Morphology and properties of isotactic polypropylene/poly(ethylene terephthalate) in situ microfibrillar reinforced blends: Influence of viscosity ratio

In situ microfibrillar reinforced blends based on blends of isotactic polypropylene (iPP) and poly(ethylene terephthalate) (PET) were successfully prepared by a “slit extrusion-hot stretching-quenching” process. Four types of iPP with different apparent viscosity were utilized to investigate the effect of viscosity ratio on the morphology and mechanical properties of PET/iPP microfibrillar blend. The morphological observation shows that the viscosity ratio is closely associated to the size of dispersed phase droplets in the original blends, and accordingly greatly affects the microfibrillation of PET. Lower viscosity ratio is favorable to formation of smaller and more uniform dispersed phase particles, thus leading to finer microfibrils with narrower diameter distribution. Addition of a compatibilizer, poly propylene-grafted-glycidyl methacrylate (PP-g-GMA), can increase the viscosity ratio and decrease the interfacial tension between PET and iPP, which tends to decrease the size of PET phase in the unstretched blends. After stretched, the aspect ratio of PET microfibrils in the compatibilized blends is considerably reduced compared to the uncompatibilized ones. The lower viscosity ratio brought out higher mechanical properties of the microfibrillar blends. Compared to the uncompatibilized microfibrillar blends, the tensile, flexural strength and impact toughness of the compatibilized ones are all improved.     

Transcrystalline Morphology of an in situ Microfibrillar Poly(ethylene terephthalate)/Poly(propylene) Blend Fabricated through a Slit Extrusion Hot Stretching‐Quenching Process

Summary: Isotactic poly(propylene) (iPP) transcrystallites are obtained in in situ microfibrillar polyethylene terephthalate (PET)/iPP blends during a slit extrusion‐hot stretching‐quenching process. Based on morphological information from X‐ray scattering and microscopy, three nucleation origins are proposed in microfibrillar reinforced blends under an elongational flow field: (a) the classical row nuclei model; (b) fiber nuclei; (c) nuclei induced by fiber assistant alignment. The last model provides a natural explanation for the case that transcrystallites only occur in some microfiber reinforced blends under flow rather than without the external field.

AFM image for the transcrystalline layer of the microfibrillar blend.     

间规聚苯乙烯/等规聚丙烯/间规聚苯乙烯-b-聚(1-丁烯)共混体系相容性

间规聚苯乙烯(sPS)的改性主要是对其增韧改性,提高其力学性能.sPS的化学改性已有较多文献报道[1,2].     

Morphology and nonisothermal crystallization of in situ microfibrillar poly(ethylene terephthalate)/polypropylene blend fabricated through slit‐extrusion,hot‐stretch quenching

This study describes the morphology and nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) in situ micro‐fiber‐reinforced blends (MRB) obtained via slit‐extrusion, hot‐stretching quenching. For comparison purposes, neat PP and PET/PP common blends are also included. Morphological observation indicated that the well‐defined microfibers are in situ generated by the slit‐extrusion, hot‐stretching quenching process. Neat iPP and PET/iPP common blends showed the normal spherulite morphology, whereas the PET/iPP microfibrillar blend had typical transcrystallites at 1 wt % PET concentration. The nonisothermal crystallization kinetics of three samples were investigated with differential scanning calorimetry (DSC). Applying the theories proposed by Jeziorny, Ozawa, and Liu to analyze the crystallization kinetics of neat PP and PET/PP common and microfibrillar blends, agreement was found between our experimental results and Liu's prediction. The increases of crystallization temperature and crystallization rate during the nonisothermal crystallization process indicated that PET in situ microfibers have significant nucleation ability for the crystallization of a PP matrix phase. The crystallization peaks in the DSC curves of the three materials examined widened and shifted to lower temperature when the cooling rate was increased. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 374–385, 2004     

In‐situ microfibrillar PET/iPP blend via slit die extrusion,hot stretching,and quenching: Influence of hot stretch ratio on morphology,crystallization, and crystal structure of iPP at a fixed PET concentration

