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Conference Proceedings

Elimination of Copolymer in Polyvinyl Chloride Plastisols Using High-Solvating Dibenzoate Plasticizers
Deirdre Newton, William D. Arendt, Emily L. McBride, May 2017

High-solvating dibenzoate plasticizers are already known for their ability to reduce gelation and fusion temperatures relative to formulas with general purpose plasticizers.[1] In this evaluation, plastisols were prepared to compare different PVC resins, homopolymer versus copolymer, as well as different plasticizers, general purpose versus high solvators. Viscosity aging was evaluated at room temperature and 40 °C to determine the storage stability of each formulation. Fusion characteristics and mechanical properties were compared by gel/fusion and different processing temperatures. This data was used to demonstrate that high-solvating dibenzoate plasticizers can successfully be used to reduce fusion temperature and increase storage stability, which enables formulators to replace copolymer with homopolymer while retaining processability, improving certain mechanical properties, and reducing cost.

Surface Treatment of Carbon Fiber by Anodic Oxidation and Improvement of ILSS in CFRP
Hiroyuki Nishimura, Hirofumi Kyutoku, Masaaki Yoshikawa, Yoshikazu Kondo, Kazushi Yamada, May 2017

Carbon fiber has many superior properties such as a higher strength, a higher elastic modulus, a higher heat resistance, a lower specific gravity compared with conventional organic materials, metals or ceramics. On the other hands, its inactive surface due to high graphitization is disadvantageous for the high-performance composite materials in the advanced material fields. In this study, the fundamental producing conditions and estimations on the obtained carbon fibers were studied. The surface modifications of carbon fibers were achieved by the anodic oxidation to improve the interfacial adhesive strength which resultantly caused the stronger interlaminar shear strength (ILSS). The conditions of anodic oxidations (ex. loaded current) were studied for getting the maximum modification effect. The mechanical properties of obtained carbon fibers were estimated with the universal testing machine. The surface characteristics of carbon fibers were observed with the Scanning Electron Micrograph (SEM). The introduction of oxygen (=O/C ratio) on carbon fibers by the anodic oxidation were estimated with the x-ray photo-electron spectroscopy (XPS). The comprehensive effects of these treatments were evaluated by the changes in ILSS. We tried to find out the optimum condition through the studies of the relationship between our own carbon fibers and AO conditions. Resultantly, we found out that the very little AO not larger than 0.02(A/2k) is sufficient to improve the ILSS of obtained composites.

Wide-Range of Microcellular Bead Foams from Different PLA-based Drop/Sea Blend Morphologies
Mohammadreza Nofar, A. Tabatabaei, C.B. Park, P.J. Carreau, M-C. Heuzey, M.R. Kamal, May 2017

In this study, the blends with weight ratio of 75/25 (w/w) were prepared where amorphous polylactide (PLA) was the matrix and poly[(butylene adipate)-coterephthalate] (PBAT) or poly[(butylene succinate)-coadipate] (PBSA) were the minor phases. Various blend morphologies could be obtained by using different molecular weight PLAs as well as different processing techniques (i.e., internal mixer and twin-screw extruder). Different microcellular bead foam structures ranging from low-density open-cell to high-density closed-cell could be manufactured not only via using blends with different droplet morphologies but also by using different minor phase solid inclusions with different rigidities originated from their different crystallization behavior.

Enhancement of the Conductor Track Quality of Electrically Conductive Plastics Parts by Means of Targeted Process Control with the Integrated Metal/Plastics Injection Molding
Philipp Ochotta, Christian Hopmann, May 2017

In the Integrated metal/plastics injection molding (IMKS), metallic tracks are injected into a plastics carrier by means of die-casting in an integrated process. IKV investigated the influence of process management on the quality and durability of these electrically conductor plastic components. The focus of this work lies in the analysis of the metal melt, its flowing behavior and the interaction with the plastics carrier. The results show that the components produced in IMKS have a long service life with respect to electrical loads.

Testing and Modeling Anisotropic Failure of Polymeric SLS Materials and Structures
Mark Oliver, Zhenyu Xue, Bachir Abeid, Stuart Brown, May 2017

Understanding the mechanical failure of additively manufactured (AM) polymers is becoming more important as engineers increasingly fabricate end-use parts. Knowing how the mechanical limits of a given AM polymer depend upon material orientation is a critical aspect of maximizing mechanical performance. We have characterized the tensile failure of an SLS polyamide 12 in detail using tensile test specimens and subsequently examined how the anisotropy of the material impacts the failure of a lattice structure loaded in three-point bending. Additionally, an anisotropic material model is presented that we have used to simulate the deformation of the lattice structure using finite element analysis.

