Quantitative FTIR study of PHBV/bisphenol A blends

FTIR spectroscopy was used to verify the presence of intermolecular hydrogen bond (inter-H-bond) between poly-(3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV) and bisphenol A (BPA). By monitoring the spectral changes during PHBV crystallization and blends dissociation, the absorptivity ratio of C=O bonds in crystalline and amorphous regions in PHBV and that of H-bonded and free C=O in PHBV/BPA blends were experimentally determined as 1.40 and 1.68, respectively. Using curve-fitting program, the C=O absorptions in spectra of blends were ascribed to three types of bonds: amorphous, crystalline and H-bonded C=O. The crystallinity of PHBV and the fraction of H-bonded C=O were calculated. These results indicated that the H-bond clearly suppressed the PHBV crystallization. Furthermore, the fraction of BPA molecules that simultaneously formed two hydrogen bonds (H-bonds) with C=O was estimated. It revealed that there existed a H-bond network in PHBV/BPA blends. This network was compared with the covalent network by estimating the number of atoms between every two adjacent crosslink points in chain. Up to the high density of H-bond discussed in this paper, there was always a certain part in PHBV that crystallized due to the dynamic character of hydrogen bonds; however, the hydrogen bonds significantly reduced the crystallization rate of PHBV.

Synthesis and characterization of maleated poly(3-hydroxybutyrate)

Graft copolymerization of maleic anhydride (MA) onto poly(3-hydroxybutyrate) (PHB) was carried out by use of benzoyl peroxide as initiator. The effects of various polymerization conditions on graft degree were investigated, including solvents, monomer and initiator concentrations, reaction temperature, and time. The monomer and initiator concentrations played an important role in graft copolymerization, and graft degree could be controlled in the range from 0.2 to 0.85% by changing the reaction conditions. The crystallization behavior and the thermal stability of PHB and maleated PHB were studied by DSC, WAXD, optical microscopy, and TGA. The results showed that, after grafting MA, the crystallization behavior of PHB was obviously changed. The cold crystallization temperature from the glass state increased, the crystallization temperature from the melted state decreased, and the growth rate of spherulite decreased. With the increase in graft degree, the banding texture of spherulites became more distinct and orderly. Moreover, the thermal stability of maleated PHB was obviously improved, compared with that of pure PHB.

Miscibility and crystallization behavior of poly(3-hydroxyvalerate-co-3-hydroxyvalerate)/poly(propylene carbonate) blends

Blends of synthetic poly(propylene carbonate) (PPC) with a natural bacterial copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 8 mol % 3-hydroxyvalerate units were prepared with a simple casting procedure. PPC was thermally stabilized by end-capping before use. The miscibility, morphology, and crystallization behavior of the blends were investigated by differential scanning calorimetry, polarized optical microscopy, wide-angle X-ray diffraction (WAXD), and small-angle Xray scattering (SAXS). PHBV/PPC blends showed weak miscibility in the melt, but the miscibility was very low. The effect of PPC on the crystallization of PHBV was evident. The addition of PPC decreased the rate of spherulite growth of PHBV, and with increasing PPC content in the PHBV/PPC blends, the PHBV spherulites became more and more open. However, the crystalline structure of PHBV did not change with increasing PPC in the PHBV/PPC blends, as shown from WAXD analysis. The long period obtained from SAXS showed a small increase with the addition of PPC.

Monte Carlo simulation of miscibility of polymer blends with repulsive interactions: effect of chain structure

The effects of the chain structure and the intramolecular interaction energy of an A/B copolymer on the miscibility of the binary blends of the copolymer and homopolymer C have been studied by means of a Monte Carlo simulation. In the system, the interactions between segments A, B and C are more repulsive than those between themselves. In order to study the effect of the chain structure of the A/B copolymer on the miscibility, the alternating, random and block copolymers were introduced in the simulations, respectively. The simulation results show that the miscibility of the binary blends strongly depends on the intramolecular interaction energy ((ε) over bar (AB)) between segments A and B within the A/B copolymers. The higher the repulsive interaction energy, the more miscible the A/B copolymer and homopolymer C are. For the diblock copolymer/homopolymer blends, they tend to form micro phase domains. However, the phase domains become so small that the blend can be considered as a homogeneous phase for the alternating copolymer/ homopolymer blends. Furthermore, the investigation of the average end-to-end distance ((h) over bar) in different systems indicates that the copolymer chains tend to coil with the decrease Of (ε) over bar (AB) whereas the (h) over bar of the homopolymer chains depends on the chain structure of the copolymers.

