Showing papers by "Liangbin Li published in 2017"
TL;DR: The first measurement of the tau lepton polarization P-tau(D*) in the decay (B) over bar -> D* tau(-) (v) over b (tau) as well as a new measurement of the ratio of the branching fractions was reported in this paper.
Abstract: We report the first measurement of the tau lepton polarization P-tau(D*) in the decay (B) over bar -> D* tau(-) (v) over bar (tau) as well as a newmeasurement of the ratio of the branching fractions R(D*) = B((B) over bar -> D* tau(-) (v) over bar (tau)) / B((B) over bar -> D* l(-) (v) over bar (l)), where l(-) denotes an electron or a muon, and the tau is reconstructed in the modes tau(-) -> pi(-) v(tau) and tau(-) -> rho(-) v(tau). We use the full data sample of 772 x 10(6) B (B) over bar pairs recorded with the Belle detector at the (KEKB) over bar electron-positron collider. Our results, P-tau(D*) = -0.38 +/- 0.51 (stat)(-0.16)(+0.21) (syst) and R(D*) = 0.270 +/- 0.035 (stat)(- 0.025)(+0.028) (syst), are consistent with the theoretical predictions of the standard model.
374 citations
TL;DR: The result is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.
Abstract: We present a measurement of angular observables and a test of lepton flavor universality in the B -> K(+)l(+)l(-) decay, where l is either e or mu. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb(-1) containing 772 x 10(6) B (B) over bar pairs, collected at the Upsilon(4S) resonance with the Belle detector at the asymmetric-energy e(+)e(-) collider KEKB. The result is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6 sigma.
338 citations
TL;DR: Tough cellulose hydrogels possessing sensitively mechano-responsive behavior could be utilized as a dynamic light switch and a soft sensor to accurately detect small external force, respectively in a novel pathway to construct tough and mechanoresponsive hydrogel via a green conversion of natural polysaccharide.
Abstract: Deformation-driven alignment of macromolecules or nanofibers leading to anisotropy is a challenge in functional soft materials. Here, tough cellulose hydrogels that exhibited deformation-induced anisotropy are fabricated by reacting cellulose with a small amount of epichlorohydrin (EPI) in LiOH/urea solution and subsequent treating with dilute acid. The loosely cross-linked network that was obtained via chemical cross-linking of cellulose with EPI as a large framework maintained the elasticity of hydrogels, whereas nanofibers produced by the acid treatment formed physical cross-linked networks through hydrogen bonds which could efficiently dissipated mechanical energy. Meanwhile, the nanofibers could further aggregate to form submicrobundles and participate in the formation of frameworks during the acid treatment. Under deformation, the nanofibers and submicrobundles in the physical networks synchronize easily to align with the large framework, generating the rapidly responsive birefringence behaviors with highly stable colors. Thus, the cellulose hydrogels possessing sensitively mechano-responsive behavior could be utilized as a dynamic light switch and a soft sensor to accurately detect small external force, respectively. This work opens a novel pathway to construct tough and mechanoresponsive hydrogels via a green conversion of natural polysaccharide.
85 citations
TL;DR: In this paper, temperature effects on deformation behaviors of extracted ultrahigh molecular weight polyethylene (UHMWPE) precursor fibers are studied with the in situ synchrotron radiation wide-angle X-ray scattering technique (WAXS) during tensile deformation at temperatures from 25 to 130 °C.
Abstract: Temperature effects on deformation behaviors of extracted ultrahigh molecular weight polyethylene (UHMWPE) precursor fibers are studied with the in situ synchrotron radiation wide-angle X-ray scattering technique (WAXS) during tensile deformation at temperatures from 25 to 130 °C. The structural and mechanical evolution behaviors during tensile deformation can be divided into four temperature regions with boundaries located at temperatures of αI and αII relaxations and the onset of melting, respectively, which reveal that the deformation behaviors of polymer crystals are determined by the interplay between intrinsic structural dynamic or chains mobility and external stress field. Irrespective of temperature, yield and strain-softening proceed via partial melting while crystal slip via cutting crystal planes occurs in the strain-hardening zone. Finally we construct morphological diagrams containing crystallinity, crystal size, and orientation in temperature–strain space, which may serve as a roadmap for UH...
