The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Dual-Mode Viscoelasticity For Polymer Melts
Polymer melts containing entangled chains of high molecular weight and high polydispersity typically show a distinct power-law relaxation region prior to a terminal relaxation region. It is difficult to describe this multiplex property using the generalized Maxwell model unless a large number of fitting modes are used. In this paper, we propose to establish relaxation models directly in the Laplace transformed s-domain, by defining constraints or admissibility conditions for acceptable transfer functions for modeling the multiplex entanglement effect. This leads to a single-mode relaxation modulus with only four model fitting parameters. In combination with a normal Rouse relaxation mode to describe initial short-range structural relaxation, the resultant two-mode relaxation model is found to fit realistic linear viscoelastic material functions and holds a promise for modeling nonlinear deformation of polymer melts.
Recycling Of Polyethylene Grocery Bags Into High-Strength Fibers And Yarns Without Using Melt Processing
A critical issue facing man kind is how to effectively recycle plastic grocery bags. Currently, the most proven practice for bag recycling is to create numerous returning sites throughout the nation. However, the success is compromised by the voluntary nature of such activities. In this work, we investigate an alternative approach to bag returning, by diverting recycling activities directly to consumers or end users at home. Specifically, a simple process for converting waste bags into high-strength fibers and yarns is designed and tested in a feasibility study. The results demonstrate that by twisting and hot drawing, high-strength polymer yarns with mechanical properties at least comparable to those of commodity polymer fibers can be created. This may open up a new paradigm in plastic bags recycling and allow part of the recycling burden to be shifted to local residential communities.
A Novel Small-Diameter Eggshell Membrane/Tpu Double-Layered Vascular Scaffold With Wavy Structure
In this study, a double-layer, small-diameter vascular scaffold mimicking the wavy structure and mechanical properties of native blood vessels was developed. It was found that eggshell membrane (ESM) could provide an extracellular matrix (ECM) environment for human umbilical vein endothelial cells (HUVEC) in vitro. The avian eggshell membrane has a fibrous structure and has long been utilized in Chinese medicine for recovery from burn injuries and wounds in Asian countries. Therefore, ESM is expected to be an excellent natural material for biomedical use. However, its low mechanical properties have hampered its use in scaffold applications. Herein, we use synthetic thermoplastic polyurethane (TPU) fibers combined with ESM via electrospinning using a wavy cross-section rotating collector. The purpose of combining these two materials was to leverage the bioactivity of ESM with the tunable mechanical properties of TPU. The circumferentially wavy biomimetic configuration provides the scaffolds with a sufficient toe region and the capacity for long-term use under repeated dilation and contraction.
Low Emission, Uv Stabilized Lasermarkable Pom For Automotive Interiors
Laser marking on plastics is growing in use. Barcodes and product lot data can currently be marked with lasers some commodity resins. However, of specific interest is the use of lasers to mark functional or decorative information on engineering resins. Because of their inert surface characteristics, these resins can be difficult to mark via printing using ink. This paper focuses on the development of specialty grades of engineering resins that yield excellent sharp, clear images when laser marked. Grades have been developed for laser marking white characters on black, dark characters on white and other effects.
Effects Of Electroactive Crystal Phases And Porous Structure On Triboelectrication Of Poly(Vinylidene Fluoride)
Triboelectric nanogenerator is a promising technology that is capable of harvesting wasted mechanical energy. It is possible to modify the friction layers of triboelectric nanogenerators to improve their levels of triboelectrification and thereby their efficiencies. This paper aims to investigate the effects of electroactive crystal phases and foam morphology of polyvinylidene fluoride (PVDF), which can be used as the negative side of friction layers, on the performance of a triboelectric nanogenerator. Non-isothermal crystallization and supercritical carbon dioxide foaming were used to fabricate PVDF foams with high electroactive crystal phase contents. Under this approach, PVDF foams with pore size of ~15 μm and electroactive crystal phase content of ~62% were fabricated. Experimental results revealed that the maximum output voltage and current density achieved by using PVDF foams with high electroactive phase contents as the negative friction layers were 53.9 V and 5.1 mA/m2, respectively. This represents threefold increases in performance when compared to the case of solid PVDF friction layers with low electroactive phase contents.
