Compatibility and biocompatibility study of new HPC/PU blends

BACKGROUND: Polymer blending is one of the most useful methods for the improvement or modification of the physicochemical properties of polymeric materials without altering the structure and function of individual polymers. The blends between biopolymers and synthetic polymers are of particular significance because they can combine biocompatibility with good processability and mechanical resistance and can be used as biomaterials. The aim of the blending of hydroxypropylcellulose (HPC) and polyurethane (PU) is to find applications for newly synthesized PUs and also to create new materials with possible medical applications and enhanced surface properties. RESULTS: Films containing mostly HPC or mostly PU are found to be homogeneous and transparent, while for the intermediate composition range a morphology of a fine dispersion in a continuous matrix is characteristic. The values of the blood–biomaterial interfacial tension (γ_SL) are in the range 1.96–3.27 mN m^?1, which allows us to conclude that these materials have a good haemocompatibility. CONCLUSION: The thermomechanical and morphological behaviour were explored and specific interactions were evident between the PU blocks and the HPC chains especially in the 60% HPC–20% HPC/40% PU–80% PU composition range because of the high degree of compatibility. The blends obtained are not cytotoxic and exhibit good surface properties and haemocompatibility. Therefore they could be candidates for medical and pharmaceutical applications. Copyright © 2008 Society of Chemical Industry     

On the compatibility of polysaccharide/maleic copolymer blends. II. Thermal behavior of pullulan‐containing blends

The compatibility of pullulan with maleic acid/vinyl acetate copolymers in the solid state in the form of thin films was studied with thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and optical microscopy. With respect to morphology, blends with a content of pullulan greater than 85 wt % exhibited an even distribution of finely dispersed particles. The thermal properties were dependent on the mixing ratio, and the interactions between components were quite pronounced in the pullulan‐rich blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1782–1791, 2002     

Effect of dynamic vulcanization on properties and morphology of nylon/SAN/NBR blends: A new compatibilization method of nylon/ABS blends

Dynamically vulcanized blends of nylon, styrene–acrylonitrile copolymer (SAN), and nitrile–butadiene rubber (NBR) were examined for mechanical properties, Shore D hardness, Vicat softening temperature, impact process, and phase morphology. The effect of a curing system such as phenolic formaldehyde resins (PF), dicumylperoxide (DCP), and a sulfur system on the mechanical properties of the nylon/SAN/NBR blends was studied, and dynamic vulcanization with a PF system was found to lead to outstanding toughness of the blends. The effect of PF content on the mechanical properties, Shore D hardness, and heat resistance of the nylon/SAN/NBR blends was also investigated. With increasing PF content the notched‐impact strength and Vicat softening temperature (VST) of the nylon/SAN/NBR (50/25/25) blends evidently improved, but tensile strength and Shore D hardness of the blends changed slightly. It can be concluded that the nylon/SAN/NBR (50/25/25) blends dynamically vulcanized by high‐content PF can attain excellent comprehensive mechanical properties, especially supertoughness, at room temperature. SEM was used to investigate the effect of dynamic vulcanization on disperse‐phase particle size, particle size distribution, and phase morphology. It was obvious that disperse‐phase particle size decreased with an increasing PF content. Thermal behavior and miscibility of dynamically vulcanized nylon/SAN/NBR with PF were investigated by DMTA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2057–2062, 2003     

Microhardness of ternary blends of polyolefins with recycled polymer components

Microhardness tests, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements were performed on melt‐pressed films of multicomponent blends based on low‐density polyethylene (LDPE), linear LDPE (LLDPE), high‐density polyethylene (HDPE), and polypropylene (PP), and their recycled homologues. Some of the PE blends also contained ethylene‐propylene‐diene monomer (EPDM) as compatibilizer. In all cases, the variation of microhardness as a function of content of the recycled component follows the additivity law of components. Thus, the range of hardness values of polyolefin blends can be controlled by choice of both components and their relative content in the blend. The hardness of the components increases from LDPE, to LLDPE, to HDPE, to PP and increases from 20 to 84 MPa. For recycled components, the hardness values are reduced by ～15%. According to DSC results, all the blends are immiscible. Results are discussed in terms of the levels of crystallinity reached for the different blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2046–2050, 2003     

