Comparison of glass transition and interpretation on miscibility in blends of amorphous poly(vinyl methyl ether) with highly crystallizable versus less‐crystallizable polyesters

Various phase behavior of blends of poly(vinyl ether)s with polyesters of two types (highly crystalline and less crystalline with different main‐chains) were examined using differential scanning calorimetry (DSC) and optical microscopy (OM). Effects of varying the main‐chain polarity of the constituent polyesters on the phase behavior of the blends were analyzed. Miscibility in PVME/polyester blends was found only in polyesters with backbone CH₂/CO ratio = 3.5 to 7.0). T_g‐composition relationships for blends of PVME with highly crystalline polyesters (PBA, PHS) were found to differ significantly from those for PVME blends with less‐crystalline polyesters (PTA, PEAz). Crystallinity of highly crystalline polyester constituents in blends caused significant asymmetry in the T_g‐composition relationships, and induced positive deviation of blends' T_g above linearity; on the other hand, blends of PVME with less crystalline polyesters exhibit typical Fox or Gordon‐Taylor types of relationships. The χ parameters for the miscible blends were found to range from ?0.17 to ?0.33, reflecting generally weak interactions. Phase behavior was analyzed and compared among blends of PVME with rapidly crystallizing vs. less‐crystallizing polyesters, respectively. Effects of polyesters' crystallinity and structures on phase behavior of PVME/polyester blends are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2899–2911, 2007     

Mutual influence of the morphology and capillary rheological properties in nylon/glass‐fiber/liquid‐crystalline‐polymer blends

Nylon‐6/glass‐fiber (GF)/liquid‐crystalline‐polymer (LCP) ternary blends with different viscosity ratios were prepared with three kinds of nylon‐6 with different viscosities as matrices. The rheological behaviors of these blends were characterized with capillary rheometry. The morphology was observed with scanning electron microscopy and polarizing optical microscopy. This study showed that although LCP did not fibrillate in binary nylon‐6/LCP blends, LCP fibrillated to a large aspect ratio in some ternary blends after GF was added. The addition of 5 wt % LCP significantly reduced the melt viscosity of nylon‐6/GF blends to such an extent that some nylon‐6/GF/LCP blends had quite low viscosities, not only lower than those of neat resins and nylon‐6/GF blends but also lower than those of corresponding nylon‐6/LCP blends. The mutual influence of the morphology and rheological properties was examined. The great reduction of the melt viscosity was considered the result of LCP fibrillation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1619–1627, 2004     

Thermogravimetric and wide angle X-ray diffraction analysis of thermoplastic elastomers from nylon copolymer and EPDM rubber

Nylon copolymer (PA6, 66) and ethylene propylene diene (EPDM) blends with and without compatibilizer were prepared by melt mixing using Brabender Plasticorder. The thermal stability of nylon copolymer (PA6, 66)/ethylene propylene diene rubber (EPDM) blends was studied using thermogravimetric analysis (TGA). The morphology of the blends was investigated using scanning electron microscopy (SEM). In this work, the effects of blend ratio and compatibilisation on thermal stability and crystallinity were investigated. The incorporation of EPDM rubber was found to improve the thermal stability of nylon copolymer. The kinetic parameters of the degradation process were also studied. A good correlation was observed between the thermal properties and phase morphology of the blends. By applying Coats and Redfern method, the activation energies of various blends were derived from the Thermogravimetric curves. The compatibilization of the blends using EPM-g-MA has increased the degradation temperature and decreased the weight loss. EPM-g-MA is an effective compatibilizer as it increases the decomposition temperature and thermal stability of the blends. Crystallinity of various systems has been studied using wide angle X-ray scattering (WAXS). The addition of EPDM decreases the crystallinity of the blend systems.     

THERMAL ANALYSIS AND STRUCTURE STUDIES ON THE BLENDS OF LIQUID CRYSTALLINE COPOLYESTERS AND PET, PBT

The apparent uniform blends of liquid crystalline aromatic copolyesters and semiflexible polyesters PET or PBT were obtained by mechanical mixing in the molten state within certain range of composition.The effects of blending with liquid crystalline components on the structure of homopolyester matrix were examined by thermal analysis and X-ray diffraction. These results suggest that the LC component in the blend may possibly be acting as a nucleating agent, or it may induce axial orientation of molecules promoting the local ordering of matrix. For the blends of PET, these influences mainly display in narrowing the width of cold crystalline peak and enhancing the main peak of x-ray diffraction; and for the blends of PBT, the pre-melting crystalline peak was enhanced.     

