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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Modern injection molding machine technology is able to reproduce machine parameters, such as the movement of the axes, with high accuracy. Nevertheless, different boundary conditions, such as fluctuations in material properties or changes in ambient conditions, influence the quality of injection molded parts. Innovative control concepts can enable a production with a constant part quality despite changing and non-optimal boundary conditions. But these concepts do not take viscosity fluctuation into account although it changes the pressure distribution and thus the shrinkage behavior of the molded parts.
Within this paper, a temperature control setup of the hot runner for compensating different melt viscosities is introduced and implemented. Therefore, a temperature displacement law that regulates the temperature of the hot runner is developed and used to control the injection molding process. Its influence on the process and the part quality are investigated.
Thermal mold design is an important phase during mold construction and determines strongly the resulting part quality and cycle time. Nowadays, part geometries become more complex as well as cycle time becomes an increasingly important requirement.
To support the mold designer in generating an efficient cooling channel design with less iteration loops, a methodology is under development to indicate the location of the cooling channels. Based on the local cooling demand of the part, this methodology proposes an inverse approach where an optimal thermal state of the mold is calculated and a corresponding cooling channel design is derived. A objective function is used to calculate and evaluate the cooling quality of the resulting design. In a process simulation, the developed cooling channel design shows a reduction in part warpage of up to 75 % compared to a conventional thermal mold design.
It is known from literature [1, 2] that the rheological properties of polymer melts are influenced by the degree of long chain branching (LCB). Therefore, it is very important to understand the influence of LCB on the solid-state properties to help improve material design for unique applications. The objective of the present study is to demonstrate the use of extensional rheology as a tool to understand FR performance pertaining to dripping. Further, we also demonstrate the synergistic role of LCB in polycarbonate resins for improving FR performance.
A brief overview of discharge methods for continuous compounders is presented covering single-screw extruders, melt pumps, centrifugal pelletizers, pressure vessels, counter-rotating twin-screws, along with the B&P Littleford XLT twin-screw mechanism and Rotofeed System. These seven systems are critical subsystems of the entire extrusion process. Discharge methods for specialty processes, if designed correctly, can provide a constant pressure great enough for profile extrusion, continue mixing and/or reacting, cool, or pelletize the product. The correct subsystem can mean the success or failure of the entire process and is highly dependent on material properties.
Adhesively bonded joints are an excellent replacement of traditional mechanical joints in the automobile industry. In comparison to mechanical joints, adhesively bonded joints are lightweight and cost-effective in fabrication. Induction-based bonding is gaining popularity as they are relatively quicker than conventional oven techniques. However, the temperature distribution, phase change, and cure time are not as straightforward as conventional oven prepared joints. Thus, it is necessary to understand these parameters in an induction based heating method to produce better joints. In this research work, stress waves are transmitted between adherents that pass through the adhesive interface. The changes in transmission coefficient and Time of Flight (TOF) of guided waves (GW) helps in understanding joint conditions properties such as adhesive phase transition and time of cure during fabrication. A qualitative analysis is reported in this paper to prove the application of guided waves in process monitoring.
This paper investigates the potential of two concepts to extend an existing technique for simulating the melting process in high-speed-extrusion operations. The first concept is based on the so called Enthalpy- Porosity-Technique. A momentum sink will be implemented in the momentum equations to influence the velocity of the solid and umolten phase. The second concept deals with an adjustment of the current computation of the dissipated energy during phase change from solid to liquid. It is based on the idea that in a partially molten cell only the melt is exposed to shearing. A comparison of simulation results and microtom cut views from real experiment is carried out.
Additive manufacturing (AM) has revolutionized the way in which products are designed and manufactured, where parts are built from the ground up, layer upon layer. For polymer based additive manufacturing, we have improved upon that by applying an innovative strategy that allows for functionally gradient multi material printing with single extrusion head. The innovation incorporates a rotating nozzle that introduces a controllable shear rate of the polymer melt, altering the melt rheology. 3-D printing a couple of materials that have different melting temperatures into a single part is challenging, since the temperature of the nozzle has to be tuned constantly to match the melt temperature of the material being extruded to achieve a desired performance. Otherwise, over extrusion or under extrusion will occur due to the different viscosities of the materials. In this study, a 3-D printer with single extrusion head that can print different materials into one part without changing the temperature of the melt is proposed. The proposed technique also allows extrusion based 3D printing to precisely optimize products performance by mixing different materials. Keywords: Additive manufacturing, 3D printing, Multi material printing, PLA.
