Published by De Gruyter

Volume 36 Issue 5

November 2021

Issue of International Polymer Processing

Contents
Journal Overview

Publicly Available November 16, 2021

Page range: 471-471

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Review article

November 16, 2021

Control Strategies for Reactive Extrusion of Polypropylene by Peroxide Degradation A Brief Review and an Experimental Study

S. Wolf, J. Miethlinger

Page range: 472-498

Abstract

Industry 4.0 and digitalization are widely argued for the future success of numerous industrial solutions. Big data management might lead to the assumption that every issue can be solved numerically without any physical background. To some extent, this strategy will help within the plastics industry in general and in the extrusion technology in particular. However, a deep process knowledge together with process-relevant sensors, as well as the right process arrangements within the processing chain combined with smart data mining methods will be still the key success of industry 4.0. This presentation illustrates, based on a brief review on existing control strategies (Part 1), including sensory and predictive control models for reactive extrusion applied at a real-life on-site best practice project (Part 2), possibilities in combination of process tasks with digitalization approaches for PP-Polymer production. Specifically, rheological research conducted with a novel, patented multi-point rheometer (part 3), will provide a deeper insight into dynamic processes such as reactive extrusion. With those results and derivations thereof, improvements in predictive process control in addition to artificial control systems are made and might even lead to further interesting opportunities.

Regular Contributed Articles

November 16, 2021

Morphology and Tensile Properties as a Function of Welding Current in Thermoplastic Induction Welds

W. P. Ma, H. C. Bu, F. Y. Wang, H. Y. Yang, Y. Xu, X. H. Zhan

Page range: 499-507

Abstract

Compared to other conventional joining methods, induction welding offers the superiority of avoiding mechanical degradation and satisfying the need for weight reduction in the aircraft industry. In this paper, a metal mesh was adapted as an induction component in the induction welding of polyetheretherketone (PEEK) with various currents. The effect of welding current on the microstructure and mechanical properties of the induction welding joint was further investigated. The results indicate that induction welding joints with the narrow thickness of the fusion zone and high tensile strength can be attained in the welding current range of 7.05 A to 11.05 A. However, when the current exceeds 13.91 A, the excessive heat input leads to the unsteady flow of PEEK or even thermal oxidative degradation and thermal decomposition, which increases the thickness of the fusion zone and reduces the tensile strength of the joint. In addition, the principal fracture mode presents cohesive failure, thereby promoting the tensile strength of the joint.

November 16, 2021

Numerical Simulation of Fluid Flow and Mixing Dynamics inside Planetary Roller Extruders

J. Winck, S. Frerich

Page range: 508-518

Abstract

In this contribution, the fluid flow and mixing dynamics inside planetary roller extruders are simulated using the finite element method (FEM) and the mesh superposition technique (MST). Three-dimensional configurations with planetary spindles of varying number and geometry of planetary spindles were created to analyse the influence of the spindle configuration and the rotational speed on the process behavior. Therefore, pressure gradients, flow velocities and directions, shear rates, the mixing index and residence time distributions were evaluated. The distributive and dispersive mixing efficiencies varied depending on the planetary spindle configuration, and these configurations thus suit different processing tasks. In comparison to the standard planetary spindles, the TT3 spindles, with their incomplete toothing, and the knob spindles, with their double transversal helical toothing, showed intense axial and radial mixing. In general, the mixing performance of the planetary roller extruder is explained by a high rate of extensional flow and frequent changes in flow type. The reported numerical approach allows, for the first time, a comprehensive observation of the process behavior of planetary roller extruders.

