Moduli Stabilization Research Articles

Polarity effects of asphaltene subfractions on the stability and interfacial properties of water-in-model oil emulsions

Asphaltenes can adsorb at the interface between crude oil and produced water and form a defensive interfacial layer to stabilize emulsions. This paper details the effects of the polarities of asphaltene subfractions on emulsion stability and interfacial properties. Asphaltene subfractions with different polarities were first obtained by a solvent-precipitation method, followed by the characterization of their molecular structures and dispersive states in the model oil. The results show that the subfractions with lower polarity contain a higher proportion of aliphatic groups, which benefits oil compatibility, thus leading to a better dispersive state and weaker aggregation tendency. Then, the stabilities of the emulsions prepared with these subfractions were explored at different concentrations. The emulsion stability worsens as polarity weakens at 500 ppm. However, at a concentration of 5000 ppm, the emulsion stability increases first with a polarity decrease, reaches a peak, and then decreases. The adsorption behavior and interfacial structural strength are detected through dynamic interfacial tension and dilational viscoelastic experiments. The subfractions with lower polarities exhibit better dispersion in the model oil, allowing for higher rates of absorption. The dilational modulus and emulsion stability depend on the migration rate and surface coverage of the subfractions and share similar trends with changes in polarity. With an increase in the polarity of the subfractions, the surface coverage and migration rate have reverse contributions on the dilational modulus and emulsion stability. Additionally, the contributions become more obvious after asphaltene aggregation.

Talc filled polylactic-acid biobased polymer composites: tensile, thermal and morphological properties

Global warming due to human activities (i.e., burning fossil fuels) has led to many issues, such as extreme weather (storm or drought) and rise in sea level making low land uninhabitable. One of the solutions to mitigate the global warming is to promote the use of biobased material. In this work, various dosage of talc powder ranged from 5, 10, 30 and 40 wt% were added into polylactic acid (PLA) to form biobased polymer composites. The biobased polymer composite has the potential to replace fossil-based polymer for sustainable packaging application. The PLA/talc composites were prepared by using melt blending method and compressed into thin sheet for characterisation test. The effect of talc content on the thermal properties and tensile performance of the PLA composites were investigated. Scanning electron microscope was used to study the fracture surface of the composites and the dispersion of talc powder in the matrix. Results showed that the addition of talc ranged from 5 to 30 wt% can enhance the Young’s modulus and thermal stability of the composites but there is no improvement in tensile strength and elongation at break due to poor interfacial adhesion. The addition of talc beyond 30 wt% (i.e., 40 wt%) did not show improvement in thermal stability because at high talc content, the formation of agglomerate and voids allows the oxygen to diffuse into the matrix which lead to decomposition process.

Heterotic instantons for monad and extension bundles

We consider non-perturbative superpotentials from world-sheet instantons wrapped on holomorphic genus zero curves in heterotic string theory. These superpotential contributions feature prominently in moduli stabilization and large field axion inflation, which makes their presence or absence, as well as their functional dependence on moduli, an important issue. We develop geometric methods to compute the instanton superpotentials for heterotic string theory with monad and extension bundles. Using our methods, we find a variety of examples with a non-vanishing superpotential. In view of standard vanishing theorems, we speculate that these results are likely to be attributed to the non-compactness of the instanton moduli space. We test this proposal, for the case of monad bundles, by considering gauged linear sigma models where compactness of the instanton moduli space can be explicitly checked. In all such cases, we find that the geometric results are consistent with the vanishing theorems. Surprisingly, linearly dependent Pfaffians even arise for cases with a non-compact instanton moduli space. This suggests some gauged linear sigma models with a non-compact instanton moduli space may still have a vanishing instanton superpotential.

Fabrication of Oleogels via a Facile Method by Oil Absorption in the Aerogel Templates of Protein-Polysaccharide Conjugates.

