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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Poly(L-lactide) (PL) has been used as a bioabsorbable material in the medical and pharmaceutical fields. The unmodified hydrophobic PL surface generally has low cell affinity; thus, modification of PL film surface properties is necessary to improve its use as a biomaterial. Our surface modification method involved the use of photografting and typical wet chemistry to create branched architectures containing amine functionalities on the periphery. The resulting film surface was analyzed using contact angle goniometry. F3T3M mouse fibroblast cells were cultured on unmodified PL film and PL film grafted with the branched structure. Optical micrographs showed enhanced cell proliferation on the surface-modified PL film.
An injection moldable thermoplastic Polyetherimide Sulfone resin with Tg of ? 250°C (482°F) was developed for advanced automotive lighting systems and other applications requiring thermal capabilities greater than those currently achieved with Polyetherimide. With a +30°C higher Tg than Polyetherimide, the resin can still be melt processed using standard injection molding machine equipment by increasing melt temperature to 385-415°C and mold temperatures of 150- 175°C. The injection molding processibility of the resin and its properties are presented and compared with Polyetherimide.
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.
Premise of Research: (a) Properties vs. gelation and vitrification. (Vitrification occurs when Tg = Tcure); (b) Isothermal properties at T vs. conversion as a consequence of rising transition temperatures (e.g., modulus and density at T vs. T? and Tg); (c) Effect of isothermal aging in the localization of subsequent properties vs. temperature. Results in Graphical Form: (a) TTT Diagram: Isothermal Time-Temperature- Transformation Cure Diagram; (b) CHT Diagram: Continuous Heating TTT Diagram; (c) Property- Temperature-Conversion Diagram.
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.
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.
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.
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).
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.
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.
This paper presents an extrusion-based open-cell foaming process with polypropylene (PP)/metallocene polyethylene (mPE) and PP/low-density polyethylene (LDPE) blends. The basic strategy for achieving a high open-cell content is to induce a hard/soft melt structure using two semi-crystalline polymers with distinctively different crystallization temperatures (Tc), and to foam this non-homogeneous melt structure with supercritical CO2. The effects of polymer blending, die geometry, and temperature on cell opening were investigated in this study.
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.
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.
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.
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.
With the Taguchi method, the process parameters of dynamic injection molding are optimized and the relationship between processing conditions and the physical properties of isotactic polypropylene is explored. The results show that vibration frequency and vibration amplitude have greater influences on mechanical properties of isotactic polypropylene than injection velocity and packing pressure in most of our experiments. The samples’ impact strength could be improved by about 40% with optimum parameters. The morphology and crystallinity are also explored with DSC and WAXD.
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.
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.
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.
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.
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