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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High Velocity 3 Point Bending Test Using an Impact Tower
The idea of using an impact tower for 3-point bending for polymer testing has been developed before . In this work the experimental method is refined. The vibrations are reduced by removing the ends of the specimen and by using a smaller span. Results are presented for a polypropylene. The modulus and the yield stress increase with strain rate, as predicted by viscoelastic consideration and by the Eyring theory for the yielding of polymers.
Coloration of Polytrimethylene Terephthalate Fibers with Pigments and Polymer Soluble Dyes
Polytrimethylene terephthalate (PTT) is a recently commercialized polymer with both demonstrated and potential for increasing use in fibers for carpets and textiles. It is both dyeable in the conventional sense but also readily colored in the melt phase with pigments and polymer soluble dyes. This paper explores the methods used to mass color (solution dye) PTT, the pigments and dyes that can be employed, and the color and fastness results obtained with eleven selected colorants.
Dynamic Light Scattering Method for Determination of Shelf Stability of Liquid Colloidal PVC Stabilizers
Many liquid mixed metal stabilizers are colloidal microemulsions of water in oil. Their shelf stability is a function of the diameter of microemulsion droplets. Microdroplets with a diameter less than 50-60 nm and low tendency to aggregate are shelf stable. A fast procedure for estimation of shelf stability of liquid stabilizers for PVC based on determination of microdroplet diameters was developed.
Behaviour of Fibre-Bearing Syntactic Foams in Compression and Flexure
The comparative performances in three point bending and compression of syntactic foams comprising of epoxy resin and glass microballoons with the inclusion of chopped glass fibres of two different resin compatibility namely, epoxy and phenolic, are reported. The data showed that the compressive strength values differ marginally. As regards the flexural strength it increases for a change from epoxy to phenolic. When the properties of third syntactic foam with polyester compatible fibres was examined, it was found that the value was higher than the epoxy counterpart. This was attributed to the difference in the procedural route adopted for fabricating this latter foam.
Optimizing Injection Molding towards Multiple Quality and Cost Issues
Injection molding part designers are frequently faced with multiple quality and cost issues. These issues are usually in conflict with each other, and thus tradeoff needs to be made to reach a final compromised solution. Since evaluation of part quality and cost via injection molding simulation is very time-consuming, implementation of a conventional multi-criteria optimization procedure to injection molding problems is economically unfavorable. However, many injection molding problems dealing with multiple quality and cost issues can be modeled as constrained problems. By introducing a concept of Penalized Total Cost, such constrained problems are further simplified into bounded single-criterion problems. The bounded single-criterion problems are then optimized using a direct search-based optimization procedure. Strategies of modeling, transformation and optimization for these problems are discussed in this paper. A case study is provided.
Elongational Effects of Die Flows: Pressure Distribution and Shape Prediction
There are many industrial applications in which shear and extensional behaviors of the material both play a role. This is true, for example, for flows in converging channels or flows in abrupt contractions typical of cable coating, fiber spinning or indeed flows in many plastics and rubber extrusion dies. Viscoelastic flow simulation has made it possible to predict these effects, at least qualitatively. Numerical simulations using a 3-mode PTT model reported here show a good quantitative agreement with experimentally measured pressure drops over a range of flow rates for both a short and a long conical capillary die. While this approach is physically meaningful, convergence at high Weissenberg number remains a challenge for the scientific community. This fact can sometimes justify the call for simpler, qualitative engineering approximations. By adding in the flow equations the dependence of the viscosity function on the third invariant of the rate of deformation tensor, it becomes possible to consider some effects of extensional viscosity in axisymmetric and 3D flows. We observe an increase in the pressure drop and the onset of recirculation patterns. We present numerical simulations of flow in a converging cone capillary and compare the results with available experimental data. We include simulation results for 3D die swell which show the influence of this extensional effect.
