枝化聚丁二酸丁二醇酯共聚物的合成及结晶性能研究

采用丁二酸(SA)、1,4-丁二醇(BDO)及枝化单体正丁基缩水甘油醚(BGE)合成了不同枝化度的枝化聚丁二酸丁二醇酯(PBS)共聚物,采用核磁共振仪、X射线衍射仪、差示扫描量热仪以及偏光显微镜对枝化共聚物的化学组成及结晶性能进行了表征。结果表明,枝化单元的引入没有改变聚合物的晶型,但显著改变了其热力学性能,枝化PBS共聚物的熔点(Tm)、结晶度(Xc)均随枝化单体含量的增加逐渐降低;相比纯PBS,枝化PBS共聚物的Avrami指数n降低;高枝化度对结晶形貌,特别是环带的形貌有较大影响。     

脂肪酶N435催化合成PBS

采用多级酶催化法在无溶剂和有机溶剂中,用脂肪酶N435催化丁二酸二乙酯和1,4-丁二醇(1,4-BDO)聚合,得到聚丁二酸丁二醇酯(PBS),Mw分别达到2009和5295.研究结果表明:在80℃时脂肪酶具有最好的催化活性;70℃,合成的PBS的Mw/Mn最佳,并且Mw随反应时间的增加而增加.同时二苯醚是获得较高Mw和低Mw/Mn的PBS的优良溶剂.在二苯醚中合成PBS,影响Mw的因素是水含量、酶浓度;影响Mw/Mn的因素是反应物浓度;影响产率的因素是酶浓度.     

不同扩链剂对PBS性能的影响

通过熔融溶液相结合的方法合成聚丁二酸丁二醇酯(PBS)预聚物。用异佛尔酮二异氰酸酯(IPDI)、六亚甲基-1,6-二异氰酸酯(HDI)和丁二酰氯(SUC)对PBS预聚体进行扩链改性。采用熔点仪测定PBS的熔点;采用傅里叶变换红外光谱仪对PBS的结构进行了表征;采用凝胶渗透色谱仪、热重仪和万能实验机测定了PBS的摩尔质量及其分布、热稳定性和力学性能;测定失重率,考察不同扩链剂对PBS降解性能的影响。结果表明:PBS扩链后摩尔质量均有显著提高,摩尔质量分布均小于扩链前;且断裂伸长率等力学性能和热分解温度等热性能也都有明显改善。但用不同扩链剂扩链后,PBS降解性能有较大区别。     

线性PBS基脂肪族聚酯的合成和降解研究

为了探讨线性PBS基脂肪族共聚酯的结构和降解之间的关系,首先合成了线性PBS基脂肪族共聚酯,即聚丁二酸丁二醇酯-共-聚己二酸丁二醇酯P(BS-co-BA),聚丁二酸丁二醇酯-共-癸二酸丁二醇酯P(BS-co-BSe),并将线性PBS基脂肪族共聚酯及PBS在土壤悬浮液中进行降解,通过GPC、熔点测定仪对线性PBS基脂肪族共聚酯的分子量和熔点进行了测定;通过测定降解过程中失重率和降解前后聚酯薄膜表面形貌来对共聚酯降解程度进行表征。结果表明:随着二元酸碳链的增长,分子对称性降低,降解性能增大。通过观察分子量,熔点及降解失重率的测定结果,得出分子量越大,降解越不容易进行;熔点越小,降解性能越好。     

硫酸钙晶须/PBS共混物等温结晶动力学研究

用差示扫描量热仪(DSC)测试了硫酸钙晶须/聚丁二酸丁二醇酯(PBS)共混物的等温结晶过程。采用Hoffm-weeks方程拟合的方法得到了4种配比的硫酸钙晶须/PBS共混物的平衡熔点,并根据实验数据拟合出描述硫酸钙晶须/PBS共混物等温结晶过程的Avrami方程。结果表明:共混物的平衡熔点随着硫酸钙晶须含量的提高而降低;硫酸钙晶须的加入,对PBS的成核机理和生长方式没有明显的影响;等温结晶温度不影响共混物的结晶机理,但会影响结晶速率,等温结晶温度越高,结晶速率越慢。     

