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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Optimizing Pipe Extrusion Dies Using CFD Simulation
The extrusion of polyolefin pipes suffers degradation due to mechanical design problems of the extrusion die that is commonly used. This study uses numerical and computational approaches to detect problematic areas in the die geometry. Simulations show that in the conventional die there are areas of stagnation and recirculation of the melt flow, resulting in greater residence times, one of the main causes of degradation. This study introduces the use of novel profiles, which reduce stagnant flow regions, recirculation events, and can optimize the pipe extrusion process. Additionally, this study illustrates a methodology based on residence time distribution (RTD), a parameter that can be applied in optimization of the tooling and equipment in extrusion processes.
Effect of Poly(Butylene Adipate-Co-Terephthalate) Contents on Crystallization and Mechanical Properties of Polymer Blends of Poly(Lactic Acid) and Poly[(Butylene Succinate)-Co-Adipate]
The effect of poly(butylene adipate-co-terephthalate) (PBAT) contents on crystallization and mechanical properties of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) blend was studied. PLA and PBSA were blended in a twin screw extruder, which incorporated PBAT as a ternary component in PLA/PBSA blend. The ratio of PLA/PBSA was set at 80/20. The contents of PBAT were varied from 0 to 50 wt%. The thermal properties and crystallization behavior of PLA/PBSA/PBAT blends were analyzed by differential scanning calorimetry. The effect of PBAT contents on non-isothermal crystallization kinetic of the composites was investigated by using Avrami equation. Tensile modulus and tensile strength of the PLA/PBSA blends decreased when increasing PBAT contents. It can be noted that the addition of 20 wt% PBAT showed the maximum impact performance of the PLA/PBSA blends.
New generation of potable Noryl resin grades for Fluid Engineering
New generation of potable water certified Noryl™ grades for Fluid Engineering Noryl™ resins include blends containing Polyphenylene Ether (PPE) and crystal clear Polystyrene (ccPS) and/or High Impact Polystyrene (HIPS). Noryl™ resin has been used in fluid engineering applications already since 1969 in various applications (water meter housings, impellers, faucets, pumps, etc.) due to its excellent hydrolytic stability and low water absorption. Over the years, the applications requirements changed, new applications evolved, and changes in legislation happened (food contact & drinking water). For a high demanding application (hydroblock or manifold), Noryl™ resin grade GFN1630V has been successfully used. However due to changes in legislation a re-design was needed in order to be compliant with future food contact and drinking water requirements. The development and more specifically the testing needed to come to the optimal formulation selection will be discussed.
A Novel Continuous Kynar® PVDF Foam Concentrate and Application Developments
Kynar® PVDF and Kynar Flex® PVDF have long been used for many extrusion applications. The need for lighter weight, more flexible product has been of interest for some time, but the lack of the ability to foam PVDF for continuous products has always been an issue. Several batch processes for producing PVDF foam articles currently exist, but filling the need for continuous articles such as plenum rated wire, tube, pipe, film, and stock shapes has continued to be a challenge. Research organizations and industry experts have made several failed attempts to be able to develop a robust foaming mechanism and process for PVDF resins. Finally, Arkema has developed a suitable chemical foam concentrate as well as a robust processing method for many continuous Kynar® PVDF applications of infinite length.
Shape-Memory Behavior of a Polyethylene-Based Carboxylate Ionomer and Compounds Containing Zinc Stearate
Shape memory polymers (SMP) are materials that can change shape when exposed to an external stimulus, such as temperature. Thermally-actuated shape memory polymers can be deformed when heated above a critical temperature (Tc) of a reversible network, and then fixed into a temporary shape when cooled down under stress below Tc. When the material is reheated above Tc, the reversible network disappears and material recovers its original, permanent shape. The permanent shape of an SMP can be provided by chemical crosslinks or physical crosslinks that persist above Tc. The reversible, temporary network is created by physical crosslinks or hard domains that vanish above Tc. The unique properties of SMPs can be used in various applications, such as intelligent packaging, reconfigurable tooling, aerospace systems, biomedical devices, artificial muscles and self-deployable devices. Shape memory polymers were prepared from Surlyn® 9520, an poly(ethylene-co-methacrylic acid) ionomer and its blends with Zinc Stearate (ZnSt). Surlyn® 9520 is a semicrystalline ionomer with a broad melting point in the range 60-100 °C, physical cross-links in the ionomer due to interchain ionic interactions provided a “permanent” cross-linked network, while its crystals provided a temporary network. Although the ionic associations within the ionomer can be used as the permanent network, the critical role of the ionomer is to facilitate dispersion of the FAS and to provide a complementary functionality to the matrix polymer that stabilizes the FAS dispersion and develops the strong intermolecular interactions. Broad melting point due to the different size of crystals in the ionomer that melt at different temperature allowed demonstrating the tenability of shape memory effect in this ionomer. A separate route of achieving shape memory properties of the samples by blending the ionomer with ZnSt was shown. The strong dipolar interactions between the ionomer and a dispersed phase of crystalline ZnSt
Rotational Molding Cycle Reduction by Preheating the Mold and the Polymer Powder
Rotational molding is the preferred and most appropriate method for making large, hollow plastic parts. Its primary advantages over other methods, such as blow molding and twin sheet thermoforming, are that parts are practically unlimited in size and are relatively stress free, since material is not forced into shape. One of the main disadvantages of rotational molding is long cycle times. The objective of this study was to explore methods of reducing the overall cycle time, with an emphasis on reducing oven cycle time. A series of cycles were run to investigate the effect of preheating, mold and polymer powder, on oven time using the mold internal air temperature, an indicator of oven cycle completion time. An overall cycle time reduction will ultimately lower production and product costs, as well as reduce energy consumption.