Calorimetric study of blends of poly(butylene terephthalate) and a liquid crystalline polyester

The thermal properties of solution-prepared blends of poly(butylene terephthalate) (PBT) and liquid crystalline poly(biphenyl-4,4′-ylene sebacate) (PB8) have been studied by differential scanning calorimetry (DSC). The smectic-to-isotropic (s → i) transition of the mesomorphic component is observed at temperatures slightly increasing with the PB8 content, in the 270–280°C range; on cooling, the mesophase formation (i → s transition) takes place at temperatures that decrease markedly with decreasing PB8 content. The temperatures of the crystal-to-smectic and smectic-to-crystal transitions of PB8 are almost invariant with blend composition. The melting and crystallization temperatures of the PBT phase decrease on increasing the content of the liquid crystalline component. These results, together with those of isothermal calorimetry of both the crystallization of the PBT component and the mesophase formation of the PB8 component of the blends, indicate that the two polymers are not immiscible in the isotropic state. In this latter state, however, the two polyesters undergo transesterification, which can be followed through changes in the DSC scans. The effect of the thermal history on the properties of the blends has been studied with particular attention. Both the dynamic and the isothermal calorimetric measurements provide evidence of an increase of the degree of crystallinity of PBT on addition of the liquid crystalline component up to about 35–50% by weight.     

Morphology and Mechanical Properties of Nylon 6/PBT Blends Compatibilized with Styrene/Maleic Anhydride Copolymer

The mechanical properties and dynamic mechanical properties of blends composed of Nylon 6 and poly(butylenes terephthalate)(PBT),with styrene/maleic anhydride(SMA)as compatibilizer,were studied.The observation on the morphologies of the etched surfaces of the cryogenically fractured specimens via scanning electron microscopy(SEM)demonstrated that in the compatibilized Nylon 6/PBT blends,there exists a finer and more uniform dispersion induced by the in-situ interfacial chemical reactions during the preparation than that in the corresponding uncompatibilized blends.On the other hand,the overall mechanical properties of the compatibilized blends could be remarkably improved compared with those of the uncompatibilized ones.Moreover,increasing the amount of the compatibilizer SMA leads to a more efficient dispersion of the PBT phase in Nylon 6/PBT blends.Furthermore,there exists an optimum level of SMA added to achieve the maximum mechanical properties.As far as the mechanism of this reactive compatibilization is concerned,the enhanced interfacial adhesion is necessary to obtain improved dispersion,stable phase morphology,and better mechanical properties.     

热致液晶PEI与PES—C共混物的研究

通过熔融共混,制备不同配比（２．５／９７．５－７５／２５）的ＰＥＩ／ＰＥＳ－Ｃ共混物,使用ＷＡＸＤ、ＤＳＣ、锥板流变仪、力学性能测试、ＳＥＭ等方法对共混物进行了研究。共混后强度、模量均有提高,在高剪切速率下,共混物的粘度有所降低。扫描电镜照片显示,共混物具有“皮芯”结构。     

Investigation of phase morphology of incompatible polyethylene/nylon 6 blends containing EPDM-based functionalized compatibilizers

Graft copolymer and graft terpolymer were prepared by solution grafting of maleic anhydride (MAH) or acrylonitrile (AN) alone and mixture of MAH and AN on to ethylene–propylene–diene terpolymer (EPDM) using benzoyl peroxide (BPO) as an initiator. The resulting EPDM-g-MAH, EPDM-g-AN and EPDM-g-(MAH-co-AN) have been used to obtain a binary blend of Nylon 6/functionalized EPDM and a ternary blend of polyethylene/Nylon 6/functionalized EPDM by melt blending. The effects of the nature and the amount of the grafted species on the phase morphology, crystallization behavior and mechanical properties of the blends were characterized through scanning electron microscopy, optical microscopy, infrared spectroscopy and using a dynamic mechanical analyzer. From the morphological study, it can clearly be seen that the presence of the functionalized EPDMs in these blends resulted in an improvement of the dispersion degree in incompatible polyethylene/Nylon 6 blends.     

