增塑剂法研究高分子共混物的相平衡曲线

经共聚改性的聚苯乙烯PS(OH)与聚甲基丙烯酸丁酯PBMA形成的互溶体系具有LCST行为。由于体系的玻璃化温度较高。分相温度与玻璃化温度接近。使分相时的浊点温度受升温速率影响很大,以致浊点曲线与相平衡曲线有一定的差距。本文以邻苯二甲酸二丁酯DBP为增塑剂加入PS(OH)/PBMA共混体系中,在一定的升温速率下测浊点温度,并对增塑剂作零浓度的外推,由此得到的浊点曲线与相平衡曲线完全一致。证实了增塑剂法的可靠性。加入增塑剂后浊点温度随升温速率变化平缓,更接近相平衡点,显示了增塑剂法的有效性。     

聚甲基丙烯酸甲酯/聚(苯乙烯-丙烯腈)共混体系相分离的特征动态流变响应

采用动态流变学方法,结合小角激光光散射(SALLS)测定,对聚甲基丙烯酸甲酯(PMMA)/聚(苯乙烯－丙烯腈)(SAN)共混体系的动态流变行为与相分离的关系进行了研究.发现在低频区域,时温叠加失效与共混物体系发生相分离有关,时温叠加失效温度T_b与用SALLS测定的浊点温度T_c一致,用低频区域动态储能模量G'与频率的关系[1gG'～lg(α_T)]偏离线性粘弹模型或时温叠加失效温度表征PMMA/SAN共混体系的相分离是有效的.     

溶剂对相分离法制备聚偏氟乙烯微孔膜性质的影响

研究了用相转换法制备聚偏氟乙烯（PVDF）微孔膜时溶剂对成膜性质的影响.用浊点法测定了二甲基亚砜、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、N-甲基吡咯烷酮、磷酸三甲酯等五种溶剂配制的质量分数为wPVDF=0.12的铸膜液在30℃时的相分离点,显微镜拍照法测定了这些铸膜液与水接触时相分离前沿推进速率,泡点法测定了膜孔径,并测定了气体通量.结果表明,二甲基亚砜、磷酸三甲酯、N,N-二甲基乙酰胺是适于制作聚偏氟乙烯微孔膜的溶剂.     

SiO2粒子对PMMA/SAN共混体系相分离行为的影响

采用小角激光光散射(SALLS)并结合动态流变学方法,考察了气相法二氧化硅(SiO2)粒子的加入对聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混体系相行为的影响,得到了添加SiO2粒子前后的相图,发现SiO2粒子对基体相行为的影响与基体的组成有关.对PMMA/SAN(60/40)体系,加入SiO2粒子后相分离温度上升,但并未改变相分离机理,仍为亚稳单相分解过程(spinodal decomposition,SD);而对于PMMA/SAN(30/70)体系,加入SiO2粒子后却降低了体系的相分离温度.该现象可能是SiO2粒子和基体组分界面间组成与PMMA/SAN共混物基体组成的差异造成的.     

TIPS法制备聚偏氟乙烯平板微孔膜及其表征

以邻苯二甲酸二甲酯(DMP)为稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)平板微孔膜。利用差示扫描量热仪分析了不同PVDF/DMP体系的结晶性能;通过测试纯水通量、孔隙率、泡点、平均孔径、拉伸强度等对膜进行了表征。结果表明:DMP含量增大,结晶温度向低温方向移动,膜拉伸强度降低,当DMP的质量分数为0.70时膜拉伸强度有明显拐点;PVDF/DMP体系冷却发生固-液相分离;PVDF含量增大,膜水通量、孔隙率、最大孔径和平均孔径均减小。     

ATRP法合成接枝共聚物PVDF-g-PNIPAAm及其分离膜的研究

以氯化亚铜(CuCl)/三(N,N-二甲基氨基乙基)胺(Me₆TREN)为催化配位体系, 用DMF作为溶剂, 通过原子转移自由基聚合(ATRP)方法直接在商用聚偏氟乙烯(PVDF)粉末上接枝温敏性材料N-异丙基丙烯酰胺(NIPAAm). 红外光谱(FTIR)和核磁共振(¹H NMR)分析表明, PNIPAAm成功接枝到了PVDF上. 考察了聚合反应时间及反应温度对接枝率的影响. 接枝共聚物以相转化法进行制膜, 通过纯水通量测试温敏性能, 结果表明, PVDF能成功用于ATRP反应, 当温度变化时所制备的PVDF-g-PNIPAAm共聚膜呈现出一定的温度敏感性能.     

