Antecedents of construction project coalitions: a study of the Spanish construction industry

Research into the formation of alliances, relevant in the field of strategic management and especially, in the construction industry, is often explained in terms of interdependency and complementarities (exogenous factors). In contrast, the influence of a firm’s social relations networks (endogenous factors) has hardly been studied at all. Thus, a model is needed that includes both exogenous and endogenous factors as antecedents to the formation of strategic alliances in the construction industry. Cooperation in the construction sector is especially frequent, above all in public works programmes, as their scale requires coalitions of different‐sized firms. Accordingly, to explore how both exogenous and endogenous factors influence the formation of alliances, a social network analytical method—Multiple Regression Quadratic Assignment Procedure (MRQAP)—was applied to cooperative project coalitions in the Spanish public works construction sector from 2001–2007. Empirical findings confirm that construction companies form coalitions, principally on the basis of past alliances. Membership of business associations and groups is also a key factor, though the influence of geographic proximity is the most debatable result. In the construction industry, the formation of alliances is conditioned, among other factors, by previous social and economic relations that can generate the necessary information and trust for the selection of whichever partner is considered the most suitable for the development of the joint project.     

Effect of dietary and synthetic chelating agents on the intestinal absorption of lead

The effect of a number of dietary and synthetic chelating agents on the intestinal absorption of lead has been examined using the everted sac preparation and the tracer isotope ²⁰³Pb. All the agents examined increased lead transport into the serosal compartment. An explanation of the way in which these agents modify the model to describe lead transport is proposed.     

The discourse of ‘Respect for People’ in UK construction

A competency‐based review of professional quantity surveying is important for service excellence and has continuing relevance in the built environment of the 21^st century. A survey of quantity surveyors in professional practice in South Africa has provided a new perspective on the relative importance of competencies required for current and future quantity surveying services, and revealed notable gaps between the important competencies and current proficiency levels among practitioners. The survey was based on a structured questionnaire reflecting 23 defined competencies, which were derived from the literature and from in‐depth interviews with selected practitioners. The results indicated that technically orientated competencies were rated of highest importance for current services, while management orientated competencies were rated of higher importance for future services. The profession was rated as deploying below average proficiency levels in marketing, advanced financial management, leadership and general management, and project management, although these received high current and future importance ratings. The findings suggest that initial and continuing education and training of professional quantity surveyors should emphasize the development of management‐orientated competencies.     

Thermal and flammability performance of polypropylene composites containing melamine and melamine phosphate‐modified α‐type zirconium phosphates

In this article, melamine (MA) and melamine phosphate (MP) have been intercalated into α‐type zirconium phosphate (α‐ZrP) interlayer spaces. The structure and thermal properties of the corresponding powders, MA‐ZrP and MP‐ZrP, were ascertained by X‐ray diffraction, Fourier transform infrared spectra, X‐ray photoelectron spectroscopy measurement, and thermogravimetric analyses (TGA). Furthermore, polypropylene (PP) and its intumescent flame retardant (IFR) composites containing the two organically modified α‐ZrP powders using maleic anhydride‐grafted PP (JPP) as compatibilizer were fabricated by melt blending. The results from TGA and cone calorimetry demonstrated that PP/JPP and PP/JPP/IFR composites containing MA‐ZrP and MP‐ZrP exhibited better thermal stability and burning behavior in comparison with their corresponding counterparts, PP/JPP and PP/JPP/IFR, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40254.     

In situ biaxial stretching for the platelet formation of an ethylene–vinyl alcohol copolymer through multistage stretching extrusion and its effect on the gas‐barrier properties of polyethylene

The morphological evolution of ethylene–vinyl alcohol copolymer (EVOH) and its effect on the gas‐barrier properties of high‐density polyethylene (HDPE) were investigated. HDPE/EVOH blends were prepared through a multistage stretching extrusion, which combined an assembly of force‐assembling elements (FAEs) with an extruder. Scanning electron microscopy confirmed that with an increasing number of FAEs, the biaxial‐stretching field existing in each FAE transformed the dispersed EVOH phase into well‐defined platelets along the flowing plane. Dynamic rheological results further revealed that the formation of the platelets enlarged the interfaces between the dispersed barrier phase and the matrix; this not only led to the decline of the complex viscosity but also created more tortuous paths for the diffusion of gas molecules. Compared with that of the non‐FAE specimen blended with 25 wt % EVOH, the oxygen permeability coefficient decreased more than one order of magnitude when one FAE was applied. The structural model for permeability indicated that the enhanced barrier resulted from the increased tortuosity of the diffusion pathway, which was provided by the aligned high‐aspect‐ratio platelets. Compared with the previous biaxial‐stretching method, multistage stretching extrusion provided a simple and economical way to generate a laminar structure of the dispersed phase in the matrix phase without the application of an external stretching force. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40221.     

