The aim of this work was to develop new bioplastic compounds from wheat gluten, biobased plasticizers (glycerol, octanoic acid and 1,4-butanediol), and microalgal biomass as a filler. The effects of the composition on tensile properties, thermal stability, and water sensitivity were investigated. Microalgal biomass was added with the selected quantities: 10, 20, and 30 per hundred parts (php). Mechanical mixing of the components, i.e., gluten, plasticizer, and microalgae, was followed by molding in a hot press. Microlgal filler improved mechanical properties of the plasticized gluten material: in samples plasticized with 1,4-butanediol, 30 php of biomass increased the tensile modulus by nearly one order of magnitude, from 36.5 MPa to 273.1 MPa, and it also increased the tensile strength from 3.3 MPa to 4.9 MPa. The introduction of microalgal biomass slightly increased the surface sensitivity against water: 30 php of biomass reduced the water contact angle from 41° to 22° in samples plasticized with glycerol, but the biomass lowered the overall water absorption kinetics for material with each plasticizer. Microalgal biomass proved therefore to be an interesting sustainable resource with which to develop materials based on gluten, in particular to increase the mechanical properties of the compounds without reducing thermal stability or water resistance.
This paper deals with the additive manufacturing of metakaolin-based geopolymers and with the use of microalgal biomass from wastewater treatment plants as biofiller in this kind of cementitious material. The study was developed following the evolution stages of the material, which was prepared and printed as a soft paste and then hardened thanks to an inorganic polymerization reaction (geopolymerization). Thus, the characterization techniques adopted encompassed rheometry, mechanical tests performed on the hardened material, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Microalgal biomass addition, evaluated in this study at 1, 3 and 5 php with respect to the powder weight, affected both the properties of the fresh and of the hardened material. Regarding the former aspect, biomass reduced the yield stress of the pastes, improving the ease of the extrusion process, but potentially worsening the ability to build structures in height. When hardened, geopolymers containing microalgae showed mechanical properties comparable to the unfilled material and a microstructure characterized by smaller pores. Finally, a printing test was successfully performed with a larger printer to assess the feasibility of producing large-scale structures. Taking into account these results, this study demonstrates the possibility of using microalgal biomass as biofiller in geopolymers for additive manufacturing.
The research described in this study establishes whether measured physical material parameters could be used as a predictor of the human subjective response to the tactile and visual stimuli characteristics of aluminium coatings surfaces. Twenty surfaces were used consisting of four uncoated aluminium substrates and four different type of coatings applied on each of the four uncoated substrates. Forty volunteers (20 female and 20 males) were asked to rate the surfaces using semantic differential scales.The results suggest that coatings obtained by matt polyurethane which contains a fine dispersion of silica micro-particles has the capability to veil the effect of the manufacturing process of the aluminium substrates on both the felt slipperiness and felt roughness. The dynamic coefficient of friction was found to be a good predictor of the felt slipperiness with a negative power law exponent of 0.86 (R 2 = 0.85), confirming that greater friction is associated with less felt slipperiness. The physical gloss was also found highly negatively correlated (R 2 = 0.87) with the felt slipperiness of the tactile stimuli suggesting that glossier surfaces could be mostly perceived sticky. These results provide useful suggestions relating to the sensory perception and experience of materials, helpful for the industrial and product design in numerous application fields such as automotive and electronics industry.
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