Excellent Low-temperature Flexibility Research Articles

Multi-walled carbon nanotubes/carbon black/rPLA for high-performance conductive additive manufacturing filament and the simultaneous detection of acetaminophen and phenylephrine

The combination of multi-walled carbon nanotubes (MWCNT) and carbon black (CB) is presented to produce a high-performance electrically conductive recycled additive manufacturing filament. The filament and subsequent additively manufactured electrodes were characterised by TGA, XPS, Raman, and SEM and showed excellent low-temperature flexibility. The MWCNT/CB filament exhibited an improved electrochemical performance compared to an identical in-house produced bespoke filament using only CB. A heterogeneous electrochemical rate constant, kobs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${k}_{obs}^0$$\\end{document} of 1.71 (± 0.19) × 10−3 cm s−1 was obtained, showing an almost six times improvement over the commonly used commercial conductive CB/PLA. The filament was successfully tested for the simultaneous determination of acetaminophen and phenylephrine, producing linear ranges of 5–60 and 5–200 μM, sensitivities of 0.05 μA μM−1 and 0.14 μA μM−1, and limits of detection of 0.04 μM and 0.38 μM, respectively. A print-at-home device is presented where a removable lid comprised of rPLA can be placed onto a drinking vessel and the working, counter, and reference components made from our bespoke MWCNT/CB filament. The print-at-home device was successfully used to determine both compounds within real pharmaceutical products, with recoveries between 87 and 120% over a range of three real samples. This work paves the way for fabricating new highly conductive filaments using a combination of carbon materials with different morphologies and physicochemical properties and their application to produce additively manufactured electrodes with greatly improved electrochemical performance.Graphical abstract

Facile and solvent-free synthesis of a novel bio-based hyperbranched polyester with excellent low-temperature flexibility and thermal stability

In this work, a novel biobased hyperbranched polyester (HBPE) with excellent low-temperature flexibility (low Tg) and thermal stability, was prepared from the self-polycondensation of AB2 monomer based on methyl ricinoleate (MR), a commercially available derivative from castor oil. The AB2 monomer was facilely synthesized by UV-initiated thiol-ene addition between MR and 2-mercaptoethanol in the absence of solvents. The reaction parameters were systematically optimized, and the highest yield up to 98 % was achieved with almost complete conversion of double bond within 2 h. A series of HBPEs were then obtained via bulk polymerization of the AB2 monomer under different conditions. Among the four transesterification catalysts investigated, Ti(OBu)4 was demonstrated to be the most efficient one due to the higher polymerization efficiency and molecular weight (Mn = 13,000∼17,000 g/mol) of as-obtained HBPEs. And the degree of branching (DB) was estimated to be in the range of 0.30∼0.42. Notably, the HBPEs with dangling chains exhibited a low glass transition temperature (Tg) of ―42.8∼―59.2 °C, indicative of excellent low-temperature flexibility. TGA results indicated that the onset thermal degradation temperature under nitrogen exceeded 310 °C for all the HBPEs. In comparison to the polyrincinoleate as a linear polyester analogue, the HBPE behaved like Newtonian fluid behaviors with lower complex viscosities.

Grafting of Triphenylmethyl Group onto Polyurethane and the Impact on the Shape Recovery and Flexibility at Extremely Low Temperature

The bulky and rigid triphenylmethyl group was grafted onto polyurethane (PU) to reduce the molecular attractions between hard segments and to improve the mobility of the PU chain under freezing conditions. The triphenylmethyl-grafted PU exhibited improvement in the cross-link density, solution viscosity, maximum tensile stress, shape recovery at 10 °C, and low temperature flexibility compared with the plain PU. The soft segment melting was not affected by the grafted triphenylmethyl group, whereas the soft segment crystallization disappeared with the increase of the triphenylmethyl group content. The glass transition temperature (Tg) increased with the increase of the triphenylmethyl group content. The rapid increase of the tensile strength and shape recovery at 10 °C resulted from the cross-linking effect, whereas the strain at break and shape retention at -25 °C slightly decreased with the increase of the triphenylmethyl group content. The triphenylmethylgrafted PU displayed an excellent low temperature flexibility even at -50 °C due to the improved mobility of the PU chain compared to ordinary PU.

