High-performance Thermoplastic Polymer Research Articles

Characterize the high-temperature steady-state rheological behavior and Arrhenius activation of PEEK via strain rate jump tensile tests

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer with diverse industrial applications, such as aerospace, automotive, electronics, and medical devices. However, systematic research on its high-temperature rheological characteristics is inadequate. In this study, strain rate jump tensile tests were introduced to examine the steady-state rheology phenomena and strain rate sensitivity of PEEK at four different temperatures and nine different strain rates. Theoretical analysis based on the free volume theory and the Arrhenius law was also carried out to further analyze the transition of PEEK from Newtonian flow to non-Newtonian flow. Results indicate that PEEK materials exhibit a transition from Newtonian flow to non-Newtonian flow similar to metal materials at high temperatures. The transition point from Newtonian flow to non-Newtonian flow is marked by the emergence of steady-state rheology and its characteristic stress. Theoretical analysis demonstrates that the transition of PEEK is in accordance with the Arrhenius low. Moreover, its apparent activation energy (1.42 eV) is significantly lower than that of metal materials (5.28 eV), indicating a lower energy barrier and an easier transition. The strain rate sensitivity index correlates negatively with rising temperatures, especially at lower rates. This study enhances understanding of PEEK's rheological characteristics at high temperatures, aiding the development and application of high-performance thermoplastic materials.

Comprehensive evaluation of interfacial interactions optimization for CF reinforced high-performance thermoplastic composites by electrochemical deposition of conjugated polymers

The mechanical properties of carbon fiber (CF) reinforced high-performance thermoplastic composites are significantly compromised due to inadequate interface bonding between CF and matrix. In this study, electrochemical polymerization techniques were employed to modify CFs with polypyrrole (PPy), poly-aniline (PANI), and poly-o-phenylenediamine (PoPd), to systematically investigate the impact of conjugated polymers on the interfacial properties of CF/copoly (phthalazinone ether sulfone ketone)s (PPESK) composites through a combination of experimental and molecular dynamics (MD) approaches. The findings revealed distinct differences among these conjugated polymers in terms of their effects on both IFSS and ILSS for CF/PPESK composites. Among all tested laminates, PoPd@CF-60s/PPESK exhibited the highest IFSS, ILSS and flexural strength values of 39.8 MPa, 75.6 MPa, and 1494 MPa, respectively, 94.1 %, 20.6 %, and 47.6 % higher than those of CF-desized/PPESK, without compromising CFs strength and thermal resistance of CF/PPESK composites. MD simulations combined with fracture morphology analysis confirmed that compatibility between conjugated polymers and matrix played a pivotal role in enhancing interface properties for CF/PPESK composites. Furthermore, the AFM outcomes demonstrated that the PoPd layer could serve as the modulus transition layer between the CF phase and the PPESK phase, which effectively enhancing the load transfer efficiency between the two phases under external forces. To summarize, this work presents a straightforward yet non-destructive approach that effectively enhances the interface strength within advanced CF reinforced high performance thermoplastic polymer composites (CFRHPTPs).

DFT-based investigation of polyetherketoneketone materials for surface modification for dental implants

BackgroundPolyetherketoneketone (PEKK) is a high-performance thermoplastic polymer with unique structural and mechanical properties that make it a promising candidate for surface modification of dental implants. This study was conducted to investigate the feasibility of PEKK for this purpose using the Cambridge Serial Total Energy Package (CASTEP) code based on density functional theory (DFT).MethodsThis study examined the ground state energy, structural properties, thermodynamic behavior, cohesive energy, refractive index, stress analysis, mechanical properties, and anisotropic behavior of PEKK.ResultsThis study found that PEKK has a complex crystal structure with an orthorhombic unit cell shape, triclinic lattice type, and a centered structure. It also has a 2D layered structure owing to the presence of carbonyl groups, which provides a large surface area for interaction with biological tissues. Thermodynamic analysis showed that PEKK exhibited bond elongation and structural changes at 380 °C, indicating thermal degradation. The cohesive energy of PEKK was calculated to be – 440 eV, indicating its stability and structural integrity. PEKK has a complex refractive index, with real and imaginary components that affect its optical properties. Stress analysis showed that PEKK is resistant to shear deformation and has high hydrostatic stress, which contributes to its stability and biocompatibility.ConclusionThe mechanical properties of PEKK, including its high stiffness, resistance to volume change under pressure, and ability to accommodate natural movements, make it suitable for surface modification of dental implants.

