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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Properties and Applications of Sandwich Panels Based on PET Foams
PET foams of variable densities, (1 g/cc to 0.2 g/cc), based on virgin and recycled material were produced by extrusion with physical or chemical blowing agents and evaluated as low density core in sandwich panels having M/F impregnated paper or flame retardant mineral reinforced PET as skin faces. Flexural and shear stiffness of the laminates were determined by variable span three point bending. Panels were also tested for thermal and moisture stability and compared with competitive sandwich constructions based on PVC foam, flake board, particleboard and plywood. Potential applications of the PET based laminates in building and construction are presented.
On the Experimental Investigation of High-Frequency Dielectric Sealing of PVC
This feasibility study deals with the investigation of welding Polyvinyl Chloride (PVC) sheets of different formulations, using high dielectric frequency technique. The experimental work consisted of PVC formulation (rigid sheet), mold design (new products), experimental design to quantify the effect of process parameters, mechanical characterization (tensile, peel testing) of the weld area, and process optimization. Rigid PVC formulation was selected based on two primary mechanical properties, tear resistance and shear modulus. The weld was well achieved within the studied range of parameters, while the processing conditions were experimentally optimized. Finally, new office items were successfully produced as a result of the design of new molds combined with new process layout (sheets).
Comprehensive Study of a New Extensional Flow Mixer
A patented Extensional Flow Mixer (EFM) (1) has been developed in which plastics is hydrodynamically mixed by flowing through a series of convergent and divergent regions so that very efficient dispersive and distributive mixing can be achieved. The EFM can be attached to any plastics pumping machine, such as single-screw and twin-screw extruders, for injection molding, blow molding, extrusion, and compounding. Comprehensive laboratory and industrial tests have been conducted especially for film applications, which indicate the mixing of a single-screw extruder (SSE) with an EFM can outperform that of a twin-screw extruder (TSE) in certain aspects. Results of gel elimination, strength enhancement and morphology changes are presented.
Pressure-Volume-Temperature Dependence in Polyvinylidene Fluoride and Polyvinylidene Fluoride-Hexafluoropropylene Copolymers
The relationship between pressure, volume and temperature (PVT) of polyvinylidene fluoride homopolymers (PVDF) and polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) copolymers was determined in the pressure range of 200 to 1200 bars and in the temperature range of 40°C to 230°C. Differential scanning calorimetry (DSC) analysis was performed on each resin to simulate the cooling process during the PVT experiments and to determine the crystallization and melting temperatures at atmospheric pressures. The TAIT state equation describing the dependence of specific volume on the zero-pressure volume (V0,T), pressure and temperature has been used to predict the specific volume of PVDF and PVDF-HFP copolymers.
On the Prediction of Crystallinity Distribution in Injection Molded Semi-Crystalline Thermoplastics
Injection molded semi-crystalline thermoplastic parts show variable morphologies across their thickness. Process parameters such as injection speed, mold temperature, and melt temperature, play important role in forming these morphologies. The heat and shear history has great effect on the crystallization process of the semi-crystalline plastics. In this study, different available crystallization models were used to predict the crystallinity distribution, and capabilities of the models compared. Based on the results from these models, a more realistic model, which considers stress relaxation during the crystallization process, is proposed.
Properties of an Oil Resistant TPV
A TPV based on a dynamically vulcanized blend of epoxidized natural rubber and polypropylene is described. Morphological and rheological properties are briefly reviewed. Basic physical properties compare well with those of other TPVs whilst oil resistance is comparable to that of a well-compounded NBR vulcanizate (34% acrylonitrile). Excellent heat resistance with good retention of properties on ageing for extended periods at 100° and 150°C is also demonstrated as is good weathering and ozone resistance.