Stabilized & Optically Tailored Plasmonic Nanocomposite Preparation Using Laboratory Scale Extrusion
Joshua A. Orlicki, Devon A. Boyne, Alice M. Savage, Mark H. Griep, Frederick L. Beyer, May 2017

One of the chief impediments to the wider adoption of nanocomposites is the challenge of maintaining nanoscale features while employing bulk preparative techniques. Nanoparticle fillers may tend to aggregate or become destabilized during processing at temperatures required to process engineering thermoplastics. We report a study where nanoparticles of varying aspect ratios were stabilized with robust shells and then compounded using a laboratory scale extruder. Optical plaques were produced via injection molding, and the resultant nanocomposites were assessed for their optical and morphological properties.

Effects of Small Range Color (Pigment) Concentration Levels in Combination with Gamma Sterilization on Plastic Injection Molded Parts
Trivikrama Bhanoji Pala, I. Joga Rao, May 2017

Color (pigment) concentration levels play a significant role in changing the mechanical properties of an injection molded part. Higher concentration levels could result in functional failure of the parts [1]. A general rule of thumb, concentration levels between 3 - 5% or 5 - 10% are being used across different industries to achieve the required color. The above concentration levels are considered as small range concentration levels in this manuscript. Effects of sterilization (radiation) plays an important role on the plastic injection molded parts. The combination of gamma radiation sterilization and color concentration is very useful to the medical devices and food processing Industry. An experimental study is conducted to find out the effects of both small range color concentration and gamma radiation sterilization on the mechanical properties such as tensile strength, strain at yield and break on the Injection molded parts. In this study, Injection molded specimen made up of PP (polypropylene) and Acrylonitrile Butadiene Styrene (ABS) which are exposed to gamma sterilization of 25 kGy (kilo gray) dose are considered as it common normal dose used for plastics [8]. Depending upon the specific polymer and additives involved. There is no impact on tensile strength, while the strain at yield and at break shown an considerable decreasing trend with increase in the percentage of pigments in case of PP(polypropylene). There is no trending observed in case of ABS resin. Outcomes may influence performance and should be evaluated in advance by functional testing. Hence product designers may need to assess the impact of these small pigment concentration levels in combination with the sterilization effect with respect to the base resin and need to specify the acceptable pigment concentration levels in combination with sterilization in their product drawings or in product specification documents.

Creep Failure Analysis and Shelf Life Determination (Prevention) of Injection Molded Parts with and with out Gamma Irradiation
Trivikrama Bhanoji Pala, I. Joga Rao, May 2017

Creep is the inelastic response of materials exposed to constant load at a particular temperature. Creep characteristics play an important role in the design consideration of injection molded plastic parts where they can provide enable one to measure or estimate the creep strain when there are mating parts. However this does not consist of the information necessary to determine or calculate the outcome of creep failure of the mating parts under a constant load up to the end of the shelf life of the product. If the designer can understand the limits of creep failure in the plastic engineering part design then it aids in the determination of shelf life of the product. Also, the plastic parts which are predominantly used in the medical device industry, are exposed to sterilization prior to use. A common radiation dose used for plastics is in the range 15–25 kGy [8]. Therefore the objective of this study was to understand the creep failure of parts with or without gamma sterilization and help enable the designer to determine the shelf-life of the plastic components when they are exposed to gamma sterilization. Finite Element Analysis (FEA) was utilized to determine the impact of creep on the two mating PP (polypropylene) injection molded parts. The inputs needed for the FEA model, which are the temperature dependent coefficients (A, m and n) were determined by curve fitting the creep test results for PP with a time hardening formulation of power law creep model for the strain vs time data at 23°C, 40°C and 60°C with and without gamma sterilization . It is found that the Creep strain at given total time showed a decreasing trend [2]. The FEA model contains two PP resins namely a bearing and sleeve having a mating interference fit. Sleeve is inserted into the bearing and this insertion force is termed as attachment force and later the sleeve is pushed out from bearing and this force is termed as detachment force. In FEA model, in order to find creep strain produced between both mating parts, the Sleeve is retained in bearing for intended self-life duration. The detachment force of sleeve before and after shelf life for unexposed parts and 25kGy gamma exposed PP resins parts were calculated. The results shows that the detachment force reduces after aging, regardless of gamma exposure. These results assist the product designer to estimate the reduction in detachment force due to creep strain between the mating parts. It is also found that material and geometry are important to consider, so that the failure due to the creep can be avoided early in the design process and it is very critical to consider creep in order to ensure product performance. Therefore the results of this study can help one determine the required shelf life of the product by considering the creep failure in the successful design of the plastic Injection molding parts.

