聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

 本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

LLDPE／EAA共混体系结晶行为及相容性

通过ＤＭＡ、ＤＳＣ、偏光显微镜（ＰＬＭ）、ＷＡＸＤ及力学性能测试等方法，对线性低密度聚乙烯（ＬＬＤＰＥ）／乙烯－丙烯酸共聚物（ＥＡＡ）共混体系的研究表明，ＬＬＤＰＥ与ＥＡＡ的非晶相可部分相容，结晶相不能形成共晶；共混物结晶时，两组分相互影响，ＬＬＤＰＥ的结晶速度高于ＥＡＡ，两者结晶没有进入对方晶胞中．还发现ＬＬＤＰＥ与ＥＡＡ力学性能上相容．低含量ＥＡＡ共混体系显示出较佳的力学性能．     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

PTHF-b-PMMA/PVC共混体系的相容性和结晶行为

研究了具有焓效应的聚四氢呋喃-聚甲基丙烯酸甲酯两嵌段共聚物与聚氯乙烯PTHF-b-PMMA/PVC)共混体系的相容性和结晶行为. 结果表明, 其相容性比AB/A型嵌段共聚物共混体系的相容性要好得多; 与PTHF部分相容的PVC对PTHF微区的结晶行为可产生很大的影响. 应用有关理论和模型很好地解释了结晶行为的这种变化.     

聚环氧乙烷/聚乙基■唑啉共混体系结晶行为及相容性的研究

用偏光显微镜（ＰＬＭ）、ＤＳＣ、ＩＲ和ＷＡＸＤ等测试方法对聚环氧乙烷（ＰＥＯ）／聚乙基唑啉（ＰＥＯｘ）共混体系结晶行为及相容性进行了研究．结果表明，ＰＥＯ含量在３０％以上的共混体系中，几乎完全被球晶充满，非晶态ＰＥＯｘ作为微区分散在大球晶之间或之中；含量为２０％的共混体系照片上呈树枝状晶；含量低于１０％时则看不到结晶出现，体系形成单一的非晶相．对任何组成的共混物，均只出现单一的玻璃化转变温度（Ｔｇ），而且符合Ｆｏｘ方程揭示的规律；随ＰＥＯｘ组分含量的增加，共混体系的结晶度减小，熔点下降，并利用平衡熔点方程计算出ＰＥＯ与ＰＥＯｘ的相互作用能密度．非晶ＰＥＯ与ＰＥＯｘ热力学相容，其相容性是由于这两种分子间存在着特殊相互作用．ＰＥＯｘ的加入不会改变ＰＥＯ的晶胞参数．     

聚L-乳酸/4,4'-二羟基二苯硫醚共混物的分子间相互作用及结晶和熔融行为

利用红外吸收光谱(FTIR)研究了聚乳酸(PLLA)/4,4'-二羟基二苯硫醚(TDP)熔融共混物的分子间相互作用,结果表明,PLLA的羰基与TDP的羟基之间形成了分子间氢键.通过差示扫描量热(DSC)研究了共混物的玻璃化转变行为及非等温结晶和熔融行为.结果表明,样品的玻璃化转变温度(Tg)随TDP含量的增加呈线性下降.共混物的熔融结晶温度(Tc)、结晶焓(ΔHc)、熔融温度(Tm)及熔融焓(ΔHm)均随TDP含量的增加呈下降趋势,而冷结晶温度的变化趋势则相反.当TDP达到40%(质量分数)时,共混物的DSC曲线既未出现结晶峰,也未出现熔融峰,表明该样品已完全成为非晶态物质.广角X射线衍射(WAXD)分析结果表明,TDP的加入未改变PLLA的晶型,但导致其晶面间距变大,晶体结构变得松散.因此共混物熔点的下降归因于分子间氢键的形成降低了PLLA分子链的运动能力及晶体的紧密程度而非晶型的改变.     

