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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Review of Analytical Models of Anisotropy-Induce Spring Forward Effect via FEA Simulation and an Experimental Study
The increase of residual stresses during the phase change of thermoset fiber-reinforced composites causes unintended situations. A specific situation of interest is the angular distortion in curved fiber-reinforced thermoset parts, also referred to as the spring-forward effect or anisotropy induced curvature change. It has been identified that conventional analytical models deviate from experimental results when changing the part thickness. Therefore, it is of interest to study the effect of thickness variation on the final angle change. Some of these models neglect the effect of phase change in the distortion. This research relates the current scope of analytical and experimental models to predict spring-forward effect. It is necessary to extend the current models to involve the cure time-temperature-diagram (TTT) of thermoset resins.
Short Cellulose Nanofibril/Polyvinyl Alcohol Nanocomposite Fibers
Short cellulose nanofibrils (SCNF) were investigated as a reinforcement for polyvinyl alcohol (PVA) fibers. SCNF fibers were mechanically isolated from hard wood pulp after enzymatic pretreatment. Various levels of SCNF were added to PVA and gel-spun into continuous fibers. The molecular orientation of PVA was affected by a combination of wet drawing during gel spinning and post-hot-drawing at a high temperature after drying. A maximum total draw ratio of 27 was achieved with various SCNF contents investigated. The PVA crystal orientation increased when small amounts of SCNF were added, but decreased again as the SCNF content was increased above about 2 or 3%, likely due to SCNF percolation resulting in network formation that inhibited alignment. SCNF fillers were effective in improving PVA fiber tensile properties (i.e., ultimate strength and elastic modulus). Shifts in the Raman peak at ~1095 cm-1, which were associated with the C–O–C glycosidic bond of SCNF, indicated good stress transfer between the SCNF and the PVA matrix due to strong interfacial hydrogen bonding.
Using Zemac® Copolymers to Upgrade Virgin Nylon Performance
Nylon is widely used in many applications. At the 2013 ANTEC, our paper covered the results obtained with compounding primarily recycled nylon with the addition of small quantities of alternating copolymers of ethylene and maleic anhydride and specific property improvements for applications in injection molded compounds. The resulting compounds have performance that can match or exceed prime virgin nylon at 30-50% cost savings. This current paper will cover the unique chemistry of alternating copolymers of ethylene and maleic anhydride to provide several advantages for upgrading prime or virgin nylon. For example, this paper will cover results of increasing relative viscosity and the advantages that brings to various applications. Another set of results will cover the unique improvements obtained in impact-modified nylon-6 and nylon-6,6 by reducing the negative impact of traditional impact modifiers by offering synergistic set of properties.
Important Factors Impacting the Performance of Polyolefin Pipes
The use of polyolefins in pipe applications has global acceptance. As such, polyolefin based pipes are expected to maintain their properties over an extremely long service life where the polymer must withstand climatic, extractive and mechanical forces. The success of polyolefin pipes has been enabled by the development of suitable resins with a defined molecular architecture plus stabilization systems which have enabled the protection of the polymer during both melt processing and the end use application. Through the proper development of the stabilizer systems for this challenging application it is possible to protect the polymer and also extend the service life of the pipe under various environmental factors.
Detection of the Brill Transition to Elucidate Localized Thermal History in Nylon 6/6 Injection Molded Samples
The semi-crystalline microstructure of nylon 6/6 is directly related to the shear and thermal history of the material. Injection molding freezes in a set microstructure distribution through the thickness of a quenched sample. The relationship between the amorphous and crystalline domains in nylon 6/6 injection molded samples was explored using DMA, Flash DSC and FTIR analysis. The rate of injection during molding was shown to have the most significant effect on final microstructure distribution through the part thickness. Areas within the test geometries were analyzed to determine if the microstructure had formed at conditions above or below the Brill transition temperature, providing insight to the condition of localized polymer melt just prior to quenching.
