Thermoplastic Polymer Materials Research Articles

Effect of pressurized CO2 and N2 on the rheology of PLA

Melt-polymer processing is conventionally employed for thermoplastic polymeric materials. The rheological behaviour of the polymer is then of critical importance to correctly accomplish the process. The effect of pressurized fluid additives (PFA), such as CO2 and N2, has been investigated in this work to determine the extension of their beneficial plasticization effect on PLA. In-line measurements performed by a custom-designed slit-die rheometer were conducted at different temperatures and PFA concentrations, and the viscosity values of PLA/PFA mixtures were experimentally determined and compared to those obtained when adding a commercial plasticizer, acetyltributylcitrate (ATBC), to PLA. Our results suggested that a twofold reduction of PLA viscosity is achievable using addition of 2.65 wt% pressurized CO2 respect to similar contents of ATBC. Furthermore, a decrease of 10 °C of the processing temperature could be attained when adding 1.70 wt% of CO2. This work aims at shedding light on the rheological behaviour that PLA experiences during assisted-melt extrusion processing, and on how more favourable energetic processing could be achieved by lowering temperature, if the appropriate type and concentration of PFA is employed during processing.

Polymer Photochromic Composites and Their Spectral and Kinetic Properties

A method for the synthesis of polymer photochromic composites containing photochromic nitro-substituted spiropyran via mechanical mixing in melt is developed, and dependences of the spectral and kinetic properties of the samples on the nature of chosen thermoplastic polymer matrices (polyolefins, polycarbonate) and their processing temperatures are studied.

Multi-component Polymer Systems Comprising Wood as Bio-based Component and Thermoplastic Polymer Matrices – An Overview

The production of wood-based polymer composites has gained increasing interest in recent years, especially regarding sustainability issues, aiming at the recovery, reuse, and up-cycling of by-products from natural resources exploitation, as well as plastics. Due to their reduced cost, low density, and availability, wood components (fibers, flour) are attractive fillers for thermoplastic polymer matrices used in multi-component systems. Performance of wood-based thermoplastic materials mainly depends on the type and strength of interactions at the polymer-wood interface. Different low polarity polymers (high/low density polyethylene, polypropylene, polyvinylchloride) can be successfully used as matrices in such formulations. Various methods may be applied in order to obtain specified performance attributes of wood-based composites. Addition of appropriate compatibilizing agents, chemical and/or physical modification of the filler in order to improve its compatibility towards the matrix, or a judicious combination of these approaches may be employed. This paper briefly reviews some recent literature data, as well as research results by the authors, aiming at a comparative assessment of the materials properties (structure, thermal, mechanical and water sorption behavior) in correlation with the nature and type of components, processing, recycling options, and environmental impact.

3D-Printable ABS Blends with Improved Scratch Resistance and Balanced Mechanical Performance

Acrylonitrile–butadiene–styrene (ABS) is one of the most important materials utilized by fused deposition modeling (FDM) 3D printing. In this work, we prepared a series of 3D-printable ABS-based materials with improved scratch resistance and balanced mechanical performance via a simple blending strategy. The scratch resistant performance, mechanical strength, melt flow rate, hardness, transmittance, and surface gloss of ABS were improved simultaneously by adding 30 mass portion of poly(methyl methacrylate) (PMMA). Further addition of a small amount of methacrylate–butadiene–styrene (MBS), a kind of core–shell rubber modifier with high toughening efficiency, improved the toughness of ABS/PMMA effectively and hardly influenced the scratch resistance and optical properties of ABS/PMMA. This ABS/PMMA/MBS blend has the potential for large-scaled fabrication and can be developed as a new category of thermoplastic polymer material specially used for FDM 3D printing.

