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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The Open Hole Compression Test for Evaluation of the Effects of Fiber Waviness in Fiber Reinforced Composites
In this study, we investigate the open-hole compression (OHC) test for evaluating the effects of fiber waviness in continuous fiber reinforced composites. The OHC specimens are fabricated from carbon fiber / epoxy into unidirectional laminate containing intentional waviness defects. The effect of the waviness morphology is also investigated by evaluating the effects of the resin pocket at the root of the waviness profile. Temporal evaluations of the load-deformation response, microscopy and acoustic emissions are used to understand the failure modes from the waviness specimens. The waviness specimens show different failure modes and can be structurally correlated to either kink zone formation and fiber fracture or interlaminar damage. The results also show the influence of the notch and the resin pocket on the interlaminar strain responsible for initiation of damage in the composite specimens.
Improvement of Melt Strength and Crystallization Rate of Polylactic Acid and its Blends with Medium-Chain-Length Polyhydroxyalkanoate through Reactive Modification
Poly(lactic acid) (PLA) was reactively modified by using a multifunctional co-agent (triallyl trimesate) in the presence of dicumyl peroxide. The viscosity, elasticity and melt strength of PLA increased substantially following reactive compounding. Furthermore, the rate of crystallization of co-agent in modified PLA was significantly higher than that of the pristine PLA and a distinct crystallization peak appeared. Reactively modified blends of PLA with an elastomeric polyhydroxyoctanoate exhibited similar features, and significant improvements in blend morphology.
Catastrophic Failure of Fiber-Reinforced Thermoplastic Lawnmower Wheels
Three instances of riding lawnmower, fiber-reinforced thermoplastic wheel failures resulting in serious injuries have been examined. The wheels fractured violently due to the presence of fatigue cracks. The failure mechanism is fatigue initiation and growth during normal service followed by brittle overload fracture upon handling (e.g., tire inflation). One of the wheel failures is described in detail herein. Several design and manufacturing issues may have contributed to the failure: (1) cracks initiate and grow by fatigue at weak points in the design; (2) glass fiber orientation is nonrandom and predominantly in a direction that is ineffective in preventing fatigue crack propagation; (3) voids in the plastic weaken the part by reducing the effective cross sectional area; and (4) the polypropylene resin was apparently contaminated with polyamide. Crack path analysis was a very valuable tool used to understand the fractures.
Thermal, Mechanical, Rheological and Dielectric Properties of Clay-Containing SEBS Nanocomposites: Effect of Morphology
In this paper, intercalated vs. exfoliated structures of clay-containing nanocomposites of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene are studied. The morphology of the nanocomposites, characterized earlier by microscopy and Small Angle X-Ray Scattering, is confirmed through the study of the thermal, mechanical, rheological and dielectric behavior. In particular, the improvement of the thermal stability of the polymer matrix was induced by the intercalated structure while the viscoelastic behavior and the mechanical and dielectric relaxation phenomena were more sensitive to the exfoliated structure.
Effect of Solvent Volatility on Diameter Selection of Nanofibers Produced by Gas Jet Fiber Process
Gas Jet Fiber (GJF) process involves aerodynamic forces to draw a jet of polymer solution from a nozzle and to convert it into polymer nanofibers. The jet of polymer solution undergoes rapid stretching and turns into solid nanofibers as the solvent evaporates. The nanofibers are collected as non-woven mat. An important parameter defining the nanofiber properties is fiber diameter. This work investigates selection of diameter of nanofibers from homogenous solutions of two immiscible polymers in two mutually miscible solvents. Several morphological forms such as interpenetrating network, bilobal, and core-shell are obtained by selecting two solvents with different vapor pressure and solubility parameters. This paper addresses the roles of polymer solution viscosity and solvent volatility in defining polymer fiber diameter varying between 1 µm and 100 nm.
Increased Strength and Thermal Conductivity in MWCNT/Epoxy Composites by Ultrasonication Aided Internal Mixing
To explode epoxy processing methods and overcome limitations of shear mixing and ultrasonication, internal mixer containing laminated kneading block structured rotors are designed and then the unites assemble configuration is optimized by evaluating mixing parameters of epoxy mixing field with the help of POLYFLOW software. Moreover, tip ultrasonication horn is integrated into the sealed barrel positioning at confluence areas between couple rotors to apply ultrasonication field simultaneously during mixing. Kinds of multi-wall carbon nanotubes are mixed with epoxy to prepare reinforced composite. Series characterizations are performed, including SEM, TGA/DSC, tensile test and thermal conductivity measurements to verify the equipment’s mixing capability. At 1.5wt% loading rate, significant mechanical improvements (above 27%) and thermal conductivity increase (above 22%) are observed, indicating excellent nanotubes dispersion and distribution in epoxy matrix.