Characterization of Polyurethane Grafted with Bis(2-hydroxyethyl) Terephthalate

ABSTRACTBis(2-hydroxyethyl) terephthalate (BHETPA) was grafted onto polyurethane (PU) to investigate the effects of BHETPA, which contains a rigid aromatic group and flexible hydroxyethyl groups, on the physical properties of PU. The cross-link density, viscosity, tensile strength, and shape recovery notably increased with an increase of BHETPA due to chemical cross-linking by BHETPA. A PU sample demonstrated excellent low-temperature flexibility compared with plain PU, showing complete recovery at approximately 0°C. Therefore, grafting BHETPA onto PU modified the thermal behavior and greatly improved the tensile stress, shape recovery, and low-temperature flexibility of PU compared to plain PU.

Contrasting thermal behavior and low-temperature flexibility of PDMS-grafted and poly(2-ethylhexyl acrylate)-grafted polyurethane

ABSTRACTPolydimethylsiloxane (PDMS) was grafted onto polyurethane (PU) to form a P series, and 2-ethylhexyl acrylate (EHA) was graft-polymerized onto PU to form an E series. The spectroscopic, thermal, tensile, shape memory, and low-temperature flexibility properties of the P and E series were compared. With an increase in the PDMS content, the Tg of the P series gradually increased, whereas the Tg of the E series was not affected by an increase in the EHA content. The tensile strength of the P and E series sharply increased with the PDMS or EHA content without a significant decrease in tensile strain. The shape recovery of the P and E series remained high after four repeated tests. However, shape retention of the P series significantly decreased with an increase in the PDMS content. Finally, the P series demonstrated excellent low-temperature flexibility from −35°C compared with the E series and control PUs.

Characterization and Effect of Covalently Grafted Benzoic Acid on the Low Temperature Flexibility and Water Vapor Permeability of a Polyurethane Copolymer

ABSTRACTPolyurethane was grafted with benzoic acid (BA series) or a phenyl group (C series) to compare the impact of the grafted groups on water contact angle, tensile strength, shape memory, and low temperature flexibility. Benzoic acid is different from a phenyl group because it has both a rigid phenyl ring and a carboxyl group. The tensile strengths of the BA and C series substantially increased compared to that of the unmodified polyurethane. The BA series with the grafted benzoic acid exhibited excellent low temperature flexibility compared to the C series with the grafted phenyl group.

Synthesis, surface properties, and antibacterial activity of polysiloxane quaternary ammonium salts containing epoxy group

Polysiloxane containing tertiary amino group (P(SiO)m(SiOTA)n) with different molecular weight was synthesized through equilibrium polymerization of octamethylcyclotetrasiloxane (D4) and hydrolysis of N,N-diethyl-aminopropyl-methyldimethoxysilane (TAMDESi) in the presence of potassium hydroxide (KOH) as catalyst. After that, polysiloxane quaternary ammonium salt containing epoxy group (P(SiO)m(SiOQAEp)n) with different molecular weight and cationic concentration was obtained from P(SiO)m(SiOTA)n and epichlorohydrin by quaternization. It was shown that P(SiO)m(SiOQAEp)n surfactant exhibited low surface tension (γCMC < 30.00 mN/m) at the critical micellization concentration. The thermodynamic parameters of micellization (ΔG0m, ΔH0m, ΔS0m) indicated that the micellization of P(SiO)m(SiOQAEp)n surfactant was enthalpy-driven. In particular, it was found that the glass transition temperature (Tg) of P(SiO)m(SiOQAEp)n varied in the range of −15 ∼ –70 °C according to the molecular weights, and the thermal decomposition temperature was higher than 220 °C. This type of surfactant had excellent low temperature flexibility as well as good chemical and thermal stability. The antimicrobial activity was evaluated against Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus), respectively. The minimum bactericidal concentration (MBC) values against S. aureus and E. coli were below 1.5–2.8 × 10−5 mol/L, which indicated that P(SiO)m(SiOQAEp)n had strong antibacterial activity.

Preparation and Characterization of Polyurethane Copolymer Grafted with Polystyrene Side Chains

A polyurethane series containing grafted polystyrene and a Control series with free polystyrene were prepared, and their spectroscopic, thermal, tensile, shape-memory, and low-temperature flexibility properties were compared. The grafted polystyrene significantly reduced the ΔHc and also reduced the crystallization peaks of the polyurethane series. The tensile strength of the polyurethane series sharply increased with polystyrene content, whereas the Control series did not. The shape recovery of the polyurethane series remained high but the shape retention gradually decreased after four repeated tests. Lastly, the polyurethane series grafted with polystyrene demonstrated excellent low-temperature flexibility.

