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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Multilayer Films Using PP/PPgAA Blends
Blends of polypropylene (PP) with 0 to 100% wt of Polypropylene grafted with Acrylic Acid (PP-gAA) were prepared by melt mixing and then coextruded as external layers with a central layer of nylon-6 on three layer coextruded flat films The effect of the modified polymer content and its molecular weight on interfacial adhesion between PP and nylon was determined by T-peel strength measurements. The effect of melt temperature and contact time during coextrusion on peel strength was determined. The observed increase on T-peel strength of the films when using 10% and higher levels of functionalized PP in the blend, suggest good interfacial adhesion between layers. Besides PPgAA content, its molecular weight has a notorious effect on interfacial adhesion between PP and nylon-6 (PA6).
Near-Infrared Spectroscopic Product and Process Control
The main applications of near-infrared spectroscopy relating to polymers are quality control, monitoring of textile fibers, remote identification/classification of polymeric materials (recycling), monitoring of polymer melts for additive and/or (co)polymer composition, and polymerization monitoring (of polyolefins, epoxies, nitrogen-containing polymers). Diffuse reflectance and transmission, transreflectance and reflectance modes are being used. Examples of the aforementioned applicational areas will be given with the main emphasis on the on-line (multicomponent) additive analysis in the polymer melt by means of near-infrared spectroscopy.
Extruder Analysis Utilizing a Transparent Extruder and Simulation Software
Experiments using a glass window extruder are presented. These provide direct observation of the different melting behavior among various polymers. Simulations performed using commercially available software showed good correlation with the observations. The data obtained provides valuable insight into the melting behavior which, can be used to evaluate and ultimately improve the capabilities of simulation software as well as screw designs.
How to Add Value and Solve Mold Problems - With Steel
Mold designers and mold builders know many different ways to solve mold problems.. Yet a surprising number of our colleagues have not yet used the wide variety of proven mold steel on offer in to-day's market place. This paper reviews the range of available grades of steel; it cites examples of mold problems that have been solved by selecting better and more appropriate alloys; it lists the worldwide availability of innovative mold steels, and finally, it shows that better steel adds value to a mold at very modest cost.
Melt Processed Polymer-Clay Nanocomposites: Properties and Applications
The melt compounding route is a powerful approach in the preparation of polymer-clay nanocomposites as existing technologies can be utilized and easily scaled to commercial quantities. Polymer-clay nanocomposites have been developed via melt compounding. Dramatic increases are exhibited in heat distortion, stiffness, and barrier properties compared to the neat resin. Other benefits include low specific gravity, processing ease, surface appearance, etc.
Polymer Rheology-Challenges for the 21st Century
Rheological data are used in the plastics industry for polymer characterization, quality control, process control, and process modeling. In each of these fields, there remain significant barriers to progress. The challenges in polymer characterization are to develop experimental techniques for the rapid and precise measurement of linear viscoelastic properties and for evaluating the response of a melt to extensional deformations. A powerful aid in keeping a manufacturing process under statistical control is the use of an on-line rheometer as a process sensor for automatic control. A remaining challenge is the development of an in-line melt rheometer that would eliminate the need for gear pumps and reduce the time delay resulting from the transit of melt from the sampling point to the rheometer. While computational fluid dynamics has been applied with success to the simulation of several melt forming processes, major problems remain when melt elasticity plays an important role. In addition, present simulation techniques do not incorporate models for gross melt fracture, sharkskin and wall slip.
Influence of the Percentage of Gel Content on Impact Strength of Cross-Linked Rotationally Moulded Parts
Crosslinking of polyethylene changes the chemical structure of the original thermoplastic polymer. The initial thermoplastic material consists of linear polymer chains and this is transformed into a polymer network with rubber elastic properties. Radical activity during peroxide or radiation crosslinking leads to polymer chain scission, formation of short chain fragments and crosslinking. The resulting polymer network can, therefore, be described as a fairly homogeneous randomised statistical alkyl-chain network. Average molecular weights between crosslinks, gel content ( crosslink density ) and the solvent swelling factor are the main parameters for characterising the structure . A three-dimensional network is thus formed which improves many properties such as heat deformation, abrasion resistance, viscous deformation, chemical resistance, and stress cracking resistance. Impact and tensile strength are also increased, shrinkage is decreased and low temperature properties are improved .
