Influence of liquid crystalline polymer and recycled PET as minor blending components on rheological behavior,morphology, and thermal properties of thermoplastic blends

In this study, the potential of recycled poly(ethylene terepthalate) (rPET) as a well‐defined reinforcing material for the in situ microfibrillar‐reinforced composite (iMFC) was investigated in comparison with that of liquid crystalline polymer (LCP). Each dispersed phase (LCP or rPET) was melt blended with high density polyethylene (PE) by using extrusion process. The rheological behavior, morphology, and the thermal stability of LCP/PE and rPET/PE blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of LCP or rPET into PE significantly improved the processability. A potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as‐extruded strand. Although the viscosity ratio of the rPET/PE system was lower than that of the LCP/PE blend system, most rPET domains appeared as small droplets. An addition of LCP and rPET into the PE matrix improved the thermal resistance significantly in air but not in nitrogen. The obtained results suggested the high potential of rPET as a processing aid and good thermally resistant material similar to LCP. Copyright © 2009 John Wiley & Sons, Ltd.     

The structure and physical properties of in situ composites based on semiflexible thermotropic liquid crystalline copolyesteramide and poly(butylene terephthalate)

Liquid crystalline polymer–poly(butylene terephthalate) (LCP/PBT) blends were prepared by melt mixing. The LCP employed was a thermotropic copolyesteramide based on 30 mol % of p‐amino benzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The thermal, dynamic mechanical and rheological properties, morphology, and crystal structure of LCP/PBT blends were studied. The results showed that the semiflexible ABA30/PET LCP is miscible in the melt state with PBT, and they are partial miscible in the solid state. Differential scanning calorimetric measurements showed that the introduction of the semiflexible LCP into LCP/PBT blends retards the crystallization rate of PBT. However, the LCP dispersed phase acted as the sites for the nucleation of spherulites and enhance the degree of crystallinity of PBT. Hot‐stage optical microscopy examination revealed that the LCP microfibers with random orientation are dispersed in the PBT matrix of compression molded LCP/PBT blends. Under the application of a shearing force, the LCP domains in the PBT matrix tended to deform into microfibers, and to orient themselves along the flow direction. The formation of microfibers resulted in an increase of the storage modulus. The torque measurements indicated that the melting viscosity of the LCP/PBT blends is much lower than that of the pure PBT. Finally, the wide‐angle X‐ray diffraction patterns indicated that PBT shows no structural change with the incorporation of LCP, but the apparent crystal sizes of several diffraction planes change significantly. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 403–414, 2000     

Reactive compatibilization of polyolefin/PET blends by melt grafting with glycidyl methacrylate

The melt free radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) was carried out in Brabender internal mixer. The GMA content of the grafted HDPE (HDPE‐g‐GMA) was determined through FTIR by means of a calibration curve. The influence of reaction procedure, radical initiator concentration and addition of a co‐monomer (styrene) on the grafting efficiency was examined. Blends of poly(ethylene terephthalate) (PET) with HDPE and HDPE‐g‐GMA (75/25 w/w) were prepared by melt mixing in internal mixer. The morphology of the blends was then analysed by SEM microscopy. PET/HDPE‐g‐GMA blends displayed improved phase dispersion and interfacial adhesion as compared to unfanctionalized PET/HDPE blend.     

Flory-huggins interaction parameters of LCP/thermoplastic blends measured by DSC analysis

Liquid crystalline polymer/polyamide 66 (LCP/PA66) and LCP/poly(butyl terephthalate) (LCP/PBT) blends were compounded using a Brabender Plasticorder equipped with a mixing chamber. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30 mol% of p-amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). The Flory-Huggins interaction parameters (χ12) of the LCP/ PA66 and LCP/PBT blends are estimated by melting point depression from DSC measurement. The results indicate that c12 values all are negative for LCP/PA66 and LCP/PBT blends, and when the LCP content in these blends is more than 10 mass%, the absolute value of χ₁₂ decreases. Thereby, we can conclude that LCP/PA66 and LCP/PBT blends are fully miscible in the molten state, the molecular interaction between the LCP and PA66 is stronger than that between LCP and PBT. As the LCP content in LCP/PA66 and LCP/PBT blends is more than 10 mass%, the molecular interaction between LCP and matrix polymer decreases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Properties and Morphology of Liquid Crystalline Copolyester and Polyester Elastomer Blends

