Addition Of Same Amount Research Articles

Inorganic salts as effective additive for adjusting the curing of natural oriental lacquer

Oriental lacquer, a milk-white sap collected from lacquer trees, can be cured automatically to bright and dense films in the presence of air, thus is worthy of being regarded as a type of natural green coating, as it does not emit any volatile organic compounds. It has been used in Asia for more than 8000 years attributing to its excellent characteristics. However, during harvesting and storage process, the lacquer sap surface can automatically polymerize into lacquer blocks under the catalysis of laccase present in the sap, wasting a significant amount of resources. It is an arduous task how to slow down the curing of oriental lacquer in storage without affecting the normal curing process in operation. Herein, the curing of oriental lacquer was adjusted using Na2CO3 and NaCl as additives. The results indicated that the addition of Na2CO3 quenched the semiquinone radical during the polymerization of urushiol, the main component of oriental lacquer, without affecting the laccase activity. Under the appropriate condition (25 °C and 80% relative humidity), the touch-free dryness time of the oriental lacquer mixed with Na2CO3 increased from 3 h to 15 days. Moreover, the addition of same amount of Na2CO3 and NaCl to oriental lacquer improved the curing time to 6 h, which was similar to that of pristine lacquer without the addition of any salts. The polymerization rate of the lacquer sap returned to the normal again, that may be due to the blocking of the reaction between urushiol and CO32‐ after the introduction of NaCl. Thereby, this study provided a novel and green method for oriental lacquer to achieve storage for a long time and relatively normal curing during application. This provides a guarantee for the wide use of oriental lacquer as a green natural coating.

Chemical and physical reinforcement of hydrophilic gelatin film with di-aldehyde nanocellulose

Gelatin is a representative hydrophilic protein material with remarkable biocompatibility and biodegradability. From the aspect of materials processing, gelatin also has the advantage that its entire fabrication process can be performed in an aqueous solution. However, practical application of various gelatin materials—in particular gelatin films—has thus far been limited because of their weak mechanical properties and vulnerability under aqueous environments. To overcome these disadvantages, both physical reinforcement approaches and chemical cross-linking agents have been tested. However, little research has been done to make these two roles work at the same time. In this study, cellulose nanocrystals containing aldehyde groups were prepared via a periodate oxidation process and used for cross-linkable reinforcement of gelatin-based bio-composite films. The results revealed that the di-aldehyde cellulose nanocrystal (D-CNC) could react and covalently cross-link with the amine group of the gelatin molecules via Schiff base formation and compared with neat CNC. The gelatin bio-composite film reinforced with the prepared D-CNC exhibited excellent tensile properties and water resistance, and its mechanical and hydrophilic properties could be easily controlled by adjusting the D-CNC content and was greater than addition of same amount in CNC. Therefore, D-CNC will facilitate the widespread use of existing water-soluble polymers, especially natural hydrophilic proteins and can be used in conventional application fields such as the food, pharmaceutical, and biomedical industries.

The Impact of Selectively Plasticized Poly (ethylene oxide) (PEO) Block in Nanostructured Polystyrene−PEO−Polystyrene Triblock Copolymer Electrolytes

All polymer electrolytes, including block polymer (BP) electrolytes exhibit low ionic conductivity compared to liquid electrolytes. For homopolymer electrolytes, the ionic conductivity can be increased by incorporating plasticizer into the polymer network. However, the subsequent weakened mechanical structure of the network precludes its use in many practical applications. In this work, we selectively plasticize the PEO block in a polystyrene PS-PEO-PS triblock copolymer electrolyte using a PEO-like plasticizer: tetraethylene glycol dimethyl ether (TEGDME). Unlike its homopolymer (PEO) electrolyte counterpart, the mechanical properties of the PS-PEO-PS triblock copolymer electrolyte are not drastically degraded by this plasticizer because it is immiscible in the nonpolar PS block domains. Polymer electrolyte membranes were cast from lithium trifluoromethanesulfonate (LiTFS) solutions with the corresponding polymers. The molar ratio of ethylene oxide to Li+ is 16 for all electrolytes (nEO:nLi = 16:1). The ionic conductivity of the PS-PEO-PS electrolyte at 80 °C is about one order of magnitude lower than that of the homopolymer (PEO) counterpart at the same temperature. However, the shear modulus (G’) of the PS-PEO-PS electrolyte is about three orders of magnitude higher than the homopolymer, indicating the mechanical properties of the copolymer electrolyte is primarily dominated by the PS phase. The addition of TEGDME plasticizer to the PEO homopolymer electrolyte resulted in a ~10% increase in conductivity. The addition of same amount of TEGDME to the PS-PEO-PS electrolyte resulted in ~100% increase in conductivity. Compared to the dry electrolyte counterpart, the low isothermal frequency (ω = 0.1 rad/s) elastic modulus, G’ of the TEGDME plastized PS-PEO-PS was reduced to half at 80 °C (on the order of 106 Pa). Surprisingly, G’ of the plastized membrane surpassed its dry PS-PEO-PS counterpart at higher frequency values (17 < ω < 100 rad/s). This counter intuitive result is further explored using: 1) Fourier-transform infrared spectroscopy (FTIR) to elucidate the salt solvation and coordination to ether oxygens, and 2) small angle X-ray scattering (SAXS) to decipher the domain spacing of the adjacent copolymer blocks. Acknowledgment This work is supported by Dr. Imre Gyuk, Manager, Energy Storage Program, Office of Electricity Delivery and Reliability, Department of Energy. CC acknowldge partial financial support by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Thermomechanical behaviour of zirconia–multiwalled carbon nanotube-reinforced polypropylene hybrid composites

