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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Processing Highly Filled Pre-Compounded Pellets on Single Screw Extruders
One of the more popular filled polymer materials has been wood flour with polyolefins and this will be used as the example throughout this paper. Processing other highly filled polymer and filler choices will often follow the same logic as that with wood fillers, so the discussion is somewhat generic in that respect. In the realm of profile extrusion utilizing wood filled plastic materials, there are a few machinery approaches that have proven successful. Although these machinery setups will be discussed and briefly compared, the single screw machine being fed pre-pelletized material will be the main thrust of the paper. The best choice for a given installation typically comes down to economics and product physical properties. Both the capital costs and the operational costs are important when selecting the extrusion means. Some of the major processing and equipment comparisons will be discussed. Since no one machinery approach has monopolized this application to date, perhaps different extrusion houses will still decide on different means to get successful profiles from high wood (or other filler) percentages.
Stress Concentration Evaluation in an Injected Commercial Piece using Computational Tools
The stress concentration evaluation in an injected commercial piece (CD case) was studied for typical amorphous polymers (polystyrene (PS) and high impact polystyrene (HIPS). It was obtained the general stress field in critical areas by using commercial simulation and modelation programs. Three constants for each material were determined considering: nominal stress in service and nominal stress considering process conditions plus service both calculated using a simulation program (K1service and K1process) and nominal stress in service using a solid 3D modelator program (K2service). The estimated stress concentration factor in service obtained from the programs showed differences less than 6%. The estimated stress concentration factor in process plus service is 62% bigger than the estimated stress concentration factor only in service.
Durability of E-Glass Fiber Reinforced Vinyl Ester Polymer Composites with Nanoclay in an Alkaline Environment
Two kinds of GFRP (glass fiber reinforced polymer) composite samples were used: the first with 2 layers of E-glass fiber fabric in a matrix of vinyl ester resin; and the second with addition of 1wt% and 2wt% nanoclay to the polymer matrix. The samples underwent aging tests with a sustained load of 890N (12.5% of tensile strength) for 3 months and the reduction in tensile strength was determined.A study was conducted to monitor the weight change of the GFRP specimens immersed in the alkaline solution under no sustained load. Another study was conducted to monitor the weight loss of glass fiber fabric immersed in the alkaline solution, also under no sustained load. Similar tests were conducted with neat resin samples and resin samples with 1wt% and 2wt% nanoclay.The results of the sustained load tests show a 12- 17% reduction in the tensile strength of the composite samples. However, no particular distinction was observed between the two types of GFRPs. It has been found from the absorption tests conducted on GFRP samples that the rate of alkaline solution absorption is higher in the GFRP samples without nanoclay followed by samples containing 1% and 2% nanoclay in that order. It has also been found that the dissolution rate of the glass fiber piece is linear. Tests conducted on the resin samples have shown that the weight gain was the highest in samples with 2% nanoclay followed by samples with 1% nanoclay and then by plain polymer samples.
Viscoelastic Behavior of Highly Filled HDPE/Wood Flour Composites
Dynamic and steady shear viscoelastic properties of highly filled (50-70%) HDPE/Wood flour composites have been investigated by parallel-plate and capillary rheometers. The concentration effect of a new lubricant and coupling agent on the melt rheological properties of the composites was explored as well. The results showed that addition of both lubricant and coupling agent to the 70% filled HDPE composite considerably improved its flow behavior. An increase in the complex viscosity and storage modulus of the wood filled systems at low concentration of both modifiers was observed in case of 50% filler loading. Higher concentrations of modifiers resulted in a decrease of the complex viscosity. In capillary flow, it was observed that the lubricant improved the processability to a great extent. It was also found that all wood filled composites did not obey the Cox-Merz rule. It was concluded that dynamic and steady shear viscosity measurements by parallel plate rheometer did not correspond to capillary measurements at elevated wood flour loadings.
Flexible Thermoplastic Elastomer (TPE) Based on Ionomer Technology
Ionomer products have been in the marketplace for more than 30 years. These products offer outstanding toughness, high melt strength, excellent abrasion resistance with hardness values greater than 40 Shore D. This new class of patented flexible ionomer alloy thermoplastic elastomers (TPEs) have been developed with lower hardness and lower modulus for both Consumer and Automotive applications. These products have hardness values in the range of 70 to 90 Shore A with high toughness and tear strength, high mar/abrasion resistance, good chemical resistance, superior stain resistance, and controlled gloss.This paper will address the polymer science and technology for these new ionomer-based TPEs with respect to morphology, physical properties, rheological properties and aesthetics, as compared to traditional TPEs, including thermoplastic vulcanizates (TPV).
