Atmospheric emission of nanoplastics from sewer pipe repairs.

Nanoplastic particles are inadequately characterized environmental pollutants that have adverse effects on aquatic and atmospheric systems, causing detrimental effects to human health through inhalation, ingestion and skin penetration1-3. At present, it is explicitly assumed that environmental nanoplastics (EnvNPs) are weathering fragments of microplastic or larger plastic debris that have been discharged into terrestrial and aquatic environments, while atmospheric EnvNPs are attributed solely to aerosolization by wind and other mechanical forces. However, the sources and emissions of unintended EnvNPs are poorly understood and are therefore largely unaccounted for in various risk assessments4. Here we show that large quantities of EnvNPs may be directly emitted into the atmosphere as steam-laden waste components discharged from a technology commonly used to repair sewer pipes in urban areas. A comprehensive chemical analysis of the discharged waste condensate has revealed the abundant presence of insoluble colloids, which after drying form solid organic particles with a composition and viscosity consistent with EnvNPs. We suggest that airborne emissions of EnvNPs from these globally used sewer repair practices may be prevalent in highly populated urban areas5, and may have important implications for air quality and toxicological levels that need to be mitigated.

Spontaneous Emulsions: Adjusting Spontaneity and Phase Behavior by Hydrophilic-Lipophilic Difference-Guided Surfactant, Salt, and Oil Selection.

Spontaneous emulsion behavior has been difficult to predict and could be influenced by many variables including salinity, temperature, and chemical composition of the oil and surfactant. In this work, the hydrophilic-lipophilic difference (HLD) framework was used to predict the formation of spontaneous emulsions using a mixture of Span-80 and SLES surfactants. The spontaneity and emulsion behavior of different systems were modeled by estimating the HLDmix. The influence of surfactant ratio, salinity, and oil type was investigated. Spontaneous emulsification could only be observed when the HLDmix was between -0.96 and 1.04. Within this range, a negative HLDmix resulted in a greater spontaneity to form o/w emulsion, and a w/o emulsion was more likely to form when the HLDmix was positive. When the HLDmix was close to 0 (between -0.22 and 0.56 in our systems), emulsions were formed in both the oil and aqueous phases with high spontaneity. A combined effect of ultralow interfacial tension, Span-80 micelle swelling, and interfacial turbulence due to Marangoni effects is likely the main mechanism of the spontaneous emulsification observed in this study. A synergistic reduction in interfacial tension was observed between Span-80 and SLES (<1 mN/m). When the HLD of the system was close to 0, a bicontinuous emulsion phase was formed at the oil-water interface. The bicontinuous emulsion broke-up over time due to the ultralow interfacial tension and interfacial turbulence, forming dispersed oil and water droplets. Results from this work provide a practical method to suggest what surfactant composition, salinity, and oil type could promote (or eliminate) the conditions favorable for spontaneous emulsification.

Predicting Spontaneous Emulsification in Saltwater Environments Using the HLD Model.

Spontaneous emulsification of toluene with nonylphenol polyethoxylate (NPE) and sodium dodecylbenzenesulfonate (SDBS) surfactants in saltwater environments was studied. NaCl promoted the spontaneous emulsification of an otherwise non-spontaneous SDBS-toluene system. Dynamic light scattering and turbidity indicated that spontaneity increased with NaCl concentration. The mechanism of spontaneous emulsification was dependent on surfactant type; NPE emulsified via micelle swelling, and SDBS emulsified via nucleation and growth. Hydrophilic lipophilic difference (HLD) calculations were used to model spontaneous emulsification and spontaneity. As HLD approached zero, conditions became more favorable for spontaneous emulsification. Between HLD values of -2.4 and -2.05, samples transitioned from non-spontaneous to spontaneous. This study aids in predicting spontaneous emulsion formation in saltwater environments for applications in nanoemulsion formation and wastewater remediation.

Structure-Property Relationship of Cellulose Nanocrystal-Polyvinyl Alcohol Thin Films for High Barrier Coating Applications.