Bio-Based Elastomers from Cationic/Free Radical Polymerization of Soybean Oil
Recently bio-based polymers procured from different natural resources have attracted greater attention as the viable eco-friendly alternatives to traditional petroleum-based products. Among various bio-based materials, vegetable oils represent one of the most abundant, low cost renewable material having the potential to be an ideal alternative to chemical feedstock/ traditional synthetic polymeric materials. Different derivatives of vegetable oils can be used as preliminary resources for the synthesis of a variety of materials (e.g. polyols, glycol, lubricants and plasticizers for polymers) owing to the high reactivity of their oxirane rings. So in this project, we have synthesized different soybean oil based elastomer using cationic/ free radical polymerization. Some preliminary study on the dynamic mechanical behavior of the synthesized elastomer has also been carried out.
Study of Mechanical Properties of Soy Flour Additives in Elastomer Composites
Bio-based polymers and biofiller polymers are becoming viable alternatives to petroleum-based plastics and offer increase bio-content at the end of service life compared to conventional plastics and rubbers. Advantages of soy flour include being lightweight, low cost, high strength and stiffness but interfacial adhesion poses to be an issue. In this project, soy flour as an additive to synthetic rubber matrix based composites were studied. Surface modification such as acetylation and grafting with PMMA were compared to untreated soy flour composites. In general, untreated as soy concentration increased, the mechanical properties of the composites decreased. In contrast, pretreated soy flour (acetylated soy flour and grafted soy flour) at 10wt% performed comparable to that of the neat rubber and resulted in an increase in tensile stress.
Effect of Feature Spacing when Injection Molding Parts with Microstructured Surfaces
The effects of microfeature spacing on the replication of thermoplastic elastomer features was investigated using micropillars with two diameters (10 and 20 ?m) and three spacing ratios (0.5:1, 1:1, and 2:1). The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Feature spacing significantly affected the replication of micropillars using a thermoplastic elastomer. This replication was competition between cooling and pressurization of the melt. Wider spacing between smaller features allowed cooling in the tooling lands to dominate the feature filling. Higher pressures did not always produce better feature replication, suggesting that cooling effects in the tooling “holes” restricted filling. High pressures also produced surface porosity in the molded pillars.
Comparison of Microstructured Surfaces Using Injection Molding and Nanoimprint Lithography
For the first time, thicker (2.4-mm) polycarbonate and polymethylmethacrylate sheets were employed in thermal nanoimprint lithography. The replication of microfeatures using this process was influenced primarily by imprinting temperature and not by imprinting pressure and time. Imprinting of thicker sheets generally showed the same replication trends as injection molding – i.e., channel depth increased with lower viscosity materials, definition of the channel bottom improved with increased solidification time, and land formation required complete replication of the channels. The higher temperatures in injection molding increase thermal and shear-induced stresses, thus increasing shrinkage and decreasing feature definition.
Quantitative Modeling of Scratch-induced Deformation in Ductile Amorphous Polymers
Scratch-induced surface deformation in polymeric materials is a complex mechanical process due to the rate, time, temperature and pressure dependent behavior of polymers. In this study, attempts were made to quantitatively predict the development of different scratch-induced deformation features of a model ductile amorphous polymer. By including the rate and pressure dependent mechanical and frictional behavior in the FEM model, good agreement has been obtained between FEM simulation and experimental findings. Usefulness of the present numerical modeling for designing scratch resistant polymers is discussed.
Degassing of Residual Monomer during Reactive Extrusion of PA6: Experimental Analysis
Polyamide 6 (PA6) with different molecular weight is polymerized in a twin-screw extruder based on the anionic polymerization. Due to a thermal equilibrium a temperature depending content of 10% (wt/wt) residual monomer remains in the PA6. Product quality requires a monomer content < 1% (wt/wt) A two-step vacuum degassing was adapted to realize an in-line monomer removal. The influence of the main degassing parameters on the amount of residual monomer and the relative viscosity of the PA6 is investigated. It was found, that a two-step degassing and injection of water as entrainer provides a content of residual monomer of 2.1% (wt/wt) based on high molecular weight PA6 and a polymer throughput of 10 kg/h. With decreasing content of residual monomer the melt viscosity increases causing a higher shear energy dissipation and melt temperature. At elevated melt temperatures side reactions and thermal degradation of the PA6 can occur, which were detected by changes in relative viscosity.
The Effect of Openair® Atmospheric Plasma on the Adhesion of UV Curable Coatings to Plastics
Ultraviolet (UV) cured liquid and powder coatings provide plastic part manufacturers with a number of desirable benefits including enhanced appearance, improved performance and various process advantages. At the same time, the rapid film formation and densely cross-linked chemistry that characterize UV curable materials also increases the likelihood of adhesion failures. That these coatings are formulated with little or no solvents makes attaining adhesion even more challenging. This paper examines adhesion problems inherent in UV curable liquid and powder coatings, and explores the tradeoffs associated with popular methods to mitigate adhesion problems. We find that atmospheric plasma treatment provides an especially effective means of improving adhesion of UV cure coatings to a wide range of plastic substrates.
