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.
Thermosets and composites can be difficult materials to use in serial production. How do you know what combinations of curing temperatures and time can be used? When is it safe to demold parts? And are the final properties what you expect? Without this information, it is impossible to optimize your cycle times and minimize waste. This webinar will introduce how thermal analysis is being utilized by DarkAero to manufacture high-performance two-seat aircraft and composite structures with a new level of technical understanding and engineering confidence. The material covered will include:
Photolytic and thermal degradation are important processes to the overall sustainability and environmental impact of a flame retardant for a given commercial application. Details on accelerated photolytic aging and recycling studies of ethane bis(pentabromophenyl) (EBP), often called decabromodiphenyl ethane (DBDPE), will be presented.
Due to the viscoelastic flow characteristics of polyethylene (PE) and the interaction of molten PE with metallurgy of a die surface, flow instabilities occur after exceeding a certain shear rate, temperature or mean velocity, which was initially discovered in 1958. This flow instability and melt fracture leads to an undesirable product appearance and can negatively impact product properties due to the emergence of a “sharkskin” morphology of produced film. In addition, melt fracture is one of the first instabilities that occurs at higher throughput, which can limit rates of commercial applications. Although the flow characteristics of polyethylene cannot be modified easily, specialty additives such as polymer processing aids (PPAs) can deposit on the die surface, inducing slip and enhancing flow. With this additional lubrication, die pressure can be lowered and the onset for melt fracture can be delayed, leading to significant commercial rate improvements. Fluoropolymers are ubiquitous within the field of PPAs for polyethylene and incorporate fully-fluorinated carbons to reduce interactions of the molten polyethylene and the die surface. While the efficacy of fluoropolymers to delay the onset of melt fracture is well described, the current regulatory landscape is progressing rapidly for the broad ban of perfluoroalkyl substances, which incorporates fluoropolymers. Although the chemistry and migration of fluoropolymers is quite different than that of perfluorooctanoic acid and perfluorooctanesulfonic acid which bans initially targeted, the current legislations are covering all compounds with at least one fully fluorinated carbon. Regarding plastic packaging, there are multiple states that have passed bans effective in 2023, with additional regulations going through the US and EU that come into effect within the next few years. For converters and film producers to maintain current rates and product morphology, new PFAS-Free technology needs to be developed and implemented within a very short timeframe. This presentation will provide insight into the mechanism at which processing aids lubricate the die and reduce melt fracture, cover academic and literature-based PFAS-Free PPA technologies and deliver an overview into the development of PFAS-Free PPAs at NOVA Chemicals. The performance of NOVA Chemicals fluorine-free PPA technology and efficacy towards melt fracture clearing will be presented alongside the effectiveness of fluorine-free PPA to prevent die lip build up.
The fatigue performance of unidirectional fiberreinforced plastics is subjected to complex damage mechanisms, dependency on the load direction, and straindependent material behavior. In addition, the strength of the fiber/matrix interface is one of the main influential fa ctors on the composites’ fa tigue life. Its characterization, however, is effortful and the results are prone to large scatter. Moreover, the microstructure within the composite leads to a complex stress-strain field that changes with each fiber break, or detachment. So far, this resulting internal stress-strain fields only have been possible to be investigated by numerical approaches. In this work, a single fiber break model was extended to a representative volume element model (RVE) within the finite element method. A composite material made of carbon fibers and epoxy resin is being investigated. The behavior of the two constituents is assumed to be orthotropic and isotropic elastic, respectively. The complex microstructure is represented by a random fiber distribution generated with a sequential expansion algorithm, and periodic boundary conditions are applied. The fiber strength is modeled as a Weibull-distribution. A parameter study is carried out to analyze the influence of the fiber/matrix detachment rate on the internal stress distribution. Principal Component Analysis (PCA) is introduced to reduce the dimensionality of the problem. The obtained results show that PCA can reduce successfully complex stress-strain fields to an eigenvalue and eigenvector problem. Furthermore, the simulations show that the fiber detachment length correlates with the number of load cycles.
