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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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.
Improvements to Laser Processing of Thin Polymer Films - Using Non-Standard Novel Laser Wavelengths
Highly reliable high power carbon dioxide lasers are being increasingly employed in the converting industry. New laser sources with different wavelengths are available to allow more controlled laser cutting and perforating processes. These process advantages are thought to be due to enhanced absorption of certain thermoplastics at these shorter wavelengths and this paper investigates these.
Modifying LDPE for Improved Adhesion to Aluminum Foil
A modifier was developed to enhance the adhesion of LDPE to aluminum foil in extrusion coating/lamination. Statistically designed experiments identified four factors that most influence the adhesion: % of modifier blended with LDPE, temperature, thickness and time in the air gap. The results show that the modifier offers several benefits to flexible packaging applications, including greater consistency in meeting adhesion specifications and the ability to run at faster line speed or at lower temperatures without sacrificing adhesion. These are demonstrated using statistical modeling and analysis.
Force Measurement during Vibration Welding of Nylon 66
An experimental technique for measuring the shear forces generated during vibration welding is presented. It involves the use of piezoelectric shear force transducers mounted under the fixture on the lifting table. Using unreinforced and 30% glass fibre reinforced nylon 66 T-welds, the force was measured in real time under a range of weld pressures and weld amplitudes. The shear stress amplitude is observed to depend strongly on the type of material, the welding parameters and the specific phase of the vibration welding process.
Automotive Plastic Fuel Tank Systems
The manufacturing of Plastic Fuel Systems is an ever changing and technology driven field. The field is influenced by governmental emission standards that are becoming tougher to meet with plastic fuel tanks. Several new technologies have been developed to accommodate the environmental legislative changes.
Through-Transmission Laser Welding of Nylon - Breaking the Moisture Barrier
For through-transmission laser welding (TTLW), basic studies include optical and mechanical data of nylon at dry-as molded conditions". Recent developments have been oriented toward the influence of accumulated moisture on optical and mechanical characterization of laser welded nylon 6. Results from this report provide supporting data that moisture in nylon is not a barrier for laser technology and the mechanical performance of welded parts."
Design Flexibility in Waveguides and Lightpipes for TTIr Plastics Welding
Waveguides and lightpipes can be used for simultaneous TTIr plastics welding. There are various new improvements in the waveguide and lightpipe technology, including optical horned, tapered, lensed, side looking, and part incorporating waveguides and lightpipes, that enhance weldability, weld quality, and cycle times.
Practical Joint Designs for Laser Welding of Thermoplastics
In recent years, much work has been done on laser welding of thermoplastics. The process has been well characterized through the use of test plaques. This paper discusses practical considerations of laser joint design, including an examination of the advantages and disadvantages of collapse-type joints and non-collapse or contained welding joints. Issues such as reflection and low transmissibility and low absorption materials are discussed from the part designer's point of view.
Industrial Applications for Laser Welding of Plastics
The possibility for laser welding of plastics has been researched over the past years with the results of the technology going in various directions. The Approach of laser welding plastic components in Industrial applications utilizing the Quasi-simultaneous laser welding (QSLS) has been quite successful.
In-Process Temperature Measurement in Extrusion Using Continuous Wave Ultrasound
In this work a continuous wave ultrasound system was investigated for application to in process temperature measurement for extrusion. Work to date includes preliminary studies of the feasibility and initial laboratory based tests showing sensitivity of the signal to temperature changes.
In-Process Viscosity Monitoring for Extrusion Control
Melt viscosity during extrusion is a strong indicator of product quality, hence measurement of this variable in real-time is a key target for process control. The suitability of different methods of viscosity monitoring for application in a control scheme is assessed in this work. The responses of in-line and on-line rheometers to steady state and dynamic conditions are investigated. Also, the ability to infer viscosity by monitoring of other process variables is considered.
Injection Moulding Process Assessment by Energy Monitoring
The potential for process and production measurements on injection moulding machines using non-invasive, energy measurements is examined. High-speed energy measurements are shown to provide similar information to more traditional process measurements. Energy measurements may also provide additional information for use in process troubleshooting. It is concluded that energy monitoring can provide a fingerprint" of a process and hence can be used for product quality control."
Ultrasonic Monitoring of Gas assisted Injection Moulding (GAIM)
In-process measurements using ultrasonic technology provide a powerful yet non-invasive insight into material conditions. In the injection-moulding cavity, information on filling and solidification detection can be measured. The transit time of longitudinal ultrasonic waves through HDPE has been measured during gas assisted injection moulding (GAIM), indicating the ability of this technology to assess part wall thickness in-situ before mould opening.
Effect of Nano-Size Clay Particles on the Flexural Properties of Syntactic Foams
Effect of incorporation of nano-size clay particles on the flexural properties of syntactic foams is studied in the present work. Nanoclay particles are incorporated in syntactic foams in the volume fraction of 2 and 5%. Total volume fraction of glass microballoons and nanoclay is maintained at 0.65. Three-point bending tests are carried out in accordance to the standards ASTM D790-02. Flexural strength is found to increase with nanoclay content.
Measurement of Sintering Characteristics of Clay-Reinforced Polyamide 6 Nanocomposite
Sintering characteristics of clay nanoparticle/polyamide 6 composite were studied for applications in Rapid Prototyping and Manufacturing. Sintered nanocomposite powders showed lower final density than the standard polymer due to increased resistance to low shear rate deformation. Because of this flow resistance, rapid prototyping processing parameters such as part-bed temperature and laser power must be adjusted.
The Characteristics of PA-6/Clay and PA-66/Clay Nanocomposites
Nanocomposites based on polyamide 66 (PA-66)/clay and polyamide 6 (PA-6)/clay were prepared using a twin-screw extruder. The nanocomposites were characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetric (DSC), optical microscopy and tensile testing. Effects of processing condition and clay modifier were also studied. The results show that mixing, shearing elements and higher residence time in the twin-screw extruder are effective factors in enhancing exfoliation. The characteristics of the two types of nanocomposites will be compared.
Prediction of Residual Strength of Laminated Composites Subjected to Low Velocity Impact
Barely visible impact damage in composite structures is difficult to detect. The predominant failure mechanism is delamination, which is easily detected by C-scan. Using pixel data from C-scan image, coupled with acoustic emission amplitude distribution data from compression after impact testing, and applying it to a back propagation neural network, correlations on ultimate strength can be made with great accuracy. This paper demonstrates the ability to predict the ultimate compressive strengths of composite structures using this approach.
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