Rayleigh散射研究部分相容聚苯乙烯／顺丁橡胶合金相结构

用光散射在线采集与分析方法完成了熔融混炼过程中非相容高分子共混物的形态结构分析。选择了聚苯乙烯／顺丁橡胶合金体系；使用了小角前向光散射和小角背散射(在线)技术，用Debye-Bueche光散射理论的结构参数如相关距离ac、平均弦长l、旋转半径Rg和积分不变量Q表征了共混物中分散相尺度和均匀性，讨论了合金体系的相容性。用扫描电子显微镜测定了共混物中分散相尺寸，并与光散射的结果进行了比较。ac、l和Rg的变化规律与显微镜的结果是一致的。用积分不变量Q研究了共混物的均匀性。     

聚苯乙烯／顺丁橡胶合金相结构的X光小角散射研究

采用X光小角散射法研究了聚苯乙烯/顺丁橡胶合金体系的相结构及相容性。用Debye-Bueche光散射理论的结构参数，如相关距离ac．平均弦长l、旋转半径Rg和积分不变量Q等表征了合金中分散相的尺度及其分布在连续相中的均匀性，用扫描电子显微镜(SEM)定量测定了合金中分散相尺寸的大小和尺寸分布。结果表明：上述各光散射结构参数均可以在纳米尺度范围内表征合金体系的相结构，积分不变量Q可以表征合金体系相结构的均匀性。聚苯乙烯(PS)/颐丁橡胶(PB)合金是典型的不相容体系，无论PB还是PS处于稀相时均不呈现分子分散。     

小角光散射研究PP／EOC增韧体系

以乙烯 -1-辛烯共聚物 (EOC)对聚丙烯 (PP)进行增韧改性 ,通过小角光散射测取到不同配比的共混物的相关距离 αc、积分不变量Q ,进一步求得分散相粒子表面间距 τ和过渡层厚度d ,研究 τ与材料冲击性能之间的关系 ,发现存在一个临界值 τc与材料的脆韧转变点相对应。当 τ≤τc 时 ,材料是韧性的 ;当 τ>τc 时 ,材料呈脆性。在共混过程中 ,τ随共混时间增加逐渐减小 ,在共混的中后期趋于稳定 ;随 τ值的减小 ,材料冲击强度增加。过渡层厚度d随EOC含量的递增逐渐增大 ,对应材料的冲击强度增加。     

相差显微镜研究PP/POE共混体系的相分散行为

采用密炼机在线取样,相差显微镜拍照研究乙烯-1-辛烯共聚物（POE）在聚丙烯（PP）中的相分散行为。由于相差显微镜图样经过傅里叶变换得到的图样与小角光散射图样有很好的对应关系,本文引入光散射试验中的结构参数-分散相平均粒径αc2以表征PP／POE共混体系的相分散行为。根据αc2值随时间的变化,把PP／POE共混的相分散过程分为分散初期,分散中期,分散后期3个阶段。按照αc2值与组成的关系,可以看出PP／POE（POE质量分数为30％）,体系开始出现双连续相结构．与扫描电镜结果相一致。     

高分子共混物的相结构对力学性能的影响

本文以聚丙烯 尼龙1010(PP PA1010)共混体系为模型研究了高分子共混物的微观相结构对宏观力学性能的影响,并通过微观力学模型来预测共混物的拉伸强度。通过光散射试验和扫描电镜结果讨论了两相平均弦长比(L1 L2)以及分散相的质心相关距(D)与拉伸性能的关系。结果表明,当分散相一定时,拉伸强度随两相相对尺寸的增大和分散相颗粒相关性的减弱而减小。理论计算的分散相最小体积分数与相形貌观察的结果非常接近,添加增容剂的体系,由于改善了界面粘合,使理论预测值与试验结果很好的吻合。     

高聚物共混改性后的透明性

本文阐述了影响聚合物共混两相体系透明性的因素。从复杂的两相聚合物混合体系的光散射中,通过一定的简化假设得到单分散非相干单散射的理想体系。该体系光散射理论表明,散射程度(浊度)受分散相数量、分散相颗粒尺寸、两相相对折光指数及入射光波长的影响。得出提高聚合物混合体系透明度的关键是使两相折光指数相匹配,即 m→l,这一结论对真实体系仍适用。并指出共混的透明度还受到成型加工工艺的制约。本文还介绍了提高共混物透明性的几种途径。     

