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A compact and versatile tensile apparatus for polymer materials is designed and fabricated. Three distinct stretching modes are developed: constant speed, cyclic, and sinusoidal, with adjustable speeds ranging from 0.001 to 120 mm/s. To capture the true strain of the central region, a high-speed camera has been integrated into the apparatus. The temperature of the sample chamber is controlled by flowing air, enabling a homogeneous temperature in the range of RT ∼200 °C. The apparatus is particularly suitable for a synchrotron beamline. The structural evolution of natural rubber during sinusoidal stretching is investigated by in situ wide-angle x-ray scattering. Scattering patterns, force, clamp position, and sample images are saved simultaneously during stretching. Notably, the results reveal a sinusoidal variation in the crystallinity of crosslinked natural rubber when a sinusoidal strain was applied to the sample. The integration of advanced measurement techniques and controlled experimental conditions ensures the acquisition of reliable and accurate data, providing valuable insights into the structural evolution of materials under dynamic deformation conditions. [ABSTRACT FROM AUTHOR]

Polyamide 6 (PA6) and stabilized PA6 with two different thermal stabilizers, (ie, metal salts CuI/KI and hindered amine KYN818 [l,3-benzendicarboxamide,N, N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)]) were separately prepared by melt blending and then aged for different time. The effects of aging temperature and aging time on crystallization behaviors of PA6 and stabilized PA6 were systematically investigated by differential scanning calorimetry and X-ray diffraction. The variations of melting temperature, crystallinity and 2[theta] values suggest that aging under high temperature will accelerate the formation of crystals initially and then the degradation of molecular chains. The yellowness index and maximum decomposition temperature of stabilized PA6 are higher than that of PA6, which is dominated by different aging mechanisms and properties of stabilizers. In addition, the viscosity of all systems is increased at the preliminary stage, which is caused by the crosslinking network and the post-polycondensation. The results of dynamic mechanical analysis showed that the glass transition temperature ([T.sub.g]) decreases because the degradation of molecular chains during the aging process. Moreover, the carbonyl index for stabilized PA6 is lower than PA6, indicating the degradation is hindered by stabilizers. A comparison of the stabilization performance between CuI/KI and KYN818 was investigated to differentiate the long-term stabilizing efficiency. KEYWORDS hindered amine, metal salts, physical properties, polyamide 6, thermal-oxidative aging, 1 | INTRODUCTION Polycaprolactam (polyamide 6, PA6) is an important engineering thermoplastic which is widely used in the automotive, aerospace, and other industrial fields due to its excellent mechanical properties, [...]

Lightweight foam made of poly(ether‐b‐amide) (PEBA) elastomer has been widely used in sport shoes due to its superior rebounding and supporting properties. Novel PEBA with polyamide 1012 as hard segments and poly(tetramethylene oxide) (PTMO) as soft segments was foamed by supercritical CO2. The influence of foaming process parameters, that is saturation temperature, pressure on the morphology of cellular structure was systematically studied by scanning electron microscopy (SEM) and wide‐angle x‐ray diffraction (WAXD). By controlling the viscoelastic behavior of PEBA at certain temperatures and pressures, foams with low density and energy loss coefficient can be fabricated. The cell density of 4.5 × 109 cells/cm3 and expansion ratio of 16.0 of the foams can be obtained respectively. Cyclic compression performance of foams was systematically studied. For the foams with the highest expansion ratio, the energy loss coefficient of 11.9% in the first cycle and 3.5% after equilibrium were observed, which were less than those of former reported PEBA foams. The relationship between the Young's modulus and expansion ratio is in line with the Gibson–Ashby relationship. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A disulfide‐based poly(ether‐b‐amide) copolymer with rapid self‐healing capability under moderate conditions was synthesized from 4,4'‐dithiodibutyric acid (DTDBA), isophorondiamine (IPDA) and poly(tetramethylene oxide) (PTMO) based on a two‐step method. The incorporation of IPDA with asymmetric structure and substantial steric hindrance not only effectively decreased the number of regular H‐bonds, but also inhibited the crystallization of polyamide segments, imparting the synthesized poly(ether‐b‐amide) copolymer with an amorphous structural feature. Based on the coordination of segmental diffusion and recombination of disulfide bonds and hydrogen bonds, the scratches and damaged mechanical properties of PEBADS‐I611 could be completely self‐healed after healing at 40 °C for only 11 min and 3 h, respectively. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of surface properties of nanoparticles (NPs) on the crystallization behavior of nanocomposite, three kinds of silica (SiO2) NPs are dispersed in isotactic polypropylene (iPP) matrix by solution blending method. Specifically, the poor compatibility between inorganic bare SiO2 NPs and organic PP matrix triggers the formation of aggregates and induces the fractionated crystallization with two crystallization peaks at higher particle loading (Φ), i.e., main crystallization peak (MCP) and low temperature crystallization peak (LCP, always located at 124.0 °C). Once short PP chains (0.9 × 104 g mol−1) are grafted onto the surface of SiO2 NPs, the nanocomposites with all Φ only exhibit a single MCP which is attributed to the strong interfacial interaction. With the increase of grafting chain length (9 × 104 g mol−1), the more stretched conformation of grafting chains can provide numerous heterogeneous nucleation sites and significantly accelerate the crystallization rate of PP chains near the surface of SiO2 NPs, which lead to the formation of an extra high temperature crystallization peak (HCP, almost kept constant at 133.0 °C). The occurrence of various crystallization peaks implies that the surface properties of nanoparticles play a vital role in the nucleation ability of nanoparticles. [ABSTRACT FROM AUTHOR]