Evaluation of Material Extrusion Printed PEEK Mold Inserts for Usage in Ceramic Injection Molding

The rapid tooling of mold inserts for injection molding allows for very fast product development, as well as a highly customized design. For this, a combination of rapid prototyping methods with suitable polymer materials, like the high-performance thermoplastic polymer polyetheretherketone (PEEK), should be applied. As a drawback, a huge processing temperature beyond 400 °C is necessary for material extrusion (MEX)-based 3D printing; here, Fused Filament Fabrication (FFF) requires a more sophisticated printing parameter investigation. In this work, suitable MEX printing strategies, covering printing parameters like printing temperature and speed, for the realization of two different mold insert surface geometries were evaluated, and the resulting print quality was inspected. As a proof of concept, ceramic injection molding was used for replication. Under consideration of the two different test structures, the ceramic feedstock could be replicated successfully and to an acceptable quality without significant mold insert deterioration.

Tribological Properties of PEEK and Its Composite Material under Oil Lubrication

PEEK (Poly Ether Ether Ketone) is a high-performance thermoplastic polymer with excellent mechanical, thermal and chemical stability. PEEK has good performance, and is widely used in hydraulic motors. However, there are few studies on the friction and wear properties of materials under the condition of oil lubrication with wide application. The modification of PEEK and the expansion of its application have become a hot research topic in the industry. This study focuses on the modification of the design of PEEK and explores the friction and wear characteristics of self-lubricating materials under different modification schemes. Friction and wear samples were prepared using PEEK-modification pelletizing and injection-molding processes, followed by fixed-condition friction and wear tests. The tribological mechanisms and wear properties of the materials under different modification schemes were analyzed, leading to the identification of several sets of improved reinforced materials. Experimental results demonstrate that modified materials can enhance surface tribological performance, with the best modification effect observed at an SCF filling rate of 15%. The modified PEEK material can better meet the requirements of specific applications, such as high-temperature environments, chemically aggressive environments, or applications requiring high strength and wear resistance.

Enhanced mechanical performance of bamboo fiber/polypropylene composites via micro-nano reinforcing strategy

Developing high-performance plant fiber-reinforced thermoplastic polymer composites using environmentally friendly and cost-effective methods remains a significant challenge. In this study, we present a novel micro-nano strategy for producing robust short bamboo fibers (BFs) reinforced polypropylene (PP) composites (SBFPCs) without the need for chemical modification. Our approach involves the utilization of purified short micron BFs, which is surface-coated with holocellulose nanofibers (HNFs) extracted from bamboo parenchyma cells (BP). Through conventional injection processing, the resulting SBFPCs demonstrate remarkable mechanical enhancements with just a 0.2 wt% addition of HNFs compared to control samples. Notably, the mechanical properties of our SBFPCs surpass those of most reported short plant fiber-reinforced thermoplastic composites. The superior mechanical performance of our SBFPCs can be attributed to several factors, including the use of purified micron BFs with optimal aspect ratios as the primary reinforcement phase, enhanced interfacial mechanical interlocking between BFs and the PP matrix facilitated by the addition of HNFs, and the potential dispersion of HNFs within the PP matrix at submicron or nanoscale as a secondary reinforcement phase. This study highlights the promising application of SBFPCs in engineering areas with stringent mechanical requirements.

Surface Roughness of Polyetheretherketone Printed by Fused Deposition Modeling: A Pilot Study Investigating the Impact of Print Layer Thickness and Polishing Method

Polyetheretherketone is a high-performance thermoplastic polymer that can be used in 3D printing by fused deposition modeling, and is a promising material for dental applications. Some printing parameters are sensitive and can influence the properties of the printed object. Thus, this work aims to evaluate the influence of the print layer thickness on the surface roughness of polyetheretherketone before and after polishing and to verify the effectiveness of the polishing method used, as well as to compare it with the results obtained using polymethyl methacrylate as the control group. Specimens with different impression layer thicknesses were printed with polyetheretherketone (Group A—0.1 mm and Group B—0.3 mm). Additionally, a control group with polymethyl methacrylate specimens was milled. Roughness evaluation was conducted using a contact profilometer after the specimens had been printed (before polishing). Then, silicon carbide sandpaper was used to polish the surface, and the roughness was reassessed. Differences were observed between specimens regarding the print layer thickness and the roughness, with the 0.3 mm layer thickness showing the lowest roughness values. The results of this pilot study suggest that the surface roughness of fused deposition modeling printed polyetheretherketone is influenced by print layer thickness, with the lowest roughness seen at a thickness of 0.3 mm.

