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.
We have designed a series of mechanochromic devices inspired by nature with the capabilities of changing transparency and “switching on/off” luminescence in response to mechanical stimuli. The key to accomplish these excellent optical properties is to control strain-induced surface engineering, that is, the longitudinal cracks opening and transverse invaginated folds. All of these devices are comprised of a rigid thin layer atop polydimethylsiloxane (PDMS) based elastomer, which can be facilely and quickly fabricated. For transparency change mechanochromism, the folds and cracks with excellent light trapping and scattering capabilities can endow high opaqueness to the originally highly transparent samples. The evolution of crack opening and fold–ridge mechanisms are captured through finite analysis that incorporates damage and cracks in the rigid thin layer. For luminescent mechanochromism, the strain-tunable cracks on the UV shield layer act as “gates” to mediate the traveling of UV light to “switch on/off” the luminescence of mechanochromism. This device exhibits a remarkably high strain responsive sensitivity, demonstrating an excellent sensing capability for detecting mechanical failure or damage. All the mechanochromisms also show outstanding durability and reversibility.
This work combined the grafting maleic anhydride(MAH) onto polypropylene (PP) and the coupling reaction between diamine and MAH grafted PP (PP-g-MAH) into a single step through a twin screw extruder. Detailed molecular weight analysis, rheological characterization and foaming tests were conducted subsequently. The investigation indicated that the concentration of reagents plays a key role in control of the chain structure. By the combination of SEC and rheological analysis, the optimum amount of MAH and diamine for preparing LCB-PPs is decided. However, the optimum peroxide loading during branching modification is not clear and need further evidence. To solve this problem, a foaming test was carried out to assess the performance of the modified PP with different peroxide loading. The results demonstrate that an intermediate level of modification (peroxide concentration, 0.2-0.4 wt%) is already sufficient for the optimization of foaming process.
The long-term performance is critically important for safety assessment of pressurized pipe materials. In the present work, cyclic cracked round bar (CRB) test was utilized to investigate the slow crack growth behavior in a compounded polyolefin pipe material exhibiting flame retardant and antistatic properties (FRTPO). The applicability of the CRB method to evaluate the long-term performance of compounded polyolefin material was also discussed and validated. We demonstrate, for the first time, that the PP-based FRTPO pipe compound displays, surprisingly, excellent long-term performance comparable to that of commercial PE100 pipe material.
Multilayer films are widely used in packaging industry to fulfil different applications. It is well known that multilayer structure is essential for high gas barrier packaging using EVOH, because moisture has negative effects on EVOH’s barrier properties [1, 2]. In order to effectively use EVOH in barrier applications, usually a moisture barrier layer and a tie layer are required [3, 4]. In this study, specially prepared polymeric compounds based on EVOH and polyolefin with good dispersion, proper compatibility/incompatibility and viscosity match are prepared. These special materials all yield a morphology that is similar to multilayered structure after the resins are extruded into thin film. Different from some previous researches [5, 6, 7], our technique involves with a precompound process, which ensure the multilayer morphology to form after resins are extruded into thin films. With multilayer-like morphology inside, EVOH phase is extended and protected. Therefore, good gas barrier (both OTR and WVTR) properties agreeing with series model calculation are reported for all film samples. These materials with multilayer-like morphology have also shown decent adhesion with different PE reins, so 3- layer instead of 5-layer films are successfully fabricated, which are applicable in barrier packaging applications in terms of barrier and optical properties. It is expected that these special materials with multilayer-like morphology inside can be used as monolayer films or a layer in multilayer structures to enhance the barrier performance as well as process flexibility of EVOH resins.
Electrospun nanofiber membranes consisting of Polyvinylidene fluoride-co-hexafluoropropylene blended with nanosilica nanocomposites were successfully prepared using electrospinning technique in this paper. The neat PcH, PcH-nanosilica, and Pch-modified nanosilica nanocomposite membranes were characterized by water contact angle, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Results showed that the addition of nanosilica increase the hydrophobicity of the membranes. Blended with 5 wt% modified nanosilica, the water contact angle of membrane could reach up to a maximum value (136°). Membrane morphological analysis presented that the resultant membrane had the thinnest diameter and roughness surface, which confirmed the enhancement of hydrophobicity of the membrane.
