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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Design and Optimisation of a Standard Milk Crate Using FEM
This paper presents an investigation on the design and optimization of plastic milk crates using the finite element method (FEM) with the aim of reducing the mass and simplifying the shape of a standard milk crate. The paper also explores the possibility of manufacturing such milk crates using recycled High Density Polyethylene (HDPE) instead of virgin HDPE or virgin polypropylene (PP) to make it more cost effective.
Clay Exfoliation and Content Effect on Nylon Nanocomposite Foams
Amorphous nylon 6 nanocomposites with various clay contents and dispersion degrees were prepared by direct twin-screw extruder compounding. The nanocomposite structures were examined with XRD and TEM. The effects of clay exfoliation and content on microcellular extrusion foaming of amorphous nylon 6 nanocomposites will be presented. Apart from their nucleating role in bubble nucleation, nanoclay particles also promoted the volume expansion ratio of nylon foams. The role of clay particles on diffusivity will be discussed critically.
Domain Decomposition for 3D Flow Simulation of Injection Molding
This work generalizes D-N and Schwarz schemes for elliptic equation to Stokes and injection molding problem and constructs the non-overlapping and overlapping sub problem. It divides the original problem into several sub problems and distributes them to different processor to solve simutaneously. This method can accelerate the 3-D flow simulation involving large scale calculation.
Wall Thickness Optimization in Molded Product Design
Wall thickness is a vital design decision that affects structural performance, material utilization, and processing costs. Simple flow and bending analyses are developed and validated against sophisticated 3D finite element analyses for use in early product development. The simple analysis indicates the desirability of 1) simultaneous wall thickness and rib design, and 2) adding ribs to the design to increase stiffness as needed. Finally, calculus is applied to solve for optimal flow length to wall thickness ratio as a function of material costs and machine rates.
Design of an Instrumented Mold to Verify Air Gap Formation during Cooling in Box-Shaped Parts
Shrinkage occurs asymmetrically during the cooling stage of an injection molding cycle. When this happens, especially in box and cup shaped injection molded parts, an air gap forms, drastically reducing heat transfer rates into the cavity steel. In order to verify the gaps existence and volumetric size, an injection mold is modified with componentry to quantify the separation from cavity steel.
Heat Transfer Study of Air Gap Influence on Cooling in Boxshaped Parts
Air gap influence on cooling in cup shaped parts is an undocumented phenomenon, requiring additional analysis and quantitative measurement. As an enhancement to a previous investigation, the heat transfer behavior of a plastic part is analyzed by using a finite-element model that incorporates shrinkage, and resulting gap, from PVT estimates. The heat loss of a part without an air gap and one with an air gap are contrasted to determine the significance of the air gap on cooling.
New High Impact Miscible Polycarbonate Polyimide Blends
Blends of polyetherimides usually form phase separated mixtures with polycarbonate or polycarbonate esters, however recent work shows surprising miscibility when a polycarbonate ester with a high percentage of resorcinol derived ester linkages is used. The transparent blends have lower color, improved melt flow and increased practical toughness compared to an unblended polyetherimide. Additionally, three component blends of resorcinol based polycarbonate ester, polyetherimde and polyester also demonstrate miscibility.
EVOH/Clay Nanocomposite Systems: Processing–Structure–Property Relationships
EVOH/clay nanocomposites were prepared via a dynamic melt-intercalation process using a Brabender plastograph or an extruder machine. A model of clay fracturing and an onion like delamination was suggested. EVA-g-MA or LLDPE-g-MA were added as compatibilizers of EVOH with clay, at various concentrations. Clay-containing Ny-6/EVOH blend is a unique system, in which chemical reaction in addition to hydrogen bonds formation between the EVOH/Ny-6 components in the blend was found to take place.
Surface Recovery of PDMS after Exposure to UV/Ozone
Controlled surface oxidation of polydimethylsiloxane (PDMS) is commonly used in manufacturing of microfluidic devices since it is a very effective method of both bonding PDMS components together, and altering the surface properties of PDMS. The stability of these modified surfaces is crucial in determining the lifetime and reliability of the device. This paper investigates the stability of UV/ozone modified PDMS surfaces using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).
XPS Analysis of Uv Curable Adhesive and its Adhesion to PDMS
Adhesive joints were prepared between polycarbonate (PC) and polydimethylsiloxane (PDMS). This paper presents an x-ray photoelectron spectroscopy (XPS) investigation into the chemistry of adhesion between the adhesive and PDMS. UV pretreatment of the PDMS surface proved essential in obtaining strong adhesion.
