Joamin Gonzalez-Gutierrez

Development of highly-transparent protein/starch-based bioplastics

Striving to achieve cost-competitive biomass-derived materials for the plastics industry, the incorporation of starch (corn and potato) to a base formulation of albumen and glycerol was considered. To study the effects of formulation and processing, albumen/starch-based bioplastics containing 0-30 wt.% starch were prepared by thermo-plastic and thermo-mechanical processing. Transmittance measurements, DSC, DMTA and tensile tests were performed on the resulting bioplastics. Optical and tensile properties were strongly affected by starch concentration. However, DMTA at low deformation proved to be insensitive to starch addition. Thermo-mechanical processing led to transparent albumen/starch materials with values of strength at low deformation comparable to commodity plastics. Consequently, albumen biopolymers may become a biodegradable alternative to oil-derived plastics for manufacturing transparent packaging and other plastic stuffs.

Powder Injection Molding of Metal and Ceramic Parts

Powder injection molding (PIM) is a technology for manufacturing complex, precision, netshape components from either metal or ceramic powder. The potential of PIM lies in its ability to combine the design flexibility of plastic injection molding and the nearly unlimited choice of material offered by powder metallurgy, making it possible to combine multiple parts into a single one (Hausnerova, 2011). Furthermore, PIM overcomes the dimensional and productivity limits of isostatic pressing and slip casting, the defects and tolerance limitations of investment casting, the mechanical strength of die-cast parts, and the shape limitation of traditional powder compacts (Tandon, 2008).

Atomistic Modelling of Confined Polypropylene Chains between Ferric Oxide Substrates at Melt Temperature

The interactions and conformational characteristics of confined molten polypropylene (PP) chains between ferric oxide (Fe2O3) substrates were investigated by molecular dynamics (MD) simulations. A comparative analysis of the adsorbed amount shows strong adsorption of the chains on the high-energy surface of Fe2O3. Local structures formed in the polymer film were studied utilizing density profiles, orientation of bonds, and end-to-end distance of chains. At interfacial regions, the backbone carbon-carbon bonds of the chains preferably orient in the direction parallel to the surface while the carbon-carbon bonds with the side groups show a slight tendency to orient normal to the surface. Based on the conformation tensor data, the chains are compressed in the normal direction to the substrates in the interfacial regions while they tend to flatten in parallel planes with respect to the surfaces. The orientation of the bonds as well as the overall flattening of the chains in planes parallel to the solid surfaces are almost identical to that of the unconfined PP chains. Also, the local pressure tensor is anisotropic closer to the solid surfaces of Fe2O3 indicating the influence of the confinement on the buildup imbalance of normal and tangential pressures.

Effect of the printing bed temperature on the adhesion of parts produced by fused filament fabrication

ABSTRACT For parts produced by fused filament fabrication (FFF) the adhesion between the first printed layer and the printing bed is crucial, since it provides the foundation to the subsequent layers. Inadequate adhesion can result in poor printing quality or destroyed bed surfaces. This study aims at understanding and optimising the adhesion process for parts produced by FFF. The consequences of varying printing bed temperatures on the adhesion of two commonly used printing materials on two standard bed surfaces were investigated by means of an in-house built adhesion measurement device and complemented by contact angle measurements. This study shows a significant increase in adhesion forces, when printing parts at a bed temperature slightly above the glass transition temperature of the printing material.

Optimisation of the Adhesion of Polypropylene-Based Materials during Extrusion-Based Additive Manufacturing

Polypropylene (PP) parts produced by means of extrusion-based additive manufacturing, also known as fused filament fabrication, are prone to detaching from the build platform due to their strong tendency to shrink and warp. Apart from incorporating high volume fractions of fillers, one approach to mitigate this issue is to improve the adhesion between the first deposited layer and the build platform. However, a major challenge for PP is the lack of adhesion on standard platform materials, as well as a high risk of welding on PP-based platform materials. This study reports the material selection of build platform alternatives based on contact angle measurements. The adhesion forces, investigated by shear-off measurements, between PP-based filaments and the most promising platform material, an ultra-high-molecular-weight polyethylene (UHMW-PE), were optimised by a thorough parametric study. Higher adhesion forces were measured by increasing the platform and extrusion temperatures, increasing the flow rate and decreasing the thickness of the first layer. Apart from changes in printer settings, an increased surface roughness of the UHMW-PE platform led to a sufficient, weld-free adhesion for large-area parts of PP-based filaments, due to improved wetting, mechanical interlockings, and an increased surface area between the two materials in contact.

