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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Micro Molding of Polymer Cantilevers for Sensor Applications
In recent years there has been considerable interest in the micro molding process as the trend slanting towards miniaturization. In the present paper micro molding process studies have been carried out on the micro molding of polymer cantilevers for sensor and actuator applications. Microgrinding, EDM, and micro-EDM methods have been used for fabrication of micro cantilever tools. The effects of micro mold surface roughness and process conditions on part quality have also been studied.
Development of a Micro/Nano Injection Molding Testbed
In this work, an injection molding test bed is being developed that is designed specifically for molding micro-scale parts with nano-scale features. The device is designed to mold with sub-milliliter sample sizes and to produce arbitrarily large injection velocities and injection pressures. Initial experiments have produced 125 micron thick, 5000 micron diameter center gated disks with a nanometer scale sinusoidal surface texture. This surface texture will be used to measure shrinkage and warpage on the micro-scale using Micro-Moire.
Assessing Vibration-Assisted Injection Molding through Fatigue Lifetime Studies
An investigation into fatigue lifetime behavior of polycarbonate and polystyrene materials processed by both conventional and vibration-assisted injection molding (VAIM) is underway. The goal of this investigation is to determine whether the vibration-assisted process improves the fatigue behavior. In addition to characterizing fatigue behavior, the micromechanical deformation mechanicals controlling fatigue behavior will be elucidated.
Counter Flow Injection Molding - An Alternative Method for Producing Parts with Sandwich-Like Morphology
Counter-flow injection molding (CF) is a novel two-component method which can be used for the production of parts with sandwich-like morphology. Compared to some established two-material techniques, CF can induce a higher overall level of molecular orientation and hence an improved mechanical performance. The technique requires a two-component injection molding machine fitted with a special mold. The developed microstructure and mechanical properties of CF moldings are investigated in light of the applied set of processing conditions.
Use of Infrared Thermal Imaging to Study Mold & Part Cooling
Infrared thermal imaging has been successfully applied to numerous applications involving electrical, mechanical and building maintenance. Application studies involving plastics have been mostly successful yet our industry does not use Infrared Thermal Imaging. It has not caught on in the plastics industry. This paper presents a series of practical applications involving plastic and mold cooling troubleshooting and analysis. Infrared Thermal Imaging has evolved into a viable method for fast, accurate and economical mold and part cooling studies
Saving Time by Foam Injection Molding
Foam injection molding (FIM) offers many advantages. One of them is a high potential for cooling time reduction compared to standard injection molding. This paper deals with a thorough investigation on the potential of cooling time reduction by FIM. Results will be presented and discussed in depth.
Designing the Cooling System: What's the Relationship between Mold Material Selection, Water Line Spacing and Mold Surface Temperature Variation
Cooling system design is important for making injection-molding tools that have short cycles and produce high quality parts. Guidelines for waterline placement vary widely and don’t satisfy the above requirements. This research used Moldflow to investigate the effects of mold material and waterline spacing on mold temperature variation.
Runner Diameter and Length Effects on Molded-In Stresses of Injection Molded Parts
Molded-in stresses are present in all injection molded parts and can be altered by the melt delivery system of a mold. The length and diameter of runners will have a direct effect on the amount of shear the material is exposed to prior to entering the part cavity and its melt conditions as it flows through the cavity. Various runner diameters and flow lengths are evaluated as to their influence on, and relationship to, the development of residual stresses in a molded part.
Rotofoamability of Polyolefin Resins
A statistical method was used to analyze experimental data and identify the best-suited polyolefin resins for rotational foam molding operations. The average cell sizes of the skinless foams that occupy the mold to its full volumetric capacity were used as the measured response.
DSC-OIT Studies of Antioxidants in Rotomolded HDPE Tanks
Differential scanning calorimetry (DSC) was used to perform oxidation induction time (OIT) studies using surface samples from three rotomolded high-density polyethylene (HDPE) tanks. Three different processing times were used to rotomold undercooked, ideal, and overcooked tanks. Graphical and statistical methods were used to study the presence and characteristics of antioxidants at the inside and outside surfaces of the tanks.