53 citations
TL;DR: In this paper, three distinct features of the structure evolution are observed in temperature space, which can be described with three different deformation models, namely amorphization, crystalline block slip and melt recrystallization, respectively.
52 citations
TL;DR: Wang et al. as discussed by the authors employed in situ synchrotron radiation X-ray nanocomputed tomography (Nano-CT) technique with high spatial resolution (64 nm) to study the structural evolution of silica nanofiller in silicone rubber matrix at different strains.
Abstract: Adding silica nanofiller in silicone rubber can toughen the matrix 3 orders in terms of fracture energy, which is far larger than most other nanofiller–rubber systems. To unveil the astonishing toughening mechanism, we employ in situ synchrotron radiation X-ray nanocomputed tomography (Nano-CT) technique with high spatial resolution (64 nm) to study the structural evolution of silica nanofiller in silicone rubber matrix at different strains. The imaging results show that silica nanofiller forms three-dimensional connected network, which couples with silicone chain network to construct a double-network structure. Stress-induced phase separation between silica nanofiller and silicone polymer chain networks is observed during tensile deformation. Unexpectedly, though the spatial position and morphology of nanofiller network changes greatly at large strains, the connectivity of nanofiller network shows negligible reduction. This indicates that nanofiller network undergoes destruction and reconstruction simult...
45 citations
TL;DR: In this article, the authors explored the simultaneous effects of pressure and flow on β-crystal formation in isotactic polypropylene (iPP) mixed with β-nucleating agent (β-NA) when a flow field exists simultaneously.
Abstract: Using a pressuring and shearing device (PSD), we explored the simultaneous effects of pressure and flow on β-crystal formation. Interestingly, pressure plays a versatile role in β-crystal formation in isotactic polypropylene (iPP) mixed with β-nucleating agent (β-NA) when a flow field exists simultaneously. At a low pressure (5 MPa), a mass of β-crystals can be obtained over the entire range of applied shear rates (0.0–24.0 s–1). As the pressure increases (50–100 MPa), a weak shear flow (3.2 s–1) can profoundly suppress the β-crystal formation. When elevating the pressure to 150 MPa, β-crystals cannot be generated. The pressure and flow window to produce β-crystals in iPP mixed with β-NA were successfully summarized for the first time. The diversified β-crystal formation behaviors in iPP mixed with β-NA under the simultaneous effects of pressure and shear flow were well elucidated by combining classical nucleation theory and the growth of different crystalline phases. Our current work lays a solid foundat...
42 citations
TL;DR: The first observation of the radiative charm decay D^{0}→ρ′0}γ and the first search for CP violation in decays D′0→ρ⩽γ, ϕγ, and K[over ¯]^{*0}(892)γ are reported.
Abstract: We report the first observation of the radiative charm decay D-0 -> rho(0)gamma and the first search for CP violation in decays D-0 -> rho(0)gamma, phi gamma, and (K) over bar (*0)(892)gamma, using a data sample of 943 fb(-1) collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The branching fraction is measured to be B(D-0 -> rho(0)gamma) = (1.77 +/- 0.30 +/- 0.07) x 10(-5), where the first uncertainty is statistical and the second is systematic. The obtained CP asymmetries A(CP)(D-0 ->rho(0)gamma) = +0.056 +/- 0.152 +/- 0.006, A(CP)(D-0 -> phi gamma) = -0.094 +/- 0.066 +/- 0.001, and A(CP)(D-0 -> (K) over bar (*0) gamma = -0.003 +/- 0.020 +/- 0.000 are consistent with no CP violation. We also present an improved measurement of the branching fractions B(D-0 -> phi gamma) = (2.76 +/- 0.19 +/- 0.10) x 10(-5) and B(D-0 -> (K) over bar (*0) gamma = (4.66 +/- 0.21 +/- 0.21) x 10(-4).
36 citations
TL;DR: In this paper, the sequence and coupling of intra-and interchain orderings in flow-induced crystallization (FIC) of partially cross-linked isotactic polypropylene (iPP) is studied with in situ Fourier transform infrared spectroscopy (FTIR) and synchrotron radiation X-ray scattering techniques, which reveal that multiscale structural intermediates emerge prior to the onset of crystallization.
