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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Studying Polymer Particle Sintering with an Automated Imaging System
The formation of hollow plastic parts during rotational molding requires sintering, which involves the melting, coalescence and densification of polymer thermoplastic powder. Monitoring, visualizing and measuring the densification, which includes bubble formation and bubble dissolution, yields valuable information and is a useful technique to assess the rotomold-ability of different resins. An image visualization technique had been developed referred to as the automated Polymer Analyses Vision System (PAVS) to perform the quantification of a granular assembly rather than just a few particles.
Extrusion Foaming of LLDPE/Wood Fiber Composites
Foamed wood fiber/plastic composites (WPCs) with a fine-cell structure offer many benefits compared with the un-foamed WPCs, such as the reduced material cost, the decreased density, the improved mechanical properties, the enhanced processability, and their increased nailing-ability and screwing-ability. It is known that the gaseous emissions released from the wood fiber (WF) during processing should be suppressed to ensure a fine-cell structure. Linear low density polyethylene (LLDPE) is less shear sensitive due to its narrower molecular weight distribution and shorter chain branching, compared with conventional polyethylene. This paper investigates the feasibility of LLDPE as a matrix for making WPC foams with a fine-cell structure. The foaming behaviors of LLDPE/WF composites with both a chemical blowing agent (CBA) and a physical blowing agent (PBA) were investigated, to provide some guidance to WPC manufacturers.
Optimization of the FDM™ Additive Manufacturing Process
One of the most common Additive Manufacturing (AM) technologies is Fused Filament Fabrication (FFF), more commonly known by the trademarked name “Fused Deposition Modeling™” (FDM™). As FFF continues to gain popularity as a method of manufacturing, an understanding of all factors involved in the FFF process becomes essential. This study is an attempt to understand four primary printing parameters and the effects they have on part quality, solidity, and strength. These printing parameters are extrusion rate, nozzle travel speed, layer height, and path width.
A recommendation for the determination of optimal extrusion temperature and feed rate was found. A theoretical relationship between the four print parameterswas developed. The resulting solidity was found to vary throughout a printed part, which has effects on the predictability of part strength. Micro computed tomography was proven valuable in this analysis as well as being an effective tool for investigating the bead structure.
Injection Molding and Mechanical Characterizion of Carbon Fiber-Woodfiber/Polyproplene Hybrid Composites
Hybrid composites are made by incorporating two or more different types of fillers in a single matrix, which is highly tailorable. Carbon fiber (CF) reinforced composites have been well developed for certain industries such as aerospace and sporting goods. However, the high cost of carbon fiber, as well as lack of cost effective processing technologies for mass production, prevents its penetration to many different markets. Wood fiber (WF), an environmentally sustainable bio-fiber, has been used widely in making wood/plastic composites (WPCs) for building products and automotive applications, due to its low cost and lightweight. Nevertheless, WPCs have very limited structural applications where strong mechanical properties are required. Incorporating CF and WF into a polymer matrix to make hybrid composites through injection molding, would be a path to expanded applications for both. This paper investigated the injection molding of CF-WF/polypropylene hybrid composites and their mechanical properties. The effects of fiber content and hybridization on the mechanical properties were studied.
Stochastic Modeling and Quantification of Uncertainties of the Injection Molding Process
Uncertainties of the injection molding process are stochastically modeled. A system is considered showing the interaction of the clamping unit and the mold. Therefore, a deterministic equation is obtained modeling the system simplified as a set-up of springs in order to easily determine the resulting forces in the load path of the system. As an example for uncertain process parameters the mold temperature and the pressure force of the injected polymer are chosen. The Monte Carlo method is used to receive the stochastic results for the mean and the probability interval. Furthermore, an optimization algorithm is applied to improve the system in terms of the stiffness of the clamping unit and the temperature variation of the mold. This procedure is well suited to predict possible failures which appear only very seldom and therefore would not be revealed by commonly used set-up procedures.