Mechanical and viscoelastic behavior of natural rubber and carboxylated styrene‐butadiene rubber latex blends

The morphology, mechanical and viscoelastic behavior of latex blends of unvulcanized natural rubber (NR) with carboxylated styrene‐butadiene rubber (XSBR) were investigated, with special reference to the effect of the blend ratio, temperature, and frequency. Mechanical properties like tensile strength, modulus, and elongation at break were also studied. As the XSBR content increased, the tensile strength increased up to a 50:50 NR/XSBR ratio and then decreased as a result of the self‐curing nature of XSBR. The dynamic mechanical properties of these latex blends were analyzed for loss tangent, storage modulus, and loss modulus. The entire blend yielded two glass‐transition temperatures, which corresponded to the transitions of individual components, indicating that the system was immiscible. To determine the change in modulus with time, a master curve of 50:50 NR/XSBR blends was plotted. Time–temperature superposition and Cole–Cole analysis were done to understand the phase behavior of the latex blends. The experimental and theoretical values of storage modulus of blends were compared using the Kerner and Halpin–Tsai models. With the help of optical micrographs, attempts were made to correlate the morphology and viscoelastic behavior of these blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2639–2648, 2003     

Calorimetric and rheological study of isocyanate–pyrolysis oil blends

The reaction of polymethylene diphenyl diisocyanate (pMDI) with pyrolysis oils (PO) was studied by differential scanning calorimetry (DSC) and rheology. Chemical reactions between pMDI and PO occur under 100°C, as shown in DSC scans. DSC analysis showed that the peak temperature of the reaction decreased as the PO content of the PO–pMDI blends increased. The heat of reaction is at its maximum around 30–40% PO content. A rheological study of various PO–pMDI blends was done to evaluate the evolution of viscosity with time for different PO–pMDI hybrid mixtures. The initial viscosity of the blends is directly proportional to the PO content. An exponential increase of viscosity was demonstrated for all PO–pMDI mixtures. Rheological and chemical analysis results confirmed that chemical reactions occur between pMDI and PO at room temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1362–1370, 2003     

Rheological properties and microstructures of cellulose acetate phthalate/hydroxypropyl cellulose blends

Cellulose acetate phthalate (CAP)/hydroxypropyl cellulose (HPC) blends were investigated by means of attenuated total reflection‐Fourier transform infrared spectroscopy, thermogravimetry/differential thermal analysis, shear viscosity, oscillatory shear tests, and atomic force microscopy (AFM). Effect of solution concentrations in 2‐methoxyethanol, blend compositions, and shear rate on the rheological functions reflects the mobility of the chain segments or their orientation—with thinning behavior in the shear field. Specific interactions, such as the hydrogen bonds between polymer components and 2‐methoxyethanol used in casting solutions of films, influence the resulting morphology. Supernodular aggregates with different intensities and dimensions, which involve the coexistence of an isotropic and an anisotropic phase, typical for lyotropic cellulosic derivative liquid crystals at low concentrations, are evidenced by AFM images. This study is useful for applications of CAP/HPC blends in pharmaceutical domains.POLYM. COMPOS., 33:2072–2083, 2012. © 2012 Society of Plastics Engineers     

Controlling the phase stability of polymer blends through the introduction of impenetrable interfaces

In this work, the effect of the introduction of modified solid surfaces into polymer blends on the phase‐separation process was investigated. Glass fibers with surfaces having different chemistries were introduced into polystyrene–poly(methyl methacrylate) blends. The glass fibers used either had fully hydrated surfaces or had surfaces covered with a random copolymer, poly(styrene‐co‐methyl methacrylate). The copolymer was synthesized by free‐radical polymerization of styrene and methyl methacrylate in the presence of previously vinyl silane‐treated glass fibers. The copolymerization and grafting procedures were investigated by FTIR and thermal analysis. Blends containing the fibers were studied using FTIR microscopy and optical microscopy. FTIR microscopy results showed that the composition of the phases in the blends was shifted by using fibers with different surface chemistries. Fibers with grafted copolymers were capable of narrowing the immiscibility region in the phase diagram, while fully hydrated fibers were able to expand the gap. It was proposed that interfacial interactions regulated by a hydrophilic–hydrophobic type of forces were responsible for guiding the described phase‐separation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1619–1627, 2003     