Polymer materials are made fire resistant basically by controlling either the bulk properties of polymers i.e., the condensed phase or by controlling the gas phase chemistry i.e., the volatiles that are formed due to polymer degradation under burning conditions or by controlling both. This suggests that if materials could be designed with low specific mass loss rates under fire conditions, the amounts of volatiles formed would be substantially reduced resulting into less combustion and thereby less heat generation. The latter would result into less increase of surface or ignition temperature of the materials resulting into less thermal degradation of materials. This suggests that important parameters that control the condensed phase properties of polymers to make them fire resistant are surface or ignition temperature and the kinetic degradation parameters of the materials. Another parameter that has a great influence on the fire properties is the gas phase chemistry, which in turn, is controlled by the volatiles formed during the burning process. The volatiles formed differs both with respect to flammability and generation of heat of combustion. This suggests that both the total amount of volatiles and the chemical composition of the volatiles formed because of burning are important to improve fire resistance properties of the materials. Therefore, preferred volatile compositions are also presumed to be effectively improve the fire properties of the materials. Furthermore, in phosphorus (P) and Phosphorus-Nitrogen (P-N) based (PFR) halogen free flame-retardant systems, it has been suggested that formation of P and PO radicals in the gas phase are important to obtain good fire-resistant properties because they both function as effective radical quenchers and char formers resulting into less heat generation. For radical quenching presence of phosphorus in the form of P and PO radicals in the gas phase are important. This suggests that distribution of phosphorus both in the condensed and in the gas phase should play an important role in controlling the fire properties. This proposes that selection of suitable PFR compounds that renders a preferred P distribution in the gas and in the condensed phase is important to obtain good fire resistance properties. Unfortunately, quantitative estimations of the above-mentioned parameters are lacking in the literature. In this presentation, we shall present a toolkit to experimentally measure these parameters for different HFFR PP model compounds and their correlations to the UL94V results. The study shows that we obtain a good agreement between these quantitative parameters and UL94V tests. This suggests that our toolbox could be very helpful and effective tool both to characterize and develop new and effective HFFR formulations instead of using single point UL94V tests that are being commonly used today.
Via two-step solid-state foaming using subcritical CO2 as blowing agent, the foamed acrylonitrile-butadiene-styrene/carbon fibers (ABS/CFs) composites are prepared. The results demonstrate that a bimodal cell structure (BMCS) is developed in the foamed ABS/CFs composites. Small and denser cells are developed in the ABS matrix, whereas large cells are formed around the CFs due to concentrated CO2 at the ABS-CFs interfaces. The mean cell diameters are 0.39–0.92 μm for the small cells and 12.5–25.6 μm for the large cells, being dependent on the CFs content. The CFs especially at 10 wt% or higher can refine the small cells via both increasing the strength and elasticity of the ABS matrix and restricting their growth under large cell growth. Interestingly, slow depressurization for the saturated composites followed by foaming is also favorable to refine the small cells, which is mainly attributed to no cells to be preformed in the saturated composite via the slow depressurization. Relatively higher saturation pressure or modest foaming temperature can further refine the BMCS in the foamed ABS/CFs composites.
The extraction of cure-dependent fatigue behavior under tension-tension fatigue is presented for filament-wound coupons. Displacement controlled fatigue tests are performed on tubular filament-wound coupons. The state of the tube is characterized by performing interrupted static tests in between the fatigue cycles. At the coupon level, the state of damage in the matrix is obtained using micromechanics expressions with the help of Digital Image Correlation (DIC) technique. The results show a noticeable difference between fully cured (95%) and 80% cured composite specimens.
The material properties of fiber reinforced plastics are highly directional and the final fiber orientation can usually only be determined after the manufacturing process by time-consuming and cost-intensive sample preparation. The determination of the mechanical properties usually requires destructive testing. Compared to conventional methods, the method of ultrasonic birefringence presented here allows a non-destructive determination of the shear moduli G13 and G23. Furthermore, it allows the determination of the fiber orientation without the need of a complex specimen preparation. The difference in shear modulus measurement between the two methods is less than 1%.
The purpose of this research is to develop measurement devices and verify whether the permeability values obtained by different experimental devices and theoretical models are correct through Moldex3D RTM simulation tool. The experimental mold dimension and process parameters are established in Moldex3D for verification, such as one-dimensional flow and radial flow. From the results, it is known that the experimental and simulation results are highly consistent. Therefore, Moldex3D simulation software can be used as a verification tool to compare the permeability and flow front.