Effect of Void Fraction on Dielectric Properties of Injection-Molded Polypropylene/MWCNT Foams
Polypropylene-multiwalled carbon nanotube (PP-MWCNT) nanocomposite foams with various void fractions ranging from 0 to 40% were prepared using injection molding. Their microstructure, cellular morphology and dielectric properties were studied. The results indicated that overall the real permittivity increases with void fraction. However, the void fraction effect was more pronounced at higher MWCNT contents. It was found that by a proper combination of void fraction and MWCNT content, real permittivity can be increased while the dielectric loss is decreased. For instance, 20% void fraction in PP-1.95vol.%MWCNT nanocomposites resulted in ~7 times increase in permittivity (reaching to 73.1) and ~3 times decrease in dielectric loss (reaching to 0.03). Such enhancements were explained in terms of the interfacial polarization and the rearrangement of MWCNTs caused by cell growth during foaming.
Study on Orientation and Distribution of Metal Fiber in Epoxy Substrate by Using Electromagnetic Control
Controlling fiber orientation and distribution in flow field is one of the important issues in composite materials. In this study, induction electromagnetic is used to control fiber orientation and distribution in flow field so as to investigate effect of distribution of fiber orientation angle and penetrating conductivity. The result of this study demonstrates that the ratio of static electromagnet controlling, dynamic electromagnet controlling and nonelectromagnet controlling is 12.2:9.6:1. Besides, the smaller viscosity of base can cause the fiber to be more easily arranged according to the magnetic field. Key Words: stainless steel fiber, fiber orientation, electromagnet.
Impact of Foaming on Fiber Breakage, Conductivity, and EMI Shielding of Injection-Molded Polypropylene/Stainless Steel Fiber Composites
Lightweight polypropylene/stainless-steel fiber (PP-SSF) composites with 15-35% density reduction were fabricated using foam injection molding and supercritical carbon dioxide (CO2). The electrical percolation threshold, electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of the PP-SSF composite foams were characterized and compared against the solid samples. The effects of physical foaming on fiber breakage were investigated. The results showed that the presence of dissolved CO2 decreased the fiber breakage by about 30%, which contributed significantly to the enhancement of electrical and EMI shielding properties. Consequently, the percolation threshold decreased up to four folds from 0.85 to 0.21 vol.% as the void fraction increased from 0 to 35%. The specific EMI SE was also significantly enhanced. A maximum specific EMI SE of 75 dB.g-1cm3 was achieved in PP-1.1vol.% SSF composite foams, which was highly superior to 38 dB.g-1cm3 of the solid PP-1.0vol.% SSF composites. The results reveal that light and efficient products with a lower fiber content can be developed by foaming technologies for EMI shielding applications.
Open Cell Microcellular Foams of Poly(Lactic Acid) Blend with Poly(Butylenes Succinate)
Biodegradable poly(lactic acid) (PLA)-based PLA/Poly(butylenes succinate) (PBS) foams with open cell structure were prepared via batch foaming method using supercritical carbon dioxide as blowing agent. It was found that PLA was immiscible with PBS, and PBS phase was dispersed as tiny spheres or large domains at various concentrations. The addition of PBS reduced the viscosity of the blends. During foaming process, the PLA/PBS interfaces acted as cell nucleation sites and the low melt strength PBS contributed to the formation of cell connection channels, which resulted in open cell structure. The investigation of PBS content found that PLA/PBS (80/20) foamed at 100 °C obtained the highest cell opening rate (96.2%).
Effects of Thermoplastic Elastomers on Mechanical Properties of Glass Fiber Reinforced Poly(3-Hydroxybutyrate-Co-3- Hydroxyhexanoate)
This study investigates the effects of thermoplastic elastomers on the mechanical properties of glass fiber reinforced bacterial polyester, poly(3-hydroxybutyrate-co- 3-hydroxyhexanoate) (PHBH), composites. The thermoplastic elastomers used were styrene-ethylenebutylene- styrene copolymer (SEBS) and maleated styrene-ethylene-butylene-styrene copolymer (SEBSMA). Composites were prepared by melt-compounding and injection molding. Mechanical test results suggested that SEBS-MA was more effective than SEBS in improving ductility, fracture energy, and notched Izod impact strength of glass fiber reinforced PHBH composites. Scanning electron microscopy results suggested that SEBS-MA encapsulated fibers as well as dispersed in the PHBH matrix, whereas SEBS dispersed in the PHBH matrix without fiber encapsulation.
