Polyhydroxylated C60 as an Hypercross-Linking Agent

1994 ◽  
Vol 359 ◽  
Author(s):  
Long Y. Chiang ◽  
Lee Y. Wang ◽  
Rong-Shen Wu ◽  
Kuo-Huang Hsieh
Keyword(s):  
Mechanical Properties ◽  
Ambient Temperature ◽  
Fullerene Derivatives ◽  
Polyurethane Networks ◽  
Thermal Mechanical Properties ◽  
Naoh Solution ◽  
Polyhydroxylated Fullerenes ◽  
Hydrolysis Of ◽  
Tetramethylene Oxide

ABSTRACTPolyhydroxylated fullerene derivatives (fullerenols) were utilized as an efficient hypercross-linking agent for the synthesis of elastic poly(tetramethylene oxide)-based polyurethane networks with excellent thermal mechanical properties. Polyhydroxylated fullerenes were synthesized from the hydrolysis of polycyclosulfated fullerene derivatives in the presence of water at 85-90 °C or in aqueous NaOH solution at ambient temperature.

Novel Oxidative Nucleophilic Chemistry Enroute to The Synthesis of C60 Fullerols

1993 ◽  
Vol 328 ◽  
Author(s):  
Long Y. Chiang ◽  
Lee Y. Wang ◽  
John W. Swirczewski
Keyword(s):  
Sulfuric Acid ◽  
Ambient Temperature ◽  
Oxidation Reaction ◽  
Chemical Structure ◽  
High Yield ◽  
Radical Intermediates ◽  
Naoh Solution ◽  
Polyhydroxylated Fullerenes ◽  
Hydrolysis Of ◽  
Sulfate Species

ABSTRACTWe have demonstrated a novel cyclosulfation chemistry for the functionalization of C60 Molecules and a new route to the synthesis of fullerol. The cyclosulfation reaction of C60 was performed in neat fuming sulfuric acid at 55–60 °C under N2. Hydrolysis of these derivatives in the presence of water at 85–90 °C or in aqueous NaOH solution at ambient temperature gave the corresponding polyhydroxylated fullerenes (fullerols) in high yield. Various spectroscopie methods were used to resolve the chemical structure of fullerol. An average of 10 to 12 hydroxyl addends was found in fullerols that can be correlated to the structure of polycyclosulfated fullerene precursors containing 5 to 6 cyclosulfate units. The cyclosulfation chemistry is, presumably, initiated by an one-electron oxidation reaction on C60 Molecules, followed by the attack of nucleophilic anionie sulfate species onto the resulting cationic C60 radical intermediates. Further electron oxidation and intramolecular cyclization of the resulting hydrogen sulfated C60 yielded the desired polycyclosulfated C60 products.

scholarly journals Mechanical Properties of Mortars Reinforced with Amazon Rainforest Natural Fibers

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 155
Author(s):  
Régis Pamponet da Fonseca ◽  
Janaíde Cavalcante Rocha ◽  
Malik Cheriaf
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Natural Fibers ◽  
Construction Materials ◽  
Hot Water ◽  
Amazon Rainforest ◽  
Hot Water Treatment ◽  
Composite Binder ◽  
Naoh Solution ◽  
Reference Samples

The addition of natural fibers used as reinforcement has great appeal in the construction materials industry since natural fibers are cheaper, biodegradable, and easily available. In this work, we analyzed the feasibility of using the fibers of piassava, tucum palm, razor grass, and jute from the Amazon rainforest as reinforcement in mortars, exploiting the mechanical properties of compressive and flexural strength of samples with 1.5%, 3.0%, and 4.5% mass addition of the composite binder (50% Portland cement + 40% metakaolin + 10% fly ash). The mortars were reinforced with untreated (natural) and treated (hot water treatment, hornification, 8% NaOH solution, and hybridization) fibers, submitted to two types of curing (submerged in water, and inflated with CO2 in a pressurized autoclave) for 28 days. Mortars without fibers were used as a reference. For the durability study, the samples were submitted to 20 drying/wetting cycles. The fibers improved the flexural strength of the mortars and prevented the abrupt rupture of the samples, in contrast to the fragile behavior of the reference samples. The autoclave cure increased the compressive strength of the piassava and tucum palm samples with 4.5% of fibers.

scholarly journals The Effect of Different Types of Internal Curing Liquid on the Properties of Alkali-Activated Slag (AAS) Mortar

2021 ◽  
Vol 13 (4) ◽  
pp. 2407
Author(s):  
Guang-Zhu Zhang ◽  
Xiao-Yong Wang ◽  
Tae-Wan Kim ◽  
Jong-Yeon Lim ◽  
Yi Han
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Deionized Water ◽  
Internal Curing ◽  
Control Group ◽  
Alkali Activated Slag ◽  
Different Types ◽  
Naoh Solution ◽  
Activated Slag ◽  
Alkali Activated

This study shows the effect of different types of internal curing liquid on the properties of alkali-activated slag (AAS) mortar. NaOH solution and deionized water were used as the liquid internal curing agents and zeolite sand was the internal curing agent that replaced the standard sand at 15% and 30%, respectively. Experiments on the mechanical properties, hydration kinetics, autogenous shrinkage (AS), internal temperature, internal relative humidity, surface electrical resistivity, ultrasonic pulse velocity (UPV), and setting time were performed. The conclusions are as follows: (1) the setting times of AAS mortars with internal curing by water were longer than those of internal curing by NaOH solution. (2) NaOH solution more effectively reduces the AS of AAS mortars than water when used as an internal curing liquid. (3) The cumulative heat of the AAS mortar when using water for internal curing is substantially reduced compared to the control group. (4) For the AAS mortars with NaOH solution as an internal curing liquid, compared with the control specimen, the compressive strength results are increased. However, a decrease in compressive strength values occurs when water is used as an internal curing liquid in the AAS mortar. (5) The UPV decreases as the content of zeolite sand that replaces the standard sand increases. (6) When internal curing is carried out with water as the internal curing liquid, the surface resistivity values of the AAS mortar are higher than when the alkali solution is used as the internal curing liquid. To sum up, both NaOH and deionized water are effective as internal curing liquids, but the NaOH solution shows a better performance in terms of reducing shrinkage and improving mechanical properties than deionized water.

scholarly journals Recyclable Self-Healing Polyurethane Cross-Linked by Alkyl Diselenide with Enhanced Mechanical Properties

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 773 ◽  
Author(s):  
Yuqing Qian ◽  
Xiaowei An ◽  
Xiaofei Huang ◽  
Xiangqiang Pan ◽  
Jian Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Amide Bond ◽  
Self Healing ◽  
Healing Efficiency ◽  
Polyurethane Networks ◽  
Combined Action ◽  
Cross Linker ◽  
Dynamic Structures ◽  
External Interventions

Dynamic structures containing polymers can behave as thermosets at room temperature while maintaining good mechanical properties, showing good reprocessability, repairability, and recyclability. In this work, alkyl diselenide is effectively used as a dynamic cross-linker for the design of self-healing poly(urea–urethane) elastomers, which show quantitative healing efficiency at room temperature, without the need for any catalysts or external interventions. Due to the combined action of the urea bond and amide bond, the material has better mechanical properties. We also compared the self-healing effect of alkyl diselenide-based polyurethanes and alkyl disulfide-based polyurethanes. The alkyl diselenide has been incorporated into polyurethane networks using a para-substituted amine diphenyl alkyl diselenide. The resulting materials not only exhibit faster self-healing properties than the corresponding disulfide-based materials, but also show the ability to be processed at temperatures as low as 60 °C.

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