POM/PBS共混纤维的结构与性能研究

采用聚丁二酸丁二醇酯(PBS)对聚甲醛(POM)进行改性,经共混纺丝制得POM/PBS共混纤维,研究了POM/PBS共混体系的流变行为以及共混纤维的热稳定性、结晶结构和力学性能。结果表明:PBS对POM有一定的增塑作用,可以降低POM的黏度和剪切敏感性;添加PBS可降低共混体系的熔点、结晶温度和结晶度,POM的熔点为168.6℃,结晶温度为145.6℃,结晶度为78.6%,而加入PBS质量分数20%的POM/PBS共混体系的熔点为165.7℃,结晶温度为139.7℃,结晶度为68.9%;PBS增大了POM的球晶尺寸,但PBS质量分数超过15%时,由于发生相分离而产生PBS的环带球晶;当PBS质量分数为10%时,POM/PBS共混纤维力学性能最好,拉伸强度和弹性模量分别达到1 264 MPa,9.5 GPa,相比纯POM纤维分别增加了25.8%和15.9%。     

不同结构低分子质量PBS基共聚物的性能

通过控制反应条件的方法,以己二酸(BA)、乙二醇(EG)、己二醇(HS)作为改性PBS的共聚单体,合成了几种低分子质量的PBS基共聚物。采用1H-NMR、FT-IR表征了共聚物的化学结构;WXRD、TGA、DSC对共聚物的性能进行了研究。结果表明:酯化时间为2 h,抽真空时间在30 min以内时,能够得到数均分子质量5 000以上的PBS基共聚物。对于相近分子质量的不同共聚物,聚合后结晶形态没有明显变化,但结晶度和熔点都有所下降;相比PBS,P(BS-co-BA)和P(BS-co-EG)的热分解温度都有所增加,而P(BS-co-HS)的有所降低,但分解温度仍在300℃以上。     

PBS及其共聚酯生物降解性能的研究进展

综述了PBS(聚丁二酸丁二醇酯)、PBS基脂肪族共聚酯,PBS基芳香族共聚酯的结构和生物降解性能,并分别总结了它们的结构和生物降解性能之间的关系.PBS基脂肪族共聚酯分为线型PBS基脂肪族共聚酯和枝状PBS基脂肪族共聚酯,分别对它们进行了介绍.得出了PBS及其共聚酯的结构、分子量、聚酯形态、熔点、结晶度等与共聚酯的生物降解性之间的关系.     

纳米SiO_2表面引发接枝PA6的制备

以己内酰胺钠为引发剂,使纳米SiO_2(nano-SiO_2)表面羟基与过量2,4-甲苯二异氰酸酯反应,再用己内酰胺(CL)封端制备CL接枝nano-SiO_2(nano-SiO_2-g-CL);以其产物为活化剂,使CL在nano-SiO_2表面引发阴离子聚合,制备nano-SiO_2接枝聚酰胺(PA)6(PA 6-g-nano-SiO_2)。相比于水解聚合,表面引发的阴离子聚合能在较低的温度(170℃)下进行。研究表明,nano-SiO_2颗粒均匀地分散在PA 6基体中,并影响PA 6-g-nano-SiO_2的结晶性而导致熔点降低,且其热稳定性提高。     

十二内酰胺两段式水解聚合合成PA12的研究

以十二内酰胺为单体,采用两段式水解聚合工艺合成聚十二内酰胺(PA 12),考察了两段聚合工艺条件以及不同种类的催化剂和相对分子质量调节剂对PA 12的重均相对分子质量(Mw)及其结构与性能的影响。结果表明:较佳的水解聚合工艺条件是以200 g十二内酰胺单体为基准,水的加入量为40 g,己二酸的加入量为0.8 g,高压段反应温度为280℃,高压段反应时间为3 h,常压段反应温度为260℃,常压段反应时间为1.5 h,得到的PA 12的Mw为4.4×104,与工业化PA 12相当;当己二酸或醋酸的加入量相同时,得到的PA 12的Mw相当,结晶温度、熔点和相对结晶度几乎相同,但己二酸催化得到的PA 12的热稳定性稍优,作为催化剂和相对分子质量调节剂,己二酸略优于醋酸。     