Rheological Method Development: Using Rheological Tools To Predict Thermoformability
Extrusion thermoforming of very large parts such as those used in the appliance industry can exceed the melt strength limits of a given polymer. This study was undertaken to define new rheological tests capable of defining the molecular design required to avoid excessive sag in the heating step of the thermoforming process and to identify the optimum temperature for forming. Damping factor (tan = G’’/G’), also known as “tan delta”, can be used as a tool to identify fabrication conditions, molding window size, and the effect of added recycle streams. In addition, we compare polymer families that challenge our ability to thermoform large parts. Semi-crystalline materials must be run at or above their melting point temperature (Tm). Tm is well above the glass transition temperature (Tg) and the temperature delta (Tm - Tg) may exceed the width of any rubber plateau region in the melt state. These rheological characteristics are related back to the entanglement density of a given polymer and compared to the width of the rubber plateau.
Molecular And Morphological Parameters Governing Yield Behavior Of Polyethylene Pipe Materials
The ductile behavior of PE in Region I of the pipe failure regime is mainly governed by the time / and temperature-dependent yield stress of the polymer . Two different deformation mechanisms are relevant in PE. One governing shorter times and/or lower temperatures and the other longer times and/or higher temperatures which is relevant for the long-term ductile failure behavior of PE pipes. For the former, clear structure-property relationships were elaborated in literature. However, for the latter hardly any work was performed. This paper presents an accelerated method to characterize the ductile failure of PE pipes and tries to identify its limits and applicability. Furthermore, as a first attempt the structures of three model PE pipe grades are linked to their long-term ductile failure properties.
Novel V/P Transfer Actuation Method And Injection Molding Strategy And Their Comparison To Traditional Methods
The use of one novel and three well-known injection strategies were investigated to determine the effect on variation in part weight for each when variation in material viscosity and check ring leakage were introduced to the process. In addition, a comparison was made of the use of traditional screw position, cavity pressure sensing, and a novel switch closed by the melt front to actuate v/p transfer with each of the processing strategies. Velocity to pressure transfer when the part was not quite full (2-stage, pack with second stage), after the part was packed with a fast velocity (2-stage, pack with first stage), and after the part was packed with a slow velocity (3-stage) were the well-known injection strategies evaluated. The novel strategy was a modified 3-stage where the v/p transfer was actuated after the first velocity (as in 2-stage, pack with second stage) and the pack velocity was set as the limit during the first profile of the second stage of injection. It was found that the modified 3-stage process reduced variation compared to traditional 3-stage and that the novel switch used to detect the flow front was the most consistent method to actuate v/p transfer.
Evaluation Of Novel Switch To Detect The Melt Flow Front In Injection Molding
A cost effective filling control device was designed, prototyped, and evaluated in an attempt to reduce variation in the quality of injection molded parts. The patent pending method consists of an internal switch that is actuated by the melt flow in the cavity. A four run full factorial DOE was carried out for each of the V/P transfer methods that were compared: screw position, cavity pressure, mold surface temperature, and the new in-mold switch (MeltSwitch™). The part weight was measured to determine how each method was affected by viscosity and decompression variation. It was found that the mold surface temperature and MeltSwitch™ performed the best in minimizing part weight variation.
Wet Compounding Of Cellulose Nanocrystals Into Polylactic Acid For Packaging Applications
Cellulose nanomaterials have been demonstrated to improve the mechanical and barrier properties of various polymers, but numerous challenges, such as drying, remain to viably produce polymeric cellulose nanocomposites for packaging applications. In this paper we describe a method for drying and blending cellulose nanocrystals into polylactic acid (PLA) using a single process referred to as wet compounding. Aqueous suspensions of CNCs were directly compounded with PLA in a thermokinetic mixer in which viscous heating creates sufficient temperature to evaporate water and melt polymers during mixing. Here, CNCs with and without lignin were compounded with PLA followed by cast extrusion to produce films, which were evaluated for their mechanical and barrier properties. Composite films with de-lignified CNCs produced through wet compounding were found to have improved mechanical and barrier properties compared to neat PLA, whereas lignin-containing CNCs did not improve the barrier properties of PLA. The process of rapid wet compounding was not found to detrimentally affect the properties of PLA controls. In addition, using a discharge temperature setpoint well below the melting point of polymer resulted in the most favorable composite properties, indicating that further optimization and investigation of wet compounding is needed. The use of novel processing, such as wet compounding, has tremendous promise for advancing the viability of cellulose nanocomposites.
