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。     

同向双螺杆挤出中共混物相态发展过程

本文研究了模型聚合物共混体系ＨＤＰＥ／ＰＳ在同向双螺杆挤出机中的相态发展过程。研究发现分散相相畴尺寸变化主要发生在双螺杆的熔融段。在双螺杆共混初始阶段存在大量的片状和纤维状分散相结构。根据实验现象建立了双螺杆挤出中共混物相态变化的物理模型,为进一步模拟双螺杆共混过程提供了理论基础。     

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。     

环氧化EPDM对PBT/LLDPE共混体系的微观形态及力学性能的影响研究

采用反应性熔融共混技术制备了聚对苯二甲酸丁二醇酯(PBT)/线型低密度聚乙烯(LLDPE)共混物,并采用环氧化三元乙丙橡胶(eEPDM)为增容剂改善PBT/LLDPE共混体系的相容性。使用红外光谱(FTIR)和扫描电子显微镜(SEM)等手段对共混物进行了分析和相形态观察,并测试了力学性能,研究了eEPDM对PBT/LLDPE共混体系形态结构和力学性能的影响。研究结果表明,熔融共混过程中eEPDM的环氧基团与PBT的端羧基发生化学反应,就地生成PBT-g-EPDM共聚物,该共聚物可对PBT/LLDPE共混物起到良好的增容作用。与PBT/LLDPE/EPDM共混体系相比,PBT/LLDPE/eEPDM共混物的相区尺寸更小,分布更窄,而且加入eEPDM在改善冲击强度方面比添加EPDM更有效。     

聚合物共混物分相与解分相动力学

采用相差显微镜研究了具有最低临界共溶温度(LCST)的聚丁二酸丁二醇酯/聚环氧乙烷(PBS/PEO)(质量百分比为20∶80)共混物液液相分离过程。通过小角激光光散射方法对共混物液液相分离进行了原位实时观测,并探讨了相尺寸与分相时间的标度关系。结果证明:液液相分离过程中,相尺寸与分相时间的标度关系为:qm∝t-α,且指数α为1/3,符合经典的蒸发-凝结理论与碰撞融合理论对spinodal旋节线分相动力学的预测。通过小角激光光散射方法对共混物解分相过程进行了原位实时观测,并探讨了解分相过程中相尺寸与分相时间的标度关系:qm∝tβ,且指数β为1/2,发现解分相过程中涨落动力学与非线性Langevin公式理论计算结果一致。     

聚丙烯聚乙烯顺丁橡胶三元共混体系力学性能及光学性能的研究

本文主要讨论了等规聚丙烯/低密度聚乙烯/顺丁橡胶三元共混体系(其中橡胶部分硫化)的力学性能、并用光散射法研究了共混体系的结晶形态及橡胶对等规聚丙烯和低密度聚乙烯共混体系结晶的影响,从光散射强度计算了混合球晶的尺寸。     

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。     

聚烯烃离聚体原位增容PP/LLDPE共混物的研究!

用傅立叶红外光谱(FTIR)、力学性能测试等方法研究了聚烯烃离聚体原位增容聚丙烯/线性低密度聚乙烯(PP/LLDPE)共混物。结果表明:熔融状态下,在马来酸酐接枝聚丙烯/马来酸酐接枝线性低密度聚乙烯(PP-g-MAH/LLDPE-g-MAH)(质量比50/50)共混物中加入二水醋酸锌,共混物中的马来酸酐基团(羧酸基团)与Zn2+发生离子偶联反应,相界面就地产生的聚烯烃离聚体增加了两相界面黏合力,共混物力学性能提高;原位增容后共混物中的PP和LLDPE相熔点略微下降,LLDPE结晶温度向高温移动;在角频率为0.01～100.00s-1,原位增容后共混物的储能模量、损耗模量和复数黏度都高于简单共混物的,损耗正切(tanδ)低于简单共混物的;对于PP/PP-g-MAH/LLDPE/LLDPE-g-MAH四元体系,SEM显示原位增容后共混物的相界面变得模糊,相容性提高。     

氟橡胶/环氧丙烯酸酯橡胶共混物的双连续相形态和性能(英文)

采用双螺杆挤出机,通过熔融共混法制备了氟橡胶(FKM)/环氧丙烯酸酯橡胶(EACM)共混物.用透射电镜和动态机械热分析仪研究了FKM/EACM共混物的形态、热力学性能和动态机械性能,探讨了共混比对其力学性能的影响.透射电镜研究结果显示,FKM/EACM共混物在共混比范围内呈现出完美的两相连续结构形态,共混体系的相畴尺寸随着EACM用量的不同而改变,当FKM/EACM(质量比)为80/20时,EACM在FKM的基质中形成最完善的网络结构;同时两相产生了协同效应,FKM/EACM共混物的拉伸强度和撕裂强度达到最大值.     

