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.
Fused filament fabrication (FFF) is one of the most accessible and flexible additive manufacturing processes. However, it is plagued by consistency issues related to material deposition. The role of compressibility is explored with an instrumented nozzle to relate the observed printing pressure to variations in deposited road widths. Variations in road width are analyzed relative to those predicted using a double domain Tait equation (PVT model) for high impact polystyrene (HIPS). Compressibility was found a critical effect, varying the road widths by up to 50% when accelerating and decelerating. The effect of the speed of transient stress propagation was also investigated but found insignificant.
This paper explains the computational model developed in predicting the infrared heating of a composite material component. Computational Fluid Dynamics (CFD) technique is used in predicting heating behavior of a thermoplastic composite component. In-house testing facilities has been utilized to determine the radiation characteristic of the materials. The computational thermal model developed is validated by experimentally measured temperatures at key locations of sample plate during its heating. Comparisons between experimental data and numerical simulations showed good match between model & measurement. The developed model can be used as an effective tool in predicting the heater setting parameters for polymers/ composites heating in different application scenarios.
The research of foam injection molding for thermosetting materials is still in an early stage. Recent studies focused on the process of volumetric underfilling, but open pore structures and gradients over the flow path were obtained. This paper gives an insight into a novel process variant, which makes the production of skin-core structures possible. It is shown, how an expanding mold technique enables the production of components with a solid skin layer and a foamed core in an injection molding process with phenolic resins. In an experimental design, packing pressure time and mold temperature are identified as the main influencing parameters. Their impact on the skin layer’s height as well as the surface quality of the specimen are discussed. Finally, a model description of the processes leading to the formation of these foam structures is proposed.
The costs for degradable plastics are in comparison to bulk plastics still high. To increase the market share of degradable-plastics-based products the reduction of the plastic used itself could be suitable option. To keep the degradable properties of the product suitable materials for a hybrid are wood or woodbased products like carton. In this paper, the combination of wood and degradable plastics to a hybrid material by overmolding was investigated. In this feasibility study the effects of injection molding on wood as an insert and the bonding strength between the two materials was analyzed.
This work concerns the synthesis, characterization and evaluation of enzymatic degradation kinetics in three biobased polymers: poly(hexamethylene succinate), poly(hexamethylene 2,5-furan dicarboxylate) and a copolymer containing hexamethylene succinate (HS) and hexamethylene 2,5-furan dicarboxylate (HF) units. All three comonomers are available from renewable resources, and their use in agricultural films and coatings would reduce the incidence of microplastics in soils, and could also provide functionality in controlled release applications. We find that copolymerization of the aliphatic and aromatic monomers reduces the crystallinity in the polymer, thus increasing the degradation rate.
The effect of simulated sunlight and ultraviolet (UVB) light on the chemical structure and tensile properties of chlorinated polyvinyl chloride (CPVC) was studied. Exposures were conducted in a Q-SUN xenon arc chamber and QUV accelerated weathering tester. CPVC tensile specimens were exposed for 1 week, 4 weeks, 8 weeks and 12 weeks and then analyzed using a tensile testing apparatus and Fourier Transform Infrared (FTIR) spectroscopy. The testing showed the CPVC material exhibited early degradation when exposed in the Q-SUN xenon arc chamber. FTIR analysis showed surface chemical structural changes as early as one week into the exposure and tensile testing showed apparent changes in elongation at break (70 % reduction) after 8 weeks of exposure in the Q-SUN xenon arc chamber (equivalent to 1344 hours of noon summer light) with a day light filter and 67.66% reduction in the elongation at break after 12 weeks of exposure in the Q-SUN xenon arc chamber with a window glass filter. CPVC tensile specimens when exposed in the QUV accelerated weathering tester exhibited discolored or stained surfaces.
The use of foamed polymeric precursors for blow-molding and thermoforming applications is seeing increased use in the world of application development across a wide range of segments such as automotive, appliances, and packaging. Foam blow molding holds great potential for further enhancing lightweight solutions for complex hollow structures, while adding the potential of single-material solutions offering multi-functionality, e.g., thermo-acoustic isolation or damping. Unlike in the case of foam injection-molding, fundamental processing-structure-property interrelationships are not widely researched in the area of foam blow-molding. Modelling, simulations, and predictive engineering of foam blow molding processing are still in their infancy. Any simulation framework for this purpose needs to address the complex interplay between the matrix rheology, foam morphology and morphology evolution, and the resulting processability and thermo-rheological properties of the foamed product. Here, we report a preliminary simulation framework for foam blow molding, demonstrated in the context of foam extrusion blow molding. The framework addresses several important material and processing considerations. These include: (1) the initial foam morphology; (2) the nonlinear viscoelastic characteristics of the foamed melt; (3) the derivation of constitutive parameters for the foam – arriving at a homogenized representation of the foam rheological characteristics; (4) the implementation of blow-molding simulations using these parameters in a commercially available simulation software; and (5) finally correlating the local strains in the blow molded part to its morphology.