不同PETG对PS/PETG共混物相态结构的影响

采用转矩流变仪制备了聚苯乙烯/聚对苯二甲酸-乙二醇-1,4-环己烷二甲醇酯(PS/PETG)共混物和PS/改性PETG（PETG-M）共混物。采用旋转流变仪和熔体流动速率测定仪测定了PS、PETG和PETG-M的流变性能;采用扫描电子显微镜观测了共混物的相态结构。结果表明,随着PETG和PETG-M含量的提高,PS/PETG共混物和PS/PETG-M中PETG和PETG-M分散相颗粒平均粒径都增大,分散相颗粒密度都减小,在含量相同的情况下,PETG-M的分散相颗粒平均粒径小于PETG,PETG-M的分散相颗粒密度高于PETG,PETG-M的分散相粒径分布宽度更窄。     

EPDM-g-MAN增韧聚氯乙烯的研究

用悬浮法合成三元乙丙橡胶（EPDM）与甲基丙烯酸甲酯（MMA）及丙烯腈（AN）接枝共聚物（EPDM-g-MAN）,用其增韧聚氯乙烯（PVC）树脂。研究了PVC/EPDM-g-MAN共混物的抗冲击性能、增韧机理、相结构以及热稳定性,并与PVC/氯化聚乙烯(CPE)共混物的抗冲击性能进行了对比。结果表明：EPDM-g-MAN比CPE具有更好的增韧效率。SEM分析表明,随着EPDM-g-MAN用量的增加,共混物的增韧机理由裂纹支化终止转变为剪切屈服兼有空穴化。TEM分析表明,EPDM以分散相均匀分散于PVC连续相中,两相界面模糊,具有良好的相容性,且随着EPDM含量的增加,共混物的相结构由“海-岛”结构转变为近连续相结构。EPDM-g-MAN的加入提高了PVC的热稳定性。     

共聚焦拉曼成像技术研究PE-LD/EVOH共混物的三维相结构

利用共聚焦拉曼成像技术研究了低密度聚乙烯（PE-LD）/乙烯-乙烯醇共聚物（EVOH）共混物中各相在压塑样品水平方向、深度方向和三维空间的分布情况,首次获得了PE-LD/EVOH共混物的三维相结构,并直观地将相区与共混物化学成分相对应。结果表明,PE-LD/EVOH共混物为不相容体系;当EVOH的质量分数为20%时,其作为分散相,以较规则的圆柱体形态分散于PE-LD基体中,圆柱直径尺寸在3～6μm范围内。加入马来酸酐接枝聚乙烯（PE-gMAH）作为相容剂后,共混物的相态结构发生显著变化,分散相形状由规则变为不规则,截面的平均尺寸减小到约2μm,这说明PE-g-MAH可显著增强PE-LD与EVOH两组分间的界面相容性。     

在新型混炼器作用下的PP/HMWPE共混物的结构与性能

采用自制新型混炼器对聚丙烯（PP）与高摩尔质量聚乙烯（HMWPE）进行共混,研究了混炼器转速和HMWPE用量对PP／HMWPE力学性能的影响,并对共混物的结构进行了表征。研究表明,在混炼器作用下,HMWPE与PP共混可提高PP的冲击性能,提高量可达33．7％;但HMWPE的含量太高时,反而会降低共混物的性能;混炼器对拉伸性能的影响较小。共混体系的结构都是海-岛结构,两组分各自在自己的本体中结晶,形不成共晶结构,但两者会相互干涉。混炼器的作用是提高共混物中分散相的分散程度和减小分散相的尺寸。     

