No abstract

There is need for developing novel conductive polymers for Digital Light Processing (DLP) 3D printing. In this work, photorheology, in combination with Jacobs working curves, efficaciously predict the printability of polyaniline (PANI)/acrylate formulations with different contents of PANI and photoinitiator. The adjustment of the layer thickness according to cure depth values (Cd) allows printing of most formulations, except those with the highest gel point times determined by photorheology. In the working conditions, the maximum amount of PANI embedded within the resin was ≃3 wt% with a conductivity of 10−5 S cm−1, three orders of magnitude higher than the pure resin. Higher PANI loadings hinder printing quality without improving electrical conductivity. The optimal photoinitiator concentration was found between 6 and 7 wt%. The mechanical properties of the acrylic matrix are maintained in the composites, confirming the viability of these simple, low-cost, conductive composites for applications in flexible electronic devices.

Bio-based polymeric nanocomposites (NCs) with enhanced electrical conductivity and rigidity were obtained by adding multi-walled carbon nanotubes (CNTs) to a commercial bio-based polyamide 4,10 (PA410). Two different types of commercial CNTs (Cheap Tubes and Nanocyl NC7000 TM ) and two different preparation methods (using CNTs in powder form and a PA6-based masterbatch, respectively) were used to obtain melt-mixed PA410/CNT NCs. The effect of the preparation method as well as the degree of dispersion and aspect ratio of the CNTs on the electrical and mechanical properties of the processed NCs was studied. Superior electrical and mechanical behavior was observed in the Nanocyl CNTs-based NCs due to the enhanced dispersion and higher aspect ratio of the nanotubes. A much more significant reduction in aspect ratio was observed in the Cheap Tubes CNTs than in the Nanocyl CNTs. This was attributed to the fact that the shear stress applied during melt processing reduced the length of the CNTs to similar lengths in all cases, which pointed to the diameter of the CNTs as the key factor determing the properties of the NCs. The PA6 in the ternary PA410/PA6/CNT system led to improved Young's modulus values because the reinforcing effect of CNTs was greater in PA6 than in PA410.

No abstract

Three series of aliphatic random copolycarbonates, poly(heptane-co-dodecane carbonate) P7C-P12C, poly(butane-co-dodecane carbonate) P4C-P12C and poly(butane-co-heptane carbonate) P4C-P7C, were synthesized by two-step polycondensation process. The organocatalyst 4-(dimethylamino) pyridine (DMAP) was used for the first time to prepare copolycarbonates, as an alternative to metal catalysts, to avoid the toxicity of the remaining catalysts impurities that are difficult to remove after synthesis. Differential scanning calorimeter studies demonstrated the isodimorphic character of the copolycarbonates showing pseudoeutectic points and the crystallization in a wide composition range. Wide angle X-ray scattering (WAXS) results displayed changes in crystallographic plane spacings possibly due to the isodimorphic behavior of the systems. Two double crystalline copolymers were obtained, i.e., 85/15 P4C-P12C and 80/20 P7C-P12C, as they correspond to pseudo-eutectic compositions. Remarkably, for the 80/20 P7C-P12C copolycarbonate, we found a novel behavior. This copolymer exhibits both coincident crystallization and coincident melting during non-isothermal DSC runs. However, WAXS revealed that the material is double crystalline as it contains crystals from P7C-rich and P12C-rich phases. This is the first example of a double crystalline polymeric material that exhibits a single crystallization and a single melting peak, in spite of being double crystalline. Comparing the results obtained for the 3 series of copolycarbonates, we can conclude that it is easier to incorporate a shorter repeating unit chain segment in a crystal formed by a larger repeating unit chain segment.

In this research, the effect of maleic anhydride-grafted styrene-ethylene/butylenestyrene (SEBS-g-MAH) compatibilizer on different properties of polycarbonate and poly(acrylonitrile-butadiene-styrene) (PC/ABS) blends was investigated. For this purpose, blends of PC and ABS at different ratios, without and with varying concentrations of compatibilizer, were prepared by melt compounding in a co-rotating twin-screw extruder followed by injection molding. The effectiveness of the compatibilizer was investigated by studying the microstructure and the mechanical, thermal, and rheological properties of the blends. It was found that the addition of the compatibilizer increases tensile strength, modulus, elongation at break, impact strength, complex viscosity, and thermal stability. This effect was noted at a loading of 1 wt% of compatibilizer, where enhanced interactions between the PC and ABS can be seen. Rheological methods, based on dynamic viscoelastic tests, allowed us to distinguish between emulsion-like and cocontinuous morphologies and allowed an insight into the effect of the compatibilizer on the interfacial tension.

Compatible polymer blends of polypropylene (PP) with an amorphous polyamide (aPA) were obtained through reactive compatibilization by adding 20% maleic anhydride-modified copolymer (PP-g-MA) to the blends. The blends were made up of a pure PP phase and an aPA-rich phase where very small amounts of PP were detected. The dispersed phase particle size decreased considerably indicating that compatibilization occurred. Young's modulus of the compatibilized blends increased with respect to that of the uncompatibilized ones. The compatibilized blends were highly ductile, and the impact strength also improved, proving that compatibilization occurred under a broad range of experimental conditions.

Lactide-valerolactone copolymers have potential application in the packaging sector. Different copolymers were synthesized, and the kinetics of the copolymerization reactions and the microstructure of the copolymers were analysed. Lactide showed higher reactivity than valerolactone which leads to composition drift through the reaction. Thermal, mechanical and barrier properties of the selected copolymers were studied. Overall, the incorporation of valerolactone results in copolymers with higher ductility than poly(lactide) with intermediate water and oxygen permeability which makes these materials appropriate candidates for use in the packaging sector.