Nanostructured Polymer Blends Prepared via in Situ Polymerization and Compatibilization: Processing, Morphology and Crystallization Behavior
A simple and versatile method of in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride polypropylene (mPP) matrix to yield a nanostructured polymer blend consisting of polycarbonate (PC) minor phase, a polypropylene major phase, and a surface-active compatibilizer (i.e. PC grafted onto mPP polypropylene backbone) has been reported. The current method showed that PC can be dispersed in a nanostructure of an average diameter of 150 nm. The crystallization behavior of the mPP in the blend was strongly accelerated unexpectedly by the in situ polymerization/compatibilization reaction.
Failure Analysis and Failure Prevention of a Floating Device
Saving keys that dropped in water is possible with a device to which keys are attached. It has a built-in float, which is activated when the product drops in water. The float launches itself up on a line of about 12m and appears back on the surface. The float is snap-fitted in the inner housing of the product and has a little sponge between the case and the float. When the device drops in water, the force exerted by the wetted sponge should be sufficient to disconnect the snap-fit assembly. The device is shown in Figure 1.Major mistakes have been made in design and material selection: a very stiff snap-fit construction and Nylon 6 as material for the float.Problems with the device arose, shortly after the developer had sold his company after a successful introduction during a water sport exhibition. The first summer after the transfer of the company was very humid and hot. When tests were carried out during the summer the majority of the floats could not be pushed out the inner housing.This was the reason for a civil court case, which lasted two years. The situation with the device was so complicated for the judge that he asked me as an expert witness to assemble a few products. I had to do this with both parties and I was completely free to determine the testing of the products in order to determine if the device was reliable enough.The paper describes all the analysis work for determining the reliability. It also describes how failure could be prevented by selecting a material that absorbs less moisture than Nylon 6 and by decreasing the stiffness of the snap-fit construction.
Penetration and Residual Scratch Depth in Reduced Coordinates: Comparability of Results
The scratch resistance was studied for several types of polymers: polystyrene (PS), styreneacrylonitrile (SAN), polyamide 6 (PA6), polyethersulphone (PES), polypropylene (PP), polysulphone (PSU), Santoprene® and Teflon®. Sliding wear was determined by performing multiple scratch tests were performed at different normal forces. Two new variables are introduced; reduced penetration depth and reduced residual depth in order to relate scratch test variables to Young’s modulus. Except for the elastomer Santoprene, all other polymers show similar values (the same order of magnitude) of the reduced penetration depth. Our reduced coordinates allow to recognize three types of polymers: brittle, viscoelastic and semiductile and highly elastic materials.
Surface Modification Techniques for Optimizing Adhesion to Automotive Plastics
Automotive plastics with a low polarity, such as PE, PP, TPO, POM, PUR and PTFE typically require surface treatment when decoration is required. Metallic surfaces may also require cleaning to remove low molecular weight organic materials prior to decoration. Once the above-mentioned interior and exterior grades of substrate surfaces are cleaned and activated, printing, gluing and painting are possible without the use of adhesion-promoting primers. This paper describes the latest innovations in three-dimensional surface treating technology for plastics finishing which address the need to advance adhesion properties, increase product quality, and achieve environmental objectives within the automotive industry. These innovations include advanced thermal and non-thermal discharge treatment processes for raising the polarity of surfaces to be painted, bonded, decorated, laminated, printed or to have tape applied.
Rheology of Carbon Nanofiber-Modified Thermotropic Liquid Crystalline Polymers
A series of carbon nanofiber-modified thermotropic liquid crystalline polymers (TLCP, Vectran V400P) were investigated for their rheological properties. Steady shear viscosity at 250 °C revealed that incorporation of nanofibers led to a higher steady shear viscosity and a narrowed plateau region, implying a different microstructure for TLCP composites from that of a pure TLCP. Complex viscosity increased with increasing CNF content (0 ~ 15 wt%) for all frequencies at 230 °C. Shear thinning behavior in complex viscosity plot was observed for pure TLCP and all composites; there was no plateau in the dynamic viscosity even for a pure TLCP, indicating that this TLCP does not obey Cox-Merz rule. In a G? versus G ? plot, the slope for pure TLCP was different from those of composites.
