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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MICROWAVE ENHANCED FOAMING OF SELECTED POLYMERIC MATERIALS
Microwave heating has a number of advantages in comparison to the conventional method due to the ability to heat a part of polymeric material directly through specific interaction of electromagnetic radiation with selected types of materials. Most thermoplastics are relatively transparent for microwave irradiation and they do not absorb microwaves to a sufficient extent to be heated. In such case, enhanced microwave heating can result from the use of fillers such as carbon black. In this paper, the ability of different thermoplastic polymers as polyurethane, poly(vinyl chloride) and carbon black filled polypropylene to absorb microwave irradiation and to be foamed using chemical blowing agents is discussed. The temperature changes of such materials as the heating effect under microwave irradiation with various power were investigated. Selected polymeric materials with additive of chemical blowing agents were foamed under microwave irradiation and the influence of foaming conditions on cell structure and apparent density of porous products was analyzed.
UPGRADING PERFORMANCE OF RECYCLED POLYAMIDE WITH ZEMAC®
Polyamides are widely used in many applications. There is a vast amount of recycled polyamide coming from the carpet and textile and other industries. Due to degradation and loss of viscosity, this recycled polyamide has reduced performance and limited its use. The unique chemistry of alternating copolymers of ethylene and maleic anhydride provide several advantages for upgrading recycled polyamide. This paper discusses the results obtained with compounding prime grade polyamide as well as recycled polyamide with the addition of small quantities of this copolymer and specific property improvements for applications in injection molded compounds.
GRAPHICS ON PLASTICS - A REFERENCE GUIDE
Processes to print, stamp, mark, label or otherwise deposit graphics onto molded plastic products are collectively known as plastics decorating. Given decorating processes, graphic types and production requirements, no single decorating method fits all projects and, conversely, most projects have more than one viable decorating method. For your latest new product design or redesign, one challenge is determining which decorating processes are options. This challenge is an equation of sorts with several factors to consider including: 1. graphics details required; 2. molded plastic part characteristics; and 3. production demands. The following pages guide a discussion of these factors.
MATERIAL TESTING AND QUALIFICATION FOR TODAY’S ADVANCED MEDICAL DEVICES
Although the process of selecting the right polymer for new medical devices has not changed very much in the last 10 to 15 years, the degree of complication seems to have grown exponentially. The variety of specially designed materials, the number of suppliers, some under the same name or others with a new corporate moniker, and the availability of reference databases puts a glut of information into the hands of the design engineers. But how does one successfully navigate through this information and decide on the one material that is best for their particular application. It is much more difficult to find live technical support from either suppliers or from database providers. With staff reductions and department consolidations, many companies have also lost experts from their library of specialists that in the past have led the selection of the optimum polymer for new applications. No longer do companies have the historical databank of material expertise or on-staff resources for guiding new project efforts. The level of experience in many companies is down while the breadth of knowledge is much more focused. This coupled with the evolution of far more complicated devices that often combine advances in multiple new technologies such as conductive polymers, shape memory materials, drug eluting devices and polymers that dissolve in the body all complicate the process of selecting the right polymer for the application. Medical devices designers and engineers are tasked with selecting just the right polymer for their devices; and this requires keeping in mind all the various requirements that must be satisfied including functional requirements, chemical and biological requirements and manufacturing, assembly and sterilization. Collectively, results of the evaluation of the materials used in the construction of medical device and the function of the devices together contribute to what many refer to as the biocompatibility of the device.
