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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COF of LLDPE Films as a Function of Erucamide Surface Concentration
The surface of a polymer film can be modified by allowing additives within the film to diffuse to the surface and accumulate there. Some of the most commonly used surface-property modifiers are slip, antifogging and antistatic agents. Erucamide is a slip agent widely used to reduce coefficient of friction (COF) of polymer films. This research focused on quantifying the relationship between erucamide surface concentration and COF of LLDPE films. The surface concentration was measured using surface washing, and results showed that there were significant COF changes in the surface-concentration range of 0 to 0.5 ?g/cm2.
Comparison of Techniques to Measure Additive Diffusivity in Polymer Films
The surfaces of a polymer film can be modified by allowing additives within the film to diffuse to the surfaces and accumulate there. To model the diffusion/accumulation process, it is necessary to accurately measure the diffusion coefficient of the additive in the polymer. We have attempted to characterize the diffusivity of erucamide in LLDPE through several means: mass sorption (diffusion in") and surface washing and ATR-FTIR ("diffusion out"). Experiments demonstrate that surface washing can provide inconsistent results. Mass sorption and ATR-FTIR provide comparable results although emphasis is placed on the ATR-FTIR technique because the migration process more closely mimics the behavior of commercial films."
Study of Polypropylene Degradation in a Co-Rotating Twin Screw Extruder
Screw design, injection site and operating conditions are critical parameters which influence peroxide injection efficiency during PP vis-breaking. A visual study in a clear barrel extruder was performed with water and corn-syrup to simulate the mixing of a low viscosity ratio system. Liquid injection of peroxide into PP was then performed in a 30 mm COTSE and compared to the normal pre-mixed peroxide method. Operating conditions were found to greatly influence degradation by shear and injection efficiency.
Evolution of the Anisotropic Structure of Poly(phenylene vinylene) Films with Stretching
The evolution of the anisotropic structure of PPV films with stretching was studied by three characterization techniques: three dimensional refractive indices using waveguide, infrared dichroism and flatplate x-ray photography. The results show that the cast PPV film without stretching has a highly planar structure. One way stretching converts the film to a uniaxial structure.
Extrusion Blow Molding Process-Development and Optimization
This paper presents the application of CAE tools for a Blow Molding process. A description of the underlying theory is provided. The predicted thickness distribution for an example part is shown to have a good correlation with experimental measurements. The approach to parison thickness optimization is also demonstrated.
The stress development during polymer processing of semi-crystalline polymers can cause stress-induced crystallization and changes in the crystallization kinetics. The integration of orientation entropy changes calculated by non-linear viscoelastic constitutive equations in crystallization thermodynamics gives us a proper physical model to describe the crystallization behavior in oriented polymer melts. Based on the model a new economic characterization procedure for stress-induced crystallization is put into application. The new model is used to simulate the stress-induced crystallization during the injection molding of isotactic polypropylenes. The results are compared with experimental data.
Interfacial Adhesion in Thermoplastic/LCP Blends
Knowledge about interfacial adhesion in thermoplastic/LCP blends is important for manufacturing self-reinforced composites with improved performance. Thus, in the present study, interfacial shear strength between different LCPs and thermoplastics was measured by using fiber pullout method. The LCPs employed were Vectra A - 950, Vectra B - 900, Ultrax KR - 4002 and Ultrax KR - 4003. The thermoplastics included were high density polyethylene, polypropylene, polycarbonate, polyphenylene oxide/polystyrene alloy, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyetherimide and copolyester. Based on these measurements, the similarities and differences in interfacial behavior of various pairs have been found. In addition, ranking of various pairs of thermoplastic/LCP blends has been made concerning their interfacial shear strengths.
Rheology of Highly Interactive Polymer-Filler Mixtures
The dynamic properties of polystyrene (PS)/silica mixtures of various concentrations were investigated as a function of frequency and strain along with the flow curves. An abrupt change in the viscoelastic properties is noticed above 1% volume concentration. Observations by means of scanning electron microscopy (SEM) indicate the creation of a 3D network through bridging of filler particles by adsorbed polymer. The rheological behavior is simulated utilizing a double network created by the entangled polymer matrix and the adsorbed polymer. Both networks are represented by a Giesekus viscoelastic constitutive equation. The dependence of rheological properties on filler concentration is taken into account through the density of polymer-filler interactions and a hydrodynamic reinforcement. The relative contribution of both networks is computed through the energy balance consistent with the thermodynamics of the chemical interactions and fluid mechanics. This self-consistent approach allows one to predict the major features of the rheological behavior of such systems.
Differential Scanning Calorimeters with Increased Sensitivity and Resolution
Resolution and sensitivity are two of the most important properties of thermal analyzers. Resolution can be described as the ability to separate and observe two events, which occur close to one another and sensitivity is the ability to detect very small effects. The ability to significantly shorten the overall experimental time and increase throughput, yet obtain data with improved resolution and greater sensitivity are highly desirable. In many labs involving thermal analysis of polymers, today's instruments provide a similar choice. In this paper, improved sensor design and firmware in Differential Scanning Calorimeters (DSC) will be discussed using few application examples.
Linearity and Non-Linearity of Mechanical Properties in Blends of Virgin and Recycled HDPE's
This paper investigates the behaviour of blends of Recycled Milk Bottle Resin (R-MBR) with Injection Moulding or Film Blowing grade HDPEs (IM-HDPE or FB-HDPE). This was done by measuring changes in mechanical and rheological properties as a function of blend composition and compounding intensity. There were three categories of compounding: bag mixing (BM), single pass single screw extrusion (EBx1) and double pass single screw extrusion (EBx2). The results were examined for linear and non-linear trends, and relationships between morphology, mechanical properties and molecular weights were proposed.