Polystyrene (PS)/Polyamide 6 (PA6) film with highly-oriented and aligned PA6 ribbons in PS matrix is prepared by the tape extrusion. Using carbon dioxide (CO2) as a blowing agent, the foaming behavior of this multilayered PS/PA6 film was studied at foaming temperature lower than melting temperature of PA6 and higher than transition glass temperature of PA6. The results show that the cell size of the obtained foam is smaller than that of pure PS foam because the solid PA6 ribbon not only acts as heterogeneous agent but also can restrict cell growth. Moreover, the cell is oriented along the direction perpendicular to the ribbons direction, which exhibits anisotropic mechanical properties.
Polypropylene (PP) foams with a low thermal conductivity (less than 40 mW/m·K) and a low density (0.1-0.2 g/cm3) were fabricated by the foam injection molding technology with mold opening while using CO2 as a blowing agent. PTFE fibrils manufactured by in-situ fibrillation using a co-rotating twin screw extruder were used to improve the melt strength and the strain hardening property. The crystallization behavior and the rheological properties were studied, to demonstrate that the dispersed PTFE fibrils effectively enhanced the crystallinity and, thereby, increased the melt strength, and induced a strain hardening behavior. When foamed in injection molding, the fibrillated PTFE containing PP showed much more improved foaming behavior. The thermal conductivity mainly depended on the expansion ratio of foam, although the quality of the cells (i.e., the size and uniformity) also influenced those properties.
The morphology and thermal properties of poly(propylene carbonate) (PPC) and hydrogenated nitrile butadiene rubber (HNBR) blends obtained via a meltmixing process were studied. Morphology of the blends with different compositions was observed by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were performed to study miscibility and thermal stability of the blends. SEM image showed that PPC/HNBR blends are phase-separated at the microscopic scale and each phase showed characteristic Tg in DSC. The addition of HNBR is demonstrated as a mean to significantly improved thermal stability of PPC phase under air atmosphere.
The cotton candy method was used for preparing polyacrylonitrile (PAN) nanofibers. Molecular weight (MW) of PAN was 15x104 and 20x104 g/mol. The PAN was dissolved by N-Methyl-2-pyrrolidone (NMP). The concentration of PAN solution was varied at 3-10 wt%. The PAN solution was spun through the plunger at the speed of 100 and 1,000 rpm at air pressure of 0.2 MPa. The collecting distances were set at 20, 40, 60 and 80 cm. Morphology of the fibers was observed by scanning electron microscope. The PAN nanofibers were successfully formed at 10 wt% of PAN MW 15x104 g/mol and 5wt% of PAN MW 20x104 g/mol. The fiber diameter decreased when increasing the collecting distances. The average fiber diameter was around 400-650 nm. The glass transition temperature and the oxidative degradation increased when increased the concentration of PAN. Raman spectrometry of carbon nanofiber by PAN nanofibers from CoCaM showed high crystallinity. and stretched strongly and alignment.
Multiple options exist for decreasing the weight of injection molded automotive components. Each option offers unique advantages and limitations regarding weight reduction potential and mechanical performance of the final part. Advanced Composites has evaluated the effect of several strategies, including composite density reduction, wall thickness reduction, and foaming, on the performance of injection molded test specimens and parts made using a diagnostic tool. Densities and part weights were obtained as well as tensile, flexural, and impact properties. In the case of density reduction, the removal of mineral filler alone proved insufficient to maintain mechanical performance, indicating the need for optimization of the material formulation. The characteristics of foamed and thin-wall parts were also examined and demonstrate the need for careful consideration of part and material design.
Automotive industries are promoting and working to improve the sustainability of their vehicles by using materials, which includes increasing of recycled and lightweight materials. Increasing recycled materials is to improve resource efficiency by recycling consumer and industrial waste and increasing lightweight materials is to improve vehicle fuel efficiency by expanding the use of lightweight materials. An automotive prototype (oil pan) is developed from 100% recycled material (20 wt% recycled carbon fiber with 80 wt% recycled polyamide) to improve fuel efficiency by light weighting and as well as sustainability. The material properties and processing parameters are compared to current production part. A global thermal cycling durability test of prototype part has been performed where the continuous high temperature is mainly concerned. It is found that the prototype part is 15% lighter than current part and as well as lower processing time. The prototype part has successfully passed the global thermal cycling durability test.
Thermally conductive compounds are viewed as potential replacements of metal based heat sinks in automotive and non-automotive LED lamp applications. Graphite is certainly the main candidate for thermally conductive applications that tolerate electrical conductivity for their high efficiency and reduced costs. In this article we demonstrate that the introduction of graphite increases substantially the thermal conductivity especially along the plastic flow (in plane) direction. We have tested several commercially available graphite grades in polyolefin model polymers and have seen that the crystallinity, the average particle size and the aspect ratio are the three main factors that promote thermal conductivity. In this comparative study we have also tested special high aspect ratio graphite that delivers high thermal conductivity at low loadings giving an advantage in terms of weight reduction.
