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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PENT AND ITS APPLICATION IN PIPE LIFETIME PREDICTION
A new method of evaluating the polyethylene (PE) pipe lifetime in brittle failure has been recently proposed. It consists of an extrapolation of the failure time in the Pennsylvania notch test to arbitrary PE pipes at various loads and temperatures. This paper presents a detailed review of the theoretical and experimental basis of the new lifetime prediction method and discusses its limitations. An experimental examination of the proposed method applied to a commercial high-density PE is reported. The results suggest that the proposed method overestimate the lifetime at room temperature by 30 ~ 40 times. It is inadequate for extrapolation of brittle fracture time of PE from 80°C to room temperature. Such limitation is related to the changes in failure mechanism and kinetics of crack growth taking place at some intermediate temperature. An alternative method for PE pipes lifetime prediction based on a combination of testing and modeling is discussed.
COLD DRAWING AND ITS ROLE IN FRACTURE OF POLYOLEFIN PIPES
There are three major modes of polyolefin pipes failure: ductile, stress driven brittle and degradation assisted brittle fractures. The ductile failure results from material instability on macro-scale. It appears as a ballooning resulting from large-scale strain localization (stretching and thinning) similar to that observed in cold drawing in uniaxial tension (necking). The brittle fracture is manifested in cracking with no large deformation on macro-scale. However, there is a localized crazing in front of the crack, which consists of micro fibers and membranes. It also results from cold drawing, but on micro-scale. This paper presents analysis of cold drawing as time dependent phase transition referred to as “delayed necking”. The connections between ductile and brittle polyolefin pipes failure from one side and delayed necking on another are discussed.
ENHANCING BIOPOLYMERS WITH HIGH PERFORMANCE NATURAL TALC PRODUCTS
The effect of talcs on PolyLactic Acid (PLA) performance has been studied with a focus on properties of fully crystallized PLA. The results show that talc could be used as an effective nucleation agent to improve mechanical properties of PLA including stiffness, heat deflection temperature and impact strength. It is also shown in two PLA formulations that Luzenac High Aspect Ratio talc (HAR®) in combination with plasticizers and impact modifiers could further improve crystallization speed and impact properties through modifying the amorphous phase of PolyLactic Acid.
USE OF DIGITAL IMAGE CORRELATION AND INVERSE MODELING TO DETERMINE RESIDUAL STRESS IN AXISYMMETRIC POLYMER COMPONENTS
This paper presents a new method to determine residual stress profiles in cables and other axisymmetric objects using digital image correlation and inverse modeling. 3D digital image correlation with two cameras and stereo-vision was used to determine full-field displacements resulting from cutting a slit in a disk made from cable insulation. These displacements were compared to predicted displacements in a finite element analysis of the cutting. Differences between nodal displacements and the corresponding measured displacements were used to construct a cost function which was iteratively minimized by changing the residual stress field used as initial condition in the finite element simulation.
KEY ISSUES IN MICROFABRICATION, THERMAL BONDING AND SURFACE MODIFICATION OF CYCLIC OLEFIN COPOLYMER (COC/TOPAS®) MICROFLUIDIC DEVICES
Cyclic olefin copolymers (COC/TOPAS) are commonly employed for making microfluidic devices. Several issues need to be addressed before this can be realized. A reliable technique for micro-replicating COC is required. Good sealing and high bond strength between COC inter-layers without destroying channel integrity is necessary. The intrinsically hydrophobic surface has to be rendered hydrophilic to facilitate flow and electrophoretic separation. Here we report the production of high fidelity microdevices by hot-embossing. Thermal seals with high bond strengths for bonding below the glass transition temperature Tg, photografting using suitable hydrophilic monomers to give good surface wettability and hemocompatibility are outlined.