Miscibility and crystallization of metallocene polyethylene blends with polypropylene

The crystallization and morphology of very‐low‐density polyethylene (VLDPE) and ultra‐low‐density polyethylene (ULDPE) blends with isotactic polypropylene (PP) were studied by differential scanning calorimetry (DSC) and hot‐stage optical microscopy (HSOM) with polarized light. In particular, the isothermal crystallization of PP in molten PE was investigated. A polypropylene homopolymer was melt‐blended with six types of VLDPEs and ULDPEs, with variations in branch content and length and in molecular weight. All the blends contained 20% PP by mass. It was found that the crystallization temperatures of PP and PE changed in the blends, and the crystallization of PP was affected by branch length and content and by the molecular weight of the PE, indicating a certain degree of miscibility between PP and PE. The isothermal crystallization rate of PP decreased in the blends; in particular, the crystallization rate of PP was slower in the ULDPE with lower MFI, suggesting that crystallization of PP was hindered by PE and that its rate was regulated by the viscosity of ULDPE. HSOM images showed that a portion of the PP crystallized from molten PE, although phase separation was obvious, providing additional information on the miscible behavior between PP and VLDPEs (or ULDPEs). Furthermore, the miscible level between the PP and the ULDPEs was higher than that between the PP and the VLDPEs because the degree of change in the crystallization behavior of the PP and PE was greater in the PP–ULDPE blends. This was possibly a result of the higher branch content in the ULDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1179–1189, 2003     

Surface properties of miscible poly(1,1,1,3,3,3‐hexafluoroisopropyl methacrylate)/phenoxy blends

Poly(1,1,1,3,3,3‐hexafluoroisopropyl methacrylate) (PHF) is miscible with poly(hydroxyether of bisphenol‐A) (phenoxy) as shown by the optical transparency and a single glass‐transition temperature in each blend. FTIR spectroscopy shows that the interactions between PHF and phenoxy are not particularly strong. The surface properties of the blends were studied by contact angle measurements, dynamic and static time‐of‐flight secondary ion mass spectroscopy, and X‐ray photoelectron spectroscopy. The blend surfaces were enriched with PHF. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1798–1805, 2004     

Properties of extrusion cast sheets of blends of natural and aliphatic polyesters

Natural and synthetic polymers of various compositions were blended in a twin‐screw extruder. These blends were then sheeted into thin sheets with a coat hanger die attached to a single‐screw extruder. The natural content in the blend was varied between 5 and 50 wt %, and the mechanical and morphological properties of the blends were evaluated. At 50 wt % natural content, the tensile strength decreased to a third of that of the synthetic polymer. The use of a compatibilizer doubled the tensile strength for the 50 wt % natural content blend. The sheets displayed equal strengths in the machine and transverse direction. The tear strength decreased as the natural content increased, and the decrease was greater in the anhydride‐compatibilized blends than in the uncompatibilized blends. The blends displayed two distinct glass transitions, one for each component, indicating phase separation. The crystallinity of the blends decreased as the starch content increased. This result was confirmed by differential scanning calorimetry (DSC), which showed that the melting endotherm decreased as the starch content increased. Gel permeation chromatography (GPC) results showed that the peak position was at the same location irrespective of blend composition, indicating minimal degradation of starch moieties. The water absorption was diffusion controlled, with a sharp initial burst of water uptake. Scanning electron microscopy (SEM) showed melting of starch granules that formed a co‐continuous phase with the synthetic polyester. Increasing the natural content also increased the surface roughness of the sheets. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1545–1554, 2003     

