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There are multiple factors that contribute to the warpage problems where molten part is distorted during solidification in rotational molding. A novel warpage simulation model is developed accounting for the effect of various process parameters like crystallinity change, temperature-dependent polymer properties, and cooling rate. The polymer material properties were readily not available; they were constructed from literature data with adaptation to the process condition and their significance on simulation results is discussed in detail. A systematic detailed simulation analysis of warpage in box part was done and results were compared with experimental values published in literature. The warpage magnitude under seven different cooling methods are presented. It was found that externally water cooled parts exhibited maximum warpage which is also corroborated by literature data while the parts cooled by water on either sides of the part show reduction in warpage. The warpage simulation results show an agreement with deviation ranging from 1.2% to 69% with experimental values. Highlights * A novel thermal expansion coefficient approach was adopted for the first time to develop warpage simulation of rotationally moulded parts. * Inclusion of temperature-dependent thermo-mechanical properties of polymer in the simulation model. * The cooling rate is directly proportional to the warpage in the parts. * Validating warpage simulation results for seven different cooling methods with experimental measurements. * Maximum warpage is seen where the highest temperature difference exists between part and mould. KEYWORDS process parameters, rotational molding, shrinkage, simulation, warpage, 1 | INTRODUCTION Control and prediction of warpage problem in rotational molding (1) of polymer parts is long overdue. All thermoplastic processing methods inevitably include heating the polymer to the [...]

RationaleThe etiology of schistosomiasis-associated pulmonary arterial hypertension (PAH), a major cause of PAH worldwide, is poorly understood. Schistosoma mansoni exposure results in prototypical type-2 inflammation. Furthermore, transforming growth factor (TGF)-β signaling is required for experimental pulmonary hypertension (PH) caused by Schistosoma exposure.ObjectivesWe hypothesized type-2 inflammation driven by IL-4 and IL-13 is necessary for Schistosoma-induced TGF-β-dependent vascular remodeling.MethodsWild-type, IL-4(-/-), IL-13(-/-), and IL-4(-/-)IL-13(-/-) mice (C57BL6/J background) were intraperitoneally sensitized and intravenously challenged with S. mansoni eggs to induce experimental PH. Right ventricular catheterization was then performed, followed by quantitative analysis of the lung tissue. Lung tissue from patients with schistosomiasis-associated and connective tissue disease-associated PAH was also systematically analyzed.Measurements and main resultsMice with experimental Schistosoma-induced PH had evidence of increased IL-4 and IL-13 signaling. IL-4(-/-)IL-13(-/-) mice, but not single knockout IL-4(-/-) or IL-13(-/-) mice, were protected from Schistosoma-induced PH, with decreased right ventricular pressures, pulmonary vascular remodeling, and right ventricular hypertrophy. IL-4(-/-)IL-13(-/-) mice had less pulmonary vascular phospho-signal transducer and activator of transcription 6 (STAT6) and phospho-Smad2/3 activity, potentially caused by decreased TGF-β activation by macrophages. In vivo treatment with a STAT6 inhibitor and IL-4(-/-)IL-13(-/-) bone marrow transplantation also protected against Schistosoma-PH. Lung tissue from patients with schistosomiasis-associated and connective tissue disease-associated PAH had evidence of type-2 inflammation.ConclusionsCombined IL-4 and IL-13 deficiency is required for protection against TGF-β-induced pulmonary vascular disease after Schistosoma exposure, and targeted inhibition of this pathway is a potential novel therapeutic approach for patients with schistosomiasis-associated PAH.