Method To Utilize Aligned Carbon-Fiber Prepreg Trim Scrap For Structural Applications
The pressure for increased fuel economy and low CO2 emissions for automotive vehicles continues. In order to satisfy requirements, lighter vehicles will need to be manufactured making it necessary to replace metals in structural components with lightweight materials such as carbon fiber composites. The challenge associated with implementation of carbon fiber composites is to make them cost effective for high volume production because historically this class of materials was designed for low volume production scenarios. In order to apply carbon fiber prepreg derivatives to high volume automotive applications, the material must be designed so it can be robotically handled, and reduce expensive material usage inefficiencies while utilizing existing processing equipment. This work presents an innovative mechanical method to incorporate uncured carbon fiber reinforced polymer “in-process” scrap to completely utilize the waste material in three-dimensional reinforcing rib features of a structural automotive application, and demonstrates an efficient material use method to provide cost savings with aligned carbon fiber prepreg designs. This paper compares the mechanical properties of the discontinuous fiber reinforced composites prepared using virgin carbon fibers and reutilized carbon fiber prepreg scrap.
'Advancements In Aspects Of Automotive Anti-Scratch'
Slip additives have been used to reduce friction in films, aid mold release, and facilitate the application and removal of closures. Mono-unsaturated fatty acid amides, such as erucamide and oleamide, are traditionally used for high slip application. At modest dosing, these additives provide high slip performance at low addition levels, typically below 0.5%. However, these products are prone to breakdown due to prolonged exposure to UV light, high ambient temperatures, and oxidation. Croda determined there was a need for a more stable slip additive that does not reduce in performance over time. Incroslip™ SL is Croda’s latest innovation in slip additive technology. Through the course of two case studies it was found to provide excellent stability over time, which benefits to extended shelf life and cost savings, and optimum torque release and application performance through dosing HDPE via a LDPE masterbatch.
A Composition-Morphology Mapping Of Fumed Silica Filled Polymer Blends
We explore the effects of adding fumed silica particles to blends of two immiscible homopolymers, polyisobutylene (PIB) and polyethylene oxide (PEO) across a wide range of composition. Blends of PIB and PEO with fumed silica loading up to 10 vol% were studied. The fumed silica has strong affinity for PEO, and hence, when there is enough PEO to fully engulf the particles, a combined phase of fumed silica-in-PEO is formed. Due to the fractal-like nature of fumed silica particles, this combined phase can be strongly solid-like even at low particle loadings. We observed two morphological changes different from what was observed in spherical particulate filled in polymer blends studied in the past. The first is that, at low loadings of fumed silica, a huge qualitative change was seen in the morphology of the polymer blends. More specifically, particle-free blends that showed a dispersed phase microstructure often became cocontinuous upon adding particles. The second is when fumed silica together with the PEO formed a combined phase, a capillary aggregates network survived across a wide range of composition at 10vol% fumed silica loading.
Development Of Multifunctional Composites For Space Radiation Shielding Applications
Development of a novel polymer matrix composite material comprised of ultra-high molecular weight polyethylene (UHMWPE) fiber reinforcement and hydrogen-rich polybenzoxazine is reported. The composite material is targeted for use in aerospace applications that require a unique combination of structural functionality and excellent space radiation shielding performance. Composite samples were prepared using a low-pressure vacuum bagging process and utilize a newly developed benzoxazine resin that features a unique combination of high hydrogen concentration, low polymerization temperature, and low viscosity. Mechanical properties were characterized by tensile testing and indicate that the composite possess high tensile strength. Radiation shielding performance was evaluated using computerbased simulations. Specific strength and equivalent radiation dose were determined from test and simulation data and used as performance metrics to evaluate multifunctional capability. Compared to aluminum, the composite provides a 325% increase in specific strength and an estimated 31% reduction in equivalent radiation dose.
