Deep eutectic solvent for curing of phthalonitrile resin: Lower the curing temperature but improve the properties of thermosetting

2020 ◽  
pp. 095400832097215
Author(s):  
Yu Qi ◽  
Zhihuan Weng ◽  
Ce Song ◽  
Yue Hu ◽  
Xin Liu ◽  
...  
Keyword(s):  
High Performance ◽  
Oxidation Stability ◽  
Deep Eutectic Solvent ◽  
Curing Temperature ◽  
Molar Ratio ◽  
Curing Agent ◽  
Curing Process ◽  
Curing Time ◽  
Functional Pathway

Long curing duration and high curing temperature are commonly known to restrict the application of the phthalonitrile resin. In this study, a deep eutectic solvent (DES) containing ZnCl2 and urea has been developed to improve the curing process of the resorcinol-based phthalonitrile resin (DPPh) without sacrificing the useful properties of the resin. For the molar ratio of ZnCl2 and urea as 1:1 (ZnCl2-urea (1–1)), the initial curing temperature and apparent activation energy of the system were recorded as 179.5°C and 90.1 kJ/mol, respectively, indicating a reduction of 31.2% and 39.0% as compared to the pristine ZnCl2 system. More importantly, with curing time of 6 h and post-curing temperature of 300°C, the temperature at 5% weight loss as well as glass transition temperature of the resin with DES as the curing agent were 523.1°C and 370.2°C, respectively, demonstrating a significant improvement as compared to the resin cured with ZnCl2. In addition, the satisfactory long-term oxidation stability of the resin could also be obtained by employing the new curing agent. The findings from this study open a functional pathway for facile preparation of the high-performance curing agent for the phthalonitrile resin.

Water-Resistant Modification of Desulphurization Gypsum Block

2012 ◽  
Vol 182-183 ◽  
pp. 278-282
Author(s):  
Yan Mu ◽  
Ying Li Fu ◽  
Feng Qing Zhao
Keyword(s):  
Fly Ash ◽  
Mechanical Strength ◽  
High Performance ◽  
Water Resistance ◽  
Curing Temperature ◽  
Curing Time ◽  
Operating Property ◽  
High Mechanical Strength ◽  
Calcined Gypsum ◽  
Hemi Hydrate

A high performance water resistance agent KD-3 prepared from OPC cement, fly ash, slag and additives was used for the modification of hemi-hydrate desulphurization gypsum. Various factors on gypsum block were investigated. The prepared gypsum block possesses excellent water-resistance, good operating property and high mechanical strength. The optimized results was obtained: calcined gypsum 74.9%, KD-3 25%, retarder 0.1%, curing temperature 60°C and curing time 16h.

Permeability of Expansive Soils Modified/Stabilized with lime (Review Paper)

2021 ◽  
Vol 14 (2) ◽  
pp. 129-140
Author(s):  
Muwafaq Awad ◽  
Ibrahim Al-Kiki ◽  
Amina Khalil
Keyword(s):  
Expansive Soils ◽  
Expansive Soil ◽  
Pozzolanic Reaction ◽  
Curing Temperature ◽  
Curing Time ◽  
Short Term ◽  
Coefficient Of Permeability ◽  
Review Study ◽  
Time Periods

The aim of this paper was to review the mechanism of the expansive soil-lime reactions: short term and long-term reactions in both lime modification and lime stabilization. The focus of the study was the effect of curing time for a certain centigrade 25C curing temperature in both lime modification / stabilization-expansive soils on the coefficient of permeability. Peer reviewed articles published between 2000- and 2019 were collected and relevant data were extracted. Results of this review study showed that the coefficient of permeability of expansive soils modified with lime increased during the first 7 days of curing time at curing temperature 25C and it remains constant or slightly decreased for longer curing time periods. However, for expansive soils stabilized with lime, it was found that the coefficient of permeability increased during the first 7-day curing time at curing temperature 25C, then decreased during the longer curing time periods (pozzolanic reaction). It is also noted that even though the coefficient of permeability decreased during pozzolanic reaction, it remains higher than that of the untreated soils

Optimization of the Uncooked Oratosquilla Oratoria Curing Process via Response Surface Methodology