Structure and Properties of PVDF/GO Nanocomposites Prepared by Water-Assisted Mixing Extrusion
Poly(vinylidene fluoride)/graphene oxide (PVDF/GO) nanocomposites are prepared by water-assisted mixing extrusion via injecting GO suspension into the PVDF melt continuously. The introduction of the GO layers increases the crystallinities of the ?-phase due to the special interaction between the carbonyl groups in the GO and the >CF2 groups in the PVDF. Furthermore, the GO layers are found to reinforce the PVDF matrix, as evidenced by the increased Young’s modulus and tensile strength. The TEM and SEM micrographs demonstrate that the GO layers are well dispersed and distributed in the PVDF matrix because the water molecules help the PVDF chains intercalate and exfoliate the GO layers and improve the interaction between the PVDF chains and GO layers during water-assisted melt mixing.
Degradation of Glass Fiber Reinforced Polyamide Composites during Long Fiber Reinforced Thermoplastics Direct Extrusion Compression Moulding Process
This study investigates the level of degradation for glass fiber reinforced polyamide composites during long fiber thermoplastic direct extrusion compression moulding (LET-D-ECM) process. Thermogravitmetric analyses (TGA) were performed on samples taken at different locations within the process. The Ozawa/Flynn/Wall method was used to estimate the apparent activation energy of the samples to study how degradation of PA6 progresses during the LET-D-ECM process. The results suggested that the apparent activation energy decreased in the extrusion processes. However, the apparent activation energy at early conversion increased when the sample was exposed to oxygen either during processing or sample collection.
Development and Application Studies on a Novel Kind of Low Alkaline Hindered Amine Light Stabilizer encapsulated in Porous Polypropylene
In this paper, Sunovin® 5513PP- a novel kind of solid low alkaline hinderd amine light stabilizer (HALS), encapsulated in porous polypropylene, - was developed by mixing liquid light stabilizer (bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Sunovin® 5513) in extrusion foamed polypropylene. In such way, the application area of low alkaline liquid light stabilizers was broadened from liquid to solid polymer. TGA tests were then performed to investigate the thermal stability of Sunovin® 5513PP. Xenon arc lamp aging tests and QUV accelerated weathering tests were conducted to explore the aging-resistance effect of Sunovin®5513PP in PP compounds and acidic PP compounds. The results show that the thermal stability of Sunovin® 5513PP is better than that of pure Sunovin® 5513 and Sunovin® 5513PP presents better anti-light aging effect compared with those alkaline light stabilizer in acidic PP compounds.
New Phosphorus Based Flame Retardants for Thin-Walled Applications
Building on more than 30 years expertise in phosphorus chemistry and flame retardants (FRs) for textiles, Thor (www.thor.com) has recently developed an extensive range of non-halogenated FRs dedicated to plastics applications. Cornerstones of the portfolio are two new substances, AFLAMMIT® PCO 700 and PCO 800 that have been registered under REACH and TSCA, and another proprietary high-performance FR, AFLAMMIT® PCO 900.
While they can be used in various polymers, thicknesses and applications, these new substances are expected to find commercial use primarily in polyolefin based thin-films, tapes or foams, where they fill the gap between traditional formulations (based on organic bromine or chlorine based FRs and antimony trioxide) and the available halogen-free additives, which are essentially limited in performance.
The paper will introduce the new AFLAMMIT® products and their synergistic combinations in a benchmark approach and will demonstrate their unique FR effectiveness. These new additives not only represent the first halogen-free alternatives to the widely used halogenated compounds in the targeted applications, but have also demonstrated to be successful in particular applications without halogen-free requirements, where performance based criteria are most important (i.e. highly flame-retarded films preserving transparency or light-weight FR thermoplastic foams).
Determination of the Compositions of Fully Biodegradable Ternary Blends with Near-Infrared Spectroscopy
Comparison between near-infrared (NIR) spectroscopy in diffuse reflectance and transmission modes for determination of the compositions in fully biodegradable poly-(lactic acid)/poly-(propylene carbonate)/poly-(butylene adipate-co-terephthalate) (PLA/PPC/PBAT) blends was made. Principal component analysis (PCA) was firstly performed to qualitatively examine the response of two modes to concentration change. Then partial least square (PLS) models were developed for quantitative evaluation based on root mean square error of cross validation (RMSECV), root mean square error of prediction (RMSEP) and coefficient of determination (R2). The data showed that NIR spectroscopy in both modes succeeded in extracting information of concentration of complex fully biodegradable PLA/PPC/PBAT blends, whereas diffuse transmission mode presented better performance than diffuse reflectance mode.
