Crystallization behavior of polypropylene/polycarbonate blends

Crystallization behavior and morphology of polypropylene (PP)/polycarbonate (PC) blends have been studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). In the study of non-isothermal crystallization of the blends, the phenomenon of multiple crystallization peaks of PP/PC blends was related to the blend morphology in which PP was the dispersed phase as small droplets in the PC matrix. The phenomenon of a single crystallization peak of the PP/PC blends was related to the blend morphology in which PP was a continuous phase; in that case the crystallization peak temperatures of the blends were higher than that of the PP. The isothermal crystallization kinetics of the PP and PP/PC (80/20) blend were described by the Avrami equation. The results showed that the Avrami exponent of the PP/PC (80/20) blend was higher than that of the PP, and the crystallization rate of the PP/PC (80/20) blend was faster than that of the PP. The crystallization rate of the PP and PP/PC (80/20) blend were calculated according to the Hoffmann theory. Both the PP and PP/PC (80/20) blend had maximum crystallization rates. The temperature at the maximum crystallization rate for the PP/PC (80/20) blend was higher than that of the PP.     

Enhanced mechanics in injection molded isotactic polypropylene/polypropylene random copolymer blends via introducing network-like crystal structure

The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene(i PP), polypropylene random copolymer(co-PP) and i PP/co-PP blends were investigated. Differential scanning calorimetry(DSC) and dynamic rheological analysis illustrated that i PP and co-PP were compatible in the blends and co-PP uniformly dispersed in the i PP phase. Polarizing optical microscope(POM) was adopted to observe the crystal size and morphology evolution. The results of mechanical properties and scanning electron microscopy(SEM) indicated that the crystal size of i PP in i PP/co-PP blends(10 wt% co-PP + 90 wt% i PP and 30 wt% co-PP + 70 wt% i PP) radically decreased after the incorporation of co-PP. During crystallization, the molecular chain segments of co-PP could penetrate i PP spherulites and form a network-like crystalline structure. The network-like crystal structure could effectively transmit stress and consume more energy to overcome intermolecular forces to resist stretching. In this way, the strength would improve to a certain degree. The impact fracture mechanism of i PP/co-PP blends is quasi ductile fracture by multiple crazes. Our work discovered that the blends containing 10 wt% and 30 wt% of co-PP exhibited prominent toughness and reinforcement.     

Experimental study of flow-induced crystallization in the blends of isotactic polypropylene and poly(ethylene-co-octene)

The crystallization behavior of the blends of isotactic polypropylene (iPP) and poly(ethylene-co-octene) (PEOc) under quiescent condition and shear flow were studied by differential scanning calorimetry (DSC) and rheology, respectively. The DSC curves of the iPP phase in the blends showed similar crystallization exothermic peaks to that of pure iPP itself, indicating that the addition of PEOc up to a percentage of 30 in weight almost had no influence on the crystallization behavior of iPP at quiescent condition. The rheological results of isothermal flow-induced crystallization (FIC) of iPP in the blends showed that the crystallization kinetics of iPP was enhanced with the increase of shear rate, similar to that of pure iPP, but the presence of PEOc enhanced the effect of shear on the crystallization kinetics of iPP significantly in the cases of shear rates larger than 0.2 s⁻¹, which was due to that PEOc played an important role to promote the nucleation of iPP. The rheological results also implied that the characteristic relaxation times of blends were longer than that of pure iPP during the FIC process, indicating a different relaxation mechanism which might be related to the occurrence of interface relaxation and chain relaxation of the PEOc phase in the blends.     

iPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为

用DSC、~(13)C-NMR、SEM和WAXD等方法研究了IPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为。实验结果表明,EPDM与PE组分的相容性优于与PP组分的相容性,多数EPDM分子链段能够分布在PE组分中;EPDM含量为15％时,共混物相容性最好,SEM照片呈现晶体微区的互连或网络状结构;随EPDM含量增加,总结晶度X_c减小,其中PE组分结晶度X_(cE)有较大幅度地降低,PP组分结晶度X_(cp)基本没有变化,这可以根据EPDM和PE、PP之间相容性的差异以及PE、PP两组分在冷却过程中不同的结晶行为来解释。     