Simulation and Research of the Nozzle with an Ultrasonic Resonator for Spraying Polymeric Materials

In this paper, a method for the aerosol application of polymers to fabric surfaces is discussed. A lot of thermoplastic polymer materials during application have the property of hardening and the formation of glue lumps. This leads to a decrease in the quality of the coating applied. In view of the fact that aerosol coating is undoubtedly advantageous, it required improvement. Modeling of polymer flow through the nozzle was perform to determine the optimal application distance. The experimental part consisted of applying a solution of a polyvinyl chloride polymer to a fabric using an ultrasonic radiator on a diffuser. Just for comparison, samples without the connection of the radiator were perform. Politec 3D scanner equipment used to determine deformation changes. This study has a weight for the further development and improvement of coating devices.DOI: http://dx.doi.org/10.5755/j01.mech.24.1.20215

Dynamic performance of an amorphous polymer composite under controlled loading of reduced graphene oxide based on entanglement of filler with polymer chains

This work recommends an optimum content of rGO required for effective improvement in thermomechanical properties of rGO/ABS composites. According to electrical conductivity measurements, the percolation threshold of rGO in ABS should be around 1 wt% but mechanical and rheological properties keep on increasing beyond this value. However, on the basis of tensile and damping properties, 1.5 wt% is the optimum content of rGO that should be used as reinforcement in thermoplastic polymer matrices. Composites having 1.5 wt% rGO in ABS have shown significant improvement in tensile strength, excellent degree of entanglement (specially at higher temperatures) and a very low value for C-factor. As observed in FESEM micrographs, the deterioration of properties with further increase in rGO content (2 wt% and above) should be due to non-uniform dispersion of filler inside the matrix. Moreover, the elliptical shape of Cole-Cole plots validates the compatibility of rGO as reinforcing filler in ABS matrix.

Технология производства зубчатых колес из термопластичных полимерных материалов (обзор)

Технология производства зубчатых колес из термопластичных полимерных материалов (обзор)

Utilization of Recycled Polymer Matrices For Production of Eco-Composites

One of the big new areas of development of the advanced composite materials is in combining natural fibers with thermoplastics for producing lightweight, environmentally friendly, cost-effective composite material.The aim of this work is to show the possibilities of recycling and reuse of thermoplastic polymer matrices with rice hulls (RH) and kenaf fibres (KF) using the conventional techniques, extrusion and compression moulding. The matrices (polypropylene (PP) and poly(lactic) acid (PLA) ) were recycled one and two times and the fibers/filler were compounded with recycled matrix. The processing and material properties have been studied on the composites with recycled matrix and compared to the composites with virgin matrix.Characterization of all composites includes mechanical, morphological and thermo-gravimetrical analysis. Тhe flexural properties for PP recycled based composites were held close to the flexural properties for composite based on neat PP, but for PLA recycled based composite the flexural properties are decreased for about 50%. The thermal stability of recycled matrices based composites is very similar to the thermal stability of the composites with virgin matrix. SEM analysis has shown that the fillers/fibers are covered by the recycled polymer matrix, indicated on the satisfied durability of the recycled polymer matrices. The obtained results have shown that both polymer matrices (biodegradable and no degradable) could be recycled with acceptable mechanical properties and they can be successfully used for production of eco-composites.

Localized Laser Sintering of Metal Nanoparticle Inks Printed with Aerosol Jet® Technology for Flexible Electronics

Direct-write methods, such as the Aerosol Jet® technology, have enabled fabrication of flexible multifunctional 3-D devices by printing electronic circuits on thermoplastic and thermoset polymer materials. Conductive traces printed by additive manufacturing typically start in the form of liquid metal nanoparticle inks. To produce functional circuits, the printed metal nanoparticle ink material must be postprocessed to form conductive metal by sintering at elevated temperature. Metal nanoparticles are widely used in conductive inks because they can be sintered at relatively low temperatures compared with the melting temperature of bulk metal. This is desirable for fabricating circuits on low-cost plastic substrates. To minimize thermal damage to the plastics, while effectively sintering the metal nanoparticle inks, we describe a laser sintering process that generates a localized heat-affected zone (HAZ) when scanning over a printed feature. For sintering metal nanoparticles that are reactive to oxygen, an inert or reducing gas shroud is applied around the laser spot to shield the HAZ from ambient oxygen. With the shroud gas-shielded laser, oxygen-sensitive nanoparticles, such as those made of copper and nickel, can be successfully sintered in open air. With very short heating time and small HAZ, the localized peak sintering temperature can be substantially higher than that of damage threshold for the underlying substrate, for effective metallization of nanoparticle inks. Here, we demonstrate capabilities for producing conductive tracks of silver, copper, and copper–nickel alloys on flexible films as well as fabricating functional thermocouples and strain gauge sensors, with printed metal nanoparticle inks sintered by shroud-gas-shielded laser.

