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.
Polylactide (PLA) is a bioplastic which has a high potential for packaging applications. Due to a high raw material prize and a limited availability the usage of PLA is limited apart from some niche products at the moment. Nevertheless, the number of applications is increasing. At the Institute of Plastic Processing (IKV) the recycling behavior of PLA is evaluated. Recycling helps to cut the raw material consumption and lowers material costs. Additionally, it improves the ecological balance. Following the industrial praxis different recycling strategies are analyzed. This paper gives a review about the multiple processing of PLA and the processing with melt degassing.
The foaming of rubber products offers saving potential with respect to component weight, material consumption and costs, while damping properties can be improved. For foaming of high-temperature vulcanizing (HTV) silicone rubber, the use of chemical blowing agents is state of the art. Physical blowing agents such as inert gases have ecological, economical and process-engineering advantages. This paper presents results of a current research project focusing on the development of a continuous process for the physical foaming of solid silicone rubber using nitrogen as blowing agent. The main aim is the achievement of a constant process in order to produce homogeneously foamed rubber profiles and the identification of quality-determining parameters.
Replicating microstructures for functional surfaces in a fast and economic way is crucial for many technical applications. In this paper an experimental study on the variothermal extrusion embossing is presented. Polyethylene and polypropylene grades are used to manufacture hydrophobic films. Microstructure geometries as well as static and dynamic surface behavior in contact with purified water are analyzed. A theoretical approach to estimate the distinctive temperature profile that is generated according to processing conditions (e.g. haul-off speed, temperature of the embossing roll, etc.) is verified experimentally. Thus, the assumption is confirmed that a set of processing conditions (responsible for a specific replication accuracy) can be transferred to another set of conditions while keeping the replication quality constant.
Centering errors in the alignment of the surfaces of optical lenses lead to aberrations. In spite of very precise molds and processes, a lateral offset between the two mold halves and therefore between the optical inserts occurs and leads to centering errors in the replicated optical components. A newly developed mold design with integrated piezo-actuators allows the adjustment of the die-sided optical insert and with it the minimization of the centering error. Therefore it is possible to influence and reduce the geometrical error and raise the optical performance of plastics lenses without a machining of the mold.
Injection molding is the most important process to manufacture complex polymer parts. However, today the injection molding of elastomers almost entirely produces solid workpieces. Functionalized complex hollow components, e. g. for the conduction of medias, are often manufactured in costly multistep processes. The projectile injection technique offers a new approach to easily produce elastomers in a one-step process into complex hollow parts. This paper discusses the requirements on peripheral equipment and mold design and gives impressions of the effect of the process parameter variations on important quality criterias for this innovative process.
The market for mechatronic actuator devices in the automotive sector, as well as in the field of white goods (household appliances), brown goods (home entertainment), and red goods (air conditioning in buildings) has been growing constantly throughout recent years [1, 2]. During use, the actuators not only have to mechanically withstand the nominal load, but often also higher peak loads. Peak loads occur, for example, in the case of blocking, reaching the end position of the adjustment rail of a car seat or a car mirror. There are four commonly used approaches for overload protection: adjustment of component to applied load over-sizing of mechanical parts - limiting load electrical current limitation - use of sensors use of a mechanical overload protection system. An over-sizing of machine elements, e.g. gears, is easily achievable but not desirable, since overall weight and costs increase. Electrical current limitation and use of sensors are almost weight-neutral, since the circuit board will be extended by only a few electronic components. However, with a higher level of complexity, the risk of defects rises and overload protection in an unpowered state, e.g. for the case of vandalism, is not possible. Another approach is the use of a machine element with an integrated mechanical overload protection, such as a friction clutch. A friction clutch combines the function of motion transmission and mechanical overload protection. A benefit is its full function in an unpow-ered state, which thus provides effective protection against vandalism. The technology of assembly injection molding opens up an economic way to produce these plastic multi component machine elements, see Fig. 1. When made by assembly injection molding, additional costs due to a more complex mold have to be taken into account, though, by using function integration within transmission components, this cost increase can be kept low. Well-defined design should allow weight and com
Polymer based nanocomposites are fabricated through the incorporation of nanoscale inorganic solids into polymeric matrix. The focus of this research was on the production and rheological investigation of polylactide (PLA) and nanographite platelets (NGP) based bionanocomposites. In the current study, the linear viscoelastic behaviour of the samples was investigated in order to study the effects of the enhanced dispersion of NGP fillers on the rheological properties of the nanocomposites. Uniaxial extensional experiments were also carried out to analyse the impacts of the nanofillers on linear viscoelastic envelope (LVE) and non-linear viscoelastic behaviour (strain hardening region) of the nanocomposites. Furthermore, in order to provide an accurate prediction of the extensional viscosity behaviour of PLA/NGP nanocomposites, the modelling of strain-hardening behaviour of neat PLA and its nanocomposites was investigated using steady shear viscosity, relaxation spectrum and damping function based on Papanastasiou-Scriven- Macosko (PSM) version of Kaye-Bernstein-Kearsley-Zapas (K- BKZ) model.
