Crystallization behavior,mechanical properties,and environmental biodegradability of poly(β‐hydroxybutyrate)/cellulose acetate butyrate blends

The miscibility, crystallization behavior, tensile properties, and environmental biodegradability of poly(β‐hydroxybutyrate) (PHB)/cellulose acetate butyrate (CAB) blends were studied with differential scanning calorimetry, scanning electron microscopy, wide‐angle X‐ray diffraction, and polarizing optical microscopy. The results indicated that PHB and CAB were miscible in the melt state. With an increase in the CAB content, the degree of crystallinity and melting temperature of the PHB phase decreased, and this broadened the narrow processability window of PHB. As the elongation at break increased from 2.2 to 7.3%, the toughness and ductility of PHB improved. From the degradation test, it could be concluded that degradation occurred gradually from the surface to the inside and that the degradation rate could be adjusted by the addition of the CAB content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2116–2122, 2003     

Miscibility and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate)/phenoxy blends

Miscibility and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate) (PBST)/poly(hydroxyl ether biphenyl A) (phenoxy) blends were investigated with various techniques in this work. PBST and phenoxy are completely miscible as evidenced by the single composition‐dependent glass transition temperature over the entire blend compositions. Nonisothermal melt crystallization peak temperature is higher in neat PBST than in the blends at a given cooling rate. Isothermal melt crystallization kinetics of neat and blended PBST was studied and analyzed by the Avrami equation. The overall crystallization rate of PBST decreases with increasing crystallization temperature and the phenoxy content in the PBST/phenoxy blends; however, the crystallization mechanism of PBST does not change. Moreover, blending with phenoxy does not modify the crystal structure but reduces the crystallinity degree of PBST in the PBST/phenoxy blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of olefin‐based compatibilizers on the morphology,thermal and mechanical properties of ABS/polyamide‐6 blends

In this study, commercially available epoxidized and maleated olefinic copolymers, EMA‐GMA (ethylene‐methyl acrylate‐glycidyl methacrylate) and EnBACO‐MAH (ethylene‐n butyl acrylate‐carbon monoxide‐maleic anhydride), were used at 0, 5, and 10% by weight to compatibilize the blend composed of ABS (acrylonitrile‐butadiene‐styrene) terpolymer and PA6 (polyamide 6). Compatibilizing performance of these two olefinic polymers was investigated from blend morphologies, thermal and mechanical properties as a function of blend composition, and compatibilizer loading level. Scanning electron microscopy (SEM) studies showed that incorporation of compatibilizer resulted in a fine morphology with reduced dispersed particle diameter at the presence of 5% compatibilizer. The crystallization behavior of PA6 phase in the blends was explored for selected blend compositions by differential scanning calorimetry (DSC). At high compatibilizer level a decrease in the degree of crystallization was observed. In 10% compatibilizer containing blends, formation of γ‐crystals was observed contrary to other compatibilizer compositions. The behavior of the compatibilized blend system in tensile testing showed the negative effect of using excess compatibilizer. Different trends in yield strengths and strain at break values were observed depending on compatibilizer type, loading level, and blend composition. With 5% EnBACO‐MAH, the blend toughness was observed to be the highest at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 926–935, 2007     

