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Article
Publication date: 26 August 2014

Zhifeng Huang, Xiaoyang Ma, Zemin Qiao, Shujuan Wang and Xinli Jing

This paper aims to disclose the evolution of pendulum hardness of two-component acrylic polyurethane coatings during the cure process and attempts to describe the…

Abstract

Purpose

This paper aims to disclose the evolution of pendulum hardness of two-component acrylic polyurethane coatings during the cure process and attempts to describe the quantitative relationship between pendulum hardness and curing time. These findings are helpful for the study of fast curing acrylic polyurethane coatings.

Design/methodology/approach

The pendulum hardness method was used to monitor the hardness of two-component acrylic polyurethane coatings during curing. The quantitative relationship between pendulum hardness and curing time can be obtained with Avrami equation.

Findings

The evolution of coating pendulum hardness can be divided into three stages. By using the Avrami equation that explained the influence of both the acid value and the curing temperature on the drying speed of hydroxyl acrylic resin, the evolution of coating pendulum hardness during curing can also be accurately described.

Research limitations/implications

It should be noted that the physical meaning of the Avrami exponent, n, is not yet clear.

Practical implications

The results are of great significance for the development of fast-curing hydroxyl-functional acrylic resins, with the potential to improve the drying speed of the coatings used in automotive refinish.

Originality/value

It is novel to divide the pendulum hardness into three stages, and, for the first time, the Avrami equation is utilized to describe the evolution of coating pendulum hardness during curing.

Details

Pigment & Resin Technology, vol. 43 no. 5
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 30 June 2020

Kaili Yao, Dongyang Chu, Ting Li, Zhanli Liu, Bao-Hua Guo, Jun Xu and Zhuo Zhuang

The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution…

Abstract

Purpose

The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution and the hydrogen bond dissociation of polyurea under high-speed shock.

Design/methodology/approach

The atomic-scale simulations are achieved by molecular dynamics (MD). Both non-equilibrium MD and multi-scale shock technique are used to simulate the high-speed shock. The energy dissipation is theoretically derived by the thermodynamic and the Hugoniot relations. The distributions of bond length, angle and dihedral angle are used to characterize the chain conformation evolution. The hydrogen bonds are determined by a geometrical criterion.

Findings

The Hugoniot relations calculated are in good agreement with the experimental data. It is found that under the same impact pressure, polyurea with lower hard segment content has higher energy dissipation during the shock-release process. The primary energy dissipation way is the heat dissipation caused by the increase of kinetic energy. Unlike tensile simulation, the molecular potential increment is mainly divided into the increments of the bond energy, angle energy and dihedral angle energy under shock loading and is mostly stored in the soft segments. The hydrogen bond potential increment only accounts for about 1% of the internal energy increment under high-speed shock.

Originality/value

The simulation results are meaningful for understanding and evaluating the energy dissipation mechanism of polyurea under shock loading, and could provide a reference for material design.

Details

Engineering Computations, vol. 38 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 18 November 2013

Mica Grujicic, Jennifer Snipes, Subrahmanian Ramaswami, Rohan Galgalikar, James Runt and James Tarter

Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a…

Abstract

Purpose

Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft (i.e. low glass transition temperature) matrix. A number of experimental investigations reported in the open literature clearly demonstrated that the use of polyurea external coatings and/or internal linings can significantly increase blast survivability and ballistic penetration resistance of target structures, such as vehicles, buildings and field/laboratory test-plates. When designing blast/ballistic-threat survivable polyurea-coated structures, advanced computational methods and tools are being increasingly utilized. A critical aspect of this computational approach is the availability of physically based, high-fidelity polyurea material models. The paper aims to discuss these issues.

Design/methodology/approach

In the present work, an attempt is made to develop a material model for polyurea which will include the effects of soft-matrix chain-segment molecular weight and the extent and morphology of hard-domain nano-segregation. Since these aspects of polyurea microstructure can be controlled through the selection of polyurea chemistry and synthesis conditions, and the present material model enables the prediction of polyurea blast-mitigation capacity and ballistic resistance, the model offers the potential for the “material-by-design” approach.

Findings

The model is validated by comparing its predictions with the corresponding experimental data.

Originality/value

The work clearly demonstrated that, in order to maximize shock-mitigation effects offered by polyurea, chemistry and processing/synthesis route of this material should be optimized.

Details

Multidiscipline Modeling in Materials and Structures, vol. 9 no. 4
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 30 July 2021

Lihong Bao, Suyi Cao and Lin Tu

This paper aims to provide a flexible polyurethane (PU) film with visible light trapping ability, photothermal conversion and energy storage performance by covalently…

Abstract

Purpose

This paper aims to provide a flexible polyurethane (PU) film with visible light trapping ability, photothermal conversion and energy storage performance by covalently bonded a visible light absorbing dye into the polymer through copolymerization.