聚丁二酸乙二醇酯及其共聚酯的生物降解性能

通过降解过程的质量损失率、相对分子质量及其分布、热性能、表面形貌等评价手段,重点考察了Aspergillus niger脂肪酶对聚丁二酸乙二醇酯(PES)和聚(丁二酸乙二醇-共-对苯二甲酸乙二醇酯)(PEST)的降解性能。结果表明:PES在脂肪酶溶液中具有较好的生物降解性能,随着对苯二甲酸摩尔含量的增加,PEST的质量损失率呈现先增加后逐渐减少的趋势;随着酶解时间的延长,残留部分的PES、PEST的相对分子质量均呈下降趋势;残留部分的PES、PEST的熔点随降解时间的延长变化不大,熔融热焓有所增加;聚酯薄膜表面产生了不同程度的沟槽、孔洞和裂纹。可以推测,PES及PEST的生物降解首先发生在无定形区,并且大分子链段发生的是随机断裂。     

Inferential estimation of molecular weights of polybutadiene rubber by neural networks

Molecular weight distribution, which is characterized by its averages like number average (Mn) and weight average (Mw), is one of the important properties of polybutadiene rubber (PBR), and it is difficult to measure. The objective of this work is to develop models to predict Mn and Mw from readily available process variables. Neural networks that are capable of mapping highly complex and non‐linear dependencies have been adapted to develop models for the Mn and Mw of PBR. The molecular weight distribution and its averages of PBR samples collected over a wide range of operating conditions were measured by the conventional Gel Permeable Chromatograph (GPC) method. Neural networks were trained with relevant data to predict Mn and Mw from process variables. The trained networks were found to generalize well when tested with new data. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1611–1618, 2005     

In situ polymerized nanocomposites of poly(butylene succinate)/Tio2 nanofibers: molecular weight,morphology, and thermal properties

In this study, the nanocomposites of poly(butylene succinate) (PBS) and TiO₂ nanofibers were first synthesized via in situ polymerization. Molecular weight, morphology, and thermal properties of the nanocomposites were characterized. As the weight percentage of TiO₂ nanofibers increased from 0 to 2%, the molecular weight of PBS in the nanocomposites decreased gradually compared with that of pure PBS. In morphology, the nanocomposites were constituted by free PBS and PBS‐grafted TiO₂ nanofibers (PBS‐g‐TiO₂), which were proved by the Fourier transform infrared, scanning electron microscopy (SEM), and transmission electron microscopy. In addition, the SEM demonstrated the strong interfacial interaction and homogeneous distribution between TiO₂ nanofibers and PBS matrix. The thermal properties determined by differential scanning calorimetry and thermogravimetric analysis included the increasing of cold crystallization temperatures, the melting temperatures, and the thermal stability. Besides, the crystallinity and the rate of crystallization of the nanocomposites were enhanced, which were also observed by the X‐ray diffraction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

In vitro hydrolytic degradation of poly(para-dioxanone) with high molecular weight

The in vitro hydrolytic degradation of high molecular weight poly (para-dioxanone) was studied by examining the changes of weight retention, water absorption, pH value, tensile strength, break elongation, thermal properties, and morphology of high molecular weight PPDO in phosphate buffered saline (PBS) (pH 7.44) at 37°C for 8 weeks. During the degradation, all samples’ weight retention decreased and water absorption increased significantly, whereas hydrolysis rate of PPDO bars varied with molecular weight. Compared with lower molecular weight samples, higher molecular weight PPDO samples exhibited higher hydrolysis rate. The samples’ glass transition temperature (Tg) decreased notably, while the degrees of crystallinity (Dc) increased. The samples almost totally lost their tensile strengths and breaking elongation after 4 weeks of degradation. The results suggested that the stability of PPDO in vitro hydrolytic degradation increased with the increase of molecular weight.     