Purpose/aimAngiogenesis is a central component of normal wound healing but it has not been fully characterized in lung repair following acute inflammatory injury. The current literature lacks vital information pertaining to the extent, timing, and location of this process. This information is necessary for examining mechanisms that drive normal lung repair in resolving acute inflammatory injury. The goal of our study was to formally characterize lung angiogenesis over a time course of bleomycin-induced lung injury.Materials and methodsFemale C57BL/6 mice age 8-12 weeks were treated with a single dose of intratracheal bleomycin. Total lung endothelial cells were quantified with flow cytometry 0, 7, 14, 21, and 28 days following bleomycin administration, and endothelial cell replication was assessed using bromodeoxyuridine (BrdU) incorporation.ResultsEndothelial cell replication was maximal 14 days after bleomycin administration, while total lung endothelial cells peaked at day 21. Tissue analysis with stereology was performed to measure total lung vascular surface area in bleomycin at day 21 relative to controls and demonstrated a trend toward increased vasculature in the bleomycin group.ConclusionsAngiogenesis begins shortly after injury in the bleomycin model and leads to an expansion in the lung endothelial cell population that peaks at day 21. This study offers the first longitudinal examination of angiogenesis following acute inflammatory lung injury induced by bleomycin. Information provided in this study will be vital for further investigating mechanisms of angiogenesis in both normal and abnormal lung repair.

The changing nature of doctoral education over the past three decades has taken on a triadic relationship constructed around expectations-process-purposes and has generated much commentary and critique. The intention of this paper is to focus on the notion of "purpose" from the perspective of doctoral supervisors which we have collated into four themes labelled "knowledge generation," "recognition," "positionality" and "instrumentalism". The themes were generated via the analysis of semi-structured interviews undertaken with 50 doctoral supervisors as part of the SuperProfDoc project investigating their practice.

The evolution of foam in unpressurized melt processing techniques, such as rotational molding, is different from high‐pressure processes like injection foam molding, making comparisons difficult. This has driven the need for a dedicated technique for studying these systems. A unique test procedure was developed to capture and characterize foam evolution in test tubes under unpressurized conditions. A validation study found the procedure to be reliable, producing repeatable samples (height average (AVG) 39.69 ± 1.70 mm and density AVG 0.319 ± 0.012 g/cm3) and delivering comparable results to samples produced using the industrial rotational foam molding process. A study examined the effect of polymer particle size on the foam structures produced. Finer (>90 μm <106 μm) polymer powders produced more desirable structures, achieving 38.6% lower foam density and 43.8% taller peak foam height than coarser powders (>425 μm < 500 μm). Cycle times were much shorter (~15 min) in comparison with the industrial rotational molding process (>40 min) and required smaller amounts of materials, making it useful for rapid characterization. Future work is planned to apply the new procedure to investigate the effects of material and processing conditions on the foam structures produced under unpressurized conditions. Highlights: Evaluation of existing unpressurized foam characterization methods.Rapid test procedure developed to characterize unpressurized foam evolution.Variability study of foam structures produced using the new procedure.Effect of rotational molding polymer powder and considerations for foaming.Results validated with industrial unpressurized rotationally molded samples. [ABSTRACT FROM AUTHOR]

The article is focused on analysis of global efficiency of new mold for rotational molding of plastic parts, being directly heated by thermal fluid. The overall efficiency is based on several items such as reduction of cycle time, better uniformity of heating-cooling and low energy consumption. The new tool takes advantage of additive fabrication and electroforming for making the optimal manifold and cavity shell of the mold. Experimental test of a prototype mold was carried out on an experimental rotational molding machine, developed for this purpose, measuring wall temperature, and internal air temperature, with and without plastic material inside. Results were compared with conventional mold heated into an oven and to theoretical simulations done by Computational Fluid Dynamic software (CFD). The analysis represents considerable improvement of cycle time related to conventional methods (heated by oven) and better thermal uniformity to conventional procedures by direct heating of oil with external channels. In addition to thermal analysis an energetic efficiency study was done. POLYM. ENG. SCI., 52:1998-2005, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Rotational molding is a low pressure, high temperature, molding process that uses heat and biaxial rotation to produce hollow, one piece plastic parts. It's used to produce small and [...]