Experimental Measurement of Low-Intensity and Long-Duration Internal Charging Behavior

We report initial results from the EU FP7 Spacestorm project on the experimental behavior of commonly-used space dielectric materials in an electron environment where the incident electron current is significantly below safe levels specified by design standards. The realistic electron environment facility (REEF), which uses an intense strontium-90 beta-emitting radioactive source to simulate the space environment, has been recommissioned at the University of Surrey for this purpose. Using a combination of shielding and variable source-sample separation REEF can achieve a very wide dynamic range in electron current, from the very high levels associated with an extreme space weather event, down to the levels below the European Cooperation for Space Standardization low temperature (<25 °C) safety threshold of 0.02 pA/cm2. In order to allow for the accumulation of significant levels of charge at such a low current, these experiments need to be run continuously for several weeks, far in excess of typical experimental investigations of internal charging phenomena. Here we report our early results from these experiments on samples of polyether ether ketone thermoplastic polymer material. Irradiating using a range of electron currents provides insight into the effect not just of inherent material properties but also of secondary effects such as radiation-induced conductivity.

The Design of Composite Materials of Prescribed Structure and Properties

The structure and properties of a composite material (basalt-fibre-reinforced plastic) reinforced by chaotically distributed discrete fibres were determined at the design stage with account taken of the fibre diameter, the critical length of the fibres, the arrangement of fibres within the matrix, and the stress distribution over the length of the fibres. The results of calculation were used in the manufacture of specimens of thermoplastic polymeric material by the developed technology. The given results of experimental investigation of specimens of the thermoplastic material showed that the calculated values of the properties of the composite differ little from experimental values.

On the Plastic Constraint Factor of Polymers

SummaryThe plastic constraint factor based on Hill's theory of plasticity is widely used to check the stress state applying the essential‐work‐of‐fracture (EWF) approach to polymers. However, the plastic constraint factor experimentally determined as the ratio of the net section stress in cracked specimens and the yield stress does not match the theoretical predictions of the theory of plasticity because assuming ideal‐plastic behaviour for polymer materials does not consider material‐specific viscoelastic–viscoplastic effects adequately. Therefore, a correction term for amorphous thermoplastic polymer materials is derived introducing the influence of the material on the plastic constraint factor. This correction term is based on the Williams‐Landel‐Ferry (WLF) equation for different thermodynamic quantities such as temperature and stress (negative pressure) and the introduction of a glass stress to be comparable to the glass temperature. Analytical calculation of this correction term, taking polycarbonate as an example, is used as a comparison to empirical values in literature for numerous amorphous and semi‐crystalline thermoplastic as well as partial‐plastically deformable elastomeric polymer materials. It can be concluded that this enhanced Hill's theory is well suited to amorphous polymers.

Nuclear characteristics of epoxy resin as a space environment neutron shielding

Abstract In recent years many investigations have been done for choosing applicable light neutron shielding in space environmental applications. In this study, we have considered the neutron radiation-protective characteristics of neat epoxy resin, a thermoplastic polymer material and have compared it with various candidate materials in neutron radiation protection such as Al 6061 alloy and Polyethylene. The aim of this investigation is the effect of type of moderator for fast neutron, notwithstanding neutron absorbers fillers. The nuclear interactions and the effective dose at shields have been studied with the Monte Carlo N-Particle transport code (MCNP), using variance reductions to reduce the relative error. Among the candidates, polymer matrix showed a better performance in attenuating fast neutrons and caused a lower neutron and secondary photon effective dose.