Numerical Studies of the Phase Change and Warpage under Various Process Conditions for Rotational Molding
The analysis of heat transfer in the rotational molding (rotomolding) process is a non-linear multi-dimensional problem. Using the two-dimensional (2-D) model from Lim and Ianakiev the proposed phase-change algorithm, warpage formation, thermal distribution in the warped part, cycle time prediction and other key thermal properties have been investigated. The phase-change algorithm has decreased the computational non-linearity, while maintaining the level of accuracy. Additional useful observations and predictions are also presented from the warpage simulations.
Improving the Prediction of Thermoforming Sag in Simulations through Experimental Validation of the Transition Model
Sag is a critical parameter to control in thermoforming. It is however very difficult to predict sag accurately through simulation. A series of numerical models for sag prediction are evaluated by comparison with experimental results. Some of the main process modeling parameters are identified and quantified experimentally.
A Unified Approach of Modeling Polypropylene for Thin-Gauge Solid-Phase Thermoforming Applications
A new approach has been developed for modeling hot-drawing of semi-crystalline polypropylene (PP) under conditions similar to industrial thermoforming. The proposed model encompassed components derived from a combination of concepts including Buckley et. al. [i], DSGZ [ii], G'Sell-Jonas [iii], theory of linear elasticity and multi-dimensional stresses based on a biaxiality ratio. The resulting constitutive model precisely describes the yield, strain softening followed by flow and hardening observed in hot-drawing of polypropylene.
New Capillary Viscometers for the Compounding Industry
New Capillary Viscometers, beyond offering remarkable precision, may also broaden the characterisation of polymer compounds.After a short review of the features of recent equipment, some selected examples of applications will be shown. They range from improved quality control of incoming and outgoing products, to recycling management, masterbatches characterisation, and evaluation of dispersion effects on filled materials.
The Effect of Movement during Cure of a Silicone Sealant
Movement of a building joint sealant during cure is believed to affect the fully cured" mechanical properties and the durability. A one part silicone was cured for 10 h to 168 h before the onset of physical deformation cycles. These cure times fall between the proposed RILEM TC-139 technical recommendation of 5 min and the ASTM C719 durability standard of 21 d. Apparently enough cross-linking occurred prior to testing such that neither the overall movement history of the sample nor the deformation regime shapes affected subsequent curing or mechanical properties of the sealant."
Rheological Characterization of Liquid Crystal Polymers (Xydar-300, Xydar-400 and Xydar-900) Measured in ARES Spectrometer
An in-depth experimental and theoretical study of many important factors governing the rheological properties of liquid crystal polymers, Xydars (SRT-300, SRT-400, and SRT-900) is carried out by Advanced Rheometric Expansion System (ARES Spectrometer) in the parallel plate-plate configuration over a wide range of frequency, temp and strain level in the steady shear and dynamic conditions.
Rheological Methods for the Detection of Low Levels of Long-Chain Branching in Polyolefins
Several published rheological approaches to detect the presence of long-chain branching (LCB) in commercial polyolefin resins were assessed. In particular, the suitability, feasibility, and applicability of these approaches in detecting low levels of LCB (( 0.01 LCB/1000C) were the basis of the assessment. Nine methods were evaluated using two sets of metallocene polyethylenes.
Investigation of Torque and Normal Force Responses in Double-Step Strain Histories for Branched Polyethylenes
Experiments of single-step and reversing double-step strain histories were performed on branched polyethylene and the torque and normal force responses were analyzed within the framework of the K-BKZ theory. The results validate the findings of Venerus that K-BKZ model correctly predicts the responses in the reversing histories for branched polymers.
Rheological Studies of Injection-Molded Polyolefin Foams
The rheological properties of molten LDPE and mPE foams were measured in small amplitude oscillatory shear flow. The foam samples were prepared by injection molding and the effect of injection conditions on the resultant cell structure is discussed. The linear viscoelastic behavior of the foams is well described by the Palierne emulsion model (1) without the use of any fitting parameter. It is shown that the linear viscoelastic properties of LDPE and mPE foams depend only on the properties of the polymer matrix and on the gas volume fraction.
Computer Modeling of Gas Permeation in Flexible Packages
The shelf life of oxygen and moisture sensitive products is limited by a plastic package's ability to restrict or control the permeation of small molecules through the package's walls. Mass transfer and thermal transfer equations have the same theoretical basis, and therefore heat transfer modeling programs can be adapted to model permeation. This paper models and validates this concept.
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