Numerical Simulation for Insert Injection Molding of Oneconstituent Polypropylene Single-Polymer Composites
One-constituent polypropylene single-polymer composites (PP SPCs) possess matrix and reinforcement which are from the same kind of PP with identical chemical structure. One-constituent SPCs are characterized by lower density, lighter weight and better interfacial adhesion, which can fulfill the demands for fully recyclable engineering composites. Traditional SPCs preparation processes like hot compaction, film stacking, co-extruding have long cycle, narrow processing temperature window and difficult control of processing temperature. Insert injection molding can solve these issues with high effectiveness of preparing SPCs. In this article, we simulated and analyzed the insert injection molding process of one-constituent PP SPCs for testing the processing temperature window and mastering the temperature distribution inside the mold cavity. Numerical results of the insert injection molding process for oneconstituent PP SPCs were also compared with those of injection molding process for pure PP. Results of temperature, viscosity and warpage were all discussed which could be used to determine the optimum injection molding conditions.
Variation of Scratch Behaviors of Thermoplastic Polyolefins (TPO) Due to Thermal Degradation
Evaluating the effect of scratching speed and thermal degradation time acting on the scratch resistance of Thermoplastic Polyolefin (TPO) quantitatively using ASTM D7027-13 standard is the main theme of this paper. By measuring the critical normal load at a scratch mode transition point, scratch resistance of TPO is characterized. The test result showed that thermal degradation causes TPO to become susceptible to scratch. As scratch speed and thermal degradation time increase, critical points appeared faster which means the specimen failed at the lower load level.
Thermally Triggered Shape Memory Sensors via Nanolayered Coextrusion of Commercial Polymers Materials
A multilayered film polymer processing approach to produce one-way shape memory films and labels was demonstrated. Utilizing a relatively low cost, industrially scalable fabrication processes of multilayered film coextrusion and film embossing, 1”x1” areas of layered polymer films were loaded for thermally triggered film topography changes to produce passive sensing or anti-counterfeit labels. Customizability in the one-way thermally induced multilayered film shape memory was demonstrated via hidden text, changes in film optical transmission, and induction of custom laser diffraction patterns off the surface of encoded and recovered multilayered shape memory films.
The multilayered film coextrusion approach enabled actuation of the overall film topography changed, based on the highly regular sequential micro and nanolayering of two alternating polymer materials with differing glass transition and softening temperatures. Stemming from a synergy of the nanolayer thickness of highly ordered layered film structures and length scale of chemical bond thermal relaxations of the polymer materials, shape memory films and labels were created from commercial homopolymers that do not require block copolymer architectures or custom chemistry.
A Three-Layer Foamed Composite Prepared by Rotational Molding
A three-layer composite (polymer-fiber / polymerfoam / polymer-virgin) was made by rotational molding using a laboratory-scale biaxial rotational molding machine. The mold consists of a cylindrical stainless steel of five liters of volume. A linear medium density polyethylene (LMDPE) was used in all layers. In the composite layer a natural fiber (agave) was included and in the foam layer a chemical foaming agent (azodicarbonamide, ACA) was incorporated. The effect of the agave fiber and foaming agent contents was related to the tensile properties. The inner air mold temperature and rotomolding cycle time are reported.
Root Cause Analysis and Fixing of Coextruded Polyolefin Blown Film Defects
A blown film producer experienced a film production and quality defect which prevented it from making quality coextruded films. The problem was analyzed, the root cause was identified, and a solution was implemented. The root cause of the problem was the improper installation of the die assembly onto the rotator of the line which caused molten polymer pumped from the core extruder to leak from the entry of the core spiral mandrel into the entry of the outer skin spiral mandrel. The required fix was simply to adjust the position of the locating collar of the rotator so that the die assembly properly sealed onto the rotator. Following the implementation of the fix, the film producer was able to produce quality product with the desired structure.
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