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2014 Volume 32 Issue 4
2014, 32(4): 385-394
doi: 10.1007/s10118-014-1418-9
Abstract:
The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer (RAFT)/self-condensing vinyl polymerization (SCVP) method. Several redox initiating chemicals such as Cu(Ⅲ)/―CONH2, Ce(Ⅳ)/―CONH2 and Ce(Ⅳ)/―OH were chosen to increase the free radical generating rate, and the chain transfer agent (CTA) was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, value and the degree of branching of polymers (DB) obtained from 1H-NMR spectra and multi detector size exclusion chromatography (MDSEC) suggested the acquiring of hyperbranced polyacrylamides with Cu(Ⅲ)/―CONH2 and Ce(Ⅳ)/―CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly(N-hydroxymethyl acrylamide) (PNHAM) with higher DB value (0.48) proved that using Ce(Ⅳ)/―OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index () value and the DB was also studied.
The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer (RAFT)/self-condensing vinyl polymerization (SCVP) method. Several redox initiating chemicals such as Cu(Ⅲ)/―CONH2, Ce(Ⅳ)/―CONH2 and Ce(Ⅳ)/―OH were chosen to increase the free radical generating rate, and the chain transfer agent (CTA) was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, value and the degree of branching of polymers (DB) obtained from 1H-NMR spectra and multi detector size exclusion chromatography (MDSEC) suggested the acquiring of hyperbranced polyacrylamides with Cu(Ⅲ)/―CONH2 and Ce(Ⅳ)/―CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly(N-hydroxymethyl acrylamide) (PNHAM) with higher DB value (0.48) proved that using Ce(Ⅳ)/―OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index () value and the DB was also studied.
2014, 32(4): 395-401
doi: 10.1007/s10118-014-1415-z
Abstract:
Stable aqueous amino-grafted silicon nanoparticles (SiNPs-NH2) were prepared via one-pot solution method. By grafting amino groups on the particle surface, the dispersion of SiNPs in water became very stable and clear aqueous solutions could be obtained. By incorporating SiNPs-NH2 into the hole transport layer of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT:PSS), the performance of polymer solar cells composed of poly[2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as active layer can be improved. SiNPs-NH2 are dispersed uniformly in the PEDOT:PSS solution and help form morphologies with small-sized domains in the PEDOT:PSS film. SiNPs-NH2 serve as screens between conducting polymer PEDOT and ionomer PSS to improve the phase separation and charge transport of the hole transport layer. As a result, the sheet resistance of PEDOT:PSS thin films is decreased from (935)105 to (133)105 /□. The power conversion efficiency (PCE) of polymer solar cells was thus improved by 9.8% for devices fabricated with PEDOT:PSS containing 1 wt% of SiNPs-NH2, compared with the devices fabricated by original PEDOT:PSS.
Stable aqueous amino-grafted silicon nanoparticles (SiNPs-NH2) were prepared via one-pot solution method. By grafting amino groups on the particle surface, the dispersion of SiNPs in water became very stable and clear aqueous solutions could be obtained. By incorporating SiNPs-NH2 into the hole transport layer of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT:PSS), the performance of polymer solar cells composed of poly[2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as active layer can be improved. SiNPs-NH2 are dispersed uniformly in the PEDOT:PSS solution and help form morphologies with small-sized domains in the PEDOT:PSS film. SiNPs-NH2 serve as screens between conducting polymer PEDOT and ionomer PSS to improve the phase separation and charge transport of the hole transport layer. As a result, the sheet resistance of PEDOT:PSS thin films is decreased from (935)105 to (133)105 /□. The power conversion efficiency (PCE) of polymer solar cells was thus improved by 9.8% for devices fabricated with PEDOT:PSS containing 1 wt% of SiNPs-NH2, compared with the devices fabricated by original PEDOT:PSS.
