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2015 Volume 33 Issue 10
2015, 33(10): 1351-1358
doi: 10.1007/s10118-015-1684-1
Abstract:
The thermal quenching behaviors of the temperature sensitivity paints (TSP) composed of europium(III) thenoyltrifluoroacetonate (EuTTA) and Eu-phenanthrene complex (Eu-2) in polystyrene (PS), polymethylmethacrylate (PMMA) and epoxy resin (EP) were investigated. It is found that both the emission intensity and temperature sensitivity were not only affected by the luminescence probes, but also by the polymer matrix. The interaction between probes and matrix results in the alteration of both the non-radiation decay rate and the activation energy of the non-radiative process for the thermal quenching process, i.e. larger activation energy of the non-radiative process shows higher temperature sensitivity and less emission intensity. Therefore, it was confirmed that the temperature sensitivity and luminescent intensity of TSP depended not only on the luminescence probes but also on the polymer matrix.
The thermal quenching behaviors of the temperature sensitivity paints (TSP) composed of europium(III) thenoyltrifluoroacetonate (EuTTA) and Eu-phenanthrene complex (Eu-2) in polystyrene (PS), polymethylmethacrylate (PMMA) and epoxy resin (EP) were investigated. It is found that both the emission intensity and temperature sensitivity were not only affected by the luminescence probes, but also by the polymer matrix. The interaction between probes and matrix results in the alteration of both the non-radiation decay rate and the activation energy of the non-radiative process for the thermal quenching process, i.e. larger activation energy of the non-radiative process shows higher temperature sensitivity and less emission intensity. Therefore, it was confirmed that the temperature sensitivity and luminescent intensity of TSP depended not only on the luminescence probes but also on the polymer matrix.
2015, 33(10): 1359-1372
doi: 10.1007/s10118-015-1685-0
Abstract:
Polyimides (PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some epoxy resins at room temperature. These PIs can be incorporated in the absence of organic solvent into epoxy resin E51 with the loading below 2 wt% forming EP-PI composites. No phase separation is observed by SEM on cryogenically fractured surfaces of EP-PI composites. The PI can improve mechanical properties, especially impact strength. Adding 2 wt% PI-1.5W, the impact strength reaches to 55 kJ/m2 with the increase in tensile and flexural strengths by 14% and 3%, respectively. SEM analyses for the fracture surface suggest that PI reduces the crosslink density, improves the plasticity of epoxy resin and changes the mode of fracture from fragile to ductile. Moreover, the glass transition temperature of EP-PI composites was found to increase to a significant extent.
Polyimides (PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some epoxy resins at room temperature. These PIs can be incorporated in the absence of organic solvent into epoxy resin E51 with the loading below 2 wt% forming EP-PI composites. No phase separation is observed by SEM on cryogenically fractured surfaces of EP-PI composites. The PI can improve mechanical properties, especially impact strength. Adding 2 wt% PI-1.5W, the impact strength reaches to 55 kJ/m2 with the increase in tensile and flexural strengths by 14% and 3%, respectively. SEM analyses for the fracture surface suggest that PI reduces the crosslink density, improves the plasticity of epoxy resin and changes the mode of fracture from fragile to ductile. Moreover, the glass transition temperature of EP-PI composites was found to increase to a significant extent.
2015, 33(10): 1373-1379
doi: 10.1007/s10118-015-1687-y
Abstract:
The fluorescence property of bovine serum albumin was investigated in the presence of PEGs of different molecular weights. Based on our results, we propose that PEGs of different molecular weights bind to albumin in the pH 7.4 aqueous solution, but only when the polymer size is larger than the protein size, one polymer chain may bind to multiple proteins and cause the proteins to aggregate.
The fluorescence property of bovine serum albumin was investigated in the presence of PEGs of different molecular weights. Based on our results, we propose that PEGs of different molecular weights bind to albumin in the pH 7.4 aqueous solution, but only when the polymer size is larger than the protein size, one polymer chain may bind to multiple proteins and cause the proteins to aggregate.
2015, 33(10): 1380-1388
doi: 10.1007/s10118-015-1686-z
Abstract:
The diffusion and subsequent copolymerization of styrene (St)/butyl methacrylate (BMA) mixed monomers in iPP pellets to prepare copolymer nanoblends were investigated. The diffusion step was carried out at 90 ℃ for 2 h in water, and the copolymerization was initiated by the addition of BPO with the aid of a small amount of St. The diametrical distributions of both St and BMA units and their ratio St/BMA were investigated by micro FTIR. Both St and BMA can diffuse into the centres of iPP pellets. The diametrical distribution of St/BMA ratio is constant in all the copolymer blends. The copolymer composition depends on the comonomer feed ratio. The molecular weights of the copolymers were measured by GPC after extraction with tetrahydrofuran. The phase morphology of the copolymer blends was investigated by FESEM, showing the average particle sizes of less than 100 nm. DSC measurements show that the diffusion and subsequent copolymerization of St/BMA monomers only occur in the amorphous regions of iPP pellets.