Abstract: The sequence and coupling of intra- and interchain orderings in flow-induced crystallization (FIC) of partially cross-linked isotactic polypropylene (iPP) is studied with in situ Fourier transform infrared spectroscopy (FTIR) and synchrotron radiation X-ray scattering techniques, which reveal that multiscale structural intermediates emerge prior to the onset of crystallization. Upon imposing flow, intrachain conformational ordering or coil–helix transition (CHT) occurs first, which is directly correlated with external stress. As helical content is built up at large strain, density fluctuation happens, and sufficient long helices may result in orientation ordering before FIC. The results demonstrate that stress induced intrachain CHT is the essential structural intermediate in FIC, which can be further coupled with interchain orientation and density providing either helical content or length meets the criterions for the phase transitions. We propose that coupling among external stress, intrachain conformat...
34 citations
TL;DR: Results are significantly more precise than previous measurements available for this mode, and the A_{CP} measurement is consistent with the standard model expectation.
Abstract: We report a study of the decay D-0 -> (KSKS0)-K-0 using 921 fb(-1) of data collected at or near the (sic)(4S) and (sic)(5S) resonances with the Belle detector at the KEKB asymmetric energy e(+)e(-) collider. The measured time-integrated CP asymmetry is A(CP)(D-0 -> (KSKS0)-K-0) = (-0.02 +/- 1.53 +/- 0.02 +/- 0.17)%, and the branching fraction is B(D-0 -> (KSKS0)-K-0) = (1.321 +/- 0.023 +/- 0.036 +/- 0.044) x 10(-4), where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode (D-0 -> K-S(0)pi(0)). These results are significantly more precise than previous measurements available for this mode. The A(CP) measurement is consistent with the standard model expectation.
31 citations
TL;DR: In this paper, the authors demonstrated that a UHMWPE with a highly linear structure and low entanglements synthesized by a single active site Ziegler-Natta catalyst can be melt injection molded without the aid of any additives and, more strikingly, structurally manipulated by means of an intensive shear flow during the packing stage of injection molding.
TL;DR: A morphological transition from a flow-induced network to shish is observed by SAXS with increasing extension temperature from below to above the melting point of Form II, which supports the idea that flow alters the obtained crystal size and its thermodynamic stability.
Abstract: Structural and morphological transitions of flow-induced crystallization (FIC) in poly(1-butene) (PB-1) melt have been studied by combining extensional rheology and in situ synchrotron radiation ultrafast wide- and small-angle X-ray scattering (WAXD/SAXS) measurements. Unexpectedly, metastable Form III is crystallized directly from the PB-1 melt by high-speed extension, which has a short lifetime of several tens of milliseconds and manifests the thermodynamic and kinetic competition among Form III, Form II and melt under flow. Relative crystallinity evolution of Form II after extension reveals a crystal melting dominated process within the observation time of 120 s even under high supercooling. This is opposite to the common case of FIC but supports the idea that flow alters the obtained crystal size and its thermodynamic stability. Additionally, a morphological transition from a flow-induced network to shish is observed by SAXS with increasing extension temperature from below to above the melting point of Form II. With above observations, we construct nonequilibrium structural and morphological diagrams of FIC in strain rate-temperature space, which may guide the industrial processing of the PB-1 material.
TL;DR: In this article, the shape descriptor OCB was introduced to differentiate hexagonal and orthorhombic clusters from melt, and it was shown that coupling between conformational and inter-chain rotational orderings results in the formation of hexagonal clusters first, which is dynamic in nature.
Abstract: Homogeneous nucleation process of polyethylene (PE) is studied with full-atom molecular dynamic simulation. To account the complex shape with low symmetry and the peculiar intra-chain conformational order of polymer, we introduce a shape descriptor OCB coupling conformational order and inter-chain rotational symmetry, which is able to differentiate hexagonal and orthorhombic clusters from melt. With the shape descriptor OCB, we find that coupling between conformational and inter-chain rotational orderings results in the formation of hexagonal clusters first, which is dynamic in nature. Whilst nucleation of orthorhombic structure occurs inside of hexagonal clusters later, which proceeds via the coalescence of neighboring hexagonal clusters rather than standard stepwise growth process. This demonstrates that nucleation of PE crystal is a two-step process with the assistance of OCB order, which is different from early models for polymer crystallization but similar with that proposed for spherical 'atoms' like colloid and metal.
TL;DR: The first evidence for isospin violation in B→K^{*}γ and the first measurement of the difference of CP asymmetries are reported, which are the most precise to date for charged and neutral B meson decays.