CO2 and O2 gas permeability are paramount concerns in food packaging. Here, the permeability of cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVA) coatings was explored as it relates to varied CNC content. Specifically, this work focuses on the role of PVA in rheology and barrier performance of the CNC films. Results show that shear-casted CNC films are transparent and have a high-order parameter, which is attributed to the shear-thinning behavior of the CNCs. The barrier performance of the CNC films improved because of the synergistic effect of having both alignment of CNCs and a lower free volume. The CNC-PVA films exhibited excellent barrier performance as compared to traditional engineered polymers, even much higher than high barrier ethylene-vinyl alcohol copolymer films. Furthermore, the moisture sensitivity of the films was greatly diminished with the addition of PVA. Overall, the results show applicability of CNC-PVA coating formulations for high barrier packaging applications.

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Role of Bromide.

Aromatic polyamide-based membranes are widely used for reverse osmosis (RO) and nanofiltration (NF) treatment but degrade when exposed to free chlorine (HOCl/OCl-). The reaction mechanisms with free chlorine were previously explored, but less is known about the role of bromide (Br-) in these processes. Br- may impact these reactions by reacting with HOCl to form HOBr, which then triggers other brominating agents (Br2O, Br2, BrOCl, and BrCl) to form. This study examined the reactivities of these brominating agents with a polyamide monomer model compound, benzanilide (BA), and a modified version of it, N-CH3-BA. The results indicated that all these brominating agents only attacked the aromatic ring adjacent to the amide N, rather than the amide N, different from the previously examined chlorinating agents (HOCl, OCl-, and Cl2) that attacked both sites. Orton rearrangement was not observed. Species-specific rate constants (ki, M-1 s-1) between BA and HOBr, Br2O, Br2, BrOCl, and BrCl were determined to be (5.3 ± 1.2) × 10-2, (1.2 ± 0.4) × 101, (3.7 ± 0.2) × 102, (2.2 ± 0.6) × 104, and (6.6 ± 0.9) × 104 M-1 s-1, respectively, such that kBrCl > kBrOCl > kBr2 > kBr2O > kHOBr. N-CH3-BA exhibited lower reactivity than BA. Model predictions of BA loss during chlorination with varied Br- and/or Cl- concentrations were established. These findings will ultimately enable membrane degradation and performance loss following chlorination in mixed halide solutions to be better predicted during pilot- and full-scale NF and RO treatment.

An emerging mobile air pollution source: outdoor plastic liner manufacturing sites discharge VOCs into urban and rural areas.

The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an emerging mobile source of anthropogenic air pollution. Evidence indicates volatile organic compounds (VOCs) can be released before, during, and after manufacture. The chemical composition of a popular uncured styrene-based CIPP resin was examined, along with the VOCs that remained in the new cured composite. The roles of curing temperature and heating time in waste discharged into the air were examined. Uncured resin contained approximately 39 wt% VOCs. Multiple hazardous air pollutants were present, however, 61 wt% of the uncured resin was not chemically identified. A substantial mass of VOCs (8.87 wt%) was emitted into the air during manufacture, and all cured composites contained about 3 wt% VOCs. Some VOCs were created during manufacture. Curing temperature (65.5-93.3 °C) and heating time (25-100 min) did not cause different composite VOC loadings. High styrene air concentrations inhibited the detection of other VOCs in air. It is estimated that tens of tons of VOCs may be emitted at a single CIPP manufacturing site. Regulators should consider monitoring, and potentially regulating, these growing mobile air pollution and volatile chemical product sources as they are operating in urban and rural areas often in close proximity to residential and commercial buildings.

Diffusion-Controlled Spontaneous Emulsification of Water-Soluble Oils via Micelle Swelling.

Spontaneous emulsification of toluene, xylenes, cyclohexane, and mineral oil in a nonionic nonylphenol polyethoxylate surfactant solution was investigated by visual observations coupled with dynamic light scatting measurements and interfacial tensiometry. For water-soluble oils, nanoscale emulsions formed spontaneously by diffusion of oil molecules into the aqueous surfactant solutions and subsequent swelling of surfactant micelles with oil. Micelle swelling rates were quantified to assess system spontaneity, revealing that oil solubility in water was directly correlated to the spontaneity of the emulsion (toluene > xylenes > cyclohexane). When experiments were intentionally designed to create surfactant concentration gradients, Marangoni flows were found to enhance spontaneity. Despite their spontaneous formation, emulsion stability was limited over the course of 40 days by Ostwald ripening followed by creaming and evaporation. These results provide insights on the likelihood of nanoemulsion formation and persistence in oily wastewater as the components in this study are present in many wastewater systems.