Polyester is the single largest fiber product globally. Owing to its physical properties, price, recyclability, and versatility, which offer a unique set of advantages unmatched by any other fiber like nylon and polypropylene, polyester BCF and staple fiber has become the fiber of choice in wide variety of applications, including in automotive applications. This market segment is projected to continue its growth at a faster pace in the next five years. We will review the key drivers, polymer and fiber process and product requirements, followed by test methods used for colorant selection and qualification. In the end, we will highlight colorants that are suitable and recommended for solution dyed polyester applications.
Fill time has long been regarded as the primary parameter to monitor and control during first stage filling of the injection molding process. Fill time is the result of a given first stage mold volume (shot volume) that is to be filled at a given volumetric flow rate. The most common industry method for evaluating the recommended fill time on the molding floor is known as the Rheology Curve or Relative Viscosity vs. Relative Shear Rate Curve (RV Curve). The RV Curve is one of the main principles taught worldwide in scientific molding courses in the injection molding industry. A company’s processing policies and procedures often reference the RV Curve as the method of choice for establishing an ideal volumetric flow rate and resulting fill time. Other methods may include the utilization of mold filling simulation software, personal experience based on similar parts and molds, or comprehensive Design of Experiments (DOE).
This study focuses on the RV Curve and calls the method into question from a mathematical standpoint based on the formulas used to derive the RV curve. The study also discusses an alternative method as a potential replacement to the RV Curve.
A commodity polybutene-1 (PB-1) resin has been chemically modified through reactive processing. Samples produced by using various amounts of peroxide have been analyzed in terms of their molecular and rheological properties. Molecular weight distributions (MWD) as determined by gel permeation chromatography (GPC) indicate that polydispersity (PDI) remains constant but weight-average molecular weight (Mw) decreases with increasing peroxide amount. Linear viscoelastic measurements indicate that the modified samples are thermo-rheologically simple, zero-shear viscosity decreases with increasing peroxide concentration and flow activation energy remains constant.
Thermoplastic elastomers (TPEs) can be defined as a class of special type of polymers, which exhibit hybrid behavior of thermoplastics and rubbers [1-3]. They can be processed like thermoplastics and at the same time can perform like rubber over a broad use temperature range. The thermoplastic elastomers’ sector has expanded at a compound annual growth rate of 5.4% since 2012 to reach 4.24 million tonnes in 2017. Even though TPEs are an increasingly mature market, Smithers-RAPRA research shows that this growth would continue at a rate of 5.5% across the next five years to hit 5.53 million tonnes in 2022 [4].
The melting behaviour in the single-screw extruder has to date been thoroughly researched, starting with MADDOCK, for example, who was already involved with this topic experimentally in the 1950s. The subsequent modelling of TADMOR in the 1960s also brought the melting to a mathematical background. The model considered was based on conventional melting, in which a solid bed and a melt eddy are formed. Another melting model is disperse melting, in which the solid particles are evenly distributed in the melt. This can be caused, for example, by high screw speeds or special screw geometries. However, the mathematical treatment of this model is not yet fully developed. Nevertheless, a higher melting capacity is predicted for the disperse melting model. Whether this statement is also independent of the extruder size will be investigated in the following, using an analytical mathematical comparison. For this purpose, the models of PAPE and POTENTE are used.
The target of this research was to fabricate and optimize a new 3D printable biobased material that can be used for biomedical applications that require biodegradability, biocompatibility and good mechanical properties. This research was successful in preparing a biobased filament made of 70% Poly (lactic acid) (PLA) and 30% Poly (butylene succinate) (PBS) and 3D printing this filament using Fused Filament Fabrication (FFF) technique. The rheological properties were investigated prior to 3D printing and the 3D printed specimens’ mechanical properties were compared to control specimen processed with injection molding method. The V-notched Izod impact testing of the 3D specimens showed about 30% higher impact toughness in comparison to the injection molded specimens.
In recent years, the increasing concerns on the widespread use of petro-based polymers and the pollution problems associated with their inadequate disposal and handling are driving the development of new and more sustainable polymers, especially biodegradable plastics obtained from renewable resources. The biodegradability of biopolymers depends on their physical and chemical properties, but also on the environmental conditions of the biodegradation media, on which depends the type and availability of microorganisms involved directly in the biodegradation process. Biopolymers showed biodegradability in compost, soil and marine conditions, however, presents different biodegradation rates when compared between these environments. For example, polylactic acid (PLA) showed an excellent biodegradation in compost. Conversely, in marine environment, PLA presented low mineralization rates, while polyhydroxyalkanoates (PHAs) presented an excellent biodegradation in marine conditions. In this sense, a biopolymer with a biodegradation rate around 10% may not be considered as biodegradable in any condition and their accumulation in ecosystems can result harmful. In this study, biodegradation of bioplastics under different environmental conditions are discussed.