RHEOLOGICAL CHARACTERIZATION OF MELT MIXED PCL - MWCNT NANOCOMPOSITES PREPARED AT DIFFERENT MIXING SPEEDS
Composites of poly(caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were produced by melt-mixing in a small scale compounder by varying the screw speed between 25 and 400 rpm at a constant mixing time of two minutes. By that, different levels of dispersions, as assessed by quantitative analysis of area ratio of remaining primary agglomerates from light microscopy, were achieved. With increasing screw speed the state of dispersion increases and levels off starting at about 100 rpm. Melt rheological properties were measured in frequency sweeps. Interestingly, distinct differences in the complex viscosity * and the storage modulus G’ were found in dependence on the agglomerate area ratio, whereas the loss modulus G’’ was not much influenced. The storage modulus at 0.1 rad/s initially increased with decreasing area ratios, showing that especially the storage modulus is very sensitive to the nanotubes dispersion state. It increased up to a mixing speed of about 75 rpm illustrating improved dispersion followed by a decrease when further increasing the speed. As GPC investigation showed no significant differences in the degradation of the PCL matrix depending on the rotation speed, the effect of decreasing rheological parameter was assigned to nanotube shortening. Both effects improved dispersion and nanotube shortening are also reflected in the electrical resistivity values of compression molded samples. Here, up to 75 rpm a decrease in resistivity due to the better dispersion was observed, whereas above 75 rpm, where dispersion had leveled off, again an increase was found reflecting the reduction in nanotube aspect ratio. Thus, it could be shown that rheological measurements are suitable to detect differences in the dispersion state in composites with a fixed type of CNTs and concentration but also the effect of nanotube shortening reflected in lower aspect ratios.
Low Smoke Polyphenylene Ether Blends for Building and Construction and Transportation Applications
Recent statistics on building fires show that smoke and toxic gases emitted due to burning of materials are much more harmful than the fire itself posing serious health hazard and sometimes fatal to the occupants1. It is for this reason, that many governing and regulatory bodies have laid Fire, Smoke and Toxicity (FST) standards for the use of plastics in public buildings and transportation in Europe, as well as the rest of the world. High-end engineering plastics like polysulphones are well known2 for their low smoke and flame retardance performance according to various standards, but their high cost could limit their use in certain areas of application. This work is an attempt to overcome these cost limitations by using an innovative technology and presents the development of a new poly(arylene ether) resin (PPE) based low smoke, flame retardant, halogen free, Noryl® NI-160 I OB resin (from here-on refe1Ted to as PPE+PS blend) that meets many of the FST requirements applicable to building codes and mass transit bodies in Europe and America. PPE resin is usually modified with polystyrene (PS) [ either crystal polystyrene (CCPS) and/or High Impact Polystyrene (HIPS)]. The PPE+PS blend utilizes a proprietary eco-friendly smoke suppressant technology that helps build robust char during its combustion. The robust char is believed to play a role in reducing smoke while maintaining outstanding flame retardancy and low toxicity. In addition, the PPE+PS blend offers advantages in terms of good proccessability, good mechanical and them1al properties, and low specific gravity.
DEFORMATION AND FAILURE MECHANISMS IN POLYOLEFINES AND THE ROLE OF THE ENTANGLEMENT NETWORK
The occurrence of two brittle ductile transitions is explained in terms of craze propagation and craze-crack transition models. The first and most familiar transition occurs at low temperatures and high strain rates and it is linked to chain scission. The other less well known transition occurs at elevated temperatures and low strain rates and is linked to molecular disentanglement. The importance of the entanglement network for these transitions is highlighted. The relation between these transitions and the molecular mobility transitions such as the glass transition and the -relaxation are discussed. Strategies for increasing the crack propagation resistance are reviewed. The present paper is taken from the authors’ feature article that appeared recently.
CHARACTERIZING HIGH IMPACT POLYPROPYLENE BY MULTIDIMENSIONAL CHROMATOGRAPHY
High impact polypropylene (hi-PP) shows consistent growth rates, with the automotive industry being a main driver behind this. The fractionation of hi-PP into the individual components is essential to establish structure«property relationships. High temperature two dimensional liquid chromatography (HT 2D-LC), which couples a separation according to composition by high-temperature high performance liquid chromatography (HT-HPLC) with a separation according to molar mass by size exclusion chromatography (SEC) opens fundamentally new perspectives to characterise the molecular heterogeneity present in hi-PP. For the first time a separation of the amorphous EP rubber fraction according to its chemical composition becomes possible. The HPLC separation uses porous graphite as stationary phase and gradients of high boiling solvents as the mobile phase. Starting from the separation of EP model copolymers it is shown how commercial hi-PP can be chromatographically separated in a comprehensive way.
