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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Our industry leading separation technology enables us to recover polyolefin and styrenic plastics from complex mixed streams such as shredded end-of-life vehicles. Plastic flakes recovered using our process are compounded and sold as pellets suitable for use in injection molding and extrusion applications. This paper looks at some of the challenges of understanding and controlling the properties of the polypropylene product, including a discussion of how infrared spectroscopy and statistical analysis of the spectra may be used to rapidly measure the mechanical properties.
Oral solid dosage forms are the most patient-accepted and therefore industrially relevant pharmaceutical applications, representing 80% of the market share. In that context, polymer processing techniques, such as hot melt extrusion (HME) or injection molding (IM), are increasingly used to process primary material into the final dosage forms due to several benefits (e.g., enhanced solubility or solvent-free processes). In this study, tablets based on solid dispersion systems were processed via injection molding using either primary powder or pellets prepared by HME. Fenofibrate, a BCS Class 2 substance (low solubility, high permeability), was selected as model API, with loadings of 10%, 20% and 30%, while Soluplus® (PVCL-PVAc-PEG co-polymer) served as matrix. It could be shown that both the achieved mechanical properties (e.g., hardness) of the tablet, as well as the release kinetics, are suitable for oral dosage forms.
In this study, a novel co-rotating non-twin screw extruder with a clam-shell barrel was designed and invented. Then, the visualization of mixing an 80/20 (wt%) ratio HDPE/PS blend was carried out after the barrel was opened. The morphological development of HDPE/PS blends in this non-twin screw extruder was studied. Two groups of operating conditions were employed when the ratio of the screw speed to the feed rate was kept constant. The effects of the screw speed on the morphological development of the HDPE/PS blends along the axial direction during extrusion were discussed. The results revealed that coalescence happened during extrusion, and increasing the screw speed resulted in a smaller droplet size and a narrower size distribution of the product. The dispersive mixing was stronger in the nip zone than in the screw channel. In addition, it was found that the morphology pattern changed considerably and the particle size decreased sharply and became more uniform after the blend went through the holes of the die.
Recently, polymeric optical lens have been utilized in many fields and electronic devices, such as camera, mobile phone, tablet, and other optical devices. The quality is the key for the main suppliers to keep competition, however, how the material’s viscoelasticity influences the optical features is still not fully understood yet. In this study, we have investigated the viscoelastic effects on the optical property of a lens made of Zeonex COP 480R material by the traditional injection molding, simulated with n = 0.4 and ?* = 217,000 Pa in the Cross model for the melt viscosity. Results show that if the power-law index (n) was varied from 0.1 to 0.6, the total fringed order has no significant difference, but the fringed patterns were varying dominantly in the perpendicular direction, instead of the flow direction for the case at n = 0.4. This situation was matched with the distribution of the flow-induced residual stresses. Moreover, if the ?* in the Cross model was varied from 100,000 Pa to 300,000 Pa, the total fringed patterns were apparently changing from being dominated in the flow direction to being in the direction perpendicular to the flow. The influenced width of the fringed patterns was almost linearly increased with the increasing ?*. The results can be applied as some guideline for either the further material modifications or the new material developments.
The gas-assisted injection molding (GAIM) process is so complicated that increasing reliance has been placed on CAE?Computer Aided Engineering?as a tool for both mold designers and process engineers. In this paper, a 3D theoretical model and numerical scheme is presented to simulate the GAIM process, in which an equal-order velocity-pressure formulation method is employed to eliminate the pressure oscillation. In addition, the whole flow field is calculated with the gas pressure as a boundary condition to obtain the gas penetration, and a 3D control volume scheme is employed to track the flow front of the melt and gas. Finally the validity of the model has been tested through case studies and experimental verification.
Our industry leading separation technology enables us to recover a variety of plastics from complex mixed streams such as shredded waste electrical and electronic equipment (WEEE). Plastic flakes recovered using our process are compounded and sold as pellets suitable for use in injection molding applications. Polyolefin and styrenic plastics have been in our product portfolio for nearly a decade, but recently we have been expanding our range of plastic products. This paper looks at the challenges of recovering additional plastics and the properties of PC/ABS we have recovered from shredded WEEE.
In this study, temperature profiles for the air inside the mold was measured to analyze the thermal behavior of a polymer for a complete rotational molding cycle. Foamed and unfoamed linear medium density polyethylene (LMDPE) parts were produced by biaxial rotational molding. A chemical blowing agent (azodicarbonamide, ACA) was used at different concentrations (0, 0.25, 0.50, and 1.0 % wt.). The temperature profiles inside the mold were measured for different oven temperatures (260-320 °C). The analysis proposed is based on the temperature profiles and their derivatives to better determine the different temperature transitions occurring in a complete molding cycle.