The diffusion and subsequent copolymerization of styrene (St)/butyl methacrylate (BMA) mixed monomers in iPP pellets to prepare copolymer nanoblends were investigated. The diffusion step was carried out at 90 ℃ for 2 h in water, and the copolymerization was initiated by the addition of BPO with the aid of a small amount of St. The diametrical distributions of both St and BMA units and their ratio St/BMA were investigated by micro FTIR. Both St and BMA can diffuse into the centres of iPP pellets. The diametrical distribution of St/BMA ratio is constant in all the copolymer blends. The copolymer composition depends on the comonomer feed ratio. The molecular weights of the copolymers were measured by GPC after extraction with tetrahydrofuran. The phase morphology of the copolymer blends was investigated by FESEM, showing the average particle sizes of less than 100 nm. DSC measurements show that the diffusion and subsequent copolymerization of St/BMA monomers only occur in the amorphous regions of iPP pellets.
2015, 33(10): 1389-1403
doi: 10.1007/s10118-015-1696-x
Abstract:
Two novel heterogeneous nickel -diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall(s) in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PEmmol-1 Nih-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 gmol-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.
Two novel heterogeneous nickel -diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall(s) in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PEmmol-1 Nih-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 gmol-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.
2015, 33(10): 1404-1420
doi: 10.1007/s10118-015-1688-x
Abstract:
The target of the present investigation is synthesis and characterization of an amphiphilic diblock copolymer with antibacterial property. Ring opening polymerization (ROP) of -caprolactone (CL) and tetrahydrofuran (THF) was carried out under inert atmosphere by using L-cysteine as a bridging agent in the presence of stannous octoate (SO) as a catalyst. The nano silver end capped diblock copolymer was synthesized by in situ method. Thus obtained nano silver end capped L-cysteine bridged diblock copolymer was characterized by various analytical methods like Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), fluorescence spectroscopy, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and zeta potential. The antimicrobial property of the nano silver end capped diblock copolymer against e-coli was tested.
The target of the present investigation is synthesis and characterization of an amphiphilic diblock copolymer with antibacterial property. Ring opening polymerization (ROP) of -caprolactone (CL) and tetrahydrofuran (THF) was carried out under inert atmosphere by using L-cysteine as a bridging agent in the presence of stannous octoate (SO) as a catalyst. The nano silver end capped diblock copolymer was synthesized by in situ method. Thus obtained nano silver end capped L-cysteine bridged diblock copolymer was characterized by various analytical methods like Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), fluorescence spectroscopy, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and zeta potential. The antimicrobial property of the nano silver end capped diblock copolymer against e-coli was tested.
2015, 33(10): 1421-1430
doi: 10.1007/s10118-015-1700-5
Abstract:
Spherical polyelectrolyte brushes (SPBs) consisting of polystyrene (PS) core and poly(2-aminoethyl methacrylate hydrochloride) (PAEMH) shell were prepared by photo-emulsion polymerization. Au nanoparticles (Au-NPs) with controlled size and size distribution were synthesized in situ using SPBs as nanoreactors. Via layer-by-layer deposition technique on the surface of SPBs, nano-composite particles with Au/Ag-NPs bilayer and Au/Ag/Au-NPs trilayer were prepared. The structures of the as-prepared Au/Ag multilayer SPBs were characterized by UV-Vis spectroscopy, TEM, ICP-AES and DLS. The charge reversal of the nano-composite particles observed by zeta potential confirmed the success of layer-by-layer assembly. The Au/Ag-NPs bilayer nano-composite particles showed high catalytic efficiency with an apparent activation energy of about 41.2 kJ/mol in the reduction reaction of 4-nitrophenol to 4-aminophenol in the existence of sodium borohydride monitored. The catalytic activity of Au/Ag-NPs multilayer SPBs close to that of Au-NPs SPBs and much higher than that of Ag-NPs SPBs reveals its potential applications in cost-effective catalysts with high-performance.
