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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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.
Solutions For Polyamide Impact Modification Based On Ethylene Copolymers And Elastomers
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.
Development Of New Solid Conveying Model Based On The Actual Measurement Of Polymer Processing Properties
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.
The Screw Rheomter: A Novel Rheometry For The Thermoplastic And Rubber Material
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'.
Preparation Of Maleated Thermoplastic Starch And Its Graft Copolymers Via Reactive Extrusion
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.
Reinforcing Phenomena Of Elemental Carbon: The Case Of Carbon Black Vs. Biocarbon In Composite Uses
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.
Piezoresistive Polymer Nanocomposites And Their Foams As Smart Sensing Materials
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.
Thermal Properties Of Carbon Fiber Reinforced Polyamide 66 Composites Throughout The Direct Long-Fiber Reinforced Thermoplastic Process
The direct long fiber reinforced thermoplastics (D-LFT) process is a series of processes involving two twin-screw extruders, a conveyer, and a compression molding machine. This study investigates variation on thermal properties of carbon fiber reinforced polyamide 66 (PA66) composites throughout the D-LFT process. Samples were taken from five different locations along the D-LFT process and characterized using thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results suggested that the thermal stability was decreased continuously up to the halfway point of the conveyer, but increased from the half conveyer to the compression molding. The degree of crystallinity was little changed throughout the process, but the crystallization half-time was increased after the half conveyer.
Effects Of Fiber Content On Optical, Viscoelastic, And Thermal Properties Of Cellulose Nanofiber Reinforced Poly(Methyl Methacrylate)
This study investigates the effects of cellulose nanofiber (CNF) content on optical, thermal, and viscoelastic properties of CNF reinforced poly(methyl methacrylate) (PMMA). CNF/PMMA with different CNF contents were prepared through a solution casting method with acetone and compression-molded to create nanocomposite films. The films were characterized using an ultraviolet–visible-near infrared (UV-VIS-NIR) spectrophotometry, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results suggested that the viscoelastic and thermal properties of the CNF/PMMA were increased with the increase of CNF content while maintaining a high degree of transparency and increasing attenuation capability of ultraviolet light.
Injection Molding And Injection Compression Molding Of Ultra-High Molecular Weight Polyethylene: Minimized Thermal Degradation And Delamination Layer Formation
Ultra-high molecular weight polyethylene (UHMWPE) in powder form was processed using injection molding (IM) with different cavity thicknesses and injection-compression molding (ICM). Tensile tests and impact tests showed that the ICM samples were superior to those of IM. Increased cavity thickness and ICM were helpful for improving the mechanical properties due to effective packing of the material. A delamination skin layer (around 300 μm thick and independent of cavity thickness) was formed on all IM sample surfaces while it was absent in the ICM samples, suggesting two different flow behaviors between IM and ICM during the packing phase.
Investigation Of The In-Flow Effect On Weld Lines In Injection Molding Of Glass Fiber Reinforced Polypropylene
In the injection molding process, weld lines can occur when two flow fronts rejoin due to either multi-gated molds or obstacles in the mold cavity. The weakness of plastic at weld lines provides serious difficulties for the design and long term durability of injection molded parts. Various methods to reduce the strength loss of weld lines include optimization of material composition, mold design and process conditions. To this purpose, this paper experimentally explores the influence of in-flow on the strength of weld lines for a commercial polypropylene compound reinforced with glass fibers. In-flow is defined as the flow within the mold cavity, below the solidified layer, that continues after the local region of the mold cavity is filled. In particular, the comparison of the weld line strength between specimens manufactured with and without in-flow was carried out and related to the reinforcement distribution in the welding zone.
Experimental Setup Design For Processing Functionally Graded Cellular Composites In Rapid Rotational Foam Molding
This paper presents a new manufacturing process for producing functionally graded foam for rapid rotational foam molded composites (RRFM). A new experimental setup incorporates continuous foaming operation using a physical blowing agent (PBA) and a chemical blowing agent (CBA) to deliberately generate a foamed core with varying quality based on preferred direction or orientation. Carbon dioxide will be used as the PBA to produce ultrafine cellular foam. This novel process utilizes a static mixers to create a single phase solution before foam injection phase. In the co-extrusion operation, one extruder will be used for CBA-based fine cell low density foam production and the other for PBA-based ultra-low density polymeric foaming operation.