Effect of the crosslinking density and programming temperature on the shape fixity and shape recovery in epoxy–anhydride shape‐memory polymers

In addition to the fabrication of thermoset epoxy–anhydride shape‐memory polymers (SMPs), a systematic experimental investigation was conducted to characterize the crosslinking density, micromorphology, thermal properties, mechanical properties, and shape‐memory effects in the epoxy SMP system, with a focus on the influence of the crosslinking density and programming temperature on the shape‐fixity and shape‐recovery behaviors of the polymers. On the basis of the crosslinking density information determined by NMR technology, we concluded that the effect of the crosslinking density on the shape‐fixity behaviors was dependent on the programming temperature. The advantage of a nice combination of crosslinking density and programming temperature provided an effective approach to tailor the actual shape recovery within a wide range. The increasing crosslinking density significantly improved the shape‐recovery ratio, which could be further improved through a decrease in the programming, whereas the crosslinking density was more fundamental. This exploration should play an important role in the fabrication and applications of SMP materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40559.     

Investigations of environmental stress cracking resistance of HDPE/EVA and LDPE/EVA blends

HDPE/poly(ethylene‐co‐vinylacetate) (EVA) and low‐density polyethylene (LDPE)/EVA blends were tested and compared with respect to their environmental stress cracking resistance (ESCR) using the Bell‐telephone test. The time to failure in the ESCR test improves with increasing EVA content, and considerable improvements were produced for LDPE/EVA blends while small improvements were observed for HDPE/EVA blends. Thermal, rheological, mechanical, and morphological studies were conducted which established a quantitative relationship between morphological features and composition. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39880.     

Preparation and characterization of poly(ethylene terephthalate) copolyesters modified with sodium‐5‐sulfo‐bis‐(hydroxyethyl)‐isophthalate and poly(ethylene glycol)

Two types of poly(ethylene terephthalate) (PET) copolyesters were successfully prepared with sodium‐5‐sulfo‐bis‐(hydroxyethyl)‐isophthalate (SIPE) and poly(ethylene glycol) (PEG) units with different molecular weights named as cationic dyeable polyester and easy cationic dyeable polyester. Their chemical and crystalline structures were characterized by the nuclear magnetic resonance (NMR), wide angle X‐ray diffraction (WAXD), and small angle X‐ray scattering measurement, and their thermal properties were tested by differential scanning calorimetry and thermogravimetric analysis, respectively. NMR experimental results showed that the actual molar ratio of comonomers was basically consistent with the correlative feed ratio. WAXD results indicated that the crystalline structures of prepared copolyesters were similar to that of PET. Moreover, the glass transition temperature, melting temperature, and thermal degradation temperature were found to decrease with the reduction of the of PEG units as the incorporation of lower of PEG units brought more ether bonds into molecular chains, which increased the irregularity of molecular chain arrangement and led to lower crystallinity. In addition, because the incorporation of PEG units with lower molecular weight led to more ether bonds and hydroxyl end‐groups in molecular chains, the value of contact angle of PET copolyesters dropped, manifesting PET copolyesters had better hydrophilicity with the decreasing molecular weight of PEG units.© 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39823.     

Fracture mechanical analysis of two commercial polyoxymethylene homopolymer resins

This research addresses the fracture mechanical analysis of two commercially available polyoxymethylene homopolymer resins. Two types of experiments are used: monotonic fracture toughness tests and cyclic fatigue crack growth tests. The resulting total lifetimes in the fatigue crack growth tests are split up into the appropriate parts of crack growth initiation and fatigue crack propagation. Fracture surfaces of monotonic and cyclic tests are analyzed using light microscopy and scanning electron microscopy. Besides the mechanical tests, the morphology within the used compact tension specimens is examined in detail by using differential scanning calorimetry, small‐ and wide‐angle X‐ray scattering, and polarized light microscopy. The results are analyzed and discussed, considering observations in the previous studies published in the literature. It is shown that both materials can be well analyzed using linear elastic fracture mechanics and their fracture mechanical properties are presented in conjunction with a detailed documentation of the microstructure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40831.     

Effect of solid‐state shear milling on structure and properties of HDPE/UHMWPE blends

The structure and properties of HDPE/UHMWPE blends prepared through a pan‐milling reactor in solid state at ambient temperature were compared with the blends made by melt mixing. The changes of structure and properties of the blends were investigated by FTIR, melt flow index, mechanical properties, dynamic rheological measurement, DSC, and WAXD. DSC measurement illustrated that after pan‐milling treatment, the half‐width of the melting temperature became smaller. The more content of UHMWPE added in the blend, the more evident change was observed. Combined with the dynamic rheological analysis, it was proved that, the pan‐milling treatment can improve the compatibility of the HDPE/UHMWPE blends. X‐ray diffraction analysis showed that after pan‐milling treatment some ordered structure could be induced, but after heat treatment, the induced crystalline structure disappeared. The tensile properties of pan‐milled HDPE/UHMWPE blends also achieved improvement after pan milling treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39916.