November 16, 2021

Synergistic Flame-Retardant Effect of Aluminum Diethyl Phosphinate in PP/IFR System and the Flame-Retardant Mechanism

J.-L. Li, C.-T. Gao, X. Sun, S.-G. Peng, Y.-W. Wang, S.-H. Qin

Page range: 519-528

Abstract

Synergistic flame-retardant effect of aluminum diethyl phosphinate (AlPi) in intumescent flame retardant polypropylene (PP/IFR) system and the flame-retardant mechanism were investigated. The flame retardancy of PP/IFR/AlPi (the mass ratio of IFR to AlPi is 2 : 1) was the best, which was proved by the results of the limiting oxygen index (LOI) test, UL-94 test, and cone calorimeter test ( CCT) test. Here, the LOI value of the sample was as high as 34% and passed the V–0 rating in UL–94 test. The peak heat release rate (PHRR) decreased by 92.57%, the total heat release (THR) reduced by 90.52%. Thermogravimetric (TGA) data showed that the introduction of AlPi improved thermal stability and changed the thermal degradation behavior of PP/IFR composites. Interestingly, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS) and laser Raman spectroscopy (LRS) proved that PP/IFR/AlPi had formed more residual carbon, but the flame retardancy was worse than PP/IFR/AlPi. This is because when the mass ratio of IFR to AlPi is 2 : 1, the synergy between IFR and AlPi was significant, gas-phase flame retardant and condensed-phase flame retardant reached a balance and obtained the best flame retardant effect.

November 16, 2021

Predicting the Non-Linear Conveying Behavior in Single-Screw Extrusion: A Comparison of Various Data-Based Modeling Approaches used with CFD Simulations

W. Roland, C. Marschik, M. Kommenda, A. Haghofer, S. Dorl, S. Winkler

Page range: 529-544

Abstract

The traditional approach to modeling the polymer melt flow in single-screw extruders is based on analytical and numerical analyses. Due to increasing computational power, data-driven modeling has grown significantly in popularity in recent years. In this study, we compared and evaluated databased modeling approaches (i. e., gradient-boosted trees, artificial neural networks, and symbolic regression models based on genetic programming) in terms of their ability to predict – within a hybrid modeling framework – the three-dimensional non-linear throughput-pressure relationship of metering channels in single-screw extruders. By applying the theory of similarity to the governing flow equations, we identified the characteristic dimensionless influencing parameters, which we then varied to create a large dataset covering a wide range of possible applications. For each single design point we conducted numerical simulations and obtained the dimensionless flow rate. The large dataset was divided into three independent sets for training, interpolation, and extrapolation, the first being used to generate and the remaining two to evaluate the models. Further, we added two features derived from expert knowledge to the models and analyzed their influence on predictive power. In addition to prediction accuracy and interpolation and extrapolation capabilities, we evaluated model complexity, interpretability, and time required to learn the models. This study provides a rigorous analysis of various data-based modeling approaches applied to simulation data in extrusion.

November 16, 2021

Influence of Crystal Structure on Thermo-Mechanical Properties of Injection Molded 𝛃-Nucleated iPP

A. Hamza, R. K. Arya, A. D. Palsodkar, G. R. Bhadu, S. J. A. Rizvi

Page range: 545-556

Abstract

Isotactic polypropylene (iPP) was nucleated in-situ with calcium pimelate during melt compounding. Calcium pimelate is a highly effective β-nucleator for isotactic polypropylene (iPP). The β-nucleated iPP was characterized by wide angle x-ray diffraction (WAXD) and differential scanning calorimetry (DSC) for its crystallinity and crystal structure. In addition, the injection-molded samples were tested for thermo-mechanical properties. It is found that very low quantity (< 0.1 wt. %) of β-nucleator is required to produce sufficiently high β-crystal fraction (K β ) in isotactic polypropylene. β-nucleated iPP shows increment of 11 to 14 °C in its heat deflection temperature (HDT). It was also observed that slow cooling rate of β-nucleated iPP promotes the formation of β-crystals and that tensile stretching leads to complete transformation of β crystals into a-crystals at room temperature. It was also revealed that the presence of maleic anhydride grafted polypropylene (PP-g-MA), a well-known coupling agent (or compatibilizer), may reduce the (K β ) value to a marginal extent. It was also observed that the thermo-mechanical properties were not much affected by the presence of PP-g-MA. Therefore, calcium pimelate may be used as β-nucleator in case of neat as well as reinforced polypropylene containing maleic anhydride as coupling agent.