2014, 32(4): 402-410
doi: 10.1007/s10118-014-1416-y
Abstract:
The results of molecular dynamics (MD) simulations on transport process of CO2 and CH4 gases in poly(ether-b-amide) (PEBAX)/nanosilica membranes are discussed. The diffusion coefficients for CH4 and CO2 gases at 6 cases with different amounts of nanosilica loading in the simulation boxes are presented. The results show that diffusion coefficients for CO2 gas in all cases are larger than those for the CH4 one. Moreover 10% nanosilica loading case shows maximum effects on diffusion coefficients and improves them by more than 68% and 157% for CO2 and CH4 gases, respectively. Additionally, the results of 3-D Cartesian trajectories and displacements curves are presented and the jumping attempt of CO2 is significantly more than that of CH4. Due to the rubbery state of PEBAX membranes in ambient temperature, the results confirm that channel lifetimes are very short and then back diffusion is not observed for this polymer.
The results of molecular dynamics (MD) simulations on transport process of CO2 and CH4 gases in poly(ether-b-amide) (PEBAX)/nanosilica membranes are discussed. The diffusion coefficients for CH4 and CO2 gases at 6 cases with different amounts of nanosilica loading in the simulation boxes are presented. The results show that diffusion coefficients for CO2 gas in all cases are larger than those for the CH4 one. Moreover 10% nanosilica loading case shows maximum effects on diffusion coefficients and improves them by more than 68% and 157% for CO2 and CH4 gases, respectively. Additionally, the results of 3-D Cartesian trajectories and displacements curves are presented and the jumping attempt of CO2 is significantly more than that of CH4. Due to the rubbery state of PEBAX membranes in ambient temperature, the results confirm that channel lifetimes are very short and then back diffusion is not observed for this polymer.
2014, 32(4): 411-423
doi: 10.1007/s10118-014-1400-6
Abstract:
The phase structure and morphology of polypropylene (iPP) blends with poly(decamethylene sebacamide (polyamide 1010, PA1010) and the part-compatible alloys (iPP/PA1010/iPP-g-MAH) are investigated by Rayleigh scattering, i.e. small angle light scattering (SALS). The structure parameters of SALS, i.e. correlation distance, ac and average chord lengths,l, are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.
The phase structure and morphology of polypropylene (iPP) blends with poly(decamethylene sebacamide (polyamide 1010, PA1010) and the part-compatible alloys (iPP/PA1010/iPP-g-MAH) are investigated by Rayleigh scattering, i.e. small angle light scattering (SALS). The structure parameters of SALS, i.e. correlation distance, ac and average chord lengths,l, are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.
2014, 32(4): 424-431
doi: 10.1007/s10118-014-1413-1
Abstract:
Triphase polyimide nanocomposite films were fabricated using barium titanate (BaTiO3) with high dielectric constant and silver (Ag) with high conductivity as fillers. In situ method was utilized to obtain the homogeneous dispersion of nanoparticles. The in situ polymerization of polyimide precursor-poly(amic acid) was performed in the presence of BaTiO3 particles. Silver compound 1,1,1-trifluoro-2,4-pentadionato silver(Ⅰ) was added into the BaTiO3 containing poly(amic acid) solution to achieve silver nanoparticles via in situ self metallization technique. The thermally induced reduction converted silver (Ⅰ) to metallic silver with concomitant imidization of poly(amic acid) to polyimide. Both BaTiO3 and silver nanoparticles were uniformly dispersed in the polyimide substrate. The dependence of dielectric behavior on the BaTiO3 and Ag contents was studied. The incorporation of small amount of silver nanoparticles greatly increased dielectric constant of composite films.
Triphase polyimide nanocomposite films were fabricated using barium titanate (BaTiO3) with high dielectric constant and silver (Ag) with high conductivity as fillers. In situ method was utilized to obtain the homogeneous dispersion of nanoparticles. The in situ polymerization of polyimide precursor-poly(amic acid) was performed in the presence of BaTiO3 particles. Silver compound 1,1,1-trifluoro-2,4-pentadionato silver(Ⅰ) was added into the BaTiO3 containing poly(amic acid) solution to achieve silver nanoparticles via in situ self metallization technique. The thermally induced reduction converted silver (Ⅰ) to metallic silver with concomitant imidization of poly(amic acid) to polyimide. Both BaTiO3 and silver nanoparticles were uniformly dispersed in the polyimide substrate. The dependence of dielectric behavior on the BaTiO3 and Ag contents was studied. The incorporation of small amount of silver nanoparticles greatly increased dielectric constant of composite films.