Effect of part thickness on the potential to induce cold crystallinity in nylon 6,6 injection molded samples
Tensile bars of two different thicknesses were injection molded from Nylon 6,6 under controlled conditions and DMA results compared. Early analysis indicates that cold crystallization can be induced for improved mechanical properties on the 2mm thick samples, but not for the 4mm samples. This is due to the more prominent shear-induced orientation layers inherent in the thinner sample re-orienting during the annealing process. Results indicate there may be applications where the crystalline distribution through the thickness of a part may be critical to the plastic performance in cyclic or thermal load bearing applications.
Sustainable In-Machine Mold Cleaning and Part Deburring & Deflashing Using Dry Ice - Changing the Game Rules with CO2
For plastic processors there is a great demand to increase the productivity of their equipment and the quality of their parts, while maintaining healthy margins. This can be a balancing act between using the most effective technology while working within a shrinking budget. This paper discusses the advantages of dry ice blasting as a replacement for solvent and/or mechanical cleaning for the removal of contaminants from tooling as well as its use to deburr and deflash plastic parts. While the principles discussed herein are applicable to multiple plastics processes (BM, Ext., etc.), the focus of this paper will be on injection molding and the various steel and aluminum mold substrates commonly used. The reader will achieve a benchmark understanding of the role and relevance of dry ice in mold cleaning, part deburring & deflashing and its impact on product quality, production cost, production efficiencies, worker safety and health and environmental responsibility. Research from several industry case studies will be discussed. The results confirm that dry ice cleaning can remove contaminant layers from various common mold metals and is a good alternative to other commonly used manual, abrasive methods as well as successfully deburr and deflash plastic parts.
Bridging the Gap: Using Injection Molding Simulation to Determine Realistic Plastic Tolerances
Dimensions on plastic parts are affected by material shrinkage and can limit the dimensional stability of a final product. Incorporating injection molding simulation into the design and manufacturing process allows companies to better determine the dimensional changes that occur due to molding. Moldflow, an injection molding simulation program, was used to import CAD geometry and select processing conditions to predict part shrinkage. These shrinkage results were compared to measured molded parts to determine variations in dimensions. By understanding the correlation between processing conditions and molded part dimensions, manufacturers can control the sensitivity of the molding process and the ability to maintain products within specifications.
Influence of exfoliated carbon nanotubes on crystal structure and tensile properties of polypropylene
The objective of this work is to investigate the microstructural mechanisms responsible for the observed remarkable increase in modulus and strength of polypropylene (PP) containing only trace amounts of multi-walled carbon nanotubes (MWCNTs). The functionalized MWCNTs were individually dispersed in commercial polypropylene matrix by using our novel nanoplatelet-assisted dispersion approach, followed by compatibilization of MWCNT in a small amount of stabilizing surfactant. We also report on the morphology and dynamic mechanical properties, and propose a novel mechanism for reinforcement of thermoplastic materials with individual MWCNTs.
Study of Interfacial Interactions in Exfoliated Graphite Nanoplatelets/Polyamide 12 Nanocomposites
The interfacial nano-reinforcement -polymer interactions in polymer nanocomposites (PNCs) are key in fabrication of PNCs with engineered properties. Our study showed the presence of an immobilized layer or interphase around nano-reinforcements and investigated possible correlations between interfacial interactions and macro-scale properties of PNCs. Polyamide 12 (PA12) based PNCs reinforced with 0-15 wt% of exfoliated graphite nanoplatelets (xGnPs) were fabricated. The results indicated occurrence of attractive interactions at the interface of xGnP and polymer leading to formation of a stiff interphase a few tens of nanometers thick. The altered dynamics of the immobilized layer was suggested to develop a dominant secondary mechanism contributing to the macroscopic properties of the PNCs.