Thermal analysis on phase behavior of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) interacting with aliphatic polyesters

Abstract  

Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LM_w-PLLA) or high-molecular-weight PLLA (HM_w-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH₂/CO) ratio in main chains. The blends of LM_w-PLLA/PEA and LM_w-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LM_w-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LM_w-PLLA/PTA and LM_w-PLLA/PEA blends, HM_w-PLLA with polyesters are mostly immiscible; and HM_w-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LM_w-PLLA/PEA and LM_w-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LM_w-PLLA and PTA or PEA.     

Effect of the thermal history on the phase transition and the liquid crystalline structure of thermotropic polyesters

A series of triad type thermotropic polyesters based on phenylsulfonyl hydroquinone and α,ω-bis(4-carboxyphenoxy)alkane was prepared, and the effect of the thermal history on the phase transition and the liquid crystalline structure of the polyesters was studied. The phase transition was significantly affected by the thermal history. When annealed at various temperatures, multiple endotherms were observed for all polyesters in DSC thermograms. A phase stability concept was employed to explain the complicated phase transitions. The time evolution of the liquid crystalline structure was investigated by optical microscopy and transmitted light intensity measurement under crossed polars during annealing. The steady decrease in the density of disclinations with accompanying increase of transmitted light intensity was observed. Depending on the surface conditions of the liquid crystal polymer film, two markedly different domain growth patterns and different textures were found on isothermal annealing; the continuous wormlike texture and the discontinuous droplet texture. The structural relaxation of the deformed texture during annealing was also studied. When shear was applied, the characteristic banded texture was formed in all polyesters.     

Raman and Wide-Angle X-Ray Diffraction Studies on Molecular Structure,Crystallinity, and Morphology of Uncompatibilized and Compatibilized Blends of High Molecular Weight Polyethylene/Nylon 12

Molecular structure, crystallinity and morphology of uncompatibilized and compatibilized blends of high molecular weight polyethylene (HMWPE) and Nylon 12 were investigated by using Fourier-transform (FT) Raman spectroscopy, wide-angle x-ray diffraction (WAXD), and scanning electron microscopy (SEM). One of the important purposes of the present study is to compare the present results for HMWPE/Nylon 12 with the previously obtained results for high-density polyethylene (HDPE/Nylon 12). Uncompatibilized and compatibilized blends of HMWPE/Nylon 12 with a Nylon 12 content ranging from 10 to 90 wt% at increments of 10 wt% were prepared. The compatibilized polymer blends were prepared by adding a small amount of maleic anhydride (MAH), and SEM images show that the addition of the small amount of MAH (0.5 wt%) yields a marked improvement of dispersion of HMWPE and Nylon 12. To evaluate the crystallinity of HMWPE from Raman spectra, the relative intensities of bands at 1418 and 1129 cm⁻¹ to the intensity of a band at 1000 cm⁻¹ (I₁₄₁₈/I₁₀₀₀ and I₁₁₂₉/I₁₀₀₀) were estimated for all the uncompatibilized and compatibilized blends of HMWPE/Nylon 12. From the comparison of the relative intensities (I₁₄₁₈/I₁₀₀₀ and I₁₁₂₉/I₁₀₀₀) between the uncompatibilized and compatibilized blends of HMWPE/Nylon 12 it was found that when the Nylon 12 content reaches 40 wt% the crystallinity of HMWPE in the compatibilized blends becomes higher than that of HMWPE in the uncompatibilized blends. The uncompatibilized and compatibilized blends of HMWPE/Nylon 12 (50/50) show quite different x-ray diffraction patterns; the compatibilized blend shows a significantly larger orientational effect in the x-ray pattern of HMWPE. It seems that the increase of interaction of MAH-HMWPE with the Nylon 12 matrix leads to the additional crystallinity.     

Crystalline Morphology and Crystallization Kinetics of Melt-miscible Crystalline/Crystalline Polymer Blends of Poly（vinylidene fluoride） and Poly（butylene succinate-co-24mol% hexamethylene succinate）

Poly（vinylidene fluoride） （PVDF） and poly（butylene succinate-co-24 mol% hexamethylene succinate） （PBHS）, both crystalline polymers, formed melt-miscible crystalline/crystalline polymer blends. Both the characteristic diffraction peaks and nonisothermal melt crystallization peak of each component were found in the blends, indicating that PVDF and PBHS crystallized separately. The crystalline morphology and crystallization kinetics of each component were studied under different crystallization conditions for the PVDF/PBHS blends. Both the spherulitic growth rates and overall isothermal melt crystallization rates of blended PVDF decreased with increasing the PBHS composition and were lower than those of neat PVDF, when the crystallization temperature was above the melting point of PBHS component. The crystallization mechanism of neat and blended PVDF remained unchanged, despite changes of blend composition and crystallization temperature. The crystallization kinetics and crystalline morphology of neat and blended PBHS were further studied, when the crystallization temperature was below the melting point of PBHS component. Relative to neat PBHS, the overall crystallization rates of the blended PBHS first increased and then decreased with increasing the PVDF content in the blends, indicating that the preexisting PVDF crystals may show different effects on the nucleation and crystal growth of PBHS component in the crystalline/crystalline polymer blends.     