November 16, 2021

An Experimental Study on the Properties of Recycled High-Density Polyethylene

A. G. Toroslu

Page range: 557-563

Abstract

Recycling of plastic materials has become more environmentally important than recycling of other materials. The most important problem during recycling is the presence of oil, dirt, dust and metal particles that are mixed with plastic materials. These mixtures can change their its mechanical and physical properties and it is quite costly to remove them completely. Removing iron alloy particles from plastic is possible by using the magnetic method. However, removing non-metallic materials requires extra processing. In this study, the use of recycled High-Density Polyethylene (rHDPE) without an expensive cleaning processes has been investigated. Different amounts of aluminium oxide (Al 2 O 3 ) were added to High Density Polyethylene (HDPE) to simulate the effect of non-metallic material involved. The effect of these contamination rates on the mechanical and physical properties of HDPE was examined in detail. For this purpose, recyclable materials were produced by mixing rHDPE with 1%, to 7% Al 2 O 3 . The results show that up to 7% of the mixture has acceptable effects on the properties of HDPE. When the results of the experiments are examined, it is observed that there is a 3.74% change in the elastic modulus of the material. This means, that up to 7% non-metal contaminated rHDPE material can be used without any costly recycling process .

November 16, 2021

Improvement of Mechanical and Biological Properties of PLA/HNT Scaffolds Fabricated by Foam Injection Molding: Skin Layer Effect and Laser Texturing

M. Eryildiz, M. Altan, S. Odabas

Page range: 564-576

Abstract

Polylactic acid (PLA) is one of the important materials for orthopedic regenerative engineering applications due to its biodegradability and biocompatibility. Nonetheless, PLA may show insufficient mechanical strength for some bone replacement applications. Halloysite nanotube (HNT) is one of the non-toxic, biocompatible reinforcement for improving mechanical and biological properties of PLA for tissue engineering applications. In this study, PLA/HNT scaffolds were prepared by chemical foam injection molding process. Laser surface texturing was applied on the skin layer of the injection molded scaffolds to enhance the cell viability and hydrophilicity of PLA. The effects of HNT concentration on cell morphology, mechanical and thermal properties, cell viability and biodegradation profile of the scaffolds were studied. The results demonstrated that cell viability increased by 43% in PLA/HNT scaffolds compared to neat PLA. Hydrophilicity of the scaffolds that have thick skin layer was enhanced by the laser surface texturing in two different designs and consequently, cell viability increased about 16%. Surface roughness measurements and water contact angle measurements have verified this result.

November 16, 2021

Relationship between Molecular Orientation Relaxation during Physical Aging and Heat Resistance of Polystyrene Injection Moldings

K. Tao, K. Yamada, S. Higashi, K. Kago, H. Takeshita, K. Tokumitsu

Page range: 577-585

Abstract

This work examined the relationship between changes in molecular orientation and the heat resistance (heat distortion temperature) of polystyrene injection moldings following heat treatment below the glass transition temperature. Molecular orientation around the core layer of the injection moldings was found to be relaxed by the heat treatment. Also, in the untreated specimen, the molecular orientation around the core layer was relaxed from 60°C during the heating process. Since loss tangent (tanδ) also increased from 60°C during the heating process in the untreated specimen, it was considered that the increase in tanδ occurred with the molecular motion due to the relaxation of molecular orientation from 60°C. After the heat treatment, because of the relaxation of molecular orientation around the core layer by the heat treatment, the relaxation of molecular orientation from 60 °C did not occur during the subsequent heating process, and the tanδ of the polymer between 60 and 90 °C was decreased. Because this decrease in the tanδ over this temperature range improved the heat resistance of the material, the enhanced heat resistance by the heat treatment was attributed to the suppression of the relaxation of molecular orientation from 60°C during the heating process. Furthermore, relaxation of molecular orientation and enthalpy relaxation were related to improvement in the heat resistance.

