Remon Pop-Iliev

A Novel System Design for Continuous Processing of Plastic/Wood-Fiber Composite Foams with Improved Cell Morphology

It is believed that the moisture that is inherently present in nondried wood-fibers adversely affects the cell morphology of plastic/wood-fiber composite foams processed in extrusion. Based on this hypothesis, achieving a continuous extrusion-based production of fine-celled plastic/wood-fiber composite foams witha desirable quality would be strongly conditioned by the efficiency of the system designed for uninterrupted wood-fiber moisture elimination. This paper presents an innovative approachin addressing this problem by implementing the well-known cascade devolatilizing system in a chemical blowing agent (CBA) based production of plastic/wood-fiber composite foams. It comprises a moisture-evaporation tandem extrusion system equipped witha vent at the interconnection of the two extruders to serve for purging the moisture in the atmosphere. In order to check the performance of the newly developed system, an experimental study has been carried out for comparing the cell morphology and the volume expansion ratios of the foams obtained by processing identically formulated foamable plastic/wood-fiber composite mixtures using simultaneously the cascade devolatilizing tandem extrusion system and a corresponding single extruder withno vent. The experimental results revealed that the foams produced by using the cascade devolatilizing tandem system exhibited significantly improved cell morphologies and surface quality.

Fundamental study of CBA-blown bubble growth and collapse under atmospheric pressure

This article focuses on gaining a fundamental understanding of the bubble growth and collapse phenomena in a chemical blowing agent (CBA)based foaming process under atmospheric pressure. The behavior of CBA-blown bubbles exposed to various processing conditions is observed using a hot-stage optical microscope-based image processing system. A mathematical model that accounts for the effects of diffusion, surface tension, viscosity, and elasticity has been employed. It has been found that the processing temperature, diffusivity, and gas bulk concentration have dominant effects on the life span of CBA-blown bubbles.

Manufacturability of Fine-Celled Cellular Structures in Rotational Foam Molding

Any closed-cell polyolefin foam production tends to achieve the highest possible cell size distribution uniformity, cell size reduction, and cell density augmentation. However, the control of the cell size of rotationally foam-molded cellular structures formed on the base of a chemical blowing agent (CBA) might be often aggravated by some inherent limitations that are unique to the rotational molding process, which results in coarser-celled final cellular structures. Although a fine-celled morphology (cell size<100 [mm] and cell density > 106 [cells/cm3]) in rotationally molded foams has been closely approached, it has not been actually achieved yet, nor has it been ever clarified whether it is actually achievable in rotational foam molding or not. This study attempts to provide an answer to this fundamental question by focusing on the understanding of the mechanisms governing the formation, growth, shrinkage, and collapse of CBA-blown bubbles in nonpressurized polymer melts originating from extrusion melt compounded foamable resins in a pellet form.

Melt Compounding Based Rotational Foam Molding Technology for Manufacture of Polypropylene Foams

This paper is intended to provide an engineering understanding of the technological potentials for processing polypropylene (PP) foams in rotational foam molding. A process proposal, based on the melt compounding material-preparation approach, capable of producing completely foamed, single-layer, single-piece PP products in rotational foam molding, is disclosed in detail. It comprises dispersing a chemical blowing agent (CBA) in the PP matrix using a twin-screw compounder, pelletizing the obtained expandable composition, and then producing foams in an uninterrupted rotational foam molding cycle by using the pre-compounded foamable pellets. Several PP grades were deliberately selected to cover a wide range of melt flow rates (MFR), starting from 5.5 up to 35 dg/min. After the raw materials participating in the study were characterized using thermal analysis instrumentation, different foamable compositions were formulated in order to prepare both 3-fold and 6-fold foamable pellets from each PP grade. The optimal foam processing strategies were identified via a systematic experimental parametric search. Foams with the best cell morphologies were obtained out of the high melt strength PP grades. In addition, the experimental results revealed that the cell morphology of the processed PP foams is not as good as that of respective PE foams. However, the cell morphologies of the PP foams processed by using the melt compounding-based approach demonstrated significant improvements in comparison with those processed by using the dry blending-based approach.

Piezoelectric power generation for sensor applications: design of a battery-less wireless tire pressure sensor

An in-wheel wireless and battery-less piezo-powered tire pressure sensor is developed. Where conventional battery powered Tire Pressure Monitoring Systems (TPMS) are marred by the limited battery life, TPMS based on power harvesting modules provide virtually unlimited sensor life. Furthermore, the elimination of a permanent energy reservoir simplifies the overall sensor design through the exclusion of extra circuitry required to sense vehicle motion and conserve precious battery capacity during vehicle idling periods. In this paper, two design solutions are presented, 1) with very low cost highly flexible piezoceramic (PZT) bender elements bonded directly to the tire to generate power required to run the sensor and, 2) a novel rim mounted PZT harvesting unit that can be used to power pressure sensors incorporated into the valve stem requiring minimal change to the presently used sensors. While both the designs eliminate the use of environmentally unfriendly battery from the TPMS design, they offer advantages of being very low cost, service free and easily replaceable during tire repair and replacement.

