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Article

Peng Du, Haibao Hu, Feng Ren and Dong Song

The maintenance of the air–water interface is crucial for the drag reduction on hydrophobic surfaces. But the air bubbles become unstable and even washed away under high…

Abstract

Purpose

The maintenance of the air–water interface is crucial for the drag reduction on hydrophobic surfaces. But the air bubbles become unstable and even washed away under high speed flow, causing the failure of surface hydrophobicity. Thereby, this paper aims to understand the relations between bubble behaviors and surface properties, flow conditions and to discover new methods to maintain the air–water interface.

Design/methodology/approach

Bubble properties on hydrophobic surfaces were characterized using single-component multiphase lattice Boltzmann simulation. Three equations of state (EOSs), including the Peng–Robinson, Carnahan–Starling and modified Kaplun–Meshalkin EOSs, were incorporated to achieve high density ratios.

Findings

Both the static and dynamic properties of bubbles on hydrophobic surfaces were investigated and analyzed under different flow conditions, solid–liquid interactions and surface topology.

Originality/value

By revealing the properties of bubbles on hydrophobic surfaces, the effects of flow conditions and surface properties were characterized. The maintenance method of air–water interface can be proposed according to the bubble properties in the study.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Yongtao Yao, Yuncheng Xu, Bing Wang, Weilong Yin and Haibao Lu

The purpose of this paper is to provide a review of recent systematic and comprehensive advancement in electrospun polymer fiber and their composites with shape memory property.

Abstract

Purpose

The purpose of this paper is to provide a review of recent systematic and comprehensive advancement in electrospun polymer fiber and their composites with shape memory property.

Design/methodology/approach

The nanofiber manufacture technique is initially reviewed. Then, the influence of electrospinning parameters and actuation method has been discussed. Finally, the study concludes with a brief review of recent development in potential applications.

Findings

Shape memory polymer (SMP) nanofibers are a type of smart materials which can change shape under external stimuli (e.g. temperature, electricity, magnetism, solvent). In general, such SMP nanofibers could be easily fabricated by mature electrospinning technique. The nanofiber morphology is mainly affected by the electrospinning parameters, including applied voltage, tip-to-collector distance, viscosity of solution, humidity and molecular weight. For actuation method, most SMP nanofibers and their composites can change their shapes in response to heat, magnetic field or solvent, while few can be driven by electricity. Compared with the block SMPs, electrospun SMP nanofibers’ mat with porosity and low mechanical property have a wide potential application field including tissue engineering, drug delivery, filtration, catalysis.

Originality/value

This paper provides a detailed review of shape memory nanofibers: fabrication, actuation and potential application, in the near future.

Details

Pigment & Resin Technology, vol. 47 no. 1
Type: Research Article
ISSN: 0369-9420

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Article

Zhenghong Li, Haibao Lu, Yongtao Yao and Long Lin

The purpose of this paper is to develop an effective approach to significantly improve the thermomechanical properties of shape memory polymer (SMP) nanocomposites that…

Abstract

Purpose

The purpose of this paper is to develop an effective approach to significantly improve the thermomechanical properties of shape memory polymer (SMP) nanocomposites that show fast thermally responsive shape recovery.

Design/methodology/approach

Hexagonal boron nitrides (h-BNs) were incorporated into polymer matrix in an attempt to improve the thermal conductivity and thermally responsive shape recovery behaviour of SMP, respectively. Thermally actuated shape recovery behaviour was recorded and monitored instrumentally.

Findings

The results show that both glass transition temperature (Tg) and thermomechanical properties of the SMP nanocomposites have been progressively improved with increasing concentration of h-BNs. Analytical results also suggest that the fast-responsive recovery behaviour of the SMP nanocomposite incorporated with h-BNs was due to the increased thermal conductivity.

Research limitations/implications

A simple way for fabricating SMP nanocomposites with enhanced thermally responsive shape recovery based on the incorporation of h-BNs was developed.

Originality/value

The outcome of this study may help fabrication of SMP nanocomposites with fast responsive recovery behaviour.