In this study, a novel and facile method was developed to fabricate oleogels. The alginate/soy protein conjugates with excellent emulsifying activity and emulsion stability were prepared via Maillard reaction and freeze-dried to form the aerogel templates, which were then immersed in corn oil within 6 h to induce the oleogels. Compared with the alginate and soy protein solutions, the viscosity and elastic modulus G' of the conjugate solutions increased, indicating the formation of a new macromolecule and strengthened gel network from Maillard reaction. The conjugate aerogels presented the morphology of serious aggregation and conglutination but the higher elastic modulus and better thermal stability, due to the increasing covalent interactions. These aerogel templates showed a good oil absorption of up to 10.89 g/g aerogel and holding capacity of 40%. The resulting oleogels loaded with thymol showed excellent antimicrobial activities against Staphylococcus aureus and Escherichia coli. This work suggests that the fabrication of oleogels is not limited to the choice of existing oleogelators but from a wide variety of protein-polysaccharide conjugates to form the aerogel templates for oil absorption.

Orbital localization error of density functional theory in shear properties of vanadium and niobium.

It is believed that the density functional theory (DFT) describes most elements with s, p, and d orbitals very well, except some materials that have strongly localized and correlated valence electrons. In this work, we find that the widely employed exchange-correlation (XC) functionals, including local-density approximation (LDA), generalized gradient approximation (GGA), and meta-GGA, underestimate the shear modulus and phase stability of V and Nb greatly. The advanced hybrid functional that is usually better for correlated systems, on the other hand, completely fails in these two simple metals. This striking failure is revealed due to the orbital localization error in GGA, which is further deteriorated by hybrid functionals. This observation is corroborated by a similar failure of DFT+U and van der Waals functionals when applied to V and Nb. To remedy this problem, a semiempirical approach of DFT+J is proposed, which can delocalize electrons by facilitating the on-site exchange. Furthermore, it is observed that including density derivatives slightly improves the performance of the semilocal functionals, with meta-GGA outperforms GGA, and the latter is better than LDA. This discovery indicates the possibility and necessity to include higher-order density derivatives beyond the Laplacian level for the purpose of removing the orbital localization error (mainly from d orbitals) and delocalization error (mainly from s and p orbitals) completely in V and Nb so that a better description of their electronic structures is achieved. The same strategy can be applied to the other d electron system and f electron system.

Cellulose nanofiber/elastomer composites with high tensile strength, modulus, toughness, and thermal stability prepared by high-shear kneading

An aqueous TEMPO-oxidized cellulose nanofiber (TOCN) dispersion and aqueous hydrogenated acrylonitrile-butadiene rubber (H-NBR) latex were mixed with or without applying high shear forces. The TOCN/H-NBR mixtures containing TOCN volume ratios of 0–10.0% were then converted to crosslinked composite sheets with peroxide between the H-NBR molecules by hot-pressing. When the aqueous TOCN/H-NBR mixtures were pretreated with high shear forces, the crosslinked TOCN/H-NBR composites exhibited concomitant high tensile strength, high tensile modulus, high ductility, high storage modulus, and high dimensional stability to temperature. These properties are better than those of H-NBR composites containing single-walled carbon nanotubes or carbon black at the same filler volume ratio. In the crosslinked TOCN/H-NBR comosites prepared with high shear fodrces as pretreatment, electron microscopy images showed that the TOCN elements were homogeneously dispersed in the H-NBR matrix without forming aggregates. Thermal and pulsed NMR analyses of the solvent-extracted residue of the non-crosslinked TOCN/H-NBR composite indicated that characteristic nanostructures formed in the TOCN/H-NBR interfacial phases, which may cause the excellent mechanical and thermal properties of the composite.

Preparation and characterization novel dioctyl terephthalate blended polyvinyl alcohol-composite films incorporated with the graphene oxide and silver nanoparticles

Dioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.

Logarithmic loop corrections, moduli stabilisation and de Sitter vacua in string theory

We study string loop corrections to the gravity kinetic terms in type IIB com- pactifications on Calabi-Yau threefolds or their orbifold limits, in the presence of D7-branes and orientifold planes. We show that they exhibit in general a logarithmic behaviour in the large volume limit transverse to the D7-branes, induced by a localised four-dimensional Einstein-Hilbert action that appears at a lower order in the closed string sector, found in the past. Here, we compute the coefficient of the logarithmic corrections and use them to provide an explicit realisation of a mechanism for Kähler moduli stabilisation that we have proposed recently, which does not rely on non-perturbative effects and lead to de Sit- ter vacua. Our result avoids no-go theorems of perturbative stabilisation due to runaway potentials, in a way similar to the Coleman-Weinberg mechanism, and provides a counter example to one of the swampland conjectures concerning de Sitter vacua in quantum grav- ity, once string loop effects are taken into account; it thus paves the way for embedding the Standard Model of particle physics and cosmology in string theory.