UV Monocoat: Ad Advanced Coating Technology for Consumer Electronics
Surface coatings on plastic substrates with excellent physical performance, low application cost, and minimum environmental impact are highly desirable for various commercial applications. Here we describe PPG’s ultraviolet (UV) monocoat technology for consumer electronics, which afforded both protection and decoration of plastic substrates with a single-layer colored coating system. Studies demonstrated that UV monocoat applied on plastic computer and cellphone parts successfully met or exceeded customers’ specifications, showing good adhesion to plastic substrates, excellent abrasion and scratch resistance, good chemical resistance, and high weathering stability. UV monocoat also enabled a variety of colors with a wide range of gloss for decoration of plastic substrates. In addition, UV monocoat uniquely combined a single-layer design with UV cure technology, which significantly increased on-line coating capacity and efficiency and dramatically reduced application cost and environmental impact.
ToolingEDGE - High Performance and Sustainable Production
The strong emergence of new" economical and industrial regions on the globe supported by lower hand labor costs puts European Engineering & Tooling face to new challenges that evidence the necessity to develop new and revolutionary ways of making things. It is in this context and to answer to the new global challenges it was created an industrial and scientific Cluster the Portuguese Engineering and Tooling Cluster (E&T). This cluster represents an industrial value chain with specialized skills and competences from Design and Engineering to Tooling and Plastic Products. The E&T cluster is responsible for setting up a national strategy for the development and sustainability of this important economic sector combining a strong investment in technological and organizational innovation that will support a constant and progressive evolution on technical and organizational efficiency. The E&T strategic plan within 10 years is to be recognized worldwide as one of the most advanced in technological point of view and having the capacity to offer added value in the design and production of molds special tools and precision machined parts produced by injection or in materials with specific features for new applications. The R&D project ToolingEDGE - High Performance and Sustainable Production is one example of research activities being held by E&T cluster. The project aims to deploy technological solutions to prepare the E&T sector for sustainable competitiveness and to enable the penetration in new and/or added value markets considered strategic for the E&T notably: the aeronautics medical devices electronics automotive and packaging industries."
In-situ Monitoring of a Gas-Liquid Reaction with NIR Spectroscopy
Fourier Transform Near Infrared (FT-NIR) spectroscopy may be used to analyze industrial processes in- situ. In this case study, FT-NIR data is presented which tracks the reactants and final products ensuing from a catalytic gas-liquid process used for the production of vinyl melamine monomers. This reaction presents an alternate pathway to the polymerization of melamine in lieu of its traditional reaction pathway using formaldehyde, a known carcinogen. The analysis shows changes in rates of reaction and end-product concentrations based on differing temperatures, catalyst concentration, and stirring speed.
The Assessment of Uncertainty in Spectrophotometry
Ideally, manufacturer specifications provide performance characteristics and specifications that can be used to evaluate the suitability of colorimeter and spectrometer measuring and test equipment for a given application. However, understanding specifications and using them to compare equipment from different manufacturers, the quality of products, and its adherence to specifications can be a perplexing task. This primarily results from inconsistent terminology, units, and methods used to develop and report equipment performance specifications. This paper discusses how to determine if manufacturer specifications are adequate for the intended purpose, and how to interpret and assess colorimeter and spectrometer performance and reliability. Recommended practices are presented and an illustrative example is given for combining components values into a specification.
Gas Chromatography Applications in Food Flexible Packaging Covering Food Safety, Process Control, Polymer Additive Analysis and Analysis of New Generation Packaging with a Compendium of Illustrations
Gas Chromatography (GC) is used extensively in Food Flexible Packaging for quick and accurate analysis of solvents retained from solvent based liquid printing inks, adhesives and coatings. This paper covers recent a recent development in Head Space technology, the Dynamic Head Space with Purge & Trap, which ensures complete extraction of high boiling points solvents such as ethyl cellosolve, propyl cellosolve, toluene and methyl iso butyl ketone in addition to low boiling point solvents such as ethyl alcohol, ethyl acetate and methyl ethyl ketone. Identifying all solvents in full measure is critical for food safety. The paper mentions the fast GC concept, with suitable spilt injection ratio, a special shorter length capillary column and Flame Ionization Detector (FID) with high sampling frequency and data acquisition capability which can help in quick analysis for control of speed, drying hood air flow and dryer temperature station wise in printing, lamination and coating. Analysis of the levels of slip and anti-block additives after production of the sealant layer film, after lamination, after curing and post storage needs to be measured for validation and standardization of processes and sourcing of raw materials.GC analysis is relatively fast and simple. Nano-technology is being increasingly used in food packaging for performance improvement. SiOx coating on Bi-axially Oriented Polyester (BOPET) Films improves barrier to levels matching aluminium foil and thereby facilitates see-through packaging. The paper describes a method for analysis of performance of such coatings. The aim of the paper is to help the food flexible packaging industry to fully exploit the capabilities of advanced Gas Chromatography to ensure food safety, optimize processes and enhance shelf performance.