CAE Prediction of Ink Wash-Out on Phone Keypad for In-Mold Decoration
This article investigates the ink that using for in-mold decoration project washes out during production. The material for film and resin is polycarbonate. The average thickness of keypad of mobile phone is 0.7 mm. The printed ink on the film washes out due to the shear stress of plastic flowing. Therefore, the shear stresses of gates in balanced and unbalanced runner system are investigated by the results of CAE simulation. Furthermore, a mold of keypad was used to investigate the phenomena of ink wash-out and to compare with the results of CAE analysis.
Influence of the Coupling Agent on Polypropylene/Clay Nanocomposite based Wood-Plastic Composites
In this study, wood-plastic composites (WPCs) were made by compounding 50 wt% wood flour with 50 wt% of a matrix material composed of a polypropylene (PP)/clay-based nanocomposite using a co-rotating twin-screw extruder. Polymer nanocomposite (PNC) pellets, having varying percentages of clay, were first made by employing a PP/clay master batch. These pellets were then compounded with the wood flour and different percentages of polypropylene grafted with maleic anhydride (PP-g-MA) that acts as coupling agent between wood and PP. WPC pellets were finally injection molded into a variety of test specimens whose mechanical properties and rate of water absorption were measured and whose fracture surfaces were examined with the help of a scanning electron microscope (SEM). Results were compared with WPCs containing additional wood flour but no clay. It was found that the addition of clay to PP enhanced the modulus of both the base polymer and the injection-molded WPCs. Results of water absorption tests indicated a reduction in the initial rate of water uptake when 4 wt% of clay was used in the WPC matrix.
Organosilane Modification of Montmorillonite Clay: Characterization and its Influence on the Properties of Polyvinyl Alcohol Nanocomposite
Montmorillonite clay has been treated with various concentrations of 3-aminopropyltriethoxysilane in various solvents such as water, tetrahydrofuran and toluene. Intercalation of aminosilanes between the clay layers have been confirmed from the increase in the average dspacing obtained from X-ray diffraction (XRD). The two peaks observed in the x-ray diffraction results of clay modified with organosilanes in the water medium confirms the intercalation of amino silane as well as the tactoid formation due to the surface interaction of the surface –OH groups with water. Presence of organosilanes in modified clays has been further confirmed from the –CH asymmetric and symmetric stretching of >CH2 groups at 2920 and at 2855 cm-1. The amount of exchanged cations between organosilanes and clay has been determined using thermogravimetric analysis (TGA).The influence of modified nanoclay on the mechanical properties of the polyvinyl alcohol nanocomposite have been investigated. Significant improvement in mechanical properties like modulus and tensile strength has been observed.
Evaluation of Momentary-Mold-Surface-Heating (MmSH) Process
In order to prevent molding defects such as weld-line, flow-mark, gas-mark, etc., various mold-surface-heating injection-molding technologies have been developed. The feasibility of these technologies depends upon the heating method. Electric heating is easy to implement and control. However, it increases cycle time due to deep thermal penetration under the mold surfaces. The patented MMSH process utilizes a flame heating with propane gas and heats the mold surfaces only. Since only the mold surfaces are heated, the mold can be cooled down quickly. It also improves the surface quality and the mold filling into a thin wall. In this experimental study, process variables such as cavity pressure, resin temperature and mold temperature are evaluated during the molding process. The process variables measured with and without flame heating are compared. The enhancement of surface quality by the MMSH process is also evaluated.
