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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FUNDAMENTALS AND PRACTICE OF PLASTICS FAILURE ANALYSIS
It usually comes as a surprise when a plastic product fails. Plastics are made to succeed, not to fail. Sometimes the financial liability can be high, such as a waterline break that is not detected and causes major property damage. If there is a fatality due to plastics failure, criminal charges may be brought. A company can be forced into bankruptcy by plastics failure. So answering the question "why do some plastics fail and others don't" is of major importance. The answer involves choices of material (chemical composition, molecular weight and intermolecular order), design, processing and service conditions.
STRESS-INDUCED CRYSTALLIZATION OF A METALLOCENE HIGHDENSITY POLYETHYLENE
The final mechanical properties of a plastic product which is made of semi-crystalline polymers depend significantly on the molecular properties and the applied processing conditions. Particularly, the formation of flow induced structures via polymer crystallization plays a major role in defining the final attributes of the product. In this paper, the effects of shearing, uniaxial extension and temperature on the flow induced crystallization of a high-density polyethylene (HDPE) are examined using rheometry. Extensional flow found to be a stronger stimulus for polymer crystallization compared with that of simple shear. Generally, strain and strain rate found to enhance crystallization in both simple shear and elongation at temperatures around the meting point. At temperatures well above the melting point, polymer crystallized under elongational flow while there was no crystallization under simple shear flows.
SOLUTIONS WITH UV-CURING PAINT TECHNOLOGY FOR DIFFERENT BUSINESS UNITS
UV-curing paint technology is known since many years e.g. in the field of wood application or in the area of plates and blanks. Today it is also getting more and more common for automotive and decorative applications starting with new improved technologies also to paint 3- D parts. The new Dual-cure paint system of PETER-LACKE combines the advantages of the very fast drying and excellent scratch resistance of a UV-curing paint system with the 3-D painting ability and physical properties of a conventional thermal cured PU-paint system. A dual-cure piano black system was launched e.g. for the new Audi A8 Interior. The UV-Mono-cure systems – just cured by UV-light – give additional to the very short cure time of just a few seconds the advantage of very low or no emissions. Many colours and effects are possible in both UV paint systems and can be used on various plastics as well as on metal or glass.
COATINGS ON TRANSPARENT PLASTICS FOR AUTOMOTIVE APPLICATIONS
Transparent thermoplastic polymers hold an important position as materials for optics as well as for automotive glazing. However, soft plastic parts need to be protected by coatings. For optical applications especially antireflective coatings are inevitable. A presently wellestablished coating system for plastics is plasma ionassisted deposition. Special efforts are essential to find out the best coating conditions for each type of plastic. A comprehensive understanding of complex interactions between the plasma and the different polymer materials is a key factor for the development of coating strategies. Some coatings on polycarbonate for automotive applications will be discussed for example.
Surface Modification Techniques for Optimizing Adhesion to Automotive Plastics
Automotive plastics with a low polarity, such as PE, PP, TPO, POM, PUR and PTFE typically require surface treatment when decoration is required. Metallic surfaces may also require cleaning to remove low molecular weight organic materials prior to decoration. Once the above-mentioned interior and exterior grades of substrate surfaces are cleaned and activated, printing, gluing and painting are possible without the use of adhesion-promoting primers. This paper describes the latest innovations in three-dimensional surface treating technology for plastics finishing which address the need to advance adhesion properties, increase product quality, and achieve environmental objectives within the automotive industry. These innovations include advanced thermal and non-thermal discharge treatment processes for raising the polarity of surfaces to be painted, bonded, decorated, laminated, printed, or to have tape applied.
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.
Interlaminar Fracture Toughness Of Carbon Fabric Reinforced Epoxy Composites
The Mode I and Mode II fracture behaviour of three carbon-epoxy composite laminates with different fabric reinforcement and different matrices was investigated. Standard Double Cantilever Beam (DCB) and End Notched Flexure (ENF) delamination tests were performed to determine initiation toughness and to asses the subsequent crack propagation behaviour. Various toughening mechanism, acting at the microscopic level and responsible for the stick-slip propagation behaviour observed, have been identified. The effect of temperature in a range from -60° to 165 °C was investigated.