Design/methodology/approach

For this target solution copolymerization of diphenyl-methane-diisocyanate (MDI), poly(1,4-butylene adipate) (PBA2000), polyethylene glycol (PEG) of different molecular weight, self-made dye, 1,4-butanediol (BuOH) was carried out in a flame-dried flask under an inert nitrogen (N2) atmosphere. First, an isocyanate-terminated prepolymer of dried PEG, MDI and PBA2000 was prepared in dimethylformamide and stirred for 1 h at 35°C. Then, self-made dye and 1, 4-butanediol (BuOH) were added and heated at 85°C for 3 h to get photothermal conversion polyurethane (PTPU) solution. Allowed the solution to dry at room temperature for seven days and then at 65°C for 12 h to get PTPU films.

Findings

The flexible PU films with photothermal conversion and energy storage performances were successfully synthesized and the functional films presented both excellent energy storage and mechanical property when the molecular weight of PEG was in the range of 6,000∼10,000.

Research limitations/implications

The materials that were used in this research paper had a reasonably low cost. Also, the procedures for the synthesis of dye and polymers were extremely easy because there was no need for high pressure or temperature and no dangerous solvents were used.

Practical implications

The photothermal conversion property and mechanical performance of the synthesized flexible PU films were characterized. The results have proved that these films were soft and elastic, and have certain photothermal conversion and energy storage ability, thus can be used in the surface finishing of special fabric and leather.

Originality/value

Visible light trapping photothermal conversion PU flexible film with energy storage capability was prepared for the first time.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 August 2008

Robert Bogue

The purpose of this paper is to provide a review of recent progress in self‐assembly technology, principally in the microelectronics context.

Abstract

Purpose

The purpose of this paper is to provide a review of recent progress in self‐assembly technology, principally in the microelectronics context.

Design/methodology/approach

First, the paper discusses the application of nanoscale self‐assembly techniques to microelectronic and related components and then considers research involving larger devices.

Findings

The paper shows that a range of self‐assembly techniques is being used to fabricate both production and experimental microelectronic devices, often with the aim of developing alternatives to copper wire interconnects. Other, experimental self‐assembly techniques are being developed for the packaging and mounting of microelectronic components on substrates.

Originality/value

Provides a useful, detailed review of the use of self‐assembly techniques at the nanoscale, microscale and macroscale.

Details

Assembly Automation, vol. 28 no. 3
Type: Research Article
ISSN: 0144-5154

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Article
Publication date: 1 December 2005

George K. Stylios

Examines the eleventh published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects…

Abstract

Examines the eleventh published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects. Subjects discussed include cotton fabric processing, asbestos substitutes, textile adjuncts to cardiovascular surgery, wet textile processes, hand evaluation, nanotechnology, thermoplastic composites, robotic ironing, protective clothing (agricultural and industrial), ecological aspects of fibre properties – to name but a few! There would appear to be no limit to the future potential for textile applications.

Details

International Journal of Clothing Science and Technology, vol. 17 no. 6
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 11 January 2011

Vilas D. Athawale and Mona A. Kulkarni

The aim of this paper is to synthesise polyester/silica hybrid resins and their hybrid polyurethanes via in situ (IS) and blending (BL) methods and to evaluate the effect…

Abstract

Purpose

The aim of this paper is to synthesise polyester/silica hybrid resins and their hybrid polyurethanes via in situ (IS) and blending (BL) methods and to evaluate the effect of preparation method, interaction type and silica content on the physico‐chemical and thermal properties of polyurethane/silica (PU/Silica) hybrid coatings.

Design/methodology/approach

Silica particle‐containing silica sol was prepared according to Stöber method using tetraethylorthosilicate as the precursor and then introduced into polyester matrix by in situ and direct blending method. The modified polyester/silica resin was further crosslinked with TMP‐TDI adduct to synthesise PU/Silica hybrid coatings and studied for thermo‐mechanical, physico‐chemical properties.

Findings

It was found IS polymerisation caused more polyester segments to chemically bond onto the surface of silica particles than BL process. Results also reveal that due to stronger interaction between silica particles and PU matrix, hybrid resins prepared by IS method confers better properties than BL method and exhibit optimal properties at the critical concentration of 8 wt% silica.

Research limitations/implications

In the present study, silica particles are used to modify properties of polyurethane resins. Many other countless combinations in terms of inorganic filler or organic matrices can be explored to obtain a wide range of interesting properties and applications.

Practical implications

The results obtained in this study will be extremely useful to enhance the understanding of this class of hybrid materials.

Originality/value

Hybrid organic‐inorganic networks offer a new area of material science that has extraordinary implications for developing novel materials that exhibit a diverse range of multi‐functional properties.

Details

Pigment & Resin Technology, vol. 40 no. 1
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 21 March 2008

A. Elidrissi, O. Krim and S. Ousslimane

To evaluate in the first stage, the efficiency of changing the nature and the length of diols on the properties of perfectly hard sequences polyurethanes (PU). In the…

Abstract

Purpose

To evaluate in the first stage, the efficiency of changing the nature and the length of diols on the properties of perfectly hard sequences polyurethanes (PU). In the second, the thermal properties of a new series of segmented PU with different concentrations of soft sequences were determined.