2014, 32(4): 432-438
doi: 10.1007/s10118-014-1398-9
Abstract:
Nano-sized spherical polymer brushes (SPBs) consisting of both a polystyrene (PS) core and a brush shell of poly(acrylic acid) (PAA), poly(N-acrylcysteamine) (PSH), or poly(N-acrylcysteamine-co-acrylic acid) (P(SH-co-AA)), were prepared by photo-emulsion polymerization. The core-shell structure was observed by dynamic light scattering and transmission electron microscopy. Due to the strengthened Donnan effect, the PAA brush can adsorb heavy metal ions. Effects of the contact time, thickness of PAA brush and pH value on the adsorption results were investigated. Due to the coordination between the mercapto groups and heavy metal ions as well as the electrostatic interactions, SPBs with mercapto groups are capable to remove heavy metal ions selectively from aqueous solutions. The order of adsorption capacity of the heavy metal ions by SPBs with mercapto groups is: Hg2+ Au3+ Pb2+ Cu2+ Ni2+. The adsorbed heavy metal ions can be eluted from SPB by aqueous HCl solution, and the SPBs can be recovered. After three regenerations the recovered SPBs still maintain their adsorption capacity.
Nano-sized spherical polymer brushes (SPBs) consisting of both a polystyrene (PS) core and a brush shell of poly(acrylic acid) (PAA), poly(N-acrylcysteamine) (PSH), or poly(N-acrylcysteamine-co-acrylic acid) (P(SH-co-AA)), were prepared by photo-emulsion polymerization. The core-shell structure was observed by dynamic light scattering and transmission electron microscopy. Due to the strengthened Donnan effect, the PAA brush can adsorb heavy metal ions. Effects of the contact time, thickness of PAA brush and pH value on the adsorption results were investigated. Due to the coordination between the mercapto groups and heavy metal ions as well as the electrostatic interactions, SPBs with mercapto groups are capable to remove heavy metal ions selectively from aqueous solutions. The order of adsorption capacity of the heavy metal ions by SPBs with mercapto groups is: Hg2+ Au3+ Pb2+ Cu2+ Ni2+. The adsorbed heavy metal ions can be eluted from SPB by aqueous HCl solution, and the SPBs can be recovered. After three regenerations the recovered SPBs still maintain their adsorption capacity.
2014, 32(4): 439-448
doi: 10.1007/s10118-014-1419-8
Abstract:
Bacterial cellulose produced by Acetobacter xylinum has been reacted with propyleneoxide to synthesize hydroxypropyl cellulose (HPC) under different reaction conditions while diluted by toluene. The effects of mass ratio of bacterial cellulose to propyleneoxide, dilutability of toluene, reaction temperature (T) and time (t) were investigated by series of experiments. The degree of substitution (DS), hydroxypropyl content (A) and yield () were compared. The optimized product exhibited cold-water solubility and hot-water gelatinization in aqueous medium. Further study was carried out with FTIR, TGA, XRD, SEM and 13C-NMR for characterization. The water/air contact angle measurement reveals that it is a good hydrophobic material with good mechanical properties.
Bacterial cellulose produced by Acetobacter xylinum has been reacted with propyleneoxide to synthesize hydroxypropyl cellulose (HPC) under different reaction conditions while diluted by toluene. The effects of mass ratio of bacterial cellulose to propyleneoxide, dilutability of toluene, reaction temperature (T) and time (t) were investigated by series of experiments. The degree of substitution (DS), hydroxypropyl content (A) and yield () were compared. The optimized product exhibited cold-water solubility and hot-water gelatinization in aqueous medium. Further study was carried out with FTIR, TGA, XRD, SEM and 13C-NMR for characterization. The water/air contact angle measurement reveals that it is a good hydrophobic material with good mechanical properties.