This paper describes the evaluation of the mechanical properties and flame resistance on bio-based polymer compounds of Poly (lactic acid) (PLA) and Polyamide 11 (PA11). A compounding technology and mechanical properties of PLA and PA11 using a compatibilizer were firstly studied to improve the thermal resistance and the impact strength of PLA. Some compositions of PLA/PA11 blends using a compatibilizer were investigated. After some flame retardants which were not halogenated and toxic materials were blended to the composition of PLA/PA11/compatibilizer, the mechanical properties and flame resistance were also evaluated as compared with the commercialized PLA and Polycarbonate (PC) alloy. The flammability test was conducted with the multi-cone calorimeter to obtain the relation between the heat release rate or the integrated heat release value and the combustion time.
For the design of injection molded parts made of short-fiber-reinforced polymers, the anisotropic, geometry- and temperature-dependent thermal expansion coefficient (TEC) is often needed at the early stages of the design process, for example during material selection. The data usually available from material suppliers does not consider temperature dependency and the influence of geometries such as part thickness. State-of-the-art calculation methods such as the rule of mixture neither include these effects. Hence the development of simple models designed to estimate the TEC at the early stages of development is of interest. This paper deals with a method for engineers working in research and development to calculate the geometry- and temperature-dependent anisotropic TEC of parts made from short-fiber-reinforced polymers under consideration of fiber orientation. To evaluate the validity of the method, the results from the calculations were compared to measurements conducted on parts of different thicknesses. Here a good correspondence with the anisotropies of the TEC in different part directions was achieved.
Poly(ethylene terephthalate)(PET)/graphene nanocomposites were prepared by melt mixing to characterize their gas permeability and mechanical properties. With 2 wt% of few layered graphene, PET/graphene composite films show more than 70% decrease in N2 gas permeation and 10–21% increase in storage modulus, E'. Their non-isothermal crystallization phenomena from the melt were also investigated by differential scanning calorimetory (DSC). Crystallization temperature, Tc, of PET/graphene nanocomposites was higher than that of PET/MWCNT nanocomposites. This suggests that the nucleation effect of graphene was higher than that of MWCNT and was enhanced with the increase in concentration of graphene. On the other hand, PET/graphene nanocomposites show shorter half crystallization time, t1/2, than neat PET at lower concentrations, and t1/2 increased along with concentration of graphene. From Raman spectroscopy, it was shown that PET chains in nanocomposites are confined strongly in the presence of an excess of graphene. This confinement effect suggests that crystal growth rate of PET was suppressed by graphene in nanocomposites.
The addition of peroxides as a dispersing additive for multiwalled carbon nanotubes (MWCNT) incorporated in polypropylene is investigated with Raman spectroscopy both in the melt and on the extruded composite. Peroxide addition results in lowering of the melt viscosity of PP in addition to enhancing the defect concentration of the MWCNT. The better melt infiltration due to the former and evidences of CNT functionalization from the latter result in improved MWCNT dispersion quality in PP.
Presenting and explaining the functions and history of the planetary extruder. Covering the advantages in physical characteristics, to include contact surface availability per rotation of the central spindle, Energy exchange capabilities (thermodynamics), control of mechanical energy and mixing properties. Technical advances made over the years in areas of manufacturing and employment of the planetary extruder in areas of de-gassing possibilities, individual blending of raw materials, liquid injection, mass- temperature and pressure measurement, control over fill degrees and residence times. Showing the advantages and applications of a modular built planetary extruder, in the adaptation of dis-continuous production processes into continuous processes. Introducing areas of application where the planetary extruder has shown major advantages and is used today throughout the world.
One of the most under-utilized tax savings opportunities for companies in the plastics industry is the U.S. Credit for Increasing Research Activities (R&D tax credit). The R&D tax credit rewards companies who invest resources in innovation, product development, mold design, new materials or resins, and process development/improvement. In addition to Federal tax savings, several states have a similar program that rewards companies for the development or improvement to its products or processes. The types of activities that may qualify for the R&D tax credit include, but are not limited to the following: Developing new product designs Improving functionality or reliability or existing products Designing new molds or improving transfer molds Experimenting with processing variables to improve processes Improving manufacturing processes through automation Experimenting with new resins Performing PPAP or First Article inspections on new parts This article will discuss the following: The types of activities that may qualify for the R&D tax credit The types of expenditures that are eligible for the R&D tax credit The different methodologies for calculating the R&D tax credit The types of documentation necessary to substantiate a R&D tax credit claim The determining factors of whether the costs of externally-produced molds may be included as qualified expenditures The possible utilization of the R&D tax credit to offset taxes paid up to five years ago A case study of a plastics processor claiming the R&D tax credit
A twin-screw extrusion process for PETG/clay nanocomposites using supercritical carbon dioxide was studied. Well-dispersed nanocomposites enhance the superior properties of the PETG/clay nanocomposites. So, we studied to achieve a good dispersion of the individual silicate layers of the clay. For even more enhancement of the dispersion of the clay in polymeric phase, supercritical CO2 can be employed in the processing of the nanocomposites due to the fast diffusion into the clay particles. The properties of PETG/clay nanocomposites are investigated by rheometer, thermal analyzer, permeability tester, and mechanical tester. The effects of clay contents and CO2 feed rate on the rheological and barrier properties of PETG/clay nanocomposites are presented. The results show that the rheological and thermal properties of the nanocomposites increase with the addition of clay. From the permeability test of nanocomposites, the barrier properties also increase. Moreover, the analysis of the nanocomposites also reveals that the use of supercritical CO2 leads to an increase of the rheological and barrier properties. From the results above, we strongly suggest that the use of supercritical CO2 assisted twinscrew extrusion is an effective way to improve the superior properties of PETG/clay nanocomposites.