Specific Features of Dynamic Vulcanization and Properties of Thermoplastic Elastomers
The macrokinetic of dynamic vulcanizetion was studied. Criteria for selection a cross-linked system and condition for conduction one-step dynamic vulcanizetion were suggested. The influence of the ratio of the basic components, the content of plasticizer and mineral filler on mechanical and processing properties of thermoplastic vulcanizates (TPV) was investigated. The ageing of TPV was connected with recrystallization of polypropylene (PP). The mechanism of TPV's deformation is proposed.
Practitioner Training Program for Troubleshooting Injection Molded Part Defects
The objective of this paper is to document our study of injection molded part defects. The study of the defects is necessary in developing a training program for technicians and engineers. With this program one will be able to understand the causes of the defect and the steps required to eliminate it.
Blend of Post Industrial ABS and PMMA Improves Thermal and Impact Properties
The recycling of post industrial ABS and PMMA was investigated. A material compound consisting of 100% post industrial (PI) recycled ABS and multicolored acrylic (PMMA) scrap from a manufacturing plants was blended and extruded. Test samples were injection molded and the test results were correlated to virgin material. Additionally, the material was used in injection molding of rear lamp housings in black and gray colors. The test results and economics are promising.
Resistance of Glass Fiber-Reinforced Thermoplastics to Water Hammer
The resistances of three kinds of short glass fiber or glass bead-reinforced plastics [polyphenyleneether (GFPPE), polyphenylenesulfide (GFPPS), and polyoxymethylene (GBPOM)] to water hammer were studied. The fracture surfaces and the cross sections of the fracture surfaces were observed to investigate the fracture mechanism. PPE showed poor resistance to water hammer compared to PPS and POM. Investigation of the fracture surfaces showed that their surfaces were rather flat and hardly any glass fibers were observed at the fracture surfaces. It was found that the characteristic fracture surfaces was attributable to the breaking of the glass fibers at the fracture surface which is hardly observed in other modes of fracture such as tensile fracture.
Advances in Fusible Core Technique
Fusible core technology allows the production of injection molded parts which cannot be manufactured by conventional mold technology because of undercuts and internal geometries. The production sequence consists of several process steps. The reliability and economy of the process depend on each process operation as well as on the correct design of the interfaces between the steps. This paper presents sample applications, production methods and potentials for future applications. Moreover, current R+D work is described which mainly focuses on improved process engineering, a better understanding of the boundary conditions of product design and a wider range of applicable polymers.
Scale-Up Rules for Blow Heads
Alongside time-intensive flow analyses, requiring extensive calculations, the use of dimensional analysis is an alternative strategy for the design of blow heads. Selected blow heads are broken down into their basic geometrical elements and subsequently transfer formulas are established. Assuming for reasons of simplification that the material flow is isothermal, stationary and laminar and that wall adherence is prevailing, the concept of representative quantities is used to take into account the non-Newtonian behavior of the melt. The combination of the basic elements produce the full-scale device which -compared to the model - display both identical processing times and loss of pressure as well as unchanging shear velocity and wall shear stress, but will achieve different levels of material throughput.
The Processing of Renewable Resources Using a Short Single Screw Extruder with a Combined Section for Solid Conveying and Plastification
Due to the growing awareness of the necessity to protect the environment, the substitution of conventional plastic materials by biodegradable materials is gaining an ever increasing importance. An application that makes sense especially with regard to economic aspects is the processing of non-modified crop on plastics processing machines. This is made possible by the concept of a single-screw extruder equipped with a metering unit with which the total amount of energy required to plasticize the material is generated exploiting the friction occuring in the solid matter. As opposed to conventional extruder designs which exhibit separate areas for conveying the material and for plasticizing the same, these two tasks are united in one section of the extruder. The concept is based on specific geometries of screw and cylinder which secure that the entire mass flow passes a shear zone situated in the material conveying zone, warranting a very efficient transmutation of energy.
Transcription of Small Surface Structures in Injection Molding - An Experimental Study
The ability to replicate the surface roughness from mold wall to the plastic part in injection molding has many functional and cosmetic important implications from medical use to designer products. Generally the understanding of surface transcription, i.e. the replication of the surface structure from mold to plastic part, also relates to micro injection molding and molding of parts with specific micro structures on the surface such as optical parts. The present study concerns transcription of surface roughness as a function of process parameters. The study is carried out with a polystyrene part, process parameters at typical levels and a rough spark eroded mold surface with Ra = 12.6 ?m.
Influence of Molecular Weight Distribution on LLDPE Blown Film Processing Conditions and Property Sensitivity
The effect of key blown film processing parameters on linear low density polyethylene (LLDPE) film properties was investigated. The processing parameters studied were frost line height, blow up ratio, output rate and melt temperature. Statistically designed experiments were conducted with three high alpha olefins (HAO) copolymers of similar melt index, density and short chain branching distribution (SCBD) but of different molecular weight distribution (MWD). Film impact strength variations with processing conditions were found to depend strongly on polymer MWD.
The Relations between the Composition and the Permeation Resistance of the Polyethylene/Compatibilizer Precursor/Modified Polyamide Blends
The effects of compatibilizer precursor (CP) and modified polyamide (MPA) contents on the permeation rate of unleaded gasoline and on the morphology of polyethylene/modified polyamide (PE/MPA) blends are investigated. The optimal composition of PE/MPA for the lowest gasoline permeation rate is PE70/MPA15, which blended 30% of MPA (compounded 15% of CP with 85% of PA) with 70% of PE. The barrier properties improvement of PE/MPA blown tubes against unleaded gasoline reach a maximum (367 times at 25°C) comparing with genetic PE.
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