Influence of Free Volume Determined by Positron Annihilation Lifetime Spectroscopy (PALS) on Gas Permeability of Cellulose Nanocrystal Films.

Cellulose nanocrystals (CNCs) are of increasing interest for packaging applications because of their biodegradability, low cost, high crystallinity, and high aspect ratio. The objective of this study was to use positron annihilation lifetime spectroscopy (PALS) to investigate the free volume of CNC films with different structural arrangements (chiral nematic vs shear-oriented CNC films) and relate this information to gas barrier performance. It was found that sheared CNC films with higher CNC alignment have lower free volume and hence have more tortuosity than chiral nematic self-assembled films, which lowers gas diffusion throughout the films. The overall barrier performance of the aligned CNC film obtained in this study has a higher barrier performance than high barrier polymer films like PVOH and EVOH. Furthermore, a modified model was developed for single-component CNC films to predict the gas permeability with variation of CNC alignment with validation by the data taken.

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Reaction Kinetics, Mechanisms, and the Role of Chloride.

Aromatic polyamide thin-film composite membranes are widely used in reverse osmosis (RO) and nanofiltration (NF) due to their high water permeability and selectivity. However, these membranes undergo biofouling and can degrade and eventually fail during free chlorine exposure. To better understand this effect, the reactivity of the polyamide monomer (benzanilide (BA)) with free chlorine was tested under varying pH and chloride (Cl-) conditions. The kinetic results indicated that the current existing mechanisms, especially the Orton rearrangement, were invalid. Revised reaction pathways were proposed where BA chlorination was driven by two independent pathways involving the anilide ring and amide nitrogen moieties. The ability for one moiety to be chosen over the other was highly dependent on the pH, Cl- concentration, and the resulting chlorinating agents (e.g., Cl2, HOCl, OCl-, and Cl2O) generated. Species-specific rate constants for BA with Cl2, OCl-, and HOCl equaled (7.6 ± 0.19) × 101, (1.7 ± 1.5) × 101, (2.1 ± 0.71) × 10-2 M-1 s-1, respectively. A similar value for Cl2O could not be accurately estimated under the tested conditions. The behavior of these chlorinating agents differed for each reactive site such that OCl- > HOCl for N-chlorination and Cl2 > HOCl > OCl- for anilide ring chlorination. Experiments with modified monomers indicated that substituent placement largely affected which reactive site was kinetically favorable. Overall, such findings provide a predictive model of how the polyamide monomer degrades during chlorine exposure and guidance on how chlorine-resistant polyamide membranes should be designed.

In vitro toxicity assessment of emitted materials collected during the manufacture of water pipe plastic linings.

Objectives: US water infrastructure is in need of widespread repair due to age-related deterioration. Currently, the cured-in-place (CIPP) procedure is the most common method for water pipe repair. This method involves the on-site manufacture of a new polymer composite plastic liner within the damaged pipe. The CIPP process can release materials resulting in occupational and public health concerns. To understand hazards associated with CIPP-related emission exposures, an in vitro toxicity assessment was performed. Materials and Methods: Mouse alveolar epithelial and alveolar macrophage cell lines and condensates collected at 3 worksites utilizing styrene-based resins were utilized for evaluations. All condensate samples were normalized based on the major emission component, styrene. Further, a styrene-only exposure group was used as a control to determine mixture related toxicity. Results: Cytotoxicity differences were observed between worksite samples, with the CIPP worksite 4 sample inducing the most cell death. A proteomic evaluation was performed, which demonstrated styrene-, worksite-, and cell-specific alterations. This examination of protein expression changes determined potential biomarkers of exposure including transglutaminase 2, advillin, collagen type 1, perilipin-2, and others. Pathway analysis of exposure-induced proteomic alterations identified MYC and p53 to be regulators of cellular responses. Protein changes were also related to pathways involved in cell damage, immune response, and cancer. Conclusions: Together these findings demonstrate potential risks associated with the CIPP procedure as well as variations between worksites regarding emissions and toxicity. Our evaluation identified biological pathways that require a future evaluation and also demonstrates that exposure assessment of CIPP worksites should examine multiple chemical components beyond styrene, as many cellular responses were styrene-independent.