2014, 32(4): 449-457
doi: 10.1007/s10118-014-1410-4
Abstract:
Polyacrylonitrile (PAN) nanofibers with average diameter of 300 nm were produced by electro-spinning. The nanofibers were stabilized at different temperatures in the range of 180-270 ℃ in several duration times and heating rates. Fourier transforms infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyzing techniques were employed to measure the extent of stabilization reaction. By all procedures, the ranges of temperature and duration time recommended were about 250-270 ℃ and 1-2 h, respectively. Increasing the activation temperature from 800 ℃ to 1200 ℃ caused porosity and pore volume development up to 60% and 0.532 cm3/g, respectively. Pore width of all samples was calculated to be about 0.7 nm confirming micro-pore structure of the produced PAN based activated carbon nanofibers. Comparing dye adsorption for different adsorbents including chitin and granular activated carbon (GAC) showed the highest efficiency for the produced activated carbon nanofibers (ACNFs).
Polyacrylonitrile (PAN) nanofibers with average diameter of 300 nm were produced by electro-spinning. The nanofibers were stabilized at different temperatures in the range of 180-270 ℃ in several duration times and heating rates. Fourier transforms infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyzing techniques were employed to measure the extent of stabilization reaction. By all procedures, the ranges of temperature and duration time recommended were about 250-270 ℃ and 1-2 h, respectively. Increasing the activation temperature from 800 ℃ to 1200 ℃ caused porosity and pore volume development up to 60% and 0.532 cm3/g, respectively. Pore width of all samples was calculated to be about 0.7 nm confirming micro-pore structure of the produced PAN based activated carbon nanofibers. Comparing dye adsorption for different adsorbents including chitin and granular activated carbon (GAC) showed the highest efficiency for the produced activated carbon nanofibers (ACNFs).
2014, 32(4): 458-466
doi: 10.1007/s10118-014-1409-x
Abstract:
A new method to prepare polysaccharide-coating type chiral stationary phases (CSPs) was developed in this work. As a typical example, naked silica gel was coated by cellulose, which was then derivatized with 3,5-dimethylbenzoyl chloride to afford cellulose tris(3,5-dimethylbenzoate)-silica gel (CTDBS) complex. The silanols on CTDBS were end-capped with 3-aminopropyltriethoxysilane to obtain CSP 1. The amino groups on CSP 1 were further end-capped with 3,5-dimethylbenzoyl chloride to give CSP 2. The silanols on CTDBS were end-capped with methyltrimethoxysilane to yield CSP 3. CSPs 1-3 were characterized by FTIR, solid-state 13C-NMR and elemental analysis. The enantioseparation abilities of CSPs 1-3 were evaluated with structurally various chiral analytes. The enantioseparation results demonstrated that the end-capping moieties on CSPs 1 and 2 significantly affected enantioseparation. In addition, the effect of the structures of chiral analytes and end-capping moieties on the retention factors and the resolutions was discussed.
A new method to prepare polysaccharide-coating type chiral stationary phases (CSPs) was developed in this work. As a typical example, naked silica gel was coated by cellulose, which was then derivatized with 3,5-dimethylbenzoyl chloride to afford cellulose tris(3,5-dimethylbenzoate)-silica gel (CTDBS) complex. The silanols on CTDBS were end-capped with 3-aminopropyltriethoxysilane to obtain CSP 1. The amino groups on CSP 1 were further end-capped with 3,5-dimethylbenzoyl chloride to give CSP 2. The silanols on CTDBS were end-capped with methyltrimethoxysilane to yield CSP 3. CSPs 1-3 were characterized by FTIR, solid-state 13C-NMR and elemental analysis. The enantioseparation abilities of CSPs 1-3 were evaluated with structurally various chiral analytes. The enantioseparation results demonstrated that the end-capping moieties on CSPs 1 and 2 significantly affected enantioseparation. In addition, the effect of the structures of chiral analytes and end-capping moieties on the retention factors and the resolutions was discussed.