Formulation of Optimally Stabilized Poly(Vinyl Chloride) Systems with the Aid of the Chemiluminescence Technique. Part II
The Chemiluminescence (CL) technique has been shown to be an accurate method to detect the formation of polyene sequences in the degrading PVC compounds. This part 2 of the paper analyzes the functions and performances of different classes of thermal stabilizers and co-stabilizers, i.e. mixed metal carboxylates, mercaptides, organic and inorganic HCl absorbers, phosphites and antioxidants by their CL. The ways of formulation of well rounded stabilization are offered.
Preparation of Poly(Methyl Methacrylate) and Carbon Nanofiber Composites by Chaotic Mixing
Composites of poly (methyl methacrylate) and carbon nanofibers were prepared in a chaotic mixer, and electrical conductivity and quality of dispersion were compared with those produced in conventional mixers. The threshold for electrical conductivity was about 1.5 wt. % for materials prepared in a chaotic mixer, while those produced in batch and continuous mixers were not conductive up to a loading of 4 wt. %. Thermogravimetric analysis revealed that the presence of carbon nanofibers delayed thermal degradation of the polymer.
Nanomechanical Properties of Viscoelastic Polymers
The surface mechanical properties of ethylene vinyl acetate (EVA) with various vinyl acetate (VA) contents have been investigated. These nano mechanical properties, obtained from the nanoindentation technique, were compared with bulk results from the conventional tensile test. Agreement in Young's modulus as a function of VA content is found between two data. The discrepancy in modulus value between surface and bulk was also found in EVA with higher VA content. We speculate that this is due to macroscopic structure effect on bulk modulus as well as intrinsic viscoelastic deformation behavior of EVA.
An Investigation into Hesitation Effects in Oscillating Flows
The hesitation effect is well known to adversely affect the appearance of molded products. In this paper, the effect of hesitation on aesthetics and dimensional properties is investigated via a design of experiments varying the materials, melt temperature, coolant temperature, injection velocity, and oscillatory time. Analysis and molding validation indicate that hesitation is related to solidification of the melt front rather than changes in melt shear stress.
Performance of a Self-Regulating Melt Pressure Valve
Injection molding has been limited by the lack of direct flow and pressure control of the polymer melt at multiple points in the mold during the molding cycle. A selfregulating melt pressure valve has been developed whereby the outlet melt pressure is proportional to the control force on the valve pin. This paper validates the capability to provide melt pressure control proportional to the supplied pneumatic pressure without melt pressure transducers.
Design and Performance Analysis of a Self-Regulating Melt Pressure Valve
A design for a self-regulating pressure valve is analyzed using a 3D flow analysis that utilizes independent shear and elongational viscosities for the polymer. The regulator is derived from a low force valve design that enables the outlet pressure to be directly regulated by a provided force on a valve pin without need for pressure sensors or a closed loop control system. Analytical and experimental results indicate an excellent level of response and consistency given the simplicity of the design.
Validation of On-Line Molding Process Simulation
Plastics injection molding has been limited by the lack of observability and controllability, such that it has not been possible to know or control flow rates and pressures at multiple locations in a mold. Using cavity pressure transducers and faster than real time process simulation, the described system provides estimates of the flow rates, part weight, melt temperature, and apparent viscosity before the mold opens and the parts are ejected. Validation results for part weight are provided for a two-cavity family mold with a valve-gated hot runner system.
Derivation of Process Windows
Selection of set-points is of vital importance to the quality and economics of manufacturing processes. However, most recipes are developed from recursive trial and error interpreted via prior human experience. A new analytical procedure based on the Extensive Simplex Method is presented that derives the global process window for an arbitrary number of process parameters and quality specifications that requires minimal process experimentation. The methods are applied to an injection molded component with width, length, and flash specifications and shown to provide excellent results.
Concept Design of a Wireless Pressure, Temperature, and Flow Rate Sensor for Injection Molding
A new concept design for a self-energizing, wireless sensor is presented. The sensor extracts energy from the polymer melt and transmits discrete acoustic signals whose timing indicates a pressure change and whose frequency indicates the melt temperature. A receiving system outside the mold receives the transmitted signals and reconstructs the melt pressures and temperatures. It then utilizes mapping and simulation techniques to estimate the pressure, temperature, and flow rates in the entire mold in real time.
A Review of In-Mold Pressure and Temperature Instrumentation
A survey of commercially available and broadly used pressure and temperature sensors for injection molding is presented. The various pressure and temperature sensing means are reviewed along with the geometry and performance of common transducers. Usage and trade-offs in sensor design and selection is discussed.
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