剪切作用下POE-g-MAH和PP-g-MAH对PA1010/PP共混物的增容作用

采用熔融共混的方法制备了聚酰胺1010/聚丙烯（PA1010/PP）共混物,通过扫描电镜、力学性能和差示扫描量热等方法研究了剪切作用下马来酸酐接枝乙烯-辛烯共聚物（POE-g-MAH）和马来酸酐接枝聚丙烯（PP-g-MAH）对PA1010/PP共混物的增容作用。结果表明,同样条件下,PP-g-MAH增容体系的相区尺寸较小,相界面更模糊,PP相的结晶温度和结晶度明显提高,共混物的拉伸强度和冲击强度均高于非增容体系。而POE-g-MAH增容体系的相区尺寸相对较大,PP相的结晶温度和结晶度明显降低,共混物只有冲击强度明显高于非增容体系,拉伸强度略低于非增容体系。     

Structured latex particles based on natural rubber for high-impact polymer blends

Natural latex (NR) particles, modified with a hard shell of poly(methyl methacrylate) (PMMA) and with a substructure of PMMA (type "NR-M") or polystyrene (type "NR-SM"), were tested as compatibilizers in blends of polycarbonate (of bisphenol A, PC) and PMMA or PS. During melt blending, the modified NR particles were torn apart, from an original size of >0.5 μm down to ≅0.1 μm in diameter. Two different types of particle distribution were observed in the blends: in PC/PMMA/NR-M blends, the NR-M particles were dispersed in the PMMA phase, whereas, in PC/PS/NR-SM blends, the NR-SM particles formed interface layers between PC and PS phase domains. The latter blend morphology, distinguished by continuous rubbery interface layers of NR-SM, turned out to be mechanically excellent in injection-moulded parts. The poor impact strength of PC/PS was raised by an order of magnitude. The effect depends on the orientation in the injection-moulded test bars.     

A modified model predictions and experimental results of weld-line strength in injection molded PS/PMMA blends

In this paper, the model based on melt diffusion and Flory-Huggins free energy theory for predicting the weld-line strength of injection molded amorphous polymers and polymer blends parts were modified by considering the diffusion thickness in the interface as a function of contact time. The modified model for weld-line strength prediction of homopolymers and polymer blends were, respectively, used to evaluate the weld-line strength of Polystyrene (PS) and Poly(methylmethacrylate) (PMMA), and that of PS/PMMA blends. The model predictions show that the theoretic predictions as a function of temperature and contact time for PS, PMMA and PS/PMMA (80/20, 70/30) are in good agreements with corresponding experimental results. However, the model predictions for PS/PMMA (20/80, 30/70) blends are much higher than experimental results. The morphology in weld-line regions for PS/PMMA (20/80, 30/70) shows lack of dispersed PS phase. Near the weld-line regions, dispersed PS phase is highly oriented along the weld-line. In theoretic prediction for polymer blends, three kinds of diffusion: Polymer A-Polymer A and Polymer B-Polymer B self-diffusions and Polymer A-Polymer B mutual diffusion were considered. This is why model predictions for PS/PMMA (20/80, 30/70) blends are higher than experimental results.     

拉曼Mapping成像研究聚苯乙烯/聚甲基丙烯酸甲酯共混体系的相态结构

利用拉曼光谱成像技术研究了聚苯乙烯/聚甲基丙烯酸甲酯（PS/PMMA）共混薄膜体系及其增容体系（增容剂为PS-b-PMMA嵌段共聚物）的相态结构及化学成分分布。实验结果表明,拉曼Mapping成像技术不仅可以得到PS/PMMA共混体系化学成分的精确分布图,同时也可以获取共混体系中分散相、界面相和连续相的分子指纹光谱。研究发现,共混体系中分散相和连续相组分分布与体系的组成紧密相关,当PS/PMMA质量比30/70时,分散相为PS,连续相为PMMA;当PS/PMMA质量比为50/50时,分散相为PS,但PS分子链仍存在于PMMA连续相中;当PS/PMMA质量比为70/30时,分散相为PMMA,连续相为PS。当增容剂PS-b-PMMA加入到PS/PMMA共混体系中后,分散相粒径减小、分布更加均匀、共混体系相容性指数（N_c）增大,说明PS/PMMA共混体系由完全不相容体系趋向变成半相容性体系,这是因为增容剂能增加PS和PMMA之间的相互作用,降低了体系的相分离程度,改善了共混体系的相容性。     