2014, 32(4): 467-475
doi: 10.1007/s10118-014-1414-0
Abstract:
In this study, nanohydroxyapatite/polyurethane (nHA/PU) composites with various contents of methoxy-poly(ethylene glycol) modified nHA (0 wt%, 10 wt%, 20 wt% and 30 wt%) were prepared by solution blending process. The physicochemical properties of the composite membranes were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electronic microscopy (TEM), Differential scanning calorimetry (DSC), Thermo gravimetric analysis (TGA) and tensile tests. TEM photos of the nanocomposites showed that the nHA was uniformly dispersed in the polymer matrix. The membrane with 10 wt% nHA showed the highest tensile strength which was about 75% higher than that of the pure PU membrane. However, the tensile strength decreased when high content (above 20 wt%) fillers were added, which was still higher than that of pure PU. TGA measurements suggested that the thermal stability of the membranes was improved owing to nHA fillers. XRD and DSC results illustrated that the crystallinity of PU soft segments decreased with the increasing content of nanoparticles in the composites.
In this study, nanohydroxyapatite/polyurethane (nHA/PU) composites with various contents of methoxy-poly(ethylene glycol) modified nHA (0 wt%, 10 wt%, 20 wt% and 30 wt%) were prepared by solution blending process. The physicochemical properties of the composite membranes were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electronic microscopy (TEM), Differential scanning calorimetry (DSC), Thermo gravimetric analysis (TGA) and tensile tests. TEM photos of the nanocomposites showed that the nHA was uniformly dispersed in the polymer matrix. The membrane with 10 wt% nHA showed the highest tensile strength which was about 75% higher than that of the pure PU membrane. However, the tensile strength decreased when high content (above 20 wt%) fillers were added, which was still higher than that of pure PU. TGA measurements suggested that the thermal stability of the membranes was improved owing to nHA fillers. XRD and DSC results illustrated that the crystallinity of PU soft segments decreased with the increasing content of nanoparticles in the composites.
2014, 32(4): 488-496
doi: 10.1007/s10118-014-1420-2
Abstract:
The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly(butylene adipate) (PBA) in poly(butylene succinate) (PBS)/poly(butylene adipate) (PBS/PBA) blends were studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and atomic force microscopy (AFM). It was revealed that the polymorphism of PBA can be regulated by the blend ratio even in a non-isothermal crystallization process. The results demonstrate that high temperature favors flat-on crystals, while low temperature contributes to edge-on crystals. It was also found that the effect of blend ratio on the crystallization mechanism of PBA is well coincident with that of the crystallization temperature. The increment of PBS content in the PBS/PBA blend gives rise to more -form crystals of PBA. For those PBS/PBA blends with low PBA content, the interlamellar phase segregation of PBA makes its molecular chains so difficult to diffuse from one isolated microdomain to another that high crystallization temperature and sufficiently long crystallization time will be required if the PBA -type crystals are targeted.
The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly(butylene adipate) (PBA) in poly(butylene succinate) (PBS)/poly(butylene adipate) (PBS/PBA) blends were studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and atomic force microscopy (AFM). It was revealed that the polymorphism of PBA can be regulated by the blend ratio even in a non-isothermal crystallization process. The results demonstrate that high temperature favors flat-on crystals, while low temperature contributes to edge-on crystals. It was also found that the effect of blend ratio on the crystallization mechanism of PBA is well coincident with that of the crystallization temperature. The increment of PBS content in the PBS/PBA blend gives rise to more -form crystals of PBA. For those PBS/PBA blends with low PBA content, the interlamellar phase segregation of PBA makes its molecular chains so difficult to diffuse from one isolated microdomain to another that high crystallization temperature and sufficiently long crystallization time will be required if the PBA -type crystals are targeted.
2014, 32(4): 497-508
doi: 10.1007/s10118-014-1421-1
Abstract:
Composite biomaterials made of biodegradable polylactic acid (PLA) and bioactive magnesium (Mg) salt are developed for orthopaedic implants or metal implant coatings. The releasing of Mg salt into the biological environment benefits the bone growth, while with the releasing of Mg salt and degradation of PLA there forms a porous scaffold for tissue engineering. The size and morphology of the salt and voids are adjustable with such preparation conditions as salt content, pH of casting solution, and the solidification rate, so that we can control the salt releasing and degradation rate of PLA. Dielectric spectroscopy is used to investigate the dispersive structures of Mg salt and voids in the polymer matrix and to monitor the in situ releasing of Mg salts in the simulated body fluid (SBF). The current study provides us with an orthopedic biomaterial with controllable multi-phase structures, and a tool to investigate the in vivo behaviors of biomaterials.
