医用水凝胶力学性能的研究进展

水凝胶是一类由亲水性聚合物链通过多种交联机制而形成的三维网络结构,具有良好的生物相容性、降解性及可调节的力学性能,广泛用于医药领域。针对不同的临床应用场景,水凝胶需要具备不同的力学性能,但目前尚无统一、系统的量化评价标准,无法针对不同临床应用需求特异性地调节水凝胶性能,限制了此类制剂应用。本文系统总结了医用水凝胶的临床应用及相应的力学性能要求、力学性能的表征手段及调节方法,并对医用水凝胶的发展现状进行总结和展望,希望为医用水凝胶力学性能的研究和发展提供理论基础。     

Mechanical properties of epitaxially crystallized 1,4-polybutadiene on uniaxially oriented isotactic polypropylene

The structure and mechanical properties of polypropylene (PP)-trans-1,4-polybutadiene (PBD) blends were investigated. It was found that PBD can epitaxially crystallize on PP. An increase in mechanical properties (Young's modulus, fracture stress) is observed, despite the fact that pure PBD has much worse mechanical properties compared to PP. The epitaxial morphology is responsible for the synergetic effects in the mechanical properties.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday     

Effects of fused deposition modeling process parameters on tensile,dynamic mechanical properties of 3D printed polylactic acid materials

Fused deposition modeling (FDM) is an important process among the available additive manufacturing technologies in various industries. Although there exists many works investigating the effects of FDM process parameters on the mechanical properties of printed materials, there are still several points need to be studied. One is the effects of process parameters on the dynamic mechanical properties of FDM-printed materials, especially in environments where the temperature often changes. The other is the mechanism by which process parameters affect the mechanical properties of printed materials. Aiming at these two points, uniaxial tensile tests and dynamic mechanical analysis are carried out respectively to characterize the tensile properties and dynamic mechanical properties of FDM-printed PLA materials under different FDM process parameters, namely printing angle, layer thickness, fill rate and nozzle temperature. Based on the experimental results explanations are given for the influence of the FDM process parameters on the mechanical properties of the printed materials.     

核壳结构对聚苯乙烯／聚丙烯酸酯LIPN力学性能的影响

本文系统研究了核壳结构对聚苯乙烯/聚丙烯酸酯(PS/PA)LIPN力学性能的影响.通过改变加料顺序、溶胀时间及双相互穿等多步聚合方法,考察了动态力学和力学性能变化的规律.结果表明,核壳结构随加料顺序的变化,导致力学性能相差十分悬殊.增加溶胀时间及采用多步聚合的双相互穿,能明显地提高互穿程度,使玻璃化温度发生内移,力学性能得到改善.     

A method for more accurate FEA results on a medical device developed by 3D technologies

At present, 3‐dimensional models of all additive manufactured objects (AMOs) are accepted as a solid model for finite element analysis (FEA). FEA of AMOs may not reveal the real results because mechanical properties of default materials in CAD software and newly built AMOs are not equal to each other. This may produce problems especially for the end user due to unexpected failure or wear off. The aim of this study was to compare FEA results of an additive manufactured Ankle Foot Orthosis model under 2 different value sets, namely default material‐based mechanical properties and measured mechanical properties. In order to determine the real mechanical properties of the additive manufactured Ankle Foot Orthosis, 3‐dimensional printed test specimens with different infill densities were prepared and tested according to the recommended standards. Mechanical test results were then loaded in the CAD software and FEA was performed. This study illustrated that default mechanical properties of existing materials in CAD software produce misleading simulation results for AMOs, ie, real mechanical properties should be used to get more accurate results.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

Determination of mechanical properties of silica compounds using a curing kinetic model

Curing is the final step in rubber goods production and the mechanical properties of the vulcanized items, strongly depend on the processing conditions. The objective of this research is to predict the mechanical properties of SBR silica compound using kinetic data obtained from curemeter measurements. The model proposed is based on two curing parameters and on mechanical properties measured in the cured and uncured state. Results showed that the model is able to accurately predict the mechanical properties of the isothermal cured compound and therefore has potential application in the non-isothermal curing cycle optimization.     

Tube-like natural halloysite/fluoroelastomer nanocomposites with simultaneous enhanced mechanical, dynamic mechanical and thermal properties

A novel kind of fluoroelastomer nanocomposites based on tube-like halloysite clay mineral were successfully prepared using a bis-phenol curing system, which resulted in prominent improvements in mechanical and dynamic mechanical properties and in the elevation as high as 30 K of the thermal decomposition temperature. Wide-angle X-ray scattering and transmission electron microscopy techniques were employed to assess the morphology developed in the nanocomposites, while stress strain diagrams were used to evaluate the mechanical properties. These nanocomposites were further characterized by moving die rheometer, dynamic mechanical properties and thermo-gravimetric analysis. Structure-properties relationship and the improvement of the mechanical, dynamic mechanical and thermal properties of fluoroelastomers are reported in the present study. Increasing amount of the filler reduced the curing efficiency of the bis-phenol curing system, which was evident from the rheometric and physical properties of the resulting composites. A sort of filler–filler interaction was perceived during the strain sweep analysis of the composites. The polymer–filler interaction was reflected in the improved mechanical and thermal properties which were the consequence of proper dispersion of the nanotubes in the polymer matrix; whereas the intercalation of macromolecular chains into the nanotubes was not reflected in the X-ray diffraction analysis.     

