耐高温PCT/LCP合金材料的制备与性能

为了开发可适用于1.0 W以上大功率照明的LED反射支架材料,将聚对苯二甲酸1,4-环己烷二甲酯(PCT)与液晶高分子聚合物(LCP)按一定质量比制成了PCT/LCP合金。研究了LCP对PCT/LCP合金的熔融结晶性能、热稳定性、力学性能、耐热氧老化性能的影响,同时研究了PCT/LCP合金制备的LED封装灯珠的高温点灯老化性能。结果表明,LCP在PCT/LCP合金体系中起到了异相成核的作用,提升了合金材料的结晶速度、热稳定性、强度和韧性。在PCT/LCP合金体系中随着LCP含量的增加,合金材料对不同波长光的初始反射率下降,但经过表面贴装技术(SMT)老化后,材料对于不同波长光的反射率变化值和色差值降低,PCT/LCP合金材料耐热氧老化性能提升。PCT/LCP合金制备的LED封装灯珠,高温点灯老化后光维率明显优于PCT基材,研究为PCT/LCP合金应用于1.0 W以上的大功率LED反射支架行业提供了参考。     

抗氧剂PCT在轮胎胎侧配方中的应用研究

研究表明,配合剂与防老剂的类型及用量影响轮胎的外观质量和轮胎表面的老化龟裂性能。研究还显示,抗氧剂PCT和再生橡胶能改善轮胎表面的黑度与外观质量,抗氧剂PCT还能改善胶料的耐臭氧老化龟裂性能;抗氧剂PCT的用量为0.5~2份。     

玻纤增强PBT/PCT合金性能研究

对玻纤增强不同配比PBT/PCT合金的力学性能,热稳定性,耐热氧老化性能进行了研究。结果表明,在玻纤增强PBT/PCT合金体系中,PCT树脂含量的增加会影响玻纤增强PBT/PCT合金体系的力学强度,但PCT树脂含量增加,可以改善PBT/PCT合金体系的韧性;同时合金体系中,PCT树脂含量增加会提高玻纤增强PBT/PCT合金体系的热稳定性; PCT树脂含量的提高对于提升PBT/PCT合金体系的初始和热氧老化后的反射率和亨特白度有利。应用研究为玻纤增强PBT/PCT合金的工业化生产提供了参考。     

玻璃纤维增强PCT/PBT合金性能研究

对不同配比玻璃纤维增强聚对苯二甲酸1,4-环己烷二甲醇酯(PCT)/聚对苯二甲酸丁二醇酯(PBT)合金的冷结晶性能,熔融结晶性能,流动性,耐热氧老化性能进行了研究。结果表明,在玻璃纤维增强PCT/PBT合金体系中,PBT的添加可显著降低PCT的冷结晶温度; PBT或PCT中任何一种组分的加入都会导致另一组分熔点的下降; PCT与PBT会发生一定程度的酯交换反应,形成部分共聚物,但共混体系两组分是分别结晶的,并不能形成共晶或混晶; PBT含量的提高会明显改善合金体系的流动性,但合金体系的初始反射率和长期耐热氧老化性能会下降。     

腰果酚醛胺固化环氧树脂泡沫塑料性能研究

以双酚A型环氧树脂(EP)为基体树脂、自制的腰果酚醛胺(PCT)为固化剂、正戊烷(N-PT)为发泡剂、吐温-80和二甲基硅油为稳泡剂室温发泡制备新型环氧树脂泡沫塑料。研究了PCT用量对发泡时间和泡沫性能的影响,通过扫描电子显微镜和热失重分析对泡沫塑料的微观形貌和热性能进行了表征。结果表明,随着PCT用量增加,发泡时间逐渐缩短;环氧树脂泡沫塑料的密度、压缩强度、吸水率和热导率均随PCT用量的增加呈现先减小后增大趋势;当PCT加入量为30 %(相对于纯EP)时,发泡时间降至5 min;泡沫塑料的综合性能较佳,密度为0.0467 g/cm^3、压缩强度为276 kPa、吸水率为2.9 %、热导率为0.037 W/m·K,此时泡孔大小均匀,不良泡孔少;泡沫初始失重温度为248.4 ℃,最大失重速率温度为362.3 ℃,耐热性最佳。     