Composite biomaterials made of biodegradable polylactic acid (PLA) and bioactive magnesium (Mg) salt are developed for orthopaedic implants or metal implant coatings. The releasing of Mg salt into the biological environment benefits the bone growth, while with the releasing of Mg salt and degradation of PLA there forms a porous scaffold for tissue engineering. The size and morphology of the salt and voids are adjustable with such preparation conditions as salt content, pH of casting solution, and the solidification rate, so that we can control the salt releasing and degradation rate of PLA. Dielectric spectroscopy is used to investigate the dispersive structures of Mg salt and voids in the polymer matrix and to monitor the in situ releasing of Mg salts in the simulated body fluid (SBF). The current study provides us with an orthopedic biomaterial with controllable multi-phase structures, and a tool to investigate the in vivo behaviors of biomaterials.
2014, 32(4): 509-518
doi: 10.1007/s10118-014-1417-x
Abstract:
Matrix/fiber composites of -form isotactic polypropylene (iPP) matrix and -iPP or PA6 fibers were prepared by laminating technique under different preparation temperatures. The mechanical properties and interfacial morphologies of these composites were studied by tensile test, optical microscopy and scanning electron microscopy, respectively. The experimental results show that the tensile yield load and tensile modulus of -iPP/PA6 matrix/fiber systems increased significantly at the expense of elongation at break. These mechanical properties show essentially no dependence on the sample preparation temperature. On the other hand, the mechanical properties of iPP matrix/fiber single polymer composites depend strongly on the sample preparation temperature. At low sample preparation temperature, e.g., 172 ℃, the solid -iPP fiber induces -iPP crystallization, leading to the formation of -iPP transcrystalline layer around the fiber. This results in a remarkable increment of the tensile yield load and tensile modulus. The elongation at break is also much better than that of the iPP/PA6 matrix/fiber system. It reflects a better interfacial adhesion of the single polymer composite compared with the iPP/PA6 composite. At higher sample preparation temperature, e.g., 174 ℃ or 176 ℃, the partial surface melting of the oriented fiber allows interdiffusion of iPP molecular chains in the molten fiber and matrix melt. The penetration of matrix chains into the molten iPP fiber results in some iPP molecular chains being included partially in the recrystallized fiber and the induced -transcrystalline layers. This kind of configuration leads to an improvement of interfacial adhesion between the fiber and matrix, which causes a simultaneous increase of the tensile yield load, tensile modulus and elongation at break of -iPP.
Matrix/fiber composites of -form isotactic polypropylene (iPP) matrix and -iPP or PA6 fibers were prepared by laminating technique under different preparation temperatures. The mechanical properties and interfacial morphologies of these composites were studied by tensile test, optical microscopy and scanning electron microscopy, respectively. The experimental results show that the tensile yield load and tensile modulus of -iPP/PA6 matrix/fiber systems increased significantly at the expense of elongation at break. These mechanical properties show essentially no dependence on the sample preparation temperature. On the other hand, the mechanical properties of iPP matrix/fiber single polymer composites depend strongly on the sample preparation temperature. At low sample preparation temperature, e.g., 172 ℃, the solid -iPP fiber induces -iPP crystallization, leading to the formation of -iPP transcrystalline layer around the fiber. This results in a remarkable increment of the tensile yield load and tensile modulus. The elongation at break is also much better than that of the iPP/PA6 matrix/fiber system. It reflects a better interfacial adhesion of the single polymer composite compared with the iPP/PA6 composite. At higher sample preparation temperature, e.g., 174 ℃ or 176 ℃, the partial surface melting of the oriented fiber allows interdiffusion of iPP molecular chains in the molten fiber and matrix melt. The penetration of matrix chains into the molten iPP fiber results in some iPP molecular chains being included partially in the recrystallized fiber and the induced -transcrystalline layers. This kind of configuration leads to an improvement of interfacial adhesion between the fiber and matrix, which causes a simultaneous increase of the tensile yield load, tensile modulus and elongation at break of -iPP.
