Herein, we report copolymerizations of ethylene (E) and ortho‐/meta‐/para‐fluorostyrenes (SF=oFS/mFS/pFS) by using quinolyl methylene fluorenyl scandium complex (Flu‐CH2‐Qu)Sc(CH2SiMe3)2. The ...copolymerizations proceed in a controlled fashion to afford copolymers composed of “soft” ethylene‐fluorostyurene (E–SF) random segments (Tg=−22.2–5.1 °C) and “hard” crystalline ethylene–ethylene (E–E) segments (Tm=42.3–130.2 °C). The copolymers behave like thermoplastic elastomers at room temperature by showing high stress values up to 39.5 MPa under elongation‐at‐break above 774 % with elastic recovery over 75 %. The excellent mechanical properties are mainly attributed to the microphase separation of the nanoscale crystalline E–E domain from the amorphous E–SF copolymer matrix proved by AFM, WAXD and SAXS. The mechanism investigation by the density functional theory (DFT) simulation reveals that the steric bulky and electron‐withdrawing ligand of the catalytic precursor prefers E propagation to generate long E–E segments, while the incorporation of SF is thermodynamic control.
A brand‐new functionalized thermoplastic elastomer with excellent toughness and efficient elastic recovery has been successfully achieved through the direct copolymerization of E and ortho‐/meta‐/para‐fluorostyrene (oFS/mFS/pFS) using the scandium complex. The DFT simulation reveals that the bulky and electron‐withdrawing ligand of the catalytic precursor prefers E propagation to generate long E–E segments.
Display omitted
A precompression pressure optimization strategy using in-die elastic recovery was developed to effectively address tablet lamination caused by air entrapment. This strategy involves ...exacerbating the air entrapment issue using high tableting speeds and main compaction pressures and collecting in-die elastic recovery data as a function of precompression pressure. The optimized precompression pressure, which corresponds to the minimum elastic recovery, is most effective at eliminating air from the powder bed prior to the main compression. When the optimized precompression pressure was employed, intact tablets of a model blend prone to lamination due to air entrapment could be produced over a wide range of high main compaction pressures, while tablets without precompression laminated immediately after ejection at equivalent main compaction pressures. This optimization strategy is effective for addressing lamination issues due to air entrapment using precompression. An advantage of this strategy is that intact tablets are not required to identify an optimized precompression pressure since elastic recovery measurements occur in-die.
Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not ...degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-
alt
-phthalate)-
b
-poly( -decalactone)-
b
-poly(cyclohexene-
alt
-phthalate) {PE-PDL-PE}. The synthesis is accomplished using a zinc(
ii
)/magnesium(
ii
) catalyst, in a one-pot procedure where -decalactone ring-opening polymerization yielding dihydroxyl telechelic poly( -decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85-98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (
f
hard
= 0.4) and variable molar masses 40-100 kg mol
−1
; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol
−1
) and variable hard-block volume fractions (0.12 <
f
hard
< 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼−51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (
f
hard
< 0.4 and
N
> 1300) with linear stress-strain relationships, high ultimate tensile strengths (
σ
b
= 1-5 MPa), very high elongations at break (
b
= 1000-1900%) and excellent elastic recoveries (98%). There is a wide operating temperature range (−51 to +138 °C), an operable processing temperature range (+100 to +200 °C) and excellent thermal stability (
T
d,5%
∼ 300 °C). The polymers are stable in aqueous environments, at room temperature, but are hydrolyzed upon gentle heating (60 °C) and treatment with an organic acid (
para
-toluene sulfonic acid) or a common lipase (Novozyme® 51032). The new block polyesters show significant potential as sustainable thermoplastic elastomers with better properties than well-known styrenic block copolymers or polylactide-derived elastomers. The straightforward synthesis allows for other commercially available and/or bio-derived lactones, epoxides and anhydrides to be developed in the future.
A new series of block polyester thermoplastic elastomers are prepared by a one-pot procedure; they show properties competitive or better than conventional materials and can be fully degraded after use.