振荡剪切流场下PS/PVME/SiO2复合物的相行为

利用光学显微镜-剪切台联用系统研究了振荡剪切流场下聚苯乙烯（PS）/聚甲基乙烯基醚（PVME）/二氧化硅（SiO₂）纳米粒子复合物的热力学稳定性. 结果表明,小振幅振荡剪切可导致PS/PVME共混物出现类似在稳态流场下的剪切诱导相容及剪切诱导相分离现象. 共混体系存在临界振荡频率ω_c,当振荡频率低于ω_c时,发生剪切诱导相分离（SID）行为,反之发生剪切诱导相容（SIM）行为. SiO₂纳米粒子的加入使复合体系的相容性提高. 存在一个临界SiO₂纳米粒子含量φ_c,当SiO₂纳米粒子含量高于φ_c时,复合体系中不存在临界振荡频率ω_c,低振荡频率下的剪切诱导相分离得到抑制. 此外,复合体系的上述行为与升温速率和共混物组成密切相关.     

热致相分离法高效制备压电聚偏氟乙烯膜

以环保溶剂乙酰柠檬酸三丁酯(ATBC)为稀释剂，绿色无毒的离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIM][PF₆])为添加剂，采用热致相分离(TIPS)法制备聚偏氟乙烯(PVDF)微滤膜，通过扫描电子显微镜观察不同添加剂含量PVDF膜的微观形貌；通过超滤杯对PVDF膜的纯水通量进行了测试；使用拉力计对PVDF膜的机械性能进行了表征；通过红外光谱和X-射线衍射研究了添加剂对PVDF膜晶型结构的影响。结果表明：加入1.0%[BMIM][PF₆]时，PVDF的晶型变为β- 晶型。     

活性正离子聚合制备聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物

以2-氯-2,4,4-三甲基戊烷(TMPCl)/TiCl4/质子捕捉剂(DtBP)为引发剂体系,引发异丁烯聚合,随后加入1,1-二(4-甲基苯基)乙烯作为封端剂稳定末端碳正离子,再引入四异丙醇钛(Ti(OiPr)4),降低Lewis酸性,继续引发α-甲基苯乙烯聚合,实现活性正离子聚合制备聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物.考察了α-甲基苯乙烯聚合时间对单体转化率、产物的dn/dc值、分子量及其分布的影响以及四异丙醇钛对聚合速率的影响.并通过体积排斥色谱法/紫外检测器/示差折光指数/多角激光光散射、1H-NMR以及DSC以对产物进行表征.实验结果表明,嵌段共聚物分子量分布窄(MWD≤1.2),单体转化率与分子量呈线性关系,聚合速率对单体浓度呈一级动力学关系,具有活性聚合的特征.Ti(OiPr)4能有效稳定活性中心,降低聚合速率.聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物的DSC测试发现明显的两个Tg,表明存在微相分离结构.     

热致相分离法制聚偏氟乙烯微孔膜稀释剂的选择

依据聚偏氟乙烯(PVDF)、邻苯二甲酸二甲酯、水杨酸甲酯、卡必醇醋酸酯、三醋酸甘油酯、邻苯二甲酸二正丁酯(DBP)、苯乙酮和二苯甲酮(DPK)的Hansen溶度参数及其相对介电常数, 选择能与PVDF以液-液相分离机理进行热致分相的稀释剂, 制备了具有双连续结构的微孔膜. 通过比较PVDF-稀释剂间的溶度参数及相对介电常数的差异, 发现PVDF-DBP体系和PVDF-DPK体系有发生热致液-液相分离的可能. 实时观察上述两个体系的分相过程并测定其结晶温度, 当PVDF质量分数低于30%时, 随着温度的降低, PVDF-DPK体系发生液-液相分离. 根据PVDF-DPK体系相图, 通过控制PVDF含量和降温条件, 无须添加非溶剂或拉伸工艺, 就可以制备出具有双连续结构的PVDF微孔膜.     