Coalescence in blends of thermoplastic polyurethane with polyolefins

The coalescence behavior of immiscible blends was determined by annealing the melt without shear. The kinetics and the mechanism of coalescence were observed for blends of thermoplastic polyurethane (TPU) and polyolefins. Two different types of measurements were used to observe coalescence in quiescent melt at the processing temperature. On the one hand, the blend granules were annealed in bulk. The resulting particle sizes were determined by light microscopy and by SEM on particles separated from the blend. On the other hand, thin samples were annealed on a hot stage. Coalescence was observed in situ by light microscopy or static laser light scattering. It was found that the higher viscosity and elasticity ratios between polyethylene and TPU lead to a more pronounced coarsening of the morphology of 80/20 blends than in TPU/polypropylene. It has been shown that the process of reshaping coalescence is one mechanism of coalescence that occurs in quiescent melt. Another mechanism that was directly observed is a “domino effect” where one coalescence process causes the next one.     

Blends of polypropylene with poly(cis-butadiene) rubber. I. Phase structure and morphology of blends

Pressed films of blends of polypropylene with poly(cis-butadiene) rubbers (PcBR) or grafted copolymer of ethyl acrylate (EA) onto PcBR (PcBR-g-EA) was examined by IR spectra, small angle X-ray scattering, small angle laser scatering (SALS), and scanning election microscopy (SEM). The problem of isomerization on PcBR (or PP/PcBR) is discussed by melt mixing (at a temperature of 180°C) using IR. X-ray scatering from the relation of phase was analyzed using Porod's law and led to the values of the interface layer of the blends. With increasing content of rubber, the interface layer thickness (σ_b) had a maximum value at 60/40 (PP/PcBR-g-EA) for the blends. The invariant (Q) was calculated and the relation of Q with σ_b was calculated using Debye-Buech statistical theory, and the average chord length (l) was obtained by Porod's definition of blends. The morphology and structure of the blends were investigated by SEM. The phase separation of the blends was found by SALS. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2265–2272, 1997     

Study on morphology and viscoelastic properties of PP/PET/SEBS ternary blend and their fibers

The morphology development of polypropylene (PP)/polyethylene terephthalate (PET)/styrene‐ethylene‐butylene‐styrene (SEBS) ternary blends and their fibers were studied by means of scanning electron microscopy (SEM) in conjunction with the melt linear viscoelastic measurements. The morphology of the blends was also predicted by using Harkin's spreading coefficient approach. The samples varying in composition with PP as the major phase and PET and SEBS as the minor phases were considered. Although SEM of the binary blends showed matrix‐dispersed type morphology, the ternary blend samples exhibited a morphological feature in which the dispersed phase formed aggregates consisting of both PET and SEBS particles distributed in the PP matrix. The SEM of the blend samples containing 30 and 40 wt % of total dispersed phase showed an agglomerated structure formed between the aggregates. The SEM of the PP/PET binary fiber blends showed long well‐oriented microfibrils of PET whereas in the ternary blends, the microfibrils were found to have lower aspect ratio with a fraction of the SEBS stuck on the microfibril fracture surfaces. These results were attributed to a core‐shell type morphology in which the PET and SEBS formed the core‐shells distributed in the matrix. The melt viscoelastic behavior of the ternary blends containing less than 30 wt % of the total dispersed phase was found to be similar to the matrix and binary blend samples whereas the samples containing 30 and 40 wt % of dispersed phases exhibited a pronounced viscosity upturn and nonterminal storage modulus in low frequency range. These results were found to be in good agreement with the morphological results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Barrier Properties of Blends Based on Liquid Crystalline Polymers and Poly(ethylene terephthalate)

Abstract

Blends of poly(ethylene terephthalate) (PETP) and two different thermotropic liquid crystalline (LC) polymers of the Vectra-type were prepared by melt mixing. Oxygen and water vapor permeability, light transmission and welding properties were measured on compression-molded and film-blown specimens. SEM showed that the LC polymers were the disperse phase with a good phase adhesion to the PETP matrix in the majority of the compression-molded blends. The 50/50 blend based on the low melting point LC polymer showed possibly a continuous LC polymer phase. The film-blown specimens showed LC polymer spheres at low LC polymer content. Above a certain LC polymer content (10-30% LC polymer), fibrous and ellipsoidal LC polymer particles was the dominant morphological feature of the blends. Density measurements showed that the void content in the blends was low. The compression-molded blends based on the high melting point LC polymer showed permeabilities conforming to the Maxwell equation assuming low permeability (LC polymer) spheres in a high permeability (PETP) matrix. The compression-molded blends based on the low melting point Vectra showed lower permeabilities than predicted by the Maxwell equation, particularly at high LC polymer content. The film-blown blends showed extensive scattering in the permeability data. The blend with 30% low melting LC polymer exhibited a 96% lower oxygen permeability than PETP. This was due to a reduction in both oxygen diffusivity and solubility. Ellipsoidal and fibrous LC polymer particles increased the diffusional path and lowered the diffusivity. The transparency of the compression-molded samples was lost already at 1% LCP. The blends showed welding properties superior to those of PETP.     