Abstract: We report the first evidence for isospin violation in B -> K*gamma and the first measurement of the difference of CP asymmetries between B+->.K*(+)gamma and B-0 -> K-*0 gamma. This analysis is based on the data sample containing 772 x 10(6)BB pairs that was collected with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We find evidence for the isospin violation with a significance of 3.1 sigma, Delta(0+) = [+6.2 +/- 1.5(stat) +/- 0.6(syst) +/- 1.2(f (+-)/f(00))] %, where the third uncertainty is due to the uncertainty on the fraction of B+B- to (BB0)-B-0 production in gamma(4S) decays. The measured value is consistent with predictions of the standard model. The result for the difference of CP asymmetries is Delta A(CP) = [+2.4 +/- 2.8(stat) +/- 0.5(syst)] %, consistent with zero. The measured branching fractions and CP asymmetries for charged and neutral B meson decays are the most precise to date. We also calculate the ratio of branching fractions of B-0 -> K-*0 gamma to B-s(0) -> phi gamma.
TL;DR: The results demonstrate that the FIC of PE proceeds via a multi-stage ordering process, during which coupling occurs among stress, intra-chain conformation, and inter-chain orientation and density orderings.
Abstract: Non-equilibrium molecular dynamics simulations have been performed to study the molecular mechanism of flow-induced crystallization (FIC) of polyethylene (PE). The end-to-end distance of chain Rete and the content of trans conformation Ctrans are extracted out to represent intra-chain conformation ordering at whole chain and segment levels, respectively, while orientation correlation function P, density ρ, and bond orientational order parameter Q4 are taken to depict inter-chain orders. Imposing the extension induces the intra-chain conformational ordering to occur first, which further couples with the inter-chain order and results in the formation of hexagonal packing. Further increasing strain leads to the appearance of orthorhombic order. The results demonstrate that the FIC of PE proceeds via a multi-stage ordering process, during which coupling occurs among stress, intra-chain conformation, and inter-chain orientation and density orderings. Analyzing the flow-induced energy evolution unveils that not only entropy but also energy plays an important role in the FIC.
TL;DR: In this article, an upper bound of 4.42 +/- 0.05 (stat)+/- 0.12 (syst)+/-0.16 (norm))% was established for the Cabibbo-suppressed decay Lambda(+)(c) -> pi p(0) in e(+) e(-) collisions using a data sample corresponding to an integrated luminosity of 915 fb(-1).
Abstract: We have searched for the Cabibbo-suppressed decay Lambda(+)(c) -> pi p(0) in e(+) e(-) collisions using a data sample corresponding to an integrated luminosity of 915 fb(-1). The data were collected by the Belle experiment at the KEKB e(+) e(-) asymmetric-energy collider running at or near the (4S) and (5S) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B(Lambda(+)(c) -> phi p(0)) K+ K- p pi(0) decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B(Lambda(+)(c) ->. K+ K- p pi(0))(NR) phi p. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B(Lambda(+)(c) -> P-s(+) pi(0)) x B(P-s(+) -> phi p) K- pi(+) p pi(0);the result is B(Lambda(+)(c) -> K- pi(+) p pi(0)) = (4.42 +/- 0.05(stat)+/- 0.12(syst)+/- 0.16(norm))%, which is the most precise measurement to date.
TL;DR: In this article, the authors discovered a new class of polymers known as stress-memory materials, which is not guaranteed by the shape-memory effect (SME), but instead manifests itself as a unique behavior of shape memory polymers possessing the extra characteristic of an enthalpy switch.
Abstract: Smart materials for stress applications are both sought after in the industry and are also of academic interest. Motivated by the unexpected drastic differences in the cyclic thermomechanical responses between Tg and Tm shape memory polyurethanes (SMPU), we discovered a new class of polymers known as stress-memory materials. We revealed that stress memory is not guaranteed by the shape-memory effect (SME), but instead manifests itself as a unique behaviour of shape memory polymers (SMPs) possessing the extra characteristic of an enthalpy switch. Stemming from our findings on a rubbery switch, memory stress is realized from the entropic elasticity within rubbery chains of the SMP soft segments. Enthalpy in a Tm-switch, crystal switch, can modulate this entropic energy leading to stress-memory, whereas the Tg-switch is a second-order thermodynamic transition. Thus, a model needs two basic elements: entropy domination for spring elasticity and enthalpy modulation of entropy as a switch for the stress-memory polymer networks. This forms a fundamental platform for materials development in energy, smart devices, artificial muscles, biological and physical massage systems with polymers, and high entropy ceramics and metals.