A COMPREHENSIVE STUDY OF LOW-DENSITY POLYETHYLENE IN CAPILLARY FLOW
The capillary flow of a commercial LDPE melt was studied both experimentally and numerically. The excess pressure drop due to entry (Bagley correction), the compressibility, the effect of pressure on viscosity and the possible slip effects on the capillary data analysis have been examined. Using a series of capillary dies having different diameters, D and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted both with a viscous model (Carreau-Yasuda) and a viscoelastic one (K-BKZ/PSM model). Particular emphasis has been given on the pressure-dependence of viscosity, with a pressure-dependent coefficient βp. For the viscous model, the viscosity is a function of both temperature and pressure. For the viscoelastic K-BKZ model, the time-temperature shifting concept has been used for the non-isothermal calculations, while the time-pressure shifting concept has been used to shift the relaxation moduli for the pressure-dependence effect. It was found that only the viscoelastic simulations were capable of reproducing the experimental data well, while any viscous modeling always underestimates the pressures, especially at the higher apparent shear rates and L/D ratios.
Closing the gap between Polypropylene and Polyamide Composites with New Silane Grafting & Crosslinking Technology from Dow Corning
Polypropylene grafting with α,β-unsaturated carboxylic functional-silanes by melt reactive extrusion processing in presence of free radical initiator was demonstrated while preventing significantly undesired degradation. Such modified PP was then used for enabling crosslinking into an injected part of neat PP resin, and enhanced coupling in glass- or cellulose-fibers reinforced PP composites. After testing composites at high temperatures (80-120°C), significant improvements were seen on tensile, flexural, and impact resistances – in particular stability upon heat, water and oil aging. Relevance of this work will be discussed against applications in Automotive, Appliance, and Building where glass-fibers reinforced polyamide or polyester is often over-engineered.
PRODUCTION OF A FUNCTIONAL 3D – PLASTIC PANE
In the last few years the use of plastics as a replacement of glass has increased many times over. Especially in the automotive industry more and more panorama roofs and side windows will be made out of polycarbonate and PMMA in the near future. Major advantages are a weight reduction and an improved processability in regards of the three-dimensionality . The integration of certain functions in these plastic panes is the next step towards manufacturing innovative plastic products. This research project is about the integration of an electrochromic system which is able to change its color and therefore its level of transparency by applying a voltage.
SYNTHESIS OF ELASTOMERIC PHENOLIC RESINS WITH IMPROVED TOUGHNESS AND FLEXIBILITY
Novel phenolic resins (PF) with improved fracture toughness and flexibility properties were synthesised and evaluated. A first modification consisted in the copolymerization of Phenol with a natural renewable component (Cardanol) during the synthesis of PF resins (CPF). An increases in the content of Cardanol resulted in a proportional increases in the flexural strength and in the fracture toughness together with a decreases in the flexural modulus of the cured CPF/PF blended resins. Further increased plasticizing and toughening effect was observed by the blending of the CPF/PF resins with propylene glycol (PG).
DETERMINING THE MORPHOLOGY OF CHEMICALLY FOAMED PIPE COATING USING IMAGE SEGMENTATION
A method for rapidly characterizing the shape, size and distribution of bubbles in foam has been developed. The method is based on the extraction of bubble shapes from high resolution images of microscopy slices of the foam, using image segmentation. The foam studied is the 30 mm thick high impact polystyrene coating of a thermally insulated pipe. The coating is applied using extrusion with a chemical foaming agent and the image segmentation provides a dataset with the ellipse fit of 500.000 bubbles.
SIMULATION AND EXPERIMENT FOR SHEET METAL BENDING WITH RUBBER PADS
The paper presents a theoretical and, at the same time, an experimental approach to sheet bending with pads made of rubberlike materials. Numerical simulation for V bending was carried out by using the ABAQUS/Standard software package. The program takes into account the following: sheet material, pad material, punch stroke and punch radius. The theoretical results are compared with experiments in order to determine whether the numerical simulation is close to reality and whether it gives correct information about the process even in the area that can’t be reached by experiments. Some statistical tests were performed in order to validate the results. Moreover, a proposal for replacing rubber with plasticized PVC using two different recipes was made.
LOOK UPSTREAM TO AVOID ‘GIGO’ PITFALLS IN EXTRUSION
The American phrase ‘garbage in, garbage out’ (GIGO for short) succinctly describes a problem often faced by plastics extrusion processors worldwide: No matter how well an extruder extrudes, its output will not be on-spec if the input blend is off-spec. When formulation problems do arise, the on-line proportioning system draws initial troubleshooting focus. But the problem itself (or its underlying cause) may lie elsewhere, farther upstream. This presentation systematically addresses the major process operations prior to extrusion (and beyond to include the materials themselves) in an effort to indentify and avoid the various pitfalls that may plague reliably accurate formulation.