Rheology of TPV’S
The rheological properties of various TPV's have been studied in shear flow using dynamical mechanical spectrometry, capillary rheometry, transient stress buildup and shear creep. The TPV's which are commercial dynamically vulcanised PP/EPDM blends show a typical rheological behaviour with an apparent yield stress value at low shear rates, a shear-thinning viscosity at high(er) shear rates and, moreover, they do not obey the Cox-Merz law. This study revealed that the observed phenomena could be explained by the role of the three main components: PP, EPDM and oil.
Effect of Polyolefin Structure on Grafting of Maleic Anhydride
In this study the effect of polyolefin composition, i.e. ethene/propene ratio, on MA grafting and branching/crosslinking or degradation was investigated both in the melt and solution. The MA grafting content for PE and EPM was similar, but low for polymers with a high propene content. An increase of the ethene content results in a transition from degradation to branching/crosslinking.
Factors Affecting Adhesion of Tie Layers between Polypropylene and Polyamides
Adhesion properties were determined on five-layer coextruded cast films. With a few exceptions, the cap layers consisted of polypropylene, the tie layers consisted of blends of polypropylene and maleic anhydride-grafted polypropylene, and the center layer consisted of various polyamides. Up to a point, the adhesion increased as the overall film thickness and the level of maleic anhydride-grafted polypropylene were increased. The molecular weight of the grafted resin had a small effect on adhesion. Homopolymer diluent outperformed random copolymer diluents. Adhesion did not vary much when different types of polyamides were used as the center layer, but each exhibited much greater adhesion than an ethylene-vinyl alcohol center layer.
Investigations on Stretched Block Copolymers of Poly(butylene terephthalate) and Poly(tetramethylene oxide)
The changes in phase structure under uniaxial deformation of block copolymers of Poly(butylene terephthalate) (PBT) and Poly(tetramethylene oxide) (PTMO) have been investigated using 13C solid state NMR spectroscopy and infrared spectroscopy on in-situ stretched samples. The study was focused on the strain-induced crystallization of the PTMO. It became obvious that a minimum stress level in the material is necessary for the strain-induced PTMO crystals to form and to be stable at room temperature. The amount of crystalline PTMO is dependent on the stress level and on the temperature. We also found, that the PTMO crystallization is favored by a large PTMO block length and a large PTMO content.
Microfibrillar Composites with Ultimate Properties
In the past decade, numerous novel polymeric products were introduced, including polymer blends, for various applications in the automotive and electronic industry. Up to now a homopolymer as such has to be reinforced to meet the high demands on stiffness and strength in engineering applications and glass fibres were the major reinforcing element used in these materials. Microfibrillar reinforced composites based on polycondensates are new polymeric construction materials with ultimate properties. Such a composite has specific economical and ecological advantages since, upon recycling, a polymer blend is obtained which can be re-used to make again polymeric materials with specific properties.
Residence Distribution Models for Twin Screw Extruder
Transformation of the residence time distribution (RTD) to give both the residence volume distribution (RVD) and the residence revolution distribution (RRD) yields new physical insights into the extrusion process. These new tools motivate the development of a simple residence distribution model which characterizes the partially filled and fully filled screw sections and is capable of distinguishing between screw configurations and operating conditions. A least square error fit method is used to identify the parameters of the RTD model and it is indicated that the model function is appropriate to describe the RTD experimental data. The model for the RTD is validated on the analysis of data collected from the extrusion of polyethylene on a 30 mm Krupp Werner and Pfleiderer (W&P) Co-rotating twin screw extruder.
Mean Residence Time Characterization in Co-Rotating Twin Screw Extruder: Screw Configuration Comparison
Many industrial processes are described by residence time distribution functions (RTD). Experiments were carried out on a 30mm Krupp Werner and Pfleiderer co-rotating twin-screw extruder (CoTSE) equipped with reflectance optical probes to study the residence functions of different screw geometries to distinguish them. Theory described by Gao, Bigio, et al, shows that the mean number of screw rotations can be found from these RTD functions from the product of the screw speed and mean residence time. This equipment was used to show that the mean number of screw rotations is proportional to the inverse of the specific throughput. In addition, different geometries exhibit different functional relationships between the mean number of screw rotations and the inverse of the specific throughput.
