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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Non-Linear Rheological Response As A Tool For Measuring Dispersion In Nanocomposites And Blends
Polypropylene (PP) was blended with polycaprolactone (PCL) and nanoclay (NC) in a twinscrew extruder (TSE) using a traditional extrusion process or a sub-critical gas assisted process (SGAP). Impact, morphology, and X-ray diffraction (XRD) properties indicated a smaller PCL phase droplet size and an increase in dispersion of the NC when SGAP was used. Standard small amplitude oscillatory (SAOS) rheological tests for storage modulus G’ were not sensitive enough to discern the difference between the traditionally extruded and SGAP samples. Fourier Transform rheology was used to determine the intrinsic non-linearity Q0, which was able to distinguish the added dispersive and mixing capabilities of SGAP. Practical implications of SGAP and Fourier-Transform (FT) Rheology are discussed.
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.
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.
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.
'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.
Effect Of Cooling Time, Packing Pressure, And Antistiction Coating On Replication Of Micro Molded Substrates
Micro injection molding is one of the most widely utilized technologies to manufacture micro parts. One of the most challenging aspects in micro injection molding is to understand the role of different processing parameters on the quality of replication of the micro-features. This study will examine the effects of packing pressure in order to replicate micro features with high filling accuracy for micro molds with oval and cylindrical shapes. Moreover, part demolding is a critical factor where the chance of damaging the created patterns is high. So, cooling time is examined to eliminate micro pillar distortion during part demolding. Furthermore, the ability to mold micro pillars using a silicon mold without antistiction coating using Thermoplastic Polyurethane (TPU) is investigated. A key finding was that the degree of distortion of the micro pillars edges during demolding stage is strongly related to cooling time. Silicon molds were used in this study because of the ease of fabrication of cavities at a micron scale in these materials following deep reactive ion process even though silicon is not an ideal mold material as it is brittle and the polymers tend to adhere to silicon during processing. Keywords: micro/nano injection molding, microfabrication, packing pressure, cooling time, antistiction coating.
Polycarbonate-Polyester Blend Degradation Behavior
Objective of this paper is to document the efficacy of additives being used to minimize the antagonistic effects of ester interchange reactions that take place during high temperature processing of polycarbonate and polyester blends. Polycarbonate/polyester alloys suffer from loss of physical properties and moisture resistance due to ester interchange reactions. With right additives, the physical properties can be improved. Six different additives, that are phosphorous compounds and oxides of metals in nature were used to blend polycarbonate (PC) and polyesters. To improve the miscibility between the PC and polyethylene terephthalate (PET), a compatibilizer was added. Based on physical and analytical properties, certain additives have been identified as performing better than the rest. The properties selected to study are focused on understanding the impact of these additives on hydrolytic stability, tensile strength, heat deflection temperature, impact strength, and enthalpy and rate of crystallization. Degradation of physical properties and decrease in enthalpy of crystallization are indicative of loss of long term chain order and formation of unwanted copolymers in PC/Polyester blends.
Rheology Of Molten Polyolefin Interfaces: Slip In Shear, Hardening In Extension
While barrier, optical, dielectric, and mechanical properties of multilayer polymer films have been studied extensively, there is comparatively little regarding the melt rheology of these multilayer films that would inform secondary processes such as thermoforming and biaxial orientation. Here we expand on our previous work regarding polyethylene/polypropylene (PE/iPP) solid-state adhesion to study the molten interface of 640 layer PE/iPP films. The interfacial tension of a metallocene linear low density polyethylene (mlE) and metallocene iPP (miP) system was measured by blending miP into mlE. The small amplitude oscillatory shear (SAOS) data was fitted with the Palierne model to extract an interfacial tension. Interfacial slip of the multilayer mlE/miP system was observed at shear stresses greater than 10 kPa. While neither mlE or miP homopolymer exhibited strain hardening behavior, the 640 layer mlE/miP system possessed a higher plateau extensional viscosity than anticipated as well as pronounced strain hardening behavior. These results suggest the molten interface has a significant impact in the secondary processing of extruded polyolefin films and may be an avenue to enhance thermoformability of iPP films.
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