Closing the loop in space 3D printing: Effect of vacuum, recycling, and UV aging on high performance thermoplastics produced via filament extrusion additive manufacturing

The outlook for space exploration, and the long-term sustainable presence of humans in space, rely upon the advancement of in-situ manufacturing capabilities. In-space additive manufacturing (AM) has gained significant attention due to its potential to produce spare parts in-situ and facilitate repairs for extending space missions. However, to date, there is no AM system capable of processing high-performance engineering thermoplastic polymers within uncontrolled space conditions (i.e., reduced gravity, vacuum, and radiation environment). Additionally, the effect of ultra-violet (UV) radiation on printed parts has remained unexplored. In this work, a custom-built filament extrusion AM breadboard has been developed and tested enabling the fabrication of engineering thermoplastic polymers, whereby the machine was placed inside a vacuum chamber to partly mimic the harsh space environment. Mechanical (tensile and flexural) and thermal (thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis) tests were conducted on the printed specimens before and after exposure to UV aging. Moreover, the printed geometries underwent a recycling process involved the shredding of the pristine 3D-printed polymeric samples, the drying of the obtained granulates and finally the extrusion of 3D-printable filaments. The polymeric recycled 3D-printed specimens were then subjected to further mechanical and thermal testing, offering valuable insights into the feasibility of in-space AM and the potential to augment the circularity of the printed parts. The results of the mechanical and thermal tests, together with the effect of vacuum printing, UV aging, and recycling, are provided within the manuscript. This work cements the basic building blocks to sustainably advance on-orbit and in-space infrastructure, and paves the way for long-term human space missions.

Multiscale Mechanical Characterization of Polyether-2-ketone (PEKK) for Biomedical Application.

Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.

State-of-the-art polyetheretherketone three-dimensional printing and multifunctional modification for dental implants.

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer with an elastic modulus close to that of the jawbone. PEEK has the potential to become a new dental implant material for special patients due to its radiolucency, chemical stability, color similarity to teeth, and low allergy rate. However, the aromatic main chain and lack of surface charge and chemical functional groups make PEEK hydrophobic and biologically inert, which hinders subsequent protein adsorption and osteoblast adhesion and differentiation. This will be detrimental to the deposition and mineralization of apatite on the surface of PEEK and limit its clinical application. Researchers have explored different modification methods to effectively improve the biomechanical, antibacterial, immunomodulatory, angiogenic, antioxidative, osteogenic and anti-osteoclastogenic, and soft tissue adhesion properties. This review comprehensively summarizes the latest research progress in material property advantages, three-dimensional printing synthesis, and functional modification of PEEK in the fields of implant dentistry and provides solutions for existing difficulties. We confirm the broad prospects of PEEK as a dental implant material to promote the clinical conversion of PEEK-based dental implants.

Preparation and Characterization of Polycarbonate-Based Blend System with Favorable Mechanical Properties and 3D Printing Performance.

Recently, material extrusion (MEX) 3D printing technology has attracted extensive attention. However, some high-performance thermoplastic polymer resins, such as polycarbonate (PC), cannot be processed by conventional MEX printing equipment due to poor processing performance. In order to develop new PC-based printing materials suitable for MEX, PC/poly(butylene adipate-co-terephthalate) (PBAT) blends were prepared using a simple polymer blending technique. It was found that the addition of PBAT component significantly improved processing performance of the PC, making the blends processable at 250 °C. More importantly, the PC was completely compatible with the PBAT, and the PBAT effectively reduced the Tg of the blends, endowing the blends with essential 3D printing performance. Furthermore, methyl methacrylate-butadiene-styrene terpolymer (MBS) was introduced into the PC/PBAT blends to improve toughness. SEM observations demonstrated that MBS particles, as stress concentration points, triggered shear yielding of polymer matrix and absorbed impact energy substantially. In addition, the MBS had little effect on the 3D printing performance of the blends. Thus, a PC/PBAT/MBS blend system with favorable comprehensive mechanical properties and 3D printing performance was achieved. This work can provide guidance for the development of novel MEX printing materials and is of great significance for expanding the variety of MEX printing materials.