Morphology and mechanical properties of polyamide‐6/K resin blends

Mechanical properties and morphological studies of compatibilized blends of polyamide‐6 (PA‐6)/K resin grafted with maleic anhydride (K‐g‐MAH) and PA‐6/K resin/K‐g‐MAH were investigated as functions of K resin/K‐g‐MAH and dispersed phase K resin concentrations, and all the blends were prepared using twin screw extruder followed by injection molding. Scanning electron microscopy (SEM) were used to assess the fracture surface morphology and the dispersion of the K resin in PA‐6 continuous phase, the results showing extensive deformation in presence of K‐g‐MAH, whereas, uncompatibilized PA‐6/K resin blends show dislodging of K resin domains from the PA‐6 matrix. Dynamic mechanical thermal analysis (DMTA) test reveals the partially miscibility of PA‐6 with K‐g‐MAH, and differential scanning calorimetry (DSC) results further identified that the introduction of K‐g‐MAH greatly improved the miscibility between PA‐6 and K resin. The mechanical properties of PA‐6/K resin blends and K‐g‐MAH were studied through bending, tensile, and impact properties. The Izod notch impact strength of PA‐6/K‐g‐MAH blends increase with the addition of K‐g‐MAH, when the K‐g‐MAH content adds up to 20 wt %, the impact strength is as more than 6.2 times as pure PA‐6, and accompanied with small decrease in the tensile and bending strength less than 12.9% and 17.5%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable poly(L‐lactic acid)/poly(butylene succinate‐co‐adipate) blends: Miscibility,morphology, and thermal behavior

Blends of two biodegradable and semicrystalline polymers, poly(L ‐lactic acid) (PLLA) and poly(butylene succinate‐co‐adipate) (PBSA), were prepared by solvent casting in different compositions. The miscibility, morphology, and thermal behavior of the blends were investigated using differential scanning calorimetry and optical microscopy. PLLA was found to be immiscible with PBSA as evidenced by two independent glass transitions and biphasic melt. Nonisothermal crystallization measurements showed that fractionated crystallization behavior occurred when PBSA was dispersed as droplets, evidenced by multiple crystallization peaks at different supercooling levels. Crystallization and morphology of the blends were also investigated through two‐step isothermal crystallization. For blends where PLLA was the major component, different content of PBSA did not make a significant difference in the crystallization mechanism and rate of PLLA. For blends where PBSA was the major component, the crystallization rate of PBSA decreased with increasing PLLA content, while the crystallization mechanism did not change. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Miscibility and properties of completely biodegradable blends of poly(propylene carbonate) and poly(butylene succinate)

Completely biodegradable blends of poly (propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt‐prepared and then compression‐molded. The miscibilities of the two aliphatic polyesters, that is, PPC and PBS, were investigated by dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The static mechanical properties, thermal behaviors, crystalline behavior, and melt flowability of the blends were also studied. Static tensile tests showed that the yield strength and the strength at break increased remarkably up to 30.7 and 46.3 MPa, respectively, with the incorporation of PBS. The good ductility of the blends was maintained in view of the large elongation at break. SEM observation revealed a two‐phase structure with good interfacial adhesion. The immiscibility of the two components was verified by the two independent glass‐transition temperatures obtained from DMA tests. Moreover, thermogravimetric measurements indicated that the thermal decomposition temperatures (T_?5% and T_?10%) of the PPC/PBS blends increased dramatically by 30–60°C when compared with PPC matrix. The melt flow indices of the blends showed that the introduction of PBS improved the melt flowability of the blends. The blending of PPC with PBS provided a practical way to develop completely biodegradable blends with applicable comprehensive properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Control of structure and mechanical properties for binary blends of poly(3‐hydroxybutyrate) and cellulose derivative

Structure and mechanical properties for binary blends composed of a poly(3‐hydroxybutyrate) (PHB) and a cellulose derivative, such as cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB), have been studied by means of dynamic mechanical analysis, isothermal crystallization measurements, and tensile testing. It is found that β relaxation temperature due to glass transition of PHB or PHB‐rich phase in the blends, in which the cellulose derivative has lower molecular weight, is almost the same as that of the pure PHB. On the other hand, the peak location is shifted to even lower temperature than that of the pure PHB by blending the cellulose derivative with higher molecular weight, although the cellulose derivative is a glassy polymer with high glass transition temperature. Further, the blend with lower β relaxation temperature exhibits ductile behavior with low modulus in uniaxial deformation. The difference in the structure and mechanical properties for the blends are found to be determined by the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3447–3452, 2007     