Isothermal crystallization kinetics of AB2 hyper-branched polymer (HBP)-filled polypropylene (PP)

In this paper, the isothermal crystallization kinetics of pure polypropylene (PP) and AB₂ hyper-branched polymer (HBP)/PP blends have been investigated by differential scanning calorimetry (DSC). During isothermal crystallization, the crystallization rates of the blends are higher than those of PP. Furthermore, in the blends with different HBP contents, the value of t _1/2 became smaller with increasing HBP content; however, the crystallization rate of the blend decreased slightly when the content of HBP is 5 %. An increase in the Avrami exponent means the addition of HBP influences the mechanism of nucleation and the growth of PP crystallites. In addition, the crystallization activation energy of pure PP and HBP/PP blends were also discussed, and the result showed that the crystallization activation energy has decreased remarkably in HBP/PP blends.     

Thermal and structural studies of polypropylene blended with esterified industrial waste lignin

Microwave-assisted chemical modification of lignin was achieved through esterification using maleic anhydride. Modified lignin (ML) was blended in different proportions up to 25 mass% with polypropylene (PP) using Brabender electronic Plasticorder at 190 °C. The structural and thermal properties of blends were investigated by thermogravometric analysis (TG), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). TG analysis showed increased thermal stability of blends due to antioxidant property of ML, which opposed oxidative degradation of PP. DSC analysis indicted slight depression in a glass transition temperature and melting temperature of blends due to partial miscible blend behavior between PP and ML. All blends showed higher crystallization temperatures and continuously reducing percentage crystallinity with increasing ML proportion in the blends. WAXD analysis indicated that PP crystallized in β polymeric form in addition to α-form in the presence of ML. However, proportion of β-form did not show linear relation with increase in ML proportion, thus ML acts as β nucleating agent in the PP matrix. SEM analysis showed good dispersion/miscibility in PP matrix indicating modification in lignin is useful.     

FRACTIONATED CRYSTALLIZATION OF HDPE IN PS/POE/HDPE/SBS BLENDS

The fractionated crystallization behavior of the minor dispersed HDPE phase in PS/POE/HDPE/SBS quaternary blends was investigated by differential scanning calorimetry (DSC).Interestingly,we found that the fractionated crystallization behavior of HDPE was molecular weight dependent.At a fixed composition,HDPE with lower molecular weight showed more obvious fractionated crystallization behavior than HDPE with higher molecular weight.This was ascribed to a finer dispersion of HDPE with lower molecular weigh...     

聚丙烯/凹凸棒土纳米复合材料结晶形态和形貌研究

采用熔融共混的方法 ,制备聚丙烯 凹凸棒土纳米复合材料 .通过X射线衍射 (XRD)分析凹凸棒土在聚丙烯复合材料中晶面间距的变化以及对聚丙烯晶型的影响 ,结果表明凹凸棒土在复合材料中晶面间距没有变化 ;聚丙烯晶型没有发生变化但晶粒尺寸增加了 .用示差扫描量热法 (DSC)分析聚丙烯复合材料的结晶度的变化 ,发现凹凸棒土的加入使复合材料的结晶温度提高 ,结晶速率增大 ,结晶度增加 .用偏光显微镜(POM)观察凹凸棒土对聚丙烯球晶的影响 ,结果表明凹凸棒土的加入起到了成核剂的作用 ,使得聚丙烯球晶尺寸减小 ,当凹凸棒土的加入量到 10 %左右时 ,观察不到完整的球晶 .利用扫描电子显微镜 (SEM)和原子力显微镜 (AFM)观察凹凸棒土在聚丙烯中的分散 ,发现凹凸棒土在聚丙烯基体中分散比较均匀 ,但呈无序分布 .     

