多种成核剂对PBS结晶及力学性能的影响

本文研究了滑石粉、TMB-5、碳酸钙、硫酸钙晶须、高岭土等五种成核剂对聚丁二酸丁二醇酯(PBS)结晶行为及力学性能的影响。偏光显微镜的观察结果显示了成核剂能细化PBS的球晶尺寸,提高球晶排列的规整度;热分析结果表明添加成核剂能提高PBS的结晶温度,加快PBS的结晶速率;结晶性能的改善又直接造成PBS力学性能的提高,其拉伸强度和冲击强度都有明显上升。五种成核剂中以滑石粉的效果最为突出,能使PBS的结晶温度上升11℃,拉伸强度提高了4.4MPa。     

不同结构有机成核剂对聚丁二酸丁二醇酯结晶的影响

聚丁二酸丁二醇酯(PBS)是一种具有广泛应用前景的生物可降解高分子,但其加工性能和力学性能受制于结晶性能。本文通过差示扫描量热仪、偏光显微镜、X射线衍射和力学性能测试等手段研究几种不同分子结构有机成核剂对PBS结晶性能及力学性能的影响,寻找PBS高效有机成核剂。结果表明含芳香基团有机成核剂对PBS结晶有明显的促进作用,提高PBS的结晶温度,结晶速率和拉伸性能。     

聚丁二酸丁二醇酯/碳酸钙复合材料老化研究

采用红外光谱(FTIR)、X射线衍射(XRD)、热重分析(TG)等研究了聚丁二酸丁二醇酯/碳酸钙(PBS/CaCO3)复合材料的老化性能。结果表明:老化后PBS/CaCO3的FTIR特征峰强度发生了一定变化;随着老化时间的延长,复合材料的结晶度由25.08%提高到36.56%;PBS/CaCO3复合材料比PBS有更好的热稳定性;老化过程中材料的拉伸强度逐渐下降。     

聚甲基乙撑碳酸酯/聚丁二酸丁二醇酯共混体系性能研究

采用熔融共混法制备了聚甲基乙撑碳酸酯/聚丁二酸丁二醇酯(PPC/PBS)复合材料,通过力学性能、DSC、TG研究了PBS用量对PPC/PBS共混体系力学性能、结晶性能、热稳定性的影响。结果表明:PBS的加入提高了PPC/PBS共混体系的拉伸强度、缺口冲击强度和热稳定性。     

PBS对两种新型聚乳酸复合材料性能的影响

分别以聚乳酸、聚丁二酸丁二醇酯(简称:PBS)及聚乳酸、聚丁二酸丁二醇酯与改性凹凸棒石黏土为原料,制备出两种新型复合材料。考察了不同PBS含量对这两种新型复合材料力学性能与热学性能的影响。结果表明:PBS的加入量越多,拉伸强度、断裂伸长率变化趋势相似,冲击强度与热变形温度变化趋势略有不同。形温度变化趋势略有不同。     

PBS/埃洛石纳米管复合材料的制备与性能

利用Brabender转矩流变仪,通过熔融共混法直接制备了聚丁二酸丁二醇酯(PBS)/埃洛石纳米管(HNT)复合材料。研究了HNT含量对其在PBS基体中的分散性以及复合材料力学性能、热稳定性能和结晶性能的影响。扫描电镜结果显示:在质量分数为10%时,HNT能以单管形式均匀分散在PBS基体中。随着HNT含量的增加,PBS/HNT复合材料的拉伸模量、弯曲强度和弯曲模量显著提高,但其断裂伸长率和热稳定性有所降低。差示扫描量热分析表明:HNT在PBS中能起到异相成核作用,提高了PBS基体的结晶温度和结晶度。     

花生壳纤维增强PBS复合材料的制备及性能

将废弃花生壳纤维作为一种增强材料应用到可降解高分子材料聚丁二酸丁二醇酯（PBS）中，采用熔融共混法制备了聚丁二酸丁二醇酯/花生壳纤维（PBS/F）复合材料，分析了复合材料的结晶性能、热性能及力学性能，并采用分子模拟对性能的改变进行了验证。结果表明：花生壳纤维的添加并没有改变PBS的晶型，但作为成核剂参与了PBS的结晶过程，促进了复合材料的结晶，缩短了复合材料的结晶时间。花生壳纤维含量为5%时其成核作用最强，使其作为“桥梁”镶嵌在复合材料中，结合分子间相互作用使得复合材料的热性能及力学性能较纯PBS有所增加。分子模拟结果表明了花生壳纤维与PBS形成了C=O…H-O，从而增强两者的界面结合。     