Pneumatic tire-based piezoelectric power generation

Plug-in Hybrid Electric Vehicles (PHEVs) and Extended Range Electric Vehicles (EREVs) currently mainly rely on Internal Combustion Engines (ICE) utilizing conventional fuels to recharge batteries in order to extend their range. Even though Piezo-based power generation devices have surfaced in recent years harvesting vibration energy, their output has only been sufficient to power up sensors and other such smaller devices. The permanent need for a cleaner power generation technique still remains. This paper investigates the possibility of using piezoceramics for power generation within the vehicles wheel assembly by exploiting the rotational motion of the wheel and the continuously variable contact point between the pneumatic tire and the road.

Manufacture of Integral Skin PP Foam Composites in Rotational Molding

The feasibility of applying the single-charge rotational foam molding processing principle to the fabrication of integral skin polypropylene (PP) foams comprising a PP solid skin and a PP foamed core is investigated in this study. A systematic process interruption and sample evaluation approach was used to quantify the experimental results and explore possibilities for improving the process control strategies to ultimately achieve a desired homogeneity and thickness uniformity of the solid PP skin layer that would be fully encapsulating the PP foamed core of a desired cell population density and average cell size. The experimental results revealed that this is quite a challenging task, not only because of the well-known intrinsically poor foaming nature of PP due to its low melt strength at elevated temperatures, but also because, in single-charge rotational molding, the processing parameters are often conflicting with each other and therefore, have to be optimized within a very narrow processing window. However, simultaneous, single-charge, quality PP integral skin and foamed PP core formation in rotational foam molding is feasible. Optimizing the heating profile, heating rate, heating time, and the mold rotational speed as well as careful selection of PP resins (or resin blends), chemical blowing agents (CBA), and their composition formulations is strongly recommended.

Single-Step Rotational Foam Molding of Skin-Surrounded Polyethylene Foams:

This paper demonstrates howthe rotational foam molding process can be employed for the manufacture of plastic articles that have a distinct layer of nonfoamed skin surrounding a foamed core or layer. It is focused on the singlestep processing principle, the main feature of which is the simultaneous introduction of both the foamable and nonfoamable resin into the cavity of the mold at the beginning of the cycle. Although this advanced concept eliminates the need for process interruptions and the use of drop boxes or plastic bags, it requires an appropriate processing strategy that would assure that the execution of the adhesion of the nonfoamable thermoplastic resin to the internal surface of the mold always takes place prior to the activation of the foamable resin.

Development of a DSM-Based Methodology in an Academic Setting

This paper proposes the use of a design structure matrix/work transformation matrix (DSM/WTM)-based methodology in academic settings to serve engineering educators as a facilitating tool for predetermining the difficulty and feasibility of design engineering projects they assign, given both the time constraints of the academic term and the expected skill level of the respective learners. By using a third-year engineering design project as a case study, engineering students actively participated in this comprehensive use of DSM methodologies. The engineering design process has been thoroughly analyzed to determine convergence characteristics based on the eigenvalues of the system followed by a sensitivity analysis on the originally determined DSM based on data provided by students in terms of task durations and number of iterations for each task. Finally, an investigation of the design process convergence due to unexpected events or random disturbances has been conducted. The obtained predictive model of the design process was compared to the actual dynamics of the project as experienced by the students and the effect of random disturbances at any point in the design process has thereby been evaluated. [DOI: 10.1115/1.4005591]

Implementation and Effect of Rubrics in Capstone Design Courses

This paper demonstrates the implementation of a two-dimensional rubric system into capstone-level design courses as the preferred method for assigning and evaluating students’ design work. The rubric is based on the ICE (Ideas, Connections, and Extensions) learning and application levels, having been expanded from the basic one-dimensional rubric into two dimensions to further resolve each rank (level of application) into skill levels of learning of a given concept (i.e., a design project element), with qualitative descriptors summarizing the requirements for each skill level versus rank coordinate in the rubric that an element is applied to justify the assigned grade. These rubrics provide guidance to students in how to address the design requirements for maximum possible marks and also assist instructors with clearly defining the design requirements. The developed rubrics are applicable to other upper year undergraduate and graduate level courses featuring a major design project with minor modifications. Their usefulness was evident in the observed improvement of students’ grades over the last three years. For capstone courses, a multi-dimensional rubric is more versatile, providing instructors with a greater choice of assigning grade levels to evaluate student performance for a given element of the design project.Copyright