Polyamides, Plastics

Palmer, Robert

doi:10.1002/0471238961.1612011916011213.a01

Cited by 14 publications

(8 citation statements)

References 2 publications

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“…As a result of their high chemical stability and conformational diversity, 36,37 polyamides have established themselves as the material of choice for a myriad of applications, ranging from fibers (e.g., nylon) for clothing to covering and fitting structures in automotive and electronics. 38 Nonetheless, opposed to the widely applied dynamic transesterification reaction, 19,39−42 the number of reported efficient exchange reactions based on transamidation is quite limited, for example, for its use as dynamic covalent peptides. 43,44 This should be ascribed to the inherent stability of the amide bond, which implies that exchange or dissociation does not readily occur.…”

Section: ■ Introductionmentioning

confidence: 99%

Reprocessing of Covalent Adaptable Polyamide Networks through Internal Catalysis and Ring-Size Effects

et al. 2021

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Here, we report the introduction of internally catalyzed amide bonds to obtain covalent adaptable polyamide networks that rely on the dissociation equilibrium between dicarboxamides and imides. While amide bonds are usually considered to be robust and thermally stable, the present study shows that their dynamic character can be activated by a smart choice of available building blocks without the addition of any external catalyst or other additives. Hence, a range of polyamide-based dynamic networks with variable mechanical and viscoelastic properties have been obtained in a systematic study, using a straightforward curing process of dibasic ester and amine compounds. Since the dissociation process involves a cyclic imide formation, the correlation between ring size and the thermomechanical viscosity profile was studied for five- to seven-membered ring intermediates, depending on the chosen dibasic ester monomer. This resulted in a marked temperature response with activation energies in the range of 116–197 kJ mol–1, yielding a sharp transition between elastic and viscous behavior. Moreover, the ease and versatility of this chemistry platform were demonstrated by selecting a variety of amines, resulting in densely cross-linked dynamic networks with T g values ranging from −20 to 110 °C. With this approach, it is possible to design amorphous polyamide networks with an acute temperature response, allowing for good reprocessability and, simultaneously, high resistance to irreversible deformation at elevated temperatures.

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Section: ■ Introductionmentioning

confidence: 99%

Reprocessing of Covalent Adaptable Polyamide Networks through Internal Catalysis and Ring-Size Effects

et al. 2021

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“…In PA 6.6, the repeating unit has a center of symmetry: the amide linkages easily align to form hydrogen bonds when the fully extended zigzag‐like chains are arranged in the same or parallel mode and the chain axis lies oblique to the lamellar surface (α‐form), leading to a triclinic unit cell 1, 4. On the other hand, for PA 6, with an odd number of CH 2 , the amide groups are in the correct position to form linear H‐bonds only if the fully extended chains stack in an alternating or staggered shear (α‐form) or when the carbonyl groups are tilted by 30° relative to the chain axis, resulting in the formation of pleated sheets (γ‐form) 3, 7–9…”

Section: Introductionmentioning

confidence: 99%

Long‐Aliphatic‐Segment Polyamides: Salt Preparation and Subsequent Anhydrous Polymerization

Boussia

Vouyiouka

Porfiris

et al. 2010

Macro Materials & Eng

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Long‐aliphatic‐segment polyamides were prepared based on hexamethylenediamine and α,ω‐(CH2)x biosynthetic diacids (x = 10, 11, 12). The pertinent monomers (salts) were isolated as solids, thoroughly characterized for the first time, and then submitted to an anhydrous melt prepolymerization technique. The obtained prepolymers exhibited $\overline {M} _{{\rm n}} $ in the range of 5 100–11 800 g · mol−1, and the molecular weight was further increased by up to 55% through solid‐state finishing. The suggested overall polyamidation cycle was conducted at short melt‐reaction times, so as to avoid any thermal degradation, and was proved efficient, indicating similar reactants polymerizability independently of the methylene content.magnified image

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“…The elastic properties of PA66-GF30 and rubber were defined as typical values [ 31 , 32 ]. The piezoelectric properties for piezoelectric units (PZT-5H) were defined according to [ 27 ].…”

Section: Methodsmentioning

confidence: 99%

Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions

Liu

Yang

et al. 2021

Materials

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The piezoelectric energy harvester (PEH) is a device for recycling wasted mechanical energy from pavements. To evaluate energy collecting efficiency of PEHs with various piezoelectric unit distributions, finite element (FE) models of the PEHs were developed in this study. The PEH was a square of 30 cm × 30 cm with 7 cm in thickness, which was designed according to the contact area between tire and pavement. Within the PEHs, piezoelectric ceramics (PZT-5H) were used as the core piezoelectric units in the PEHs. A total of three distributions of the piezoelectric units were considered, which were 3 × 3, 3 × 4, and 4 × 4, respectively. For each distribution, two diameters of the piezoelectric units were considered to investigate the influence of the cross section area. The electrical potential, total electrical energy and maximum von Mises stress were compared based on the computational results. Due to the non-uniformity of the stress distribution in PEHs, more electrical energy can be generated by more distributions and smaller diameters of the piezoelectric units; meanwhile, more piezoelectric unit distributions cause a higher electrical potential difference between the edge and center positions. For the same distribution, the piezoelectric units with smaller diameter produce higher electrical potential and energy, but also induce higher stress concentration in the piezoelectric units near the edge.

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Polyamides, Plastics

Cited by 14 publications

References 2 publications

Reprocessing of Covalent Adaptable Polyamide Networks through Internal Catalysis and Ring-Size Effects

Reprocessing of Covalent Adaptable Polyamide Networks through Internal Catalysis and Ring-Size Effects

Long‐Aliphatic‐Segment Polyamides: Salt Preparation and Subsequent Anhydrous Polymerization

Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions

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