The in situ microfibrillar blend of poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) was fabricated through a slit die extrusion, hot stretch, and quenching process. The morphological observation indicates that while the unstretched blend appears to be a common incompatible morphology, the hot stretched blends present PET in situ fibers whose characteristics, such as diameter and aspect ratio, are dependent on the hot stretching ratio (HSR). When the HSR is low, the elongated dispersed phase particles are not uniform at all. As the HSR is increased to 16.1, well‐defined PET microfibers were generated in situ, whose diameter is rather uniform and is around 0.6 ～ 0.9 μm. The presence of the PET phase shows significant nucleation ability for crystallization of iPP. Higher HSR corresponds to faster crystallization of the iPP matrix, while as HSR is high up to a certain level, its variation has little influence on the onset and maximum crystallization temperatures of the iPP matrix during cooling from melt. Optical microscopy observation reveals that transcrystalline layers form in the microfibrillar blend, in which the PET microfibers play as the center row nuclei. In the as‐stretched microfibrillar blends, small‐angle X‐ray scattering measurements show that matrix iPP lamellar crystals have the same orientation as PET lamella. The long period of lamellar crystals of iPP is not affected by the presence of PET micofibers. Wide‐angle X‐ray scattering reveals that the β phase of iPP is obtained in the as‐stretched blends, whose concentration increases with the increase of the HSR. This suggests that finer PET microfibers can promote the occurrence of the β phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4095–4106, 2004     

Effect of in situ poly(ethylene terephthalate) (PET) microfibrils on the morphological structure and crystallization behavior of isotactic polypropylene (iPP) under an intensive shear rate

The morphological structure and crystallization behavior of in situ poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) microparts prepared through micro‐injection molding are investigated using a polarized light microscope, differential scanning calorimeter, scanning electron microscope, and two‐dimensional wide‐angle X‐ray. Results indicate that both the shear effect and addition of PET fibers greatly influence the morphologies of the iPP matrix. Typical “skin‐core” and oriented crystalline structures (shish‐kebab) may simultaneously be observed in neat iPP and iPP/PET microparts. The presence of PET phases reveals significant nucleation ability for iPP crystallization. High concentrations of PET phases, especially long PET fibers, correspond to rapid crystallization of the iPP matrix. The occurrence of PET microfibrils decreases the content and size of β‐crystals; by contrast, the orientation degree of β‐crystals increases with increasing PET content in the microparts. This result suggests that the existence of the microfibrillar network can retain the ordered clusters and promote the development of oriented crystalline structures to some extent. Copyright © 2015 John Wiley & Sons, Ltd.     

Formation and morphology of cellulose acetate butyrate (CAB)/polyolefin and CAB/polyester in situ microfibrillar and lamellar hybrid blends

Cellulose acetate butyrate (CAB)/iPP (isotactic polypropylene), CAB/HDPE (high density polyethylene), CAB/PET (poly ethylene terephthalate), CAB/PTT (poly trimethylene terephthalate), CAB/PBT (poly butylenes terephthalate) and CAB/IPET-PEG (poly(ethylene terephthalate-co-isophthalate)-poly(ethylene glycol)) in situ microfibrillar and lamellar hybrid blends at a weight ratio of 80/20 were prepared by melt extrusion. Microfibrillar and lamellar hybrid morphologies of CAB/polyolefin and CAB/polyester blends under different force fields were investigated. The formation process of in situ microfibrillar and lamellar hybrid blends were analyzed and proposed.     

Simultaneously reinforce and toughen polypropylene by in‐situ introducing polylactic acid microfibrils

A petroleum‐based polymer, isotactic polypropylene (iPP), and a biodegradable polymer, poly(lactic acid) (PLA), were compounded and molded into parts through the micro‐injection technique. A systematic structural investigation indicated that the microfibrillation of PLA minor phase depended on the operation parameter of inter‐mixer, ie, rotor speed. The higher rotor speed, the lower viscosity ratio of the PLA/iPP pair was favorable for microfibrillation occurred during micro‐injection process. The PLA microfibrils with high aspect ratio was successfully introduced into iPP matrix, and the tensile strength and strain at break of iPP/PLA blends were simultaneously improved. This study suggests a promising method for designing special microfibrillar morphology in polymer blend by using conventional melt processing techniques.     