Design/methodology/approach

The synthesis of segmented PU has been realised in two stages known as the pre‐polymer method. Various compositions of PU were obtained by keeping the poly(tetramethylene glycol) – PTMG molecular weights constant, but varying its concentration. The products obtained were characterised by IR, NMR, gel permeation chromatography and studied by differential scanning calorimetry.

Findings

The level of phase segregation depends on several parameters, especially the nature of the soft segment and its average molecular weight, nature of the hard sequence and the number of hydrogen bonds established in the PU sequences.

Research limitations/implications

The segmented PU obtained were synthesised from PTMG of number molecular weight 2,000. They could also be synthesised from PTMG of molecular weight 600, 1,000, 2,000, 4,000, etc. The effect of change of PTMG molecular weight on PU properties could also be studied.

Practical implications

Better understanding of the morphology of segmented PU and its effect in the practical domains.

Originality/value

Novel perfectly hard sequences PU have been synthesised and characterised. The effect of soft sequence nature and concentration on the phase segregation in these new series of segmented PU is discussed.

Details

Pigment & Resin Technology, vol. 37 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 2 March 2020

Yongfeng Liu, Yi Liu and Duolong Di

The purpose of this study is to focus on the preparation of macroporous adsorption resins (MARs) functionalized with carbazole and N-methylimidazole, and adsorption…

Abstract

Purpose

The purpose of this study is to focus on the preparation of macroporous adsorption resins (MARs) functionalized with carbazole and N-methylimidazole, and adsorption behaviors of (–)-epigallocatechin gallate (EGCG) and caffeine (CAF) on the functionalized MARs.

Design/methodology/approach

Based on the Friedel–Crafts and amination reactions, novel MARs functionalized with carbazole and N-methylimidazole were synthesized and characterized by the BET method. Accordingly, adsorption behaviors and structure-activity relationships for EGCG and CAF were studied in detail.

Findings

The results showed that pseudosecond-order kinetic model was provided with a better correlation for the adsorption of EGCG and CAF onto L-1 and L-2, and pseudofirst-order kinetic model was the most suitable model to illustrate the adsorption process for EGCG and CAF on L-3. The result indicated that Langmuir, Freundlich, Temkin–Pyzhev and Dubinin–Radushkevich isotherms all could better illustrate the adsorption processes of EGCG and CAF on L-1, L-2 and L-3.

Practical implications

This study provides theoretical guidance and technical support for the efficient separation and purification of EGCG and CAF from waste tea leaves by MARs on a large scale. In addition, the results showed that this novel MARs would provide useful help and be used in large-scale production of active ingredients from natural products in the industry and other fields.

Originality/value

Adsorption kinetic models such as pseudofirst-order, pseudosecond-order and intra-particle diffusion kinetic models, and adsorption isotherm models such as Langmuir, Freundlich, Temkin–Pyzhev and Dubinin–Radushkevich isotherms models were adopted to illustrate the adsorption mechanisms of EGCG and CAF. The main driving forces for MARs with no functional groups were pore sieving effects, pp conjugation effects and hydrophobic interactions, and the other significant driving forces for MARs functionalized with carbazole and N-methylimidazole were electrostatic interactions, ion-dipole and hydrogen bonding interactions. This study might provide scientific references and useful help for large-scale separating and enriching active ingredients in natural products using the technology of MARs with special functional groups.

Details

Pigment & Resin Technology, vol. 49 no. 3
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 29 June 2012

Manzoor Ahmad, J. Luo, Ben Xu, Hendra Purnawali, Peter King, Paul Chalker, Yongqing Fu, Weimin Huang and Moshen Miraftab

Shape memory polyurethanes (SMPUs) are typically synthesized using polyols of low molecular weight, Mw, and high hydroxyl number as it is believed that high density of…

Abstract

Shape memory polyurethanes (SMPUs) are typically synthesized using polyols of low molecular weight, Mw, and high hydroxyl number as it is believed that high density of cross-links in these polyols are essential for high performance shape memory polymers. In this study, polyethylene glycol (PEG-6000) with Mw ~ 6000 g/mol and low hydroxyl number (OH ~ 18 mg K OH/g) as the soft segment and diisocyanate as the hard segment were used to synthesize SMPUs. It revealed that although the PEG-6000 based SMPUs have lower maximum elongation at break (425%) and recovery stress than those of PCL-2000 polyol based SMPUs, they have much better shape recovery ratio (98%) and shape fixity (95%). Furthermore, these SMPUs showed a much shorter actuation time of <10sec for up to 85% shape recovery, much shorter than those low Mw SMPUs, clearly demonstrated their great potential for applications.

Details

World Journal of Engineering, vol. 9 no. 3
Type: Research Article
ISSN: 1708-5284

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