The Effect of Monomer Structure on the Adhesive Properties of Thermally Reversible Isocyanate Polymers
The benefits of thermally reversible polymers derives from their structure; they dissociate into much lower molecular weight components when heated above a critical temperature and reform into a polymer when cooled below that temperature. This allows them to flow at a modestly elevated temperature, while exhibiting good strength, adhesion, solvent resistance at lower temperatures. Such polymers can be used as hot melt adhesives that combine the best features of both thermoplastics and thermosets. They can be reheated repeatedly, while producing a crosslinked network at ambient conditions. The properties of reversible isocyanate polymers depend on the structure of the monomers incorporated into the polymer backbone. This paper summarizes the influence of several polyester based monomers on the adhesive characteristics of the resulting polymer.
Influence of Chemical Composition on the Rheological Behaviour of Condensation Reaction Resins
A study of Melamine Formaldehyde (MF) resins of different molar ratios was undertaken to asses their chemorheological and thermorheological properties. MF resins polymerise via a polycondensation reaction involving condesation of up to 10 wt. % of water on cure. This results in rapid and extensive foaming of the resin when cured under atmospheric pressure. To accomplish the study, both foaming dynamics and bulk properties of MF were analysed; the former yielded results on the influence of initial moisture content on reaction rate and on curing kinetics including gel and vitrification times, while the latter yielded true G' and G' values and consistent glass transition temperature readings. The different molar ratios were found to affect curing kinetics in terms of large differences in gelation and vitrification times, and to yield high glass transition temperatures.
New Compositions of Matter from the Modular Disk Coextrusion Die
A new composition of matter never made before has been created from common thermoplastics. Coextruded blown films were made using two thermoplastic materials in sixteen alternating layers. Each of the sixteen layers was progressively varied in thickness in a controlled manner so that the thinner layers on outside of the bubble gradually progressed into thicker layers on the inside of the bubble. Refractive index differences between certain plastic materials can now be studied and the effect of films having progressively varied layer thickness can be compared to films having essentially uniform layer thickness.
A Study of Surface Haze Formation in Polypropylene/Acrylic Alloys
Haze is a cosmetic defect that occasionally appears on injection molded part surfaces. This defect is especially noticeable in dark colored, high gloss parts. A study was performed to identify and understand the underlying causes of surface haze formation in unfilled PP/PMMA alloys. Four different Polypropylene resins with varying amounts of PMMA were evaluated. The formation of haze was found to correlate with the amount of PMMA included in the formulation and the melt elasticity as indicated by tan ? at low frequency.
Dependence of Draw Resonance on Extensional Rheological Properties of LLDPE
The effect of extensional rheology on draw resonance during fiber melt spinning is studied. Two linear low-density polyethylenes(PE's) synthesized using metallocene catalysts are compared. The LLDPE's appear to have different amounts of long chain branching, resulting in differences in extensional rheology. However, both materials behave almost identically in shear. During melt spinning, the PE's exhibit different critical draw ratios at which the onset of draw resonance occurs. Furthermore, the period of resonance changes with increasing draw down ratio for both PE's.
Light Stabilization for Black and White Glass-Filled Nylon-6
Light stabilization of polyamides for automotive applications remains a challenge. In this paper various stabilization systems (hindered amine light stabilizer, antioxidant, phosphite) were evaluated in black and white glass-filled nylon-6. The properties being examined were color change and gloss retention of injection molded plaques during exposure in a xenon arc weatherometer under exterior automotive conditions per SAE J1960 and interior automotive conditions per SAE J1885. Light stabilization systems meeting the interior automotive requirements were identified.
Assessment of a New, Completely Controlled, IR Welding System Using Statistically Designed Experiments
Infrared welding has been used successfully for many years for joining plastics pipes in industrial applications. In order to increase the productivity of this technique, a new generation of machines has been developed that can reduce the weld cycle times by up to 45% compared with standard IR machines. This paper describes how a statistically designed experimental programme has been used to assess the performance of these new IR welding machine in the most cost-effective manner. Results have shown that low temperature welding factors achieved are within 4% of the values obtained on standard IR machines.