聚氨酯弹性体力学性能影响因素探讨

研究了合成方法、原料的种类与配比、硫化工艺条件等因素对聚氨酯弹性体力学性能的影响。结果表明,聚氨酯弹性体的结构与组成以及由此引起的微相分离程度的变化是影响弹性体性能的重要因素。对于同样的聚合多元醇、二异氰酸酯及扩链剂合成的弹性体,采用不同的硫化及熟化条件其力学性能不同,并找到达到最佳力学性能所需的工艺条件。     

Investigation of degradation mechanisms in mechanical properties of polyimide films exposed to a low earth orbit environment

The degradation of the mechanical properties of polyimide films was evaluated by means of tensile tests after exposure to a low earth orbit (LEO) environment. Polyimide films irradiated with atomic oxygen (AO), ultraviolet (UV) light, and electron beam (EB) rays using ground simulation facilities were also evaluated similarly and compared. In these experiments tensile stress (7.0 MPa or less) was applied to the samples in order to assess its effects on mechanical properties. The mechanical properties of the flight samples decreased concomitantly with increased exposure duration. The fracture surfaces exhibited characteristic radiated patterns initiating from the exposed surfaces which showed a rough texture. In the AO-irradiated samples the mechanical properties degraded and the surface texture developed as the AO fluence increased; similar fracture surfaces appeared in the flight samples. In contrast, UV and EB irradiation had little impact on mechanical properties. Based on these results, the eroded surfaces by AO irradiation served as the starting points of the rupture, resulting in degradation of mechanical properties of polyimide films exposed to a LEO environment. The tensile stress states induced no difference in evaluations.     

Influence of manufacturing conditions on measurement of mechanical material properties on thermoplastic micro tensile bars

Injection moulding of thermoplastic micro parts result in modified material behaviour due to process induced changes of the internal properties. Thus, a transfer of the mechanical material properties, determined and valid on standardized test specimens, to micro parts is only possible to a restricted extent. Tensile bars with scaled dimensions are used to investigate the influence of part size with injection moulded specimens (with size depending process conditions) and milled specimens (without size depending process conditions). Milled scaled tensile bars provide comparable and reproducible mechanical material properties due to their identical morphological structure. Injection moulded scaled tensile bars have a size dependent morphology which can lead to modified mechanical properties. It is shown that the mechanical properties of thermoplastic polymers react differently with reduced dimensions, especially due to the crystallisation behaviour.     

可调制润湿性和力学性能的电纺纤维膜的制备与性能研究

采用静电纺丝技术分别制备了无规排列和高度取向排列的聚对苯二甲酸乙二醇酯(PET)和PET/CA(柠檬酸)4种纤维膜,对它们的润湿性能和力学性能进行了研究,同时研究了纤维膜厚度对膜的力学性能的影响.研究结果表明,与无规排列的PET纤维膜相比,取向排列的PET纤维膜沿纤维取向方向的力学性能有了很大的提高,而断裂伸长率略有下降;加入柠檬酸(CA)后,PET/CA复合纤维膜的表面水接触角从132.3!减少到0!,且取向排列的纤维膜比无规排列的纤维膜更易润湿;无规排列的复合纤维膜的力学性能因加入CA而大幅下降,取向排列的PET/CA纤维膜沿纤维取向方向的力学性能下降较小,而无规排列的PET/CA纤维膜的断裂伸长率从284.1%增加到444.5%.无规排列纤维膜的力学性能随膜厚度的增加先提高,后来又下降,而取向排列的纤维膜沿纤维取向方向的力学性能随膜厚度增加而单调增加.     

热塑性淀粉/乙烯-乙烯醇共聚物复合材料的制备与性能

利用熔融共混的方法,制备得到热塑性淀粉/乙烯-乙烯醇共聚物（TPS/EVOH）复合材料,并对该复合体系的加工性能、机械性能、动态力学性能、流变性能以及吸水性进行了研究.结果表明：随着EVOH含量增加,复合材料中分子间作用力加强;复合体系的机械性能得到改善;当EVOH含量到达30%后,复合材料的吸水性明显降低.     

Design of polyphosphazene hydrogels with improved structural properties by use of star-shaped multithiol crosslinkers

The feasibility of using a star-shaped crosslinker to produce a hydrogel with controlled mechanical properties and degradation rates was investigated. The aqueous blends of functional polymers and crosslinkers formed a solution at low temperature and a hydrogel with desired mechanical properties at body temperature. The introduction of star-shaped crosslinkers affected the microscopic and macroscopic properties of the hydrogel. The fabricated hydrogels could be suitable for many potential biomedical applications because of their injectability, tunable mechanical properties, controlled degradation rate and gel formation under physiological conditions.     