纳米氧化锌填充PBS复合材料性能的研究

采用硅烷偶联剂(KH-550)对纳米氧化锌进行了表面改性,通过熔融共混法制备了聚丁二酸丁二醇酯(PBS)/纳米氧化锌复合材料,利用扫描电子显微镜、热重分析仪、差示扫描量热仪等对复合材料的力学性能、热性能和非等温结晶性能进行了研究分析,并通过Ozawa-Flynn-Wall方法分析了复合材料的热降解行为。结果表明,纳米氧化锌能提高PBS的拉伸强度和弯曲强度,但降低了其冲击强度;改性后的纳米氧化锌可以提高其与PBS的界面相容性,并提高其在PBS基体中的分散性能,不同程度地提高了复合材料的力学性能;纳米氧化锌提高了PBS的结晶速率,降低了其热解反应活化能。     

聚丁二酸丁二醇酯/甲壳素晶须复合材料的制备及性能

采用乙酸酐酰化改性甲壳素晶须(CHW),得到乙酰化甲壳素晶须(ACHW),通过FTIR、XRD、TEM表征了ACHW的结构和形态。将CHW和ACHW分别与聚丁二酸丁二醇酯(PBS)通过熔融共混法进行复合,制得了含CHW、ACHW质量分数分别为1%、3%、5%和7%的PBS/CHW、PBS/ACHW复合材料,并测试了其结晶性能、热稳定性能和力学性能的变化;利用ESEM观察了复合材料断面中CHW和ACHW的分散情况。结果表明:ACHW的引入有效改善了ACHW与基体PBS之间的界面相容性;在PBS结晶过程中,ACHW作为成核剂,加快了PBS的结晶速率,但没有改变PBS的晶型;当ACHW的质量分数为3%时,PBS/ACHW复合材料的热稳定性明显提高,Td-5%为349.2℃,Td-max为401.9℃,与纯PBS相比分别提高了53.0℃和33.6℃;拉伸强度由纯PBS的30.9MPa增加到35.8 MPa,断裂伸长率由9.8%增加到17.5%。     

聚丁二酸丁二醇酯成核剂研究进展

聚丁二酸丁二醇酯(PBS)作为脂肪族可生物降解高分子材料,结晶速度缓慢、球晶尺寸大导致其力学性能较差。通过添加成核剂改善PBS的结晶行为,能有效提高PBS的力学性能和加工性能。主要介绍了用于PBS的成核剂的研究进展,包括无机成核剂和有机小分子成核剂,以及最近发现的有机大分子成核剂。与常规类型的成核剂相比,具有特定结构的有机大分子成核剂更能有效地改善PBS的结晶性能,从而提高其力学性能,扩展应用领域。     

Victrex® poly(ethersulfone) (PES) and Victrex® poly(etheretherketone) (PEEK)

Properties of two high performance engineering thermoplastics, amorphous polyethersulfone (PES) and semicrystalline polyetheretherketone (PEEK), are discussed. Both resins can be processed by conventional techniques, compounded with high performance fibers, and have high service temperature (up to 300°C). Due to the amorphous character PES can be dissolved and spray coated into metals.     

Calcium silicate hydrate (II) (“C-S-H(II)”)

This semicrystalline phase, originally named ‘calcium silicate hydrate(II)’ by Taylor (1950), has been studied with X-rays, electron optics, chemical investigation of silicate anion type, infrared spectra, and thermal methods. It is structurally related to jennite (C₉S₆H₁₁) and probably also to the fibrous CSH of cement pastes, the three phases forming a sequence of decreasing crystallinity. The specimen studied had approximate composition C₂SH_3.2 after standing over saturated CaCλ₂ at about 15°C. CSH(II) contains metasilicate chains and pyrosilicate groups and has a disordered layer structure. Much of the water can be lost reversibly without significant change in lattice parameters.     