微层共挤出(PP+EVOH)/PP阻隔材料的结构与性能研究

利用微层共挤出技术制备了具有交替层状结构的(PP+EVOH)/PP复合材料,其中PP为聚丙烯,EVOH为乙烯-乙烯醇其聚物.通过扫描电子显微镜观察、气体渗透实验、差示扫描量热仪分析以及力学性能测试研究了微层共挤出复合材料的形态结构及其对复合材料气体阻隔性能、力学性能以及结晶性能的影响.研究结果表明,通过微层共挤出技术,PP层和(PP+EVOH)层沿挤出方向交替排列,EVOH在PP基体中的的分散形态由零维球形变为一维纤维状,进而演变为二维片状.这些形态导致微层共挤出材料的氮气渗透系数和断裂伸长率较普通共混物分别下降了两个数量级和提高了27倍,并且显著影响其结晶行为.当层数超过64层后,由于PP层减薄,界面增多,EVOH不仅对(PP+EVOH)层中PP相存在结晶成核作用,而且对PP层也有结晶成核作用.     

iPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为

 用DSC、¹³C-NMR、SEM和WAXD等方法研究了IPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为。实验结果表明,EPDM与PE组分的相容性优于与PP组分的相容性,多数EPDM分子链段能够分布在PE组分中;EPDM含量为15％时,共混物相容性最好,SEM照片呈现晶体微区的互连或网络状结构;随EPDM含量增加,总结晶度X_c减小,其中PE组分结晶度X_cE有较大幅度地降低,PP组分结晶度X_cp基本没有变化,这可以根据EPDM和PE、PP之间相容性的差异以及PE、PP两组分在冷却过程中不同的结晶行为来解释。     

Effect of melt temperature on the phase morphology, thermal behavior and mechanical properties of injection-molded PP/LLDPE blends

<正>The phase morphology and thermal behavior of various isotactic polypropylene(PP)/linear low density polyethylene(LLDPE) blends were investigated with aid of scanning electron microscopy(SEM) and differential scanning calorimetry(DSC),respectively.The effect of barrel(melt) temperature on the morphology,thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus,and the influence of LLDPE composition was also taken into account.It was found that the mechanical properties,especially the tensile ductility and the impact strength,were greatly affected by the processing temperature.The samples obtained at low temperatures had the highest elongation at break and impact strength,while those molded at high temperatures had the poorest toughness.Two reasons were responsible for that:first,the phase size in the samples increased with the processing temperature;second, possible orientation existed in the samples obtained at low processing temperatures.     

Crystallization behavior of dynamically cured polypropylene/epoxy blends

Dynamically cured polypropylene (PP)/epoxy blends compatibilized with maleic anhydride grafted PP were prepared by the curing of an epoxy resin during melt mixing with molten PP. The morphology and crystallization behavior of dynamically cured PP/epoxy blends were studied with scanning electron microscopy, differential scanning calorimetry, and polarized optical microscopy. Dynamically cured PP/epoxy blends, with the structure of epoxy particles finely dispersed in the PP matrix, were obtained, and the average diameter of the particles slightly increased with increasing epoxy resin content. In a study of the nonisothermal crystallization of PP and PP/epoxy blends, crystallization parameter analysis showed that epoxy particles could act as effective nucleating agents, accelerating the crystallization of the PP component in the PP/epoxy blends. The isothermal crystallization kinetics of PP and dynamically cured PP/epoxy blends were described by the Avrami equation. The results showed that the Avrami exponent of PP in the blends was higher than that of PP, and the crystallization rate was faster than that of PP. However, the crystallization rate decreased when the epoxy resin content was greater than 20 wt %. The crystallization thermodynamics of PP and dynamically cured PP/epoxy blends were studied according to the Hoffman theory. The chain folding energy for PP crystallization in dynamically cured PP/epoxy blends decreased with increasing epoxy resin content, and the minimum of the chain folding energy was observed at a 20 wt % epoxy resin content. The size of the PP spherulites in the blends was obviously smaller than that of PP. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1181–1191, 2004     