New Metrics for Evaluation of Network Defects in Glassy Thermosets
Madhura S. Pawar, Alan J. Lesser, Irene Gorman, May 2017

Previous work on rubber toughening by incorporating reactive functional modifiers into epoxy formulations show that they phase separate into rubbery domains necessary for effective increases in fracture toughness both in the neat resin as well as carbon fiber reinforced composites. However, their relative reactivity with respect to the epoxy or the amine used in the system can lead to imbalance in stoichiometry and disruption of the network structure. Also, due to their different solubility in different resins and hardeners, they can act as plasticizers instead of phase separating into necessary rubbery domains which can be seen from the decrease in Tg of these formulations. This work aims to investigate the detrimental effects of impact modification on network structure by measuring thermal and non-linear mechanical properties of the network using non-standard compression testing. Compression tests were done on impact modifier free diglycidyl ether bisphenol A (DGEBA) crosslinked with diaminodiphenylmethane (DDM) with varying stoichiometric ratios of excess amine or epoxy groups in the network. For the amine-rich networks, yield stress and modulus is not affected significantly as the network is a completely intact loosely crosslinked network however the strain hardening modulus decreases systematically as the network goes further out of stoichiometry. In contrast, the results of the epoxy rich networks show complex trends with increasing yield stress and modulus as we go further out of stoichiometry. This is due to the densification of the network due to parts of the epoxy network filling in the free volume giving rise to a fragmented network and a mechanically fragile glass as excess epoxy groups are added to the system. The strain hardening modulus of the epoxy rich networks show a steeper decrease than those of amine excess networks. Compression testing on DGEBA-DDM formulations with impact modifiers can be used to and calculate network connectivity and effectively distinguish between effects of plasticization and network disruption due to stoichiometric imbalance for glassy thermosets.

Application of Taguchi Method on Weldline Tensile Strength of Long Glass Fiber Reinforced Nylon66 Molded Parts
Hsin-Shu Peng, Po-Wei Huang, Chao-Tsai Huang, May 2017

Nylon66 composites (PA66 with 40wt% long glass fiber) were used as molding material for injection molded part (tensile specimen with thickness of 1.8mm and 2.5mm). The Taguchi method with L18 orthogonal array was used to determine important factors affecting weldline tensile strength in long glass fiber reinforced Nylon66 molded parts. It was found that the significant contributing factors in the descending order were melt temperature (38.70%), part thickness (28.66%), mold temperature (14.40%), screw speed (10.44%) and filling time (4.27%); moreover, lower melt temperature, part thickness of 1.8 mm, higher mold temperature, higher screw speed and longer filling time would increase the weldline tensile strength for long glass fiber reinforced Nylon66 molded parts with vent design.

Dielectric Permittivity of Thermoplastic Polyurethane/PZT Composite Foams
Gayaneh Petrossian, A. Ameli, May 2017

The touch sensitivity of piezoelectric-based sensors is inversely proportional to their dielectric permittivity. Introducing a cellular structure into these sensors can decrease the permittivity while enhancing their mechanical flexibility. In this work, various cellular thermoplastic polyurethane (TPU)/lead zirconate titanate (PZT) composites having several PZT contents were fabricated using physical foaming, and their dielectric properties and microstructure were studied. Composite foams with PZT contents of 2.5-10vol.%, relative densities of 0.2-1, and void fractions of 50-75vol.% were obtained, providing a platform to assess the evolution of relative permittivity with the foaming degree. The relative permittivity continuously decreased in both the neat TPU and TPU/PZT composites, up to a maximum of 4 times, as the volume expansion increased. At higher expansion ratios, the relative permittivity of the composites appeared to be independent of the PZT loading, due to the volumetric dominance of the low-dielectric air phase. The experimental relative permittivity measurements also showed good agreement with the predictions made by the Yamada model, extended to ternary system of piezoceramic polymer composite foams. Voltage sensitive foams can have applications in aerospace, robotics, and flexible electronics.