Polylactic Acid-Based Polymer Blends for Durable Applications
Elevated temperature and humidity lead to rapid degradation of polylactic acid (PLA). Consequently, PLA is not used for durable applications since properties cannot be maintained. The effects of blending PLA with polycarbonate (PC), heat treatment, and graphene inclusion were investigated in the presence of high humidity at 50°C. Samples were studied for up to 1 year of equivalent outdoor aging. While crystallization and adding graphene enhance short-term stability, it was determined that PC-rich blends in which the PC encapsulated the dispersed PLA had significantly improved hydrolytic resistance and mechanical properties as compared to both PLA and PLA-rich blends.
Thermoplastic Starch: The Prepation Method
This work presents a systematic study about thermoplastic starches. Corn starch was mixed with 2 and 4 wt.% of carboxylic acid and 20 to 30 wt.% of water. The samples were prepared in an internal mixer coupled to a torque rheometer, and the torque values were monitored during mixing. The specimens for mechanical tests were calendered and cut with a knife. The mixtures were characterized by mechanical testing (tensile strength), scanning electron microscopy, and thermal analysis. The torque curves indicated that the samples with and without adipic acid addition suffer retrogradation. When the water content is increased, the glass transition temperature values decrease because water acts as a plasticizer for starch. The mechanical test results showed that samples with 2 wt.% acid content present the highest values of elastic modulus and tensile strength, and the lowest values of elongation at rupture.
Reproducible Relaxation Spectrum of Polyethylene via Global Log-Polynomial Kernel
Discrete relaxation spectrum of an HDPE sample has been calculated using two different approaches modified from the original BSW spectrum. The spectrum with the global kernel consisting of two log-polynomial components appears to provide a good representation of the experimental data. It results in a more reasonable prediction of properties on the experimentally unreachable frequency range than a truncated 6-point spectrum does. The global kernel approach also shows the potential of predicting inflection points on VGP plots, which are useful to quantify LCB and other molecular or morphological features.
Additive-Assisted One-Step Melt Mixing Approach to Disperse MWCNT into LLDPE
Nanocomposites based on linear low density polyethylene (LLDPE) with multiwalled carbon nanotube (MWCNT) were produced by an additive-assisted one-step melt mixing approach. For this the polymer granules, nanotube powder (Nanocyl NC7000) and 1 to 10 wt.% of non-ionic polyoxyethylene cetyl ethers with different ethylene glycol repeating units were simply fed together in the hopper of a small-scale DSM Xplore 15 twin-screw microcompounder. The MWCNT/LLDPE composites showed excellent MWCNT dispersion and highly improved electrical properties as compared to samples without the additives.
Experimental Investigation on Corrosion Properties of LDS MID for Hearing Aid Applications
The trend towards miniaturization is ever going in the hearing aid industry. The Moulded Interconnect Device (MID) technology can offer the unique possibility to reduce the size of the hearing aids by combining electrical and mechanical functions in the same components. On the other hand, one of the main concerns for MIDs in hearing aids is the corrosion of metal tracks. This paper investigates the corrosion of the MID parts based on different base materials, layer thickness and mechanical wear of the MIDs. The results presented in the paper will be useful for designing MIDs in hearing aids and other electro-mechanical applications.
Optimization of Polyolefin Manufacturing Assets in Changing Economies
Dynamic changes in global and regional polyolefin supply and demand combined with varying feedstock pricing have required strategic decision making by polyolefin manufactures. Polyolefin producers are under continued pressure to evaluate plant closing, product mix, target market and asset optimization. This paper identifies several techniques by which polyolefin manufacturing companies can better manage these changes using advanced on-line Nuclear Magnetic Resonance (NMR) technology. Shared examples from commercial plants will demonstrate how the NMR technology has enabled leading suppliers to improve process operability while reducing grade change costs, site inventory levels and costly off-grade blending.
Effect of Nanoplatelets and Polymer Crystallinity on Moisture Diffusion through Polylactic Acid
Polylactic acid (PLA), a bio-derived biodegradable polymer, is being considered as substitute for conventional non-biodegradable polymers in packaging applications, among other uses. However, it has low barrier properties for gases and water vapor. In this work, the effect of nanoplatelets of nanoclay and graphene has been evaluated on the water vapor permeability through PLA films. In addition, the effect of PLA crystallinity has also been studied. It was found that while both nanoclay and graphene have a significant effect on the water vapor permeability, PLA crystallinity has only a smaller effect.
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