聚丁二酸丁二醇酯的自成核结晶行为

利用差示扫描量热仪(DSC)研究了自成核对聚丁二酸丁二醇酯(PBS)的结晶行为的影响. 研究结果表明, PBS的有效自成核温度处理区间为118～120 ℃. PBS经自成核处理后结晶温度提高, 可以在100~118 ℃温度区间内迅速结晶. 同时, 研究了自成核处理后样品在100～104 ℃范围内的等温结晶行为、动力学过程及熔融行为. 结果表明, 随着等温结晶温度的升高, 结晶速率变慢, 熔融曲线出现多重熔融峰. Hoffman-Weeks方程分析结果表明, 自成核处理对PBS的平衡熔点没有影响. Avrami等温结晶动力学方程适合分析自成核处理样品的等温结晶动力学过程, 获得其动力学参数K与n, 其中n值偏大的原因在于自成核的样品结晶生长点增多. 根据Arrhenius方程, 计算获得PBS自成核处理后等温结晶活化能为-286 kJ/mol.     

聚甲基丙烯酸甲酯－聚四氢呋喃两嵌段共聚物／聚四氢呋喃共混体系的相容性和结晶行为

报道了对嵌段共聚物结晶型共混体系结晶行为的研究．通过对聚甲基丙烯酸甲酯－聚四氢呋喃两嵌段共聚物／聚四氢呋喃共混体系的研究，我们发现１．微相分离结构的存在，可使相容的这类体系形成多种特殊的结晶形态；２．共混体系的相容性可以方便地由其结晶行为来判断；３．共混体系中共聚物的结晶能力显著提高．这些特点都明显不同于一般的聚合物共混体系．     

聚β-羟基丁酸酯/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...     

生物可降解聚丁二酸/苯基丁二酸丁二醇酯系列共聚物的合成及其结晶行为

合成了一系列聚丁二酸/苯基丁二酸丁二醇共聚酯(PBSBS),利用DSC、1H-NMR和X射线等测试手段对共聚物组成、热力学性能、结晶性能、等温结晶行为进行了表征和研究.结果表明,含苯基的共聚单元的引入显著改变了聚丁二酸丁二醇酯(PBS)的热力学性能4,利用Hoffman-Week曲线得到的共聚物平衡熔点随共聚组分含量的增加显著降低,玻璃化转变温度则明显升高,结晶熔点符合无规共聚物的Flory方程.此外,利用Avrami方程对均聚物PBS以及共聚物PBSBS-10分别进行了等温结晶行为研究,结果表明共聚使结晶速率降低,PBS和PBSBS-10的Avrami指数分别介于2.8~3.0和2.7~2.9之间,结晶方式为三维生长异相成核,X射线测试结果表明共聚不影响晶体结构.     

Miscibility and Crystallization in Binary Crystalline Blends of Poly(butylene terephthalate) with Poly(butylene terephthalate-e-caprolactone)

Poly(butylene terephthalate)/poly(butylene terephthalate-e-caprolactone) is a new A/AxB1-x binary crystalline blend with intra-molecular repulsion interaction. Using the mean-field binary interaction model, the value of interaction parameter between the butylene terephthalate and caprolactone structural unit was first reported to be 0.305. This blend exhibited different crystallization behavior from a typical homopolymer/copolymer blend, which was carefully investigated by di?erential scanning calorimetry. It was found that poly(butylene terephthalate-e-caprolactone) copolymers have a great effect on the pure poly(butylene terephthalate) chain mobility and poly(butylene terephthalate) crystalline lattice packing. In the meantime, the crystallization of butylene terephthalate segments in copolymers was restricted by the previously formed poly(butylene terephthalate) crystallites. The two constituents for blending can not form a co-crystal in the range of composition even if they have the same butylene terephthalate unit. It can be concluded that longersegments in a copolymer would be beneficial for the formation of a co-crystal in blends.     

