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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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.
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."
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