Hydrogen bonding,miscibility, crystallization,and thermal stability in blends of biodegradable polyhydroxyalkanoates and polar small molecules of 4‐tert‐butylphenol

The hydrogen bonding, miscibility, crystallization, and thermal stability of poly(3‐hydroxybutyrate) (PHB)/4‐tert‐butylphenol (BOH) blends and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(3HB‐3HHx)]/BOH blends were investigated by Fourier transform infrared (FTIR) spectroscopy, solid‐state¹³C‐NMR, differential scanning calorimetry, wide‐angle X‐ray diffraction (WAXD), and thermogravimetric analysis. The results of FTIR spectroscopy and solid‐state¹³C‐NMR show that intermolecular hydrogen bonds existed between the two components in the blends and that the interaction was caused by the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of BOH. With increasing BOH content, the chain mobility of both the PHB and P(3HB‐3HHx) components was improved. After the samples were quenched, the detected single glass‐transition temperatures decreased with composition, indicating that both PHB/BOH and P(3HB‐3HHx)/BOH were miscible blends in the melt. Moreover, as BOH content increased, the melting temperatures of PHB and P(3HB‐3HHx) clearly decreased, which implied that their crystallization was suppressed by the addition of BOH. Although the crystallinity of PHB and P(3HB‐3HHx) components decreased with increasing BOH content in the blends, their crystal structures were hardly affected after they were blended with BOH, which was further proven by WAXD results. In addition, the thermal stability of PHB was improved by a smaller amount of BOH.     

Mechanical characterization of toughened polyamide‐6 blends with metallocene copolymers

The effectiveness as impact modifier of two in situ maleated metallocene copolymers, a metallocene polyethylene, (mPE1) and a metallocene ethylene‐propylene (mEPDM) and three commercial maleated copolymers (mPE2‐g‐MA, EPDM‐g‐MA, and mEPR‐g‐MA) were studied in binary and ternary blends carried out in an intermeshing corotating twin‐screw extruder with polyamide‐6 (PA) as matrix (80 wt %). Also, the effects of the grafting degree, viscosity ratio, and crystallinity of the dispersed phases on the morphological and mechanical properties of the blends were investigated. A significant improvement of the compatibility of these grafted copolymers with PA6 was shown by FTIR spectroscopy, capillary rheometry, and scanning electron microscopy (SEM) in all reactive blends. The tensile strength values of the mEPR‐g‐MA/PA2 binary blend showed the highest strain hardening. The results obtained in this work indicated that the effectiveness of the grafted copolymers as impact modifier depends on the morphology of the blends and a combination of tensile properties of the blend components such as Young's modulus, Poisson ratio, and break stress. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of microcompounding process parameters on the properties of ABS/polyamide‐6 blends based nanocomposites

Melt intercalation method was applied to produce acrylonitrile‐butadiene‐styrene/polyamide‐6 (ABS/PA6) blends based organoclay nanocomposites using a conical twin‐screw microcompounder. The blend was compatibilized using a maleated olefinic copolymer. The effects of microcompounding conditions such as screw speed, screw rotation‐mode (co‐ or counter‐), and material parameters such as blend composition and clay loading level on the morphology of the blends, dispersibility of nanoparticles, and mechanical properties were investigated. Furthermore, corotating screws were modified to achieve elongational flow which is efficient for obtaining dispersive mixing. The morphology was examined by SEM analysis after preferential extraction of the minor phase. Subsequently, the SEM micrographs were quantitatively analyzed using image analyzer software. The morphology of the blends indicated that processing with counter‐rotation at a given screw speed yielded coarser morphology than that of processed with corotation. X‐ray diffraction analysis showed that highest level of exfoliation is observed with increasing PA6 content, at 200 rpm of screw speed and in corotation mode. Also, the effects of screw speed, screw rotation mode, and screw modification were discussed in terms of XRD responses of the nanocomposites. The aspect ratio of the clay particles which were measured by performing image analysis on TEM micrographs exhibited a variation with processing conditions and they are in accordance with the modulus of the nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Starch‐based biodegradable blends: morphology and interface properties