The characterization and effects of the alizarin series dyes grafted to polyurethane copolymers on the photoluminescence and low temperature flexibility

Alizarin-series dyes (alizarin, alizarin red S, alizarin yellow GG, or mordant orange) are grafted onto shape memory polyurethane (PU) through an allophanate bonding, and the photoluminescence and the low-temperature flexibility of the resulting PUs are tested. The PU is mainly composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly (tetramethyleneglycol) (PTMG), and 1,4-butanediol (BD), and the dye is connected, through another MDI, to the carbamate moiety of the PU chain. The PUs with different dye contents are characterized, and their shape recovery and photoluminescence properties are compared. With respect to the tensile mechanical properties, the maximum stress increases up to 50 MPa, and the strain remains above 1000 % even after the dye is grafted onto the PU. The shape recovery is as high as 99 %, and the shape retention improves as the dye content increases. Finally, the photoluminescence of the PUs is demonstrated by the luminescent light emission test, and the dye-grafted PU shows excellent low-temperature flexibility compared with that of linear PU.

Polyurethane for Special Sealing Applications and a Comparison to Rubber

Polyurethane materials have been known for decades. More recently thermoplastic polyurethanes (TPUs) have been introduced. These materials represent an alternative to either conventional thermoplastics or rubber, depending on the hardness. TPUs have a substantially higher tear propagation resistance and abrasion resistance than rubber, but for a long time they remained very vulnerable to hydrolysis and had poor compression set. Recent developments by raw material manufacturers have significantly improved the hydrolysis resistance. However, as sealing applications also require very good compression set values, the greatest improvements in this area have been achieved by the major seal manufacturers who synthesise their own polyurethane. TPUs are clearly the sealing material of choice for applications in hydraulics systems and are increasingly taking over from rubber. Recent developments have succeeded in obtaining excellent low-temperature flexibility combined with good compression set at high temperatures. For special sealing applications in the food sector, however, good hydrolysis resistance is no longer sufficient in itself. A new range of materials developed for this sector offers resistance to CIP/SIP media that is even better than that of many conventional elastomers.

Perfluoroether elastomer for wide fluid and temperature capabilities

Perfluoroether elastomer is based on a perfluoroether polymer backbone combined with silicone crosslinking. This combination produces products that have excellent low temperature flexibility and heat resistance, together with improved performance in fuels, solvents, acids, and alkalis compared to standard fluoroelastomers. The material family is available in a number of different forms including low viscosity flowing liquid, gum solid and also intermediate types of viscous fluid and paste. Variation of chemical compositions, filler loadings and rubber formulations make it possible to manufacture a variety of elastomeric products such as molded rubber parts, low modulus adhesives, soft coatinglayers, and very soft and sticky gels for a wide range of engineering applications.

Properties and Morphology of Segmented Copoly(ether urea)s with Uniform Hard Segments

Block copoly(ether urea)s with uniform hard blocks consisting of two urea groups possess appealing elastomeric properties. The crystal structure of a model bisurea illustrates the formation of long stacks of hydrogen-bonded urea groups. Thermal analysis of these polymers demonstrates the reversible melting of the hard blocks, causing the material to flow. The low glass transition temperature ensures excellent low-temperature flexibility. The morphology of the material consists of long stacks of associated hard blocks embedded in the soft phase. Elongation of the materials demonstrates their highly elastic behavior, with a strain at break ranging from 1000 to 2100%. During tensile testing, irreversible deformation and reorganization of the hard blocks occur, resulting in a significant amount of tensile set. These well-defined polymers proved to be superior compared to a less-defined analogue having a polydisperse hard block.