The materials for vehicle light guide rod or liquid crystal display need superior optical and heat resistance properties. In conventional polycarbonate, these properties were improved by adding a general heat stabilizer. A search was made for new additives effective in any other properties. As a result, it was found that heat resistance and optical properties are improved dramatically by adding combinations with specific PAG and additives. The key properties for commercial production are molding retention time and weatherability. Results revealed that both properties were sufficient to use in vehicle light guides. Improvement of optical, heat aging properties, retention molding, and weatherability of the improved polycarbonate was examined.
Laser Direct Structuring (LDS) is a type of Molded Interconnect Device (MID) that uses optimized plastics which are compounded with special pigments. The LDS method is often times used for producing antenna and circuitry components. Aside from thermal stability, common requirements for plastics in these applications are good mechanical strength, dimensional stability, and stable radio frequency properties at operating ranges of high frequencies. Mitsubishi Engineering Plastics currently produces polycarbonate, polybutylene terephthalate, and aromatic polyamides for LDS. Newer polycarbonates and polyamides which are suitable for soldering are being developed at this time as well.
The objective of this work is to study the rheological characteristics of the compound of polycarbonate resins with different melt flow indexes and the affects of the processing parameters PC1 content (30wt%-pph) of MFI (25gm/10mins) and PC2 content (70 wt. %-pph) of MFI (6.5gm/10mins). By understanding the relationship between shear rate and viscosity, it becomes possible to define the viscosity model and exact color shifts. The temperature was varied at three stages (230°C, 255°C and 280°C) to study its effect on rheological characteristics, colour differences (dE*), pigment size distribution and dispersions.
A sustainable resource in the form of chicken feather derived keratin was used to enhance the thermo-mechanical properties of polysiloxane-polyurethane bio-composites. Two methods, solvent–casting–evaporation–compression molding, and solvent–precipitation–evaporation–compression molding were used to create new bio-composites incorporating 20 %·w/w of chicken feather fibers into a polysiloxane-polyurethane matrix and the results were compared. A molecular modeling visualization indicated the possible existence of hydrogen bonding between fibers and polyurethane molecules. The thermo-mechanical properties of both the polysiloxane polymer and feather reinforced bio-composites were assessed using thermogravimetry, dynamic mechanical analysis and stress–strain measurements with hysteresis loops. The dispersion uniformity of the keratin fibers in the plastic matrix was investigated via macro photography. Addition of chicken feather fibers to the polysiloxane matrix was found to decrease the recovery strain and mass loss of the composites (at lower temperatures) but increase the elastic modulus, storage modulus, and char level (at higher temperatures). The results demonstrate that keratin derived from what is currently a waste product from the poultry industry (with significant economic and environmental disposal costs) can improve the thermo-mechanical properties of the tested bio-composites simply and cheaply, with potentially large cost savings and environmental benefits.
Thermoplastic foams have been explored for their use as scaffolds for bone tissue engineering. Challenges exist in their applicability and strategies for enhancement in mechanical properties are needed. In this paper we report the fabrication of hybrid polymeric-metallic foams where magnesium was electrodeposited on polyurethane foams with the goal to enhance the mechanical properties of polyurethane foams. The foams were characterized using visual methods and optical microscopy techniques, which clearly showed the presence of magnesium fused foams.
Weld lines are rather well known as optical and/or mechanical blemishes in plastics products that can be avoided barely by mold design or process control. Although many publications show single solutions to optimize weld line strength in injection molded parts, there is no complete comparison of thermoplastic polymer materials available. Therefore, an overview about formation, morphology and strength of weld lines for amorphous, semicrystalline and filled polymer materials is given.
Capillary Rheology has been around for many years. As technology moves on, this has opened doors to use the capillary rheometer as a base on which to build a sophisticated R&D platform to perform a wide range of other tests, which help rheologists and their colleagues. We look at extensional rheology, elasticity, pressure- volume-temperature (PVT), thermal conductivity (TC), sharkskin analysis and the effects of counter pressure measurements. Those are but a few of available options to lab managers who try to squeeze out extra capabilities from their budgets.
Analysis and results are presented to model the melting of a single pellet in an extrusion screw. The analysis considers transient heat conduction with a convention boundary condition and three sources of internal generation. The results suggest that the theoretical melting time for a pellet is on the order of seconds and more optimal extrusion screw designs are possible.
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