Recently, polymer electrolyte fuel cell (PEFC) cogeneration systems using plastic pipes for hot water supply have been commercialized in Japan. However, it is expensive and difficult to replace these plastic pipes if they are damaged. Therefore, it is important to evaluate the durability and to predict the life expectancy of these pipe materials and systems. In this study, the immersion test was used for polybutylene (PB) and double-layer crosslinked polyethylene (PEX2) pipes to evaluate their long-term performance in the residual chlorine solutions at 80 °C for 30,000 consecutive hours. The mechanical and thermal properties of these pipes were investigated using tensile test and DSC. Based on the tensile test results, it was found that the elongation at break rather than the yield stress had a strong correlation with the melting enthalpy (?H) of the PB and PEX2 pipes. On the other hand, the DSC results revealed that the oxidation induction time (OIT) at the inner surface of the PB and PEX2 pipes decreased significantly with immersion time, in which the OIT of the PB pipe decreased more rapidly than that of the PEX2 pipe. The difference in the OIT behavior was discussed in terms of the influence of the residual antioxidants in these pipes.
The mixing process of a halogen-free intumescent flame retardant ABS composite was carried out to examine the priority of a novel co-rotating non-twin screw extruder (NTSE) over the traditional twin screw extruder (TSE). The homogeneity of the flame retardant additives of the composites processed by NTSE and TSE under the same operating condition was characterized qualitatively using mechanics performance, LOI and UL-94 tests, and quantitatively using FTIR and TG analysis. All the results suggested that NTSE could achieve better mixing of the flame retardant additives in the polymer matrix than in TSE, which was further clarified by the SEM analysis.
Thermal analysis (TA) techniques are indispensable tools for polymer characterization and root cause analysis of various problem such as contamination and part failure. Thermal analysis were carried out using Thermo-Gravimetric (TGA), Differential Scanning Calorimeter (DSC) and Hot Stage Microscopy techniques were used to study compatibilization of blends. This study related Polyethylene terephthalate (PET) as major phase) with minor amounts of Polycarbonate (2%PC) and Polyethylene-liner-low-density (3-5% PE-LLD). PC is fully miscible with PET in a molten state or when it exists in infinitesimal domains. The binary (PET/PC) blend’s matrix yields a homogeneous phase in thermal analysis. Degradation kinetics (single degradation peak) suggests that PET/PC is a binary miscible blend. On the other hand, PE-LLD is immiscible with PET even in a minor concentration; a pronounced skin-core effect was observed in hot stage microscopy and a doublet degradation peak was observed in TGA. In a ternary blend (PET, PC and PE-LLD), surprisingly the PC acts as a compatibiliser for the PE-LLD in the blend matrix. The degradation doublet peak in ternary blend due to PE (TGA) was minimized and crystallinity of ternary blend (DSC) was increased than the binary blends. Therefore, ternary blend appears as a homogeneous matrix in all three TA techniques used.
A numerical simulation for elastomer foaming extrusion process was made. Energy equation coupled with unit cell model were used and solved by Radial Basis Function (RBF) and Finite Difference Method (FDM), respectively. The curing reaction, the change of viscosity and the concentration of the gas inside the rubber are also taking into account. The effect of processing parameters as temperature of vulcanization and the velocity of the profile inside the tunnel were evaluated and the resultant bubble size and its distribution were analyzed.
As American vehicle fuel efficiency requirements have become more stringent due to the CAFE standards, the auto industry has turned to thermoplastic-fiber composites as replacements for metal parts to reduce weight while simultaneously maintaining established safety standards. Furthermore, these composites may be easily processed using established techniques such as injection molding and compression molding. The mechanical properties of these composites are dependent on, among other variables, the orientation of the fibers within the part. Several models have been proposed to correlate fiber orientation with the kinematics of the polymer matrix during processing, each using various strategies to account for fiber interactions and fiber flexing. However, these all require the use of empirical fitting parameters. Previous work has obtained these parameters by fitting to orientation data at a specific location in an injectionmolded part. This ties the parameters to the specific mold design used. Obtaining empirical parameters is not a trivial undertaking and adds significant time to the entire mold design process. Considering that new parameters must be obtained any time some aspect of the part or mold is changed, an alternative technique that obtains model parameters independent of the mold design could be advantageous. This paper continues work looking to obtain empirical parameters from rheological tests. During processing, the fiber-polymer suspension is subjected to a complex flow with both shear and extensional behavior. Rather than use a complex flow, this study seeks to evaluate and compare the effects of shear and extension on two orientation models independently. To this end, simple shear and planar extension are employed and the evolution of orientation from a planar random initial condition is tracked as a function of strain. Simple shear was imparted using a sliding plate rheometer designed and fabricated in-house, and a novel rheometer tool was developed
The effects of blend composition and foaming conditions on polylactic acid (PLA)/thermoplastic polyurethane (TPU) blend foams were studied. Thermal behavior of the blends showed that TPU weakened crystallization ability of PLA. It was found that foam morphology was impacted by the blend composition and foaming conditions used in the study. PLA and PLA/TPU (80/20) did not demonstrate any significant foaming behavior while PLA/TPU (50/50) foamed at high temperature and pressure conditions. TPU foam morphology demonstrated temperature and pressure dependence. Interestingly enough, PLA/TPU (20/80) showed pore formation at all the operating conditions with either open cell or closed cell structures.