In order to improve the properties of plasticized wheat starch (PWS) and to conserve its final biodegradability, PWS can be blended with biodegradable polyesters [polyesteramide, poly(ε‐caprolactone), poly(lactic acid), poly(butylene succinate adipate) and poly(butylene adipate terephthalate)] which exhibit variable polar characteristics. This paper is focused on the analysis of the compatibility of these blends which vary according to their formulation. To understand the lack of affinity between the different phases, interface adhesion has been investigated by contact angle measurements to obtain the work of adhesion. From these determinations a forecast approach has been developed to predict blend compatibility. Blend structures were obtained by scanning electron microscopy observations. Blends show either a dispersed structure or a co‐continuous morphology. Percolation thresholds (co‐continuity) and full continuity regions were determined thanks to a method based on solvent extraction. Finally, rheological investigations have been carried out on the different biodegradable polymers to understand better the blend structure formation during the process. Copyright © 2004 Society of Chemical Industry     

Rheological and thermal properties of single‐site polyethylene blends

Branched polyethylenes, low‐density polyethylenes (LDPE1 and LDPE2) or long‐chain‐branched very low density polyethylenes (VLDPE2), were blended with very low density polyethylenes containing short branches (VLDPE1 and VLDPE3). The rheological and thermal measurements of the pure copolymers and their blends (VLDPE1–LDPE1, VLDPE1–LDPE2, VLDPE1–VLDPE2, and VLDPE2–VLDPE3) were taken by controlled stress rheometry and differential scanning calorimetry, respectively. The shear‐thinning effect became stronger with increasing long‐chain‐branched polymer compositions when it was correlated with the flow behavior index, and the extent of shear thinning was different for each blend set. Stronger shear thinning and a linear composition dependence of the zero‐shear viscosity were observed for the VLDPE1–LDPE1 and VLDPE1–LDPE2 blends. These blends followed the log additivity rule, and this indicated that they were miscible in the melt at all compositions. In contrast, a deviation from the log additivity rule was observed for the VLDPE1–VLDPE2 blend compositions with 50% or less VLDPE2 and for the VLDPE3–VLDPE2 blends with 50% or more VLDPE2. The thermal properties of the blends were consistent with the rheological properties. VLDPE1–LDPE1 and VLDPE1–LDPE2 showed that these blends were characteristic of a single‐component system at all compositions, whereas the phase separation (immiscibility) was detected only for VLDPE1–VLDPE2 blends with 50% or less VLDPE2 and for VLDPE3–VLDPE2 blends with 50% or more VLDPE2. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1549–1557, 2005     

Plasma treatment for enhancing mechanical and thermal properties of biodegradable PVA/starch blends

Two series of biodegradaable polyvinyl alcohol (PVA)/starch blends, i.e., PVA with/without plasma treatment (PP/P series), were produced by single‐screw extruder. The influences of plasma pretreatment and PVA content on the tensile properties, thermal behaviors, melt flow index, and biodegradability of blends were investigated. PVA pretreated by plasma (PPVA) reacted with glycerol was found not only to mechanically strengthen the PPVA/starch blend but also to improve the compatibility of PPVA and starch. Compared with PVA/starch blends, the melt flow indices of PPVA/starch blends were improved significantly by 200–300% and their tensile strength also increased two‐to‐three‐fold. Thermogravimetry analysis (TGA) showed that the thermal stability of PPVA/starch (85/300g) blend was better than PVA/starch blend at processing temperature and outperformed than PVA and starch at high temperature. Both the PPVA/starch and PVA/starch blends finished biodegradation within 9–10 weeks in soil burial tests. The esterification reaction of PPVA and glycerol was characterized by FTIR spectroscopic measurement and TGA test. The morphologic evolutions of the blend during biodegradation were investigated carefully by scanning electron microscope (SEM) imaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase behavior and physical properties of injection‐molded polyamide 6/phenoxy blends