Smart materials that can adapt their mechanical response in the presence of an external stimuli are popular for their applications in 4D printing. Such printing methods exploit a smart material’s capability to interact with these stimuli to impart controlled material deformation tailored to specific applications. A modified percolation model was formulated to predict the dynamic transition exhibited in polymer composites containing cellulose nano-crystals (CNCs) which undergo mechanical softening in the presence of water. Coupling the effects water diffusion to the degree of CNC connectivity provided a method to capture the dynamic softening of CNC-based, water responsive smart materials as a function of filler loading. This modeling approach can be implemented to develop humidity sensing actuators and water-sensitive shape memory devices.
Hybrid materials nowadays are achieving increasing market dominance in the technical segment due to their outstanding mechanical properties. One such hybrid material that is increasingly coming into focus, especially in mobility branch, are fiber-reinforced plastics. They offer the advantage of low weight and high strength. As a rule, generally glass or carbon fibers are embedded in the matrix material. Over the last few years, the demand for fiber-reinforced plastics has increased continuously. Considering the recent changes in the automotive industry, it is expected that this trend will not change in the near future, especially with regard to the weight reduction of means of vehicles.
A new type of nano-cellulose crystal (CNC) has been gaining interest for its unique morphology combined with its as-produced carboxylate functionality: electrosterically stabilized nano-crystalline cellulose (ENCC). When ENCCs are added to thermoplastic polyurethane (TPU) composites and submerged in water they display a unique increase in opacity. Using UV-VIS and DMA, the optical and mechanical properties of these composites can be studied at differing ENCC concentrations.
There has been a common goal among various researchers across the globe to investigate sustainable and high-strength materials as a suitable replacement for metallic materials in many industrial sectors. Many products obtained through reinforcing steel can potentially be replaced with those synthetic fibers such as carbon and glass to overcome the critical issues pertaining to dimension stability along with the creep effect that could pose complications in applications such as belts driving heavy machinery. In the current study, Steel, Carbon and glass fibers were reinforced in TPU matrix and manufactured by compression molding. The resulting composite materials were then tested for tensile analysis. After comparing the mechanical properties of the fibers, it was observed that the carbon/TPU showed the highest load-bearing capacity, followed by steel and glass reinforced TPU composites. The results also opened up the possibilities for carbon fibers to be a suitable replacement candidate to the steel cords that are used in applications such as conveyor belts for providing the required tensile strength.
A seamless modeling framework from injection molding simulation to anisotropic structural analysis is presented. Key features of the framework are anisotropic material modeling and fiber orientation data mapping, aspects that are facilitated by coupling Moldex3D, Digimat, and ANSYS software. The approach is exercised by modeling the mechanical response of injection molded tensile specimens with single and dual gates made of a thermoplastic resin with 20% glass fiber weight fraction. It is reassured that local fiber orientation is crucial for an accurate prediction of the mechanical strength of dual-gated tensile specimens with a weld line. Unlike the isotropic modeling approach, typical features of stress and strain concentrations along the weld line are clearly demonstrated. The capability of the approach is further highlighted by accurately predicting the break-off torque of a screw head used to adjust the seal compression in cable entry ports of optical closures.
In the current research, hybrid laminates having veneer facesheets and natural fibre composite cores were fabricated to investigate their fire and mechanical properties and to observe a suitable combination. Wool and flax fibres were selected for fibre reinforcement. Ammonium polyphosphate (APP) was used as the primary flame retardant for all the composites. The mechanical performance of the flax fibre reinforced fire retardant polypropylene (flax-FRPP) and fire retardant wool-polypropylene (FR-wool-PP) hybrid layered panels were further studied and compared to plywood made similarly. The results showed that hybrid laminates have better fire properties and the hybrid layered veneer composites can have significant structural applications if proper bonding between the composite and the veneer layers can be achieved. The tensile properties showed a reduction in Young’s modulus and ultimate tensile strength, though the wool-veneer hybrid laminates outperformed the flax-veneer ones. Moreover, the impact test showed that the wool-veneer hybrid laminates had the best resistance when compared to all the veneer-based samples tested. The results point towards the possibility of manufacturing a superior fire-resistant hybrid veneer composite laminate.