Influence of cellulose particles on chemical resistance, mechanical and thermal properties of epoxy composites

Background: The technological developments for nanocellulose production from cheaper plant materials compared to wood, in particular, agricultural waste is an urgent task of nanobiophysics. The discovery of possibility of expanding the functional characteristics of materials in compositions with modified cellulose particles essentially stimulated the interest of researchers in cellulose composites. Surface modification of cellulose particles by functional materials, such as dyes, metal oxides, silicon, allows applying composites with modified cellulose in various areas of modern industry. A significant improvement in the operational performances of functionalized cellulose particles can be achieved by using them as filler in polymers. Epoxy resin compositions with modified and unmodified cellulose particles, studied in present work, are an example of hybrid biosystem. The interfacial interaction of filler particles with the epoxy matrix, their concentration and dispersion can change the physical and chemical properties of the biopolymer and the functional parameters of biocomposites. Studying the influence of external fields on the physical and chemical properties of epoxy resin-based biosystems and their influence on operational parameters seems to be an urgent problem of advanced and sustained materials science. Objectives: The purpose of this work was to develop an effective nanocellulose synthesis from plant materials and surface functionalization of micro- and nanocellulose particles with clathrochelate iron (ΙΙ) dye as well obtaining biocompositions of epoxy resin with functionalized and non-functionalized micro- and nanocellulose, and to explore of the morphology, chemical resistance, mechanical and thermal properties of epoxy composites with cellulose micro and nanoparticles. Materials and methods: The studying objects were the composites of epoxy resin Eposir-7120 with a polyethylene polyamine “PEPA” hardener in a ratio of 6.2:1 and 10% cellulose micro and nanoparticles. The microcellulose obtained from wood has been a commercial product. Nanocellulose has been synthesized from organosolv cellulose obtained from Miscanthus x giganteus stalks. Surface modification of micro- and nanocellulose was performed using the clathrochelate iron (ΙΙ) dye. The specific surface area of cellulose particles was determined using low-temperature nitrogen adsorption-desorption according to the Brunauer-Emmett-Teller method. Mechanical parameters were determined using universal Shopper and UMM-10 machines. Thermal analysis was performed using Q1500 analyzer. Swelling was determined by the gravimetric method. Results: Elastic modulus E, compressive strength σ and thermogravimetric parameters were determined. It was shown that in composites with micro and nanocellulose the E rises in 7.0–12.2% while the σ increases in 9.1% for composites with cellulose micro particles. The loading resin with nanocellulose and modified cellulose microparticles no affects the σ value of composites. The thermal stability of epoxy polymer (310°C) reduces after loading with micro and nanocellulose to 290 and 300°C, respectively. Chemical resistance of composites with both celluloses to 20% nitric acid reduces. In neutral medium swelling characterizes by rapid sorption to saturation of 15–20% acetone in 36 hours. Conclusions: Thus, the synthesis method of nanocellulose from plant materials and functionalization of its surface with clathrochelate iron (ΙΙ) were developed. Light response of dye was detected in visible spectral range. Epoxy resin composites with 10% micro and nanocellulose were obtained. The filling effect with micro- and nanocellulose at elastic modulus, compressive strength, and thermal stability of epoxycomposites was studied. The swelling processes run similarly in composites with cellulose micro and nanoparticles.