IMAGING TECHNIQUES: INNOVATIVE TOOLS FOR FAILURE ANALYSIS
The loss of stabilizing additives is a crucial elemental step in the ageing of polymers. However, the approach currently used to determine the spatial distribution of antioxidants in finished or semi-finished products of polymers is extremely limited with regard to spatial resolution and reproducibility. Infrared microscopy offers an extremely powerful alternative with regard to both these criteria: Using infrared microscopy the extraction of the phenolic long term stabilizer Irganox 1010 from the wall of polypropylene pipes can be monitored. Carrying out IR-microscopy in a quantitative manner enables to determine the temperature and pressure dependent diffusion constants of the stabilizer. The same approach also allows to monitor the loss of Irganox 1010 from the surface of polyethylene pipes as a result of weathering. A quantitative relationship between the loss rate and the radiation dose can be established.
NEW HIGH HEAT POLYCARBONATES FOR AUTOMOTIVE LIGHTING APPLICATIONS
Trends in Automotive Lighting towards increased design freedom, weight reduction and lower system costs have resulted in an increased usage of thermoplastics. SABIC Innovative Plastics recently introduced its Lexan* XHT resin portfolio, a family of new transparent high heat polycarbonate copolymers. These resins can withstand elevated temperatures existing in close proximity to the light source and, as such, are suitable for usage in both metallized bezels and transparent lens applications. This paper will demonstrate the excellent metallization characteristics, weatherability and long-term color and property retention of these resins. Finally, other potential applications of Lexan* XHT resins will also be discussed.
EFFECT OF COMMON STABILIZERS IN THE LONG-TERM HEAT AGEING PERFORMANCE OF POLYETHERIMIDES
A fast method was develop to predict the macroscopic properties of molded resin specimens tested in the Underwriting Laboratories (UL®) Relative Thermal Index (RTI) test (tensile strength retention) with microscopic properties that can be easily measured (molecular weight). By using higher temperatures than employed in the UL RTI protocol, accelerated ageing can be achieved in pellets. Polyetherimide (PEI) resin was spiked during extrusion with common stabilizers. The analysis focused on melt stability, rheology and long-term heat ageing performance. Hindered phenol stabilizers were detrimental under accelerated thermo-oxidative ageing of PEI. The use of new stabilizers should be carefully considered.
Enhancing Properties of PP-Impact Copolymers by Chemical Modification
Polypropylene impact copolymers are widely used in automotive applications. They are required to comply with many criteria. Customers demand high-performance materials which also exhibit good aesthetical properties. The challenge is to balance properties as high impact strength, good flow ability and absence of surface defects, like tiger stripes. It is known that peroxide modification whilst increasing the flow ability of polypropylene impact copolymers deteriorates the basic mechanical and aesthetical properties. Work was performed in which a PP-impact copolymer was subjected to peroxide aided chain-scission under simultaneous presence of the co-agent 1,4- butanedioldimethacrylate (1,4-BDDMA). Results show that samples made with 1,4- BDDMA exhibit superior cold impact resistance and tiger stripe performance compared to the materials made with only peroxide. In addition, morphology, molecular weight distribution, and rheological behaviour of the continuous and dispersed phases of the modified PP impact copolymer were studied.
Lexan* Specialties Copolymers - Performance Attributes for Automotive Applications
Lexan* copolymers offer new performance attributes in comparison to conventional polycarbonates by combining building blocks from different monomeric species. In doing so the application space of polycarbonates are expanded to include e.g. weatherability and scratch performance. By improving these attributes on an intrinsic level unique value propositions can be realized which include non-hardcoat or paint-out solutions. This can lead to cost-out opportunities and environmentally friendlier solutions. To emphasize application possibilities in the automotive industry, attributes are considered with regards to scratch, chemical and UV resistance for both Lexan* DMX and SLX resins.
FROM TRADITIONAL MANUFACTURING TO RESEARCH DRIVEN BUSINESS IN PLASTICS TECHNOLOGY USING TAMPERE MODEL WITH STRONG UNIVERSITY CO-OPERATION ASPECT: A SUCCESS STORY OF AN SME
Novel theory and methodology were developed to increase and intensify competitiveness and business activities of companies at plastics industry type SME. As result of research work the model for R&D – Tampere Model - was created. This model is based on four main components - research, networking, university-enterpriseco- operation and technology transfer. This paper describes the Model, its main results in economical and technological terms using a Finnish SME, Vesita Ltd., as business case. The process has developed the company and its business from small local to research orientated and international. This has also led to new hightech products and increasing use of plastics components.