Details

Pigment & Resin Technology, vol. 46 no. 1
Type: Research Article
ISSN: 0369-9420

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Article

Haibao Lu, Yongtao Yao, Jinying  Yin and Long Lin

This paper aims to study the synergistic effect of self-assembled carboxylic acid-functionalised carbon nanotube (CNT) and nafion/silica nanofibre nanopaper on the…

Abstract

Purpose

This paper aims to study the synergistic effect of self-assembled carboxylic acid-functionalised carbon nanotube (CNT) and nafion/silica nanofibre nanopaper on the electro-activated shape memory effect (SME) and shape recovery behaviour of shape memory polymer (SMP) nanocomposite.

Design/methodology/approach

Carboxylic acid-functionalised CNT and nafion/silica nanofibre are first self-assembled onto carbon fibre by means of deposition and electrospinning approaches, respectively, to form functionally graded nanopaper. The combination of carbon fibre and CNT is introduced to enable the actuation of the SME in SMP by means of Joule heating at a low electric voltage of 3.0-5.0 V.

Findings

Nafion/silica nanofibre is used to improve the shape recovery behaviour and performance of the SMP for enhanced heat transfer and electrical actuation effectiveness. Low electrical voltage actuation and high electrical actuation effectiveness of 32.5 per cent in SMP has been achieved.

Research limitations/implications

A simple way for fabricating electro-activated SMP nanocomposites has been developed by using functionally graded CNT and nafion/silica nanofibre nanopaper.

Originality/value

The outcome of this study will help to fabricate the SMP composite with high electrical actuation effectiveness under low electrical voltage actuation.

Details

Pigment & Resin Technology, vol. 45 no. 2
Type: Research Article
ISSN: 0369-9420

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Article

Haibao Lu, Yongtao Yao and Long Lin

This paper aims to create and to study multifunctional shape memory polymer (SMP) composites having temperature-sensing and actuating capabilities by embedding…

Abstract

Purpose

This paper aims to create and to study multifunctional shape memory polymer (SMP) composites having temperature-sensing and actuating capabilities by embedding thermochromic particles within the polymer matrix.

Design/methodology/approach

The multifunctional materials were fabricated following a process consisting of blending (of the thermochromic particles and the SMP at various ratios), mixing, degasing, moulding and thermal curing, prepared by incorporating thermochromic particles within the polymer. The effect of the thermochromic particles on the thermomechanical properties and thermally responsive shape memory effect of the resulting multifunction SMP composites were characterised and interpreted.

Findings

It was found that exposure of the composites to temperatures above 70°C led to a pronounced change of their colour that was recorded by the thermal and electrical actuation approaches and was reproducibly reversible. It was also found that the colour of the composites was independent of the mechanical state of the SMP. Such effects enabled monitoring of the onset of the set/release temperature of the SMP matrix. Furthermore, the combination of thermochromic additive and the SMP resulted in significantly improved thermomechanical strength, absorption of infrared radiation and the temperature distribution of the SMP composites.

Research limitations/implications

The temperature-sensing and actuating capabilities of the polymeric shape memory composites developed through this study will help to extend the field of potential applications of such composites to fields including sensors, actuators, security labels and information dissemination, where colour indication is an advantageous feature.

Originality/value

The SMP composites capable of temperature sensing and actuating are novel.

Details

Pigment & Resin Technology, vol. 44 no. 4
Type: Research Article
ISSN: 0369-9420

Keywords

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Article

Haibao Lu, Yongtao Yao, Shipeng Zhu, Yunhua Yang and Long Lin

The purpose of this paper is a study aimed at overcoming the interface issue between nanopaper and polymer matrix in shape-memory polymer (SMP) composite laminates caused…

Abstract

Purpose

The purpose of this paper is a study aimed at overcoming the interface issue between nanopaper and polymer matrix in shape-memory polymer (SMP) composite laminates caused by their large dissimilarity in electrical/thermal conductive properties. The study attempted to develop an effective approach to fabricate free-standing carbon nanofibre (CNF) assembly in octagon shape formation. The structure design and thermal conductive performance of the resulting octagon-shaped CNF assembly were optimised and simulated.

