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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Effect of Formulation Variables on Rheology of Rigid PVC
The effect of lubricants, impact modifier, and process aid on the processing and physical properties of a rigid PVC compound have been modeled using a Central Composite designed experiment. Capillary rheology was used to evaluate the flow properties of the various formulations in the study. By modeling the rheological properties it is possible to simultaneously optimize flow, extruder conditions, and final part properties.
Mold Wear vs. Wall Thickness: Critical Information for Thin Wall Molding
The plastics industry is under increasing pressure to reduce the wall thickness of molded parts. Thin wall molding provides a host of concerns not present in standard molding applications. An analysis of the relationship between tool wear and wall thickness was conducted as part of the long-term copper alloy mold wear studies at Western Michigan University (WMU). This analysis suggests tool design for the proactive reduction of high shear erosive wear associated with thin wall molds.
Moulded Part Design for the Gas Injection Technique
In gas assisted injection moulding the melt front advancement has a considerable effect on the gas penetration. The evaluation of an appropriate melt filling is an important step to avoid instabilities in the process sequence. Taking a sample moulded part a procedure is presented that enables the part designer to evaluate required melt and gas injection points according to the gas injection technique. Using finite element simulations different calculations for the melt front advancement lead to the correct gate location in correspondence with the gas nozzle and the part geometry.
Thermoplastic and Elastomeric Toughened Cyanate Esters for Composite Applications
Cyanate ester resins were modified using thermoplastic and elastomeric materials to study their effect on properties and long term durability when used as high temperature matrices in glass fiber composites. Toughness improvements without significant sacrifices in flexural properties were only observed for the systems that did not phase separate. Conversely, the thermal properties of these materials were more seriously affected after exposure to a high temperature environment.
Correlation of Step-Wise Fatigue and Creep Slow Crack Growth in Polyethylene
The correlation in mechanism and kinetics of slow crack growth between fatigue and creep of high density polyethylene was studied. The step-wise crack propagation mechanism characteristic of long-term failures in polyethylene was observed over all fatigue and creep loading conditions examined. Fatigue fracture kinetics allowed for extrapolation to the case of creep failure, which suggested that short-term fatigue testing can be used to predict long-term creep fracture properties. Under high stresses the presence of shear deformation retarded crack growth.
Utilization of Dynamic Feed Control in Family Tools
Just-in-time business agreements have forced molders to become more flexible in the way they produce parts. One way to improve efficiency in the production of complete assemblies is to mold all of the components at once in a family tool. This paper examines the ability of Dynamic Feed Control to produce high quality parts in family tools with widely varying parts in regards to wall thickness and volume.
Effect of PP-GMA on Properties of Talc Filled Polypropylene
Glycidyl methacrylate grafted polypropylene (PP-GMA) was used as a coupling agent in a PP/talc blend. Two coupling agents with GMA grafting levels of around 0.34 %wt. and different molecular weights were used. It was found that the use of PP-GMA at concentration between 1 and 10 %wt. increased the tensile strength and impact resistance of PP/talc composites. The performance of the PP-GMA was comparable to commercial PP-MAH modifiers. The chemical or physical effect of the coupling agent are discussed.
Optimization of the Weld Line in Injection Molding via an Experimental Design Approach
Weld lines are sometimes inevitable when processing large and complex parts by injection molding. In this paper, a design of experiments approach (Taguchi Method) was utilized to study the influence of seven processing variables (melt and mold temperatures, injection and hold pressures, cooling and holding times, and back pressure) on the weld line width and the tensile impact properties of injection molded dog-bone bars. The important processing variables affecting the weld line behavior are identified.
Effects of Additives on Scratch Resistance of Polypropylene Materials
Pigmented mineral-filled polypropylene (PP-PMF) is marketed as a potential alternative to ABS (acrylonitril-butyldiene-styrene) and ABS/ PC (acrylonitril-butyldiene-styrene/ polycarbonate) for interior automotive components. PP-PMF is more easily damaged by surface scratch & mar, thus limiting its acceptance for interior applications. This study investigates the scratch and mar mechanisms of talc-filled PP and the effects of various additives on the scratch and mar resistance of PP-PMF. Talc filler provides higher modulus for PP. The addition of nucleation agent and lubricant showed beneficial effects.
Observation and Characterization of Slow Crack Growth in Water Pipe Grade Polybutylene
Polybutylene (PB) piping has been widely used in portable water distribution systems. Premature brittle fracture constitutes the major limitation for PB in its application. The fracture process of PB consists the well recognized three stages: crack initiation, slow growth and fast propagation. In present work, the observations of crack initiation in service, fatigue slow crack growth (SCG) at elevated temperature, strain localization in front of the crack constituting the process zone (PZ) as well as variability of the strength of PB are reported.