Carbon based or inorganic fillers in 3D filament can enhance properties of 3D printed parts and are attracting considerable interest from academic and industry researchers, such as MarkForge, BASF, ColorFabb, and Graphene 3D Lab. Although 3D-tailored composites have been developed, very little work has been done on the production of advanced 3D filament feedstock for FDM. Work is needed on biomedical application filaments which require (i) high filler or nanoparticle loading, (ii) dimensional accuracy and (iii) superior surface finish. Current FDM filaments rarely exceed filler concentration of 10%, for example, in case of calcium phosphate without sacrificing quality. In this work, a melt-spinning die was designed with 2D FEM flow simulations to minimize interfacial flow instabilities. With the die, a co-axial 3D feedstock filament up to 20% filler concentration was spun. Tensile bars were successfully printed with 15% filler content and had similar tensile properties to neat PLA.
This paper will present the conceptual design of a novel free-rotating mixing sleeve for single screw applications. In contrast to most of the currently available free rotating mixing rings (e.g. the TMR) which primarily have a distributive mixing effect, the mixing sleeve presented in this paper will focus on dispersive mixing. The variety of requirements on dispersive mixing make the structural design and the geometrical layout very complex. Therefore, a method is introduced to couple a full parametric 3D-CAD master model of the mixer with a 3D-CFD-simulation. The aim is to describe a set-up of an automated process to design and optimize the novel mixing element by defining several target figures.
A design of experiments using different nozzle diameters with varying road heights and shear rates (based on print speed) was done using lab-made polylactic acid filament. Subsequent tensile testing and calculation was done to obtain the main responses of ultimate engineering stress and tensile modulus. Linear models were made to determine the significance between the different dependent and independent variables. The main results show that larger nozzles, shorter layer heights, and lower shear rates provide stronger, heavier and stiffer fused filament fabrication parts.
The objective of the overall project is to conduct applied research that will lead to the development of an innovative agile manufacturing plant for onsite fabrication of recycled thermoplastic products at the US military’s forward operating bases (FOBs). The proposed manufacturing plant needs to be contained in 20-foot ISO containers for both shipment and operation. A study by the US Department of Defense (DoD) of base camp waste confirmed that the single largest source of waste plastics is Polyethylene Terephthalate (PET) from water and other beverage bottles. The on-going project to convert waste or reclaimed PET (rPET) to useful products is currently being conducted by Emc2 and the US Army Corps of Engineers and is being supported by the DoD’s Strategic Environmental Research and Development Program (SERDP) as a three year effort starting in June 2018.
The development of a high stiffness Polypropylene (PP) foam for use within the rotational moulding industry has been investigated by Matrix Polymers. The scope is to offer a stiffer and more advanced alternative to the current Polyethylene (PE) foams which are on the market. Matrix Polymers want to push the boundaries of current products and combine new technologies to produce a new material. Differing compositions of CBA (chemical blowing agents), various dry blends and compounds have been trialed alongside experiments into the CBA reaction time and expansion ratios. The availability of K-kord temperature logging equipment has been utilized alongside JUST RITE temperature labels, static oven machines and a rotational Ferry machine to develop the new material. All of the above has furthered understanding into the astonishing potential of this new material. Offering this product to the rotational moulding industry would be greatly beneficial to rotational moulders from around the world in a variety of applications, we understand the limits of rotational moulding are the lack of suitable polymers. This is something that Matrix continues to challenge.
Increased demands on high-end materials focus the development on new functionalities such as biocidal effects, which are made possible by property changes in the nanoscale range of existing materials or by a combination of different material classes. Therefore nanoparticles, based on transition metal oxides have been synthesized in order to reach biocidal properties on plastic part surfaces. The influence of the nanoparticles on the thermal and mechanical properties have been characterized as well as the biocidal properties of the plastic part surfaces and of the nanoparticles itself.