Determination of percolation threshold electroactivity and phase behavior study on conducting blends of thermotropic polyesters and polyaniline

The new thermotropic polyester/polyaniline (PIn/PAni) blends have been prepared by solution blend of synthesized liquid crystalline poly[4,4′‐bis (ω‐alkoxy) biphenylisophthalate]s having four and six methylene units in spacer (PI4 and PI6) with PAni doped with camphorsolfonic acid (CSA). The percolation threshold electroactivity of prepared blend films has been determined by cyclic voltammetry. The effect of the PAni concentration, solvent nature and polyester structure on the electroactivity of the blends has been investigated. The extremely low percolation threshold of prepared PIn/PAni‐CSA blends from dimethylformamide (DMF) and m‐cresol solution was 3% weight of PAni‐CSA. The amount of conducting polymer necessary to retard the formation of the liquid crystalline (LC) phase is up to 45% by weight. Phase behavior studies by differential scanning calorimetry and polarizing microscopy show that blends with 45% of conducting polymer are both liquid crystal and conductive. The morphology of the blends has been investigated by scanning electron microscopy. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of compatibilizer on morphology and properties of HDPE/Nylon 6 blends

The compatibilization effect of linear low‐density polyethylene‐grafted maleic anhydride (LLDPEgMA) and high‐density polyethylene‐grafted maleic anhydride (HDPEgMA) on high‐density polyethylene (HDPE)/polyamide 6 (Nylon 6) blend system is investigated. The morphology of 45 wt %/55 wt % polyethylene/Nylon 6 blends with three compatibilizer compositions (5 wt %, 10 wt %, and 15 wt %) are characterized by atomic force microscopic (AFM) phase imaging. The blend with 5 wt % LLDPEgMA demonstrates a Nylon 6 continuous, HDPE dispersed morphology. Increased amount of LLDPEgMA leads to sharp transition in morphology to HDPE continuous, Nylon 6 dispersed morphology. Whereas, increasing HDPEgMA concentration in the same blends results in gradual morphology transition from Nylon 6 continuous to co‐continuous morphology. The mechanical properties, oxygen permeability, and water vapor permeability are measured on the blends which confirm the morphology and indicate that HDPEgMA is a better compatibilizer than LLDPEgMA for the HDPE/Nylon 6 blend system. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 281–290     

Miscibility of Semi-flexible Thermotropic Liquid Crystalline Copolyesteramide with Polyamide 66

IntroductionIn sl'tu polymer composites containing liquid crystalline polymers(LCPs) have attractedconsiderable attention in the past'decades['--'j. But the development of in sl'tu composites is restricted by two factors. First, the melting temperatures of thermotropic liquid crystallinepolymers (TLCPs) are generally higher than those of the commodity engineering resins. Athigh processing temperatures, these resins tend to become unstable, thereby, causing seriousproblems during fiber spinn…     

胆甾液晶／聚合物多组分体系的结构与性能研究（Ⅲ）──ChN／poly（MMA－CO－BMA）混合体系的形态结构

应用Ｘ射线衍射、偏光显微镜及电子显微镜研究了胆甾液晶与甲基丙烯酸甲酯（ＭＭＡ）─甲基丙烯酸丁酯（ＢＭＡ）无规共聚物共混体系的形态结构。研究了体系的结晶态及液晶态的行为和共聚物含量及组成对光学织构的影响。     