Brittle-ductile transition in PP/EPDM blends: effect of notch radius

The toughness of polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) blends was studied over wide ranges of EPDM content and temperature. In order to study the effect of notch radius (R), the toughness of the samples with different notch radii was determined from Izod impact test. The results showed that both toughness and brittle-ductile transition (BDT) of the blends were a function of R, respectively. At test temperatures, the toughness tended to decrease with increasing 1/R for various PP/EPDM blends. Moreover, the brittle-ductile transition temperature (T-BT) increased with increasing 1/R, whereas the critical interparticle distance (IDc) reduced with increasing 1/R. Finally, it was found that the different curves of IDc versus test temperature (T) for different notches reduced down to a master curve if plotting IDc versus T-BT(m)-T, where T-BT(m) was the T-BT of PP itself for a given notch, indicating that T-BT(m)-T was a more universal parameter that determined the BDT of polymers. This conclusion was well in agreement with the theoretical prediction.

Surface phase separations of PMMA/SAN blends investigated by atomic force microscopy

The thin films of poly(methyl methacrylate) (PMMA), poly(styrene-co-acrylonitrile) (SAN) and their blends were prepared by means of spin-coating their corresponding solutions onto silicon wafers, followed by being annealed at different temperatures. The surface phase separations of PMMA/SAN blends were characterized by virtue of atomic force microscopy (AFM). By comparing the tapping mode AFM (TM-AFM) phase images of the pure components and their blends, surface phase separation mechanisms of the blends could be identified as the nucleation and growth mechanism or the spinodal decomposition mechanism. Therefore, the phase diagram of the PMMA/SAN system could be obtained by means of TM-AFM. Contact mode AFM was also used to study the surface morphologies of all the samples and the phase separations of the blends occurred by the spinodal decomposition mechanism could be ascertained. Moreover, X-ray photoelectron spectroscopy was used to characterize the chemical compositions on the surfaces of the samples and the miscibility principle of the PMMA/SAN system was discussed.

Pressure-dependent glass-transition temperatures of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The pressure-dependent glass-transition temperatures (T-g's) of poly(methyl methacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were determined by pressure-volume-temperature (PVT) dilatometry via an isobaric cooling procedure. The Gordon-Taylor and Fox equations were used to evaluate the relationships between the T-g's and compositions of the PMMA/SAN system at different pressures. The relationships were well fitted by the Gordon-Taylor equation, and the experimental data for T-g positively deviated from the values calculated with the Fox equation. Also, the influence of the cooling rate (during the PVT measurements) on T-g was examined.

Compatibilization of polyamide-6/syndiotactic polystyrene blends using styrene/glycidyl methacrylate copolymers

Blends of polyamide-6 (PA6) with syndiotactic polystyrene (sPS) were prepared using a series of styrene/glycidyl methacrylate (SG) copolymers as compatibilizers. These copolymers are miscible with sPS, and the epoxide units in SG are capable of reacting with PA6 end groups. These copolymers thus have the potential to form SG-g-PA6 graft copolymers at the PA6/sPS interface during melt processing. This study focuses on the effects of functionality and concentration of the compatibilizer on the morphological, mechanical and crystallization behaviors of the blends.. In general, SG copolymers are effective in reducing the sPS domain size and improving the interfacial adhesion. About 5 wt% glycidyl methacrylate (GMA) is the optimum content in SG copolymer that produces the best compatibilization. Both the strength and modulus of the blend have been improved on addition of the SG copolymers, accompanying a loss in toughness when higher concentration copolymer is added. Incorporation of SG compatibilizers to PA6/sPS blend has little influence on the crystallization behavior of PA6 component but resulted in a steady reduction in intensity of crystallinity peak of sPS and simultaneous crystallization of sPS with PA6 is observed.

Morphology, structure, and properties of in situ compatibilized linear low-density polyethylene/polystyrene and linear low-density polyethylene/high-impact polystyrene blends

Blends of linear low-density polyethylene (LLDPE) with polystyrene (PS) and blends of LLDPE with high-impact polystyrene (HIPS) were prepared through a reactive extrusion method. For increased compatibility of the two blending components, a Lewis acid catalyst, aluminum chloride (AlCl3), was adopted to initiate the Friedel-Crafts alkylation reaction between the blending components. Spectra data from Raman spectra of the LLDPE/PS/AlCl3 blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of the benzene rings of PS, and this confirmed the graft structure of the Friedel-Crafts reaction between the polyolefin and PS. Because the in situ generated LLDPE-g-PS and LLDPE-g-HIPS copolymers acted as compatibilizers in the relative blending systems, the mechanical properties of the LLDPE/PS and LLDPE/HIPS blending systems were greatly improved. For example, after compatibilization, the Izod impact strength of an LLDPE/PS blend (80/20 w/w) was increased from 88.5 to 401.6 J/m, and its elongation at break increased from 370 to 790%. For an LLDPE/HIPS (60/40 w/w) blend, its Charpy impact strength was increased from 284.2 to 495.8 kJ/m(2). Scanning electron microscopy micrographs showed that the size of the domains decreased from 4-5 to less than 1 mum, depending on the content of added AlCl3.