Recent Advances in Glass Bubble Polymer Compounds
Glass Bubbles (Hollow Glass Microspheres), due to their unique spherical geometry and low density, provide several benefits in thermoplastic composites. They help produce lighter weight parts in order to achieve stringent fuel economy targets for automotive and aerospace manufacturers. They also provide productivity benefits through shorter cooling times, enhanced dimensional stability and less warpage – helping to reduce waste and improve throughput. In this paper, we provide solutions to achieve high impact strength in glass bubble polyolefin composites through the combination of impact modifiers and compatibilizers as well as demonstrate how GBs can be combined with supercritical foaming technology to achieve double digit weight savings with well maintained properties primarily for glass fiber filled composites.
Development of Chaotic Mixing System for MWCNT/Polymer Nanocomposites
The aim of this study was the development of a novel chaotic mixing system utilizing two cylinder rotors rotating in a sinusoidal fashion to uniformly mix multi-walled carbon nanotubes (MWCNTs) with a polymer matrix. To investigate the influences of important mixing parameters and optimize the mixing conditions, four major parameters were selected; and, MWCNTs were mixed with polystyrene to fabricate nanocomposites. Electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity results of the chaotic mixed nanocomposites suggest that the chaotic mixer has a higher potential for mixing nano particulates into thermoplastics, compared to other types of melt mixing techniques.
Chemical Foaming Agents for Gap Bridging in Contour Laser Transmission Welding
The use of chemical blowing agents (CBA) as a means of bridging gaps in contour laser transmission (LTW) welding was investigated in this study. 5% 5 Phenyl Tetrazole CBA was mixed with low density polyethylene (PE) containing 0.05% carbon black (CB). The CBA-containing PE compound was able to bridge 5-10% larger gaps at a given laser power than PE without CBA. In addition, a tool for assessing CBA degradation during LTW was developed. It involved developing a kinetic model for CBA degradation using thermal gravimetric analysis (TGA) and determining the temperature-time history during LTW using a finite element method (FEM) simulation. The kinetic model and thermal history were then combined to yield the CBA degradation as a function of time and position in the assembly.
Effect of Photo-Oxidative Degradation on Environment Stress Cracking Behavior of Polycarbonate
The combined effect of two major causes of polymer failure, photo-oxidative degradation and environment stress cracking (ESC), have been investigated in this paper. Polycarbonate (PC) injection molded specimens were aged for 168 hours at 50 °C in an ultraviolet (UV) weatherable chamber. Then the stress relaxation and tensile tests were carried out in the ethanol environment to examine ESC behavior of PC. The results show that the tensile yield stress and stress relaxation resistance of PC improve slightly due to photo-oxidative degradation, while the ethanol will accelerate the failure of undegraded PC. When the previous degraded specimens were tested under the presence of ethanol, the stress relaxation rate increases significantly and the surface cracks appear to be more intensive in comparison with other ones. This indicates that there is a synergistic effect between photooxidative degradation and environmental stress cracking for PC injection molded parts.
Investigation of Blending Methods and Phase Morphology of Poly (Lactic Acid)/ Polystyrene Blends
Biodegradable poly(lactic acid) (PLA) blend with other materials is widely demanded as an effective approach for preparation of porous materials. In the present wok, two phases blends of PLA and polystyrene (PS) were prepared by twin-screw extruder and Torque Rheometer. For the latter blending method, the effects of various conditions such as blends mass and the temperature of mixing chamber on phase morphology were explored. A bimodal distribution of porous structure was presented after extracting the PS phase from the samples prepared by two different blending methods. Different with Torque Rheometer, the blends of twinscrew extruder rarely appears reunion phenomenon; therefore, a better phase morphology can be expected. It further found that the phase morphology of blends was apparently optimized under proper post annealing conditions.
High Flow Polycarbonate Copolymers for Medical Applications
High-flow polycarbonate (PC) copolymer derived from bisphenol-A (BPA) and a specific biosourced monomer derived from castor bean oil for medical applications available in two melt flow ranges is reported. This copolymer belongs to the class of Lexan™ HFD resins known for their improved melt flow and ductility balance compared to standard polycarbonate yet with similar high optical clarity and light transmission properties. These high-flow HFD copolymers for the healthcare industry are designed to have all attributes of the Lexan™ HFD resins such as lower temperature processing capability, longer injection molding flow lengths and improved low temperature ductility versus a standard polycarbonate and ISO10993 biocompatibility. The superior flow enables molding of thinner parts with similar practical impact to standard healthcare PC.