Spherical polyelectrolyte brushes (SPBs) consisting of polystyrene (PS) core and poly(2-aminoethyl methacrylate hydrochloride) (PAEMH) shell were prepared by photo-emulsion polymerization. Au nanoparticles (Au-NPs) with controlled size and size distribution were synthesized in situ using SPBs as nanoreactors. Via layer-by-layer deposition technique on the surface of SPBs, nano-composite particles with Au/Ag-NPs bilayer and Au/Ag/Au-NPs trilayer were prepared. The structures of the as-prepared Au/Ag multilayer SPBs were characterized by UV-Vis spectroscopy, TEM, ICP-AES and DLS. The charge reversal of the nano-composite particles observed by zeta potential confirmed the success of layer-by-layer assembly. The Au/Ag-NPs bilayer nano-composite particles showed high catalytic efficiency with an apparent activation energy of about 41.2 kJ/mol in the reduction reaction of 4-nitrophenol to 4-aminophenol in the existence of sodium borohydride monitored. The catalytic activity of Au/Ag-NPs multilayer SPBs close to that of Au-NPs SPBs and much higher than that of Ag-NPs SPBs reveals its potential applications in cost-effective catalysts with high-performance.
2015, 33(10): 1431-1441
doi: 10.1007/s10118-015-1697-9
Abstract:
We describe in this work an alkyne-hydrosilylation approach to synthesize a series of novel polysiloxane sidechain LCPs attaching end-on or side-on mesogenic side groups. Their properties are characterized by NMR, FTIR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy and small-angle X-ray scattering. These obtained alkenylsilane linked novel LCPs exhibit higher glass transition temperatures and clearing points, and especially display the tendency of forming smectic phases, in strong contrast with the nematic phases of their comparative conventional alkylsilane linked analogues, which manifests more rigid features of the alkenylsilane linkages and their significant influence on the mesomorphic properties.
We describe in this work an alkyne-hydrosilylation approach to synthesize a series of novel polysiloxane sidechain LCPs attaching end-on or side-on mesogenic side groups. Their properties are characterized by NMR, FTIR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy and small-angle X-ray scattering. These obtained alkenylsilane linked novel LCPs exhibit higher glass transition temperatures and clearing points, and especially display the tendency of forming smectic phases, in strong contrast with the nematic phases of their comparative conventional alkylsilane linked analogues, which manifests more rigid features of the alkenylsilane linkages and their significant influence on the mesomorphic properties.
2015, 33(10): 1442-1452
doi: 10.1007/s10118-015-1698-8
Abstract:
Two novel monomers, 10,13-bis(4-octyl-2-thienyl)-dibenzo[a,c]phenazine (OTBP) and 10,13-bis(4-octyl-2- thienyl)-dipyrido[3,2-a:2',3'-c]phenazine (OTPP), were synthesized. Electrochemical polymerization of OTPP and OTBP were carried out in acetonitrile/dichloromethane (ACN/DCM) solvent mixture containing tetra-nbutylammoniumhexafluorophosphate (TBAPF6), and electrochromic properties of POTPP and POTBP are described. Furthermore, the effects of structural difference on electronic properties of electron acceptor units, electrochemical and electrochromic properties of two resulting polymers were examined. The results showed that the OTBP was polymerized at lower potential than OTPP, and this is because OTPP contains two more N atoms in electron acceptor unit and its electron withdrawing ability is stronger than that of OTBP. The UV-Vis-NIR spectra analysis revealed that the POTPP film has three absorption bands centered at 570 nm, 925 nm and 1581 nm, and the POTBP film has two absorptions at 566 nm and 1009 nm, respectively. The electrochromic properties indicated that the two polymer films exhibits reasonable optical contrasts and response time with low band gaps, defined as the onset of the absorption band at 570 nm for POTPP and the absorption band at 566 nm for POTBP, as 1.74 eV for POTPP and as 1.69 eV for POTBP.
Two novel monomers, 10,13-bis(4-octyl-2-thienyl)-dibenzo[a,c]phenazine (OTBP) and 10,13-bis(4-octyl-2- thienyl)-dipyrido[3,2-a:2',3'-c]phenazine (OTPP), were synthesized. Electrochemical polymerization of OTPP and OTBP were carried out in acetonitrile/dichloromethane (ACN/DCM) solvent mixture containing tetra-nbutylammoniumhexafluorophosphate (TBAPF6), and electrochromic properties of POTPP and POTBP are described. Furthermore, the effects of structural difference on electronic properties of electron acceptor units, electrochemical and electrochromic properties of two resulting polymers were examined. The results showed that the OTBP was polymerized at lower potential than OTPP, and this is because OTPP contains two more N atoms in electron acceptor unit and its electron withdrawing ability is stronger than that of OTBP. The UV-Vis-NIR spectra analysis revealed that the POTPP film has three absorption bands centered at 570 nm, 925 nm and 1581 nm, and the POTBP film has two absorptions at 566 nm and 1009 nm, respectively. The electrochromic properties indicated that the two polymer films exhibits reasonable optical contrasts and response time with low band gaps, defined as the onset of the absorption band at 570 nm for POTPP and the absorption band at 566 nm for POTBP, as 1.74 eV for POTPP and as 1.69 eV for POTBP.
