Low Thermal Expansion Machine Frame Designs Using Lattice Structures

In this work, we investigated tessellating cellular (or lattice) structures for use in a low thermal expansion machine frame. We proposed a concept for a lattice structure with tailorable effective coefficient of thermal expansion (CTE). The design is an assembly of two parts: a lattice outer part and a cylindrical inner part, which are made of homogenous materials with different positive CTEs. Several lattice design variations were investigated and their thermal and mechanical performance analysed using a finite element method. Our numerical models showed that a lattice design using Nylon 12 and ultra-high molecular weight polyethylene could yield an effective in-plane CTE of 1 × 10−9 K−1 (cf. 109 × 10−6 K−1 for solid Nylon 12). This paper showed that the combination of design optimisation and additive manufacturing can be used to achieve low CTE structures and, therefore, low thermal expansion machine frames of a few tens of centimetres in height.

Volumetric fusion of graphite-doped nylon 12 powder with radio frequency radiation

Purpose Additive manufacturing (AM) of thermoplastic polymers for powder bed fusion processes typically requires each layer to be fused before the next can be deposited. The purpose of this paper is to present a volumetric AM method in the form of deeply penetrating radio frequency (RF) radiation to improve the speed of the process and the mechanical properties of the polymer parts. Design/methodology/approach The focus of this study was to demonstrate the volumetric fusion of composite mixtures containing polyamide (nylon) 12 and graphite powders using RF radiation as the sole energy source to establish the feasibility of a volumetric AM process for thermoplastic polymers. Impedance spectroscopy was used to measure the dielectric properties of the mixtures as a function of increasing graphite content and identify the percolation limit. The mixtures were then tested in a parallel plate electrode chamber connected to an RF generator to measure the heating effectiveness of different graphite concentrations. During the experiments, the surface temperature of the doped mixtures was monitored. Findings Nylon 12 mixtures containing between 10% and 60% graphite by weight were created, and the loss tangent reached a maximum of 35%. Selective RF heating was shown through the formation of fused composite parts within the powder beds. Originality/value The feasibility of a novel volumetric AM process for thermoplastic polymers was demonstrated in this study, in which RF radiation was used to achieve fusion in graphite-doped nylon powders.

Characterization of polymeric biomedical balloon: physical and mechanical properties

Tubes from nylon 12 and Pebax 6333 resins were produced using an extrusion process. The extruded tubes were used to produce balloons for angioplasty applications. The tubes were stretched using blow molding process to produce balloons. Melt rheology behavior for nylon 12 and Pebax were studied and nylon 12 showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes and the balloons were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that nylon material is more sensitive to molecular orientation when stretched compared to Pebax material. Melting behavior for the tubes and balloons were investigated using dynamic scanning calorimetry (DSC). The melting temperature shifted to higher temperatures when the tubes are stretched into balloons and the shift was more pronounced for Pebax balloon than nylon. Morphology of Pebax balloon surface revealed a hybrid structure consisting of hard segments dispersed in soft segments and amorphous phases. The hard segments are crystallized polyamides that are biaxially oriented in the balloon with higher molecular orientation in the radial direction compared to axial direction. This resulted in a higher tensile strength along the radial direction compared to axial for the balloons. Dynamic mechanical analyzer (DMA) tests showed that the glass transition temperature of the nylon tubes shifted to higher temperatures (from 51 to 82 °C) during the balloon forming process, which means the nylon becomes stiffer and less flexible when formed into a balloon.

