Showing papers on "Thermoplastic published in 2020"

Fragmentation of plastic objects in a laboratory seawater microcosm.

Abstract: We studied the fragmentation of conventional thermoplastic and compostable plastic items in a laboratory seawater microcosm In the microcosm, polyurethane foams, cellulose acetate cigarette filters, and compostable polyester and polylactic acid items readily sank, whereas polyethylene air pouches, latex balloons, polystyrene foams and polypropylene cups remained afloat Microbial biofilms dominated by Cyanobacteria, Proteobacteria, Planctomycetes and Bacteriodetes grew on the plastics, and caused some of the polyethylene items to sink to the bottom Electrical resistances (ER) of plastic items decreased as function of time, an indication that seawater had penetrated into microscopic crevices in the plastic that had developed over time Rate constants for ER decrease in polyethylene items in the microcosm were similar to tensile elongation decrease of polyethylene sheets floating in sea, measured previously by others Weight loss of plastic items was ≤ 1% per year for polyethylene, polystyrene and polypropylene, 3–5% for latex, polyethylene terephthalate and polyurethane, 15% for cellulose acetate, and 7–27% for polyester and polylactic acid compostable bags The formation of microplastics observed in the microcosm was responsible for at least part of the weight loss This study emphasizes the need to obtain experimental data on plastic litter degradation under conditions that are realistic for marine environments

3D compaction printing of a continuous carbon fiber reinforced thermoplastic

Abstract: This study reports a three-dimensional compaction printing (3DCP) technique for a continuous carbon fiber reinforced thermoplastic (CFRTP). A hot-compaction roller was equipped with a fused filament fabrication (FFF)-based 3D printer to press the filament against the printer bed immediately after the printing to reduce voids and improve adhesion between the filaments. Unidirectional CFRTP coupon specimens were fabricated and the tensile and bending properties of the specimens were investigated. The test results showed that the tensile and bending properties of the printed CFRTP were improved by the hot compaction during 3D printing. Voids in the specimen were visualized using scanning electron microscopy and X-ray computed tomography, and it was confirmed that the hot compaction reduced the void content. The experimental results showed that 3DCP was superior to conventional FFF in the fabrication of CFRTP parts for structural applications.

A review of Long fibre thermoplastic (LFT) composites

Abstract: Long fibre-reinforced thermoplastic or long fibre thermoplastic (LFT) composites possess superior specific modulus and strength, excellent impact resistance, and other advantages such as ease of pr...

Scalable upcycling of thermoplastic polyolefins into vitrimers through transesterification

Abstract: About 150 million tons of disposed plastic is accumulated each year globally. A massive challenge will be addressed even if a fraction of this amount is reclaimed as relevant feedstock for innovative materials, provided this transformation is accomplished through an affordable process with minimal resources in a high-throughput manner. Vitrimers, the dynamic networks enabled by an associative covalent bond exchange, are an emerging class of materials that combine the best of thermoplastic and thermoset characteristics. Here we report that high performance vitrimers can be produced through chemical transformation of commodity thermoplastic polyolefins (TPOs) in a simple and economical way. Polypropylene (PP) and polyethylene (PE) retrieved from recycling have been converted into permanently crosslinked networks that are rubber-elastic above the melting point, and are capable of bond exchange at a further elevated temperature. We find that the dynamically crosslinked network shows thermally triggered shape-memory behaviour with 90% recovery after multiple fixity–recovery cycles. With superior mechanical stability compared to the precursor TPO, dynamic networks can establish interfacial covalent bonding to assemble objects of complex shapes through welding. The developed method can be applied to a wide range of TPOs without prior knowledge of their precise composition. It suggests a new direction towards recovery of ‘smart’ materials for sustainable and affordable technologies from plastic recycling, using conventionally operated instruments, without the need to upgrade the infrastructure of the polymer processing industry.

Low-energy impact response of composite sandwich panels with thermoplastic honeycomb and reentrant cores

Abstract: In the present study, the low-energy impact response of woven carbon fibre reinforced plastic (CFRP) composite sandwich panels with thermoplastic honeycomb and reentrant cores was investigated experimentally and numerically under three different impact energies (20 J, 40 J and 70 J). The Acrylonitrile Butadiene Styrene (ABS) honeycomb and reentrant core structures were manufactured in-plane and out-of-plane oriented via 3D printer, and adhesively bonded with two CFRP face sheets. The results indicate that the in-plane reentrant core based composite sandwich panel exhibits better impact strength and energy dissipation behavior than the in-plane and out-of-plane honeycomb core based composite sandwich panels.