Abstract

Polyester elastomer (PEL) blends having a hard segment of polyester (PBT), soft segment of polyether (PTMG), and a liquid crystalline copolyester (LCP), poly(benzoate-naphthoate) were prepared with a twin-screw extruder. Test specimens for thermal properties were prepared by injection molding. Rheological properties and morphology were investigated by Instron capillary rheometer (ICR) and scanning electron microscopy (SEM). Thermal properties of the LCP/PEL blends were investigated by DSC, dilatometer, heat deflection temperature tester, and a Rheovibron viscometer. DSC study revealed a partial miscibility between LCP and PEL. It was found that the LCP acted as a nucleating agent for the crystallization of PEL in the LCP/PEL blends. The dimensional and thermal stability of the blends were increased by increasing the LCP cont-ent. The storage modulus (E' was improved by increasing the LCP content. The blend viscosity showed a minimum value at 5 wt% of LCP which increased by increasing the LCP content above 5 wt% of LCP The morphology of the LCP/PEL blends showed poor interfacial adhesion between the two phases, and the fibrillar structure of LCP phase in the matrix was affected by the LCP content, shear rate, and extrusion temperature. The morphology of the blends was found to be affected by their compositions and processing conditions.     

Effect of organoclay loading and electron beam irradiation on the physico‐mechanical properties of low‐density polyethylene/ethylene‐vinyl acetate blend

The influence of electron beam (EB) irradiation and organoclay (OC) loading on the properties of low‐density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) blends was investigated. The samples were subjected to the EB irradiation with the dose values of 50 and 250 kGy. X‐ray diffraction (XRD), gel content, mechanical, thermal, and electrical properties were utilized to analyze the characteristics of the LDPE/EVA blends with and without OC at different irradiation dosages. Gel content analysis showed that the OC promotes considerably the insoluble part so that the LDPE/EVA blends filled with OC become fully crosslinked at 250 kGy; possibly through the formation of further crosslinks between OC and polymer chains. The samples irradiated by EB showed enhanced mechanical properties due to the formation of three‐dimensional networks. In addition, thermogravimetric analysis indicated that combined OC loading and radiation‐induced crosslinking improved thermal stability of LDPE/EVA blends considerably. Copyright © 2011 John Wiley & Sons, Ltd.     

Morphology and thermal properties of a PC/PE blend with reactive compatibilization

Reactive compatibilization of immiscible polymers is becoming increasingly important and hence a representative study of a polycarbonate/high density polyethylene (PC/HDPE) system is the focus of this paper. A grafted copolymer PC‐graft‐ethylene‐co‐acrylic acid (PC‐graft‐EAA) was generated as a compatibilizer in situ during processing operation by ester and acid reaction between PC and ethylene‐acrylic acid (EAA) in the presence of the catalyst dibutyl tin oxide (DBTO). As the polyethylene (PE) matrix does not play any part during the synthesis of the copolymer and since PC and EAA are also immiscible, to simplify the system, the influence of this copolymer formation at the interface between PC and EAA on rheological properties, phase morphology, and crystallization behavior for EAA/PC binary blends was first studied. The equilibrium torque increased with the DBTO content increasing in EAA/PC blends on Haake torque rheometer, indicating the in situ formation of the graft copolymer. Scanning electron microscopy (SEM) studies of cryogenically fractured surfaces showed a significant change at the distribution and dispersion of the dispersed phase in the presence of DBTO, compared with the EAA/PC blend without the catalyst. Differential scanning calorimetry (DSC) studies suggested that the heat of fusion of the EAA phase in PC/EAA blends with or without DBTO reduced with the formation of the copolymer compared with pure EAA. Then morphological studies and crystallization behavior of the uncompatibilized and compatibilized blends of PC/PE were studied as functions of EAA phase concentration and DBTO content. Morphological observations in PC/PE blends also revealed that on increasing the EAA content or adding the catalyst DBTO, the number of microvoids was reduced and the interface was intensive as compared to the uncompatibilized PC/PE blends. Crystallization studies indicated that PE crystallized at its bulk crystallization temperature. The degree of crystallinity of PE phase in PC/PE/EAA blends was also reduced with the addition of EAA and DBTO compared to the uncompatibilized blends of PC/PE, indicating the decrease in the degree of crystallinity was more in the presence of PC‐graft‐EAA. Copyright © 2007 John Wiley & Sons, Ltd.     