Effect of ultrasonic oscillations on weld line strength of PS,PMMA, and their blends

The effect of ultrasonic oscillations on the weld line strength of amorphous polystyrene (PS), polymethyl methacrylate (PMMA), and PS/PMMA (20/80, 50/50, 80/20) blends at various temperatures was investigated. By facilitating the molecular diffusion across the weld line, the introduction of ultrasonic oscillations could evidently improve the weld line strength of PS, PMMA, and their blends. The different effects on the weld line strength of PS/PMMA (20/80, 50/50, 80/20) blends were investigated. The ultrasonic oscillations could greatly increase the weld line strength of PS/PMMA (80/20) by ～ 70%, but was less efficient to PS/PMMA (50/50, 20/80) blends, due to the great difference of weld line morphologies of these blends. The dispersed phase of PS/PMMA (80/20) in the weld line was spherical while two different morphologies in the weld line of PS/PMMA (50/50) were observed. And the stripe‐like morphology of PS perpendicular to the flow direction in the weld line of PS/PMMA (20/80) is responsible for the little effect of ultrasonic oscillations. The fractured surfaces of PS, PMMA, and PS/PMMA (80/20) with weld line became much rougher due to the introduction of ultrasonic oscillations. The morphology study of PS/PMMA (80/20) showed that the spherical dispersed phase of PS/PMMA at the skin turned smaller under ultrasonic oscillations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2990–2997, 2006     

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.     

Thermal behavior and properties of polystyrene/poly(methyl methacrylate) blends

The thermal behavior and properties of immiscible blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with and without PS‐b‐PMMA diblock copolymer at different melt blending times were investigated by use of a differential scanning calorimeter. The weight fraction of PS in the blends ranged from 0.1 to 0.9. From the measured glass transition temperature (T_g) and specific heat increment (ΔC_p) at the T_g, the PMMA appeared to dissolve more in the PS phase than did the PS in the PMMA phase. The addition of a PS‐b‐PMMA diblock copolymer in the PS/PMMA blends slightly promoted the solubility of the PMMA in the PS and increased the interfacial adhesion between PS and PMMA phases during processing. The thermogravimetric analysis (TGA) showed that the presence of the PS‐b‐PMMA diblock copolymer in the PS/PMMA blends afforded protection against thermal degradation and improved their thermal stability. Also, it was found that the PS was more stable against thermal degradation than that of the PMMA over the entire heating range. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 609–620, 2004     

A study on weld line morphology and mechanical strength of injection molded polystyrene/poly(methyl methacrylate) blends

In this work, the mechanical strength and weld line morphology of injection molded polystyrene/poly(methyl methacrylate) (PS/PMMA) blends were investigated by scanning electron microscopy (SEM) and mechanical property test. The experimental results show that the tensile strength of PS/PMMA blends get greatly decreased due to the presence of the weld line. Although the tensile strength without the weld line of PS/PMMA (70/30) is much higher than that of the PS/PMMA (30/70) blend, their tensile strength with weld line shows reversed change. The viscosity ratio of dispersed phase over matrix is a very important parameter for control of weld‐line morphology of the immiscible polymer blend. In PS/PMMA (70/30) blend, the PMMA dispersed domains at the core of the weld line are spherically shaped, which is the same as bulk. While in the PS/PMMA (30/70) blend, the viscosity of the dispersed PS phase is lower than that of the PMMA matrix, the PS phase is absent at the weld line, and PS particles are highly oriented parallel to the weld line, which is a stress concentrator. This is why weld line strength of PS/PMMA (30/70) is lower than that of PS/PMMA (70/30) blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1856–1865, 2002; DOI 10.1002/app.10450     

On the presence of a critical shell volume fraction leading to pseudo-pure droplet behavior in composite droplet polymer blends

