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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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.
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.
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.
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 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.
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 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.
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.
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.
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.
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.
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.
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.
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.
The type, amount, and composition of the modifier and its interaction with the polyamide matrix determines the stiffness-toughness-flow balance of its blends with polyamide. Beyond these primary requirements, depending on the application, low temperature impact, color, gloss, heat resistance, melt strength in extrusion and blow molded applications influence the choice of the right modifier. In glass filled nylon, glass fiber wetting is also an important consideration. Bulk handling options with some modifiers can help manufacturing efficiency. Finally, the choice of the nylon (for example PA 6 vs. PA 66), molecular weight and end group concentration all affect the end use properties. This paper gives a balanced overview of various differentiated solutions to modify polyamides using blends with various ethylene based reactor or grafted copolymers. Modification of both PA 6 and PA 66 is discussed.
A new analysis of the solids conveying of single screw extruders is developed. The new model is based on an assumption that the compressed solid are transported to down channel direction by pushing up of flight on the screw, initially relative movement of barrel to the stationary screw. The new analysis when tested with measured polymer processing properties such as data of dynamic friction date, bulk density, and two lateral stress ratios, was found to be in excellent agreement with all geometry and operating conditions for the available experimental data.
A new rheology measurement for the gum rubber and rubber compounds has been conducted using screw rheometer. This device uses a new viscometric flow analysis of single screw extruders to measure shear viscosity, which is based upon 'the closed dischage' extrusion characteristic equation. The screw rheometer, which is characterized by self-plasticating, self-deaeration, mixing during measuring and fast measuring time, shows the average polymer properties of the sample because the measurement volume is large enough. This study especially shows that shear viscosity and stress relaxation experiments of gum rubber and compounds can be performed by using this device. The measured viscosity is a function of shear rate, thus it can be used for the analysis of processing, machine design and quality control of the rubber manufacturing. Also, a rubber relaxation time experiment was devised as a method to confirm the relaxation time in the processing range and is named 'Engineering Relaxation Experiment'.
This article elaborates the production and characterization of maleated thermoplastic starch (MTPS) and MTPS-g-PETG (glycol modified Polyethylene terephthalate) graft copolymers using reactive extrusion. Maleated thermoplastic starch (MTPS) was prepared by reaction with glycerol and maleic anhydride in a properly configured twin screw extruder. Maleic anhydride (MA) promoted cleavage of the starch molecule resulting in lower molecular weight and increased hydroxyl groups. The % of glycerol grafted on starch backbone was calculated using soxhlet extraction with acetone. MTPS was transesterified with PETG in 30:70 ratio w/w to obtain graft copolymers. Soxhlet extraction with dichloromethane (DCM) showed that around 30 % PETG was grafted on MTPS. The results were confirmed by TGA and FT-IR analysis of residue and extracts. The tensile strength and % elongation of graft copolymer was less as compared to neat PETG but much better as compared to brittle MTPS. Finally, dispersion of MTPS in PETG as continuous phase was observed using the images from scanning electron microscopy.
Synthetic elemental carbon (carbon black) has many applications. Carbon black has been used as a coloring agent and filler for rubbers in the manufacturing of tires. However, natural carbon (biocarbon)—traditionally used as a soil amendment— is carving its way towards industrial applications as a natural colorant for plastics and as a reinforcing filler in plastic composites. The reinforcing properties of elemental carbon are well known. However, the mechanism is still described mostly as physical interlocking and in some cases as an affinity between the rubber to specific morphologies present in carbon black. Elemental differences between these two sources of carbon are discussed in this paper as well as the mechanical and thermal properties of both materials when used as reinforcing filler in a plastic matrix.
Conductive polymer nanocomposites (CPN) filled with conductive filler have become increasingly popular due to their combined flexibility and low cost. This work explored the electrical properties and piezoresistive behaviors of CPN consisted of high density polyethylene (HDPE) and thermoplastic polyurethane (TPU) as well as multiwalled carbon nanotube (MWCNT) and/or graphene nanoplatelet (GnP), and their foams. The study investigated effects of CNT-to-GnP ratio on CPN’s structural morphology, foaming behavior, electrical conductivity, and piezoresistivity. The preliminary tests for the recoverability and reproducibility of the materials piezoresistive measurements look promising, and a reallife application using this material has been demonstrated by constructing a prototype sensing device.
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