Biodegradable extruded starch blends

We prepared biodegradable extruded starch blends by first mixing starch with additives and then processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, solubility, biodegradability, rheological properties, molecular weight, and glass‐transition temperature of the extruded blends were studied. Glycerol and urea, to some extent, could both decrease the tensile strength and increase the percentage elongation at break because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. The extruded starch blends showed thermoplasticity, and their melts behaved as pseudoplastic liquids at a comparatively low shear rate. The biodegradability of the extruded starch was slightly higher than that of native starch. The molecular weight of starch displayed a decreasing tendency after extruding modification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 627–635, 2003     

Mass transfer characteristics of natural rubber/ethylene vinyl acetate blends

The transport behavior of natural rubber/ethylene vinyl acetate (NR/EVA) blends has been investigated using aromatic hydrocarbons as probe molecules, in the temperature range of 26–56°C. It has been observed that the solvent uptake decreases with increase in the EVA content of the blends. The blends were crosslinked by three systems, viz. sulfur, dicumyl peroxide (DCP), and a mixture consisting of sulfur and peroxide. The DCP crosslinked system exhibited the lowest solvent uptake. The differences in the transport behavior of the blends, crosslinked by different modes, has been described in terms of the nature of crosslinks introduced between the macromolecular chains during vulcanization. The mechanism of transport has been found to deviate from the regular Fickian behavior, observed with conventional rubbers, with an increase in EVA in the blends. The dependence of the transport coefficients on blend composition, crosslinking systems, nature of penetrants, and temperature was studied. The blend–solvent interaction parameter, enthalpy, and entropy of sorption have also been estimated from the transport data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2691–2702, 2003     

Phenoxy/Hytrel blends. II. Dynamic and tensile properties of unreacted miscible blends

The dynamic and tensile properties of Brabender mixed, compression‐molded miscible, and unreacted polyhydroxy ether of bisphenol A (Ph)/Hytrel blends were studied. Blending mainly produced a decrease in the specific volume, and in the strength of the β transition of Ph. The β transition strength decrease was attributed to both specific interactions and specific volume decrease. The measured modulus of elasticity, yield stress, and ductility of the blends were discussed as a result of the combined effect of the β transition strength decrease, crystallinity, and free volume content changes, and the position of the T_gs of the blends with respect to the testing temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 85–93, 1999     

Phase structure and viscoelastic properties of compatibilized blends of PET and HDPE recyclates

Immiscible blends of recycled poly(ethylene terephthalate) (R‐PET), containing some amount of polymeric impurities, and high‐density polyethylene (R‐PE), containing admixture of other polyolefins, in weight compositions of 75 : 25 and 25 : 75 were compatibilized with selected compatibilizers: maleated styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MA) and ethylene–glycidyl methacrylate copolymer (EGMA). The efficiency of compatibilization was investigated as a function of the compatibilizer content. The rheological properties, phase structure, thermal, and viscoelastic behavior for compatibilized and binary blends were studied. The results are discussed in terms of phase morphology and interfacial adhesion among components. It was shown that the addition of the compatibilizer to R‐PET‐rich blends and R‐PE‐rich blends increases the melt viscosity of these systems above the level characteristic for the respective binary blends. The dispersion of the minor phase improved with increasing compatibilizer content, and the largest effects were observed for blends compatibilized with EGMA. Calorimetric studies indicated that the presence of a compatibilizer had a slight affect on the crystallization behavior of the blends. The dynamic mechanical analysis provided evidence that the occurrence of interactions of the compatibilizer with blend components occurs through temperature shift and intensity change of a β‐relaxation process of the PET component. An analysis of the loss spectra behavior suggests that the optimal concentration of the compatibilizers in the considered blends is close to 5 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1423–1436, 2001     

Interphase layer formation in isotactic polypropylene/ethylene–propylene rubber blends