Maximization of Hydraulic Flow in Small Flexible Polymer Tubing by Stiffness and Wall Thickness Optimization Utilizing Hardness and Glass & Carbon Nano Tubes Fillers
As medical infusion treatments become increasingly more common in the United States and across the globe, the need for better and faster fluid delivery is greater than ever. The use of advancements in polymer and polymer composites structures will provide for medical products that have increased fluid flow while maintaining required outer dimensional sizing, adequate tubing stiffness, and tubing burst resistance characteristics compared to the currently used medical tubing materials. Tubing structures of current medical tubing proprietary polyurethane structure with glass bead filler of 4% by weight (structure A), with carbon nano tube filler of 1% by weight (structure B) and a polyurethane structure with 10% increased shore durometer without fillers (structure C) were tested per ISO 10555-1 for tubing d tensile strength, stiffness, flexural fatigue resistance, vacuum lumen collapse resistance and hydraulic burst resistance. With variations of each structure having outer wall thickness of 0.010”, 0.015” and 0.020”. Structure C tubing with increased shore hardness with wall thickness of 0.020” passed all minimum requirements per ISO 10555-1. Structure C exhibited a tensile strength 13.4% less than the control group however was 52.7% stiffer and did not sustain any noticeable wear or defects during flexural fatigue testing. Structure C demonstrated tensile strengths on average 14.8% less that the control group at post flex fatigue tensile testing but showed no failures at 150 psi burst testing when applied to it for 5 seconds. Structure C with the 0.020” wall thickness is estimated to have a 43% higher flow rate capacity than the current material. Thus providing for a significantly higher rate of infusion treatment.
An Investigation of Melting and Metering Sections in a Single-Screw Extruder
For an ABS resin, a three-dimensional finite element simulation of melting and flow in the melting and metering sections of a single-screw extruder was performed using barrel rotation boundary conditions. In the simulations, the flow domain was modeled as a full three-dimensional helical channel with flight clearance. The simulation results were then compared with the corresponding results from the screw-freezing experiment. Maddock melting mechanism was observed both in experimental results and numerical predictions. However, some discrepancies existed between the numerical predictions and experimental results, which are further discussed in the paper. These discrepancies may be clarified with simulations using screw rotation boundary conditions.
Effects of Melt Rotation on Resulting Localized Material Properties throughout Injection Molded Polymeric Products
For some time now the effects of runner-based shear imbalances on melt flows during polymer molding processes have been studied and found to be problematic, even in cases where mold cavities are naturally balanced as traditionally defined. In such instances, melt rotation technology has been applied on many occasions to accommodate resulting cavity filling imbalances as well as shrinkage and warpage issues. In the present study, this approach was taken a step further with the goal of exploring affiliated product quality variations that exist as an extension of the imbalanced polymer melt flow problem. Molding trials were conducted with and without melt rotation using several types of polymers, and the resultant effects on final product physical, thermal and mechanical properties were explored. When this was done, it was found that important product quality parameters such as crystallinity and tensile modulus can vary significantly throughout conventionally molded products and be dramatically altered by the implementation of melt rotation technology. Specimens taken from product regions associated with higher melt flow shear levels exhibited higher crystallinity levels as well as higher tensile moduli. This supports the concept of melt rotation adoption for a broader range of problems extending far beyond cavity fill balancing alone.
Evaluating the Effects of Using Post Consumer Polyamide 6 (PCR-PA6) Resin for Automotive Component Application
Plastics consumption into various products has substantially grown over the years. Increasing resin prices and escalating environmental legislatives towards landfills are encouraging recycling of plastics. Recyclability of thermoplastic materials facilitates innovative application established on their residual contents. The plastic scrap thus is classified into predominant categories as postindustrial resin (PIR) and postconsumer resin (PCR). Postconsumer resin (PCR) is recovered from recycled products such as disposable packaging containers, bottles, and commodities in landfills. Discarded carpets are becoming a compelling source of PCR- Nylon resins. This paper evaluates the use of PCR-PA6 resin for automotive component application. The lifetime performance of these formulations was estimated through prolonged heat aging and testing at various intervals.