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (T_c) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min^?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, T_c of PMMI/PVDF is higher than its melting temperature (T_m) and a large temperature gap between T_c and T_m exists. At the early phase‐separation stage, the apparent diffusion coefficient (D_app) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008     

Effect of Nanoclay on the Phase Separation Behavior of Poly（methyl methacrylate）/Poly（vinyl acetate） Binary Polymer Blends

The effect of nanoclay on the phase-separation behavior of poly（methyl methacrylate）/poly（vinyl acetate）（PMMA/PVAc） blends has been mainly investigated by small-angle laser light scattering. It is found that the effect of clay on the thermodynamics and kinetics of phase-separation for PMMA/PVAc blends seems inconsistent. The kinetics phaseseparation rate decreases, while the thermodynamics parameters, cloud points Tc and delay time tD of isothermal phaseseparation also decrease, and the variation amplitude depends on the matrix composition. The affinity of clay to PMMA results in the composition difference between the border layer and the polymer matrix and further causes the concentration fluctuation at the early stage of phase separation to reduce Tc and tD. On the other hand, the decrease of phase-separation rate is caused by the mechanical barrier effect of clay on the macromolecular diffusion of blend matrix. Hence, such seemingly counterintuitive results on the thermodynamics and kinetics of phase-separation are attributed to different dominant factors.     

Effects of partial replacement of silicone rubber with flurorubber on properties of dynamically cured poly(vinylidene fluoride)/silicone rubber/flurorubber ternary blends

Blends of poly(vinylidene fluoride) (PVDF), silicone rubber (SR) and flurorubber (FKM) were prepared via peroxide dynamic vulcanization. The effect of FKM loading on the morphology, mechanical properties, crystallization behavior, rheology and dynamic mechanical properties of the PVDF/SR/FKM ternary blends was investigated. A “network” was observed in the PVDF/SR binary blends, which disappeared in the ternary blends, but a core-shell-like structure was formed. The mechanical properties were significantly improved. The Izod impact strength of PVDF/SR/FKM blend with 19 wt% FKM was 18.3 kJ/m², which was 3–4 times higher than the PVDF/SR binary blend. The complex viscosity and storage modulus of the PVDF/SR/FKM blends decreased with increasing FKM content, hence the processability was improved. The increase of FKM content seemed to show a favorable effect on the crystallization of the PVDF component. It promoted the nucleation process of PVDF, leading to increased polymer crystallization rate and higher crystallization temperature. The glass-rubber transition temperature of the PVDF phase moved to a lower temperature.     

Miscibility and crystallization behavior in blends of poly(methyl methacrylate) and poly(vinylidene fluoride): Effect of star‐like topology of poly(methyl methacrylate) chain

A tetraarmed star‐shaped poly(methyl methacrylate) (s‐PMMA) was synthesized via atom transfer radical polymerization with 2‐bromoisobutyryl pentaerythritol as the initiator. For comparison, a linear PMMA with the identical molecular weight (l‐PMMA) was also prepared. The blends of the two PMMA samples with poly (vinylidene fluoride) (PVDF) were prepared to investigate the effect of macromolecular topological structure on miscibility and crystallization behavior of the binary blends. The behavior of single and composition‐dependent glass transition temperatures was found for the blends of s‐PMMA with PVDF, indicating that the s‐PMMA is miscible with PVDF in the amorphous state just like l‐PMMA. The miscibility was further evidenced by the depression of equilibrium melting points. It is found that the blends of s‐PMMA and PVDF displayed the larger k value of Gordon–Taylor equation than the blends of l‐PMMA and PVDF blends. According to the depression of equilibrium melting points, the intermolecular parameters for the two blends were estimated. It is noted that the s‐PMMA/PVDF blends displayed the lower interaction parameter than l‐PMMA/PVDF blends. The isothermal crystallization kinetics shows that the crystallization of PVDF in the blends containing s‐PMMA is faster than that in the blends containing the linear PMMA. The surface‐folding free energy of PVDF chains in the blends containing s‐PMMA is significantly lower than those in the blends containing l‐PMMA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2580–2593, 2007     

