Organisational routines and interfirm collaboration : measurement dilemmas and recommendations for further research steps

Purpose: The paper aims mainly to present the results and consequences of measurement inaccuracies and to make recommendations for further research. Design/Methodology/Approach: We began our research by providing studies on the theoretical origins of constructs in survey questions. Specifically, we studied the theorems and related constructs. We then reviewed the measurement of the constructs, selecting reliable scales. We conducted an initial study on 101 firms in Poland randomly selected from the high-technology sector, specifically the IT sector. We selected an industry in which inter-firm relationships are common. They are distinguished by high innovation, short product and process life cycles and therefor require many relationships to meet customer expectations. The respondents were top managers. The inclusive criterion was their employment of at least five employees. Collected data were analysed with Statistica 13 software (TIBCO Software Inc. (2017). Findings: After solving measurement dilemmas we made methodological recommendations regarding population structure and scales revealing particular constructs. Originality/Value: The implementation of the recommendations aforementioned would allow to formulate and verify hypotheses resulting from the propositions we have formulated while proposing our research framework. Additionally, we obtained a new Propensity to Collaborate scale as the questions referred to particular dimensions joined in quite different groups. Hence, one item has been deleted and the dimensions have been combined. We propose to check the new scale (without dimensions) in the future research.peer-reviewe

A fundamental rule: determining the importance of flow prior to polymer crystallization

A continuum-level model for non-isothermal polymer crystallization following a complex flow is presented, along with a fundamental rule that may be employed to determine if the flow will influence the ensuing crystallization dynamics. This rule is based on two dimensionless parameters: the (Rouse) Weissenberg number, and an inverse Deborah number de�ned by the ratio between the time taken to cool to the melting point versus the stretch relaxation time, which determines the time available for flow-enhanced crystallization. Moreover, we show how the time to reach the melting point can be derived semi-analytically and expressed in terms of the processing conditions in the case of pipe flow - ubiquitous in polymer processing. Whilst the full numerical model is required to quantitatively predict induction times and spherulite-size distributions, the proposed fundamental rule may be used practically to ensure, or eliminate, flow-enhanced structures by controlling the processing conditions or material properties. We discuss how ow-enhanced structures may be revealed only after post-processing annealing, and finally examine previous works that have successfully applied the model to extrusion-based three-dimensional (3D) printing

Kinetic Model for Layer-by-Layer Crystal Growth in Chain Molecules

A kinetic model is proposed to describe the structure and rate of advancement of the growth front during crystallization. Solidification occurs through the mechanisms of surface nucleation and lateral spreading of the solid phase within layers in the vicinity of the growth front. The transformation from liquid to solid within each layer is described by an equation similar to the two-dimensional variant of the Johnson–Mehl–Avrami (JMA) equation, but in which the finite size and shape of the critical nucleus and the dynamic evolution of the solid fraction of the underlying layers are taken into account. Connection to the regime theory of Hoffman and co-workers, for surface nucleation and spreading in one or two dimensions, is also made. Given only molecular level information regarding surface nucleation rates, lateral spreading rates, and critical surface nucleus geometry, the resulting set of coupled nonlinear equations for solidification in each layer is numerically integrated in time to obtain the structure and rate of advancement of the growth front, for arbitrarily large systems and long times. Using this kinetic model with input parameters obtained from molecular dynamics simulations, a multiscale modeling analysis of crystal growth in n-pentacontane (C50) is performed.National Science Foundation (U.S.) Division of Civil, Mechanical and Manufacturing Innovation (CMMI-1235109

Advances in modeling transport phenomena in material-extrusion additivemanufacturing: Coupling momentum, heat, and mass transfer

Material-extrusion (MatEx) additive manufacturing involves layer-by-layer assembly ofextruded material onto a printer bed and has found applications in rapid prototyping.Both material and machining limitations lead to poor mechanical properties of printedparts. Such problems may be addressed via an improved understanding of thecomplex transport processes and multiphysics associated with the MatEx process.Thereby, this review paper describes the current (last 5 years) state of the art modelingapproaches based on momentum, heat and mass transfer that are employed in aneffort to achieve this understanding. We describe how specific details regardingpolymer chain orientation, viscoelastic behavior and crystallization are often neglectedand demonstrate that there is a key need to couple the transport phenomena. Such acombined modeling approach can expand MatEx applicability to broader applicationspace, thus we present prospective avenues to provide more comprehensive modelingand therefore new insights into enhancing MatEx performanc

Struktura oraz termiczne i mechaniczne właściwości kompozytów polipropylenu z nano- i mikro-diamentami

The influence of diamond powders on properties of isotactic polypropylene (PP) was investigated. PP composites containing 0.2—5 wt % of the powders with particles of average size between 100 nm and 1 µm were prepared, and their structure and properties were examined. Dispersion of each filler depended on its grain size and content. The presence of fillers raised the crystallization temperature of PP matrix by up to few Celsius degrees. The modulus of elasticity of composites increased with increasing filler content, by up to 40 % in comparison to neat PP. The tensile impact strength of the composites with 1µm powders and also the other composites at the filler content as low as 0.2 wt % improved by up to 30%. The composites did not exhibit any decrease in the yield strength and retained good drawability. The elongation at break exceeded 1000 % in most cases. Examination of the uniaxially drawn specimens revealed that the filler grains separated from the PP matrix during drawing.Badano wpływ proszków diamentowych na właściwości izotaktycznego polipropylenu (PP). Wytworzono kompozyty PP zawierające 0,2—5 % mas. proszków ośrednich rozmiarach cząstek wzakresie od 100 nm do 1 µm oraz zbadano ich strukturę i właściwości. W każdym przypadku dyspersja napełniacza zależała od rozmiarów ziaren i ich zawartości w kompozycie. Obecność napełniaczy wywołała podwyższenie, maksymalnie o kilka stopni Celsjusza, temperatury krystalizacji matrycy polipropylenowej. Moduł sprężystości kompozytów zwiększał się wraz ze zwiększeniem zawartości napełniacza (maksymalnie o 40 %). Odporność na zerwanie udarowe kompozytów z proszkami o ziarnach wielkości 1µm oraz pozostałych kompozytów z zawartością napełniaczy wynoszącą 0,2 % mas., wzrosła, maksymalnie o 30 %. Naprężenie na granicy plastyczności kompozytów nie uległo zmniejszeniu, została też utrzymana dobra ciągliwość. W większości przypadków wydłużenie przy zerwaniu przekroczyło 1000%. W trakcie badania odkształconych próbek stwierdzono, że podczas jednoosiowego rozciągania zachodziło oddzielanie się ziaren napełniaczy od matrycy polipropylenowej

Flow-induced crystallization

Molecular properties are reflected in the rheological and crystallization behavior. The first task is to design and use some well‐defined experiments that reveal all these features. Second, the experimental findings should be translated into mathematically formulated physical models, suited to be implemented in numerical codes for simulation of polymer shaping processes. Third, this modeling should be validated for a range of conditions including processing conditions. This chapter focuses on these three aspects and addresses general questions: How do the different structures observed relate to the flow conditions: deformation rates, stress, pressure, thermal conditions, material parameters, additives, and so on? and How can one model this on a continuum level so it is applicable in numerical codes for process simulation? The chapter also focuses on the effect of flow on crystallization of polymer melts