Additive Manufacturing of Metallic and Ceramic Components by the Material Extrusion of Highly-Filled Polymers: A Review and Future Perspectives

Additive manufacturing (AM) is the fabrication of real three-dimensional objects from metals, ceramics, or plastics by adding material, usually as layers. There are several variants of AM; among them material extrusion (ME) is one of the most versatile and widely used. In MEAM, molten or viscous materials are pushed through an orifice and are selectively deposited as strands to form stacked layers and subsequently a three-dimensional object. The commonly used materials for MEAM are thermoplastic polymers and particulate composites; however, recently innovative formulations of highly-filled polymers (HP) with metals or ceramics have also been made available. MEAM with HP is an indirect process, which uses sacrificial polymeric binders to shape metallic and ceramic components. After removing the binder, the powder particles are fused together in a conventional sintering step. In this review the different types of MEAM techniques and relevant industrial approaches for the fabrication of metallic and ceramic components are described. The composition of certain HP binder systems and powders are presented; the methods of compounding and filament making HP are explained; the stages of shaping, debinding, and sintering are discussed; and finally a comparison of the parts produced via MEAM-HP with those produced via other manufacturing techniques is presented.

Rheology and mechanical properties of fats: Second Edition

Abstract Rheology is a part of mechanics that studies the deformation and flow of matter in response to an applied stress. The rheological and mechanical properties of fat materials arise directly from their composition and how these components are structurally organized. The rheological properties displayed by a given fat system depend strongly on the physical state of the material. An understanding of rheological properties and how they are measured is an important consideration for improving the quality of fat products and improving the efficiency of their manufacturing process. This chapter examines various constitutive models, especially the finite element method, and various tests, which are used to study the rheological properties of fats.

New Methodology for Steady-State Friction Measurements of Granular Materials Under Pressure

Flow of granular material during processing, handling and transportation strongly influences the quality of the final product and its cost, that is why it is important to measure flow properties of granular materials. Flowability of granular materials depends on the characteristics of the material and on the conditions at which flow is occurring. In this paper a new methodology is introduced to measure friction between granular materials under pressure induced with uniaxial compression. Apparatus also allows analysis of conditions at which granular material starts to flow when exposed to uniaxial compressive load, i.e., zero-rate flowability. We call the apparatus the Granular Friction Analyzer (GFA).

Mechanical Properties of Extensively Recycled High Density Polyethylene

In the plastics industry it has been common practice to mechanically recycle waste material arising from a production. However, mechanical recycling affect material mechanical properties and consequently quality of the end products; therefore it needs to be quantified.

Selection of appropriate polyoxymethylene based binder for feedstock material used in powder injection moulding

Polyoxymethylene (POM) has found applications as a binder material in Powder Injection Moulding (PIM) due to its ability to depolymerize rapidly under acidic conditions. Such ability represents an advantage during the binder removal step of PIM. However, currently available POM has high viscosity that can complicate the injection moulding process of parts with complex geometry. For this reason it is necessary to investigate methods of lowering the viscosity of POM-based binders, but without affecting their solid mechanical properties (i.e. creep compliance). In this investigation, the addition of a low molecular weight polymer, and the reduction of the average molecular weight of POM were investigated as possible ways of decreasing the viscosity of PIM binders. The addition of the low molecular weight additive (WAX) caused a small decrease in the viscosity of the POM-based binder and a small increase in its solid creep compliance. On the other hand, lowering the average molecular weight of POM caused a large decrease in viscosity, but also an acceptable increase in creep compliance. Therefore, by selecting an appropriate molecular weight of POM, it is possible to improve the performance of POM-based binders for PIM.