Toughening and Strengthening an Epoxy by a Liquid Crystalline Epoxy
The effect of molecular reinforcement of diglycidyl ether of bisphenol F (DGEBP-F) epoxy by liquid crystalline (LC) diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) is investigated. The compositional effect of the LC moiety is related to mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Dynamic mechanical analysis is conducted to determine the effect of the DGE-DHBP on the glass transition and beta transition temperatures. Scanning electron microscopy of the fracture surface shows changes in failure mechanisms compared to the pure components. The results indicate that the mechanical properties of these blended samples are improved at 10-20% by weight of DGE-DHBP.
Surface Damage Resistance of Automotive Plastics
Damageability of automotive plastics, inflicted during events such as scratching, chipping, and compressive shearing, results in potentially high warranty costs and customer dissatisfaction. Polymer alloy composition, e.g., polymer-polymer interphase behavior and polymer-filler interactions, plays a major role in resultant damage resistance of a formed plastic part. Polymer processing, e.g., injection molding, also strongly affects the ability of a plastic surface to withstand such damage. This paper attempts to describe the role of polymer alloy composition, specifically filled- and unfilled-poly(olefin) blends, and final part processing behavior on surface damageability caused from scratching, chipping, and compressive shearing (gouging"). The role of interphase management e.g. control of miscibility between alloying agents appears to be the major factor affecting the ability of the plastic part to resist surface damage caused by external forces."
Fatigue Behavior of Discontinuous Glass Fiber Reinforced Polypropylene
The fatigue properties and mechanism of 30% wt. short glass fiber reinforced chemically coupled and uncoupled polypropylenes were determined. Depending on the degree of damage, debondings effect the load transfer to the fibers. Final fracture occurs if the number of non-loaded fibers in one cross-section increases up to the critical value. When the fatigue data was presented as S-N curves, both materials have not showed any endurance limits. The microstructural mechanisms were discussed by help of SEM observations.
Numerical Simulation of Bi-Layer Extrusion Flow within a New Conical Extruder
In this study, the coextrusion flow in the die section of a new type of multi-layer extruder is determined. The prototype extruder used is based on a conical rotor-stator assembly. The extrusion of a range of individual layers of PEs was investigated. Numerical simulation, based on an axisymmetrical model of the assembly using an inelastic fluid model, was used to analyze the flow behavior.
Freeze-Thaw Durability of Composites for Civil Infrastructure
Freeze-thaw durability is a critical area that needs to be investigated prior to implementing composite material use in civil infrastructure. This work will examine the performance of pultruded vinylester/glass and epoxy/glass cross-ply laminates in different aging environments. Tensile test data encompassing strength, stiffness, and strain-to-failure on as-received" and moisture saturated material will be presented as well as saturation moisture uptake data. Discussion of continuing experimental work related to freeze-thaw cycling will also be addressed."
Mechanical Properties of Glass Fiber Composites with an Epoxy Resin Modified by a Liquid Crystalline Epoxy
The effect of liquid crystalline networks on epoxy - glass fiber composites is investigated. Liquid crystalline epoxy resins (LCEs) have many advantages including outstanding high temperature stability, high lateral strength with high axial compressive strength. The matrix is obtained from in-situ curing of liquid crystalline diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) with diglycidyl ether of bisphenol F (DGEBP-F. Impact, tensile, and compressive results are compared between the unmodified and modified systems. Scanning electron microscopy is used to study the fracture surface to understand the mechanism of fracture and interphase formation between the fiber and matrix.
Effects of Moisture Content, CEC, and Processing Conditions on Mechanical Properties and Long-Term Reliability of PBT Fiber-Optic Buffer Tubes
Poly-butyleneterephthalate (PBT) Fiber optic buffer tubes were manufactured while varying initial material Carboxyl Endgroup Concentration (CEC), initial moisture content, as well as extrusion linespeed and cooling profile. Mechanical tests on aged and unaged tubes were correlated to the state of material degradation through capillary rheometer experiments and Melt Flow Index (MFI) measurements. Incomplete drying and use of PBT with a high initial CEC are shown to lead to more rapid reduction of molecular weight during extrusion as well as poorer long-term hydrolytic stability. By proper selection of material and processing conditions, material lifetimes can be at least doubled.