Rheology and morphology of reactively compatibilized PP/PA6 blends

This work aims to use the Palierne emulsion type model to describe the relationship between the rheological response to small amplitude oscillatory deformation and morphology of polypropylene/polyamide 6 (PP/PA6) blends compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). It was found that the Palierne emulsion type model could describe very well the linear viscoelastic responses of binary uncompatibilized PP/PA6 blends and failed to describe the ternary compatibilized PP/PP-g-MAH/PA6 blends. These features could be attributed to the fact that the morphology of the ternary blends was not of the emulsion type with the PA6 particles dispersed in the PP matrix but of an emulsion-in-emulsion type, i.e., PA6 particles dispersed in the PP matrix themselves contained PP or PP-g-MAH inclusions. By consideration of PP-in-PA6 particles as pure PA6 particles, where the volume fraction of the PA6 phase was increased accordingly, the Palierne emulsion type model could work very well for a ternary blending system. Preshear at low frequencies modified the morphology of both binary and ternary blends. The particles of the dispersed phase (PA6) became more uniform. These results suggested that the Palierne emulsion type model could be used to extract information on rheological properties and interfacial tension of polymer blends from known morphology and vice versa.

Improvement of mechanical property of polyimide blends with Co-60-irradiation

Radiation effects on polyimide blends' were studied at different irradiation temperatures and with different irradiation doses. The irradiation polyimides were the blends of linear polyimide (HQDPA/ODA) and 4-phenylethynyl phthalic anhydride end-capped oligomer polyimide. The tensile strength and the elongation at break of irradiated films were determined as the function of irradiation temperature and dose. Under proper conditions crosslinking reaction occurred when the polyimide blends were irradiated at high temperature. The mechanical properties of irradiated polyimide blends were found to be different from the linear polyimide.

Miscibility and hydrogen-bonding interactions in blends of carbon dioxide/epoxy propane copolymer with poly (p-vinylphenol)

The miscibility and hydrogen-bonding interactions of carbon dioxide and epoxy propane copolymer to poly(propylene carbonate) (PPC)/poly(p-vinylphenol) (PVPh) blends were investigated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The single glass-transition temperature for each composition showed miscibility over the entire composition range. FTIR indicates the presence of strong hydrogen-bonding interassociation between the hydroxyl groups of PVPh and the oxygen functional groups of PPC as a function of composition and temperature. XPS results testify to intermolecular hydrogen-bonding interactions between the oxygen atoms of carbon-oxygen single bonds and carbon-oxygen double bonds in carbonate groups of PPC and the hydroxyl groups of PVPh by the shift of C-1s peaks and the evolution of three novel O-1s peaks in the blends, which supports the suggestion from FTIR analyses.

Morphological study on water-borne conducting polyaniline-poly(ethylene oxide) blends

Conducting polyaniline-poly(ethylene oxide) blends were prepared from their aqueous solutions. The blends displayed an electrical conductivity percolation threshold as low as 1.83 wt % of polyaniline loading. As demonstrated by scanning electron microscopy, polarized optical microscopy, and wide-angle X-ray diffraction studies, the conducting polyaniline took a fibrillar morphology in the blend, and it existed only in the amorphous phase of poly(ethylene oxide). A three-phase model combining morphological factors instead of a two-phase model was proposed to explain the low-conductivity percolation threshold.

Characterization and properties of the neutral and doped blends of poly(3-dodecylthiophene) with low-density polyethylene

In this paper, the structures and properties of the neutral and doped blends of poly(3-dodecylthiophene) (P3DDT) with low-density polyethylene (LDPE) were investigated. Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the blends, and conductivity was also measured. It was found that separate crystallizations occur between P3DDT and LDPE. When the amount of P3DDT is small in the blend, it has the effect of a nucleation reagent and has some influence on the crystal structure. After doping, the interaction force between the molecular chains increases, and leads to a more compact packing and a more uniform dispersion in morphology. Through blending, the thermal stability of pure component could be greatly improved, especially when the P3DDT content is 5 wt %. The conductivity measurements indicate that the conductivity increases with the increase of the P3DDT composition and doping time.

Preparation of the HIPS/MA graft copolymer and its compatibilization in PA6/HIPS blends

The graft copolymer of high impact polystyrene (HIPS) grafted with malice anhydride (MA) (HIPS-g-MA) was prepared with melt mixing in the presence of a free-radical initiator. The grafting reaction was confirmed by IR analyses and the amount of MA grafted on HIPS was evaluated by a titration method. 1-5 wt% of MA can be grafted on HIPS. HIPS-g-MA is miscible with HIPS. Its anhydride group can react with the PA6 during melt mixing the two components. The compatibility of HIPS-g-MA in the HIPS/PA6 blends was evident. Evidence of reactions in the blends was confirmed in the morphology and mechanical properties of the blends. A significant reduction in domain size was observed because of the compatibilization of HIPS-g-MA in the blends of HIPS and PA6. The tensile mechanical properties of the prepared blends were investigated and the fracture surfaces of the blends were examined by means of the scanning electron microscope (SEM). The improved adhesion in a 16%HIPS/75%PA6 blend with 9%HIPS-g-MA copolymer was detected. The morphology of fibrillar ligaments formed by PA6 connecting HIPS particles was observed.