Snapping mechanical metamaterials have garnered significant interest in recent years because of their ability to achieve extremely large strains and shape/configuration changes or recoveries via ...elastic buckling instability. For 1D snapping 2D periodic structures with planar topological configurations, the snapping mechanisms have been deeply studied. In this article, 1D multistable cylindrical metastructures composed of a periodic arrangement of bistable snapping units with programmable nonlinear mechanical responses are presented. Theoretical analysis, finite element simulations, and experimental verifications are performed to the application for stable and reusable shape-reconfiguration/phase-transformation. Notably, the mechanical characterizations of 2D snapping 2D periodic structures and developed cylindrical configurations are also carried out. The applications for highly stretchable devices and morphable metastructures are proposed. The relationships between geometric parameters as well as the numbers of the unit cells and structure's macroscopic mechanical behavior are concluded. The study significantly expands the ability of snapping metamaterials and opens avenues for the adaptive morphable surfaces as demonstrated by the design of a smart responsive skin that significantly enhances the deformability and programmability.
Nanosprings
In article number 2108419, Ziyao Zhou, Houbing Huang, Yong Peng, Ming Liu, and co‐workers report freestanding, epitaxial, ferroelectric nanosprings with superscalability, which provide ...insights regarding mechanical behaviors and domain evolution of ferroelectric oxide springs. The excellent scalability originates from the continuous ferroelastic domain structures, resulting from twisting under coexisting axial and shear strains. The superstretchable, elastic, and recoverable oxide spring provides a novel platform to flexible electronics.
This work utilizes frustrated Lewis pairs consisting of tethered bis‐organophosphorus superbases and a bulky organoaluminum to furnish the highly efficient synthesis of well‐defined triblock ...copolymers via one‐step block copolymerization of lignin‐based syringyl methacrylate and n‐butyl acrylate, through di‐initiation and compounded sequence control. The resulting thermoplastic elastomers (TPEs) exhibit microphase separation and much superior mechanical properties (elongation at break up to 2091 %, tensile strength up to 11.5 MPa, and elastic recovery up to 95 % after 10 cycles) to those of methyl methacrylate‐based TPEs. More impressively, lignin‐based tri‐BCPs can maintain TPEs properties up to 180 °C, exhibit high transparency and nearly 100 % UV shield, suggesting potential applications in temperature‐resistant and optical devices.
Di‐initiating frustrated Lewis pairs promoted compounded sequence control to achieve one‐step synthesis of the well‐defined triblock copolymers. The resulting thermoplastic elastomers (TPEs) exhibit much superior mechanical properties to those of methyl methacrylate‐based TPEs and maintain TPEs properties at temperatures as high as 180 °C.
Johanson (1965) developed a one-dimensional model for the stress acting on the powder in between the rolls of a roller compactor. Limited work has been performed regarding estimation of inlet stress; ...a parameter required for the estimation of ribbon density in a roller compactor. Due to the difficulty in the design and implementation of stress measurement systems, measurement of inlet stress is difficult experimentally. Therefore, a Discrete Element Method (DEM) based approach is proposed to get the inlet conditions which are used in the Johanson model to predict the ribbon density.
The results indicate that the inlet stress and the corresponding pre-consolidated density obtained from DEM simulations were different for different process parameters. The combined methodology of using output from DEM simulations as an input condition for Johanson model yields a good prediction of the ribbon density with the inclusion of elastic expansion ratio (ribbon thickness/roll gap).
Display omitted
•Combined DEM and Johanson model based methodology is applied for the first-time.•Ribbon density calculated including elastic recovery shows decent accuracy.•Inlet pressure and pre-consolidated density are defined at inception of slip zone.•Compressibility constant is observed as invariant with punch speed and sample mass.
•The fatigue performances of multiple representative modified asphalts are evaluated.•Three testing methods, namely time sweep, elastic recovery and LAS are compared.•Failure criterion should be ...carefully selected regarding modified asphalts.•LAS shows a better correlation with elastic recovery at increasing strain levels.•Elastic recovery may be a promising indicator of asphalt/mixture fatigue life.