动态流变学对PVDF/PTW共混物流体相容性研究

采用熔融共混法制备了聚偏氟乙烯/乙烯-丙烯酸丁酯-甲基丙烯酸缩水甘油酯共聚物(PVDF/PTW)共混物,利用流变仪考察了PVDF/PTW共混物的相互作用及两者的相容性.观察共混物在200℃下的流变曲线,发现在低频区,共混物中PTW含量越大,共混物的流变曲线越偏离经典流变理论,这个结果与cole-cole图相一致.通过时温叠加原理(时温等效主曲线、Han曲线和v GP曲线)系统研究了不同组成的PVDF/PTW共混体系在均相区和相分离区的黏弹行为.结果表明,在均相区,不同温度下,共混体系的动态模量利用时温叠加原理,通过水平位移就可以很好地叠加在一起,无论是储能模量还是损耗模量,在低频末端均近似地符合经典低频末端标度关系;在相分离区,动态模量偏离了经典的低频末端标度关系,其中储能模量的偏离尤为明显,从而导致了时温叠加原理的失效,相应的Han图、v GP图也表现出不同于均相体系的特征,这些特征的响应可以用来表征共混体系的相容性,表明在研究的一系列配比(PVDF/PTW 100/0、90/10、70/30、50/50、30/70、10/90、0/100,W/W)中,当PVDF/PTW=90/10(W/W)时,两者的相容性较好.SEM也证实了这个结论.     

Fully biodegradable blends of poly(butylene succinate) and poly(butylene carbonate): Miscibility, thermal properties, crystallization behavior and mechanical properties

Fully biodegradable poly(butylene succinate) (PBS) and poly(butylene carbonate) (PBC) blends were prepared by melt blending. Miscibility, thermal properties, crystallization behavior and mechanical properties of PBS/PBC blends were investigated by scanning electron microscopy (SEM), phase contrast optical microscopy (PCOM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and mechanical properties tests. The SEM and PCOM results indicated that PBS was immiscible with PBC. The WAXD results showed that the crystal structures of both PBS and PBC were not changed by blending and the two components crystallized separately in the blends. The isothermal crystallization data showed that the crystallization rate of PBS increased with the increase of PBC content in the blends. The impact strength of PBS was improved significantly by blending with PBC. When the PBC content was 40%, the impact strength of PBS was increased by nearly 9 times.     

左旋聚乳酸的结晶行为研究

用DSC, WAXD和POM对Zn催化剂制备的左旋聚乳酸(PLLA)的熔体结晶行为进行了研究. 在95~125 ℃范围内, PLLA熔体结晶生成厚度约(14±1) nm的片晶, 该片晶不易发生熔体等温增厚. 对实验数据分别用Avrami方程和Arrhenius方程进行了计算, Avrami指数n=3±0.3, 表明PLLA以球晶形式生长, 其最大结晶速率温度为(105.0±0.5) ℃, t1/2约为5.2 min. 利用Lauritzen-Hoffmann（LH）理论对PLLA结晶机理进行了分析, 发现PLLA结晶的Regime Ⅱ和Regime Ⅲ的转变温度为107 ℃. Kg(Ⅱ)和Kg(Ⅲ)分别为4.57×105 K2和1.115×106 K2, 且Kg(Ⅲ)/Kg(Ⅱ)=2.4, 与LH理论值一致.     

PEO分子量对POM/PEO晶/晶共混物溶液结晶的影响

以六氟异丙醇(HFIP)为聚甲醛(POM)与聚氧化乙烯(PEO)的共溶剂,通过溶液结晶研究了PEO分子量对POM/PEO 50/50晶/晶共混物结晶行为及结晶形态的影响。结果表明,PEO分子量越小,POM与PEO在结晶过程中相互干扰越大。当PEO分子量为4×103时,共混物中POM形成部分不完善晶体,出现明显的熔融双峰。SEM结果表明:含不同分子量PEO的共混晶体均无明显相分离,且低分子量PEO的共混物更易形成规整球晶,认为通过溶液结晶,POM/PEO 50/50共混物中POM与PEO形成了晶体相互穿插的结晶结构。     

