Analysis of the Foaming Window for Thermoplastic Polyurethane with Different Hard Segment Contents

Santiago‐Calvo, Mercedes; Naji, Haneen Zuhair; Bernardo, Victoria; León, Judith Martín‐de; Saiani, Alberto; Villafañe, Fernando; Rodríguez‐Pérez, Miguel Ángel

doi:10.3390/polym13183143

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…The lower temperature of 36.8 °C originates from the polyol soft segment, whereas the 80.7 °C corresponds to the HS (reaction of chain-extender and diisocyanate). Furthermore, the HS degree of crystallinity ( X c ) of the TPUs (TPU-4 to TPU-8) has been determined according to eq , where Δ H m is the melting enthalpy measured for each TPU and Δ H 100% is the melting enthalpy for 100% crystalline TPU, which was taken as 155 J/g in this study X C ( % ) = normalΔ H m normalΔ H 100 % × 100 …”

Section: Resultsmentioning

confidence: 99%

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Rajput,

Forman,

Halloran

et al. 2023

Macromolecules

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The utilization of bio-based materials for polymer production poses a challenge to both the industrial and academic sectors due to the availability and production costs of the necessary raw materials. Diisocyanates necessary for polyurethane synthesis have posed a particular challenge, given the paucity of natural diamine precursors for traditional phosgenation. We recently developed a phosgene-free flow chemistry methodology that allows for the safe, efficient, and scalable preparation of diisocyanates from naturally produced diacids. This chemistry broadens the potential for the development of renewable diisocyanates for a broad variety of applications. Here, we expand upon this work by demonstrating the scaled production of a panel of bio-based linear, aliphatic diisocyanates, with chain lengths ranging from four to eight carbons in good yields of 57–81% and high purity (∼97%). These are applied to the synthesis of thermoplastic polyurethanes (TPUs) containing up to a 100% renewable carbon content. TPUs formulated using shorter carbon-chained diisocyanates displayed a higher tensile strength compared to those formulated using longer chains. Ready access to diisocyanates of varying chain length affords the ability to tailor TPU properties through careful selection of the diisocyanate, polyol, and chain extender, offering hard and soft TPUs for multiple end-use applications.

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Section: Resultsmentioning

confidence: 99%

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Rajput,

Forman,

Halloran

et al. 2023

Macromolecules

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“…This observed result is due to the presence of graphene in the sample. 46,47 As graphene is just surface-deposited, no noticeable changes in the crystallization peak are observed. 48 The thermal stability of neat and foam samples and the samples with and without graphene is shown in Figure S4c,d.…”

Section: Resultsmentioning

confidence: 99%

Facile Fabrication of Highly Sensitive Thermoplastic Polyurethane Sensors with Surface- and Interface-Impregnated 3D Conductive Networks

Ponnan

Zheng

Laroui

et al. 2022

ACS Appl. Mater. Interfaces

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This research aims to develop a practical, scalable, and highly conductive flexible 3D printed piezoresistive sensor with low filler content. Here, we introduced a fused deposition modeling 3D printing combined in situ spray-coating technique to develop a conductive sensor in a single shot. The graphene suspension is sprayed over each layer during the 3D printing of the sensor, which helps develop a conductive network on the surface and at the interface of the printed system. Graphene deposited on the overall surface is often affected by nanoparticle delamination and loses its function over time. To avoid this, the prepared samples are subjected to foaming. The foaming process created a low-mass-density sensor by forming a microcellular structure, and the surface-deposited graphene is embedded well on the TPU surface. The method followed in this work reveals a stable and connected conduction path with excellent electrical resistance and resistance against harsh conditions (exposure to organic solvents). Besides, the compression sensor withstood its sensitivity over a severe compressive strain of 80% and showed a GF of 1.82 and a sensitivity of 2.316 kPa–1. The conductive network path varied based on the infill pattern, affecting its electrical sensitivity. The wiggle pattern shows good resistance; under stretching, the pattern generated a higher current and showed a delayed conductive path disconnection than other patterns. Thus, the embedded graphene/TPU conductive sensors show good stability and promising sensitivity. Furthermore, the developed sensor is used to monitor human motion and actions.

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“…This behavior is known for TPU-based polymers and blends which have a T m around this temperature. [47][48][49] Interestingly, around this temperature, the transition from PTC to NTC effect was observed. It can be assumed that above the melting temperature, a reorganization (re-agglomeration) of the carbon filler occurs, which results in an NTC effect.…”

Section: Piezo-and Thermoresistive Response Of Resistive Sensor Fibersmentioning

confidence: 99%

A Prosthetic Hand with Integrated Sensing Elements for Selective Detection of Mechanical and Thermal Stimuli

Georgopoulou

Eckey

Clemens

2023

Advanced Intelligent Systems

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Flexible electronics have gained popularity because of their capability to combine softness and functionality. Soft resistive sensors are susceptible to mechanical stimuli and detecting temperature selectively remains a challenge. In this study, soft flexible thermistors are developed for detecting temperature changes based on the positive temperature coefficient (PTC) effect, selectively. By thermomechanical analysis and differential scanning calorimetry, it is observed that thermoplastic elastomers with higher thermal expansion and semicrystalline morphology result in a sensitive thermistor response. To achieve a high sensitivity in temperature and low sensitivity in the detection of mechanical stimulus, a low‐carbon filler content is required. The opposite trend is seen for the piezoresistive sensors for mechanical strain detection. Both sensory material types are compatible with thermoplastic material extrusion‐based additive manufacturing. The method is used for the fabrication of the sensing elements and an open‐source prosthetic hand. The strain sensor detects the bending of the fingers and the temperature sensor detects the temperature when in contact with a heated surface, successfully. In addition, the temperature sensor is used as a tactile sensor to detect contact with a non‐heated surface. Combining selective multisensory capabilities will significantly affect the future development of sensorized prosthetic devices and wearable electronics.

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Analysis of the Foaming Window for Thermoplastic Polyurethane with Different Hard Segment Contents

Cited by 5 publications

References 21 publications

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Facile Fabrication of Highly Sensitive Thermoplastic Polyurethane Sensors with Surface- and Interface-Impregnated 3D Conductive Networks

A Prosthetic Hand with Integrated Sensing Elements for Selective Detection of Mechanical and Thermal Stimuli

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