Optimization of Nanocomposites Injection Molding by design of Experiments
Design of experiments (DOE) is a systematic method based on designed experimental rums used to evaluate the effects of selected variables on the final product properties. The method is especially useful when materials are expensive and/or scarce and only small quantities are available for experimentation, such as with carbon nanotubes (CNT). The effects of injection molding on the properties of Polycarbonate and Polybutylene Terephthalate multi-wall CNT composites were studied using DOE. Results demonstrated that although only a small number of experimental runs were used, a significant effect of the injection molding parameters on the properties of the nanocomposites was detected.
PHYSICOCHEMICAL PROPERTIES OF PLASMA POLYMERIZED ACRYLIC ACID, ε-CAPROLACTONE AND LACTIC ACID FILMS
The physicochemical properties of plasma polymerized films were investigated by means of X-Ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectrophotometry (FTIR), ellipsometry and Water Contact Angle. Three different monomers (acrylic acid, ε-caprolactone and lactic acid) were polymerized in a Plasma Polymerization System for different times (7, 15 and 30 min) and power conditions (80 and 120 W). While plasma polymerized acrylic acid and ε-caprolactone shared a strong similarity with the conventional polymers, lactic acid did not bear any resemblance to the conventional polymer.
PVC – Moving Up to the Next Level
The papers from the most recent IOM3 conference, PVC 2011, are used as the basis for this paper. The PVC market is reviewed on the basis of Europe’s environmental challenges with management options being reshaped by global megatrends. The cost competitiveness of PVC products, energy saving from using PVC products and increasing recognition of our sustainable development progress can only serve our industry well into the future. The Voluntary Commitments of the past ten years (Vinyl 2010) and the next ten years (VinylPlus) are reviewed. Examples of educational initiatives in the UK to improve perceptions are also highlighted.
MECHANICAL AND THERMAL PROPERTIES OF SUPERCRITICAL CARBON DIOXIDE PROCESSED EPOXY SILICONE BLENDS
Mechanical and thermal properties of epoxy have been modified through blending of diglycidylether of bisphenol A (0.1 mol) with polydimethylsiloxane (PDMS) at concentration ranging 1.0 to 3.0 phr of resin at 1400 psi and 90±10C for 1hr in supercritical carbon dioxide (scCO2), followed by curing with triethylenetetramine (10 phr) at 40±10C.The formation of synthesized epoxy silicone blends (ESBs) has been ascertained through ultraviolet –visible (Uv-vis), Fourier transformed infrared (FT-IR), X-ray diffraction (XRD) spectra and microscopy. With PDMS concentration, the compressive, tensile strength, Rockwell hardness (R scale), fringe values and crystallinity of ESBs were decreased with simultaneous increase in their impact strength, resistance against wear and thermal stability. Key words: Supercritical carbon dioxide, Polymer blends, Spectra, Morphology, Mechanical and thermal properties.
COMPLEX INVESTIGATION OF INJECTION MOULD FILLING
Thin wall injection moulding is a difficult process. High viscosity polymeric material is injected into a mould by high speed and high pressure. A special instrumented injection mould was designed for the investigation of the cavity filling of injection mould. Rheological measurement can be carried out with different wall thickness slit die inserts. The pressure can be measured during the filling, the packing and the cooling stages as well. The pressure drop during the filling can be used for determination the flow properties of the material. The measured cavity pressure of the injection cycle is proper for the validation if thin wall injection moulding simulation. The filling of the dies was simulated by Moldex3D software.
SYNTHESIS OF POLYPYRROLE / POLYTHIOPHENE COPOLYMERS IN SUPERCRITICAL CARBON DIOXIDE
Chemical oxidative copolymerization of pyrrole with thiophene was conducted using ferric chloride initiator at 90 °C, 1200 psi over 24 hours in supercritical carbon dioxide (scCO2). Polymerizations were conducted with different concentration ratios of pyrrole to thiophene 1:0, 0:1, 1:1 and 1:2 in a 100 mL high-pressure batch reactor. Polymerization yield which was up to 56.7 % in homopolymerizations was found to decrease in copolymerizations at molar ratio of pyrrole to thiophene 1:1 .The polymers were characterized by ultraviolet visible (Uv-vis), Fourier transformed infrared (FT-IR) spectra, elemental analysis, gel permeation chromatography (GPC), simultaneous thermogravimetricdifferential thermal analysis-differential thermogravimetry (TG-DTA-DTG), electrical conductivity and atomic force microscopy (AFM). Key words: Supercritical carbon dioxide, Polymerization, Polypyrrole, Polythiophene, Copolymers, Characterization.