Considerations for emission monitoring and liner analysis of thermally manufactured sewer cured-in-place-pipes (CIPP).

Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged sewer pipes. They are gaining popularity in North America, Africa, Asia, Europe, and Oceania. Volatile and semi-volatile organic compound (VOC/SVOC) emissions from storm sewer CIPP installations were investigated at a dedicated outdoor research site. Tedlar bag, sorbent tube, and photoionization detector (PID) air sampling was conducted for five steam-CIPP installations and was coupled with composite characterizations. New CIPPs contained up to 2.21 wt% volatile material and only 6-31% chemical mass extracted per CIPP was identified. Each 6.1 m [20 ft] liner contained an estimated 5-10 kg [11-22 lbs] of residual chemical. Extracted chemicals included hazardous air pollutants and suspected and known carcinogens that were not reported by others. These included monomers, monomer oxidation products, antioxidants, initiator degradation products, and a plasticizer. PID signals did not accurately represent styrene air concentration differing sometimes by 10s- to 1000s-fold. Multiple VOCs found in air samples likely affected PID responses. Styrene (>86.4 ppmv) and methylene chloride (>1.56 ppmv) air concentrations were likely greater onsite and phenol was also detected. Additional studies are needed to examine pollutant emissions so process monitoring can be improved, and environment impacts and associated human exposures can be minimized.

Assessment of early onset surface damage from accelerated disinfection protocol.

Background: The objective of this study was to evaluate the extent and potential mechanisms of early onset surface damage from simulated wiping typical of six-months of routine disinfection and to assess the subsequent microbial risk of surfaces damaged by disinfectants. Methods: Eight common material surfaces were exposed to three disinfectants and a neutral cleaner (neutral cleaner, quaternary ammonium, hydrogen peroxide, sodium hypochlorite) in accelerated aging tests to simulate a long-term disinfection routine. Materials were also immersed in dilute and concentrated chemical solutions to induce surface damage. Surfaces were chemically and physically characterized to determine extent of surface damage. Bactericidal efficacy testing was performed on the Quat-based disinfectant using a modified version of EPA standard operating procedure MB-25-02. Results: The wiping protocol increased surface roughness for some material surfaces due to mechanical abrasion of the wiping cloth. The increased roughness did not correlate with changes in bactericidal efficacy. Chemical damage was observed for some surface-disinfectant combinations. The greatest observed effects from disinfectant exposure was in changes in wettability or water contact angle. Conclusions: Early onset surface damage was observed in chemical and physical characterization methods. These high-throughput material measurement methods were effective at assessing nanoscale disinfectant-surface compatibility which may go undetected though routine macroscale testing.

Outdoor manufacture of UV-Cured plastic linings for storm water culvert repair: Chemical emissions and residual.

Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-in-place-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia, USA. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31 mg/L), dibutyl phthalate (12.5 µg/L), and phenol (16.7 µg/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48 h aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0 to > 9.0 wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described.

Cellulose Nanocrystal (CNC) Coatings with Controlled Anisotropy as High-Performance Gas Barrier Films.

Cellulose nanomaterials are promising materials for the polymer industry due to their abundance and renewability. In packaging applications, these materials may impart enhanced gas barrier performance due to their high crystallinity and polarity. In this work, low barrier to superior gas barrier pristine nanocellulose films were produced using a shear-coating technique to obtain a range of anisotropic films. Induction of anisotropy in a nanocellulose film can control the overall free volume of the system which effectively controls the gas diffusion path; hence, controlled anisotropy results in tunable barrier properties of the nanocellulose films. The highest anisotropy materials showed a maximum of 900-fold oxygen barrier improvement compared to the isotropic arrangement of nanocellulose film. The Bharadwaj model of nanocomposite permeability was modified for pure nanoparticles, and the CNC data were fitted with good agreement. Overall, the oxygen barrier performance of anisotropic nanocellulose films was 97 and 27 times better than traditional barrier materials such as biaxially oriented poly(ethylene terephthalate) (BoPET) and ethylene vinyl alcohol copolymer (EVOH), respectively, and thus could be utilized for oxygen-sensitive packaging applications.