Time-Dependent Delamination of Plastic Film: Observation and Modeling
Hoang Pham, Haiying Zhang, Zhenwen Zhou, Alexander Chudnovsky, May 2017

The paper is aimed at the observation and modeling of thin plastic film delamination from a substrate and its progression. The authors are addressing the following issues: 1) what physical and geometrical parameters of the film-adhesive-substrate system play the major role in initiation and progression of delamination; 2) what is the root cause of slow delamination growth in time; and 3) formulation of a quantitative model of the process. A brief review of existing approaches, simple experimental setup, observations and the modeling results are reported.

Rheological Characterization of Medical Thermoplastic Polyurethanes
Ian Pierson, Emily Chen, Ajay D. Padsalgikar, May 2017

The use of thermoplastic polyurethanes (TPUs) in the medical device industry is widespread due to the unique combination of biological properties, abrasion resistance, and processability that they provide. Phase separation at the microscopic level within the morphology of TPUs results in the presence of hard and soft polymer block segments, creating these desirable characteristics. However, the microphase separation also complicates the understanding of TPU structural properties, particularly their flow properties, and creates difficulties during melt processing. Properties of several TPUs were characterized with a novel rheological method to quantify the effects of time dependence and are reported in this study.

Knowledge-Based, Iterative Approach for an Automatic Cavity Balancing for Injection Molding
Alexander Porsch, Johannes Wortberg, René Andrae, Peter Köhler, May 2017

Today, most CAD systems have integrated simulation features. These accelerate the development of injection-molded parts because of tight connection of the CAD and CAE system. Knowledge-based design and analysis features are as well implemented as tools for the determination of the gate position. The drawbacks of these solutions are the limited access to the calculation methods and the possibility for modifications or extensions. Therefore, a knowledge-based approach for an automatic flow balancing was developed. By local decreases or increases of the nominal wall thickness the filling of the cavity is improved. The positions and sizes of these geometry changes are determined iteratively during an optimization routine, which is presented in this paper. Finally, the approach is verified in a case study.

Mechanical, Thermal and Electrical Property Enhancement of Graphene-Polymer Nanocomposites
Jacques Poulin, Helen Lentzakis, Nima Moghimian, Sajjad Saeidlou, Naiheng Song, Tatiana Kaydanova, Éric David, May 2017

In this work, NanoXplore’s proprietary graphene nanoplatelets, heXo-G V20, are melt-extruded into thermoplastics LLDPE, HDPE and TPU. Graphene is shown to effectively increase the stiffness and the strength of a matrix TPU. The flexural and tensile moduli increase with loading levels of graphene whereas the tensile strength increases at low loading levels, but does not further increase at higher graphene concentrations. A ten fold increase in thermal conductivity was achieved by adding heXo-G V20 graphene to LLDPE matrix. The thermal conductivity percolation threshold was reached at 10% loading. At 1% loading of graphene the onset of the decomposition temperature and maximum weight loss temperatures were shifted by about 50°C, significantly improving the thermal stability of the PE matrix. Fourteen orders of magnitude increase in electrical conductivity of HDPE was obtained at 30% loading of graphene. Excellent EMI shielding of 40 dB was achieved with 20 wt% addition of graphene in a TPU matrix.

Polymer Modifications in Asphalt Roofing
Qian Qin, Denis Tibah, Logan Wilks, Zhanping You, May 2017

Polymers have been widely used in asphalt roofing industries in order to reduce premature failure and improve final performance such as cracking and impact resistance, which is difficult to be achieved by asphalts alone. This work focuses on styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene/butylenestyrene copolymer (SEBS), and Elvaloy modifications on asphalt roof coatings. The thermal susceptibility, low temperature cracking propensity were investigated and compared with unmodified version to present the advantages and challenges of polymer modifications. From the perspective of manufactures, the possibility to double stack roof pallets were estimated based on blocking resistance evaluation via an axial rheological method.