Miscibility,Crystallization, and Rheological Behavior of Solution Casting Poly(3-hydroxybutyrate)/poly(ethylene succinate) Blends Probed by Differential Scanning Calorimetry,Rheology, and Optical Microscope Techniques

The miscibility and crystallization of solution casting biodegradable poly(3-hydroxybuty-rate)/poly(ethylene succinate) (PHB/PES) blends was investigated by differential scanning calorimetry, rheology, and optical microscopy. The blends showed two glass transition temperatures and a depression of melting temperature of PHB with compositions in phase diagram, which indicated that the blend was partially miscible. The morphology observation supported this result. It was found that the PHB and PES can crystallize simultaneously or upon stepwise depending on the crystallization temperatures and compositions. The spherulite growth rate of PHB increased with increasing of PES content. The influence of compositions on the spherulitic growth rate for the partially miscible polymer blends was discussed.     

Miscibility and properties of poly(l-lactic acid)/poly(butylene terephthalate) blends

Binary blends of poly(l-lactide) (PLLA) and poly(butylene terephthalate) (PBT) containing PLLA as major component were prepared by melt mixing. The two polymers are immiscible, but display compatibility, probably due to the establishment of interactions between the functional groups of the two polyesters upon melt mixing. Electron microscopy analysis revealed that in the blends containing up to 20% of poly(butylene terephthalate), PBT particles are finely dispersed within the PLLA matrix, with a good adhesion between the phases. The PLLA/PBT 60/40 blend presents a co-continuous multi-level morphology, where PLLA domains, containing dispersed PBT units, are embedded in a PBT matrix. The varied morphology affects the mechanical properties of the material, as the 60/40 blend displays a largely enhanced resistance to elongation, compared to the blends with lower PBT content.     

Miscibility of biodegradable poly(propylene succinate)/poly(propylene adipate) blends: Effect of the transesterification reactions

The miscibility of poly(propylene succinate)/poly(propylene adipate) blends was investigated by means of DSC, WAXS and NMR techniques. Poly(propylene succinate) and poly(propylene adipate) were found to be completely immiscible in as blended-state. The miscibility changes upon extended mixing at elevated temperature: for enough long mixing time, the original two phases gradually merged into a single one because of transesterification reactions. The NMR analysis showed that the transesterifications led to block copolymers whose average sequence length decreased as the mixing time is increased at a fixed temperature. Upon very long mixing time (150 min), all PPS and PPA chains are fully transformed into a random copolymer characterized by a single amorphous phase.     

Miscibility and interactions of polystyrene/polyolefine and polystyrene/poly(n-alkyl methacrylate) mixtures in dilute xylene solutions

The miscibility and intermolecular interactions between polystyrene (PS) and poly(ethylene-co-propylene) (EPC), as well as between PS and long-chain poly(alkyl methacrylates) (PAMA), namely, poly(dodecyl methacrylate) (PDDMA) and poly(octadecyl methacrylate) (PODMA), in dilute xylene solutions at 30 °C were studied. Investigated polymers are widely used as rheology modifiers, i.e. viscosity index improvers and pour point depressants for lubricating mineral oils. The specific and reduced viscosities of two- and three-component polymer solutions as well as intrinsic viscosities and Huggins’ parameter values were determined as functions of the polymer mixture composition and overall polymer concentration. The reduced viscosity was found to be linearly dependent on the overall polymer concentration. The observed viscosities of polymer mixtures were intermediate to those of the mixture constituents; the values decrease in the order: EPC > PS > PAMA. The specific viscosities of all the polymer mixtures obtained as the experimental results and calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations were considered. Since all the polymer/polymer pairs showed the negative viscometric interaction parameter values (Δb₁₂ < 0), the PS/EPC and EPC/PAMA mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and molar masses. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter. The calculated values of interaction parameters for (co)polymer blends, Λ₁₂, were 5.47, 6.42 and 13.1 J cm⁻³ for PS/PDDMA, PS/PODMA and PS/EPC, respectively.