Effect of blending way on β-crystallization tendency of compatibilized β-nucleated isotactic polypropylene/poly(ethylene terephthalate) blends

The main purpose of this study is to investigate the β-crystallization tendency in the β-nucleated iPP blends. The β-nucleated iPP/compatibilizers blends, β-nucleated iPP/PET blends and its compatibilized versions with four kinds of compatibilizers (PP-g-MA, PP-g-GMA, POE-g-MA, and EVA-g-MA) were prepared by different blending ways. The effect of compatibilizers and blending ways on the non-isothermal crystallization and melting characteristics and the β-crystallization tendency of β-nucleated iPP blends were studied by differential scanning calorimetry. The relative content of the β-phase were characterised by the k _β values determined on the basis of the wide angle X-ray diffractogram. The results indicated that the β-crystallization tendency of β-nucleated iPP blends depends on the kinds of compatibilizer. Addition of PP-g-MA significantly reduced the β-crystallization tendency of β-nucleated iPP, while PP-g-GMA, POE-g-MA, and EVA-g-MA have little effect on it. In the compatibilized β-nucleated iPP/PET blends, the blending ways, which controlled the dispersion of β-nucleating agent, influences the β-crystallization tendency intensively. The high β-crystallization tendency and β-crystal content were obtained for compatibilized β-nucleated iPP/PET blends prepared firstly at high temperature and β-nucleating agent added into blends at low temperature; however, the type of compatibilizers has little effect on β-crystallization tendency and melting behavior of blends.     

PRELIMINARY INVESTIGATION ON THE MISCIBILITY OF ISOTACTIC POLYPROPYLENE （iPP） AND SYNDIOTACTIC POLYPROPYLENE （sPP） BLENDS

Experimental miscibility studies were performed on different compositions of iPP/sPP blends, where sPP has a low syndiotacticity （[rrrr] = 81%）. Combining optical microscopy, rheology, and solid state NMR spectroscopy, the miscibility of the blends was investigated at different scales in the traditionally thought to be ＂immiscible＂ iPP/sPP blends. For the composition of iPP/sPP （90/10） blend, it shows to be miscible in the melt, and furthermore, the existence of intermolecular chain interactions between sPP and iPP components was detected in the solid state.     

等规聚丙烯/二元乙丙橡胶合金相分离对结晶动力学的影响

用小角激光光散射(SALLS)、相差显微镜(PCM)、示差扫描量热仪(DSC)和偏光显微镜(POM)研究了聚丙烯/二元乙丙橡胶(iPP/EPR)共混体系的相分离行为和等温结晶行为.发现iPP/EPR(50/50,W/W)发生的液-液相分离遵循spinodal机理.通过Cahn-Hilliard方程求得了不同实验温度下iPP/EPR的表观扩散系数(Dapp)以及spinodal温度(Ts).考察了不同相分离程度的iPP/EPR体系结晶动力学,发现延长相分离时间(tps)或提高相分离温度(Tps)均会导致半结晶时间(t1/2)增大,即结晶速率降低.这被归于EPR成核作用的降低.动力学分析结果表明Avrami模型适用于描述该体系的等温结晶过程,其结晶机理基本不受相分离程度的影响,结晶均以瞬时成核和三维生长为主.     

Rheological behavior of PET/HDPE in situ microfibrillar blends: Influence of microfibrils' flexibility

Poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) in situ microfibrillar reinforced blends were prepared via a slit die extrusion‐hot stretch‐quenching process. The in situ PET microfibrils contain various contents of a segmented thermoplastic elastomer, Hytrel 5526 (HT), hence having different flexibility as demonstrated by dynamic mechanical analysis. It is interesting that the simple mixing leads to nanoscale particles of the HT phase in PET phase, and the size of the HT particles is almost independent of the HT concentration, as observed from the scanning electron microscope micrographs which show that the microfibrils with different HT concentrations have almost the same diameter and smooth surfaces. The static rheological results by an advanced capillary rheometer show that the entrance pressure drop and the viscosity of the microfibrillar blends both reduced with increasing the microfibrils' flexibility. Furthermore, the data obtained by the temperature scan of the PET/HT/HDPE microfibrillar blends through a dynamic rheometer indicates that the more flexible microfibril leads to lower melt elasticity and slightly decreases the viscosities of blends, presenting a consistent conclusion about influences of the microfibrils' flexibility on the rheological behavior from the static rheometer measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1205–1216, 2007     

Polypropylene/poly(butyl methacrylate) blends prepared by diffusion and subsequent polymerization of butyl methacrylate in isotactic polypropylene pellets

Polypropylene/poly(butyl methacrylate)(PP/PBMA) blends were prepared by diffusion and subsequent polymerization of butyl methacrylate(BMA) in commercial isotactic polypropylene(iPP) pellets.The diffusion kinetics,diametrical distribution of PBMA in a pellet and phase morphology of a typical PP/PBMA blend were investigated.     

Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS‐graft‐PET copolymer on morphology and crystallization behavior

The morphology and crystallization behavior of poly(phenylene sulfide) (PPS) and poly(ethylene terephthalate) (PET) blends compatibilized with graft copolymers were investigated. PPS‐blend‐PET compositions were prepared in which the viscosity of the PPS phase was varied to assess the morphological implications. The dispersed‐phase particle size was influenced by the combined effects of the ratio of dispersed‐phase viscosity to continuous‐phase viscosity and reduced interfacial tension due to the addition of PPS‐graft‐PET copolymers to the blends. In the absence of graft copolymer, the finest dispersion of PET in a continuous phase of PPS was achieved when the viscosity ratio between blend components was nearly equal. As expected, PET particle sizes increased as the viscosity ratio diverged from unity. When graft copolymers were added to the blends, fine dispersions of PET were achieved despite large differences in the viscosities of PPS and PET homopolymers. The interfacial activity of the PPS‐graft‐PET copolymer appeared to be related to the molecular weight ratio of the PPS homopolymer to the PPS segment of the graft copolymer (M_H/M_A). With increasing solubilization of the PPS graft copolymer segment by the PPS homopolymer, the particle size of the PET dispersed phase decreased. In crystallization studies, the presence of the PPS phase increased the crystallization temperature of PET. The magnitude of the increase in the PET crystallization temperature coincided with the viscosity ratio and extent of the PPS homopolymer solubilization in the graft copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 599–610, 2000     

Crystallization and phase morphology of injection‐molded isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends

The crystallization and phase morphology of the injection‐molded isotactic polypropylene (iPP)/syndiotactic polypylenen (sPP) blends were studied, focusing on the difference between the skin layer and core layer. The distribution of crystallinity of PPs in the blends calculated based upon the DSC results shows an adverse situation when compared with that in the neat polymer samples. For 50/50 wt % iPP/sPP blend, the SEM results indicated that a dispersed structure in the skin layer and a cocontinuous structure in the core layer were observed. A migration phenomenon that the sPP component with lower crystallization temperature and viscosity move to the core layer, whereas the iPP component with higher crystallization temperature and viscosity move to the skin layer, occurred in the iPP/sPP blend during injection molding process. The phenomenon of low viscosity content migrate to the low shear zone may be due to the crystallization‐induced demixing based upon the significant difference of crystallization temperature in the sPP and iPP. This migration caused the composition inhomogeneity in the blend and influenced the accuracy of crystallinity calculated based upon the initial composition. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2948–2955, 2007     

The effect of various compatibilizers on thermal,mechanical, and morphological properties of polystyrene/polypropylene blends

The effects of various compatibilizers on thermal, mechanical and morphological properties of 50/50 polypropylene/polystyrene blends were investigated. Various compatibilizers, polystyrene-(ethylene/butylenes/ styrene) (SEBS), ethylene vinyl acetate (EVA), polystyrene-butylene rubber (SBR) and blend of compatibilizers SEBS/PP-g-MAH, EVA/PP-g-MAH, and SBR/PP-g-MAH were used. Differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray scattering, scanning electron microscopy, microhardness, and Izod impact strength were adopted. It was found that the influence of various compatibilizers was appeared on all the properties studied. The properties of the blends compatibilized with SEBS, EVA, and SBR are very distinct from those of blends compatibilized with blend of compatibilizers. Results show that compatibilized blends with the blend of compatibilizers EVA/PP-g-MAH, SBR/PP-g-MAH, and SEBS/PP-g-MAH or SBR were relatively more stable than the uncompatibilized blend and blend compatibilized with SEBS or EVA. The compatibilizer does not only reduce the interfacial tension or increase the phase interfacial adhesion between the immiscible polymers, but greatly affects the degree of crystallinity of blends.