Crystallization,melting behavior,and morphology of PP/Novolac blends

The crystallization, melting behavior, and morphology of Polypropylene (PP) and PP/Novolac blends were studied by scanning electron microscopy, wide angle X‐ray diffraction, differential scanning calorimetry, and polarized optical microscope. The results showed that the crystallization of PP in PP/Novolac blends was strongly influenced by crystallization temperature, particles size of Novolac, crosslinking, and compatibilizer maleic anhydride‐grafted PP. The Novolac resin could not only affect the crystal structure, but also acted as effective nucleating agents, accelerating the crystallization of PP in the PP/Novolac blends. And the smaller the Novolac particles were, the more effective were the nucleating agent for PP crystallization. Avrami equation was used to analyze the isothermal crystallization kinetics of PP and PP/Novolac blends. The influences of curing and compatibilizer on the crystallization behavior of PP were rather complicated. The crystallization thermodynamics were estimated using the Hoffman theory. The incorporation of cured Novolac and compatibilizer evidently decreased the chain folding energy of PP. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3288–3303, 2006     

The crystallization characteristics of polypropylene and low ethylene content polypropylene copolymer with copolyesters

The crystallization characteristics of polypropylene (PP) and low ethylene content PP copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC). PP and PP copolymers was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 5 to 15 wt.%. All samples were prepared by solution blending in hot xylene solvent at 50 °C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PP and PP copolymers in a manner similar to that of a nucleating agent. The acceleration of crystallization rate was most pronounced in these blend systems with a maximum level at 5 wt.% of B28. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends.     

聚丙烯催化合金的结晶行为研究

近 1 0年来 ,Montell公司发展的聚丙烯催化合金 (Polypropylene catalloy,PP-c)技术受到广泛关注 .该技术采用具有特定结构的催化剂粒子 ,在适当的聚合条件下 ,得到具有一定大小、形状及内部形貌的聚合物粒子 .由 PP-c技术获得的材料性能可以在非常宽的范围内进行调节 ,其呈现出的高强度可以与工程塑料相比拟 ,柔性可以与聚乙烯相媲美 [1] .结晶性聚合物的结晶度、球晶尺寸等因素对其机械性能 ,尤其是冲击韧性具有重要的影响[2 ,3] .改性聚丙烯的结晶行为及其与物理机械性能之间的关系一直备受关注 .对于纯聚丙烯、聚丙烯与橡胶的共混物…     

Preparation and flammability of EPDM/PP/Mg(OH)2 dynamic vulcanizates

Magnesium hydroxide (MH) flame retardant dynamic vulcanized ethylene‐propylene‐diene terpolymer (EPDM)/polypropylene (PP) thermoplastic vulcanizates (TPVs) were prepared by a twin‐screw extruder. Influences of MH on their morphology, mechanical properties, flammability, and crystallization behavior have been investigated. Static tensile measurements exhibited that TPVs have higher mechanical properties than un‐vulcanized EPDM/PP/MH blends (UVBs). Scanning electron microscopy (SEM) studies showed that the formation of the larger‐size “micro‐encapsulated structure” where the MH aggregates were covered with a cross‐linked rubber phase improved the interaction between MH and polymer matrix. Results of limiting oxygen index (LOI) and microscale combustion calorimetry (MCC) confirmed that TPVs had superior fire‐resistant properties to UVBs. SEM images showed that more uniform and compact charred layers were generated in TPVs. The differential scanning calorimetry (DSC) results indicated that the crystallization behavior of the flame retardant TPVs changed marginally with increase in MH content. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystallization behavior and morphology of one-step reaction compatibilized microfibrillar reinforced isotactic polypropylene/poly(ethylene terephthalate) (<Emphasis Type="Italic">i</Emphasis>PP/PET) blends