In this study, polystyrene / carbon nanocomposite foams were made by in-situ polymerization and solution compounding. The foam was made by batch foaming using CO2 as the blowing agent. Various carbon nanomaterials such as nanographite, carbon nanofiber (CNF), carbon nanotube (CNT) and thermally reduced graphene (TRG) were used as the nucleation agent. In addition, processing variables such as foaming pressures and temperatures were also studied. The results indicated that TRG is the best nucleation agent because it possesses the highest surface area among these carbon nanomaterials. The cell morphology changed dramatically in the presence of carbon nanomaterials. This discovery not only opened up a new route for producing foams of a similar structure at a low foaming pressure, it also created a new application for graphene nanomaterial.
Due to the ever increasing cost of energy, there is an increased demand of lightweight materials. Towards that goal, we need to take advantage of new material developments such as is the case of nanoreinforced polymeric composites. The use of nanoparticles has shown improvement in mechanical properties of fiber reinforced polymeric composites (FRPC) but with adverse effect on processability, thus fully understanding the manufacturability of these processes is critical. Vacuum Assisted Resin Transfer Molding (VARTM) is the primary molding technique considered due to its significant advantages over other molding techniques and large size capacity. In this process, permeability plays a key role in determining processability. Understanding how permeability of these nano-enhanced FPRC is affected by the addition of nanoparticles is the main focus of this study.
Numerous varieties of polymer nano-composites have been developed on the laboratory scale and characterized regarding their properties. These include, nanofiller based on exfoliated clay, nanosilver, carbon nanotubes (both single and multiple wall geometry), zinc oxide, silica, and graphene among others. Carbon nanotubes (CNT) are of particular interest as they play a special role when it comes to improving or creating electrical conductivity in a polymer matrix. Currently most CNT based nano- composites are produced on co-rotating twin-screw compounding extruders via split feeding the polymer and the CNTs. However, processes using aqueous nano suspension are on the rise and offer new opportunities regarding technical performance, economical viability and reduction of health concerns related to the particle size of the CNTs. By using well pre-dispersed suspensions, which are already available on the market, it becomes easier to produce nanocomposites that provide the required characteristics, such as electrical conductivity. Also the usage of aqueous solutions enables dust-free handling of the carbon nanotubes. This presentation will introduce the Nano Direct Process and show its advantages in comparison to the conventional melt-mixing process.
The effects of multi-walled carbon nanotube (MWCNT) alignment on the electrical properties, i.e., electrical conductivity, electromagnetic interference shielding effectiveness (EMI SE), real permittivity and imaginary permittivity of MWCNT/polystyrene composites in the X-band (8.2 to 12.4 GHz) were investigated by comparing the electrical properties of injection molded samples, where MWCNTs were aligned, versus compression molded samples, where MWCNTs were randomly distributed. The results showed that the MWCNT alignment reduced the electrical conductivity and EMI SE tremendously. Nonetheless, it was observed that the MWCNT alignment significantly improved the dielectric properties of the MWCNT/polystyrene composites.
Extensive experimental studies on silica agglomerate breakup during compounding with polymer melts of various viscosities and polarities in a modular corotating twin screw extruder were conducted. Increasing the screw speed, melt viscosity and silica concentration were found to increase the silica agglomerate breakup. The effect of these parameters on agglomerate breakup was ranked as follows: silica concentration > polymer viscosity ?screw rpm. A good correlation between silica agglomerate breakage and power input was also found. A composite modular kinetic model for evaluating silica agglomerate breakup during compounding in a co-rotating twin screw extruder was developed. The kinetic constants of breakup and re-agglomeration of silica agglomerates were calculated based on the stresses applied to the agglomerates and their cohesive strength. These constants for silica agglomerates were found to be not significantly different at high concentrations. Comparison of the experimental and calculated results on the silica agglomerate size evolution during compounding with polymer melts indicated a reasonable agreement between them at high rotational speeds.
Bioplastic sheets made from plasticized meat and bone meal (MBM) protein have high water vapor permeability (WVP) and low mechanical properties that are further affected by environmental humidity. This paper describes the improvement of tensile properties and moisture resistance of the sheets by two routes: (i) chemical crosslinking of the protein with calcium ions and (ii) blending with a synthetic polyethylene. The calcium ions led to a rigid glassy state of the modified MBM with 4 and 6 times higher tensile strength and modulus, respectively, but no significant improvement in WVP. Blending of polyethylene with MBM significantly improved moisture resistance and tensile properties.
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