2015, 33(10): 1453-1461
doi: 10.1007/s10118-015-1699-7
Abstract:
The polyamide 66 (PA66)/lanthanum acetate blends with small amounts of salt loadings ( 1 wt% of PA) have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities * and storage modulus G' of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies (tan 1), i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid (G' G''). While the viscosity followed a strong shear thinning with increasing frequency, the * and G' decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudocrosslinked network structure, which makes the glass transition temperatures (Tg) and storage modulus (E') of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.
The polyamide 66 (PA66)/lanthanum acetate blends with small amounts of salt loadings ( 1 wt% of PA) have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities * and storage modulus G' of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies (tan 1), i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid (G' G''). While the viscosity followed a strong shear thinning with increasing frequency, the * and G' decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudocrosslinked network structure, which makes the glass transition temperatures (Tg) and storage modulus (E') of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.
2015, 33(10): 1462-1469
doi: 10.1007/s10118-015-1691-2
Abstract:
pH responsive composite Janus cages of PS-silica-PEO are prepared using silica nanoparticles to crosslink two PAA contained di-block copolymers at an emulsion interface sequentially. Transverse channels are in situ created across the shell, which facilitates mass transfer. Shell is pH responsive owing to the presence of residual PAA chains tethered onto the silica nanoparticles. The Janus cages are capable to preferentially capture oil from their aqueous surroundings. The saturation absorption capacity is determined by pH and oil property. Other composite Janus cages are expected by extension the method using other copolymers and functional nanoparticles.
pH responsive composite Janus cages of PS-silica-PEO are prepared using silica nanoparticles to crosslink two PAA contained di-block copolymers at an emulsion interface sequentially. Transverse channels are in situ created across the shell, which facilitates mass transfer. Shell is pH responsive owing to the presence of residual PAA chains tethered onto the silica nanoparticles. The Janus cages are capable to preferentially capture oil from their aqueous surroundings. The saturation absorption capacity is determined by pH and oil property. Other composite Janus cages are expected by extension the method using other copolymers and functional nanoparticles.
2015, 33(10): 1470-1476
doi: 10.1007/s10118-015-1690-3
Abstract:
In this study, well-ordered gold nanoparticle array on silicon substrate was adopted as an active surface-enhanced Raman scattering substrate for detecting rhodamine B (RB), and the influence of RB morphologies on surface-enhanced Raman scattering (SERS) properties was discussed. The Au nanoparticle array was prepared by using patterned P4VP nanodomains of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymer thin films as nanoreactors which is a simple and economical approach. The results show that Raman spectra of RB on the Au nanopaticle array have much stronger intensity than those on the bare silicon substrate by detecting same RB solution. It indicates that the prepared Au nanoparticle array on silicon substrate has a significant Raman enhancement for RB. Interestingly, the Raman intensity of RB from its ethanol solution is much stronger than that from its aqueous solution due to the special morphologies of RB formed in their ethanol solutions. This work provides an effective approach to prepare highly sensitive and stable surface-enhanced Raman scattering substrate.
In this study, well-ordered gold nanoparticle array on silicon substrate was adopted as an active surface-enhanced Raman scattering substrate for detecting rhodamine B (RB), and the influence of RB morphologies on surface-enhanced Raman scattering (SERS) properties was discussed. The Au nanoparticle array was prepared by using patterned P4VP nanodomains of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymer thin films as nanoreactors which is a simple and economical approach. The results show that Raman spectra of RB on the Au nanopaticle array have much stronger intensity than those on the bare silicon substrate by detecting same RB solution. It indicates that the prepared Au nanoparticle array on silicon substrate has a significant Raman enhancement for RB. Interestingly, the Raman intensity of RB from its ethanol solution is much stronger than that from its aqueous solution due to the special morphologies of RB formed in their ethanol solutions. This work provides an effective approach to prepare highly sensitive and stable surface-enhanced Raman scattering substrate.
2015, 33(10): 1477-1490
doi: 10.1007/s10118-015-1692-1
Abstract:
The multilayered polypropylene (PP) and poly(ethylene-co-octene) (POE) sheets were prepared by the microlayered co-extrusion system. The essential work of fracture (EWF) and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the wp, there is no obvious variation in the multilayered blends with low POE content (6.79%), however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends (16.57%). Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.
The multilayered polypropylene (PP) and poly(ethylene-co-octene) (POE) sheets were prepared by the microlayered co-extrusion system. The essential work of fracture (EWF) and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the wp, there is no obvious variation in the multilayered blends with low POE content (6.79%), however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends (16.57%). Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.