Thermophysical Behavior of Polycarbonate: Effect of Free Quenching above and below the Glass Transition Temperature

Polycarbonate is a tough, amorphous and transparent high performance thermoplastic polymer. It is used in many fields of application due to its versatile thermophysical, mechanical and optical properties. However, one of its drawbacks is its relatively high thermal conductivity which prevents its application as an insulating material. An appropriate heat treatment can therefore be a useful route to improve the thermal insulating property. The objective of this work is to study the effect of heat treatment; namely the influence of the quenching temperature above and below the glass transition temperature (Tg) on the thermophysical properties of neat polycarbonate (PC). The effect of the quenching temperature above Tg was also studied for neat poly (methyl methacrylate) (PMMA). The effect of residual stresses (RS) generated by the free quenching process on the thermophysical properties of neat PC was investigated. The thermal conductivity (k) and thermal diffusivity (a) of neat PC were measured using a periodic measurement method (DICO), (DIffusivity and COnductivity), at room temperature. The DICO method developed in the CERTES laboratory (Center for Studies and Research in Thermal, Environment and Systems of Paris 12 University), allows simultaneous access to the conductivity and thermal diffusivity from which the specific heat (Cp) can then be deduced. This work showed that the quenching from a high temperature above Tg did not affect the thermal conductivity and thermal diffusivity of both PC and PMMA. However, quenching from a temperature below Tg (130 ° C) caused a decrease of both the thermal. In fact the thermal conductivity of PC annealed at 130 ° C which is 0.22 W. m-1 .K-1 decreased to 0.06 W. m-1 .K-1 and 0.14 W. m-1 .K-1 after quenching at 0° C and 40 ° C respectively. This means that quenching would therefore improve the insulating capacity of PC compared to the material which has undergone only annealing. Contrary to the thermal conductivity, the values of the specific heat capacity in this temperature range ( 0° C – 40° C) significantly increased as a result of quenching. They increase from 1118 J. kg-1. K-1 for the annealed sample to 1290 J. kg-1. K-1 for PC quenched at 0° C and increased to 2221 J. kg-1. K-1 for PC quenched at 40 ° C which corresponds to an increase by 98 %. It was also found that the values of thermal conductivity and specific heat were in good agreement with those reported in the literature for neat PC samples quenched below Tg.

(Invited) A New Frontier in Hybrid Inorganic-Organic Membranes for Redox Flow Batteries: The Polyketone-Based Membranes

Zinc iodide flow batteries (ZIFBs) are amongst the most promising chemistries to substitute the expensive and less energy intensive Vanadium Flow Batteries (VFBs). One of main problems related to this technology is the crossover of water due to the transport of Zn2+. One possible approach is the development of new ion-exchange membranes (IEMs). For practical applications they are required to possess high ionic conductivity, high thermal stability, long lifetime, and electrical insulation. The preparation of polymeric materials with such high-performance properties is still challenging and can lead to high prices, hindering their widespread use in energy conversion technologies. This is even more difficult when considering anion conducting membranes [1-3].Polyketones (PK) are known to be high performance thermoplastic polymers with applications ranging from fire-retardants film coatings, packaging, and fibers, resulting from their high thermal and chemical stability. They can be obtained in high yields by copolymerization of inexpensive and readily available feedstocks such as ethylene and carbon monoxide. Our group proved that PK with alternating 1,4-dicarbonyl repeating units constitute an ideal starting point to access a wide class of modified polymers by simple Paal-Knorr cyclization, to gain pyrrole-N-bound functional groups stemming from the aliphatic backbone [4-5].Different ion-conducting membranes have been developed and the effect of reaction conditions on their thermal properties, chemical stability, and their conductivity in a wide range of frequencies have been assessed by broadband electric spectroscopy to shed light on the conduction mechanisms [4, 6]. The more promising material developed has been tested in a single cell redox flow battery obtaining promising results.The proposed conducting polymers combine the thermal stability of the aliphatic PK structure with the chemical flexibility given by the groups derived from functionalized amines branching out, proving to be highly tailorable, with possible applications in current energy conversion technologies. Acknowledgements: The authors wish to thank the Research Projects of Relevant National Interest (PRIN 2017) of the Italian Ministry of Education, University and Research “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)” (Prot. 2017YH9MRK) and SID2020 Project of Department of Industrial Engineering, University of Padova “A New frontier in Hybrid Inorganic-Organic Membranes for Energy Conversion and Storage Devices” (Prot. BIRD201244) for funding.

