Compounding of commercial nanocomposites usually involves the addition of viscosity enhancers such as binder resins in ink jet inks, and paints. Contrary to this, plasticizers such as process oils are added to reduce the melt viscosity and ease processability of reinforced elastomers. Nanofillers such as silica and carbon black are typically added to reinforce rubber and enhance performance of automotive tire treads. Filler dispersion has traditionally been qualitatively (indirectly) assessed by measuring the properties of reinforced elastomers. While dispersion can be quantified by examining filler agglomeration through surface roughness measurements and microscopy, the size-scale dependence for these hierarchical fillers has usually been ignored. We have recently devised a method to quantify nano-scale dispersion of fillers using Ultra small-angle X-ray scattering (USAXS) techniques. This method is advantageous since it directly links the controllable processing/compounding parameters such as the mixing speed, mixer geometry, residence time (or mixing duration), melt density, flow gap distance, and melt viscosity to nano-scale dispersion. While our previous studies have explored the impact of different processing parameters, this study specifically investigates the impact of melt viscosity on nano-scale filler dispersion in elastomer compounds. Commercially available polybutadienes with different Mooney viscosities were used in conjunction with different grades and amounts of process oils to modify the melt viscosity.

Quantitative governing equations are proposed to correlate structural features with performance as guiding principles to design porous p-Si structures for Li ion battery anodes.

Characterizing nanomaterials is challenging due to their macromolecular nature, requiring suites of physicochemical analysis to fully resolve their structure. As such, their synthesis and scale-up are notoriously complex, especially when compared to small molecules or bulk crystalline materials, which can be provided a unique fingerprint from nuclear magnetic resonance (NMR) or X-ray diffraction (XRD) alone. In this study, we address this challenge by adopting a three-step quality-by-design (QbD) approach to the scale-up of bioinspired silica nanomaterials, demonstrating its utility toward synthesis scale-up and intensification for this class of materials in general. First, we identified material-specific surface area, pore-size distribution, and reaction yield as critical quality attributes (CQAs) that could be precisely measured and controlled by changing reaction conditions. We then identified the critical process parameters (CPPs) controlling bioinspired synthesis properties, exploring different process routes, incorporating commercial reagents, and optimizing reagent ratios, comparing silica properties against original CQA values to identify acceptable limits to each CPP. Finally, we intensified the synthesis by increasing reagent concentration while simultaneously incorporating the optimized CPPs, thereby modifying the bioinspired silica synthesis to make it compatible with existing manufacturing methods. We increased the specific yield from ca. 1.1 to 38 g/L and reduced the additive intensity from ca. 1 to 0.04 g/g product, greatly reducing both synthesis cost and waste production. These results identify a need for mapping the effects of critical process parameters on material formation pathways and CQAs to enable accelerated scale-up and transition from the lab to the market.

Surface active agents are often used to improve dispersion of nanoparticles. Quantitative correlation between these surface-active molecules and nanoscale dispersion is absent from the literature partly because a quantitative measure of nanoscale dispersion does not exist. Recently, we have developed the Virial-van der Waals method to quantify dispersion in nanocomposites using virial coefficients. In this paper, the Langmuir adsorption model is used to quantify the influence of surface-active agents on nano-scale dispersion in terms of the effective second virial coefficient B2*. The impact of silane coupling agent on the nano-dispersion and silica aggregate structure in precipitated silica/SBR nanocomposites is demonstrated. It is shown that the higher viscosity SBR matrix led to a greater silica aggregate structural breakup, while lower viscosity matrix improved surface silanization. The isomeric content of the SBR, which impacts the dielectric behavior, impacted whether the system could be modeled through a mean-field or specific interactions. We earlier showed that larger aggregates improve dispersion, and this is reaffirmed in these results. After account is made for aggregate size, nano-scale dispersion improves with the addition of silane coupling agent. The behavior is well modeled using Langmuir monolayer adsorption.

In polymer nanocomposites, surface modification of silica aggregates can shield Coulombic interactions that inhibit agglomeration and formation of a network of agglomerates. Surface modification is usually achieved with silane coupling agents although carbon-coating during pyrolytic silica production is also possible. Pyrogenic silica with varying surface carbon contents were dispersed in styrene-butadiene (SBR) rubber to explore the impact on hierarchical dispersion, the emergence of meso-scale structures, and the rheological response. Pristine pyrogenic silica aggregates at concentrations above a critical value (related to the Debye screening length) display correlated meso-scale structures and poor filler network formation in rubber nanocomposites due to the presence of silanol groups on the surface. In the present study, flame synthesized silica with sufficient surface carbon monolayers can mitigate the charge repulsion thereby impacting network structural emergence. The impact of the surface carbon on the van der Waals enthalpic attraction, a∗, is determined. The van der Waals model for polymer nanocomposites is drawn through an analogy between thermal energy, kBT, and the accumulated strain, γ. The rheological response of the emergent meso-scale structures depends on the surface density of both carbon and silanol groups.