Chemical Identification and TGA Flynn-Wall Thermal Service Evaluation of Three Commercial Jacketed Ignition Cables
Three commercial jacketed ignition cables were obtained and the inner and jacket insulation materials identified by FTIR analysis. The cables were found to be made of silicone, chlorinated polyethylene, and PVC with both the inner and jacket made from the same polymer base. Flynn-Wall analysis was performed using TGA to calculate activation energies for 10% mass loss. These values, in conjunction with actual TGA measurements of the time for 10% mass loss at 300 and 400°C, enabled estimation of cable service lifetimes at 100 and 170°C service temperatures.
Micromanufacturing of Consistent Micro Petri Dish Biointerfaces to Guide Stem Cell Mechanotransduction
Microfeatured petri dish inserts containing consistent microtopography were manufactured for the intentional control of stem cell shape and function. Polyolefin plates were micro-injection molded through utilization of an actively heated assembly containing a negatively featured silicon inlay. Surface properties were characterized through microscopy and water contact angle (WCA) analysis. Human Mesenchymal Stem Cells (hMSCs) were grown on microfeatured and flat substrates. Microtopography dramatically altered surface hydrophobicity and hMSC morphology. Micro-injection molding offers unique industrially relevant manufacturing possibilities for use in the biomedical field.
Effect of Moisture Exposure on Scratch Resistance of Polymers
Effects of moisture exposure on scratch performance of polymethylmathacrylate (PMMA) and polypropylene (PP) were investigated. Three different grades of PMMA and PP with varying levels of polarity and molecular weight were chosen and their scratch resistance compared in both dry and moist conditions. Linear increasing load scratch tests were performed according to ASTM D7027/ISO 19252 standards. Results indicate a drop in scratch resistance with initial exposure to moisture in all three PMMA systems. In the two highly polar PMMA systems, the scratch resistance recovers to that of the dry condition after exposure to moisture while PP scratch resistance remains unchanged. It is proposed that the moisture absorbed initially acts as a plasticizer causing weakening of the surface for PMMA. In the case of more polar systems this moisture absorption continues until saturation where water molecules cluster and impart a degree of lubrication and consequently improve scratch resistance.
A Novel Method to Produce Lightweight Microcellular Injection Molded Parts with Improved Ductility
A novel method of improving the ductility of injection molded plastic parts has been developed. By applying either gas-laden pellet technology or microcellular injection molding to polymer blends or composites of proper material formulations, the ductility and toughness of the molded foam parts can be significantly improved compared to those of solid parts. The key is to achieve a microcellular structure with a sub-micro scale immiscible secondary phase. Upon tensile loading, cavitation of the secondary phase facilitates the interconnection of microcellular voids to form channels such that the stretched component becomes a bundle of fibrils. This change in structure turns the fracture mechanism from crack propagation across the matrix into shear yielding of a bundle of fibrils in the loading direction. Compared with other toughening methods, this method achieved a more significant improvement in ductility and toughness with reduced material consumption and lighter part weights.
Comparison of High-Solvating and General Purpose Plasticizers Using PVC Dry Blending Dynamics
High solvating plasticizers have recently been of interest in industry in regards to PVC melt compounding. Dibenzoate plasticizers comprise a family of high solvating plasticizers that have been known for the beneficial effects they impart to vinyl. In the pursuit of improving dry blend characteristics and conserving manufacturing energy usage, a study was conducted to determine the effects of dibenzoate plasticizers both alone and in blends with general purpose plasticizers. The dry blends were analyzed using a torque rheometer under both isothermal and constant heat ramp conditions. Experiments with plasticizers on a PVC resin have shown dibenzoates to improve processing time over the use of general purpose plasticizers alone, and plasticizer blend experiments have given insight into the utility of incremental benzoate usage. Further experimentation indicated that pressure application to dry blends gives further insight into the level of plasticizer incorporation.
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