions was quantified by Raman spectroscopy. Using both the indentation and the Raman data, the cross-link density resulting from combination reactions was estimated.