(Ba_(1-α)Sr_α)_(4.8)(Sm_(0.7)La_(0.3))_(8.8)Ti_(18)O_(54)陶瓷的微波介电性能

采用固相合成法制备了(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54(α=0.1～0.5)系陶瓷,表征了该陶瓷的相组成和显微结构,测试了微波介电性能.结果表明:α=0.3时,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷为单相的新钨青铜结构固溶体.α>0.3时,相继出现了第二相BaLa2Ti4O12和La0.66TiO2.993.随α的增加,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷的相对介电常数(εr)先增大后有所波动,品质因数(Qf)先增大后减小,谐振频率温度系数(τf)单调减小.α=0.3时,在1 350℃烧结的陶瓷的微波介电性能最佳:εr=98.77,Qf=5184GHz,τf=10.9×10-6/℃,优于不掺杂的BaO-Sm2O3-TiO2陶瓷的.     

Photopyroelectric Spectroscopic Studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) Ceramics

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.     

Poly(butadiene-acrylic acid(g)acrylonitrile(g)acrylic acid)

Summary In the present work we describe, the synthesis and characterization of a new gel obtained by crosslinking a cooligomer of butadiene-acrylic acid (BuAA), by reaction with acrylonitrile and acrylic acid. The purified product was characterized by FTIR, elemental analyses and scanning electronic microscopy. The thermal properties were studied and swelling indexes were determined in different solvents and at different pH values. The capacity of poly(butadiene-acrylic acid(g)acrylonitrile(g)acrylic acid) [gel A] to separate different organic substances, such as amino acids and colorants, was determined.     

Thermal studies of blends of poly(phenylene sulfide) (PPS) with poly(phenylene sulfide sulfone) (PPSS) and with poly(phenylene sulfide ether) (PPSE)

The miscibilities of poly(phenylene) sulfide/poly(phenylene sulfide sulfone) (PPS/PPSS) and poly(phenylene) sulfide/poly(phenylene sulfide ether) (PPS/PPSE) blends were invesigated in terms of shifts of glass transition temperatures T_g of pure PPS, PPSS, a dn PPSE. The crystallization kinetics of PPS/PPSS blends was also studied as a function of molar composition. The PPS/PPSS and PPS/PPSE blends are respectively partially and fully miscible. PPSE shows a plasticizing effect on PPS as does PPS on PPSS, which necessarily improves te processibility in the respective systems. We can control T_g and melting temperature T_m of PPS by varying amounts of PPSE in blends. The melt crystallization temperature T_mc of PPS/PPSE blends was higher than that of the PPSE homopolymer. Therefore, these blends require shorter cycle times in processing than pure PPSE. The overall rate of crystallization for PPS/PPSS blends follows the Avrami equation with an exponent ?2. The maximal rate of crystallization for PPS/PPSS blends occurs at a temperatre higher by 10°C than that for PPS, while the crystallization half time t_1/2 is 4 times shorter. In the cold crystallization range, crystal growth rates increase and Avrami exponents decrease significantly as the temperature increases.     

Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Chemical cross-linking of conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using poly(ethylene oxide) (PEO)

Hybrid films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were prepared with different molecular weights of poly(ethylene oxide) (PEO). The cross-linking reaction between PEO and PEDOT:PSS was performed at high temperature and confirmed by using differential scanning calorimeter (DSC), contact angle measurement, and solid-state ¹H NMR. The effect of chemical reaction on the conductivity and morphology of these hybrid films was studied by using 4-point probe and atomic force microscope (AFM), respectively. As-spun PEO/PEDOT:PSS films have lower electric conductivity due to the addition of nonconductive PEO, and exhibits no molecular weight dependence on conductivity. After chemical cross-linking reaction at high temperature, only PEDOT:PSS films with lowest molecular weight PEO additives show enhanced conductivity with increasing reaction time. AFM result indicates that the heat-treated PEO/PEDOT:PSS hybrid films show grain-like morphology compared to ethylene glycol treated PEDOT:PSS films which shows continuous PEDOT domain. In the present work we demonstrate that the cross-linking reaction can be used to improve the wet stability of PEDOT:PSS nanofiber, showing good water resistance and excellent dimensional stability.