Stability and Resilient Modulus of Porous Asphalt Incorporating Steel Fiber

Porous Asphalt (PA) is known as a highly permeable asphalt surface that design to be permeable pavements for stormwater control and reduce the stormwater runoff. However, the structure is subjected to damage from cracking, rutting, stripping, and rapid aging under the effects of repeated vehicle loading, hot climates, and heavy rainfall. To overcome this, PA needs to modify using high tensile strength like steel fiber. Thus, this study aims to evaluate the performance of PA with the addition of steel fiber and overcome the issue that is related to PA. A mixture contains varying percentages of steel fiber were assessed to check which samples gives the best performance as per the requirement by using laboratory tests which are LA Abrasion, Resilient Modulus, Marshall Stability, and Density. The results show that the additions of 0.6% steel fiber give the lowest value of abrasion, while 0.5% fiber content contributes the highest value of Resilient Modulus and Marshall Stability respectively. PA mixtures modified with steel fiber produce the performance enhancement of PA as a road surfacing material. It is concluded that the asphalt mixtures containing steel fibers could increase the stability and strength of the mix.

A4 lepton flavor model and modulus stabilization from S4 modular symmetry

We study the modulus stabilization in an $A_4$ model whose $A_4$ flavor symmetry is originated from the $S_4$ modular symmetry. We can stabilize the modulus so that the $A_4$ invariant superpotential leads to the realistic lepton masses and mixing angles. We also discuss the phenomenological aspect of the present model as a consequence of the modulus stabilization.

Thermosets resins prepared from soybean oil and lignin derivatives with high biocontent, superior thermal properties, and biodegradability

ABSTRACTA bio‐based monomer, methacrylated vanillyl alcohol (MVA), had been synthesized from vanillyl alcohol with methacrylate anhydride (MAA) via a solvent‐free, efficient method. The synthesis of MVA was confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR). It was used to copolymerize with acrylated epoxidized soybean oil (AESO) to prepare a bio‐based resin (MVA–AESO). Excess MAA of MVA synthesis was further used to modify AESO with hydroxyl groups, generating (MVA–MAESO) with higher unsaturation degree. Their chemical structure and modification were characterized using13C NMR and Fourier transform infrared analyses. Pure AESO and MVA resins were used to compare with MVA–AESO and MVA–MAESO in terms of their viscosity, curing performance, mechanical, and thermal properties. The synthesized MVA–AESO and MVA–MAESO resins showed much lower viscosities than pure AESO due to the dilution of MVA. In addition, the incorporation of MVA reduced curing temperatures, activation energies which caused MVA–AESO and MVA–MAESO had higher curing degree than pure AESO. With the combination of MVA and modification of MAA, flexible AESO networks exhibited superior flexural properties, storage modulus, glass‐transition temperature, and thermal stability. Furthermore, the biodegradation of the formulated bio‐based resins were also investigated. Results showed that the addition of monomer and the increase in the content of CC bonds did not significantly affect the biodegradability of AESO, which may be due to the fact that the degradable groups of AESO were not affected. This environmentally friendly, low (volatile organic) resin, prepared by a high efficiency and environmental protection synthetic route, can potentially replace typical petroleum‐based thermosets for the production environmentally friendly thermosetting resins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 48827.

Performance of Charcoal Coconut Shell Ash in the Asphalt Mixture under Long Term Aging

Improvement in transportation system is never been as easy as just providing links for better connection and network but more to do with the pavement quality of the road itself. Modification with agriculture waste is just another approach to enhance the performance of asphaltic concrete. In this study, a non-traditional bitumen modifier from a coconut shell which is the charcoal coconut shell ash (CCSA) was used. Addition of CCSA in bitumen with 0%, 2%, 4%, 6%, and 8% by weight of bitumen were investigated along with the laboratory stimulation of aging was applied in this study. Properties of modified asphalt mixture were determined using resilient modulus, dynamic creep and Marshall Stability test.. Results of samples with CCSA which underwent aging show some improvement in terms of the stability and permanent deformation characteristics. Resilient modulus, dynamic creep and Marshall Stability tests recorded the highest rates when compared to controlled sample. Hence, for more durable asphalt concrete and high serviceability it is recommended to use 2% to 4% of CCSA.