PP/PMMA/PP-g-MAH共混物的结晶和相形态研究

采用偏光显微镜和相差显微镜详细研究PP/PMMA不相容聚合物共混物体系和PP/PMMA/PP-g-PMMA增容共混体系的结晶和相形态.偏光显微照片的研究结果表明,增容剂PP-g-MAH中PP结晶需要克服更多的能垒,导致PP结晶形态变得不完善,球晶尺寸变小.比较PP/PMMA和PP/PMMA/PP-g-MAH的相差显微照片可以看出,由于增容剂的加入,PP与PMMA相之间的界面变得模糊,两相的相容性变好.随着PP-g-MAH中MAH接枝率的增加,PMMA分散相的尺寸减小且变得均匀;当增容剂的接枝率为2.41%,添加的质量分数为4.71%,PP/PMMA共混体系中PMMA分散相的相?尺寸可达最小.PP-g-MAH作为反应型增容剂,一方面与PP在界面区域产生共晶;另一方面,MAH极性基团与PMMA的极性基团间产生的强的化学键合作用,使得界面区域的PP-g-MAH分子采取有利于降低构象熵的构象来起到增容作用.PP/PMMA共混物在130℃等温结晶的结果显示,PMMA相对PP的结晶形态的影响较小,PP结晶呈现典型的均相成核特征.PP/PMMA共混体系中加入PP-g-MAH,PP结晶尺寸减少.与非等温结晶相比,等温结晶的PP/PMMA共混物中PMMA相区尺寸明显偏大.     

热致液晶聚酯共混物与复合材料研究

评述了热致液晶聚酯的共混物与复合材料的研究新进展,揭示了热行为与相容性、流变性与加工性以及形态结构与多种性能之间的内在联系,展望了应用于高强高模纤维与塑料、低热膨光纤涂层及低透气包装膜等高性能材料的前景.     

Poly(hydroxybutyrate) and epichlorohydrin elastomers blends: Phase behavior and morphology

This work studied blends of PHB with epichlorohydrin elastomers, the PEP homopolymer and its copolymer with ethylene oxide, ECO. PHB is a microbial polyester, which is accumulated intracellularly by a large number of microorganisms, presenting characteristics of biodegradability and biocompatibility. It presents a high degree of crystallinity, so is a quite brittle material, and may undergo degradation when is kept for a relatively short time at a temperature above its melting point, about 180 °C. PEP and ECO are linear and amorphous elastomers, exhibit miscibility with many aliphatic polyesters and these elastomers have been used in various branches of technology, such as the automotive industry. The proposed systems combine a polymer with high crystallinity and biodegradability, PHB, with amorphous epichlorohydrin elastomers. Blends were prepared by casting from chloroform solution at different compositions (0, 20, 40, 50, 60, 80 and 100 wt% of PHB). The phase behavior of PHB/PEP and PHB/ECO blends were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and the morphology of the crystalline phase of PHB had been examined by optical microscopy. Blends of PHB/PEP and PHB/ECO have been described in literature as miscible. However, our results from the DSC and DMA show that PHB/PEP and PHB/ECO blends are immiscible. This behavior should be related to the molecular weight of polymers used in the present work, which is higher than the molecular weight of polymers used in the previous works. The crystallization kinetics of PHB is strongly influenced by the presence of the elastomeric phase. The degree of crystallinity of PHB/PEP blends decreases with an increase in the PEP content. PHB/ECO blends present degrees of crystallinity that can be considered nearly independent of the ECO content. Differences in the morphology of the crystalline phase were also observed, and these are attributed to the presence of elastomeric phase in the intraspherulitic zone.     

Polyamide 66/EPR‐g‐MA blends: mechanical modeling and kinetic analysis of thermal degradation

The present investigation deals with the mechanical, thermal, and morphological properties of binary nylon 66/maleic anhydride grafted ethylene propylene rubber (EPR‐g‐MA) blends at different dispersed phase (EPR‐g‐MA) concentrations. The effects of EPR‐g‐MA concentration and dispersed particle size on the mechanical properties of the blends were studied. Analysis of the tensile data in terms of various theoretical models revealed the variation of stress concentration effect with blend composition and the improvement of interfacial adhesion between dispersed rubber phase and nylon 66 matrix. The thermal degradation of the blends was analyzed by nonisothermal thermogravimetric analysis (TGA). It was found that the activation energy (E_a) and overall reaction order of thermal degradation decreased with increasing EPR‐g‐MA content. The scanning electron microscopic (SEM) analysis showed a significant decrease in dispersed particle size with increasing EPR‐g‐MA content, which was explained on the basis of the level of chemical interaction (in situ compatibilization) between nylon 66 and EPR‐g‐MA. The surface morphology of the nylon 66/EPR‐g‐MA blends was illustrated by the roughness of atomic force microscopy (AFM) images. Copyright © 2008 John Wiley & Sons, Ltd.