Conventional polymers have typically been used in the packaging of various electronic devices; however, due to the inherent electrically insulating properties these materials fail to dissipate static charges. To address this issue, novel poly(ether-b-amide) (PEBA) segmented copolymers consisting of uniform rigid oxalamide and flexible polyethylene glycol (PEG) were synthesized via melt polycondensation. The influence of PEG molecular weight and the spacer length separating two oxalamide units on the condensed structure, mechanical performance, and antistatic properties was systematically investigated. Fourier-transform infrared (FTIR) demonstrated strongly hydrogen bonded and highly ordered oxalamide hard segments with the degree of ordering between 71 and 85 % even at low levels. Mechanical behavior results showed that segmented copolymers have an obvious yield point, an elastic modulus between 20 and 30 MPa, and strain at break exceeding 2000 %. Meanwhile, such copolymers possessed low surface resistivity, as low as 107 Ω, which is significantly less than that of commercial antistatic additives. The antistatic effect of PEBA on polyamide 6 (PA6) was also investigated, revealing that when the content reached 30 wt%, the surface resistivity of the alloys decreased from 1013 Ω to 1011 Ω and remained stable after 40 days, even after water washing treatment. Overall, these findings illustrate that the newly synthesized PEBA copolymers demonstrate outstanding long-term antistatic properties and provide valuable insights for the development of polyether-based multiblock copolymer antistatic agents. [ABSTRACT FROM AUTHOR]

Trans‐1,4‐polyisoprene (TPI) is a typical polymorphic polymer with two crystal modifications. The transition between two crystal modifications (α to β) occurs during stretching. The underlying mechanism is still under debate. In this work, the effects of crosslinking and strain rates on the crystal transition are studied. The TPI, which mainly contains α crystal (α−TPI), is crosslinked by γ‐ray radiation. The results show that crystalline morphology does not change after radiation. The melting temperature and yield stress of crosslinked α−TPI decrease with the irradiation dose. The structural evolution is studied by in situ wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. During stretching, the content of β crystal (Xβ) of crosslinked α−TPI increases in the strain‐hardening region. The Xβ is lower in the sample with a higher radiation dose under the same strain. On the other hand, with increasing strain rate, the Xβ of the crosslinked sample exhibits a non‐monotonic variation. A parallel mechanical model consisting of amorphous and crystal fibrils is proposed to explain the experimental observations. [ABSTRACT FROM AUTHOR]

The high crystallinity and fast crystallization rate of polypropylene (PP) often result in severe warpage of final parts prepared by means of material extrusion additive manufacturing (MEAM). In this work, the effect of bed temperature (Tb) and nozzle temperature (Tn) on the dimensional accuracy and mechanical property of MEAM‐printed PP copolymer parts was investigated. It is found that raising Tb and Tn could significantly reduce the warpage of PP parts by regulating the crystallization behavior of PP. Specially, the amount of γ‐crystal grows obviously while the total crystallinity remains unchanged, as Tb or Tn increases. Moreover, the more the content of γ‐crystal, the lower the warpage height of PP samples is. Hence, a close correlation between the content of γ‐crystal and part deformation of MEAM‐printed PP parts is successfully established. This is mainly related to the large rigidity of γ‐crystal, which significantly reduces the volume shrinkage of PP during MEAM process. Besides, the raise of Tb or Tn also enhances the tensile strength, modulus and the elongation at break of PP parts. This wok provides an effective and convenient method for the manufacture of PP parts with good dimensional accuracy and excellent mechanical properties by means of MEAM techniques. [ABSTRACT FROM AUTHOR]