Oleo chemicals as additives in paints and varnishes, etc: Part 2

Gelation that can occur when copper or aluminium bronze powder is permitted to stand in nitrocellulose lacquer can be prevented by the addition of below one percent of lauric acid. Butyl acetyl ricinoleate will impart highgloss, plasticity, pliability to nitro‐cellulose lacquers and impart permanence, and improves the ageing properties and low temperature flexibility to the product. Acrylic coatings of improved gloss and pattern control have been provided by the addition of methyl hydroxystearate. When barium α‐sulphostearate is added to interior or exterior paints it can produce films of improved hardness. Methyl linoleate can be employed to retard the hardening of Japanese film lacquer. Compositions with good heat stability and good thixotropic properties and which are suitable for use as a base for paints have been evolved by reacting hydrogenated castor oil with toluene di‐isocyanate and emulsifiable and polyethylene wax. The use of aluminium stearate in paints at elevated temperatures can result in films of high opacity, good build, sag resistance, heavy pigmented tolerance and good sealing properties. Myristic acid‐based alkyd aryl ketones have been utilised to impart lustre to wooden surfaces, and stearic acid terminated polyamide/polyimide for coatings for electrical insulators of magnetic wire have been applied to give improved lustre. Diethylene glycol esters of dilinoleic acid can be used to produce non‐drip paints, as can ethylene diamine bis hydroxystearate, and glyceryl trihydroxystearate. Hydrogenated castor oil is useable in the making of thixotropic agents applicable to paints have been prepared from the material, plus oligomers of hydroxystearic acid/ethylenediamine/sebacic acid polymers. Ethyl linoleate and ethyl linoleate have been used as penetrants in anti‐corrosive paints based upon alkyd resins. Aluminium stearate can prevent excess penetration by paints of surfaces. Bis (hydroxymethyl) propanediol oleate has found use in alkyd resins derivative coatings with butylated melamine resins‐hardening materials to give pinhole resistant coatings. Butyl stearate is a good low temperature plasticiser for paints. Butyl acetyl ricinoleate imparts good plate release and cold crack resistance to leather lacquers, and provides good handle and excellent low temperature flexibility to coated fabrics on thick unsupported sheetings.

Current Trends in Fluoroelastomer Development

Abstract Recent advances in the automotive, petroleum, and energy-related industries have created applications for high-performance elastomers, which often require chemically resistant elastomers with improved high-temperature operating capability. Fluoroelastomers are uniquely capable of withstanding high temperatures in conjunction with aggressive chemicals, fuels, and lubricants. While a number of reviews concerning fluoroelastomers have been published in the last three years, this paper will concentrate on recent developments that have improved fluoroelastomers to meet the requirements of new high-performance applications. Three types of fluorine-containing elastomers—fluorocarbon, fluorosilicone, and fluoroalkoxyphosphazene (phosphonitrilic)—are commercially available. The fluorocarbon elastomers have the highest fluorine content, with general grades having between 53 and 70% fluorine. The high fluorine content of these specialty elastomers imparts exceptional resistance to attack by fuels, oils, and corrosive chemicals. The excellent resistance to high-temperature aging for extended periods of time results in a temperature use range of −46 to 320°C. Fluoro-carbon elastomers are produced in the United States by 3M (“Fluorel” Brand fluoroelastomer) and Du Pont (“Viton” Brand fluoroelastomer) and outside the United States by Montedison (Italy, “Technoflon” Brand fluoroelastomer), Daikin (Japan, “Daiel” Brand fluoroelastomer), and Asahi Glass (Japan, “Aflas” Brand elastomer, a copolymer of tetrafluoroethylene and propylene). Fluorosilicone and fluoroalkoxyphosphazene elastomers contain 30–40% fluorine. Although the fluorine content of these elastomers is less than that of fluorocarbon elastomers, it is high enough to provide moderate chemical resistance to many fluids. The flexible nature of the heteroatoms of the polymer chain backbone in fluorosilicone and fluoroalkoxyphosphazene elastomers results in excellent low-temperature flexibility, giving them a temperature use range of −54 to 230°C. Fluorosilicone elastomers are produced by Dow Corning (“Silastic”) and General Electric (“FSE”), while fluoroalkoxyphosphazene elastomers are produced by Firestone (“PNF”). This paper is a discussion of developments in fluorocarbon elastomer technology that have led to successful use in demanding applications which require high-performance elastomeric parts. Typical properties of fluorocarbon elastomers and improved properties resulting from cure system development and variations in the fluorine content of this type of elastomer will be presented. Applications for fluorocarbon elastomers in the automotive, petroleum, and energy-related industries will be illustrated.