Shape memory polymers represent a family of stimuli-responsive materials that can be used in many applications. Polylactic acid (PLA) is a type of shape memory polymers that is biocompatible and biodegradable. By blending PLA with thermoplastic polyurethane (TPU), its shape memory effect would be improved. This study aims to optimize the shape memory effect of TPU/PLA polymer material systems and investigate the influence of material compositions and processing conditions on their shape memory effects. Blends were fabricated with different compositions and/or different thermal history. Experimental results revealed that the addition of TPU increased the recovery but decreased the fixity at the same time. Overall, the 65/35 TPU/PLA blend has the best shape memory performance. The duration of stretching at the transition temperature in the process of the test of the shape memory properties influenced the crystallization of samples. The sample could show a bad shape memory effect if the stretching time is too long.
In the plastic industry, the modification of polymers with glass or carbon fibers is common to improve the product quality and properties. Particularly, the twin screw extruder is frequently-used for continuous compounding, preparation and processing of polymers. The steadily growing demand for fiber-reinforced thermoplastics and the high cost of the carbon fibers are the motivation for recycling. Furthermore, new laws (e.g. EU Waste Framework Directive and End-of-Life Vehicle Regulation) demand the recycling of the remains and the waste of the carbon fiber production.
The effects of high-shear flow on cellulose nanocrystals (CNCs) were studied to characterize potential impacts of industrial processing on these materials. A microcapillary rheometer was employed to study the rheological characteristics ofaqueous CNC suspensions at concentrations ranging from 1.5 wt% to 12.1 wt%.Increased cellulose content in the suspensions produced increased viscosities. A Sisko model was successfully fit to the data which display high shear Newtonian plateaus. Shear rate sweeps at these concentrations failed tofullyreduce to a master curve. Furthermore, repeated testing of the same sample volume at nearly 800000 s-1led to a permanent decrease in viscosityfor all samples.Atomic Force Microscopy (AFM) probed CNC morphology to observe any changes in the CNC dimensions which may have contributed to this phenomenon. AFM resultsindicate significant decreases in both height and length of the CNCsafter repeated testing at high shear rates.
As sensors evolve, their application has expanded. Mold related processes and technologies have become a focus of technology research and development. Mounting sensors in the mold cavity has become a trend in recent years. Since heretofore data has largely been limited to feedback data from the injection molding machine, control of the sensor data is the key to exploring the filling behavior of the molten melt in the cavity.In this study we created a dynamic variable-gate design in the mold. In combination with sensors to collect real-time data in the mold cavity during the injection stage, experiments were conducted to explore the course of shear heat and pressure drop generated by the melt passing through the gate when the gate thickness is varied. Therefore, the dynamic variable-gate design parameters such as gate thickness, advance delay time, and forward distance are discussed herein. To understand whether the gate thickness changes in the injection process, the influence of different parameters on the product shrinkage, product weight, and tensile strength are explored.
Three-dimensional finite element method (FEM) modeling has been carried out in this study to investigatethe scratch-induced surface deformation and damage mechanisms in composite coatings applied on polymer substrate. Composite coating systems with anisotropic properties and variation in thicknessare considered in the numerical framework to study the influence of coating anisotropy and layer thickness on scratch behavior. The results show that coating anisotropysignificantly affectsthe scratch resistance of coating systems. Implications of the numerical findings on scratch resistance of coating systems are discussed.
The effect of long-chain branching (LCB) on scratch behavior of polypropylene (PP) was investigated. In this study, the model LCB PP samples were modified viareactive extrusion process by incorporating increasing amount of polyfunctional monomerin PP. Small amplitude oscillatory shear results show that LCB level in PP increases with increasing polyfunctional monomer introduced. Moreover, increasing LCB content slightly improves the tensile strength of PP. ASTM D7027/ISO19252 standard scratch test was employed to determine the scratch resistance of the model LCB PPs. It is found that incorporation of LCB delays the onset of fish-scale formation.
Bioprinting, a subset of additive manufacturing, utilizes bioinks, which is a combination of biomaterials and live cells, to produce functional tissue. Soybean oil is a plant polymer with promising biomaterial properties for development as a bioink. Soybean oil is low cost, has excellent biodegradation, biocompatibility and low immunogenicity.Additionally, suboptimal soybean properties such as mechanical and bioactive properties can be altered and improved when combined with other polymers. The curing of resins formulated from a combination of soybean oil epoxidized acrylate and poly(ethylene glycol) diacrylate was investigated with different concentrations of the photoinitiator diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide/2-hydroxy-2-methylpropiophenone, blend (DPH) and at different curing times. Visual observations of the cured resins indicated that as the photoinitiator concentration and curing time were varied, the resins exhibited changes in flexibility and rigidity / brittleness.
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