Simulation And Testing Of A Heat Pipe Tempered Injection-Mold-Tool Vs. Conventional Water-Based Cooling
An injection mold, developed by the Bielefeld University of Applied Science (FH Bielefeld), can be tempered via water or heat pipes (Figure 1). The practical validation shows the comparison between conventional water based tempering and the technology using heat pipes, focusing on cycle time and temperature at the cavity. Regarding cycle time, these new Heat pipes operate as efficiently as the water-based technique, but they need less energy input and allow lower complex mold design. The heat flux simulation of the mold is highly sophisticated. The deviation between the real process and the simulation shows temperature differences smaller than 5 °C.
Highly-Filled Polymeric Systems For Sheet Extrusion
Highly-filled polymer systems are color masterbatches and feedstock for powder injection molding, but have not been fully explored in sheet extrusion. This work investigated the selection of a polymer matrix with enough melt strength and flexibility, the maximum achievable filler loading, and processing issues arising when extruding a highly-filled polymer system. Extrusion grade low density polyethylene (LDPE) provided sufficient flexibility and permitted a maximum filler loading of 36 vol% (~77 wt%). Good dispersion of the filler, however, required two passes through multiple screw extruders and a small reduction in the viscosity of the LDPE. Flexible sheet with a thickness of 415 μm and surface roughness of < 1 μm was extruded continuously at a rate of 10 m/min., but required a more traditional coat hanger manifold to prevent filler hang up in the die. The filler particles were distributed uniform through the core and skin of the sheet, giving the sheet good mechanical properties.
Overview Of Next Generation Engineering Thermoplastics For Consumer Electronics
As the wireless network evolves from 4G to 5G, the data transfer rate of consumer electronics increases dramatically. The devices also need to host more powerconsuming / heat-generating functions, while maintain stylish as well as robust design. These trends coupled with the fast product cycle of consumer electronics demand for forward-looking innovation of materials, particularly engineering thermoplastics. This article summarized recent innovations in liquid crystal polymer (LCP), PPS, PBT, and thermal conductive polymers that address the needs in mobile devices components such as compact camera modules (CCM), antenna, antenna window, speaker & receiver, and connectors.
Which Extruder System For Which Compounding Job? A Reliable And Field-Tested Methodology
There is no all-round compounder. No individual extruder can handle equally well all the challenges posed in practice. Key for specific compounding tasks are often the individual steps, such as feeding of poorly flowing or very high-volume additives, efficient melt degassing, or particularly gentle plasticization of sensitive plastic compounds. So which extruder is best for the task in hand? Alternatively, which extruder can flexibly handle the widest range of compounding applications costeffectively? Moreover, when is a customized solution the best? A brief introduction in evaluation methodologies are given and illustrated with practical examples.
Quad Screw Extrusion Of Highly-Filled Polymer Composites
A novel ultra-high-speed quad screw extruder was employed to examine the effect of screw speed (i.e., high shear rate) when compounding composites with high filler loadings. Calcium carbonate (CaCO3) was selected as the filler because its high surface area and particle shape make it challenging to disperse and stabilize high levels of CaCO3 within the polymer matrix. Three different polyethylenes were compounded with 10, 40, and 70 wt% micro CaCO3 at screw speeds of 500, 1000, 1500, and 2000 rpm. Increasing both screw speeds and filler loading level decreased drive torque and head pressure while increasing mixing zone and melt temperatures and power consumption. In the resultant compounds, the complex viscosity increased with filler loading level and decreased with increasing screw speed. The tensile properties of exhibited a greater dependence on filler loading level, but screw affected the stress and strain at break. Izod impact results that showed no major changes, except for both LDPEs with 70 wt% calcium carbonate. Although these results are related to the degree of dispersion of the calcium carbonate produced by the quad screw extruder, additional research (currently in process) is required to understand the effect of processing and materials in resultant compounding.
Control Of Pa6/Pp Biocarbon Composite Morphology By Varying Biocarbon Content
This manuscript aims at investigating the influence of biocarbon content on the morphology of binary immiscible blends. Herein, polyamide 6 (PA6) and polypropylene (PP) were prepared at blending ratios 20/80 and 80/20. The dispersed droplet size was determined from scanning electron microscopy measurements and compared to the elastic and loss modulus of the systems measured by oscillation rheology. The biocarbon content showed a significant effect on the dispersed droplet size. In case of the PP dispersed phase the use of high biocarbon content is beneficial to decrease the droplet size while systems containing PP in the matrix should use a low amount of biocarbon.
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