Nanocellulose is a unique and promising natural material which is extracted from natural cellulose. The nanocellulose is gaining attention for its use in biomedical applications because of its remarkable physical property, special surface chemistry, excellent biocompatibility and low toxicity. In this study Polybutylene Succinate (PBS) with 5 levels of cellulose nanofibril (NFC) is being developed. The results demonstrate that the addition of NFC has modest effect on the thermal properties but improved the mechanical properties of PBS. The complex viscosity n* of NFC/PBS presents the shear thinning behavior. Furthermore, the water contact angle defines the hydrophilic nature of NFC/PBS composite.
The issue of plastic waste recycling and the idea of establishing a circular economy of plastics is receiving considerable interest from society, policymakers, and industry alike. A truly sustainable development in this field, however, can only be achieved when finding proper solutions to recycling challenges in world regions where formal waste management systems are lacking. In this work, polyolefin recyclates sourced from an informal waste picker community in Nairobi, Kenya were characterized in terms of material composition and basic mechanical properties. It was found that despite the absence of formal waste management systems in developing and emerging economies it is possible to produce technically useful recyclates that may compete with today’s commercially available recyclate grades.
Finding biobased fillers is growing more important as the need to use less petroleum-based plastics increases. Natural fillers provide advantages over non-natural fillers, such as glass and talc, in that they are typically lighter, biodegradable and renewable. These experiments were focused on increasing the interfacial bond in agave fiber (AF) - polypropylene (PP) biocomposites. Processing parameters, such as number of wash cycles the AF underwent, drying time prior to injection molding, and AF loading level were studied in order to characterize the mechanical properties of the composite formulations. It was found increasing the fiber loading level increased stiffness however reduced elongation as well as tensile strength. There were insignificant differences in tensile strength between the fibers that underwent no wash, one or, three wash cycles. In addition, the specific strengths were inversely proportional to the addition of AF into the composites. There was not observed a significant effect of drying time prior to injection molding on the mechanical properties.
The aim of this paper is to study the influence of combining two fillers on the coefficient of linear thermal expansion (CLTE) of polyamide 6 (PA6) hybrid nanobiocomposites. The influence of a new environmentally friendly filler (biocarbon) on the CLTE of PA6 biocomposites was examined and compared to its hybrid additionally containing nanoclay. The results were supported by morphological and thermal characterization showing that the CLTE of the nanobiocomposites were enhanced with the inclusion of a small amount of nanoclay. Accordingly, properties and potential applications of PA6-biocomposites were discussed.
With increasing interest towards biobased and/or biodegradable polymers that generate high performance composites, instead of petroleum based products, creates new opportunities and research challenges. Polylactide (PLA) is supposed to be one of the most promising biodegradable polyesters because of its high mechanical strength, high modulus and good biodegradability. However, the low melt strength of PLA has greatly limited its melt processing such as casting or blowing film, and finally limit its application as packaging. Therefore, firstly the mechanical properties of the PLA were modified by blending with PBS and PBAT; then the melt rheological properties of PLA ternary blends were modified by peroxide in reactive extrusion, and the enhancement effects were evaluated by rheological studies here. Rheological properties revealed that peroxide can greatly enhance the melt strength of PLA ternary blends. A PLA ternary blends/peroxide system can be a good candidate to fabricate biodegradable films with high toughness via stretching shaping process such as casting or blown film.
Hybrid composites are made by incorporating two or more different types of fillers in a single tailorable matrix. This paper investigates a direct injection molding technique applied to hybrid composites made of conventional carbon fiber (CF), glass fiber (GF), and environmentally friendly wood fiber (WF). The favorable combination of these fibers would lead to enhanced mechanical properties and reduced cost. The target markets for the developed hybrid composites could be construction, auto industry, aerospace industry, etc. To meet the strict requirements for these applications, the burning behavior and water absorption behaviors of these hybrid composites were also investigated. Coupling agents (CA), normally used in polymer composites to enhance mechanical properties, were also investigated on their effects on burning and water absorption behaviors.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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