3-D COMPUTER SIMULATION IN MICRO- AND NANO-MOLDING
3-dimensional FEM simulation was performed to clarify the mechanism on surface replication in micro-injection molding and thermal nanoimprinting. Especially the filling behavior into micro- and nano-surface features was discussed in comparison with the experimental results. The simulation results and the experimental results of injection molding show possibility of the generation of air traps in the filling stage and it is considered that those air traps have a strong relation with replication shape and replication rate. The simulation results of thermal imprinting clarified penetration behavior of polymer melt into nanosurface feature and show that the aspect ratio of the cavity and imprinting pressure influenced flow behavior in thermal imprinting.
CBT AS A NOVEL MATRIX MATERIAL AND ITS PROCESSING TECHNIQUES FOR COMPOSITES
Cyclic butylene terephthalate (CBT) is a novel thermoplastic matrix material for composites. Besides its low viscosity (0,02 Pas) and superior mechanical properties CBT has some other advantages over conventional matrix materials. During its polymerization no by-product is being made and it is easy to recycle. But processing of CBT is complicated and may results in a brittle material. Polycaprolactone (PCL) as an additive for CBT will also be introduced to increase toughness. In this paper the proper amount of PCL is determined to obtain a ductile material and a method is described how to fabricate prepregs and composites.
EFFECT OF MISALIGNMENTS OF A POLYETHYLENE CIRCULAR NOTCHED BAR SPECIMEN ON THE ASYMMETRIC FATIGUE CRACK GROWTH BEHAVIOR
In this study, the effect of various misalignments of the circular notched bar (CNB) specimens on the fatigue crack propagation behavior of pipe grade polyethylene is investigated by three dimensional numerical analyses. The effect of the asymmetric crack growth of the misaligned CNB specimens on the lifetime to failure is also addressed. Two types of misalignments of the CNB specimen, i.e., (a) a concentric misalignments (Case I) and (b) an angular misalignments (Case II), are considered using finite element analysis. It is observed that as the misalignments increase, the asymmetric crack growth is accelerated so that the time to reach the critical SIF decreases. Therefore, it can be understood that the lifetime to failure of CNB specimens can vary noticeably once the CNB specimen is misaligned initially. Considering results from this study, the fatigue crack growth behavior including the estimation of the lifetime of CNB specimens should addressed by considering the misalignment effects.
CHAIN EXTENSION OF RECYCLED POLYAMIDES : HOW TO INCREASE THE AMOUNT OF RECYCLED PA IN THE AUTOMOTIVE INDUSTRY
The present work attempts to implement reactive compatibilisation of blends of recycled engineering plastics, more particularly the case of recycled PA66 contaminated by recycled PA6. Low molecular weight, high Tg Styrene-Maleic Anhydride copolymers were tested as chain extenders / compatibilizers. It appeared that the addition of 2% by weight of SMA to an incompatible system of recycled PA6 and PA66 improved both ductility and impact performance by factors of at least 10 and 1.5 respectively. Moreover, high Tg SMA improved performances at elevated temperature, partly due to its ability to effectively crosslink but also because of its inherent heat resistance.
ULTRAMID® ENDURE – STAYS COOL EVEN WHEN IT IS HOT
New Ultramid® Endure from BASF is the first of its kind PA66 based polymer which has excellent heat ageing resistance,welding strength after heat ageing and good processing properties. Ultramid® Endure can withstand continuous use over 3000 hours at 220°C and temperature peaks upto 240°C. The excellent heat ageing properties of Ultramid® Endure allows it to be used for applications such as resonator, charge air lines etc.
TRANSPORT PARAMETERS OF DEACTIVATED POLY-(ORTHOAMINOPHENOL) FILM ELECTRODES
Poly(o-aminophenol) (POAP) films were deactivated and then reactivated, and dependences of the different charge-transport and charge-transfer parameters on the degree of deactivation (c) were obtained by employing Electrochemical Impedance Spectroscopy. These dependences were extracted when the polymer contacts an electroactive solution and a mediation reaction occurs at the polymerelectrolyte interface. While some parameters, such as interfacial metal-film and film-solution resistances (Rmf, Refs, Rifs), the high-frequency capacitance (CH) and the redox capacitance (Cp) exhibit a continuous variation without hysteresis between deactivation and reactivation processes within the whole c range, others, such as electron and ion diffusion coefficients (De, Di), show hysteresis between consecutive deactivation and reactivation processes. On the basis of these findings it was considered that while some parameters of the polymer only depend on the amount of redox active sites, others (De and Di) depend on both the quantity and distribution of redox active sites.
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