Continuous Anionic Polymerization of Polyamide-Based Thermoplastic Elastomer in a Counter-Rotating Twin Screw Extruder: Polyesteramide Triblock Copolymer
Polyamide 6, polyesteramide triblock and polyetheresteramide pentablock copolymers were polymerized in a modular intermeshing counter-rotating twin screw extruder. Polyesteramide triblock and polyetheresteramide pentablock copolymers are polyamide-based thermoplastic elastomers (TPE) and had not been previously polymerized in a twin screw extruder. Characterization studies including thermal analysis, viscosity measurements, and solvent extraction clearly demonstrated that the new copolymers have two separated domains arising from the different block segments. These polymers were also melt-spun into oriented filaments from the die at the exit to the twin screw extruder.
The Modified Imbedded Disc Retraction Method for Measurement of Interfacial Tension in Polymer Melts
The imbedded disc retraction method is used to estimate interfacial tension in LLDPE/PS system with PS as the imbedded disc. The Newtonian model of Rundqvist et al.  for the imbedded disc retraction is modified to include elastic effects and both are compared to experiments. The modified model is derived assuming uniaxial extension and the upper convected Maxwell model. The mean values of interfacial tension at 190, 200 and 210 °C are found to be 6.8±0.7, 3.9±0.3 and 3.7±0.2 mN/m respectively. A method of estimating whether elastic effects will significantly affect the estimated interfacial tension value during retraction for the given polymer pair is provided.
Development of Novel Applications of Crosslinked Elastomer Scrap in Thermoplastics
Materials ranging from impact-modified thermoplastics to thermoplastic elastomers (TPE) can be obtained from blends of recycled ethylene-propylene-diene rubber (EPDM) containing carbon black with poly(propylene) (PP) by varying the ratio of components in the blend. This study focused on developing TPE materials from PP and recycled ground rubber. The effect of rubber particle size, melt flow index (MFI) for the PP, and weight percent of the constituent fractions on the physical properties of the resultant blends was quantified. A design of experiments based on the processing conditions and variables was performed to determine the optimum processing conditions. Compatibilization techniques were used to improve the quality of the scrap rubber/plastic blends in response to the structural requirements of several potential applications. The cost factors for scale-up to manufacturing operations were also considered. It was found that the MFI of PP is a major factor controlling the mechanical properties of the blends. Through proper selection of the components and compatibilization techniques, blends were found to be tailorable to specific applications.
Use of Infrared Dyes for Transmission Laser Welding of Plastics
A technique has been developed for transmission laser welding plastics with infrared dye, creating a joint almost invisible to the human eye. In typical applications for laser welding of plastics, carbon black would be used as the absorbing medium for the laser energy. This new approach enables two similar clear (or coloured) plastics to be joined with a minimal mark weld line. A number of dyes have been selected and assessed in terms of strength of light absorption at 1064nm wavelength with an Nd:YAG laser, as well as their visible light absorption. Lap welds have been made in clear PMMA using the infrared dye mixed into methyl methacrylate film as an absorbing medium at the interface between the plastic sheets. The selection of the dyes and processing methods is discussed for the new technique.
An On-Line Measurement Scheme of Melt-Front-Area during Injection Filling via a Soft-Sensor Implementation
A constant melt-front velocity during the filling of an injection mold cavity is commonly believed to bring about more uniform part quality. To maintain a constant melt-front velocity, injection velocity can be set proportional to the melt-front-area which is, however, not directly measurable. An on-line soft-sensor scheme is developed through neural network to correlate on-line measurable process variables to the melt-front-area. Simulations indicate that the soft-sensor developed for the melt-front-area works reasonably well for some selected molds.
Size and Confinement Effects on the Glass Transition
Since the first measurements of the reduction of the glass transition of small molecule liquids in nanometer pores, there has been an increasing number of studies of the effects of size and confinement on the glass transition of both small molecules and polymers. The measurements coming from different groups often give apparently conflicting results. This paper surveys the state of the field and provides insights into possible reasons for the apparent discrepancies that suggest paths for further investigation.
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