Hygrothermal Aging of Glass and Carbon Fiber Reinforced Nylon 6 Sandwich Injection Moldings
Previous studies on hygrothermal aging would typically involve films, plates or dumbbell shaped specimens produced by various polymer-processing techniques. This study utilizes a relatively new processing technique; the sandwich injection molding, which enables the production of moldings with distinctive skin and core layers that can comprise of either similar or dissimilar materials. Diffusion of liquids into conventional injection moldings would usually be Fickian. However, in sandwich injection moldings, the unique combination of different materials at different specimen depths, coupled with a very different morphology caused by the ‘double-resin-flow’ during the molding process, would provide a rather complex but interesting platform to examine the extent of permeability, diffusion kinetics, as well as susceptibility of these moldings to hygrothermal degradation. This study compares the moisture absorption kinetics of sandwich and conventional injection molded glass fiber (GF) and carbon fiber (CF)-reinforced nylon 6 (PA6) composites. The effects of hygrothermal aging on their mechanical properties were also elucidated. It was found that in the sandwich moldings, better strength retention upon redrying of the specimens after aging, could be expected if the skin layer consists of CF-reinforced PA6. Thus, it is believed that the skin layer (and not only the core) in sandwich moldings can also determine the final bulk mechanical properties.
Parallel True 3D CAE with Hybrid Meshing Flexibity for Injection Molding
True 3D mold filling simulation is becoming popular for its capability to providing better accuracy with minimum model simplification. However, such a large-scale non-linear computation places extreme demands on computing power. Moreover, the complex 3D geometry of the injection molded part further challenges the capabilities of the existing mesh generator and computation algorithms. In view of this fact, this paper develops an innovative parallel true 3D mold filling simulation technology, which allows for the adoption of hybrid volume element topologies. The parallel processing capabilities and the hybrid-element-supported solver capabilities of the proposed methodology have allowed the user to perform analyses in much less time on complex model with much larger element number than ever.
Study on Response Characteristics in High Speed Injection Hydraulic System
In this paper, systematic studies on the response characteristic of hydraulic servo system for the high-speed injection molding were presented. A PID controller with digital V/P control cards was utilized to understand the response characteristics of system. The human-computer interface through LabVIEW software was also developed to get command and feedback signals then calculate delay time and reaction time. Influence of delay time and reaction time of elements to response characteristics of system in a non-melt loading condition with accumulator turned on were investigated in different process setting particularly up to a high injection speed of about 1000 mm/sec. The measured results were also compared with melt loading condition. From the results, it was found that the response time, which increases with increasing load and injection command, whereas it will decrease with increasing hydraulic pressure under the conditions of speed closed-loop control, stable and stepping up the PID velocity control. Obviously, different PID controller and the power of system play dominant roles to influence the response of system. From the results, one can provide hydraulic serve system design guideline for designers to develop a high speed injection molding machine.
Seamless Integration of Injection Molding and Structure Analysis Tools
The application of CAE analysis in injection-molded plastic part is becoming popular in the recent years, especially for part structure design and molding process optimization. Users study the designs and experiments through numerous individual CAE tools. In fact, these analyses and designs should be mutually dependent. The process-resulting properties might be not favorable to the final products, such as fiber-induced anisotropic mechanical property. Besides, the mesh requirement for different CAE analysis might be different. In this paper, an integrated approach from design phase to manufacturing phase is proposed to seamlessly combine part structure analysis and injection molding analysis through related-data linking and mesh property mapping. This developed approach is proved from numerical experiments to be a cost-effective method for related part/mold designers.
Three-Dimensional Simulation of Multi-Shot Sequential Molding
For the recent years, multi-shot sequential molding is widely applied in various industries. It is a process that uses two or more molds to produce a multi-material component. In principle, the first material is injected into the first mold by standard single-material molding technique and then moved to the next mold where the next material can be injected to combine with it. This complex process is difficult to identify and study correctly by the traditional 2.5D model. In this paper, a three-dimensional numerical approach is developed to simulate the filling, packing and cooling stages in multi-shot sequential molding, as well as the part warpage after ejection. Several cases are reported to indicate the success of the present model.
Experimental Study of the Cavity Pressure during the Vibration-Assisted MIM
A novel vibration-assisted metal powder injection molding (MIM) machine was adopted to study the effects of the vibration amplitude and vibration frequency on the cavity pressure. The melt in the cavity could be manipulated dynamically and continuously during the vibration-assisted metal powder injection molding. The experimental results showed that the cavity pressure was decreased with the increase of amplitude/frequency when the average injection velocity was constant. The cavity pressure gradient was lower than that of conventional injection molding processing (without vibration) within our research scope. The metal powder could be molded at a relative lower temperature or a lower injection pressure without the loss of the product quality.
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