国外动态

耐热聚酯PCT最近由Ge公司和Eastman公司联合开发,已使第三类型热塑性聚酯-聚环已撑二甲基对苯二酸盐(PCT)商业化。该材料的性能集中了PBT和PET两类结晶型聚酯的优点,它有PBT的强度和机械轫性,并且耐热性优于PET,是目     

苯胺改性酚醛树脂胶粘剂的研究

本文探讨了苯胺改性酚醛树脂的原理及合成过程，经PCT－1型热分析仪对树脂的分析以及摩擦材料应用试验表明，改性树脂的耐热性和产品性能明显提高．     

FEVE涂覆型光伏背膜涂料的研制

介绍了FEVE涂覆型光伏背膜的应用现状,并采用醚型氟树脂、纳米功能填料及附着力促进树脂制备了性能优异的涂覆型光伏背膜涂料,形成的涂膜具有较好的耐候性、耐腐蚀性和绝缘性。探讨了涂膜对PET基材附着力、PCT老化及EVA粘接性能的影响。     

PCT及其共聚酯的开发概况及应用

简述了PCT及其改性聚酯的工艺原理,综述了有关PCT及其共聚酯的开发现状和研究概况,并指出其应用领域。     

太阳能电池背板用PE膜的耐候性能研究

以线型低密度聚乙烯(LLDPE)和低密度聚乙烯(LDPE)为主体树脂,探讨了白色母粒对太阳能电池背板用聚乙烯(PE)膜力学性能的影响,同时研究了抗老化母粒对PE膜耐高温高湿(PCT)老化性能和耐候性的影响。结果表明:加入白色母粒可以在一定程度提高PE膜的拉伸强度;随着抗老化母粒用量的增加,PCT老化50h后的PE/聚对苯二甲酸乙二醇酯(PET)剥离强度逐步下降;在添加量相同的条件下,抗老化母粒呈均匀分布的PE膜,其耐候性优于抗老化母粒呈正态分布的PE膜。     

A novel potential cationic polymeric gene vector containing hydroxy groups and all grades of amino groups

A novel potential cationic polymeric gene vector, PCT, was synthesized by copolymerizing 3‐chloro‐1,2‐epoxypropane (CEP) and tetraethylene pentamine (TEPA). The protonizable nitrogen content of PCT is 17.7 mmol/g at 1 : 1 of CEP to TEPA, lower than 23.3 mmol/g of polyethylenimine (PEI) but higher than 7.8 mmol/g of polylysine, which indicates PCT is a candidate of polycation with high‐content but discrete charge after protonation. PCT has many hydrophilic quaternized amino and hydroxy groups contributing to hydrophilicity. Acid base titration showed that PCT was protonated in both pH 7.4–11 and pH 5.0–7.4 and had “proton sponge effect.” In aqueous solution, PCT complexed with weak anionic polymer, poly(acrylic acid) (PAA), into nanoparticles. Fourier transform infrared spectroscopy proved the formation of complex. Particle size is first increased and then decreased as increasing mass ratio θ of PCT to PAA from 0.1 to 1.7, as shown by dynamic light scattering. At θ values of more than 1.7 or less than 0.2, complex particles with mean diameter less than 200 nm were obtained. At θ of 0.5, the UV‐Vis absorbance of complex solution at first day was obviously higher than that at 7 day, while at θ of 1.7, two absorbance curves at these two time points had slightly smaller change, indicating that small complex particles were more stable than large ones because of electrostatic repulsion. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Supramolecular selectivity of poly(ethylene oxide) in semi‐crystalline polymer nanocomposites