Design/methodology/approach

The CNF nanopaper was prepared based on a filtration method. The SMP nanocomposites were fabricated by incorporating these CNF assemblies with epoxy-based SMP resin by a resin-transfer modelling technique. Thermal conductivity of the octagon-shaped CNF assembly was simulated using the ANSYS FLUENT software for structure design and optimisation. The effect of the octagon-shaped CNF on the thermomechanical properties and thermally responsive shape-memory effect of the resulting SMP nanocomposites were characterised and interpreted.

Findings

The CNF template incorporated with SMP to achieve Joule heating triggered shape recovery at a low electric voltage of 3-10 V, due to which the electrical resistivity of SMP nanocomposites was significantly improved and lowered to 0.20 O·cm by the CNF template. It was found that the octagon CNF template with 2 mm width of skeleton presented a highest thermally conductive performance to transfer resistive heat to the SMP matrix.

Research limitations/implications

A simple way for fabricating electro-activated SMP nanocomposites has been developed by using an octagon CNF template. Low electrical voltage actuation in SMP has been achieved.

Originality/value

The fabricated CNF template, the structure design and analysis of dynamic thermomechanical properties of SMP are novel.

Details

Pigment & Resin Technology, vol. 44 no. 3
Type: Research Article
ISSN: 0369-9420

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Article

Haibao Lu, Yongtao Yao and Long Lin

This article aims to present a systematic and up-to-date account of carbon-based reinforcements, including carbon nanotube (CNT), carbon nanofibre (CNF), carbon black…

Abstract

Purpose

This article aims to present a systematic and up-to-date account of carbon-based reinforcements, including carbon nanotube (CNT), carbon nanofibre (CNF), carbon black (CB), carbon fibre (CF) and grapheme, in shape-memory polymer (SMP) for electrical actuation.

Design/methodology/approach

Studies exploring carbon-based reinforcement in SMP composites for electrically conductive performance and Joule heating triggered shape recovery have been included, especially for the principle design, characterisation and shape recovery behaviour, making the article a comprehensive account of the systemic progress in SMP composite incorporating conductive carbon reinforcement.

Findings

SMPs are fascinating materials and have attracted great academic and industrial attention owing to their significant macroscopic shape deformation in the presence of an appropriate stimulus. The working mechanisms, the physico requirements and the theoretical origins of the different types of carbon-based reinforcement SMP composites have been discussed. Current research and development on the fabrication strategies of carbon-based reinforcement SMP composites have been summarised.

Research limitations/implications

A systematic review is to evaluate carbon-based reinforcements in SMPs for electrical actuation and discuss recent developments and future applications.

Practical implications

Carbon-based reinforcements in SMPs can be used as smart deployable space structure in the broad field of aerospace technologies.

Originality/value

To reveal the research and development of utilising CNT, CNF, CB, CF and grapheme to achieve shape recovery of SMP composites through electrically resistive heating, which will significantly benefit the research and development of smart materials and systems.

Details

Pigment & Resin Technology, vol. 43 no. 1
Type: Research Article
ISSN: 0369-9420

Keywords

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Article

haibao Lu, Yongtao Yao and Long Lin

This paper aims to present a phenomenological and quantitative model to study the constitutive relations and working mechanism for shape/temperature memory effect in…

Abstract

Purpose

This paper aims to present a phenomenological and quantitative model to study the constitutive relations and working mechanism for shape/temperature memory effect in polypyrrole (PPy)-based shape memory polymers (SMPs).

Design/methodology/approach

In this paper, the origin of relaxation law was used to theoretically predict the relationships between relaxation time and internal energy and temperature based on the thermodynamics of polymers.

