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1 – 10 of over 14000A.K. Khan, B.C. Ray, J. Maiti and S.K. Dolui
The purpose of this paper is to study the effect of monomer composition in core‐shell latex prepared from co‐polymer of styrene‐butylacrylate (BA)‐methyl methacrylate (MMA) and…
Abstract
Purpose
The purpose of this paper is to study the effect of monomer composition in core‐shell latex prepared from co‐polymer of styrene‐butylacrylate (BA)‐methyl methacrylate (MMA) and their paint properties.
Design/methodology/approach
The core‐shell latex was prepared by a stepwise semi‐batch emulsion polymerisation. A set of dispersion was made with the different core‐shell compositions. The core phase consists of a copolymer of styrene‐BA‐acrylic acid (AA) and the shell phase consists of a copolymer of MMA‐AA. The properties of latex were determined by solid content, viscosity, pH and particle size. Subsequently, emulsion paint (PVC‐37 per cent and NVM‐53 per cent) was prepared using core‐shell latex. The paint properties were determined by block resistance, gloss, elongation at break, etc. The particle morphology was characterised with transmission electron microscope (TEM).
Findings
Core‐shell structure of latex was confirmed by TEM. The performance of core‐shell latex has been optimised and the best combination achieved with 25‐40 per cent of hard phase in core‐shell latex.
Research limitations/implications
Although the core‐shell structured latex was prepared from co‐polymer of styrene‐BA‐MMA monomer, the system could be extended with other monomers depending on the end use of surface coating.
Practical implications
The paint industry may use this method to improve paint properties.
Originality/value
The paper shows that, by use of core‐shell latex, it is possible to achieve high‐block resistance, hardness, elasticity and gloss.
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Abstract
Purpose
The purpose of this paper is to prepare a kind of novel multi‐layer core‐shell latex, and to evaluate the effect of the preparation methodology.
Design/methodology/approach
Core‐shell poly(siloxane)/polystyrene/polymethyl methacrylate (PSi/PSt/PMMA) latex particles were prepared by seeded‐emulsion polymerisation with three stages. The core of cured PSi was prepared with octamethyl cyclotetrasiloxane (D4) and tetraethoxysilane (TEOS) by co‐condensation. Using vinyltriethoxysilane (VTEOS) as coupling agent, functional PSi particles with vinyl groups on surfaces were prepared by hydrolysis and condensation of VTEOS in core formation stage. Then, the functional PSi particles were used as seeds to copolymerise with styrene and methyl methacrylate sequentially in shell stage I and stage II to form PSi/PSt/PMMA latex particles.
Findings
FTIR, TEM, DSC and XPS showed that the PSi/PSt/PMMA latex particles had multi‐layer core‐shell structure with cured PSi as core, PSt as shell I and PMMA as shell II.
Research limitations/implications
In the present work, PSi/PSt/PMMA latex particles having multi‐layer core‐shell structure with cured PSi as core, PSt as shell I and PMMA as shell II were prepared. This methodology can be employed to prepare new functional materials for various applications.
Practical implications
Multi‐layer core‐shell particles offer a new area of material science that has wide applications in coatings or modified polymer materials production.
Originality/value
The method developed in the study reported in this paper provides a new strategy to develop new types of core‐shell materials with multi‐layer structure.
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Neri Volpato and Thomas H.C. Childs
Selective laser sintering can be used to manufacture injection mould inserts using an indirect metal laser sintering process, such as the RapidTool™ process commercialised by 3D…
Abstract
Selective laser sintering can be used to manufacture injection mould inserts using an indirect metal laser sintering process, such as the RapidTool™ process commercialised by 3D Systems. The volume of material to be laser processed for insert manufacturing is very high when compared to that for plastic prototype manufacturing. Consequently, the time involved in the laser processing is also very long. This paper describes the development and assessment of shelling strategies to be applied in an indirect rapid tooling process aimed at reducing time in the process. The feasibility of the shelling idea has been confirmed and although the scanning system offers some limitations to the idea two strategies are presented as successful, open shell and closed shell, with a great potential to save time.
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Alan Elliott Richardson and Thomas Fuller
The purpose of this paper is to examine the use of a waste marine sea shell product incorporated into a concrete mix as an aggregate replacement. Utilising shells reduces the…
Abstract
Purpose
The purpose of this paper is to examine the use of a waste marine sea shell product incorporated into a concrete mix as an aggregate replacement. Utilising shells reduces the storage of shell waste, also reducing the need for quarried aggregate and has potential benefits of adding a different material to a design mix concrete mix design for improved performance.
Design/methodology/approach
The test methods used to evaluate the concrete were, British Standard tests for compressive strength (BS EN 12390-3:2002) and porosity (BS EN 12390-8:2009). A paired comparison test was carried out examining two different partial replacement shell aggregate mixes against a plain concrete control sample.