2014 ◽  
Vol 1073-1076 ◽  
pp. 1793-1797
Author(s):  
Qi Wei Mao ◽  
Jun Rui Wu ◽  
Xi Qing Yue
Keyword(s):  
Pathogenic Bacteria ◽  
Raw Materials ◽  
Curing Temperature ◽  
Curing Process ◽  
Curing Time ◽  
Optimal Process ◽  
Curing Conditions ◽  
Oratosquilla Oratoria ◽  
Sensory Score ◽  
Total Bacteria

Oratosquilla oratoria was the experimental raw materials in the paper. Design expert8.0.6 and Excel2007 was used to analyze the optimal process with the factors which were curing time, curing temperature, curing salt contention and the index which was the total bacteria. The pathogenic bacteria and sensory score under various curing conditions were determined simultaneously. After analyzing the significance of the various factors and interactions, the results showed the optimum curing conditions of oratosquilla oratoria were as follows: curing time 7.14h, curing temperature 14.34°C, curing salt contention 8.3%. Under this condition no pathogenic bacteria was detected and the sensory score was the highest.

A Review on the Effect of Fly Ash, RHA and Slag on the Synthesizing of Coal Bottom Ash (CBA) Based Geopolymer

2021 ◽  
Vol 11 (1) ◽  
pp. 20
Author(s):  
Nor Farhana Binti Ab Gulam ◽  
A. B. M. Amrul Kaish ◽  
Abir Mahmood ◽  
Sudharshan N. Raman ◽  
Maslina Jamil ◽  
...  
Keyword(s):  
Fly Ash ◽  
Erosion Resistance ◽  
Rice Husk Ash ◽  
Lightweight Concrete ◽  
Bottom Ash ◽  
Curing Temperature ◽  
Curing Time ◽  
Construction Sector ◽  
Coal Bottom Ash

Geopolymerization is widely used in the construction sector for its characteristics of strong compressive strengths, quick hardening, long-term durability, fire resistance, and erosion resistance. This paper has gone through the geopolymer performances utilizing coal bottom ash (CBA), CBA blended with fly ash (FA), CBA mixed together with slag, and CBA with rice husk ash (RHA). CBA shows a better performance than FA in the compressive strength. This paper has discovered several elements that influence geopolymerization, the curing time, the curing temperature, the silicate and hydroxide ratio, and grinding CBA surfaces. The combination of CBA and RHA is suitable for lightweight concrete, as the range of the volumetric weight is within 1192 kg/m3 to 1655 kg/m3. The slump result decreases, as the ratio of CBA and slag increases. Slag particles are uneven in shape, which increases water consumption and leads to a honeycombed structure, whereas CBA particles are spherical in shape, which enhances workability.

scholarly journals Effect of Curing Conditions on the Shrinkage of Ultra High-Performance Fiber-Reinforced Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Song Han ◽  
Yefu Cui ◽  
Hanfeng Huang ◽  
Mingzhe An ◽  
Ziruo Yu
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
Bound Water ◽  
Fiber Reinforced Concrete ◽  
Curing Temperature ◽  
Early Age ◽  
Fiber Reinforced ◽  
Curing Conditions ◽  
High Performance Fiber

The effect of curing conditions on the early age and long-term shrinkage of ultra high-performance fiber-reinforced concrete (UHPFRC) was systematically studied. The shrinkage of the early age (0–168 h) and long-term age (0–90 d) of UHPFRC material was measured based on three kinds of humidity conditions (dry, sealed, and soaked) and curing temperatures (25°C, 40°C, and 75°C), respectively. In this paper, the hydration degree of different shrinkage stages was studied in combination with chemical-bound water experiment. Meanwhile, the influencing mechanism of curing condition on the shrinkage of UHPFRC was analyzed. The results show that the early shrinkage rate of UHPFRC is accelerated with the increase of temperature, and the rate of shrinkage development at the latter stage is suppressed with the increase of temperature. With the increase of humidity, the early age shrinkage of UHPFRC and its increasing rate gradually decrease, which means drying condition > sealing condition > soaking condition. According to the long-term shrinkage results, increasing temperature has very significant inhibiting effect on the UHPFRC shrinkage in the sealed condition. Due to the majority of the in-site components of UHPFRC cured in the sealed condition, high-temperature curing has evident inhibition of early age shrinkage of UHPFRC. Therefore, promoting curing temperature is fairly effective at inhibiting the early age shrinkage of UHPFRC for the in-site structures.