Breakup (dispersion) and distribution of nanoparticles are the chief hurdles towards taking advantage of nanoparticles in polymer nanocomposites for reinforcement, flame retardancy, conductivity, chromaticity, and other properties. Microscopy is often used to quantify mixing, but it has a limited field of view, does not average over bulk samples, and fails to address nano-particle hierarchical structures. Ultra-small-angle X-ray scattering (USAXS) can provide a macroscopic statistical average of nanoscale dispersion (breakup) and emergent hierarchical structure, as well as the distribution on the nanoscale. This work compares several common mixer geometries for carbon black-polystyrene nanocomposites. Two twin-screw extruder geometries, typical for industrial processing of melt blends, are compared with a laboratory-scale single screw extruder and a Banbury mixer. It is found that for a given mixer, nanoscale distribution increases following a van der Waals function using accumulated strain as an analogue for temperature while macroscopic distribution/dispersion, using microscopy, does not follow this dependency. Breakup and aggregation in dispersive mixing follow expected behavior on the nanoscale. Across these drastically different mixing geometries an unexpected dependency is observed for nanoscale distributive mixing (both nano and macroscopic) as a function of accumulated strain that may reflect a transition from distributive turbulent to dispersive laminar mixing as the mixing gap is reduced.

This paper presents a methodology for the robotic 3D printing of cellulose and wood shavings with bioplastics for applications in architecture, moulds, or furniture design.The material composition consists of plant fibre, binders, solvents and additives.All of the ingredients are either biodegradable or biocompatible, as in, they naturally occur in the environment.Different material compositions have been explored and tested for their extrusion behaviour, drying and curing behaviour, buildability and final product qualities, resulting in the manufacture of several case-study prototypes as a proof of concept.

This paper describes the characterization of carbon nanotube fabric or nanofabric. The nanofabric, has five fundamental properties: light weight, hydrophilic or hydrophobic, flame resistance, flexibility, and filterant. The nanofabric is formed by injecting a precursor aerosol into a high-temperature flow-through reactor. Nanofabric is collected on a drum from the exhuast. Hybrid nanofabric is synthesized by co-injection of a granulated carbon aerosol. Current fabrics used in firefighting might be supplemented with nanofabric or hybrid nanofabric to alleviate the dangers of airborne toxic chemicals and particles, along with assisting in heat management. The nanofabric survived longer in a flame test compared to traditional flame-resistant textiles.

Melt crystallized polymers display an emergent, multi-hierarchical, ordered structure made up of stacked lamellar single crystals that form fibrous or other meso structures which, in turn, form macroscopic crystallites. A dominant feature of small-angle scattering from these complex assemblies is a correlation peak associated with the stacking period. A new model-based function is proposed for small-angle scattering data from such correlated lamellar multi-hierarchical structures. Generally, routine use of scattering data has been limited to a 1-d analysis to determine the long period from Lorentz corrected data (I(q)q2 versus q). Fourier transforms of the data are sometimes used to determine the 1-d pairwise correlation function for the electron-density distribution which has been further analyzed in terms of the structure of these materials. A simple 1-d fitting model limited to infinite width 2-d sheets was introduced by Hermans (1944; Hosemann, 1950) [1,2] in the 1940s with some success. A new approach, the Unified Born-Green Function (UBG), is proposed that uses the Unified Function as adapted to correlated lamellar structures and incorporates a Born-Green description of one-dimensional correlations. The UBG fit allows quantification of the average lamellar aspect ratio, the local degree of crystallinity within a stack, quantification of the stacking versus non-stacking amorphous, and two types of disorder in addition to the stacking period and lamellar thickness. UBG can account for higher levels of structure such as crystalline domains in block copolymers and convoluted lamellar structure. The UBG fit is compared to the Hermans (1944; Hosemann, 1950) [1,2] and a hybrid-Hermans function. Fits to data sets from a wide range of polyethylene are shown ranging from molecular weight standard samples that are isothermally crystallized, to commercial HDPE quenched from the melt and a metallocene blown film sample. Several other examples from the literature are explored. It is shown that the Unified fit allows for new understanding of the impact of thermal and mechanical history, chain structure, fillers, nucleating agents, and additives on the crystalline structure and the resulting physical properties. Limitations of the UBG approach are noted.