Copolyester Elastomers For Automotive Applications With Focus On Cvj Boots
Copolyester elastomers are high performance thermoplastic elastomers, based on a polyester hard segment and a polyether or aliphatic polyester soft segment. Copolyester elastomers are used to replace thermoset rubbers in CVJ (constant velocity joint) boot applications. These require thermal stability and resistance to greases. Copolyester elastomers are well known for these properties. When the surfaces of the boots come into contact with each other (i.e. at large turning angles) this can cause squeaking noises. Looking at the future, more and more electric or hybrid cars will be built. Until now the squeak noise was muffled by the combustion engine. Electric or hybrid cars require reduced noise emission in dry and humid environments. This paper provides an overview of copolyester elastomer applications for automotive with focus on CVJ boots and noise emission testing in different environments.
Designer Polymers: Additive Manufacturing Of Smart Materials As A Complement To Injection Molding
This paper presents the idea of “designer polymers” – these are polymers that can be custom formulated to include sensing, computation, and actuation infused throughout the bulk of the material. Designer polymers are useful in the design and fabrication of smart products and we believe they will revolutionize the co-design of complex products. The co-design of smart products involves the simultaneous design of, for example, hardware and the software that executes during the functioning of the device. In our quest to develop designer materials, we have explored a variety of fabrication methods, including insert-molding and 3-D printing, or additive manufacturing.
Contribution Of Flow Instability To Tiger Stripes Of Polypropylene Copolymers
Tiger stripes of polypropylene copolymers are studied by modeling the mold filling process as a non-isothermal two-phase flow using a level-set method. It has been shown that the Level Set method is capable of modeling the evolution of the flow field at and behind the melt front. An area of large velocity contrast between the skin layer of high shear rates and the center core of low shear rates has been observed behind the melt front under relevant injection molding conditions. The large velocity contrast appears to be a direct origin of the flow instability. The instability in terms of alternative occurrence and disappearance of the oscillatory strain rate is proposed to be a possible root cause of the tiger stripes. The comparison of the materials of different rheology suggests that shear thinning may be a useful property to mitigate the risk with the tiger stripes.
Preventing Discoloration In Thermoplastic Polyurethanes
Thermoplastic polyurethanes (TPU) are a versatile class of elastomeric polymers with physical properties that can be tuned to meet a wide range of demanding applications. TPU is known for its elasticity, transparency, abrasion resistance, and chemical resistance. This combination makes TPU an attractive material to replace materials such as rubber or polyvinyl chloride in many applications. However, like many polyurethanes, TPU is prone to oxidation and discoloration during processing and upon weathering. In this paper, combinations of antioxidants, process stabilizers, and light stabilizers were investigated to determine the best additive combinations to reduce the tendency of TPU to discolor.
Evaluation By On-Line Ftir Of The Kinetics Of Pp/Pa6 Blend Compatibilization With Pp-G-Mah During Extrusion
The on-line evaluation of the effects of process conditions variation during the extrusion process on the kinetics of compatibilization of polyamide 6 (PA6) in a matrix of polypropylene (PP) compatibilized with polypropylene grafted with maleic anhydride (PP-g-MAH) in different locations along the extruder by infrared (FTIR) spectroscopy is proposed in this work. As preliminary results and as a basis for comparing the on-line results that will be shown in the presentation the evolution of dispersion of the second phase of PA6 in the PP matrix is presented here. The area ratio of the peak of carbonyl stretching in amide present in PA6 at 1640 cm-1 standardized to the IR area of the peak at 1170 cm-1 relative to PP is applied to evaluate the evolution of dispersion along the extruder and the effect of the process condition in it. The standard deviation (s.d.) of the area ratio was used to correlate to the changes in dispersion condition when the process temperature, the feed rate and the screw speed were varied.
Mechanical Failure In Agricultural Silo Bags
Silo bags are used for bulk storage of grains in farmland. There are two typical modes of their failure: while being filled with grains, or due to long-term creep deformation during storage. In the past, several numerical studies have been conducted to improve the quality of grains stored in these bags by optimizing the moisture content or CO2 levels. The failure of these bags, however, especially when excessive pressure is applied during grain filling and subsequent creep during storage, is not well understood. Explicit Dynamic Solver in Abaqus (Product of Dassault Systems Simulia Corporation, USA) was used to model polymeric silo bags storing granular material under gravitational loading and pressure. The material computational model for silo bags (film) and the granular material has been developed using material subroutines, which themselves have been calibrated through in-house tensile and creep testing for the film. Numerical analysis of agricultural silo bags has been performed to understand mechanical failure in the bags during installation and usage at different temperatures.
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