The effect of branched carbon nanotubes as reinforcing nano-filler in polymer nanocomposites

This work discusses the mechanical and dissipative properties of nanocomposite materials made of a high-performance thermoplastic polymer (polybutylene terephthalate, PBT) integrated with branched carbon nanotubes (bCNTs) as nanofiller. The storage and loss moduli as well as the loss factor/damping ratio of the nanocomposites are experimentally characterized for increasing bCNT weight fractions (wt% bCNT) upon variations of the input cyclic strain amplitude and of the input frequency, respectively. The trends obtained for the nanocomposites mechanical properties indicate improvements both in storage and loss modulus by increasing the bCNT weight fraction from 0.5% to 2%. The striking differences between the damping capacities exhibited by CNT/polymer and bCNT/polymer nanocomposites are discussed to shed light onto the different underlined mechanics of the nanocomposites. Due to the stick–slip relative sliding motion of the polymer chains with respect to the straight CNTs, CNT/PBT nanocomposites are known to exhibit a peak in the damping vs. strain amplitude curves, past which, the damping capacity shows a monotonically increasing trend due to the conjectured sliding of the polymer crystals. On the other hand, we show for the first time that bCNT/PBT nanocomposites do not exhibit a peak in the damping capacity but rather a plateau after an initial drop at low strains. This behavior is attributed to the much reduced mobility of the branched CNTs and the lack of formation of crystalline structures around the bCNTs.

Graphene filled polyetheretherketone (PEEK) composites made by melt-compounding

In the present work, a graphene nanocomposite material using as matrix a high performance thermoplastic polymer (PEEK) is presented. Composite was made by a simple extrusion-compounding process, followed by an injection-moulding process. The main advantage of this process is that it could produce large quantities at the scales needed for use in industrial applications as structural applications. Nanocomposites with different percentages of graphene 0.5, 1, 3, 5 and 10 wt.% were characterized and compared with neat PEEK as baseline. The mechanical tests showed that the Young´s modulus increased when adding graphene while the strenght remained constant. In addition, a change in the failure mode was observed when the graphene was added. Nanocomposites with high contents of graphene had lower strain at break than neat PEEK.

High performance, but low cost and environmental impact? Integrated techno-economic and life cycle assessment of polyoxazolidinone as a novel high-performance polymer

Life Cycle Assessment (LCA) and Techno-economic Assessment (TEA) are crucial for a comprehensive evaluation of the novel high-performance thermoplastic polymer polyoxazolidinone (POX).

Polyketone Functionalization: New Ways to Anion Conducting Polymers

Ion-exchange membranes (IEMs) are at the core of many energy storage and conversion devices, such as fuel cells and redox flow batteries, being responsible for the migration of ionic species, separating the fuel stocks, and providing support to the electrode assemblies. For practical applications they are required to possess not only high ionic conductivity, but also specificity, thermal stability, long lifetime, and electrical insulation. The preparation of polymeric materials with such high-performance properties is still challenging and can lead to high prices, hindering their widespread use in energy conversion technologies. This is even more arduous when considering polymers to be used in anion conducting membranes, due to the need for the extra chemical stability and ability to withstand alkaline conditions at high temperatures for long periods of time [1].Polyketones are known to be high performance thermoplastic polymers with applications ranging from fire-retardants film coatings, packaging, and fibers, resulting from their high thermal and chemical stability. They can be obtained in high yields by copolymerization of inexpensive and readily available feedstocks such as ethylene and carbon monoxide. Our group proved that polyketones with alternating 1,4-dicarbonyl repeating units constitute an ideal starting point to access a wide class of modified polymers by simple Paal-Knorr cyclization, to gain pyrrole-N-bound functional groups stemming from the aliphatic backbone [2].This is a new account on our research on the ion conducting polymeric materials derived from polyketone, obtained by reaction with variously functionalized amines, and their easy conversion to anion exchange materials. The effect of reaction conditions on their thermal properties and chemical stability in alkaline media has been studied, and their conductivity in a wide range of frequencies assessed by broadband electric spectroscopy to shed light on the conduction mechanisms.The proposed conducting polymers combine the thermal stability of the aliphatic polyketone structure with the chemical flexibility given by the groups derived from functionalized amines branching out, proving to be highly tailorable, with possible applications in current energy conversion technologies. Acknowledgements: The authors wish to thank the Research Projects of Relevant National Interest (PRIN 2017) of the Italian Ministry of Education, University and Research “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)” (Prot. 2017YH9MRK) and the SID2020 Project of the Department of Industrial Engineering, University of Padova “A New frontier in Hybrid Inorganic-Organic Membranes for Energy Conversion and Storage Devices” (Prot. BIRD201244) for funding.