One-step reaction compatibilized microfibrillar reinforced iPP/PET blends(CMRB) were successfully prepared through a "slit extrusion-hot stretching-quenching" process.Crystallization behavior and morphology of CMRB were systematically investigated.Scanning electronic microscopy(SEM) observations showed blurry interface of compatibilized common blend(CCB).The crystallization behavior of neat iPP,CCB,microfibrillar reinforced iPP/PET blend(MRB) and CMRB was investigated by differential scanning calorimetry(DSC) and polarized optical microscopy(POM).The increase of crystallization temperature and crystallization rate during nonisothermal crystallization process indicated both PET particles and microfibrils could serve as nucleating agents and PET microfibrils exhibited higher heterogeneous nucleation ability,which were also vividly revealed by results of POM.Compared with MRB sample,CMRB sample has lower crystallization temperature due to existence of PET microfibrils with smaller aspect ratio and wider distribution.In addition, since in situ compatibilizer tends to stay in the interphase,it could also hinder the diffusion of iPP molecules to the surface of PET phase,leading to decrease of crystallization rate.Two-dimensional wide-angle X-ray diffraction(2D-WAXD) was preformed to characterize the crystalline structure of the samples by injection molding,and it was found that well-developed PET microfibrils contained in MRB sample promoted formation ofβ-phase of iPP.     

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     

Fractional crystallization behavior of PCL and PEG in blends

The crystallization behavior of poly(e-caprolactone)/poly(ethylene glycol) (PCL/PEG) blend was investigated by differential scanning calorimetry (DSC) and polarized microscopy (POM). Individual phase transition peaks in the DSC curves for both PEG and PCL in all the polymer blends with different PCL contents were observed. The crystallization and melting peak temperatures of PEG were at 41 and 65°C, respectively; while the crystallization and melting temperatures of PCL located at 28 and 56°C, respectively. In-situ POM results demonstrated that spherulites crystalline morphology was formed for both PCL and PEG homopolymers. In PEG/PCL blend, however, both the phase separation morphology and spherulitic morphology can be observed. In blends with 30 or 50 wt % PCL, the PCL component formed dispersed phase and crystallized at lower temperature. However, in blends with 70% PCL, the phase inversion behavior occurred. The continuous PCL phase crystallized at 35°C, while the PEG dispersed phase crystallized at a lower temperature. Fractional crystallization behavior of PEG and PCL was controlled by temperature. The spherulites growth rate of PEG was greatly influenced by temperature, instead of the content of PCL component in the PCL/PEG blends.     

聚乳酸/羧基化聚丙烯共混物的形态与热性能研究

以扫描电子显微镜、热重分析仪、差示扫描量热仪、热台偏光显微镜分别研究了聚乳酸/羧基化聚丙烯共混体系的相形态、热性能和结晶形态.结果显示,共混物熔体冷却时,聚乳酸和羧基化聚丙烯均形成球晶,但羧基化聚丙烯球晶较大而十字消光较暗,聚乳酸球晶尺寸较小而十字消光较亮,且聚乳酸球晶产生规则的、不连续的同心环线——裂纹,裂纹厚度约为1~2μm,且裂纹内部有微纤存在.当聚乳酸含量≤50%时,由于聚丙烯上羧基的存在而使共混体系具有较好的相容性.共混物的热分解过程分为三个阶段,热分解温度的变化是聚丙烯上的羧基、聚乳酸和聚丙烯骨架分解三种机制共同作用的结果,少量聚乳酸能够明显提高共混物中聚丙烯上羧基的热稳定性.共混物中的羧基化聚丙烯组分可以发挥稀释剂的作用,大幅度降低了聚乳酸的冷结晶温度.聚乳酸含量≥50%时,共混熔体降温时DSC谱图中聚乳酸和羧基化聚丙烯分别结晶,而聚乳酸含量<50%时,只观察到羧基化聚丙烯的结晶行为.