The fatigue cracking due to the repeated traffic loading is one of the main distresses that reduces the performance and service life of the asphalt pavements. The asphalt phase of asphalt mixture is the most critical for resisting fatigue damage, and thus it must be carefully evaluated for fatigue performance. Previous studies mainly focused on a limited range of asphalt materials while the applications of multiple new kinds of modified asphalts have surged in recent years. This study aimed to evaluate the fatigue resistance of 7 representative modified asphalts, including the linear SBS polymer modified asphalt, crumb rubber modified asphalt, terminal blend (TB) rubberized asphalt, EVA modified asphalt, Rock asphalt modified asphalt and bio oil modified asphalt. Three tests (times sweep test, LAS test and Elastic recovery test) and four different failure criterions are evaluated. Results suggested that elastomeric modified asphalts show the best fatigue performance, followed by non-elastomeric modified asphalts and plain asphalt. Elastomeric modified asphalts appear to show better fatigue resistance at higher strain level conditions. Also, the fatigue life of LAS test shows a good correlation with the elastic recovery, and the correlation improves with increasing strain levels. This suggests that elastic recovery could be a promising indicator for asphalt/mixture fatigue life characterization.
Display omitted
Roll compaction/dry granulation is a widely used granulation method in the pharmaceutical industry. The simulation of the process is of great interest, especially in the early phase ...of formulation development of solid dosage forms. The hybrid modeling approach allows to predict the roll compaction process parameters to produce ribbons with a desired solid fraction. Based on the process parameters, compacts (ribblets) of the same solid fraction are produced on a single punch press. So far, the prediction accuracy for the solid fraction of the ribbons was not satisfactory. It was found that the lack in prediction accuracy was due to the elastic recovery, which was not considered in the model. In this study, the fast in-die and the slow out-of-die elastic recovery of different excipients with varying compaction properties were investigated. A method was established to compensate for the elastic recovery of compacts in roll compaction simulation and to improve the prediction accuracy of the solid fraction considerably. The results were successfully implemented into the model through an additional learning step. Moreover, the findings were transferred to the mimicking of an API containing formulation. By modeling, it was possible to accurately predict the process settings to obtain ribbons with the desired solid fraction using only a small amount of material.
The microstructural and mechanical properties of β-type Ti74-xMoxNb26 (x = 0, 2, 4, 6, and 8 at.%) biomedical alloys with low elastic modulus were investigated. The experimental results show that the ...Ti74Nb26 alloy is composed of the β and α’’ phases; however, the Ti74-xMoxNb26 (x = 2, 4, 6, and 8 at.%) alloys are composed of only a single β phase. Based on the stress–strain curve, the Ti66Mo8Nb26 alloy with the large yield strength and elastic energy can consider as biomedical and functional materials. The Mo addition not only stabilizes the β phase of the alloys, but also increases the strength, and retains the ductility of the Ti74Nb26 alloy. Based on nanoindentation technique, the reduced elastic modulus (Er) of Ti66Mo8Nb26 alloy with the high hardness (H) is 54.5 GPa, which is 1.5–5.5 times of that of human bone (10–30 GPa), and is the smaller than that of commercial Ti–6Al–4V biomedical alloy (120 GPa). The wear resistance (H/Er) and anti-wear capability (H3/Er2) ratios of Ti66Mo8Nb26 alloy are 0.0591 and 0.0112 GPa, respectively, indicating that the good wear resistance and anti-wear capability, or long service life as biomedical materials, compared with those of CP-Ti alloy. In addition, the elastic recovery values of the Ti–Mo–Nb alloys are larger than that of CP-Ti alloy (20.4%), which indicates that the Ti–Mo–Nb alloys exhibit the higher impact resistance.
•Ti–Mo–Nb alloys are mainly composed of β-Ti and α′′-Ti phases.•Ti66Mo8Nb26 alloy has the large yield strength and elastic energy.•Elastic modulus (54.5 GPa) of Ti66Mo8Nb26 alloy is close to that of human bone (10–30 GPa).•Large H/Er and H3/Er2 values indicate good wear resistance and anti-wear ability.
PDF