The investigations of mechanical, thermal and rheological properties of polydimethylsiloxane/bismuth (III) oxide composite for X/Gamma ray shielding

Different types of materials are used for radiation shielding owing to the wide usage of radioactive materials in different applications and practices. However, the flexible nature of the shielding material provides a significant advantage in various applications. In this context, the usage of elastomeric materials in a radiation accident situation or normal operating conditions would be a great asset. Although lead is generally used as the gamma ray shielding material, bismuth is also preferred in gamma shielding due to its non-toxic structure and high atomic number. In this study, an X/gamma-ray shielding composite material that contains silicone rubber and bismuth (III) oxide was developed. Silicone rubber (polydimethylsiloxane) and bismuth (III) oxide compound were vulcanized and the curing behavior of the composite was investigated in detail, using both Moving Die Rheometer and Differential Scanning Calorimeter and analyzing the results concomitantly. Mechanical and thermal analyses were carried out and it was concluded from the analysis results that the addition of the bismuth (III) oxide into the silicone matrix was significantly improved the elastic modulus and thermal stability of the developed material. It was also concluded that bismuth (III) oxide addition into the silicone rubber matrix resulted in a flexible X/gamma shielding material with an attenuation rate of 96.4%. Moreover, half-value layer (HVL) decreased with the increment of bismuth (III) oxide content. We propose that the flexible silicone material with different bismuth content, which has both thermal and kinetic properties examined in detail, can be used as flexible X/gamma shielding material.

The Influence of Adopted Chemical Modification Route on the Thermal and Mechanical Properties of Alumina Nanoparticles-Impregnated Thermoplastic Natural Rubber Nanocomposite

In this study, the effect of different loadings of Lica-38-treated and untreated alumina (Al2O3) nanoparticles on the thermal conductivity and mechanical properties of thermoplastic natural rubber (TPNR) nanocomposite, which is prepared by melt blending method, was investigated. Scanning electron microscope showed good dispersion of nanofiller in the polymer matrix. Young’s modulus and impact strength for both treated and untreated nanocomposites enhanced with filler loading until 6 wt.%, beyond which deterioration was observed. In addition, the role of Lica-38 agent was vivid as the improvement in mechanical properties of the nanocomposite was attained when embedded with treated nanoparticles. The storage modulus and thermal stability have also improved following the same trend as mentioned earlier. The thermal conductivity of the nanocomposites increased with the addition of treated Al2O3 nanoparticles, which is ascribed to their connected percolated network that acted as efficient thermal pathways in the TPNR matrix. These results support the fact that the chemically modified nanocomposite has a potential application in electronic packaging.

Advances in Carbon Fiber Reinforced Polyamide-Based Composite Materials

Abstract Carbon fiber has been used to reinforce both aliphatic and aromatic polyamides. Aliphatic polyamide is known as nylon and aromatic polyamide is often referred to as aramid. Among aliphatic polyamides, polyamide 6, polyamide 6,6, polyamide 11, polyamide 12, and polyamide 1010 have been used as matrices for carbon fiber. Factors affecting the properties of polyamide/carbon fiber composites are: fiber amount, fiber length, fiber orientation, matrix viscosity, matrix-fiber interactions, matrix-fiber adhesion, and conditions encountered during manufacturing processes. This article presents a state-of-the-art review on polyamide/carbon fiber composites. Polyamide/carbon fiber composites are lightweight and exhibit high strength, modulus, fatigue resistance, wear resistance, corrosion resistance, gear, electrical conductivity, thermal conductivity, chemical inertness, and thermal stability. Incorporation of oxidized or modified carbon fiber and nanoparticle modified carbon fiber into polyamide matrices have been found to further enhance their physical properties. Applications of polyamide/carbon fiber composites in aerospace, automobile, construction, and other industries have been stated in this review. To fully exploit potential of polyamide/carbon fiber composites, concentrated future attempts are needed in this field.