Flexible, Reconfigurable, and Self-Healing TPU/Vitrimer Polymer Blend with Copolymerization Triggered by Bond Exchange Reaction.

Abstract: In recent decades, flexible, reconfigurable, and fast-response self-healing polymers have attracted considerable attention for both industrial field and scientific research. Mechanical blending remains the most mature, economical, effective, and the simplest approach to produce polymer blends, which can combine several distinctive advantages from different thermoplastic materials. However, such a process cannot be simply applied to thermosetting materials due to their permanent molecular structures. The synthesis of high-performance polymer blends connected by covalent cross-links remains a big challenge for the present industrial system. In this paper, we proposed a novel approach to synthesize polymer blends via blending thermosetting vitrimer containing dynamic covalent networks with thermoplastic polymers. It is demonstrated that the intrinsic relationship could be established by controlling the bond exchange reactions between the thermoset and the thermoplastic, thus triggering copolymerization. Due to the highly controlled processing conditions, the synthesized polymer is highly flexible, recyclable, and reprocessable, and possesses self-healing behavior at the same time. In addition, it shows potential applications in adhesive film and wearable electronics. This new technology opens a new way to reprocess thermoset in a fashion similar to thermoplastic in the current polymer industry.

On the metal thermoplastic composite interface of Ti alloy/UHMWPE-Elium® laminates

Abstract: Thermoplastic fiber metal laminate (T-FML) is a new hybrid composite material, which is a combination of sandwiched metal and complete thermoplastic fiber reinforced polymer (FRP). Due to its superior properties contributed from the unique combination of metal and FRP's, it has been applied in various advanced fields, like aerospace, and automotive. However, poor adhesion between inhomogeneous material surfaces of fiber, metal, and matrix in T-FML makes the whole system weaker. In this work, the Ti6Al4V (titanium alloy) and ultrahigh molecular weight polyethylene fiber (UHMWPE) reinforced thermoplastic (Elium®) polymeric composite were combined together to form a T-FML. Fiber surface functionalization by PDA (polydopamine) coating with MWCNT (Multiwalled carbon nanotubes) has been adopted to enhance the bonding between the fiber and matrix. Ti6Al4V metal surface treatment by anodization with postprocessing of etching and annealing process has been adopted to enhance the interfacial bonding between metal thermoplastic composite interface (MTCI). The double cantilever beam test was utilized to evaluate the G1C (Mode I interlaminar fracture toughness at MTCI) for the T-FML sample with fiber surface functionalization and metal surface treatment. The result shows, after metal surface treatment, the average G1C can be immediately increased from 0.25 kJ/m2 (pristine titanium alloy with pristine fiber) to 1.57 kJ/m2 for surface-treated titanium alloy with pristine fiber. The PDA only coating for UHMWPE fiber enhanced the G1C from 1.57 kJ/m2 to 1.84 kJ/m2. PDA fiber surface functionalization with MWCNT coating enhanced the G1C further to 2.54 kJ/m2.

4D Printing via an Unconventional Fused Deposition Modeling Route to High-Performance Thermosets

Abstract: An unprecedented four-dimensional (4D) printing process allowing high-performance and shape memory thermoset to be printed, for the first time, by fused deposition modeling (FDM) with isotropic properties has been achieved. Bisphenol A-based epoxy and benzoxazine were formulated to a low-temperature thermoplastic and high-temperature thermoset resin, which is melt-extrudable and can be postcured into covalently cross-linked material. Carbon nanotube (CNT) was added in the resin to work as both mechanical enhancement filler and rheology modifier to prevent shape deformation during postcuring process. The cross-layer reaction fuses individual layers into an integrity, thus eliminating layer delamination induced by FDM, offering isotropic mechanical properties regardless of the printing orientations. The highly cross-linked network provides outstanding mechanical strength and superb thermal stability. The excellent shape memory performance with fast recovery rate and large recovery degree is also obtained in the three-dimensional (3D) printed composites.

