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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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.
Entrance Flow Simulation Using Elongational Properties of Plastics
A finite element simulation of the flow in a channel with an abrupt contraction is presented. Effects of shear and elongational viscosities of a polymer on the entrance flow is analyzed. The shear and elongational viscosities are represented by the truncated power-law model. The power-law index for the elongational viscosity is independent of the value of the power-law index for the shear viscosity. It is confirmed that Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow.
Effect of Elongational Viscosity on Die Design for Plastic Extrusion
A finite element simulation of the flow in a rectangular die with an abrupt contraction is presented. Effect of shear and elongational viscosities of a polymer on the flow in the die is analyzed. The shear and elongational viscosities are represented by a truncated power-law model. The power-law indices for the planar and axisymmetric elongational viscosities are found to have significant effect on the pres-sure and velocity fields in the die.
Characterizing Co-Continuous Polyethylene/Polystyrene Blends
Co-continuous blends of high density polyethylene/polystyrene (PS/PE) have been studied. The influence of a triblock copolymer, styrene-ethylene-butadiene-styrene (SEBS) was also investigated. The surface area, pore diameter and pore size distribution of the blend system after solvent extraction of one of the phases has been measured using a BET nitrogen adsorption technique and mercury porosimetry. Using this technique, it was also possible to generate an emulsification curve, demonstrating the region of interfacial saturation for this complex system.
Orientation Studies of Microbial Polyesters at the Air-Water Interface
The orientation of organic thin films of natural polymers of microbial origin was studied with the aid of LangmuirBlodgett films and x-ray reflectivity. The polymer system studied included a number of polyhydroxyalkanoates, a family of microbial polyesters which include both thermoplastic and elastomeric materials and which have previously been shown to form stable monolayers at the air-water interface. The spreading behavior of each polymer was studied and the orientation of the polymer following transfer to a substrate was determined using x-ray reflectivity.
The Design of Flat Extrusion Dies and Feedblocks
Efficient three-dimensional algorithms are now being used routinely in the design of flat extrusion dies and coextrusion feedblocks. The usual assumptions made in 1-D and 2-D analyses (i.e., lubrication approximation, hydraulic radii, geometry shape factors, etc.) are no longer necessary when full 3-D flow equations are solved everywhere in the die or feedblock. How these algorithms are being used to design flat dies (both with or without deflection) and feedblocks is demonstrated through actual examples.
Optical Sensing of Thermoplastics Solidification in an Injection Molding Machine
An optical technique for monitoring the solidification of thermoplastics was implemented and studied. A He-Ne laser illuminated the mold cavity through an optical window and a photomultiplier measured the intensity of reflected light during the molding cycle. The light measured is a complex composite of reflection and refraction from crystallites, the mold wall and as many as six interfaces. Polystyrene, polypropylene and high-density polyethylene were used. Further work is required to use this technique for process control purposes.
Property/Processing Enhancement via Improved Low-Temperature Fusion for Rigid PVC Construction Products
Impact property development in RPVC construction products is highly dependent on the type of impact modifier used and its contribution to processing. With increasing attention being paid to all aspects of production, particularly machine utilization and cost effectiveness of raw materials, maintaining performance properties remains critical. This study discusses how impact modifier selection can influence processing and the levels of other ingredients, and through these effects, influence the performance properties of articles like siding and window profile.
The Effect of Scale-Up on the Processing Behavior of a Blend Exhibiting Phase Inversion during Compounding
Phase inversion during compounding of low-viscosity ratio polystyrene/polyethylene blends was studied in two different batch mixers. Using a constant maximum-shear-rate as the scale-up criterion, longer mixing times were required in the large mixer due to its lower specific area. A new triangular element blade design was used to obtain different batch sizes in the same mixer. On scale-up with these blades, a constant specific area was maintained and equal mixing times to phase inversion were observed.
Design and Optimization of Three Dimensional Extrusion Dies Using Adaptive Finite Element Method
A numerical algorithm to automatically design polymer extrusion dies is developed. The method uses an adaptive finite element model and shape optimization methodology to define the transition section and the land lengths of a profile die. The ultimate goal of this work is to develop a simulation tool that could be used by extrusion die designers which functions like the CAD-integrated simulation tools available for injection mold designers today.
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