Rate limits of additive manufacturing by fused filament fabrication and guidelines for high-throughput system design

As additive manufacturing (AM) advances rapidly towards new materials and applications, it is vital to understand the performance limits of AM technologies and to overcome these limits via improved machine design and process integration. Extrusion-based AM (i.e., fused filament fabrication, FFF) is compatible with a wide variety of thermoplastic polymer and composite materials, and can be deployed across a wide range of length scales. However, the build rate of both desktop and professional FFF systems is comparable (∼10’s of cm3/h at ∼0.2mm layer thickness), suggesting that fundamental aspects of the machine design and process physics limit system performance. We determine the rate limits to FFF by analysis of machine modules: the filament extrusion mechanism, the heater and nozzle, and the motion system. We determine, by direct measurements and numerical analysis, that FFF build rate is influenced by the coincident module-level limits to traction force exerted on the filament, conduction heat transfer to the filament core, and gantry velocity for positioning the printhead. Our findings are validated by direct measurements of build rate versus part complexity using desktop FFF systems. Last, we study the scaling of the rate limits using finite element simulations of thermoplastic flow through the extruder. We map the scaling of extrusion force, polymer exit temperature, and average printhead velocity onto a unifying trade-space of build rate versus resolution. This approach validates the build rate performance of current FFF systems, and suggests that significant enhancements in FFF build rate with targeted quality specifications are possible via mutual improvements to the extrusion and heating mechanism along with high-speed motion systems.

Developing Customized Dental Miniscrew Surgical Template from Thermoplastic Polymer Material Using Image Superimposition, CAD System, and 3D Printing.

This study integrates cone-beam computed tomography (CBCT)/laser scan image superposition, computer-aided design (CAD), and 3D printing (3DP) to develop a technology for producing customized dental (orthodontic) miniscrew surgical templates using polymer material. Maxillary bone solid models with the bone and teeth reconstructed using CBCT images and teeth and mucosa outer profile acquired using laser scanning were superimposed to allow miniscrew visual insertion planning and permit surgical template fabrication. The customized surgical template CAD model was fabricated offset based on the teeth/mucosa/bracket contour profiles in the superimposition model and exported to duplicate the plastic template using the 3DP technique and polymer material. An anterior retraction and intrusion clinical test for the maxillary canines/incisors showed that two miniscrews were placed safely and did not produce inflammation or other discomfort symptoms one week after surgery. The fitness between the mucosa and template indicated that the average gap sizes were found smaller than 0.5 mm and confirmed that the surgical template presented good holding power and well-fitting adaption. This study addressed integrating CBCT and laser scan image superposition; CAD and 3DP techniques can be applied to fabricate an accurate customized surgical template for dental orthodontic miniscrews.

Comparative study of different alloys during thermal debind-ing of powder injection molded parts

Powder injection molding (PIM) is an interesting technique and address of research, in which a thermoplastic polymeric material is used to form the powder into the desired shape in a closed die. Binders have a crucial importance in the powder metallurgy technology as they play a vital role to provide efficient powder agglomeration and/or lubrication during shaping. At the same time, they have to be easily removed from the compacts during initial stages of sintering, using debinding process, without any damaging effect for the base material. Thermal debinding is a vital process requiring somewhat elevated temperatures to remove binder from the compact. In the current study, an investigation has been made about the effect of process variables on the debinding of injection molded pieces, by melt wicking. The debinding process was performed at temperatures ranging from 160- up to-200°C for a time duration varying from 1-up to-27 hours. All powders used in injection molding feedstock have an inherent packing porosity. Several types of alloy powders (Carbonyl iron steel, Nickel aluminide, and 316L stainless powders), with various size distributions, particle shapes, and materials are adopted to define the influence on binder incorporation resulted from this inherent porosity. Results revealed that the increase of debinding time or decrease in the wicking powder (alumina) particle size lead to an increase in the thickness of the adhered layer of alumina. When the wicking powder is very fine (0.3 mm) or has a wide particle size range (&lt;10 mm), it becomes more dense and its debinding efficiency is decreased. At high debinding temperatures (200 °C) the rate of binder evaporation and removal increased, which leads to decreasing the cohesion of the samples yielding a shape distortion. In addition, the effect of the wicking powder (Al2O3) sizes and debinding time on the binder weight loss percentage after debinding process for FeOX, Ni3Al, and 316L has been investigated.