Fundamentals of Polymer Process Control
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and the manufacturing systems continue to produce defective components during production. This paper provides an overview strategies in polymer process control, and discusses some of the difficulties posed by the complex and distributed processes. Objectives for 'intelligent' process control are presented. Finally, the potential benefits of integating product and process design are demonstrated.
An Overview of Optical Brighteners for Copolyester Resin Extrusion Paper Coating Applications
Several topics will be covered in the Take Home Information" to aid the reader in a better understanding of optical brighteners use in extrusion coating applications. They include: • What is an optical brightener? • What is the mechanism? • How to formulate with optical brighteners in an extrusion coating grade copolyester resin. "
On-Line Monitoring of Free Radical Grafting in a Model Twin Screw Extruder
The on-line monitoring system of Raman spectroscopy was developed to monitor the grafting identification and level of grafting of glycidyl methacrylate (GMA) onto low density polyethylene (LDPE). The reactive extrusion and melting behavior of GMA and LDPE was monitored by a fiber optic probe through the glass windows mounted on the model non-intermeshing counter rotating twin screw extruder. Monitoring concentration of GMA along the screw extruder was carried out to determine the reaction level.
Sorption Properties of PAN/Chitosan Composite Fiber
Composite fiber of PAN and chitosan was obtained by hydration-melt spinning process. The fiber showed a fibrillar structure which can be converted easily into pulp-like structure by beating. PAN/chitosan pulp showed much higher amount of acid dye uptake than chitosan powder or activated carbon which is used for the color removal from the waste water of dyeing industry. This better sorption for the composite fiber is considered to result from the relatively large surface area due to its pulp-like shape.
Epoxy + Montmorillonite Nanocomposite: Dynamic Mechanical Analysis
Polymer nanocomposites are of growing interest. Epoxy resins are an important matrix resin for aerospace and electronic composites. Increasing the mechanical properties of epoxy resins is vital to increasing their long term reliability. Here we investigate the addition of a montmorillonite layered silicate to an epoxy resin using dynamic mechanical analysis. The effect of montmorillonite on the glass transition and beta transition are examined. Frequency - temperature sweeps betweeen 133K to 393K at 0.0159 to 159 Hz were recorded. Master curves were determined graphically and the shift factors analyzed for changes in activation energy and WLF constants. A narrow range of reinforcement concentration was identified where desirable impact properties might be found.
Isolating the Effect of Reaction on the Phase Inversion of Model PA/PS Blends
This paper aims to distinguish the effect of reaction on morphology development during polymer blending from other confounding parameters, particularly the rheological differences between the reactive and nonreactive components. Many works have focused on components that are rheologically matched at the processing temperature. However, based on previous results that have shown the importance of the melting regime in morphology development, it is crucial that the components be rheologically matched throughout the experimental temperature range. In this work, we use a model addition protocol to limit the morphology development to a temperature range where the reactive and nonreactive polystyrenes exhibit an excellent rheological match. The interfacial reaction was found to accelerate the pace of initial morphology development, where sheets are pulled off the solid pellet core during melting. Phase inversion began earlier but finished later in the nonreactive blend.
The Effect of Preform and Bottle Design Characteristics on the Performance of PET Water Bottles
With the increased demand for bottled water worldwide, PET packaging has had to adapt to meet consumers' demands and bottlers' needs. During the development of a new water bottle, potentially contradictory considerations must be addressed. In this study of a 0.5L water bottle, the effect of bottle design, preform design, and resin on bottle performance and economics was explored. A bottle with an arch shoulder and deep ribs or belts" using a high stretch high IV preform had a good combination of mechanical properties. The aesthetic impact of the bottle design and the longer cycle time for injection molding the preform might be the drawbacks of this choice."
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