Investigation of the factors that influence lead accumulation onto polyethylene: Implication for potable water plumbing pipes.

The influence of polymer aging, water pH, and aqueous Pb concentration on Pb deposition onto low density polyethylene (LDPE) was investigated. LDPE pellets were aged by ozonation at 85 °C. ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis of aged LDPE surfaces showed that a variety of polar functional groups (>CO<, >CO, >COO) were formed during aging. These functional groups likely provided better nucleation sites for Pb(OH)2 deposition compared to new LDPE, which did not have these oxygen-containing functional groups. The type and amount of Pb species present on these surfaces were evaluated through XPS. The influence of exposure duration on Pb deposition onto LDPE was modeled using the pseudo-first-order equation. Distribution ratios of 251.5 for aged LDPE and 69.3 for new LDPE showed that Pb precipitates had greater affinity for the surface of aged LDPE compared to new LDPE. Aged LDPE had less Pb surface loading at pH 11 compared to loading at pH 7.8. Pb surface loading for aged LDPE changed linearly with aging duration (from 0.5-7.5 h). Pb surface loading on both new and aged LDPE increased linearly with increasing Pb initial concentration. Greater Pb precipitation rates were found for aged LDPE compared to new LDPE at both tested pH values.

The interaction of surfactants with plastic and copper plumbing materials during decontamination.

The study goal was to examine the effectiveness of surfactants to decontaminate plastic and copper potable water plumbing components. Several common potable water pipe and gasket plastics were examined as well as Alconox® detergent, Dawn® soap, and MAGIT-DG 100 surfactants. Results showed that the MAGIT-DG 100 solutions permeated all plastics within 3days, effectively compromising tensile strength (-82%), physical dimension (+43% volume, +45% weight), and oxidative resistance (-15%). A variety of MAGIT-DG 100 solution compounds permeated plastic samples, not just the declared major ingredient. PVC and cPVC pipes sorbed the least amount of this solution's components of all the plastic pipes tested. Alconox® and Dawn® solutions caused minimal changes to the physical and mechanical properties of all plastics examined. Crosslinked polyethylene type A (PEX-a) pipe was more susceptible to crude oil contamination than copper pipe. Flushing with a pure water Alconox® solution mixture removed all benzene, toluene, ethylbenzene, and total xylenes (BTEX) from copper pipe. No decontamination method affected BTEX removal from PEX pipe. Under certain conditions surfactant solutions have the potential to alter material integrity and may not be a viable option in removing hydrophobic organic compounds from plastic pipe.

Hydrothermal Synthesis and Processing of Barium Titanate Nanoparticles Embedded in Polymer Films.

Barium titanate nanoparticles embedded in flexible polymer films were synthesized using hydrothermal processing methods. The resulting films were characterized with respect to material composition, size distribution of nanoparticles, and spatial location of particles within the polymer film. Synthesis conditions were varied based on the mechanical properties of the polymer films, ratio of polymer to barium titanate precursors, and length of aging time between initial formulations of the solution to final processing of nanoparticles. Block copolymers of poly(styrene-co-maleic anhydride) (SMAh) were used to spatially separate titanium precursors based on specific chemical interactions with the maleic anhydride moiety. However, the glassy nature of this copolymer restricted mobility of the titanium precursors during hydrothermal processing. The addition of rubbery butadiene moieties, through mixing of the SMAh with poly(styrene-butadiene-styrene) (SBS) copolymer, increased the nanoparticle dispersion as a result of greater diffusivity of the titanium precursor via higher mobility of the polymer matrix. Additionally, an aminosilane was used as a means to retard cross-linking in polymer-metalorganic solutions, as the titanium precursor molecules were shown to react and form networks prior to hydrothermal processing. By adding small amounts of competing aminosilane, excessive cross-linking was prevented without significantly impacting the quality and composition of the final barium titanate nanoparticles. X-ray diffraction and X-ray photoelectron spectroscopy were used to verify nanoparticle compositions. Particle sizes within the polymer films were measured to be 108 ± 5 nm, 100 ± 6 nm, and 60 ± 5 nm under different synthetic conditions using electron microscopy. Flexibility of the films was assessed through measurement of the glass transition temperature using dynamic mechanical analysis. Dielectric permittivity was measured using an impedance analyzer.