SPHERULITIC STRUCTURE AND MORPHOLOGY OF POLY(ETHYLENE SUCCINATE)/POLY(ETHYLENE OXIDE) (PES/PEO) BLENDS WITH ONE-STEP CRYSTALLIZATION

The spherulitic structure and morphology development of poly(ethylene succinate)/poly(ethylene oxide) (PES/PEO) blends with one-step crystallization behavior were observed by means of polarizing optical microscope.It was found that the pure PES spherulite in which the adequate quantity of PEO melt existed in the interlamellar regions,and the blending spherulite formed by both PES and PEO lamellae could form simultaneously.When the two types of spherulites contacted with each other the front of the blendi...     

Influence of size reduction of crosslinked rubber particles on phase interface in dynamically vulcanized poly (vinylidene fluoride)/silicone rubber blends

In this paper, the influence of rubber particle size on the phase interface in dynamically vulcanized poly(vinylidene fluoride)/silicone rubber (PVDF/SR) blends without any modifier is discussed through the studies of specific surface of crosslinked SR particles, crystallization behavior and crystal morphology of the PVDF phase, interfacial crystallization, melt rheological behavior and mechanical properties of blends. A series of decreased average particle size was successfully obtained by control of rotor rate. It was found that properly high rotor rate helped to achieve a reduced particle size and a narrowing size distribution. The reduced SR particle size enlarged the PVDF/SR interface which has a positive effect on the interfacial crystallization and the melt rheological behavior. At high SR content, the negative effect of the poor interface interactions played the dominate role on determining the mechanical properties. However, the blend exhibited a unique stiffness-toughness balance at the PVDF/SR = 90/10. We hope that the present study could help to lay a scientific foundation for further design of a useful PVDF/SR blend with promoted properties to partly replace the high-cost synthetic fluorosilicone materials.     

Thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends: Thermogravimetric analysis

Thermal stability of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends has been investigated by thermogravimetric analysis (TGA) in dynamic and isothermal heating regime. PVC/PEO blends were prepared by hot-melt extrusion (HME). According to TG analysis, PEO decomposes in one stage, while PVC and PVC/PEO blends in two degradation stages. In order to evaluate the effect of PEO content on the thermal stability of PVC/PEO blends, different criteria were used. It was found that thermal stability of PVC/PEO blends depends on the blend composition. The interactions of blends components with their degradation products were confirmed. By using multiple heating rate kinetics the activation energies of the PVC/PEO blends thermal degradation were calculated by isoconversional integral Flynn–Wall–Ozawa and differential Friedman method. According to dependence of activation energy on degree of conversion the complexity of degradation processes was determined.     

Crystallization behavior and hydrophilicity of poly (vinylidene fluoride) (PVDF)/poly (styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) (SAN) blends

Poly (styrene-co-acrylonitrile) (SAN) is a hydrophilic non-crystalline copolymer, which is initially used in this paper to improve the hydrophilicity of poly (vinylidene fluoride) (PVDF). Investigation of the crystallization behavior of PVDF/SAN blends showed that the samples presented only α phase regardless of SAN content as cooling from the melt. A double-melting phenomenon was related to the perfection or crystal size of PVDF crystals. As the SAN content is increasing, crystallization of PVDF was limited, leading to a decreased crystallinity and lamellar growth. Besides, the hydrophilicity of PVDF was improved by blending with SAN. The sample containing 70 wt.% SAN performed a similar surface property of the neat SAN owing to the besieging of the PVDF phase by SAN. Observed from the cross section of the blends, PVDF/SAN blends were partially miscible with less than 50 wt.% SAN addition. As the SAN content was more than 50 wt.%, the crystalline PVDF particles clearly dispersed in the amorphous matrix.     

聚β—羟基丁酯酯／超高分子量聚氧化乙烯共混体系相容性和结晶行为

为了解决废弃塑料引起的“白色污染”问题,世界各国竞相研制开发可生物降解高分子材料,其中,有关聚β羟基丁酸酯［ｐｏｌｙ（βｈｙｄｒｏｘｙｂｕｔｙｒａｔｅ）（ＰＨＢ）］的研究尤其活跃．然而,由于商品价格较高,材料本身抗冲击性能较差、加工窗口较窄等限制...