The present investigation reveals the effect of addition of zirconia-coated multiwalled carbon nanotubes (MWCNTs) on mechanical and thermal properties of polypropylene (PP) matrix composites. Initially, zirconia coating on MWCNTs (ZrO2–CNT) has been performed with the help of isothermal hydroxylation technique and confirmed through typical microstructural and morphological characterizations. Thereafter, the effect of zirconia of mechanical and thermal properties of PP matrix composites has been studied through comparing the thermal decomposition behaviour, tensile and thermomechanical properties of pure PP, MWCNT-reinforced PP composite and ZrO2–CNT-reinforced PP hybrid composite. In short, the addition of 5 wt% CNTs improved tensile modulus by 22%, tensile strength by 16% and storage modulus by 45%, while the addition of same amount of ZrO2–CNT improved the above sequenced properties by 44, 47 and 73%, respectively. Moreover, ZrO2–CNT/PP hybrid composite has been found to have better thermally stability than pure PP as well as CNT/PP composite.

Exploring the roles of molecular structure on the β-crystallization of polypropylene random copolymer

To investigate effects of molecular structures on β-crystallization of polypropylene random copolymer (PPR), PPR-A and PPR-B with similar molecular weight and distribution but significantly different polymorphic behavior were used. Wide-angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FT-IR), solvent fractionation combined with successive self-nucleation and annealing (SSA) and Gel Permeation Chromatography (GPC) were applied. Results revealed that after addition of same amount of β-nucleating agent (β-NA), large amount of β-phase is obtained in PPR-A (K β = 0.603), while no β-phase can be seen from PPR-B; Structure characterizations revealed that they have similar molecular weight but different total amount and distribution of ethylene comonomer: the total content of ethylene comonomer of PPR-A is higher compared with PPR-B, but its ethylene comonomer distribution is less uniform. In this way, PPR-A possesses high molecular weight high isotactic fraction, which cannot be seen from PPR-B due to its more uniform comonomer distribution. Therefore, the presence of highly isotactic PP (HPP) is the key factor in β-crystallization of PPR. For verification, HPP with low or high molecular weights are respectively added into β-nucleated PPR-B. Results revealed that HPP was effective in enhancing β-crystallization of PPR-B; higher molecular weight of HPP was more favorable and more effective.

Low-temperature sintering and electrical properties of Co-doped ZnO varistors

ZnO–Bi2O3–B2O3-based varistors doped with each kind of cobalt oxides were prepared by conventional ceramic processing. The effects of CoO, Co2O3 and Co3O4 on the microstructure and the electrical characteristics of varistor samples sintered at 880 °C were investigated separately. Analysis of microstructure indicated the cobalt cations were distributed both in grain regions and grain boundary regions and no crystalline phases containing cobalt were detected in XRD patterns for the samples with various cobalt oxides. All these cobalt oxides could effectively enhance the varistor performance by effectively increasing the nonlinear coefficient and lowing the leakage current, while the breakdown voltage fields increased slightly. Capacitance–voltage characteristics showed the potential barriers of varistor samples increased with the addition of each cobalt oxide. It was found that the addition of same amount of cobalt cations in various cobalt oxides had a different effect on the varistor samples. Best electrical properties were obtained for the varistor sample containing Co3O4, in which the nonlinearity coefficient is 28.5, the leakage current density is 3.4 μA and the breakdown voltage field is as low as 260 V/mm.

The mechanism of clouding in triton X-100: The effect of additives

The mechanism of clouding in the nonionic surfactant is investigated through the effect of additives. The cloud point of Triton X-100 is shown to be very sensitive to the additions of small amounts (10 −5 M) of charged surface active agents while the cloud point remains unaltered on addition of same amount of the salt NaCl and n-butanol (10 −5 M). This is considered to be a clear indication of the result of charging the micellar surface. The linear rise in the clouding temperature of a Triton X-100 with the addition of additives sodium lauryl sulfate, sodium decyl sulfate, and sodium dodecyl benzene sulfonate up to a maximum concentration of 1 molecule per micelle of Triton X-100, is interpreted in terms of the rise in surface charge of the micelle. It is concluded that these observations support the view of regarding the cloud point as a critical phenomenon rather than the growth of micelles.