Semi‐crystalline polymer nanocomposites were prepared using successive meltings and recrystallizations techniques by intercalation of small guest molecules such as 4‐chlorotoluene (PCT), 4‐bromotoluene (PBT) and 1,4‐dibromobenzene (PDBB) into poly(ethylene oxide) (PEO) crystals. Differential scanning calorimetry, Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction experimental results show that supramolecular selectivity exists for the PEO–PDBB/PBT ternary system, while there is no supramolecular selectivity for PEO–PCT/PBT ternary nanocomposites. The interactions between PEO chains and small guest molecules have an important influence on the polymer conformation, which results in the dramatic difference in intercalation behavior. Copyright © 2007 Society of Chemical Industry     

Miscibility of poly(1,4‐cyclohexamethylene terephthalate) blends with polyarylate

The miscibility of poly(1,4‐cyclohexamethylene terephthalate) (PCT) having an aliphatic cyclic segment blended with Polyarylate (PAR) was investigated by means of calorimetric measurements. It was found that all the PCT/PAR blends are miscible and show a single, composition‐dependent glass transition temperature (T_g). The T_g composition dependence has been analyzed by using the Gordon–Taylor equation and the values of T_g obtained experimentally agree quite well with those calculated theoretically by using that equation. Also, the melting point depression phenomenon that occurred in miscible polymer pairs was observed up to 40 wt % PCT content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1947–000, 2000     

Predictive Ability of Procalcitonin for Acute Kidney Injury: A Narrative Review Focusing on the Interference of Infection

Acute kidney injury (AKI) is a common yet complicated clinical entity with high morbidity and mortality. An essential strategy to improve AKI patients’ prognoses is finding optimal biomarkers to identify AKI in a timely manner. Procalcitonin (PCT), a well-recognized biomarker for diagnosing infection and guiding antibiotics therapy, has been proposed to predict AKI development and recovery in many clinical settings. The current review provides comprehensive and updated information from relevant studies to evaluate PCT’s AKI-predictive ability and the influence of infection on this predictive ability. PCT has demonstrated optimal predictive ability for AKI in various populations irrespective of infection. However, the predictive ability seems to be blunted by infection since infection and inflammation have a more potent influence than AKI on PCT elevation. We furthermore explain the complicated association between elevated PCT levels and AKI in infection and inflammation situations and recommend directions for further investigations to clarify the essential issue. In conclusion, although conflicting data exist, serum PCT level is a potential biomarker for predicting AKI in many clinical settings regardless of infection. Nevertheless, further studies are warranted to clarify the association between PCT, infection, and AKI and to confirm the utilization of PCT for AKI prediction.     

PET-PCT共聚酯的制备及其热性能研究

由直接酯化法制备了不同1,4-环己烷二甲醇(CHDM)含量的聚对苯二甲酸乙二醇酯-聚对苯二甲酸-1,4-环己烷二甲醇酯(PET-PCT)共聚酯;利用核磁共振表征了合成产物的实际组成及序列结构;采用差示扫描量热和热失重分析研究了共聚酯的结晶特性和热稳定性。结果表明:合成的共聚酯为无规嵌段聚合物,PCT的实际组成均高于投料比,各链段的序列长度与其含量成正比。随着CHDM含量的增加,共聚酯的玻璃化转变温度升高,退火后的试样在低温处和高温处出现了两个熔点,且熔点和焓值随PCT含量的增加而降低。合成产物热稳定性优良,起始分解温度均大于400℃,最大分解温度大于435℃。用Friedman法对热分解动力学的分析,进一步证明共聚酯的热稳定性优良。     

Electrical and Pyroelectric Properties of Highly (001)-Oriented (Pb0.76Ca0.24)TiO3 Thin Films Grown by a Sol–Gel Process