Technology of thermoplastic polymeric composite materials for the bottom of shoes

Technology of thermoplastic polymeric composite materials for the bottom of shoes

Hybridization of graphene-reinforced two polymer nanocomposites

ABSTRACTThis article focuses on the hybridization of thermoplastic polymer matrices with conducting polymers and graphene derivatives. Polypropylene (PP), polymethylmethacrylate (PMMA) and polyoxymethylene (POM) were used as primary polymer matrices and polypyrrole (PPY) and polyaniline (PANI) as secondary conducting polymers. Highly conductive-reduced graphene oxide (rGO) and graphene (G) have been used as reinforcements. A Taguchi analysis has been performed for the blends to find the optimal combination of the blends with respect to electrical conductivity (σ) and mechanical properties. Both electrical and mechanical properties were improved by the hybridization process. The maximum electrical conductivity of 0.85 S.cm−1 has been acquired with POM/PPY/G blend with 3 wt.% and 5 wt.% of PPY and graphene loading, respectively. The mechanical properties have been found to improve with all the blends but, PP/PPY/G blend with 3 wt.% and 6 wt.% of PPY and graphene loading displays overall better properties in comparison with other blends.

Polymer Composites Filled with Multiwall Carbon Nanotubes

The structural and physico-chemical characteristics of thermoplastic polymers filled with multiwall carbon nanotubes (CNTs) such as polyethylene (PE), polyamide 6 (PA 6) and layered fiberglass with PA 6 are investigated. The influence of their concentrations and homogeneity degree of nanotubes distribution is studied. The properties of new composites are compared with the well investigated polytetrafluoroethylene (PTFE)-CNTs and polypropylene (PP)-CNTs systems. It is shown that an addition of CNTs into thermoplastic polymeric materials leads to the significant changes in structural characteristics, growth of strength, electrical, thermal properties. It is coursed by the formation of CNTs continuous network in the original matrix, the crystallinity degree of the matrix depending on the concentration of CNTs. In turn, the crystallinity degree of the matrix is increased by homogeneity arising of the composite as a result of the strong interaction of the matrix with nanofiller. The changes of not only bulk but also the surface properties of the composites are observed, which explains the best biocompatibility of the nanocomposites observed in natural conditions experiments (in vivo).

Synthesis and characterization of a magnetic bio-nanocomposite based on magnetic nanoparticles modified by acrylated fatty acids derived from castor oil

The present work addresses the synthesis and characterization of a new bio-nanocomposite based on acrylated fatty acids (AFA) derived from castor oil, ethyl acrylate and AFA surface modified γ-Fe2O3 (γ-Fe2O3@AFA) magnetic nanoparticles (MNPs). It was shown that the in situ formed bio-nanocomposite containing around 2.0wt.% of γ-Fe2O3 MNPs with average particle size of ca. 9.0nm, as determined by XRD and TEM measurements, displayed good magnetic response and superparamagnetic behavior. The magnetization measurements indicated that the incorporation of γ-Fe2O3@AFA MNPs into the poly(ethyl acrylate-co-AFA) matrix did not affect the magnetization saturation, remanence and coercivity of the MNPs, preserving the magnetic properties of the γ-Fe2O3 precursor. Additionally, the use of AFA to chemically modify the surface of MNPs opens a new scenario on the chemical modification of MNPs with agents that undergo free-radical reactions, allowing for the proper dispersion of MNPs into the thermoplastic polymer matrices and minimizes the undesired leaching of the MNPs.