Evaluation of tribological behavior of amorphous and crystalline thermoplastic compounds under high pressure, velocity and temperature conditions
In the present study, the friction and wear properties of two high temperature resistant polymers, an amorphous polyetherimide (PEI) and a crystalline polyetheretherketone (PEEK), have been investigated at specific combinations of high pressure, velocity and temperature against smooth steel counterparts. The effects of internal lubricant, polytetrafluoroethylene (PTFE) and PTFE with short fiber reinforcements (carbon fiber) are outlined. The tests were performed on a thrustwasher testing machine under dry sliding conditions. Different analytical techniques were employed to study the correlation between the transfer layer and wear properties. Lubricated and lubricated-reinforced compounds showed excellent wear properties compared to pristine resins throughout all PV conditions.
Development of novel Wood Plastic Composites (WPC) using as natural filler wood from the recycling of leisure sailing ships
Plastic Wood Composites, or commonly known as WPC, are a novel and interesting alternative to the usage of wood in certain applications, improving the properties of the final products thanks to the polymers intrinsic properties. However, compatibilization between the polymer matrix and the wood fibers or particles is a key factor that must be taken into consideration. Hydrophilic fibers are not compatible with hydrophobic polymer matrices, such as polyethylene or polypropylene (the main used polymers due to their processing temperatures and the low degradation temperature wood possess). The present research aimed to develop WPC using as the natural fiber recycled wood obtained from out-of-use leisure sailing ships. The objectives of the research presented and added new challenges on the development of such natural composites, posed by the state of the wood to be used, usually contaminated with salt, rests of minerals and rests of organic matter, so an excellent decontaminating process was a must. Once the wood conditioning processes were completed, a conventional extrusion process was carried out to obtain the WPC. The polymers used as polymer matrix were Low Density Polyethylene (LDPE) and Polypropylene (PP). Four different concentrations of wood fibers were used (10%, 20%, 30%, 40%) in order to determine their properties according to the fiber concentration. Also, two different compatibilizers for wood and polymers were used to check their behavior, as well as composites without compatibilizers were obtained. Finally, characterization techniques, including SEM microscopy, mechanical and impact properties and aging tests were carried out for all the developed WPC composites. Results indicate which were the best wood concentration on the composites as well as the best compatibilizer and its concentration on the final composite.
MECHANICAL TESTING OF POLYPROPYLENE MATERIALS IN SHEAR ANALYSED BY DIGITAL IMAGE CORRELATION
Three polypropylene-based materials (two talc-filled compounds and one unfilled homopolymer) were tested with two in-plane shear test methods (Iosipescu and V-notched rail). The three materials behaved differently in the shear tests. Most notably, cracks developed in tension near the notches for the particle-filled materials, while the unfilled homopolymer did not fracture. There were also differences between the materials regarding strain localisation between the notches, and thickness change in the sheared section. The stress-strain curves obtained with the two shear tests were quite similar.
MATERIAL MODELLING FOR SIMULATING IMPACT LOADING OF INJECTION-MOULDED POLYPROPYLENE PARTS
This paper describes the calibration and verification of a material model used in the numerical simulation of mechanical loading of plastic parts. The material model features strain rate dependent yield stress, pressure dependent yield stress, plastic dilatation and damage. The model was calibrated with data from tests in uniaxial tension, shear and uniaxial compression, utilising 3D digital image correlation for full-field displacement measurements. Two load cases were simulated; centrally loaded clamped plates and three-point bending of bars. The predictions of force vs. deflection were good to fair. The results are discussed in terms of deficiencies of the calibration data, heterogeneity and anisotropy of the injection-moulded components, and shortcomings of the model.