About the mechanisms of fibre reinforced plastic behaviour under cycling loading

In order to study the peculiarities of the behavior of fiber reinforced plastics under cyclic loading, tests of specimens made of ELUR-P carbon tape and cold curing binder XT-118 with a stacking sequence 2 [+45°/−45°]2s (s - the number of laminas) for cyclic tension were carried out. It is established that stabilization of the secant modulus of elasticity is observed as the number of cycles increases. The experimental data were compared with the results of numerical modeling of the deformation processes under study. Based on numerical calculations and analytic solutions found, for a number of types of loads and creep kernels, the value of the secant modulus of elasticity does not depend on the load amplitudes, when using relations with the Abel creep kernel, the ratio of viscous parts of strain shifted by values, does not depend on the period of cyclic load, the amplitude of the load and the parameter that determines the degree of viscosity of the material, but depends only on the parameter that determines the degree of attenuation of the creeping process. By using the method of decomposing the load in a series of trigonometric functions with the same cyclic periods, it is shown that the effect is manifested in the general case of cyclic loading using relations with the Abel creep kernel. There is established the independence of secant and tangential moduli of elasticity from the absolute values of maximum and minimum stresses for any kinds of loads and creep kernels using the linear theory of hereditarily elastic body. A method has been developed for identifying creep kernel parameters, relations for viscoplastic and elastic strain based on the analysis of experimental data on cyclic loading. For the separation of hereditarily elastic and viscoplastic strain, the hypothesis was introduced that their rates at large times are very different. This made it possible, on the basis of theoretical results obtained for the Abel kernel, to obtain ratios from which, independently of other mechanical characteristics, one can find the attenuation parameter from the strain values, measured in the experiment in times shifted by an integer number of periods. The method is applied to processing the data of real experiments conducted by the authors.

Nanocomposite and Its Morphological Characterization -Review

In the wider field of nanotechnology, nanocomposites have attracted a great deal of attention and, due to the enhanced mechanical, electrical and thermal properties of the weld with modulus, strength and dimensional stability of the nanocomposite, they find increased use for various applications in several industries. Metallic and ceramic nanocomposites were used at an earlier stage of development to solve the dangerous issue of optimizing nanomaterial dispersal in matrices. Nanocomposites are currently finding uses in many fields. However, there are also some disadvantages to these characteristics such as optical issues dispersion difficulties, the color black display when different carbon containing nanocomposite are used viscosity increase and sediments. This finding review more about scope of nanocomposite and its morphological structural characterization that make it more suitable in its application.

Jumping spectra and vanishing couplings in heterotic Line Bundle Standard Models

We study two aspects of the physics of heterotic Line Bundle Standard Models on smooth Calabi-Yau threefolds. First, we investigate to what degree modern moduli stabilization scenarios can affect the standard model spectrum in such compactifications. Specifically, we look at the case where some of the complex structure moduli are fixed by a choice of hidden sector bundle. In this context, we study the frequency with which the system tends to be forced to a point in moduli space where the cohomology groups determining the spectrum in the standard model sector jump in dimension. Second, we investigate to what degree couplings, that are permitted by all of the obvious symmetries of the theory, actually vanish due to certain topological constraints associated to their higher dimensional origins. We find that both effects are prevalent within the data set of heterotic Line Bundle Standard Models studied.

Density and shrinkage as guiding criteria for the optimization of the thermal conductivity of poly(urethane)-class aerogels

We investigated the effect of gelation solvent, monomer type, and monomer concentration on the physical properties of freeze-dried poly(urethane)-poly(isocyanurate) (PUR-PIR) aerogels, with particular emphasis on their thermal conductivity. It was found that the gelation solvent considerably affects aerogel morphology and physical properties. Aerogels with the lowest thermal conductivity were obtained using a mixture of tetrahydrofuran (THF) and acetonitrile, in a 50% volume ratio. The influence on thermal conductivity of polyol and isocyanate structure and of their concentration was also investigated. Rigid precursors, phloroglucinol (POL), and an aromatic polyisocyanate based on toluene diisocyanate (Desmodur RC) yielded the lowest thermal conductivity. Our results were compared with recent work reporting on parameters that could be used as predictors of thermal conductivity and other physical properties of organic aerogels. None of these parameters were found to be satisfactory predictors of aerogel properties. For example, no systematic correlation between solvent solubility parameters and aerogel properties was observed. We also examined the role of the K-index. This index, defined as the ratio between porosity and contact angle, was shown recently to be a good predictor of the properties of polyurea aerogels. While the thermal conductivity scaled with the K-index, the scaling was different for each of the isocyanate monomers considered in our experiments. Thermal conductivity, instead, scaled well with the product of density and shrinkage of aerogels, independent of monomer type. The reasons of this dependence on shrinkage and density are discussed, and the use of these parameters to guide experimentation on other systems is discussed. Physical properties such as static and dynamic compression modulus and thermal stability of the most promising formulations were also examined.