Synthesis and Characterization of Antimicrobial Polyvinyl Pyrrolidone Hydrogel as Wound Dressing Hints
A novel antimicrobial hydrogel (PVP-GP) was prepared by covalently bonding polyvinyl pyrrolidone (PVP) with poly(hexamethylenediamine guanidine hydrochloride). The products were characterized by 1H NMR, FTIR, SEM, and their performances for wound dressing applications were also evaluated. Swelling study showed that the water absorptivity of PVP-GP hydrogels decreased as the crosslinking density increased either in water or in physiological saline solution. The water vapor transmission rates (WVTR) of PVP and PVP-GP hydrogels were in the range of 1727 ~ 2320 g/m2/day, indicating that the prepared hydrogels were suitable for wound dressings without dehydrating the wound surface or accumulating exudates. Kirby-Bauer inhibition zone tests and microbe penetration assay proved that the PVP-GP hydrogels had high antimicrobial activity.
Superior Processability and Economics of Single Site LLDPE vs. Conventional Metallocene LLDPE Blown Films
Over the past 15 years, the polyethylene industry has increasingly focused on metallocene and single-site catalyzed LLDPE as the route to higher performance. Unfortunately, the improvement in physical properties over conventional Ziegler-Natta (Z/N) LLPDE is counterbalanced by a dramatic decrease in output rates which directly impacts the economics of these film structures. To compensate, blown film producers add 10%-20% of LDPE into these resins to the detriment of the film physical properties. A unique class of single-site catalyzed LLDPEs (sLLDPE) has been developed which overcomes the processability issues encountered with the traditional metallocene LLDPE (mLLDPE) resins thus reducing the demand for LDPE and maintaining the enhanced physical property performance. This paper focuses on: The comparison of bubble stability and maximum output of sLLDPE vs. mLLDPE resins. The economic cost associated with mLLDPE vs. sLLDPE in a commercial film structure via a case study.
An Investigation of the Effects of Bound Selection on the Numerical Formulation of Kinetic Parameters
Kinetic modeling is used to predict the rate of conversion of a partially cured thermosetting plastic subjected to catalytic conditions of temperature and pressure. Parameters for these models can be determined from experimental data obtained through differential scanning calorimetry (DSC). In the present study, kinetic parameters are determined from dynamic DSC scans of the Pro-Set 117LV/229 resin system. The primary contribution of this paper is an evaluation of the sensitivity of empirical kinetic parameters to the selection of reaction bounds. This study is performed using a finite difference approach to obtain parameter sensitivity. The results suggest that the kinetic parameters are insensitive to bound selection for this particular resin system. Additionally, the kinetic parameters obtained from dynamic scans are applied to isothermal DSC results, which indicates the importance of the accurate determination of kinetic parameters at low degrees of conversion and the evaluation of diffusion control. The effects of gelation and vitrification are also considered.
Manufacturing Induced Curvature of Carbon Fiber Laminates: Experimental Observation and Model Validation
The use of carbon fiber reinforced composites is becoming increasingly implemented throughout the entire aerospace, automotive and many niche industries, in large part due to their high strength to weight ratios. Unfortunately, effective design of the fabrication process and the final part performance poses increased engineering difficulties over alternative manufacturing approaches. This work focuses on the residual strains that occur within the processed laminate as induced during manufacture. These residual strains are due to a combination of the curing kinetics of the thermoset and the induced thermal strains caused by a coefficient of thermal expansion mismatch for the resin and carbon fiber. In the present paper, we present results for a cross-ply (un-balanced) laminate. We use micromechanical theories to predict the stiffness and the coefficient of thermal expansion of an individual lamina from the constitutive properties for the fiber and the matrix, and couple the lamina results with a finite element structural and coupled thermal-structural analysis to predict the observed macroscopic deformation and curvature of an unloaded processed laminate. The finite element results are compared with the measured results and show exceptional qualitative agreement with experimental observations. Suggestions for improvements on the method are introduced along with a discussion of the need for the quantification of the relevant constitutive material properties for future modeling and experimental studies.
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