Highly (001)-oriented (Pb_0.76Ca_0.24)TiO₃ (PCT) thin films were grown on Pt/Ti/SiO₂/Si substrates using a sol–gel process. The PCT film with a highly (001) orientation showed well-saturated hysteresis loops at an applied field of 800 kV/cm, with remanent polarization ( P _r) and coercive electric field ( E _c) values of 23.6 μC/cm² and 225 kV/cm, respectively. At 100 kHz, the dielectric constant and dielectric loss values of these films were 117 and 0.010, respectively. The leakage-current density of the PCT film was 6.15 × 10⁻⁸A/cm² at 5 V. The pyroelectric coefficient ( p ) of the PCT film was measured using a dynamic technique. At room temperature, the p values and figures-of-merit ( F _D) of the PCT film were 185 μC/m²K and 1.79 × 10⁻⁵ Pa^−0.5, respectively.     

Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer

Structural, microstructural and ferroelectric properties of Pb_0.90Ca_0.10TiO₃ (PCT10) thin films deposited using La_0.50Sr_0.50CoO₃ (LSCO) thin films which serve only as a buffer layer were compared with properties of the thin films grown using a platinum-coated silicon substrate. LSCO and PCT10 thin films were grown using the chemical solution deposition method and heat-treated in an oxygen atmosphere at 700 °C and 650 °C in a tube oven, respectively. X-ray diffraction (XRD) and Raman spectroscopy results showed that PCT10 thin films deposited directly on a platinum-coated silicon substrate exhibit a strong tetragonal character while thin films with the LSCO buffer layer displayed a smaller tetragonal character. Surface morphology observations by atomic force microscopy (AFM) revealed that PCT10 thin films with a LSCO buffer layer had a smoother surface and smaller grain size compared with thin films grown on a platinum-coated silicon substrate. Additionally, the capacitance versus voltage curves and hysteresis loop measurement indicated that the degree of polarization decreased for PCT10 thin films on a LSCO buffer layer compared with PCT10 thin films deposited directly on a platinum-coated silicon substrate. This phenomenon can be described as the smaller shift off-center of Ti atoms along the c-direction 〈001〉 inside the TiO₆ octahedron unit due to the reduction of lattice parameters. Remnant polarization (P_r) values are about 30 μC/cm² and 12 μC/cm² for PCT10/Pt and PCT10/LSCO thin films, respectively. Results showed that the LSCO buffer layer strongly influenced the structural, microstructural and ferroelectric properties of PCT10 thin films.     

Evaluation of poly(1,4-cyclohexylene dimethylene terephthalate) blends for improved processability

Poly(l,4-cyclohexylene dimethylene terephthalate) (PCT) exhibits superior heat deflection temperature when compared to conventional polyesters such as poly(butylene terephthalate) or poly(ethylene terephthalate). It is subject to degradation, however, at the processing temperatures normally employed to extrude or mold this material. Several approaches were taken to broaden the processing window of this material including: blending PCT with other crystalline and amorphous polymers to allow for lower processing temperatures, addition of conventional stabilizers, addition of crosslinking agents to maintain viscosity during processing and the addition of lubricants to improve processing. Key parameters included physical properties, rate of degradation, extruder torque measurements vs. time, and Differential Scanning Calorimetry (DSC) analysis (melting point and glass transition). All systems tested produced significant reduction of the intrinsic viscosity (molecular weight) for PCT during processing. The most successful approach was the blending of various polymers with PCT to lower extruder processing temperatures. Reductions in processing temperature may have resulted from improved heat transfer due to the presence of a lower melting polymer, reduction in melting point of the blend, or changes in the frictional characteristics of the PCT in the extruder. Transesterification may have played a role in compatibilizing some polyester mixtures. As expected, certain polymers had major'effects on the flow behavior of the blend. Tradeoffs were obtained in physical and thermal properties. A combined approach of polymer blending and the use of lubricants, stabilizers or crosslinking agent may hold the most promise for future development work. Thermal resistance under vapor phase soldering conditions was best for LCP/PCT blends and worst for PBT/PCT blends. Additional evaluations of the blend materials will include solvent resistance, processability, thermal resistance, dimensional stability, heat aging resistance, flammability, and specific end use tests.