Characterization of the Near-Surface Crystalline Structure and Morphology of Injection-Molded TPO
Near-surface structure is expected to play an important role in determining the surface mechanical and adhesive properties of injection-molded Thermoplastic Polyolefins (TPOs). In this report we discuss the near-surface structure of injection-molded TPO based on isotactic polypropylene (iPP), with the intention to elucidate the influence of the TPO substrate structure on the adhesion of painted layers. Localized flat-film X-ray diffraction has been used to characterize the crystalline structure of the iPP component, while transmission electron microscopy (TEM) has been used to reveal the high resolution morphology of iPP crystals and secondary particles. The polymorphism and texturing of the near-surface iPP crystals is discussed, based on the generally accepted structures of iPP crystalline phases. There is evidence to support the presence of ?-phase PP crystals in the near surface area. Significant anisotropy in the secondary particle morphology was revealed by TEM imaging.
Mold Filling and Curing Analysis in Scrimp
In recent years, vacuum-assisted resin transfer molding (e.g. Seemann Composite Resin Infusion Molding Process - SCRIMP) has been widely used for marine, civil infrastructure, transportation and defense applications. Unsaturated polyester and vinylester resins are two major resins used in these processes. Their kinetic and rheological behaviors were investigated experimentally. A model was developed to quantify the effects of different curing agents on the gel time and reaction rate. This model, in conjunction with fluid flow and heat transfer models, was used to determine the effects of resin type and composition, curing temperature, and part geometry on mold filling and curing. SCRIMP experiments were carried out to verify the simulation results.
Improving the Performance of Rotomolding Resins
Rotational molding is one of the fastest growing processes in the plastics industry today. However, this growth has been somewhat restricted by the number of and types of resins available to the molder. Polyethylene has traditionally been the workhorse for the industry because of its ease of processing. Unfortunately polyethylene lacks stiffness, along with other mechanical properties, compared to the resins used in competitive processes. This paper outlines methods to improve the performance of rotomolding resins using processing techniques, modifying the design of the part and by the inclusion of strengthening additives in the polymer matrix.
Laser Surface Modification of Polymers to Enhance Adhesion Part II-PEEK, APC-2, LCP and PA
Excimer lasers have been employed to modify the surfaces of a range of polymers to enhance adhesion. Considerable increases in joint strength were achieved as a result of laser treatment. Many lap shear joints, exposed to hot/wet environments, provided high retention of joint strength and durability. Laser-treated PEEK and APC-2 joints exposed at 50°C and 96%RH for several weeks, showed excellent resistance to ageing.
Stereolithography Inserts - Pros" and "Cons" to Use Tin as a Backfilling Material"
Stereolithography inserts shells for injection molding tools are filled in the backside, aiming to support high pressures and to improve the cooling efficiency on the mold. A common backfilling material used is an alloy of bismuth. However, there are other alternatives, such as tin, which has a higher thermal conductivity. This article discusses the pros" and "cons" to use tin as a backfill and investigates if it provides a better cooling condition improving mold's life."
Enhancement of Natural Fiber-Epoxy Interaction Using Bi-Functional Surface Modifiers
Enhancement of fiber-matrix interaction for a jute-epoxy composite system was attempted by surface modification of the fibers. The surface modification of jute fibers was achieved using bi-functional amines, which were capable of bonding with both the fiber and the matrix. The changes in interface bonding were observed by measuring the flexure modulus of the composite samples.
Effects on Mechanical Properties of LLDPE after Modification with Organic Peroxides
The action of two differents organic peroxides at 290°C on the mechanical properties of linear low density polyethylene (LLDPE) viewing its application as internal pipeline coating was studied. When the amount of crosslinking agent increased on polyolefin it was observed that for both peroxides a decreasing of elastic modulus and stress at yield. The stress at break raised and the drop of elongation at break cocurred from 0,5% of peroxide.
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