Orientation and mechanical properties of PBT and its blends with a liquid-crystalline copolyester

Blends of poly (butylene terephthalate) (PBT) and a liquid-crystalline copolyester (60 mol % poly(p-hydroxy benzoic acid)/40 mol % polyethylene terephthalate) (LCP) were prepared in the melt state. The investigation of mechanical properties indicated that, for the processing conditions used, neither the addition of up to 30 wt % LCP to PBT nor the cooling history affected significantly the tensile modulus E. For oriented specimens, a marked improvement of E was obtained for all the blends, and increased with the LCP content. This improvement was more marked for slowly cooled samples. X-ray diffraction was used to quantify the orientation of the crystalline PBT and liquid-crystalline LCP phases. It was shown that neither the thermal history nor the presence of up to 30 wt % LCP affected the orientation behavior of the PBT crystalline phase. For the LCP phase, measurements were not possible for concentrations lower than 10 wt %, and were more difficult and less precise than for PBT. Nevertheless, it was possible to show that a better orientation was obtained for the slowly cooled samples and for higher concentrations of LCP in the blends. This correlated with the enhancement of mechanical properties observed for the oriented samples.     

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     

Effects of different types of polyethylene on the morphology and properties of recycled poly(ethylene terephthalate)/polyethylene compatibilized blends

Recycled poly(ethylene terephthalate) (R‐PET) was blended with four types of polyethylene (PE), linear low density polyethylene (LLDPE; LL0209AA, Fs150), low density polyethylene (LDPE; F101‐1), and metallocene‐LLDPE (m‐LLDPE; Fv203) by co‐rotating twin‐screw extruder. Maleic anhydride‐grafted poly(styrene‐ethylene/butyldiene‐styrene) (SEBS‐g‐MA) was added as compatibilizer. R‐PET/PE/SEBS‐g‐MA blends were examined by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and mechanical property testing. The results indicated that the morphology and properties of the blends depended to a great extent on the miscibility between the olefin segments of SEBS‐g‐MA and PE. Due to the proper interaction between SEBS‐g‐MA and LDPE (F101‐1), most SEBS‐g‐MA, located at the interface between two phases of PET and LDPE to increase the interfacial adhesion, lead to better mechanical properties of R‐PET/LDPE (F101‐1) blend. However, both the poor miscibility of SEBS‐g‐MA with LLDPE (LL0209AA) and the excessive miscibility of SEBS‐g‐MA with LLDPE (Fs150) and m‐LLDPE (Fv203) reduced the compatibilization effect of SEBS‐g‐MA. DSC results showed that the interaction between SEBS‐g‐MA and PE obviously affected the crystallization of PET and PE. DMA results indicated that PE had more influence on the movement of SEBS‐g‐MA than PE did. Copyright © 2010 John Wiley & Sons, Ltd.     

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…     

Oxazoline functionalization of polyethylenes and their blends with polyamides and polyesters

The compatibilization of blends of polyamide‐6 (PA6) with linear low density polyethylene (LLDPE) and of poly(ethylene terephthalate) (PET) with high density polyethylene (HDPE), by functionalization of the polyethylenes with oxazoline groups was investigated. Chemical modification of LLDPE and HDPE was carried out by melt free radical grafting with ricinoloxazoline maleinate. Blends preparation was made either with a two‐steps procedure comprising functionalization and blending, and in a single step in which the chemical modification of polyethylene with the oxazoline monomer was realized in situ, during blending. The characterization of the products was carried out by FTIR spectroscopy and scanning electron microscopy (SEM). The rheological and mechanical properties of the blends were also investigated. The results show that functionalization of the polyethylenes can be achieved by melt blending with ricinoloxazoline maleinate even in the absence of free radical initiators. The compatibilization of the blends enhances the dispersion of the minor phase significantly, increases the melt viscosity, and improves the mechanical properties. The one‐step preparation of the compatibilized blends was also found to be effective, and is thought to be even more promising in view of commercial application.     

Microphase separation in polybenzoxazine thermosets containing benzoxazine-terminated poly(ethylene oxide) telechelics

Benzoxazine-terminated poly(ethylene oxide) telechelics (Ba-terminated PEO) was synthesized and incorporated into polybenzoxazine to obtain the nanostructured thermosets. The morphology of the thermosets was investigated by means of atomic force microscopy (AFM), small angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA). The formation of the nanophase structures in the thermosetting composites was addressed on the basis of the mechanism of reaction-induced microphase separation (RIMPS), which was in marked contrast to the case of the binary thermosetting blends of polybenzoxazine with hydroxyl-terminated poly(ethylene oxide). The occurrence of RIMPS resulted from the copolymerization reaction of the end groups of Ba-terminated PEO telechelics with the precursor of thermosetting matrix (i.e., benzoxazine), which suppressed the occurrence of the macroscopic phase separation. It was found that the formation of the nanostructures has a significant effect on the melting behavior of PEO in the thermosets, thermal transition properties of the PBZ thermosets.     