TL;DR: In this article, a protocol of two-step extension is proposed to investigate the early stage of flow-induced crystallization (FIC) in supercooled isotactic polypropylene melt at 138°C.
Abstract: With a combination of extensional rheology and in-situ small-angle X-ray scattering measurements, the protocol of two-step extension is proposed to investigate the early stage of flow-induced crystallization (FIC) in supercooled isotactic polypropylene melt at 138 °C. After both step strains, the crystallization half-time presents a nonmonotonic dependence on the interval time between two extensional operations, based on which three different stages of structural evolution are defined. In stage I, both nucleation and chain relaxation occur, which enhances the crystallization rate but reduces the final lamellar crystal orientation. In this stage, each part of the melt is considered to have approximately the same dynamics to respond homogeneously to the second extension and thus the system is still dominated by a chain-network. When entering into stage II, the sparse large-scaled crystal is formed to construct a heterogeneous crystal-network superimposed on the chain-network, which decelerates the second ex...
TL;DR: A new method for detecting trace amounts of environmental organic pollutants by dynamically tuning the SERS enhancement in the semiwet testing state is proposed.
TL;DR: In this paper, the shape descriptor OCB was introduced to differentiate hexagonal and orthorhombic clusters from melt, and it was shown that coupling between conformational and inter-chain rotational orderings results in the formation of hexagonal clusters first, which is dynamic in nature.
Abstract: Homogeneous nucleation process of polyethylene (PE) is studied with full-atom molecular dynamic simulation. To account the complex shape with low symmetry and the peculiar intra-chain conformational order of polymer, we introduce a shape descriptor OCB coupling conformational order and inter-chain rotational symmetry, which is able to differentiate hexagonal and orthorhombic clusters from melt. With the shape descriptor OCB, we find that coupling between conformational and inter-chain rotational orderings results in the formation of hexagonal clusters first, which is dynamic in nature. Whilst nucleation of orthorhombic structure occurs inside of hexagonal clusters later, which proceeds via the coalescence of neighboring hexagonal clusters rather than standard stepwise growth process. This demonstrates that nucleation of PE crystal is a two-step process with the assistance of OCB order, which is different from early models for polymer crystallization but similar with that proposed for spherical 'atoms' like colloid and metal.
TL;DR: In this paper, a setup of blown film machine combined with in situ synchrotron radiation X-ray diffraction measurements and infrared temperature testing is reported to study the structure evolution of polymers during film blowing.
Abstract: A setup of blown film machine combined with in situ synchrotron radiation X-ray diffraction measurements and infrared temperature testing is reported to study the structure evolution of polymers during film blowing. Two homemade auto-lifters are constructed and placed under the blown machine at each end of the beamline platform which move up and down with a speed of 0.05 mm/s bearing the 200 kg weight machine. Therefore, structure development and temperature changes as a function of position on the film bubble can be obtained. The blown film machine is customized to be conveniently installed with precise servo motors and can adjust the processing parameters in a wide range. Meanwhile, the air ring has been redesigned in order to track the structure information of the film bubble immediately after the melt being extruded out from the die exit. Polyethylene (PE) is selected as a model system to verify the feasibility of the apparatus and the in situ experimental techniques. Combining structure information provided by the WAXD and SAXS and the actual temperature obtained from the infrared probe, a full roadmap of structure development during film blowing is constructed and it is helpful to explore the molecular mechanism of structure evolution behind the film blowing processing, which is expected to lead to a better understanding of the physics in polymer processing.
TL;DR: In this paper, the same-hemisphere dihadron cross sections are obtained from a 655 fb(-1) data sample collected at or near the Y (4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.