Polyamide 6 (PA 6)/poly(hydroxyether of bisphenol A) (phenoxy) blends were obtained by direct injection molding over the whole composition range. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM) showed the almost full immiscibility of the blends and the lack of effect of phenoxy on the crystalline phase of PA 6. The rodlike and fine‐dispersed phase of the tensile specimens was strongly deformed during tensile testing, giving characteristic fibrilar structures. The Young's modulus and yield stress showed small deviations from additivity that appeared related mainly to the blending‐induced free‐volume change. Despite immiscibility, the ductility behavior was also additive, probably due to the fibrilar morphology. However, the thicker impact specimens gave rise to less oriented larger dispersed phases and to full plane strain conditions that, in opposition to ductility, yielded impact strength values well below linearity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1113–1124, 1999     

Investigation of thermal degradation and flammability of polyamide‐6 and polyamide‐6 nanocomposites

In this paper, polyamide‐6 and polyamide‐6 nanocomposites were prepared by direct melt intercalation technique. The thermal degradation behavior of both polyamide‐6 and polyamide‐6 clay nanocomposites has been studied. The apparent activation energy of the nanocomposites is almost the same with that of pure polymer under nitrogen, but the apparent activation energy of the nanocomposites is greatly enhanced in air atmosphere. This increasing trend coincides with the thermal analysis and the cone calorimeter results, which may suggest that the polymer/clay nanocomposites have a higher thermal stability and lower flammability. The kinetic analysis also indicates that the pyrolytic degradation and the thermal oxidative degradation of PA6 and PA6/OMT nanocomposites are two kinds of different reaction models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2297–2303, 2007     

Miscibility windows in ternary polymer blends of a polyester,polymethacrylate and poly(styrene‐co‐acrylonitrile)

Miscibility, phase diagrams and morphology of poly(ε‐caprolactone) (PCL)/poly(benzyl methacrylate) (PBzMA)/poly(styrene‐co‐acrylonitrile) (SAN) ternary blends were investigated by differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM). The miscibility window of PCL/PBzMA/SAN ternary blends is influenced by the acrylonitrile (AN) content in the SAN copolymers. At ambient temperature, the ternary polymer blend is completely miscible within a closed‐loop miscibility window. DSC showed only one glass transition temperature (T_g) for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends; furthermore, OM and SEM results showed that PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 were homogeneous for any composition of the ternary phase diagram. Hence, it demonstrated that miscibility exists for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends, but that the ternary system becomes phase‐separated outside these AN contents. Copyright © 2003 Society of Chemical Industry     

Thermal and mechanical properties of biodegradable blends of poly(L‐lactic acid) and lignin

The thermal and mechanical properties of the biodegradable blends of poly(L ‐lactic acid) (PLLA) and lignin prepared by manual mixing have been investigated. Both the results of DSC and FTIR spectral analyses indicated the existence of intermolecular interaction between PLLA and lignin. Furthermore, FTIR elucidated the existence of an intermolecular hydrogen‐bonding interaction. Study of the mechanical properties of the blends indicated that the maximum strength and the elongation of the material decreased and the Young's modulus remained almost constant when the lignin content reached 20%. Thermogravimetry indicated that lignin would accelerate the thermal degradation of PLLA when the content of lignin was more than 20%. Compared with some other biodegradable polymers, the blend of PLLA and lignin is thought to be a promising material, because the material properties, as well as the price, are at an acceptable level when the content of lignin is less than about 20%. Copyright © 2003 Society of Chemical Industry     

Biodegradable polymer blends: miscibility,physicochemical properties and biological response of scaffolds