EVALUATING THE REACTIVE BLENDING OF PET/PEN IN A TWIN-SCREW EXTRUDER: AXIAL DISPERSION MODEL
The transesterification of PET and PEN in a twin-screw extruder (TSE) was investigated. A theoretical model, able to predict the extent of transesterification reaction (X) and degree of randomness (RD) against processing parameters along the screw axis is presented. PET/PEN blends were prepared via the melt mixing process. The axial dispersion model (ADM) was developed for modeling the twin screw extruder. Extent of transesterification reaction and degree of randomness was examined via Nuclear Magnetic Resonance Spectroscopy (H-NMR). Theoretical and experimental results were in good agreement, allows the prediction of the X and RD as a function of processing parameters such as time, temperature and composition.
LIFETIME PREDICTION IN ENGINEERING PLASTICS - LIMITATIONS OF SHORT-TERM TEST EXTRAPOLATIONS
Using short term tests to predict future outcomes of any long term process is common in extrapolation techniques in Science, Social science and Engineering. However, in every process it is important to ascertain some sort of criterion before extrapolation techniques are employed. The criteria for predicting lifetime of an engineering plastics for the specific application must include the requirements of the test to (a) reproduce the mechanisms of field failures and (b) have a technically sound procedure for extrapolation of a the relatively short test data. We will finally propose a quantitative modeling approach as an alternative to “empirical” extrapolation.
POLY(LACTIC ACID) – INVESTIGATION AND MODIFICATION OF MECHANICAL BEHAVIOR
Both industrial and scientific interest in poly(lactic acid) (PLA) increased in recent years for various reasons; hopes are rising that this material may represent an alternative to commodity polymers. In order to answer these expectations, thorough characterization and modification of poly(lactic acid) is necessary. The actual presentation focuses on the mechanical properties, especially the impact resistance of PLA. Attempts were made to improve this characteristic by blending with both rigid and elastomeric polymer grades. The blends were characterized with various techniques in order to compare toughening methods in these systems, and enlighten the relationship between interactions, structure and macroscopic properties.
CHEMICAL DEGRADATION DRIVEN CRACKING IN PE PIPES
Stress corrosion cracking (SCC) in polyolefin pipes usually starts as a microcrack colony within a degraded layer adjacent to the pipe surface exposed to combine action of mechanical stress and chemically aggressive environment. One can distinguish four stages of SCC: 1) microcracks initiate within the degraded polymer; 2) slow growth of individual cracks; 3) strong interaction of cracks and formation of clusters; and 4) clusters growth and crack/or cluster instability leading to the ultimate failure. The stage of crack initiation is primarily controlled by chemical degradation, and the second stage is strongly related with the effect of mechano-chemical degradation at process zone. The interaction of multiple cracks and clusters are typically observed after the many cracks grow individually. In this paper, the mechanism of crack initiation and growth due to mechano-chemical degradation is addressed and modeled.
AUTOMOTIVE SUNROOF SYSTEMS AND FRAMES IN XIRAN® SMA/ABS
Automotive Sunroof Systems, which have become a must have for the added comfort and styling to today s cars, increasingly rely on engineering plastics functionalities to replace metals. Structural and semi-structural Sunroof module components, Sunroof frames in particular, typically need to meet a wide range of technical requirements, with a clear focus on integration of functions, safety, cost and weight reduction. The glass-reinforced materials, thermoplastics and thermosets, currently used for Sunroof frames are mostly based on PBT/ASA, PBT, PA, PP and unsaturated polyester SMC. These products are not a perfect match for the application needs of today and the future. Glass-reinforced SMA/ABS on the other hand offers an ideal, unique combination of properties required in Sunroof frames and systems. SMA/ABS-GF compounds such as Polyscope s Xiran® SG grades have clear technical and commercial benefits: • high dimensional stability and precision • very low warpage, compliance to mold cavity shape • good performance at low wall thicknesses • high creep resistance • excellent adhesion without surface treatment • low density, high economic value • good chemical resistance • easy recyclablility with efficient waste streams.
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