This paper aims to provide fundamental understandings in several issues critical to the fabrication of auxetic polyurethane (PU) foams: auxetic structure fixation mechanisms, materials characteristics essential for the successful auxetic conversion, and optimal conditions for auxetic conversion. The chemistry, microstructure and thermomechanical properties of starting PU foams for auxetic foam manufacturing were thoroughly analyzed. This is followed by the auxetic convertibility study of these three foams. Mechanisms for fixing the structure were elucidated and the windows for processing were interpreted in the context of polymer relaxation. Guided by these understandings, we finally report an ultrafast, room-temperature process for auxetic PU foams manufacturing that can be completed in as little as several seconds.
This study employed the J-integral approach to investigate the effect of recycled HDPE and nanoclay contents on the long-term stress cracking behavior of pristine HDPE. This behavior was conventionally approached by using stress intensity factor K, which defined the stress cracking behavior as two failure mechanisms: creep and slow crack growth (SCG). Unlike the conventional approach, the J-integral method identified the short-term failure prior to the creep failure. By integrating the short-term and SCG failure behavior, this study derived a correlation between Jc and SCG. The SCG behavior of recycle-blended materials without nanoclay was governed by Jc which decreased as the recycled contents increased. The decrease of Jc led to a reduction in SCG failure time. In contrast, the addition of nanoclay (up to 6-wt%) reduced Jc and stress relaxation of the material, subsequently extending the SCG failure times.
This study set out to apply gas counter pressure (GCP) in the injection molding process. By importing gas through the ends of the cavity, the melt was exposed to a melt front pressure, which, together with the packing pressure from the screw, is supposed to reduce product shrinkage. The aim was to investigate the impacts of GCP on the process parameters via the changes in machine feedback data, such as pressure and the remaining injection resin. This study also used a relatively thin plate-shaped product and measurements, such as the photoelastic effect and luminance meter to probe into the impacts of GCP on product residual stress, while a relatively thick paper-clipshaped product was used to see the impacts of GCP on shrinkage in thick parts. According to the experimental results, the addition of GCP resulted in increased filling volume, improvement of product weight and stability, as well as effective reduction of section shrinkage, which was most obvious at the point closest to the gas entrance. The shrinkage of the sections parallel and vertical to the flow direction was proved to be reduced by 32% and 16%, respectively. Moreover, observations made via the polarizing stress viewer and luminance meter showed that the internal residual stress of a product could be effectively reduced by a proper amount of GCP.
Advanced film capacitors require polymers with high thermal stability, high breakdown strength, and low loss for high temperature dielectric applications. In order to fulfill such requirements, two polymer multilayer film systems were coextruded via a forced assembly technique. High glass transition (Tg) polycarbonate (HTPC) and polysulfone (PSF) were layered with poly(vinylidene fluoride) (PVDF), respectively. The PSF/PVDF system was more thermally stable than HTPC/PVDF system. For dielectric properties at high temperature, PSF/PVDF system exhibited higher breakdown strength and lower hysteresis compared with HTPC/PVDF system. These results demonstrated that PSF/PVDF was a superior system to HTPC/PVDF for high temperature dielectric capacitors.
Radiative thermal conductivity has long been recognized as an important heat transfer mechanism. In the literature, a heat transfer of 20% to 40% through low density thermal insulation materials has been reported. Adding particles such as carbon nanotubes can significantly reduce the radiation by absorption and scattering. In addition to its cost effectiveness and easy processability, the expanded graphite was expected to absorb thermal radiation more efficiently than carbon nanotubes with the same volume content. Using the Rosseland approximation, we quantitatively undertook a first-time study of how expanded graphite significantly reduces the radiative thermal conductivity. We found that particle-added polystyrene foams with a 0.018%vol of expanded graphite nanoplatelets and a 25-fold volume expansion ratio could block 92% of the overall thermal radiative thermal conductivity. A 19.6 mW/m.K of the total thermal conductivity of these foam composites was experimentally achieved. This was due to the extremely high volume expansion (>40- fold) and to the efficiency in attenuating the thermal radiation via the polymeric foams. When we used the Glicksman model for thermal conduction together with the Rosseland approxiamtion, the calculated values of the total thermal conductivity were all in good agreement with the experimental data, and the tolerance was less than 5% (<2 mW/m.K).
Mechanical properties and thermal properties of cellulose- PLA composites were measured. The relation between molecular structure of additives and an addition effect on cellulose-PLA was investigated. By examining for combination of three kinds of cellulose material and four kinds of additive of different features, effects of additives to PLA and cellulose and their mechanism were revealed. It was found there was the most improvement of mechanical properties using hydrophobic additives with many functional groups. It was assumed that reactive additives made a crosslinked structure in cellulose-PLA composite.
Due to the wide range of properties of plastics (e.g. low density), more and more conventional materials are substituted by polymer materials. Complex requirement profiles on technical parts increase the demand for joining processes that enable the reliable joining of otherwise incompatible thermoplastics. In this case, material bonded connections are approaching their limits. In the following study two incompatible thermoplastic polymers were welded by using polymer blends that are compatible to both components. Industrially relevant thermoplastics polyethylene (PE) and polyamide 12 (PA12) were chosen to demonstrate the potential of an innovative joining technology.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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