November 16, 2021

Recycling of Bagasse as an Agricultural Waste and its Effect as Filler on Some Mechanical and Physical Properties of SBR Composites

E. S. A. Khalaf

Page range: 586-595

Abstract

In the present study, a series of mixes based on different concentrations of carbon black (CB) as a reinforcing filler and sugarcane bagasse as supplementary filler, were investigated to examine their effects on the mechanical properties of styrene butadiene rubber (SBR) composites. To this end, the first group of mixes deals with the effect of different concentrations of CB ranging from 0 to 80 phr at fixed bagasse concentration of 25 phr. The second group of mixes involves the addition of bagasse with concentrations varying from 10 to 50 phr at 10 intervals with fixed CB concentration of 40 phr. The sizes of the employed ground bagasse powder (GBP) in all prepared formulations ranged from 20 to 180 μm. In addition, 2.5 phr of maleic anhydride (MA) was added to enhance the interfacial adhesion between SBR and agricultural waste fillers (i. e. bagasse). Tensile strength, elongation at break, modulus at 100% elongation, resilience, hardness (Shore A), abrasion and degree of swelling of the rubber vulcanizates were studied. The prepared samples were also analyzed by scanning electron microscopy (SEM) to show the distribution of fiber and the occurrence of fiber-matrix adhesion. The optimum concentration of bagasse to be used simultaneously with CB in SBR composites was found to be 30 phr. Overall, it was found from the obtained results that the addition of GBP up to 50 phr is feasible without impairing the mechanical properties of SBR vulcanizates.

November 16, 2021

Use of Image Analysis for Non-Destructive Testing of Thermoformed Food Packages

O. Ekşi

Page range: 596-607

Abstract

The aim of this study is to determine the thickness distribution of a food package using a non-destructive method. Initially, thickness measurements were carried out using an experimental procedure for thermoformed samples that were used for food packaging. Additionally, in this study, image analysis was used for the first time to determine the thickness distribution of the thermoformed products non-destructively. Image analysis software was employed for the estimation of thickness distribution. Measured thickness results were compared to those estimated using image analysis. Based on the results of the current study, image analysis may be an alternative method for non-destructive testing of thermoformed food packages even in a mass production line. Image analysis can be used to determine not only thickness distribution but also the weakest regions in a food package.

November 16, 2021

Process Influences in the Combined Compacting and Back-Injection Process to Produce Back-Injected Self-Reinforced Composites (SRCs) – Analysis via Multiple Regression Modelling

F. Jakob, J. Pollmeier, H.-P. Heim

Page range: 608-619

Abstract

A new process to produce back-injected self-reinforced composites (SRCs) is presented. In contrast to other investigations on back-injection of SRCs, a process is presented which allows compacting and back injection of SRCs in one step where the SRCs are partly consolidated only via melt pressure inside the cavity. The mechanical properties of SRCs depend to a large extent on the process parameters of temperature and pressure during manufacture. These parameters are not yet known for back-injected areas. Sensors inside of the cavity measure the influences on the temperature and pressure conditions in the cavity. Initial studies on adhesion were carried out and analysed. For this purpose, shear tests of the back-injected component were carried out and a maximum shear strength of 5.81 MPa was determined for the materials used here. The investigations also show a dependence on the Distance from the Gate (D G ) and the Mass temperature (T M ). First microscopic examinations show good bonding between the SRC and the injection molded part, with no voids or air pockets in the boundary layer. It can also be seen that successful consolidation takes place in the area of the back injection.