     

Compatibility Study of Blends of Acrylic Rubber (ACM), Poly(ethyleneterephalate) (PET), and Liquid Crystalline Polymer (LCP)

The ternary blends of acrylate rubber (ACM), poly(ethyleneterephalate) (PET), and liquid crystalline polymer (LCP) were prepared by varying the amount of LCP, but fixing the ratio of ACM and PET using melt mixing procedure. The compatibility behavior of these blends was investigated with infrared spectroscopy (IR), differential scanning calorimetry (DSC), and dynamic mechanical analyzer (DMA). The IR results revealed the significant interaction between the blend components. Glass transition temperature (T_g) and melting temperature (T_m) of the blends were affected depending on the LCP weight percent in the ACM/PET, respectively. This further suggests the strong interfacial interactions between the blend components. In the presence of ACM, the nucleating effect of LCP was more pronounced for the PET. The thermogravimetric (TGA) study shows the improved thermal stability of the blends.     

iPS－b－iPP共聚物对iPS／iPP共混物的性能和形态影响的研究

报道了苯乙烯－丙烯等规嵌段共聚物（ｉＰＳ－ｂ－ｉＰＰ）增溶作用及ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ三组分共混体系微观形态和力学性能的研究结果。ｉＰＳ－ｂ－ｉＰＰ的加入明显地改善了ｉＰＳ／ｉＰＰ二组分共混物的力学性能;共聚物含量超过１５％时,三组分共混物的抗冲击强度超过ＮＩＰＳ的抗冲击强度,并具有较高的耐热性。ＳＥＭ结果表明,ｉＰＳ－ｂ－ｉＰＰ在ｉＰＳ／ｉＰＰ共混中起到了相分散和相间“偶联”作用,并降低了共混体系的微相尺寸和增加相间相互作用或粘附性。ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ共混合金具有高的软化温度和刚性。     

Shear‐Induced Crystallization in a Blend of Isotactic Poly(propylene) and Poly(ethylene‐co‐octene)

Summary: Shear‐induced crystallization in a blend of isotactic poly(propylene) and poly(ethylene‐co‐octene) (iPP/PEOc) has been investigated by means of in‐situ optical microscopy and a shear hot stage under various thermal and shear histories. Cylindrites are observed after shear in the phase‐separated iPP/PEOc blends for the first time. The nuclei (shish) come from the orientation of the entangled network chains, and the relationship between the shear rate and the network relaxation time of the oriented iPP chains is a very important factor that dominates the formation of the cylindrites after liquid‐liquid phase separation. The cylindrites can grow through phase‐separated domains with proper shear rate and shear time. In addition, the number of spherulites increases with shear rate, which is consistent with the notion of fluctuation‐induced nucleation/crystallization.

Phase‐contrast optical micrograph of the iPP/PEOc = 50/50 (wt.‐%) sample sheared during cooling with shear rate of 10 s⁻¹ and isothermally crystallized at 140 °C for 142 s after isothermal annealing at 170 °C for 420 min. The shear time is 180 s.     

Thermal and spectroscopy studies on ternary miscibility and phase behavior in blends comprising poly(4‐vinyl phenol) and two aryl polyesters

Thermal analysis and Fourier transform infrared spectroscopy characterizations were performed on three ternary blend systems that comprise poly(4‐vinyl phenol) (PVPh) and any two of the three homologous aryl polyesters [poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT)]. Although PVPh is miscible with any one of the polyesters in forming a binary blend system, miscibility in ternary systems by introducing one more polymer of different structures to the blend system is not always expected. However, this study concludes that miscibility does exist in all these three ternary blends of all compositions investigated. Reasons and factors for such behavior were probed. Quantitative interactions in the ternary blend system were also estimated. The overall interaction energy density (B) by analysis of melting point depression for the PBT/PVPh/PET ternary blend system led to a negative value (B = −5.74 cal/cm³). Similarly, T_g‐composition analyses were performed on two other ternary blend systems, PET/PVPh/PTT and PTT/PVPh/PBT. Comparison of the qualitative results showed that the interaction energy densities in the other two ternary blend systems are similarly negative and comparable to the PBT/PVPh/PET ternary blend system. The Fourier transform infrared spectroscopy results also support the qualitative findings among these three ternary blend systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1339–1350, 2006