Fast determination of phase inversion in polymer blends using ultrasonic technique

Ultrasonic attenuation and velocity, together with SEM observation were used to investigate the morphology of some polymer blends. For miscible polymer blends of PVC/NBR, because there is no phase inversion but a homogeneous system a linear change (without discontinuity) of ultrasonic velocity and attenuation was observed in a whole composition ranges. For immiscible polymer blends, namely, PP/PS, PS/EPDM and PS/SBS system, the non-linear variation of ultrasonic velocity with composition indicates the immiscibility. On the other hand, the intensity of scattering attenuation changed from system to system depending on the size of dispersed phase, but a discontinuity of scattering attenuation was always observed as the phase inversion occurred. Our result suggests the sensitivity of ultrasonic attention vs phase inversion and may be served as a useful method to fast determine the phase inversion for immiscible polymer blends.     

Crystalline structure and phase structure of mLLDPE/LDPE blends

The crystalline structure and phase structure of metallocene linear low density polyethylene (mLLDPE) and low density polyethylene (LDPE) blends were investigated, using a combination of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS) techniques. The samples displayed cocrystallization phenomenon for LDPE of 80 wt% in the blends, indicating good compatibility between the two components under this circumstance; as LDPE content decreased, phase separation arose whereas partial cocrystallization still existed in the blends. Over the whole range of weight fractions, the intrinsic crystal structure of mLLDPE does not change with the addition of LDPE, while enhanced orthorhombic crystalline phase were observed as LDPE content increased. The changes in the thickness of interface layer σ_b, dispersed phase size a_c and integral invariant Q further indicate the existence of partial compatibility between the two phases. Irrespective of the phase inversion, the morphology of the dispersed phase is deduced to be in a transitional state from rod-like shape to flakes within the whole proportional range investigated.     

Strengthening of poly(butylene adipate-co-terephthalate) by melt blending with a liquid crystalline polymer

Poly(butylene adipate-co-terephthalate) (PBAT) is a soft biodegradable polymer with a low melting temperature. PBAT has been melt-blended with a liquid crystalline polymer (LCP) aiming at preparing a new biodegradable polymer blend with improved mechanical properties. The phase structure and crystalline morphologies of the PBAT/LCP blends were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). It was found that the LCP domains are precisely dispersed in the PBAT matrix and that these domains act as the nuclei for PBAT crystallization. The nonisothermal crystallization temperature from the melt was dramatically shifted from 50°C to about 95°C by the addition of 20% LCP. In addition, the tensile modulus of the prepared blends increases gradually with increasing LCP content, indicating the excellent strengthening effects of LCP on the PBAT matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation on particular morphology of immiscible polyamide 12/polystyrene blends

In this article, a particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring-opening polymerization of Laurolactam (LL) in the presence of PS was investigated. SEM and FTIR were used to analyze the morphology of the blends. The results showed that PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is less than 5 wt %. When the PS content is higher than 10 wt %, two particular phase morphologies appeared. First, dispersed PS-rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 wt % and 15 wt %. Then, the phase inversion (the phase morphology of the PA12/PS blends changes from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) occurred when PS content is higher than 20 wt %, which is completely different from traditional polymer blends prepared by melt blending. The possible reason for the particular morphology development was illuminated through phase inversion mechanism. Furthermore, the stability of the phase morphologies of the PA12/PS blends was also investigated. SEM showed that the particular morphology is instability, and it will be changed upon annealing at 230°C for 30 min. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012