Full Generic Qualification of Nylon 12 Carbon Fiber Composite for Dynamic Thermoplastic Composite Pipe and Hybrid Flexible Pipe Applications

Composite structures are used as corrosion insensitive load bearing reinforcement in dynamic Thermoplastic Composite Pipe (TCP) and Hybrid Flexible Pipe (HFP) applications. The qualification of such structures can follow different strategies: product level versus material characterization. DNVGL-ST-F119 proposes a generic knowledge-based approach based on a testing pyramid. The pyramid allows a generic material characterization for a large number of conditions. Testing of dedicated specimens in constant media exposure measures the actual properties and changes of the material. Regression data is obtained for end-of-life properties. Simulations can be conducted using these properties to determine performance of the product in any state and condition and validate any load cases through classical stress combination. The characterization for VESTAPE® Nylon 12 Carbon Fiber thermoplastic composite (CF-PA12) covers all failure mechanisms for matrix, fiber and interface in static, dynamic and stress rupture mode for virgin, fully hydrocarbon saturated and aged to end of life in saturated condition. Each condition assessment is carried out in complete temperature dependency for subzero, room temperature, intermediate and maximum use temperature of 176°F (80°C). Fatigue testing covers runtimes of 106 cycles whereas stress rupture assessment exceeds 12,500h which corresponds to almost 1.5 years. With dense data populations for both regression curves and static test results the coefficient of variation is controlled. All characterization logic and data are analyzed for validity and certified by the official body of the DNV-GL. The material characterization enables simulation of a variety of application designs in predictive engineering and a simplified study is made for a dynamic gas injection jumper to demonstrate relevant occurring load cases. Utilizing all data and approaches allows to define the overall application envelope of the material. For the case of the thermoplastic composite of CF-PA12 it covers static flowlines, dynamic jumpers, service lines up to dynamic risers in sour crude service up to 176°F (80°C). The knowledge-based approach allows for economic design in engineering cases without compromising safety.

A Facile Method Combined with Acetic Acid Modification and Electroless Plating to Fabricate Copper-plated Nylon 12 Powder for Antistatic Coating

Metal particle could deposited on Nylon 12 (PA12) surface using electroless plating with excellent interface and distribution, but the use of noble metal as catalytic site would increase the process cost and restrict its application. In this work, we employed a facile technology combined with acetic acid etching and electroless copper plating to prepare Cu/PA12 composite powder, and it used as conductive filler for antistatic coating was also studied. Results manifested defects (hole and amorphous structure) and amide group established on etched PA12 surface, which would facilitate the destruction of the [Cu-EDTA] structure, and then the reduction of REDOX barrier. As a result, Cu and Cu2O particles deposited on its surface. The downward trend of volume resistivity of antistatic coating appeared the rule of slow-fast-slow. The lowest volume resistivity was about 105 ohm�cm. This means that the dependable technology has great potential application in preparing metal/polymer composite material at a low cost.

Preparation and selective laser sintering of nylon-12 coated copper powders

Purpose The purpose of this paper is to prepare metal/polymer composite materials prepared by additive manufacturing (AM) technology. Design/methodology/approach The effect of sintering parameters including laser power, scanning speed and slice thickness on strength and accuracy of selective laser sintering (SLS) parts were analyzed experimentally. Then, the laser sintering mechanism of nylon-12 coated copper was discussed through analyzing the interfacial reaction of nylon-12 and copper. The SLS parts were infiltrated with epoxy resin to meet the strength requirements of injection molding. Findings In this study, mechanical mixed nylon-12/copper and nylon-12 coated copper composite powders were investigated and compared as SLS materials. An effective dissolution–precipitation method was proposed to prepare nylon-12 coated copper powders with better processing and mechanical properties. The bending strength and modulus of fabricated parts after infiltration with epoxy reach 65.3 MPa and 3,200 MPa, respectively. Originality/value The composite materials can be used in the manufacture of injection molds with a conformal cooling channel for the production of common plastics in prototype quantities, showing a broad application prospect in rapid tooling.