Study on Curing Behavior of Low Molar Ratio Urea-Formaldehyde Resins with Different Curing Agents

2010 ◽  
Vol 150-151 ◽  
pp. 965-968
Author(s):  
Yao Hui Dong ◽  
Qiang Gao ◽  
Yue Zhang ◽  
Jian Zhang Li
Keyword(s):  
Thermal Analysis ◽  
Bonding Strength ◽  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Molar Ratio ◽  
Curing Agent ◽  
Curing Time ◽  
Curing Behavior ◽  
Uf Resin ◽  
Curing Agents

In order to characterize the curing behavior of low molar ratio urea-formaldehyde (UF) resin, the curing time and thermal analysis in curing reaction of the UF resins and the bonding strength and formaldehyde emission of plywood bonded by five kinds of low molar ratio UF resins with six different curing agents were studied. The results indicated that the UF resins with the molar ratio of formaldehyde to urea more than 1.0 could get reasonable curing time. The heat enthalpy of UF resins significantly increased with the enhancing the acidity of curing agent. The plywood manufactured by the UF resins with 1.1 molar ratio showed much higher bonding strength and lower formaldehyde emission.

The study of Thermal Resistant Enhancement of Siloxane-Modified LED Transparent Encapsulants

2007 ◽  
Vol 1007 ◽  
Author(s):  
Kai-Chi Chen ◽  
Chia-Wen Hsu ◽  
Hsun-Tien Li
Keyword(s):  
Thermal Resistance ◽  
High Performance ◽  
Diglycidyl Ether ◽  
Thermal Treatments ◽  
Curing Agent ◽  
C Storage ◽  
Yellow Index ◽  
Modified Epoxy ◽  
Mean Time

ABSTRACTThermal resistant property of siloxane-modified epoxy compositions designed for long-term and high temperature storage was investigated. In this study, we developed two siloxane-modified epoxy compositions to improve the thermal stability of current epoxy encapsulants. One composition contained silicone epoxy, and the other one was cyclic aliphatic siloxane dianhydride.We selected triglycidyl ether terminated Phenylmethylsiloxnae-co-dimethylsiloxne (GT-1000), which was compatible with the diglycidyl ether of bisphenol A epoxy (Epon-828), to partial replaced the epoxy resin and was cured by liquid anhydride (MHHPA). In the mean time, we also synthesized 5, 5'-(1, 1, 3, 3-tetramethyl disiloxane-1, 3-dilyl)-bis-norborane-2, 3-dicarboxylic anhydride (A1) as a co-curing agent to cure Epon-828.The thermal resistance was studied by measuring the increase of yellow index (ΔYI) after thermal treatments. In 110 °C storage experiment for 1000 h, the ΔYI of GT-1000 0.2 equivalent was 1.51, whereas Epon-828/MHHPA (Comp 1) was 6.74. Moreover, The ΔYI of the composition with higher equivalent GT-1000 was only 2.15 after 2000 hours thermal aging. In the cyclic aliphatic siloxane dianhydride co-curing compositions, when A1 was 0.05 and 0.1 equivalent, the ΔYI was 2.28 and 0.72 after 1000 h, respectively. Compared with Comp 1, both GT-1000 and A1 were effective for thermal resistance.In IR-reflow test, the ΔYI of GT-1000/Epon-828/MHHPA= 0.5/0.5/1 was 0.65 and that of Epon-828/MHHPA was 1.49 after 260 °C for 10 seconds. The results revealed that either the siloxane-modified epoxy or siloxane-modified curing agent had excellent thermal resistant property for high performance LED applications.

scholarly journals Stability of Salvia fruticosa Mill. polyphenols and antioxidant activity in a citrate-based natural deep eutectic solvent

2020 ◽  
Vol 19 (2) ◽  
pp. 200-207 ◽  
Author(s):  
Spyros Grigorakis ◽  
Abedalghani Halahlah ◽  
Dmitris Makris
Keyword(s):  
Sodium Citrate ◽  
Deep Eutectic Solvent ◽  
Reducing Power ◽  
Molar Ratio ◽  
Long Term Conditions ◽  
High Performing ◽  
Salvia Fruticosa ◽  
The Stability ◽  
Natural Deep Eutectic Solvent