The Surface Characterisation of Fused Filament Fabricated (FFF) 3D Printed PEEK/Hydroxyapatite Composites.

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer which has found increasing application in orthopaedics and has shown a lot of promise for ‘made-to-measure’ implants via additive manufacturing approaches. However, PEEK is bioinert and needs to undergo surface modification to make it at least osteoconductive to ensure a more rapid, improved, and stable fixation that will last longer in vivo. One approach to solving this issue is to modify PEEK with bioactive agents such as hydroxyapatite (HA). The work reported in this study demonstrates the direct 3D printing of PEEK/HA composites of up to 30 weight percent (wt%) HA using a Fused Filament Fabrication (FFF) approach. The surface characteristics and in vitro properties of the composite materials were investigated. X-ray diffraction revealed the samples to be semi-crystalline in nature, with X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealing HA materials were available in the uppermost surface of all the 3D printed samples. In vitro testing of the samples at 7 days demonstrated that the PEEK/HA composite surfaces supported the adherence and growth of viable U-2 OS osteoblast like cells. These results demonstrate that FFF can deliver bioactive HA on the surface of PEEK bio-composites in a one-step 3D printing process.

Understanding the Stereochemical Effect on the Properties of Emerging Thermosets: Sustainable Polybenzoxazines

Exploration of the properties of monomers by modulating their stereochemistry is not well reported in polybenzoxazines (PBzs). Isosorbide contains a rigid bicyclic (endo–exo-configuration) core that has shown promise in high-performance thermoplastic polymers. In this report, new chiral PBzs were prepared from industrially available feedstocks, carbohydrate-derived (isosorbide), and lignin- or cashew nut waste-sourced renewable phenols (cardanol and guaiacol). A fully biobased benzoxazine monomer based on a one-step condensation reaction of isosorbide diamine (isa) with phenols was carried out for 15 min under microwave and solvent- and catalyst-free conditions. Structural elucidation of monomers was achieved by two-dimensional (2D) NMR spectroscopy [heteronuclear single quantum correlation (HSQC) and COSY (correlated spectroscopy)]. The “isa”-based monomer revealed a comparable ring-opening polymerization temperature and a good processing window for the widely available bisphenol-A/aniline-based monomer. The resultant polymers showed a higher Tg, better thermomechanical properties, and adhesive strength compared to other classical petrobased PBzs. The current work extends the importance of the major component of the sugar-derived isohexide family member, isosorbide, in polybenzoxazine chemistry and suggests that stereocontrol in the monomer is another approach to affect the thermomechanical properties of this upcoming class of high-performance phenolic polymer.

The technology of continuous fibre-reinforced polymers: a review on extrusion additive manufacturing methods

Additive manufacturing technologies have transitioned from the fabrication of prototypes to final product manufacturing with competitive mechanical performance. The use of materials with high strength to weight ratio, and more specifically continuous fibre-reinforced composites, has demonstrated potential when fabricated through fused filament fabrication (FFF). The development and evaluation of such technologies has attracted a lot of attention in recent years, from both academic researchers and from industry, and a plethora of different techniques for its achievement has been proposed. This review presents different methods of FFF for the fabrication of continuous fibre-reinforced composite components as described in both patent and scholarly research literature. Different print head designs and techniques for combining and depositing polymers reinforced with continuous fibre have been developed including pre-impregnation, the use of multiple nozzles for the separate deposition of the fibre and the matrix material, and in situ impregnation of the reinforcing fibre with the matrix material. This review identifies the challenges associated with each of these approaches such as achieving a successful fibre/matrix impregnation, cutting of the continuous fibres during processing, and the introduction of high-performance thermoplastic polymers as the matrix material.