Findings
The results showed a reduction in compressive strength when 50 per cent of sea shells were used as an aggregate replacement, for both sand and gravel, compared to the control sample. Crushed and graded sea shells used in concrete displayed a lower porosity/permeability than plain concrete.
Originality/value
Whilst there is existing work relating to the compressive strength of concrete using sea shells, the porosity of concrete using sea shells has not been widely addressed and the paper investigates this aspect of sustainable concrete research.
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W.L. Yao and Ming C. Leu
This paper presents a numerical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser…
Abstract
This paper presents a numerical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography patterns. Considered are the cracking temperature of the ceramic shell, the buckling temperature of the web link, and the glass transition temperature of the epoxy resin. Our hypothesis is that shell cracking will occur if the ceramic rupture temperature is lower than the temperature of glass transition and the temperature of web buckling. This hypothesis is validated by a good agreement we obtained between experimental observations and numerical simulations. It is found that the shell cracking and web link buckling are strongly related to the cross‐sectional dimensions and span length of the web structure and the shell thickness, and that shell cracking can be prevented by buckling of the epoxy webbed pattern in early stages of the burnout process.
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E. HINTON, S.M.B. AFONSO and N.V.R. RAO
The optimization of variable thickness plates and shells is studied. In particular, three types of shell are considered: hyperbolic paraboloid, conoid and cylindrical shell. The…
Abstract
The optimization of variable thickness plates and shells is studied. In particular, three types of shell are considered: hyperbolic paraboloid, conoid and cylindrical shell. The main objective is to investigate the optimal thickness distributions as the geometric form of the structure changes from a plate to a deep shell. The optimal thickness distribution is found by use of a structural optimization algorithm which integrates the Coons patch technique for thickness definition, structural analysis using 9‐node Huang‐Hinton shell elements, sensitivity evaluation using the global finite difference method and the sequential quadratic programming method. The composition of the strain energy is monitored during the optimization process to obtain insight into the energy distribution for the optimum structures. Several benchmark examples are considered illustrating optimal thickness variations under different loading, boundary and design variable linking conditions.
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Archaeological evidence from the prehistoric Spondylus industry of coastal Ecuador is analyzed here to clarify how craft production was structured and the role that it played in…
Abstract
Archaeological evidence from the prehistoric Spondylus industry of coastal Ecuador is analyzed here to clarify how craft production was structured and the role that it played in the rise of social complexity. Many models of social development propose that elite cooption of specialized craft production can be a useful avenue through which aspiring elites can gain differential status. Contrary to the expectations of these models, data from coastal Ecuador indicates that craft production of sumptuary goods was an activity primarily carried out by household units for the benefit of the domestic economy. Increased trafficking with northern Peruvian states at ca. 750 seems to have promoted local social stratification by attracting large numbers of households to the restricted locales where they could exploit these resources, which in turn prompted a strengthening of the kinds of political conditions that facilitate orderly interaction and minimize internal social conflict.
The focus of the chapter is on disputes around corporate social responsibility (CSR) in the fossil fuel industry and how media and social networking technologies are deployed in a…
Abstract
Purpose
The focus of the chapter is on disputes around corporate social responsibility (CSR) in the fossil fuel industry and how media and social networking technologies are deployed in a virtual war between oil corporations and dissident, activist and protest groups.
Methodology/approach
Communications by BP, Shell, and their opponents in this virtual war are compared, especially in relation to the creative use of the internet, digital technologies, and social media. Through a case study approach, the chapter shows how communications often center on contested notions of CSR and claims by the oil giants about their environmental impact, which opponents dismiss as “greenwashing.” The various techniques deployed by both sides in this wide-ranging “PR war” are explored and contrasted in detail.
Findings
The findings for each case study reveal the diverse, complex, and changing nature of the relationship between the oil industry and its critics. The chapter concludes by arguing that if CSR is seen as “greenwashing” by the public, it is only likely to fuel widespread skepticism of the oil and gas sector and of corporate claims about the environment more generally.
Research limitations/implications
The research offers a snapshot of online and social media campaigns and PR strategies and tactics within the oil and gas industry rather than empirically grounded set of findings that can be easily applied to other fields.
Practical implications
Practical implications include attention to inflated or understated claims and the use of citizen testimony and humor to puncture CSR “rhetoric.” There is consideration of use of digital technologies by activists and attention to the way public debates and consultations are conducted. The need for a more respectful engagement with local communities by all parties engaging in public relations is underlined.
Originality/value
The chapter applies the concept of “asymmetrical warfare” from conflict studies within the media and communications tradition to provide a fresh revaluation of the term “PR war,” It offers a rare focus on online efforts by activist to subvert CSR-related branding, marketing, and communications. Discussion of the use of parody alongside factual and emotional arguments to challenge corporate hegemony also provides revealing insights.