Orienting Melt to Produce on Lab-Microscale High Performance and Ultra Thin Foils
Martin Quaedflieg, Han E.H. Meijer, Lou Nijsten, May 2017

Efficient molecular orientation of polymers in the melt- or solution state requires concentric contraction flows, which result in single or multi-filament fiber shaped products. Directed molecular orientation in pipes, sheets, foils and films, like strip bi-axially, planar or tri-axial, are difficult to achieve and require complex multi-stage processing often supported by the addition of extra external magnetic, electric, or temperature gradient fields that put constraints to the materials to be processed. Here we aim at a simple continuous process to produce uni-axially oriented foils, by designing a special die in a standard miniaturized laboratory scale film casting process. The internal of the die consist of a fiber forming, and a fiber fusing part. The specific design of the fiber forming part allows the combination of the fibers formed, without them crossing, into a line that forms a sheet. Flow in the total volume around the slit ends up in molecularly oriented flow inside the slit. To preserve orientation, an air gap extrusion process follows the exiting slit flow, to allow for a strong draw down under high melt stress. Small air-gaps and a cold cooling nose, combined with a supporting carrying film, make the total process easy, clean and cheap, and the products unique. We will demonstrate that, mounted on the miniature Xplore MC 15 lab compounder, the device is able to produce not only high performance fully oriented foils based on a thermotropic liquid crystalline polyester (Vectra), but also extremely thin foils of polyamides and polyesters. In the last application, the melt orientation is used only to temporary obtain a high melt strength that allows a high draw-ability in the air gap.

Environmentally Benign Processing of Poly(2,6-Dimethyl-1,4-Phenylene Oxide) (PPO) with Superheated Liquids
Md Arifur Rahman, Matthew Lok, Alan J. Lesser, May 2017

the expanding industry of polymer processing, a prominent area of current research is to process polymers efficiently without creating any environmental hazards. Processing of intractable polymers like PPO requires high processing temperature and toxic plasticizers. Very few research works have reported the use of superheated liquids to process intractable polymers. This research work presents a systematic study to explore the advantages of processing PPO with superheated liquids composed of ethanol and water. Microcellular foams of PPO having a density range from 0.13 to 0.56 g/cm3 can be produced with the aid of superheated ethanol, water and ethanol/water mixtures. Such foams also exhibit high specific strength. In addition, PPO can also be extruded with superheated ethanol or ethanol/water mixtures at a temperature which is 150 to 180 °C below the conventional extrusion temperature for PPO.

Failure Analysis and Product Improvement of Medical Device Tubing
James D. Rancourt, Jason G. Todd, Jennifer E. Brooks, May 2017

Manufactured products are expected to serve their useful lifetime without premature failure. When premature failure does occur, it is important to determine the root cause. This is particularly important in high-consequence applications such as medical products. In this case study, the analysis of polyurethane tubing that became yellowed and cracked is presented. The mode of failure was determined using multiple analytical methods, the hypothesis was tested, and additional analyses were performed to confirm the root cause hypothesis. In addition, a modification to the composition of the medical tubing was suggested and implemented. The efficacy of the modified composition was assessed, similar to the failure analysis protocol, using microscopy, spectroscopy, and chromatographic methods. The results of this failure analysis and product improvement project will be presented.

Fabrication of High Strength and Toughened Biodegradable Electrospun Fibers: Poly(Lactic Acid)/Biomax Blends
Sheikh Rasel, Remon Pop-Iliev, Ghaus Rizvi, May 2017

The objective of this study is to prepare a toughened and strengthened electrospun fibrous biodegradable poly(lactic acid) (PLA) mat blended with Biomax, an ethylene copolymer designed to modify PLA to improve toughness properties, using electrospinning. Morphological, thermal, mechanical, and thermomechanical properties of PLA/Biomax blends were investigated. Morphological findings indicated that the electrospun PLA/Biomax fibers were uniform and smooth with an average diameter of 1.4-1.5 µm when Biomax contents below 2 % (w/v). The addition of 1 % of Biomax improved both thermal stability and mechanical properties of PLA/Biomax fibrous mats. PLA/Biomax mats with 1 % (w/v) of Biomax exhibited the maximum tensile strength of 4.6 MPa and tensile modulus of 103 MPa showing 64.3 % and 101 % improvement; as compared to neat PLA values of 2.83 MPa and 51 MPa, respectively. Furthermore, the presence of 1 % Biomax into electrospun PLA fiber mats improved the storage modulus by 107.5 % compared to PLA fiber mat (41.5 MPa). Strong and toughened PLA/Biomax biodegradable fibrous mat might be potentially suitable to be used in packaging, filtration, reinforcement of composite, etc.

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