The behaviour of thermoplastic and thermoset carbon fibre composites subjected to low-velocity and high-velocity impact

Abstract: The present paper describes the results from experimental and theoretical modelling studies on the behaviour of continuous carbon fibre/polymer matrix composites subjected to a relatively low-velocity or high-velocity impact, using a rigid, metallic impactor. Drop-weight and gas-gun tests are employed to conduct the low-velocity and high-velocity impact experiments, respectively. The carbon fibre composites are based upon a thermoplastic poly(ether–ether ketone) matrix (termed CF/PEEK) or a thermoset toughened epoxy matrix (termed CF/Epoxy), which has the same fibre architecture of a cross-ply [03/903]2s lay-up. The studies clearly reveal that the CF/PEEK composites exhibit the better impact performance. Also, at the same impact energy of 10.5 ± 0.3 J, the relatively high-velocity test at 54.4 ± 1.0 m s−1 leads to more damage in both types of composite than observed from the low-velocity test where the impactor struck the composites at 2.56 m s−1. The computationally efficient, two-dimensional, elastic, finite element model that has been developed is generally successful in capturing the essential details of the impact test and the impact damage in the composites, and has been used to predict the loading response of the composites under impact loading.

Mechanical–Chemical Recycling of Low-Density Polyethylene Waste with Polypropylene

Abstract: The global increasing consumption of thermoplastic such as polyethylene and polypropylene has caused the generation of enormous amount of polymeric waste that are a challenge for solid waste management and represents a severe polluting agent, mainly for the marine life. Mechanical recycling is an important alternative to decrease the volume of polymeric waste. However, the mixture of different thermoplastic and other materials on the same object depreciates the properties of the recycled polymer due to the formation of immiscible blends. The aim of this study has been to evaluate the recycling of the post-industrial low-density polyethylene waste (LDPE waste) in presence of polypropylene using thermomechanical processing and thermochemical treatment of the material. For it, blends of LDPE waste and virgin polypropylene (PP) containing until 30 wt% of PP has been prepared with incorporation of zeolite ZSM-5 and Ziegler–Natta catalysts and submitted to the thermal treatment under controlled conditions of temperature and nitrogen flow. The results show the action of zeolite catalyst as modifier of the polymeric structure during step of the thermomechanical processing of the material. The catalysts have caused considerable changes on properties of the LDPE/PP blends, depending of the experimental conditions. The treatment of polymeric waste in presence of catalyst presents potential for recycling of polymeric materials with high contamination by other polymers and can generate recycled materials with improved properties.

On flexural and pull out properties of 3D printed PLA based hybrid composite matrix

Abstract: Fused deposition modelling (FDM) has been widely explored for number of commercially available virgin thermoplastics (such as: poly lactic acid (PLA), nylon, acrylonitrile butadiene styrene (ABS) etc.), thermoplastic based composites and printing conditions. But hitherto little has been reported on flexural and pull-out properties of 3D printed PLA based hybrid composite matrix (having magnetostrictive properties) especially in structural engineering applications. In the present work an effort has been made for 3D printing of PLA hybrid composite matrix (having magnetic characteristics) to investigate the flexural and pull out properties. The photo micro-graphic analysis and Shore D hardness has been performed on the printed samples and multifactor optimization tool has been used for optimizing the printing conditions. From multifactor optimization viewpoint it has been ascertained that infill density 100%; infill angle 45°; and infill speed 90mm/s are the best printing conditions. Further from morphological testing it has been observed that mechanical properties (flexural and pull out) are dependent upon the hardness, surface porosity and surface roughness (Ra). The creo structural analysis supported with photomicrographs have been performed on the samples prepared at best setting of input parameters and it has been found that strain increases downward along the thickness and is maximum at lowest layer due to which the failure starts from the base line in flexural testing.