The influence of the interphase layer, formed by the introduction of an oil in ethylene–propylene rubber (EPR), on the structure and properties of isotactic polypropylene (iPP)/EPR blends was studied. The dispersity of the rubber phase in the iPP matrix did not depend on presence of oil. The melting temperature of iPP decreased with increasing content of oil‐extended EPR, and it did not change if the oil was absent. The compatibility parameter was determined from the dependency of the iPP melting point on the rubber content with the Nishi–Wang equation. A negative value of the parameter indicated a limited compatibility of iPP with oil‐extended EPR. The latter also reduced the temperature and heat of crystallization of iPP. The mechanical properties of iPP/EPR blends were investigated as functions of temperature and elongation rate. It appeared that elastic modulus and yield stress of the blends linearly depended on the logarithm of the elongation rate. Activation volumes, calculated with the Eyring equation, increased with increasing content of elastomer; moreover, this increase was more pronounced for the oil‐extended elastomer. It is suggested that the oil influenced the structure of the interphase layer and, accordingly, the characteristics of the iPP/EPR blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 249–257, 2003     

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 X‐ray 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. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4054–4060, 2003     

Influence of ionomeric compatibilizers on the morphology and properties of amorphous polyester/polyamide blends

The utilization of sulfonated polyester ionomers as minor‐component compatibilizers in blends of an amorphous polyester and polyamide was investigated. The blends were prepared using twin‐screw extrusion and compared to solution blends to investigate the effect of elevated temperatures and shear mixing on blend miscibility and/or phase behavior. The phase domain sizes of the solution blends with respect to ionomer content were studied using small angle light scattering (SALS) and phase contrast optical microscopy. The thermal and mechanical properties of the extruded blends were investigated using dynamic mechanical analysis (DMA) and tensile testing while the morphology was investigated using environmental scanning electron microscopy (ESEM). The interactions between the sulfonate group of the ionomer and the polyamide were characterized using FT‐IR spectroscopy. Binary blends of the amorphous polyester and polyamide were immiscible with poor mechanical properties, while blends containing the polyester ionomer as a minor‐component compatibilizer showed a significant reduction in the dispersed domain sizes and enhanced ultimate mechanical properties. The compatibilization mechanism is attributed to specific interactions between the sulfonate groups on the polyester ionomer and the amide groups of the polyamide. Polym. Eng. Sci. 44:1721–1731, 2004. © 2004 Society of Plastics Engineers.     

Compatibilization efficacy of poly(isoprene–butyl acrylate) block copolymers in natural/acrylic rubber blends

Poly(isoprene–butyl acrylate) block copolymers with a variety of molecular weights and compositions were prepared via a controlled free‐radical polymerization with an iniferter. Subsequently, the block copolymers were used as compatibilizers in natural/acrylic rubber blends. Scanning electron micrographs revealed a cocontinuous morphology in the case of the normal blends with a low natural rubber content (20 wt %), whereas the blends that contained more natural rubber showed a dispersed‐particle morphology. When the rubbers were blended with 5 wt % block copolymer, the particle size decreased, and the tensile strength of the resulted blends increased, regardless of the block copolymer characteristics. For the blend that exhibited a cocontinuous morphology, the most effective compatibilizer was the block copolymer with an average molecular weight of 22,000 g/mol, containing mainly (87%) polyisoprene block. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 921–927, 2003     

Elongational rheology of LLDPE / LDPE blends

The objective of this study is to investigate the effect of low density polyethylene (LDPE) content in linear low density polyethylene (LLDPE) on the crystallinity and strain hardening of LDPE / LLDPE blends. Three different linear low density polyethylenes (LL‐1, LL‐2 and LL‐3) and low density polyethylenes (LD‐1, LD‐2 and LD‐3) were investigated. Eight blends of LL‐1 with 10, 20, 30 and 70 wt % of LD‐1 and LD‐3, respectively, were prepared using a single screw extruder. The elongational behavior of the blends and their constituents were measured at 150°C using an RME rheometer. For the blends of LL‐1 with LD‐1, the low shear rate viscosity indicated a synergistic effect over the whole range of concentrations, whereas for the blends of LL‐1 with LD‐3, a different behavior was observed. For the elongational viscosity behavior, no significant differences were observed for the strain hardening of the 10–30% LDPE blends. Thermal analysis indicated that at concentrations up to 20%, LDPE does not significantly affect the melting and crystallization temperatures of LLDPE blends. In conclusion, the crystallinity and rheological results indicate that 10–20% LDPE is sufficient to provide improved strain hardening in LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3070–3077, 2003