Freshwater alga Raphidocelis subcapitata undergoes metabolomic changes in response to electrostatic adhesion by micrometer-sized nylon 6 particles

Nylon powders are a type of microplastic (MP) used in personal care products such as cosmetics and sunscreens. To determine the effects of nylon polymers on freshwater microalgae, we investigated the effects of two types of micrometer-sized nylon polymers, i.e., powdered nylon 6 (Ny6-P) and nylon 12 (Ny12), and four other micrometer-sized MPs, i.e., low-density polyethylene, polyethylene terephthalate, polystyrene, and ultra-high-molecular-weight polyethylene, on the microalga Raphidocelis subcapitata. The results showed that Ny6-P inhibited R. subcapitata growth more than the other MPs; R. subcapitata growth was inhibited by 54.2% with 6.25 mg/L Ny6-P compared with the control. Ny6-P in the culture media adhered to R. subcapitata cells electrostatically, which may have disrupted growth and photosynthetic activity. Metabolomic analysis revealed that many metabolites related to the amino acid catabolic pathway and γ-glutamyl cycle were induced, which might trigger responses to avoid starvation and oxidative stress. Our study provides important information on the effects of Ny6-P on algae in freshwater environments.

Freshwater alga Raphidocelis subcapitata undergoes metabolomic changes in response to electrostatic adhesion by micrometer-sized nylon 6 particles

Nylon powders are a type of microplastic (MP) used in personal care products such as cosmetics and sunscreens. To determine the effects of nylon on freshwater microalgae, we investigated the effects of two types of micrometer-sized nylons, i.e., powdered nylon 6 (Ny6-P) and nylon 12 (Ny12), and four other micrometer-sized MPs, i.e., low-density polyethylene, polyethylene terephthalate, polystyrene, and ultra-high-molecular-weight polyethylene, on the microalga Raphidocelis subcapitata. The results showed that Ny6-P inhibited R. subcapitata growth more than the other MPs; R. subcapitata growth was inhibited by 54.2% with 6.25 mg/L Ny6-P compared with the control. Ny6-P in the culture media adhered R. subcapitata cells electrostatically, which disrupted growth and photosynthesis. Metabolomic analysis revealed that many metabolites related to the amino acid catabolic pathway and γ-glutamyl cycle were induced, which might reflect responses to avoid starvation and oxidative stress. Our study provides important information on the effects of Ny6-P on algae in freshwater environments.

Assessing the Conversion of Various Nylon Polymers in the Hydrothermal Liquefaction of Macroalgae

Marine macroalgae offers a promising third generation feedstock for the production of fuels and chemicals, avoiding competition with conventional agriculture and potentially helping to improve eutrophication in seas and oceans. However, an increasing amount of plastic is distributed into the oceans, and as such contaminating macroalgal beds. One of the major plastic contaminants is nylon 6 derived from discarded fishing gear, though an increasing amount of alternative nylon polymers, derived from fabrics, are also observed. This study aimed to assess the effect of these nylon contaminants on the hydrothermal liquefaction of Fucus serratus. The hydrothermal liquefaction (HTL) of macroalgae was undertaken at 350 °C for 10 min, with a range of nylon polymers (nylon 6, nylon 6/6, nylon 12 and nylon 6/12), in the blend of 5, 20 and 50 wt.% nylon to biomass; 17 wt.% biocrude was achieved from a 50% blend of nylon 6 with F. serratus. In addition, nylon 6 completely broke down in the system producing the monomer caprolactam. The suitability of converting fishing gear was further demonstrated by conversion of actual fishing line (nylon 6) with the macroalgae, producing an array of products. The alternative nylon polymer blends were less reactive, with only 54% of the nylon 6/6 breaking down under the HTL conditions, forming cyclopentanone which distributed into the biocrude phase. Nylon 6/12 and nylon 12 were even less reactive, and only traces of the monomer cyclododecanone were observed in the biocrude phase. This study demonstrates that while nylon 6 derived from fishing gear can be effectively integrated into a macroalgal biorefinery, alternative nylon polymers from other sectors are too stable to be converted under these conditions and present a real challenge to a macroalgal biorefinery.