The incorporation of technical lignin, a multifunctional natural polymer, into rigid polyurethane foam (RPUF) for the enhancement of thermal insulation performance has gained increasing interest in academia and industry. However, the structural complexity of technical lignin hinders its dispersion in the polyols commonly used for the preparation of RPUF. Poor dispersion of technical lignin in polyols inhibits the chemical reactions and limits the potential improvement in the thermal and mechanical properties of RPUF. Herein we report enhanced dispersion of unmodified kraft lignin, at a loading of 3 wt % in a mixture of glycerol and an aromatic polyester polyol (20:80) for the preparation of RPUF. It has improved the insulation property by 30% while retaining its mechanical performance compared to the control RPUF without lignin. Such a level of improvement, to the best of our knowledge, has not been reported in RPUF using chemically unmodified lignin to date. This is attributed to the enhanced dispersion of the kraft lignin in the polyol blend causing changes in the cell morphology of the resultant RPUF, as supported by microscopic and rheological analysis. To this end, the insights into the influence of kraft lignin on the polyol-precursor on the properties of the RPUF are discussed.
The preparation and characterization of a multilayer film reservoir with clay/essential oil (EO) composites was described. The goal is to analyze the potential use of these reservoirs with clay/EOs composites as aroma-controlled release for various applications such as pesticide or attractant for pest control as well as antimicrobial control. Two types of clays were analyzed, porous halloysite (HNT) and octadecyl modified montmorillonite (MMT) nanoclay; as well as two types of essential oils, orange (OO) and thyme oil (TO). The DRX results confirmed that MMT clay presented higher thyme oil adsorption and better interactions than orange oil. Clay/EO composites encapsulated in multilayer film showed a prolongated aroma release during longer times. Polyamide (PA) barrier layer thickness has an effect on the liberation of the volatile compounds through the multilayer film.
ASTM D-2863 is a small-scale fire performance classification test, part of ASTM C-578 standard for polystyrene rigid thermal insulations, with a binary pass/fail outcome at a given oxygen concentration level. When applied to foams, the test is highly variable and is easy to manipulate, putting its accuracy as a test method into question. In this work, macro-imaging was used to closely monitor the foam – flame interaction to gain a better understanding of variability levers. For example, one of the levers is duration of flame application to a sample. Our imaging studies indicate that the pass / fail boundary oxygen level is strongly correlated with the flame application duration.
In this paper, a decorative material was first applied onto the light weight reinforced thermoplastic (LWRT) composite core mat during the core manufacturing, and then followed by a consolidation process through the calender rolls. This method is defined as an in-line lamination process with a finished A-surface panel in comparison with conventional off-line decorative materials lamination process, in which the decorative layer is applied in a separate process from core manufacture. Decorative layers with two patterns, namely woodgrain and marble, have been studied. The adhesion performance between the decorative skin material and LWRT composite substrate has been evaluated by 180° peel adhesion test following ASTM standard D903. The separation between the decorative layer and the substrate was difficult to initiate, which demonstrates an outstanding adhesion between the two components. A stylus method quantitatively confirmed the decorative surface is smooth and able to cover the core’s texture. Flatwise tensile test results by ASTM standard C297 method showed the decorative panels could not be delaminated, indicating strong bonding between decorative skin material and core mat. Materials produced with the woodgrain pattern were tested to have better flexural strength and stiffness than the sample made with marble decorative pattern material. In addition, flame retardancy results showed the laminated decorative panels can meet ASTM E84 requirement of Class C and above. The decorative material with custom design provides the decorative A-surface with an appearance of wood, stone, textile or other natural materials as desired, opening a window for the LWRT composite to be used inside an RV such as the interior layer of sidewall and ceiling.
Automotive manufacturers have been increasing use of natural fiber composites to reduce vehicle weight and respond to consumer demand for environmentally friendly products. However, the low thermal stability of natural fibers can limit their use to low-processing-temperature polymers and low-temperature automotive environments. Pyrolysis of biomass results in the formation of a porous substance called biocarbon, which can improve composite thermal performance, eliminate odor, and reduce hydrophilicity. The objective of this study was to investigate the effects of biocarbon on the performance of biocarbon-glass fiber hybrid composites for use in under-the-hood automotive applications. This study evaluated the macroscopic (mechanical performance, density) and microscopic (SEM) characteristics of biocarbon-hybrid composites with varying loading level and biocarbon type. Biocarbon-hybrid composites were approximately 10-13% lighter than currently used fan-and-shroud materials and the addition of biocarbon content improved composite flexural strength & modulus.
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