During melt mixing a ternary blend system comprised of a high density polyethylene matrix containing dispersed polystyrene and poly(methyl-methacrylate) spontaneously forms a composite droplet structure where the PS encapsulates the PMMA. This study demonstrates that the PS/PMMA composite droplet exhibits pure PS droplet behavior at a critical volume fraction of encapsulating phase (PS:PMMA∼0.6:0.4). This critical volume fraction is shown to be independent of the overall dispersed phase concentration, shell thickness or dispersed phase size. Furthermore, the effect is observed even though the PMMA is significantly more viscous than the encapsulating PS phase. Interfacial slip as well as the maintenance of a complete PS shell during deformation are proposed as being important factors related to this behavior. The blends were prepared via melt mixing using an internal mixer and the morphology was examined by electron microscopy.     

Effect of composition on the linear viscoelastic behavior and morphology of PMMA/PS and PMMA/PP blends

Here, the effect of concentration on the morphology and dynamic behavior of polymethylmethacrylate/polystyrene (PMMA/PS), for PS with two different molecular weight, and polymethylmethacrylate/polypropylene (PMMA/PP) blends was studied. The blends concentrations ranged from 5% to 30% of the dispersed phase (PS or PP). The dynamic data were analyzed to study the possibility of inferring the interfacial tension between the components of the blend from their rheological behavior using Palierne [Palierne JF. Rheol Acta 1990;29:204-14] [1] and Bousmina [Bousmina M. Acta 1999;38:73-83] [2] emulsion models. The relaxation spectrum of the blends was also studied. The dynamic behavior of 85/15 PS/PMMA blend were studied as a function of temperature. It was possible to fit both Palierne and Bousmina's emulsion models to the dynamic data of PMMA/PS blends, to obtain the interfacial tension of the blend. This was not the case for PMMA/PP. The relaxation spectrum of both blends was used to obtain the interfacial tension between the components of the blends. The values of interfacial tension calculated were shown to decrease when the concentration of the blends increased. It was shown using morphological analysis that this phenomenon can be attributed to the coalescence of the dispersed phase during dynamic measurements that occurs for large dispersed phase concentration. When the ‘coalesced’ morphology is taken into account in the calculations the interfacial tension inferred from rheological measurement did not depend on the concentration of the blend used. The values of interfacial tension found analyzing the dynamic behavior of one of the PMMA/PS blend were shown to decrease with temperature.     

Ultraporous poly(l-lactide) scaffolds prepared with quaternary immiscible polymer blends modified by copolymer brushes at the interface

The activity of polystyrene-block-poly(l-lactide) (PS-b-PLLA) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer brushes located at a PS/PLLA interface were employed as a route to control the final microstructure of 95% void volume, ultraporous PLLA scaffolds. The latter were initially prepared from melt-processed quaternary blends of ethylene propylene diene rubber/poly(?-caprolactone)/polystyrene/poly(l-lactide) (EPDM/PCL/PS/PLLA) 45/45/5/5%vol. modified with the diblock copolymers. The blends display a layer comprised of the PS and PLLA phases located at the interface of the co-continuous EPDM and PCL phases. When the PS-b-PLLA copolymer is added, sub-micrometric PLLA droplets are encapsulated within the PS continuous layer phase. In comparison, both the PS and PLLA phases compete for the encapsulation process when the PS-b-PMMA is used, indicating that the microstructure of the PLLA phase can be fine-tuned with an adequate choice of interfacial modifier. These effects were investigated by analyzing the microstructure of ternary high-density polyethylene (HDPE)/PS/PMMA 80/10/10%vol. blends displaying PS/PMMA shell/core composite droplets in a HDPE matrix. An inversion of the shell/core structure is observed when the PS-b-PLLA copolymer is used to compatibilize the PS/PMMA interface, whereas no such restructuring occurs with the PS-b-PMMA. These effects are explained by the activity and swelling powers of the copolymer brushes. For the EPDM/PCL/PS/PLLA quaternary systems modified with the PS-b-PMMA, the PLLA homopolymer phase significantly penetrates and swells the PMMA blocks due to their mutual high affinity, as compared to the classical like-prefers-like compatibilization approach. The swelling of the blocks will tend to bend the interface toward the PS phase in order to minimize the lateral compression of the PMMA blocks. A similar effect explains the reversal of the PS/PMMA shell/core structure in the HDPE/PS/PMMA ternary system. This level of control ultimately leads to quite significant differences in microstructures and surface textures for the PLLA scaffolds.