November 16, 2021

Utilizing Pyrolytic Biomass Products for Rubber Reinforcement: Effect of the Silica Content in Biomass Feed Stocks

L.-Y. Yu, B.-C. Xue, M.-M. Qian, Y.-X. Li, Z.-X. Chen, Y.-C. Zhu, X.-F. Wang

Page range: 620-629

Abstract

Biochar has been exploited as a substitution of carbon black in the rubber industry and various biochars exhibit diverse reinforcing abilities due to the different compositions. This work aims at studying the effect of silica on the modification process and reinforcing performance through the comparison of three biochars with different contents of silica, pyrolytic rice husks (PRH, 34 wt%), pyrolytic bamboos (PB, 7 wt%) and pyrolytic corn cobs (PC, 0.4 wt%). The results reveal that PRH requires higher rotational speed (300 min –1 ) than PB (200 min –1 ) and PC (200 min –1 ) to achieve similar particle sizes during the ball milling process because of the aggregations of higher silica content. Meanwhile, silica-rich pyrolytic biomass exhibits enhanced reinforcement on mechanical properties and thermal stability of rubber, and the elongation at break of vulcanizates continues to improve with increasing silica contents. Combined with the energy consumption and reinforcement, biochar containing a little amount of silica is more suitable to be widely used as bio-filler in rubber industry. This work should serve as a valuable reference to select appropriate biochar for the production of bio-fillers with high reinforcement.

November 16, 2021

PPS News

Page range: 632-632

November 16, 2021

Seikei-Kakou abstracts

Page range: 633-633

November 16, 2021

PPS Membership application

Page range: 634-634

About this journal

International Polymer Processing offers original research contributions, invited review papers and recent technological developments in processing thermoplastics, thermosets, elastomers and fibers as well as polymer reaction engineering. For more than 25 years International Polymer Processing, the journal of the Polymer Processing Society, provides strictly peer-reviewed, high-quality articles and rapid communications from the leading experts around the world.
All articles are subject to thorough, independent peer review.
Editor: Polymer Processing Society

Volume 36 Issue 5

Issue of International Polymer Processing

Contents

Control Strategies for Reactive Extrusion of Polypropylene by Peroxide Degradation A Brief Review and an Experimental Study

Abstract

Morphology and Tensile Properties as a Function of Welding Current in Thermoplastic Induction Welds

Abstract

Numerical Simulation of Fluid Flow and Mixing Dynamics inside Planetary Roller Extruders

Abstract

Synergistic Flame-Retardant Effect of Aluminum Diethyl Phosphinate in PP/IFR System and the Flame-Retardant Mechanism

Abstract

Predicting the Non-Linear Conveying Behavior in Single-Screw Extrusion: A Comparison of Various Data-Based Modeling Approaches used with CFD Simulations

Abstract

Influence of Crystal Structure on Thermo-Mechanical Properties of Injection Molded 𝛃-Nucleated iPP

Abstract

An Experimental Study on the Properties of Recycled High-Density Polyethylene

Abstract

Improvement of Mechanical and Biological Properties of PLA/HNT Scaffolds Fabricated by Foam Injection Molding: Skin Layer Effect and Laser Texturing

Abstract

Relationship between Molecular Orientation Relaxation during Physical Aging and Heat Resistance of Polystyrene Injection Moldings

Abstract

Recycling of Bagasse as an Agricultural Waste and its Effect as Filler on Some Mechanical and Physical Properties of SBR Composites

Abstract

Use of Image Analysis for Non-Destructive Testing of Thermoformed Food Packages

Abstract

Process Influences in the Combined Compacting and Back-Injection Process to Produce Back-Injected Self-Reinforced Composites (SRCs) – Analysis via Multiple Regression Modelling

Abstract

Utilizing Pyrolytic Biomass Products for Rubber Reinforcement: Effect of the Silica Content in Biomass Feed Stocks

Abstract

PPS News

Seikei-Kakou abstracts

PPS Membership application