Findings

A phenomenological model was proposed to quantitatively identify the factors that influence the stored mechanical energy, shape memory effect (SME) and temperature memory effect (TME) in PPy. Both structural relaxation law and Tool-Narayanaswamy (TN) model were used to couple the constitutive relations of stress and transition temperature as a function of relaxation frequency, respectively. Furthermore, the simulation of the phenomenological model was compared with experimental results reported in relevant literature for purpose of verification.

Research limitations/implications

Exploration of the working mechanism underpinning the experimental (or phenomenal) results and significant enhancement of the understanding of relevant experimental features reported previously.

Originality/value

The outcome of this study will provide a powerful phenomenological and quantitative tool for studies on SME and TME in SMPs.

Details

Pigment & Resin Technology, vol. 44 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

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Article

Haibao Lu, Aying Zhang, Yongtao Yao and Long Lin

– This paper aims to present a phenomenological model to investigate the underlying mechanism and predict the bio-inspired performance under different thermo-temporal conditions.

Abstract

Purpose

This paper aims to present a phenomenological model to investigate the underlying mechanism and predict the bio-inspired performance under different thermo-temporal conditions.

Design/methodology/approach

Flory-Rehner free-energy functions are applied to quantitatively identify the driving forces in the viscously bio-inspired response of a dynamic polymer network. Furthermore, the permeation transition equation is adopted to couple water gradient and water sorption/desorption into the free-energy function.

Findings

The results show that the influence of potential energy on deformation can be related to a stretching ratio that uniquely determines water sorption/desorption, locomotion frequency and contractile stress. Finally, by means of combining the free-energy function and Arrhenius equation, a phenomenological thermo-temporal model is developed and verified by the experimental results.

Research limitations/implications

This study focuses on exploring the theoretical mechanism and significantly enhances understanding of relevant experimental features reported previously.

Originality/value

The outcome of this study will provide a powerful phenomenological and quantitative tool for study on shape memory effect in bio-inspired polymers.

Details

Pigment & Resin Technology, vol. 45 no. 1
Type: Research Article
ISSN: 0369-9420

Keywords

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Article

Sainan Zhang and Xiankai Jiang

The purpose of this paper is to synthesize and characterize a series of two-component aromatic waterborne polyurethane (2K-WPU) which is composed of non-ionic and anionic…

Abstract

Purpose

The purpose of this paper is to synthesize and characterize a series of two-component aromatic waterborne polyurethane (2K-WPU) which is composed of non-ionic and anionic polyisocyanate aqueous dispersion and polyurethane polyol aqueous dispersion.

Design/methodology/approach

The polyisocyanate aqueous dispersion was synthesized through non-ionic and anionic hydrophilic modification procedures. The values of the hydrogen bonding index (HBI) and molecule structures of WPU were obtained by Fourier transform infrared (FTIR). The thermal, mechanical and water resistance properties of 2K-WPU films were investigated.

Findings

The appearance of non-ionic polyisocyanate aqueous dispersion and anionic polyisocyanate aqueous dispersion was colorless translucent pan blue and yellow opaque emulsions, respectively. FTIR not only showed that 2K-WPU was obtained from the polymerization of polyisocyanate component and polyhydroxy component by polymerization but also showed that the content of hydrogen bondings of anionic 2K-WPU (WPU 2) was higher than non-ionic 2K-WPU (WPU 1). The glass-transition temperature (Tg), storage modulus and water resistance of WPU 2 were higher than WPU1, whereas the thermal stability of WPU1 was better than WPU 2.

Practical implications

The investigation established a method to prepare a series of 2K-WPU which was composed of non-ionic or anionic polyisocyanate aqueous dispersion and polyurethane polyol aqueous dispersion. The prepared 2K-WPU film could be applied as substrate resin material in the field of waterborne coating.

Originality/value

The paper established a method to synthesize a series of 2K-WPU. The effect of HBI value and the molecule structure of soft segment on the thermal stability, mechanical and water resistance properties of 2K-WPU films were studied.

Details

Pigment & Resin Technology, vol. 47 no. 4
Type: Research Article
ISSN: 0369-9420

Keywords

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