In a previous study, it was demonstrated that a novel deep eutectic solvent (DES), composed of lactic acid and sodium citrate dibasic at a molar ratio of 15:1 (LA-SCDB15), was a high-performing system with regard to polyphenol extraction from the medicinal plant Salvia fruticosa Mill. (Greek or Cretan sage). However, an issue of particular importance that should be addressed is the stability of the extract in this novel liquid since the information available to-date on extract stability in DES is rather limited and inconclusive. In this frame, this study was undertaken to generate extracts of S. fruticosa with LA-SCDB15 (a 77/23 w/w mixture of DES with water) and examine their stability in this solvent. S. fruticosa extracts exhibited remarkable stability under both accelerated and long-term conditions, and the antiradical activity and the ferric-reducing power of the extracts were shown to suffer virtually trivial modifications. Further analytical examination with liquid chromatography-diode array-tandem mass spectrometry assured that the major polyphenolic phytochemicals occurring in Salvia fruticosa extracts underwent non-significant changes and remained practically intact. It was concluded that the neoteric DES LA-SCDB15 may provide outstanding stability in polyphenol-containing extracts and its testing on other plant extracts is proposed as a further step towards revealing its stabilizing potential.

scholarly journals Green Valorization of Olive Leaves to Produce Polyphenol-Enriched Extracts Using an Environmentally Benign Deep Eutectic Solvent

2020 ◽  
Vol 2 (2) ◽  
pp. 226-239 ◽  
Author(s):  
Olga Kaltsa ◽  
Spyros Grigorakis ◽  
Achillia Lakka ◽  
Eleni Bozinou ◽  
Stavros Lalas ◽  
...  
Keyword(s):  
High Performance ◽  
Deep Eutectic Solvent ◽  
Deep Eutectic Solvents ◽  
Process Variable ◽  
Molar Ratio ◽  
Olive Leaves ◽  
Total Polyphenol ◽  
Solid Ratio ◽  
Wide Range ◽  
Efficient Recovery

Olive leaves (OLL) are considered to be a highly appreciated bioresource of bioactive polyphenolic phytochemicals, embracing several different structures. However, extraction processes based on deep eutectic solvents (DES) are very limited despite the wide range of techniques developed for the efficient recovery of polyphenols. This study had as objective the development of a simple, green, high-performance extraction methodology for OLL polyphenols, using a recently reported effective DES, composed of L-lactic acid and glycine. Initially, a screening was performed to select the most appropriate L-lactic/glycine molar ratio and process optimization was then carried out with response surface methodology. The optimized process variable values were DES/water (78% w/v), liquid-to-solid ratio of 36 mL g−1, and stirring speed of 500 rounds per minute, and the total polyphenol yield amounted to 97.53 ± 3.54 mg gallic acid equivalents per g dry matter. Extraction with DES at 80 °C did not significantly increase the total polyphenol yield, but it did enhance the total flavonoid yield and antioxidant activity. High-performance liquid chromatography analyses revealed that extraction with the DES resulted in extended oleuropein hydrolysis, to the favor of hydroxytyrosol formation. This finding might have a prospect in using properly tuned DES for polyphenol modification with improved bioactivities.

Effect of Curing Temperature and Cross-Linker to Pre-Polymer Ratio on the Viscoelastic Properties of a PDMS Elastomer

2015 ◽  
Vol 1112 ◽  
pp. 410-413 ◽  
Author(s):  
Firdaus Prabowo ◽  
Adrian Law Wing-Keung ◽  
Hayley H. Shen
Keyword(s):  
Curing Temperature ◽  
Curing Agent ◽  
Curing Time ◽  
Small Amplitude Oscillatory Shear ◽  
Pdms Elastomer ◽  
Linear Viscoelastic ◽  
Cross Linker ◽  
G Value ◽  
The Stability ◽  
Polymer Ratio

Viscoelastic samples made from a PDMS elastomer, Sylgard 184 (Dow Corning, USA), were prepared using 9.1% and 3% curing agent (cross-linker) and heat-cured with four curing temperatures from 25° to 150°C and four curing durations from 48 h to 25 min. Small amplitude oscillatory shear (SAOS) rheometry was done to examine their mechanical properties, represented by the storage (G’) and loss (G”) moduli. Generally, G’ and G” are dependent on the frequency, curing agent percentage and curing temperature. The samples were then reheated and SAOS tested again to check the stability of G’ and G”. It was apparent that the stability of G’ and G” are both strongly dependent on the curing temperature. Samples with the curing temperature of 25°C yielded almost up to 4 times change of G” value for 9.1% curing agent and more than 2 times change of G’ value for 3% curing agent. Hence, the usage of 25°C curing temperature at the manufacturer recommended curing time is not suitable for applications where the linear viscoelastic stability is important. In general, the stability also improves as the frequency increases for all samples.

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