Indoor mold levels and current asthma among school‐aged children in Saskatchewan,Canada

Current knowledge regarding the association between indoor mold exposures and asthma is still limited. The objective of this case–control study was to investigate the relationship between objectively measured indoor mold levels and current asthma among school‐aged children. Parents completed a questionnaire survey of health history and home environmental conditions. Asthma cases had a history of doctor‐diagnosed asthma or current wheeze without a cold in the past 12 months. Controls were age‐ and sex‐matched to cases. Vacuumed dust samples were collected from the child's indoor play area and mattress. Samples were assessed for mold levels and quantified in colony‐forming units (CFU). Sensitization to mold allergens was also determined by skin testing. Being a case was associated with family history of asthma, pet ownership, and mold allergy. Mold levels (CFU/m²) in the dust samples of children's mattress and play area floors were moderately correlated (r = 0.56; P < 0.05). High mold levels (≥30 000 CFU/m²) in dust samples from play [adjusted odds ratio (aOR) = 2.6; 95% CI: 1.03–6.43] and mattress (aOR) = 3.0; 95% CI: 1.11–8.00) areas were significantly associated with current asthma. In this study high levels of mold are a risk factor for asthma in children.     

Kinetics of degradation of PVC‐containing novel neem oil as stabilizer

The effectiveness of adding epoxidized neem oil (ENO) in poly(vinyl chloride) (PVC) to enhance heat stability was investigated. Neem oil, of vegetable extract, was characterized for its fatty acid profile and other properties. The virgin oil was epoxidized at 60°C with peroxymethanoic acid (performic acid) generated in situ in the reaction mixture by reacting hydrogen peroxide and methanoic acid. ENO was characterized by FTIR and NMR studies, and the degree of epoxidation was measured with iodine value and oxirane oxygen content. Solubility parameters of neem oil and ENO were estimated. Thermal degradation of PVC‐containing ENO was studied using the static heat stability test and artificial aging at temperatures of 100, 110, 120, and 130°C. Results were compared with the samples prepared with conventional heat stabilizers systems used in PVC, such as Ca/Zn stearates and mixtures of both Ca/Zn stearates and ENO. The changes in elastic modulus of the ENO/PVC combination and the conventionally stabilized Ca/Zn system during aging were kinetically modeled, and the rate constants for the degradative influence of modulus were determined. The activation energies and preexponential factors for the degradative process were obtained from Arrhenius plots and their relationship through a compensation effect was found. In general, ENO was found to be an effective retarder of the degradation of PVC; use of 10 phr level of ENO showed the least degradation with the highest activation energy. A synergistic effect of ENO and Ca/Zn stearate system was also observed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of microstructural arrangement of MDI-based polyurethanes on their photoproperties

Among the vast variety of polyurethane applications, several applications use the fluorescing nature of some of the polyurethanes. Even though 4,4′-methylenebis(phenylisocyanate) (MDI)-based polyurethanes fluoresce, their applications are rare because of the lack of knowledge about the fluorescence behavior of these polymers. In this study, the fluorophores responsible for the emission spectra of MDI-based polyurethanes were identified, and their emission behavior was investigated. When excited, these polymers produce two prominent emission peaks located at 356 nm and 423 nm, which are assigned to the radiative relaxation of excited isolated hard segments and excited crystalline hard segment bundles of the MDI-based polyurethanes, respectively. It was found that both chromophores can be excited by 293 nm UV radiation. The observed intensity variations of the two peaks with exposure time were attributed to the localized UV melting-assisted migration of isolated hard segments. This migration facilitates the formation of crystalline hard segments. As the two chromophore populations are inversely propositional to each other, the relative intensity of the two emission peaks varies with UV exposure in a similar manner. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47431.     

The effect of change of ionomer/polyol molar ratio on dispersion stability and crystalline structure of films produced from hydrophilic polyurethanes

In this study, we report the effect of the DMPA/PTHF molar ratio on dispersion properties of the MDI‐based hydrophilic polyurethane dispersions. In addition, the effect of the DMPA/PTHF molar ratio on the crystallinity and thermal properties of the polyurethane films prepared from dispersions are also discussed. The variation in stability was studied using a particle size analyzer. DSC and XRD analyses were used to study variations in crystallinity of films with the change of DMPA/PTHF molar ratio. FT‐IR spectra were used to monitor the formation of hydrogen bonds through urethane linkages to produce hard‐segment crystalline areas. The zeta potential increased with the increase of DMPA/PTHF molar ratio (hard‐segment content), while particle size of polyurethane particles decreased. Hence, the stability of dispersions was increased with DMPA/PTHF molar ratio due to the increase of hydrophilicity in polymer chain. Crystallinity of the films was increased with DMPA/PTHF molar ratio due to the increase of interchain interactions through Coulombic interactions and hydrogen bonding. Consequently, crystalline melting temperature was increased with the increase of DMPA/PTHF molar ratio. However, molten films formed crystalline soft segments instead of crystalline hard segments during slow cooling. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44475.     

Synthesis,characterization, and metal adsorption properties of tannin–phenol–formaldehyde resins produced using tannin from dried fruit of Terminalia chebula (Aralu)

In this study, tannin extracted from Terminalia chebula (Aralu) was used to produce tannin–phenol–formaldehyde resins. They were produced to obtain resins with different tannin to phenol ratio in an attempt to optimize the ion exchange capacities of resins produced. The resins made were sulfonated to improve their properties further. Bivalent cations, such as Zn²⁺, Pb²⁺, Ca²⁺, Mg²⁺, and Cu²⁺, were used to estimate the adsorption properties of both unsulfonated and sulfonated resins. The glass transitions of representative resins were estimated using differential scanning calorimeter thermograms. Fourier transform infrared spectroscopic analysis was used to gauge changes on resins by sulfonation and adsorption of cations. The glass transition values of unsulfonated, sulfonated, and metal‐adsorbed sulfonated resins showed a similar increasing trend with the increase of phenol content in the resin. The glass transition temperature values reach a plateau beyond the tannin/phenol ratio of 1 : 0.5, indicating the formation of large molar masses facilitating entanglements beyond that ratio. The phenol ratio of 1 : 0.5 has shown the highest adsorption capacity for all the metal ions used. The highest adsorption capacity was shown for sulfonated tannin–phenol–formaldehyde resin with the tannin/phenol ratio of 1 : 0.5 for Pb²⁺, which is 0.610 meq/g. The adsorption equilibrium data obtained using the column technique were found fitting Freundlich isotherm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of magnesium and phosphate ions on the stability of concentrated natural rubber latex and the properties of natural rubber latex–dipped products

The presence of Mg²⁺ ions was found to be a major cause of destabilization of natural rubber (NR) latex. On the other hand, the addition of excess PO ions to remove Mg²⁺ ions could adversely affect the physical properties of dipped products made of NR latex. A series of concentrated latex samples were treated with varying amounts of Mg²⁺ and PO ions. Changes with time in the characteristics of the treated latex samples such as mechanical stability time, volatile fatty acid number, and chemical stability time and in the physical properties of the dipped products such as aged and unaged tensile properties were monitored. The latex batch with a PO ion concentration of 30 ppm was found to produce the best‐quality latex and dipped products. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3120–3124, 2006