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

聚丙烯多相体系中β晶的研究进展

综述了近年来聚丙烯(PP)基多相体系,如PP/弹性体(橡胶)、PP/聚乙烯(PE)、PP/对苯二甲酸乙二脂(PET)、PP/聚酰胺(PA)等共混体系和PP/CaCO3、PP/滑石粉、PP/蒙脱土(MMT)以及PP与其它无机物的复合体系中聚丙烯β晶的研究进展,阐述了在这些聚丙烯基共混和复合体系中影响聚丙烯β晶生成的因素、聚丙烯β晶的生成机理以及聚丙烯β晶对多相体系结构和性能的影响,并对富含β晶的聚丙烯(PP)基多相体系的研究和应用的发展趋势进行了展望。     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

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.     

Preparation and characterization of glass fiber–reinforced polyethylene terephthalate/linear low density polyethylene (GF‐PET/LLDPE) composites

Polyethylene terephthalate (PET) was melt blended with linear low density polyethylene (LLDPE) and subsequently compounded with glass fibers (GF) as reinforcements at percentages ranging from 15 to 45 wt% of LLDPE and 5 to 30 wt% of GF. Thermal, morphological, and mechanical properties of the prepared composites were investigated. It was found that compounding PET/LLDPE blends with GF would be beneficial in producing composites that are thermally stable with good mechanical properties. For example, the impact strength of the composites containing 85/15 wt% (PET/LLDPE) at relatively high loading of GF, ie, from 15 to 30 wt%, was higher than that of the GF‐reinforced neat PET. When increasing the percentage of LLDPE in the composites, the impact strength increased with increasing GF content, and this was also better than that of GF‐reinforced PET whose impact strength drastically decreased upon increasing the GF%. The improvement in mechanical properties of the composite, we suggest, should be correlated with the morphologies of the composites where the visualized interface adhesion tended to be better at higher loadings of both LLDPE and GF.     

Influence of Talc and SEBS-g-MA on PP/SEBS-g-MA/Talc Composites under Gamma Irradiation Sterilization Conditions

Among thermoplastics, polypropylene is outstanding with respect to its attractive combination of low cost, low weight, heat distortion temperature above 100°C, and extraordinary versatility in terms of properties and applications. With the appropriate modification, it is possible to improve the existing properties of the polypropylene, or even obtain the new ones. As a result of its originally superior properties, polypropylene is commonly used in medical purposes, where it has to undergo the process of sterilization beforehand. The sterilization of the polypropylene in medicine is most often being carried out with low dose of gamma irradiation, which can influence the changes of properties of both the polymeric matrix and modifiers. Therefore, the purpose of our research work was to determine the mechanical properties of unirradiated and gamma irradiated isotactic polypropylene (iPP) composites with talc filler and poly-(styrene-b-ethylene-co-butylene-b-styrene) block copolymer, grafted with maleic anhydride (SEBS-g-MA) as elastomeric modifier, as well as of corresponding binary blends. Unirradiated and gamma irradiated composites and blends were characterized by tensile measurements, measurements of notched impact strength and FTIR spectroscopy. The effects of composition and gamma irradiation on the properties of the iPP composites and blends are discussed, with emphasis on the study of the stabilizing effect of talc in irradiated iPP composites.     

用超临界CO_2制备微孔聚苯乙烯/热致液晶聚合物原位复合材料

微孔聚合物是80年代初发明的一种新型多孔材料,其特征为:泡孔直径1～10 μm,泡孔密度109～1012cells/cm3,相对密度0.05～0.95.具有缺口冲击强度高、韧性高、比强度高、疲劳寿命长、热稳定性高、介电常数低和导热系数低等优异性能.同时,制备微孔聚合物使用无公害、易回收的CO2和N2替代对臭氧层有害的氯氟烃(氟利昂)和易燃的碳氢化合物等作为发泡剂,是一种新型绿色材料[1].在微孔聚合物中使用超临界流体是90年代初提出的新方法[2～4],可缩短加工时间,同时制得泡孔直径更小、泡孔密度更大的微孔材料.目前研究中,对聚合物多相体系的研究报道很少,只有HIPS[5]、PE/iPP[6]和PVC/木纤维复合材料[7]等少数体系的报道,而聚合物多相体系的研究是材料科学的主要研究领域.可以预见,加入少量第二组分的共混物为基体的微孔材料可以达到更为优异的性能.本工作选择聚苯乙烯与热致液晶聚合物的原位复合材料为研究对象,采用超临界CO2快速降压法[3]制备微孔材料.在前期工作中,报道了该材料是一种综合了液晶聚合物的高强度和聚苯乙烯微孔材料轻质、高抗冲、保温隔音性能的具有仿生结构的新型复合材料[8].本文在此基础上,进一步研究热致液晶聚合物的加入对微孔结构的影响以及界面相容剂在微孔成型中的作用.