INDUSTRIAL & TECHNICAL PART BLOW MOLDING RESIN AND COLOR CHANGE FOR SHORT RUNS
Many producers of large technical parts are struggling with increasing demands for short-run parts, caused by a trend toward differentiation (more SKU’s), Just In Time (JIT) delivery and multiple colors for consumer appeal. With many large technical machines requiring as much as 8-12 hours of running to switch colors or materials, this is a huge cost and profit drain on processors. This technical paper illustrates the necessary key elements in large part blow molding to tackle these supply chain requirements. It discusses current limitations, and advances in machinery design to enable fast resin and color changes in large industrial machines.
EXTRUDED MULTILAYER STRUCTURES FOR RIGID PLASTIC CONTAINERS
This technical paper illustrates the current state and applications for multilayer containers that package food and consumer products. The paper describes different structures utilized in making containers for varying applications, including demanding barrier requirements. We also discuss how to meet requirements for food processing systems, including hot fill, pasteurization, and retort. Several case studies of multilayer containers currently in the market are shown. The paper includes pictures and diagrams and is designed to serve as an ongoing guide for anyone tasked to determine appropriate container manufacturing processes, container designs, and material configurations to meet various barrier and post-filling requirements.
A PHENOMENOLOGICAL CONSTITUTIVE MODEL FOR STRAIN SOFTENING PREDICTION IN SEMI-CRYSTALLINE POLYMERS
Strain softening in semi-crystalline polymers, is one of their most important viscoelastic characteristics and these materials are very sensitive to temperature and strain rate. A new phenomenological model with strain, strain rate and temperature dependence on stress was developed based on the Gsell & Jonas model with a new expression used to predict the strain softening phenomena, completing the whole mechanical behavior of polymers from initial strain, strain softening and part of the strain hardening. Model verification was performed on four materials and it was developed to further study the complex deformation patterns in thermoplastic materials subjected to impact loads
TRANSIENT MOLD COOLING SIMULATION FOR THE INJECTION MOLDING PROCESS
In recent years, injection molding technologies have been developed which use variable mold heating and cooling to increase part quality without significantly increasing cycle time. These processes are not suited for simulation with a conventional steady-state (cycle-average) mold thermal analysis. This paper presents the development of a new 3D finite element based transient mold cooling simulation capability which includes coupling the mold thermal solution with the mold filling and packing simulation. The predicted transient mold temperatures are validated against measured mold temperatures for two instrumented injection molding trials.
NANOMINERALS & NANOOXIDES
Nanoclays have to intercalate and exfoliate. The extent of intercalation and exfoliation is not understood by the processing industry. Researchers have to develop and nanoclay manufacturers have to supply a product which can intercalate and exfoliate to achieve the desired performance of the final product. The nanoclay powder which is supplied has a BET surface area of 5m2/gm or less. To disperse such a powder from 5 to 750m2/gm is difficult. To salvage such a situation, there has been a relook at minerals which are platey such as talc and mica. The finest talc supplied in the world has a BET surface area of 15m2/gm. It is possible to further grind this talc (also mica) along the basal cleavage to 100m2/gm to 200m2/gm. Such talc, if added to polymers can improve properties.
LIFE CYCLE ASSESSMENT OF METALLOCENE POLYETHYLENE IN HEAVY DUTY SACKS
The substitution of plastic for more traditional materials stems from its reliability and affordability. However, with the heightened awareness on sustainability, plastic from fossil sources are sometimes perceived to adversely impact the environment. In an effort to address this issue, a detailed life cycle assessment of heavy duty sacks made from metallocene polyethylene (mPE) has been completed. The sacks are used in packaging powdered products for the construction industry. The results show that these sacks have several positive attributes and in many instances, may be a preferred alternative from a sustainability perspective. In fact, in manufacturing, transportation and handling mPE sacks are shown to consume significantly less energy and emit less greenhouse gas than paper-based alternatives. Additional environmental benefits will be discussed.
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