Abstract: The inclusive cross sections for dihadrons of charged pions and kaons (e(+)e(-) -> hhX) in electron-positron annihilation are reported. They are obtained as a function of the total fractional energy and invariant mass for any di-hadron combination in the same hemisphere as defined by the thrust event-shape variable and its axis. Since same-hemisphere dihadrons can be assumed to originate predominantly from the same initial parton, di-hadron fragmentation functions are probed. These di-hadron fragmentation functions are needed as an unpolarized baseline in order to quantitatively understand related spindependent measurements in other processes and to apply them to the extraction of quark transversity distribution functions in the nucleon. The di- hadron cross sections are obtained from a 655 fb(-1) data sample collected at or near the Y (4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.
TL;DR: In this article, the memory effect of metastable polyisoprene (TPI) was investigated with its thermodynamically stable α-TPI as reference, and the memory temperature of β-TPIs was found to be 20 °C higher than its equilibrium melting point (78 °C).
Abstract: The memory effect of metastable β form crystals of trans-1,4-polyisoprene (TPI) is investigated with its thermodynamically stable α-TPI as reference. Unexpectedly, β-TPI exhibits a stronger memory effect over α-TPI. The memory temperature of β-TPI can be 20 °C higher than its equilibrium melting point (78 °C), while α-TPI has lost memory below the equilibrium melting point (87 °C). Moreover, the ordered structures in β-TPI memorized melt accelerate spherulite growth, and the growth rate depends on melting time, similar to previous mesomorphic isotactic polypropylene studies, implying metastable phase may have universal memory effects: wide memory temperature range, crystal nucleation and growth accelerating. The higher memory temperature of metastable phase may be from weak entropic difference with isotropic melt, which cannot overcome the barrier from entanglements as thermodynamically stable phase, leading to slow relaxation. This discovery can regulate crystalline morphologies of polymers by controlling the locations of different form crystals.
TL;DR: In this paper, the branching fraction and CP violation asymmetry in the decay B-0 -> pi(0)pi(0), using a data sample of 752 x 10(6) B (B) over bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB e(+)e(-) collider.
Abstract: We measure the branching fraction and CP violation asymmetry in the decay B-0 -> pi(0)pi(0), using a data sample of 752 x 10(6) B (B) over bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB e(+)e(-) collider. The obtained branching fraction and direct CP asymmetry are B(B -> pi(0)pi(0)) = [1.31 +/- 0.19(stat) +/- 0.19(syst)] x 10(-6) and A(CP) = +0.14 +/- 0.36(stat) +/- 0.10(syst), respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belle's earlier measurements of B-0 -> pi(+)pi(-) and B-+/- -> pi(+/-)pi(0) to exclude the CP-violating parameter phi(2) from the range 15.5 degrees < phi(2) < 75.0 degrees at 95% confidence level.
TL;DR: In this paper, the gamma(4S) resonance with the Belle detector at the KEKB asymmetric energy e(+)e(-) collider was studied, and the hadronic transitions between bottomonium states were investigated.
Abstract: We study hadronic transitions between bottomonium states using 496 fb(-1) data collected at the gamma(4S) resonance with the Belle detector at the KEKB asymmetric energy e(+)e(-) collider. We measure: B(gamma(4S) -> pi(+)pi(-)gamma(1S)) = (8.2 +/- 0.5(stat.)+/- 0.4(syst.)) x 10(-5), B(gamma(4S) -> pi(+)pi(-)gamma(2S)) = (7.9 +/- 1.0(stat.)+/- 0.4(syst.)) x 10(-5), and B(gamma(4S) -> eta gamma(1S)) = (1.70 +/- 0.23(stat.) +/- 0.08(syst.)) x 10(-4). We measure the ratio of branching fractions R=B(gamma(4S) -> eta gamma(1S))/B(gamma(4S) -> pi(+)pi(-)gamma(1S)) = 2.07 +/- 0.30(stat.)+/- 0.11(syst.). We search for the decay gamma(1(3)D(1,2)) -> eta gamma(1S), but do not find significant evidence for such a transition. We also measure the initial state radiation production cross sections of the gamma(2S,3S) resonances and we find values compatible with the expected ones. Finally, the analysis of the gamma(4S) -> pi(+)pi(-)gamma(1S) events shows indications for a resonant contribution due to the f(0)(980) meson.
TL;DR: In this paper, the modulus of biaxially oriented polypropylene (BOPP) films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films.