This review provides an overview of synthetic biodegradable polymer blends prepared for tissue engineering applications and aims at establishing structure‐physicochemical‐biological properties relationships. The characteristics of blends consisting of semi‐crystalline/semi‐crystalline and semi‐crystalline/amorphous polymers are presented. Their biological properties such as degradability and biocompatibility and their biological performance as scaffolds in relation to cell adhesion, proliferation, infiltration, morphology and type are discussed. From available data, it can be deduced that miscibility influences physicochemical properties of the corresponding biodegradable polymeric blend scaffold, which in turn impacts on biological response. Immiscibility in polymer blends generally translates into good cell adhesion and proliferation. However, better cellular infiltration has been noted in compatible blends compared to immiscible blends. Factors such as crystallinity versus amorphous character, chirality, surface properties, degradation rate/products, mechanical properties and scaffold fabrication techniques are shown to have a major bearing on cell growth. © 2015 Society of Chemical Industry     

Glass transition and mechanical properties of PLLA and PDLLA‐PGA copolymer blends

The change of the glass transition temperatures (T_g) in the blend of poly(L ‐lactic acid) (PLLA) and the copolymers of poly(D,L ‐lactic acid) and poly(glycolic acid) (PDLLA‐PGA) with different D,L ‐lactic acid and glycolic acid composition ratio (50 : 50, 65 : 35, and 75 : 25) was studied by DSC. Dynamic mechanical measurement and tensile testing were performed at various temperatures around T_g of the blend. In the blend of PLLA and PDLLA‐PGA50 (composition ratio of PDLLA and PGA 50 : 50), T_g decreased from that of PLLA (about 58°C) to that of PDLLA‐PGA50 (about 30°C). A single step decrease was observed in the DSC curve around T_g between the weight fraction of PLLA (W(PLLA)) 1.0 and 0.7 (about 52°C) but two‐step changes in the curve are observed between W(PLLA) = 0.6 and 0.3. The T_g change between that of PLLA and that of PDLLA‐PGA and the appearance of two T_gs suggest the existence of PLLA rich amorphous region and PDLLA‐PGA copolymer rich amorphous region in the blend. A single step decrease of E′ occurs at around T_g of the pure PLLA but the two‐step decrease was observed at W(PLLA) = 0.6 and 0.4, supporting the existence of the PLLA rich region and PDLLA‐PGA rich region. Tensile testing for various blends at elevated temperature showed that the extension without yielding occurred above T_g of the blend. Partial miscibility is suggested for PLLA and PDLLA‐PGA copolymer blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2164–2173, 2004     

Miscibility,morphology and mechanical properties of rubber‐modified biodegradable poly(ester‐urethanes)

Biodegradable, lactic acid based amorphous poly(ester‐urethane)s (PEU) were modified with poly(L‐lactic acid‐co‐ϵ‐caprolactone‐urethane) elastomer (P[LA/CL]U) by melt blending. The phase separation of P(LA/CL)U elastomer with three different ϵ‐caprolactone (CL) compositions (CL content 30, 50, and 70 mol %) and the mechanical properties of the resulting impact‐modified linear and branched PEU were investigated. The amounts of P(LA/CL)U elastomer in the PEU blends were 10, 15, 20, and 30 wt %. Dynamic mechanical thermal analysis (DMTA) of the blends with P(LA50/CL50)U and P(LA30/CL70)U elastomers revealed separate glass transition temperatures for rubber and matrix, indicating phase separation. No phase separation was found for P(LA70/CL30)U elastomer. The effect of mixing rate and temperature during processing on composite properties was tested by blending P(LA30/CL70)U rubber with PEU under various processing conditions. Impact modification studies were also made with two P(LA30/CL70)U elastomers having different amounts of functional groups. The influence of end‐functionalization and cross‐linking on mechanical properties was investigated in blends containing PEU and 15 wt % of these elastomers. Scanning electron microscopy (SEM) showed the morphology to change dramatically with increase in the degree of cross‐linking in the rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1074–1084, 2000