Damping, impact and flexural performance of novel carbon/Elium® thermoplastic tubular composites

Abstract: The current research presents a first attempt to manufacture thermoplastic tubular composites using carbon fibre as reinforcement and an innovative Elium® resin as the matrix material using Bladder Assisted Resin Transfer Moulding (B-RTM) manufacturing process. The manufacturing process parameters required to achieve a fully impregnated thermoplastic composites were established, and the parts have undergone impact, flexure, and vibration damping tests. The mechanical properties and the failure modes are compared with the tubes manufactured with conventional epoxy matrix. During impact testing, thermoplastic tubular composites have shown 16.3% and 18.9% higher peak load and major damage energy respectively compared to carbon/epoxy tubes. They have also shown distinctive failure modes, with acrylic Elium® composites tubes undergoing more ductile and spreaded failure whilst epoxy composites have shown brittle and catastrophic failure. Flexural tests have shown comparable load-carrying capability, higher strain to failure, and less delamination for carbon/Elium® composites compared to carbon/epoxy composites. These are attributed to the presence of microductlilty and other associated matrix deformation features shown during the fractographic analysis of carbon/Elium® composites. Vibration modal analysis tests have shown 21.7% higher structural damping for carbon/Elium® composite measured at different output locations on the tube. The differences in the failure mechanisms and the underlying reasons for the improvement shown by thermoplastic Elium® composite tubes under different mechanical tests are deliberated in this paper.

Recyclable Polyethylene Insulation via Reactive Compounding with a Maleic Anhydride-Grafted Polypropylene

Abstract: The most common type of extruded power cable insulation is based on cross-linked polyethylene (XLPE), which cannot be recycled as a thermoplastic material. Hence, thermoplastic insulation materials...

Process-structure-property of additively manufactured continuous carbon fiber reinforced thermoplastic: an investigation of mode I interlaminar fracture toughness

Abstract: The process-structure-property (PSP) relationship of continuous carbon fiber reinforced thermoplastics manufactured through fused filament fabrication was investigated for the first time, specifica...

Study of the surface quality of carbon fiber–reinforced thermoplastic matrix composite (CFRTP) machined by abrasive water jet (AWJM)

Abstract: Carbon fiber-reinforced thermoplastics (CFRTP) have great interest nowadays due to their excellent mechanical properties and lightness. However, in opposition to thermoset matrix composites, there is a lake in the research about machining processes of these materials. Their low glass transition temperature is a handicap when conventional machining is used. An alternative is abrasive water jet machining (AWJM) because it does not cause thermal damage. However, the surface quality produced by this process must be studied and related to the cutting parameters. This article studies the surface quality generated by water jet machining in a low melting point thermoplastic matrix composite material. The kind of thermoplastic used is a TPU (polyurethane). The combination of a high-strength material (carbon fiber) with a low-strength material (thermoplastic matrix) makes machining difficult and can generate a poor surface finish. The influence of cutting parameters has been evaluated through an ANOVA analysis. A mathematical model that relates the surface quality with the cutting parameters has been established by means of a response surface methodology (RSM). The combination of a hydraulic pressure of 250 MPa with a traverse speed of 300 mm/min and an abrasive mass flow of 170 g/min produces the best surface quality. Finally, the main flaws when CFRTP is water jet machined have also been identified.

Thermoplastic multifunctional polysiloxane-based materials from broad gradient-transition multiphase separation

Abstract: The current work demonstrates broad gradient-transition multiphase separation for thermoplastic polysiloxane-based polymers, featuring mechanical robustness, shape memory property and healing-ability. Conventional thermoplastic elastomers are generally fabricated by embedding hard nanodomains as physical crosslinks into a soft matrix. However, it is difficult to achieve shape-memory capability in polysiloxane-based polymers with this structure because polysiloxane chains have low glass transition temperature (Tg) and are non-crystalline with little capacity to store the entropy energy after deformation. Herein, by taking advantage of the thermodynamic incompatibility between polysiloxane and polyimide, as well as the chain rigidity and linearity of polyimide, a novel poly(imide siloxane) polymer is developed, in which the flexible polysiloxane segments curled into soft nanodomains on low Tg, with increasing Tg towards the glassy polyimide matrix. The formed gradient-transition layers served as switch segments to trigger shape recovery, maintain a temporary shape and the innermost hard segments were assembled into netpoints with the assistance of gradient layers to prevent chain slippage. The disassociation of the inferior intermolecular interactions within the gradient-transition layers and the quasi-permanent crosslinking of the innermost nanodomains with the highest Tg synergistically endowed polymers with heat-assisted self-healing ability. Moreover, the hard matrix provided a protective barrier against external forces, leading to high mechanical robustness. Based on these features, we believe that these polymers are advantageous for various applications, such as implants, vascular stents and other medical devices.