The Time Dependency of the Necking Process in Polyethylene
Characterization and comparative analysis of necking phenomena in HDPE under load (creep) and displacement (ramp) control conditions are reported. For creep tests a simple exponential dependence of delay time to necking on the applied stress is observed. The applied stress and strain rate dependence of yield stress for both creep and ramp tests are presented.
Rheological Study of Soy Protein-Based PRF Wood Additives
The gelling of soy protein-based PRF wood adhesives is studied. Soy protein isolate, in combination with phenol resorcinol formaldehyde (PRF) resins is useful in the finger joining of lumber. This unique technology has several advantages including an ability to bond green lumber, very rapid set at room temperature, excellent water resistance, and reduced formaldehyde emissions. The goal of this study is to quantify the effect of soy protein hydrolysis conditions and amine functionality on the gelling and ultimate modulus of soy-derived wood adhesives.
The Effect of Fillers on the Properties of Rotationally Moulded Polyethylene
This paper describes the effects of talc and mica as fillers in rotationally moulded medium density polyethylene-MDPE. Adhesion between the filler and the matrix was enhanced using maleic anhydride modified polyethylene. Results show a clear increase of the modulus and in some cases an improvement in the tensile strength, but a decrease in the elongation and impact properties. Shrinkage of the moulded articles was reduced, and internal air temperature measurements show a reduction in the cycle time.
Computer Simulation of the Rotational Moulding of Plastics
This paper describes the development of a computer simulation for the rotational moulding of plastics. Two separate aspects of the process - the kinematics of the mould rotation and the heat transfer to the plastic powder - are modelled separately and then combined into a complete simulation. The simulation is capable of reading CAD files of real rotomoulded components, and variables such as speeds, speed ratios, material bulk density, etc can be set by the user. The program will then predict and display the wall thickness distribution in the moulded article.
TLCP Droplet Dynamics and Their Role Inviscosity Reduction
Blends of polyethylene (PE) with very low TLCP concentrations have viscosity ratios of 10-6 to 10-4, and viscosity reductions > 90% are observed. This viscosity reduction is generated by a number of mechanisms in sequence, wall slip being only one. The others are droplet coalescence, deformation and fibril formation, plus effects associated with the TLCP's ability to self-order and align when under shear, leading to a phase transition in the nematic-isotropic biphase. Intercomponent adhesion and interfacial tension also influence the droplet dynamics.
Continuous Polymer Melt Filtration
Filtration is required of nearly every flowing polymer process. Most processes utilize filter elements that must be removed periodically for replacement or cleaning. The gradual pressure buildup that accompanies filter blinding results in an unwanted temperature rise with consequent loss in dimensional control of the product and sometimes with a reduction in output. A continuous filter that would continuously replace itself or that would clean itself automatically has been sought by industry. This paper describes the original device of this sort and reveals how it operates.
Effect of Dispersed Phase Structure on High Speed Impact Test of Multicomponent PP Systems
This work presents results obtained for ternary blends of polypropylene (PP), linear low density polyethylene (LLDPE) and ethylene-norborene terpolymers (EPDM). The effect of the addition of LLDPE on the state of dispersion of different EPDM is studied. Morphological features of injection molded samples and their influence on the impact properties are analyzed. The dispersive effect of LLDPE produces higher increments in impact strength when the EPDM is homogeneously distributed in the whole specimen.
Durability of High-Performance Adhesive Joints
Adhesive specimens were prepared from Ti-6Al-4V and a commercial polyimide adhesive. Specimens were aged for up to 90 days in air at 177°C. The notched coating adhesion (NCA) test was used to characterize the adhesive performance. Interfacial degradation due to elevated temperature aging is accelerated in the NCA specimens due to a shortened diffusion path. The adhesive at the interphase appears to be weakened after elevated temperature aging in air.
Empirical Equations for Predicting Sink Mark Depth in a Rib-Reinforced Plastic Part
Two empirical equations for predicting sink mark depth on the surface opposite to a reinforcing rib in an injection-molded plastic part are presented. Extra thermal mass and effective packing time near a rib base are used as the two determining parameters for calculating the sink mark depth. A normalized geometric sink mark index is used as a measure of the extra thermal mass near the rib base, whereas, the time from the end of filling to the time required for the pressure to vanish near the rib base is used as the effective packing time.
Three-Dimensional Simulation of Plastic Molding Processes
Finite element method is used for a three-dimensional simulation of moving boundaries in an inertia-free, incompressible flow. A control volume scheme with a fixed finite element mesh is employed to predict the fluid front advancement. The predicted fluid front advancement and pressure variation in a flow domain similar to the mold cavity used for microchip encapsulation are compared with the corresponding experimental results. Flow simulation for a more complex mold cavity is also presented.
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