Porous elastomers possessing gradient morphology or chemistry are needed for new applications including biomaterial interfaces, additive manufacturing, and separation membranes. However, elastomers possessing a porosity gradient are often difficult to prepare requiring slow multistep synthesis techniques. In this work, layered porosity polydimethylsiloxane (PDMS)-based polymerized high internal phase emulsions (polyHIPEs) with defined interfaces have been synthesized using one-step reactions. The total porosity, pore size, and surface area of the prepared polyHIPEs are controlled by varying the volume of aqueous dispersed phase in the emulsion. Analysis of SEM images and pore size calculations of layered porosity polyHIPEs proved the emulsion patterning method did not disrupt emulsion morphology and a clear porosity interface was maintained. Total porosity values dictate the storage moduli of the polyHIPEs, where highly porous materials possess the lowest observed moduli of similar to 70-90 kPa. Tensile testing shows that the interface between two layers is mechanically robust and does not split during elongation at break experiments. This work provides a simple technique to prepare layered porosity PDMS-based polyHIPEs having up to five tunable porosity layers with strong interfaces between the layers.

The dispersion of nanoparticles in viscous polymers is dictated by kinetics, interaction potentials between particles, and interfacial compatibility between the matrix and dispersed phases. It was previously proposed that an analogy can be made between thermally dispersed colloids and kinetically dispersed nanoparticles in viscous media when weak interactions exist between particles allowing for a mean-field description under the Ginzburg criterion such as for carbon black dispersed in polybutadiene elastomer. For these cases, the second virial coefficient can be used to quantify the quality of dispersion; additionally, the nanoscale network mesh size can be calculated, which is related to dynamic properties. However, this approach fails for nanoparticles with surface charges or other specific interactions that lead to correlations. Here, these correlated systems are investigated in the context of the mean-field systems in order to gain a comparative description of dispersion using the network mesh size and a derived virial coefficient. The physical origin of the structural parameters from the proposed model for these correlated systems is investigated.

Surface modification of model silica to enhance compatibility in nanocomposites has been widely studied. In addition to model spherical silica, several authors have investigated the impact of surface conditions on compatibility in commercial aggregated carbon black and silica. In this paper, dispersion is investigated for a series of nanocomposites produced from commercially modified fumed silica mixed with styrene butadiene rubber, polystyrene, and polydimethylsiloxane. Surface modification includes variation in surface hydroxyl content, siloxane, and silane treatment. Qualitatively, hydroxyl groups on the silica surface are considered incompatible with non-polar polymers, while methyl groups are compatible with oleophilic polymers. X-ray scattering was used to analyze the filler aggregate structure before and after dispersion, and the second virial coefficient was used to quantify nanodispersion. The content of surface moieties was determined from Fourier-transform infrared spectroscopy. It is observed that modified silica can display mean field or specific interactions as reflected by the presence of a correlation peak in x-ray scattering. For systems with specific interactions, a critical ordering concentration is observed related to the free energy change for structuring. A van der Waals model was used to model the second virial coefficient as a function of accumulated strain, yielding the excluded volume and an energetic term. The excluded volume could be predicted from the structural information, and the bound polymer layer was directly related to the surface methyl content, whereas the energetic term was found to synergistically depend on both the methyl and hydroxyl surface content.

Porous elastomeric polymers have been used in a wide range of applications because of their unique characteristics such as biocompatibility, gas permeability, thermal stability, and hydrophobic and dielectric properties. Poly(dimethyl siloxane) (PDMS), a commercially available elastomer, has also been shown to exhibit specific acoustic properties. However, the material properties were limited because of a lack of control over the chemistry used to prepare the cross-linked PDMS elastomer. Here, the synthesis of PDMS-based polymerized medium internal-phase emulsions (polyMIPEs) with tunable storage shear moduli (G') has been performed using macromolecular thiol-ene reactions. Storage shear modulus values from similar to 38 to similar to 330 kPa were achieved by changing the stoichiometric ratio of the thiol-to-ene-functionalized PDMS, whereas the porosity of the polyMIPEs was controlled by the volume of the aqueous phase used in the emulsion formulation. Very low sound velocities (similar to 40 m/s) through the porous materials were recorded using acoustic characterization. Therefore, this work provides an example of the synthesis of soft polyMIPEs with possible applications as acoustic materials.

We show that the interconnectivity of silicon crystallites determines the final mesoporosity. Applying this mechanism to bioinspired silica enabled us to produce mesoporous silicon with a capacity of 2170 mA h g−1 after 100 cycles.