STUDIES ON THE RELATIONSHIP BETWEEN ORIENTATION MECHANISM AND MECHANICAL PROPERTIES OF ORIENTED POLYPROPYLENE. (8) INTERPRETATION OF ORIENTATION BEHAVIOR OF POLYPROPYLENE CRYSTALS DURING UNIAXIAL STRETCHING OF BULK POLYMER IN TERMS OF SPHERULITE DEFORMATION MECHANISM

This study was designed to explore the relationship between sunlight exposure and the mechanical properties of paragliding fabrics which have different colors, densities, yarn counts, and coating materials. This study exposed 5 different colors of paragliding fabrics (red, turquoise, dark blue, orange, and white) to intense sunlight for 150 hours during the summer from 9:00 a.m. to 3:00 p.m. for 5 days a week for 5 weeks. Before and after the UV radiation aging process, the air permeability, tensile strength, tear strength, and bursting strength tests were performed. Test results were also evaluated using statistical methods. According to the results, the fading of the turquoise fabric was found to be the highest among the studied fabrics. It was determined that there is a significant decrease in the mechanical properties of the fabrics after sunlight exposure. After aging, the fabrics become considerably weaker in the case of mechanical properties due to the degradation in both the dyestuff and macromolecular structure of the fiber

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Water lubrication of graphene oxide-based materials

Friction ◽

10.1007/s40544-021-0539-8 ◽

2021 ◽

Author(s):

Shaoqing Xue ◽

Hanglin Li ◽

Yumei Guo ◽

Baohua Zhang ◽

Jiusheng Li ◽

...

Keyword(s):

Mechanical Properties ◽

Graphene Oxide ◽

Lubrication Theory ◽

Lubricant Additives ◽

Water Lubrication ◽

Broad Application ◽

Water Dispersibility ◽

Metal Processing ◽

The Relationship ◽

Ph Concentration

AbstractWater is as an economic, eco-friendly, and efficient lubricant that has gained widespread attention for manufacturing. Using graphene oxide (GO)-based materials can improve the lubricant efficacy of water lubrication due to their outstanding mechanical properties, water dispersibility, and broad application scenarios. In this review, we offer a brief introduction about the background of water lubrication and GO. Subsequently, the synthesis, structure, and lubrication theory of GO are analyzed. Particular attention is focused on the relationship between pH, concentration, and lubrication efficacy when discussing the tribology behaviors of pristine GO. By compounding or reacting GO with various modifiers, amounts of GO-composites are synthesized and applied as lubricant additives or into frictional pairs for different usage scenarios. These various strategies of GO-composite generate interesting effects on the tribology behaviors. Several application cases of GO-based materials are described in water lubrication, including metal processing and bio-lubrication. The advantages and drawbacks of GO-composites are then discussed. The development of GO-based materials for water lubrication is described including some challenges.

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Structure and properties of a phenylethynyl-terminated PMDA-type asymmetric polyimide

High Performance Polymers ◽

10.1177/0954008318762592 ◽

2018 ◽

Vol 31 (3) ◽

pp. 261-272 ◽

Cited By ~ 7

Author(s):

Yixiang Zhang ◽

Masahiko Miyauchi ◽

Steven Nutt

Keyword(s):

Mechanical Properties ◽

Thermal Processing ◽

Amorphous Structure ◽

Decomposition Temperature ◽

Thermal And Mechanical Properties ◽

Chain Mobility ◽

Amorphous Structures ◽

The Cross ◽

Imide Oligomers ◽

The Relationship

A new polymerized monomeric reactant (PMR)-type polyimide, designated TriA X, was investigated to determine polymer structure, processability, thermal, and mechanical properties and establish the relationship between the molecular structure and those properties. TriA X is a PMR-type polyimide with an asymmetric, irregular, and nonplanar backbone. Both the imide oligomers and the cross-linked polyimides of TriA X exhibited loose-packed amorphous structures, independent of thermal processing. The peculiar structures were attributed to the asymmetric backbone, which effectively prevented the formation of closed-packed chain stacking typically observed in polyimides. The imide oligomers exhibited a lower melt viscosity than a control imide oligomer (symmetric and semi-crystalline), indicating a higher chain mobility above the glass transition temperature ( Tg). The cured polyimide exhibited a Tg = 362°C and a decomposition temperature = 550°C. The cross-linked TriA X exhibited exceptional toughness and ductility (e.g. 15.1% at 23°C) for a polyimide, which was attributed to the high-molecular-weight oligomer and loose-packed amorphous structure. The thermal and mechanical properties of TriA X surpass those of PMR-15 and AFR-PE-4.

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