EP-g-PU IPN结构阻尼材料

采用-NCO封端的聚氧酯(PU)预聚物,制备了环氧树脂-聚氨酯互穿网络(EP-g-PU IPN);通过添加受阻酚四[β-(3,5-二叔丁基-4-羟基苯基)丙酸]季戊四醇(AO-60)制备了AO-60/EP-g-PU IPN.通过FT-IR、DMA、SEM分别研究了改性分子链的基团变化、改性体系的动态性能及断裂面的形态,...     

Properties and hydrolysis of PLGA and PLLA cross-linked with electron beam radiation

Radiation has been used as a processing tool to modify the properties of polymers. The aim of this study is to understand how electron beam radiation, together with pentaerythritol tetraacrylate (PTTA) as a tetra-functional monomer, can alter the properties (i.e. thermal and mechanical) and hydrolysis rates of PLGA and PLLA. The effects of radiation dose and PFM concentration on the physical properties of the polymers were investigated. The results showed that upon irradiation PLGA and PLLA cross-linked, and an increased in gel content was observed. Glass transition temperature (T_g) and mechanical properties of the polymers also increased. Cross-linked PLGA and PLLA samples were found to retard hydrolytic degradation. The mechanical properties of these polymers were also unaffected by hydrolysis. In summary, PLGA and PLLA cross-linked with PTTA were found to have enhanced mechanical properties and were able to retard hydrolytic degradation.     

Morphology and Mechanical Properties of Nylon 6/PBT Blends Compatibilized with Styrene/Maleic Anhydride Copolymer

The mechanical properties and dynamic mechanical properties of blends composed of Nylon 6 and poly(butylenes terephthalate)(PBT),with styrene/maleic anhydride(SMA)as compatibilizer,were studied.The observation on the morphologies of the etched surfaces of the cryogenically fractured specimens via scanning electron microscopy(SEM)demonstrated that in the compatibilized Nylon 6/PBT blends,there exists a finer and more uniform dispersion induced by the in-situ interfacial chemical reactions during the preparation than that in the corresponding uncompatibilized blends.On the other hand,the overall mechanical properties of the compatibilized blends could be remarkably improved compared with those of the uncompatibilized ones.Moreover,increasing the amount of the compatibilizer SMA leads to a more efficient dispersion of the PBT phase in Nylon 6/PBT blends.Furthermore,there exists an optimum level of SMA added to achieve the maximum mechanical properties.As far as the mechanism of this reactive compatibilization is concerned,the enhanced interfacial adhesion is necessary to obtain improved dispersion,stable phase morphology,and better mechanical properties.     

Hierarchies in the structural organization of spider silk—a quantitative model

The unsurpassed mechanical properties of major ampullate spider silk are quantitatively explained by a hierarchical model of its structural organization. Based on combined time-resolved mechanical and Fourier-transform infrared measurements, we show that the core of native silk fibers is strongly prestressed. The prestress is released during wetting, allowing the fibers to shrink, changing permanently the mechanical properties. Prestress is, therefore, the controlling parameter of silk properties.     

Physical, chemical, and chemical-physical double network of zwitterionic hydrogels

Zwitterionic hydrogels are very promising for biomedical applications. They are usually copolymerized with other polymers to improve their mechanical properties often at the expense of their biological properties. In this study, physically cross-linked poly(sulfobetaine methacrylate) (polySBMA) hydrogels were prepared, and their physical properties including phase behavior were investigated. Linear polySBMAs, with an average molecular weight ranging from 20.9 kDa to 316 kDa, were prepared via free radical polymerization at different KCl concentrations. The opaque-transparent phase transition of polySBMA-water mixtures were measured using a UV-vis spectrometer. Analysis from dynamic rheometry showed the formation of physically cross-linked hydrogels with mechanical ductility due to reversible charge interactions. Chemically cross-linked hydrogels were also prepared, and their swelling and mechanical properties were evaluated. It was found that the introduction of cross-linkers could lead to a decrease in the amount of physical cross-links in chemical hydrogels. In order to improve the mechanical properties of SBMA hydrogels, linear polySBMA was introduced to the network of chemically cross-linked polySBMA gels, creating a chemical-physical double network (DN) with both chemical and physical cross-links. The chemical-physical DN provides a desirable method to improve the mechanical properties of zwitterionic hydrogels without introducing other hydrophobic moieties.     

Molecular dynamics simulation of mechanical properties of TATB/fluorine-polymer PBXs along different surfaces

TATB (1,3,5-triamino-2,4,6-trinitrobenzene) is the well-known high insensitive explosive. With TATB as the main body (90% and above) the polymer bonded explosives ( PBXs) contain a small amount of poly-mers (5%―10%). The composite materials with good saf…