Enhanced Wettability and Transport Control of Ultrafiltration and Reverse Osmosis Membranes with Grafted Polyelectrolytes.

End-functionalized poly(acrylic acid) (PAA-silane) was synthesized with reversible addition-fragmentation chain-transfer (RAFT) polymerization and attached to both polysulfone ultrafiltration (UF) and polyamide reverse osmosis (RO) membranes through a nonimpairing, one-step grafting to approach in order to improve membrane surface wettability with minimal impact on membrane transport performance. After PAA grafting, composition and morphology changes on the membrane surface were characterized with Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Static contact angle on PAA grafted membranes exhibited an increase in surface hydrophilicity and hence a potential enhancement in antifouling performance. The native contact angle on the polysulfone membrane systems was 86° and was reduced to 24° after modification, while the polyamide film contact angle decreased from 58° to 25°. The PAA layer endowed the porous UF membrane with dynamic control over the permeability and selectivity through the manipulation of the solution pH. The UF membrane with a 35 nm average pore size displayed a 115% increase in flux when the contact solution was changed from pH 11 to pH 3. This effect was diminished to 70% and 32% as the average pore size decreased to 20 and 10 nm, respectively. Modified RO membranes displayed no reduction in membrane performance indicating that the underlying materials were unaffected by the modification environment or added polymer. Model polyamide and polysulfone surfaces were reacted with the PAA-silane inside a quartz crystal microbalance (QCM) to help inform the deposition behavior for the respective membrane chemistries.

QCM-based measurement of chlorine-induced polymer degradation kinetics.

Highly structured network polymers are prepared via a molecular layer by layer technique (mLbL) and used as a model system to study aqueous degradation of polymer thin films in real time. Quantitative analysis of the degradation kinetics was enabled by the use of a quartz crystal microbalance (QCM). We conclude that the common metric of halogen, specifically chlorine, exposure (concentration × time) to be an ineffective normalization unit and showed a multistage adsorption process consistent with the established chemical mechanism. Additionally, degradation progression was tracked at multiple points of exposure to determine the effects of chlorination on the chemical and morphological state of the polymer structure with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The formation of known halogenation products were corroborated with XPS through the high resolution spectra. Insight into the heterogeneous nature of the nanostructural degradation was derived from the AFM images. Periodic rinsing was found to release adsorbed chlorine but had negligible benefits on extending the exposure limits of the polyamide film. Fluorinated amine monomer (3,4-difluoroaniline) was incorporated into the surface of the polymer to determine the effect of limiting N-halogenation and the formation of the halogenated ring product. The modified surface layer reduced the rate and magnitude of chlorine adsorption relative to the neat polyamide surface. The QCM technique was shown to be an effective tool for rapid and high fidelity evaluation of molecular degradation and modification strategies to increase device lifetimes.

Rational interface design of epoxy-organoclay nanocomposites: role of structure-property relationship for silane modifiers.

Montmorillonite was modified by three silane surfactants with different functionalities to investigate the role of surfactant structure on the properties of a final epoxy-organoclay nanocomposite. N-aminopropyldimethylethoxysilane (APDMES), an aminated monofunctional silane, was chosen as a promising surfactant for several reasons: (1) it will bond to silica in montmorillonite, (2) it will bond to epoxide groups, and (3) to overcome difficulties found with trifunctional aminosilane bonding clay layers together and preventing exfoliation. A trifunctional and non-aminated version of APDMES, 3-aminopropyltriethoxysilane (APTES) and n-propyldimethylmethoxysilane (PDMMS), respectively, was also studied to provide comparison to this rationally chosen surfactant. APDMES and APTES were grafted onto montmorillonite in the same amount, while PDMMS was barely grafted (<1 wt%). The gallery spacing of APDMES organoclay was greater than APTES or PDMMS, but the final nanocomposite gallery spacing was not dependent on the surfactant used. Different concentrations of APDMES modified montmorillonite yielded different properties, as concentration decreased glass transition temperature increased, thermal stability increased, and the storage modulus decreased. Storage modulus, glass transition temperature, and thermal stability were more similar for epoxy-organoclay composites modified with the same concentration of silane surfactant, neat epoxy, and epoxy-montmorillonite nanocomposite.