Abstract: Young’s modulus of biaxially oriented polypropylene (BOPP) films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films It was found that the modulus of films was decreased by about 69% as the content of polyethylene (PE) added into polypropylene (PP) reached 30% Also, increasing draw temperature can induce lower stress level during stretching, which may lead to the formation of crystals with low orientation level and thus decreased modulus of films Based on laboratory study, BOPP films produced on commercial line were studied by differential scanning calorimetry (DSC), wide and small-angle X-ray scattering (WAXS, SAXS) with varying contents of PE SAXS results show that the crystals are oriented in both machine direction (MD) and transverse direction (TD), and the crystals are more oriented in TD than MD according to the WAXS results for all films Also, the orientation parameter of crystal along TD increases from 068 to 083 as the contents of PE increase from 0% to 25% Meanwhile, the modulus of films in MD declines with increase of PE contents generally, improving the film softness Orientation of crystals is thus an effective structure parameter to adjust the film softness The relationship of processing-structure-property is also established
TL;DR: In this paper, the effects of mechanical energy and thermal effect on micropore nucleation and growth in oriented high density polyethylene (HDPE) film were investigated.
TL;DR: In this paper, the stabilization mechanism of micropore embryos formed during cold stretching in high-density polyethylene films, samples are subsequently subjected to temperature elevation and strain holding at 25 °C, respectively.
Abstract: Aiming to reveal the stabilization mechanism of micropore embryos formed during cold stretching in high-density polyethylene films, samples are subsequently subjected to temperature elevation and strain holding at 25 °C, respectively. The corresponding structure evolution is tracked. It is found that after strain holding at 25 °C and subsequent strain recovery, inhomogeneously distributed cavities are produced, most of which can be healed as temperature is elevated to 110 °C. Consequently, only a small number of nonevenly distributed micropores are formed during the subsequent hot stretching. While for thermal pathway, micropores and fibrils can be formed as temperature is elevated. The hot stretching membrane exhibits uniformly distributed micropores and the micropores are well interconnected, indicating that micropores stabilized via temperature elevation are permanent and homogeneous. The results reveal different stabilization mechanisms of micropores via the thermal and mechanical pathways with regard to the distribution as well as the amount of permanent micropores.
TL;DR: The current study can guide real processing to fabricate high-performance polymer products with oriented crystals by understanding the necessary condition of forming oriented crystals and the expression of the specific work of flow, w (T,P).
Abstract: Flow-induced oriented crystals have attracted considerable attention because they significantly increase stiffness and strength of polymer products. Naturally, understanding the necessary condition of forming oriented crystals is of importance for both industry and polymer physics. Following the concept of specific work of flow proposed by Mykhaylyk and co-workers, the expression of the specific work of flow, w (T,P), was carefully summarized and verified that when w (T,P) is above a critical specific work of flow, w c(T,P) = (1.7 ± 0.7) × 107 J m−3, oriented crystals in isotactic polypropylene can be induced by flow at pressures (50, 100, and 150 MPa) and at a undercooling of 65 K. The influences of pressure on w c(T,P) stem from two facets: one is the influence on the melt viscosity (the Barus law), and the other one is the influence on the equilibrium melting temperature (the Clapeyron equation). The current study can guide real processing to fabricate high-performance polymer products with oriented crystals.
TL;DR: In this paper, bimetallic catalysts are used to support silylchromate and vanadium-oxide-based catalysts on silica or alumina, zirconia and titania-modified silica.
Abstract: Bimodal ultra-high-molecular-weight polyethylene (UHMWPE)/high-density polyethylene (HDPE) in-reactor blends (IRBs) are produced by the bimetallic catalysts, which are synthesized through co-supporting silylchromate and vanadium-oxide-based catalysts on silica or alumina, zirconia and titania-modified silica. After support modification, the activities of the catalysts for ethylene polymerization are substantially enhanced. The IRBs produced by the modified catalysts also contain more UHMWPE and low-molecular-weight polyethylene (LMWPE) fractions, and have much broader molecular weight distribution (MWD). The homogeneous nature of the IRBs is preliminarily confirmed by the differential scanning calorimetry melting curves, showing unique melting peak in both nascent and recrystallized states. The rheological results reflect that the viscosity of the IRBs is reduced more or less when compared with UHMWPE. The distinct elastic dominance of the IRBs is also observed, implying the UHMWPE characteristics in the IRBs. In addition, the intimate mixing of the IRBs is further verified by the similar slopes of Han curves for the polyethylene (PE) samples. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3404–3412