PPDO/PLLA皮芯复合单丝的体外降解

在磷酸盐(PBS)缓冲溶液中,对熔纺得到的两种聚对二氧环己酮(PPDO)/左旋聚乳酸(PLLA)皮芯复合单丝进行体外降解性能研究。结果表明:随着降解时间的延长,两种单丝的吸水率、质量损失率不断增加,相对黏度、强度保留率、断裂伸长率和缓冲溶液的p H值不断降低;随着降解时间的延长,两种单丝的熔融焓逐步升高;随着降解时间的延长,PPDO-PLLA单丝的表面形貌变化比PLLA-PPDO单丝的大,即PPDO的降解速率比PLLA更快。     

Molecular Weight Analysis of Blue Shark (Prionace glauca) Collagen Hydrolysates by GPC-LS; Effect of High Molecular Weight Hydrolysates on Fibroblast Cultures: mRNA Collagen Type I Expression and Synthesis

High molecular weight (Mw) collagen hydrolysates have been demonstrated to produce a higher synthesis of collagen type I mRNA. Mw determination is a key factor maximizing the effect of collagen hydrolysates on collagen type I synthesis by fibroblasts. This work aimed to achieve a high average Mw in Blue Shark Collagen Hydrolysate, studying different hydrolysis parameters by GPC-LS analysis and testing its effect on mRNA Type I collagen expression. Analysis revealed differences in blue shark collagen hydrolysates Mw depending on hydrolysis conditions. Papain leads to obtaining a significantly higher Mw hydrolysate than Alcalase at different times of hydrolysis and at different enzyme/substrate ratios. Besides, the time of the hydrolysis factor is more determinant than the enzyme/substrate ratio factor for obtaining a higher or lower hydrolysate Mw when using Papain as the enzyme. Contrary, Alcalase hydrolysates resulted in similar Mw with no significant differences between different conditions of hydrolysis assayed. Blue shark collagen hydrolysate showing the highest Mw showed neither cytotoxic nor proliferation effect on fibroblast cell culture. Besides, it exhibited an increasing effect on both mRNA expression and pro-collagen I production.     

Phase behavior and morphology in blends of poly(L‐lactic acid) and poly(butylene succinate)

Blends of poly(L ‐lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared with various compositions by a melt‐mixing method and the phase behavior, miscibility, and morphology were investigated using differential scanning calorimetry, wide‐angle X‐ray diffraction, small‐angle X‐ray scattering techniques, and polarized optical microscopy. The blend system exhibited a single glass transition over the entire composition range and its temperature decreased with an increasing weight fraction of the PBS component, but this depression was not significantly large. The DSC thermograms showed two distinct melting peaks over the entire composition range, indicating that these materials was classified as semicrystalline/semicrystalline blends. A depression of the equilibrium melting point of the PLA component was observed and the interaction parameter between PLA and PBS showed a negative value of ?0.15, which was derived using the Flory–Huggins equation. Small‐angle X‐ray scattering revealed that, in the blend system, the PBS component was expelled out of the interlamellar regions of PLA, which led to a significant decrease of a long‐period, amorphous layer thickness of PLA. For more than a 40% PBS content, significant crystallization‐induced phase separation was observed by polarized optical microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 647–655, 2002     

(丁二酸丁二酯/丁二酸己二酯)共聚物的合成及性能

以丁二酸、丁二醇、己二醇为原料,在十氢萘中进行直接缩聚反应,合成了高分子量(丁二酸丁二酯／丁二酸己二酯)共聚物,产率达到95％以上。FT—IR和^1H—NMR图谱表明,共聚物的结构为预期结构;GPC测试结果表明,共聚物均具有较高的分子量;与聚丁二酸丁二酯(PBS)相比,共聚物的拉伸强度显著降低,但断裂伸长率有所提高：DSC测试结果表明,共聚物的结晶度明显低于PBS,其熔点、结晶温度随体系中丁二酸己二酯单元的增加而降低：TG测试结果表明,共聚物均具有较好的热稳定性。     

不同分子质量阻燃共聚酯的非等温结晶动力学

为了探究分子质量和共聚结构对阻燃共聚酯结晶动力学的影响,采用差示扫描量热仪对不同分子质量的阻燃共聚酯进行非等温结晶测试,并进行结晶动力学分析.结果表明:在聚酯中通过共聚反应引入共聚阻燃结构单元后,共聚酯的熔点降低,降温过程中的起始结晶温度和结晶峰温降低,分子质量较大的阻燃共聚酯的结晶温度有所下降,但这种影响并不明显;阻...