聚(3-羟基丁酸酯-co-4-羟基丁酸酯)@海藻酸钠复合纤维膜的制备及其对Pb2+和Cu2+的吸附性

采用三氯甲烷和N,N二甲基甲酰胺（DMF）为溶剂,制备聚（3-羟基丁酸酯-co-4-羟基丁酸酯）（P（3HB-co-4HB））纺丝溶液,并通过静电纺丝技术制备P（3HB-co-4HB）纳米纤维膜,用海藻酸钠（SA）对P（3HB-co-4HB）纳米纤维膜进行包覆,获得P（3HB-co-4HB）@SA复合纤维膜。利用SEM、比表面积仪、原子吸收光谱分别表征了P（3HB-co-4HB）@SA复合纤维膜的纤维形态、比表面积、溶液残留液离子浓度。结果表明:纺丝液浓度在12%时,P（3HB-co-4HB）纤维成纤性好;随着静电压增大,P（3HB-co-4HB）纤维直径先减小后增大。P（3HB-co-4HB）支架材料可以使SA的比表面积提高约3.9倍,P（3HB-co-4HB）@SA复合纤维膜对Cu2+离子、Pb2+离子最大吸附量分别为26.25 mg/g和36.25 mg/g,折算为SA的吸附量分别为364.58 mg/g和503.47 mg/g。      

4-羟基丁酸含量对聚 3-羟基丁酸 与 4-羟基丁酸共聚物性能和结构的影响

目的对3-羟基丁酸4-羟基丁酸共聚酯P(3HB-co-4HB)进行酶解测试。方法通过力学性能测试、失重率分析、热失重分析、X-射线衍射分析、扫描电镜等测试和表征手段对样品的物理性能及生物降解情况进行评价。结果 P(3HB-co-4HB)分子中4HB单体(文中均用摩尔分数表示)的引入提高了材料的柔韧性,材料的脆性下降;失重率方面,4种材料的降解速率从高到低依次为P(3HB)P(3HB-co-5%4HB)(3HB-co-10%4HB)P(3HB-co-15%4HB);酶解前期,材料的热稳定性增强,而酶解后期材料的热稳定性逐渐下降;XRD结果表明材料降解过程中结晶度的变化不明显;P(3HB-co-4HB)分子中随着4HB单体含量的增加,材料表面粗糙度降低,酶解后材料表面被侵蚀,降解速率与失重率结果一致。结论 P(3HB-co-4HB)分子中4HB单体的引入显著影响了材料的机械性能,随着4HB含量的增加,材料的失重率越来越大,热稳定性呈现先上升后下降的趋势,材料表面粗糙度逐渐降低,由于酶解过程属于从表面侵蚀开始,因此酶解过程中样品的结晶度变化不大。     

Isothermal crystallization kinetics and morphology of biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Isothermal crystallization kinetics and morphology of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] with different 4-hydroxybutyrate (4HB) molar fraction were investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). The results show that the crystallization mechanism and crystal structure of P(3HB-co-4HB) copolymers are the similar as those of poly(3-hydroxybutyrate) (PHB). While the equilibrium melting point and crystallization rate decrease with the increase of 4HB molar fraction. Banded spherulites are observed in neat PHB and P(3HB-co-4HB) copolymers, and morphology is influenced apparently by the crystallization temperature and 4HB unit.     

聚丁二酸丁二醇酯/聚羟基烷酸酯熔融共混物的结晶及流变力学行为

用熔融共混法制备聚丁二酸丁二醇酯(PBS)/聚(3-羟基丁酸酯-co-4-羟基丁酸酯)[Poly(3HB-co-4HB)]复合降解材料,利用差示扫描量热(DSC)、旋转流变仪及万能拉力机对其结晶、流变行为及力学性能进行研究。结果表明,在PBS中加入Poly(3HB-co-4HB)后,发现结晶起始温度(To,c)、结晶峰温度(Tp,c)以及结晶结束温度(Te,c)有所提高,结晶度随着Poly(3HB-co-4HB)的增加呈先增大后下降的趋势;PBS/Poly(3HB-co-4HB)复合降解材料随着Poly(3HB-co-4HB)添加量的增大,断裂伸长率和拉伸强度却呈下降趋势;同时剪切储能模量(G′)、剪切损耗模量(G″)呈现出单增趋势。因此,在复合降解材料中添加适量的Poly(3HB-co-4HB)能改善PBS的结晶、流变及力学行为。     

GF/P(3HB-co-4HB)-PLA生物基复合材料的制备与性能

为了提高聚（3-羟基丁酸酯-co-4 羟基丁酸酯）-聚乳酸（P（3HB-co-4HB）-PLA）生物基共混材料的力学性能和尺寸稳定性,扩大应用领域,以P（3HB-co-4HB）和PLA共混物为基体,盐酸或偶联剂表面处理的玻璃纤维（GF）为增强材料,采用熔融共混法制备GF/P（3HB-co-4HB）-PLA复合材料。通过傅里叶变换红外光谱仪（FTIR）、扫描电子显微镜（SEM）、热失重分析仪（TGA）和万能电子拉力机等研究了GF表面处理方法对复合材料力学性能、热性能、尺寸稳定性及断面形态的影响。研究结果表明：表面改性GF的加入可显著提高P（3HB-co-4HB）-PLA共混材料的综合性能。经偶联剂表面接枝的GF可均匀分散在P（3HB-co-4HB）-PLA基体中并形成较强的界面结合。添加质量分数20%的偶联剂改性GF使复合材料的拉伸强度、弯曲强度、缺口冲击强度和硬度分别提高了29.38%、20.32%、41.38%和15.31%;初始热分解温度（IDT）和维卡软化温度（VST）分别提高了6.64 ℃和10.7 ℃;室温和60 ℃放置60 d后复合材料试样长度方向的尺寸稳定性分别提高了32.47%和33.70%。     

成核剂对聚(3-羟基丁酸酯-co-4羟基丁酸酯)性能的影响

分别以氮化硼(BN)、BRUGGOLENP250、CaCO3和Tm-3为成核剂,用熔融模压法制备了聚(3-羟基丁酸酯-co-4羟基丁酸酯)[P(3HB-co-4HB)]样品,借用偏光显微镜(POM)、差示扫描量热(DSC)、热重分析(TGA)和扫描电镜(SEM)等考察了成核剂种类及用量对P(3HB-co-4HB)结晶形态、熔点、热分解温度、力学性能及断面形态的影响。结果表明,各种成核剂均能有效细化P(3HB-co-4HB)的球晶尺寸,提高其熔点及热分解温度;当成核剂BN的质量分数为5‰~8‰时,P(3HB-co-4HB)的综合性能最好。     

A comparative investigation of biodegradable polyhydroxyalkanoate films as matrices for in vitro cell cultures

The paper describes the production and investigation of flexible films made of high-purity polyhydroxyalkanoates (PHAs)--polyhydroxybutyrate [poly-(3HB)] and poly-3-hydroxybutyrate-co-poly-3-hydroxyvalerate [poly(3HB-co-3HV)], containing 4-30 mol % hydroxyvalerate. Poly(3HB-co-3HV) films have a more porous structure than poly-(3HB) films, which are more compact, but their surface properties, such as wettability and surface and interface energies, are the same. Sterilisation of the PHA films by conventional methods (heat treatment and gamma-irradiation) did not impair their strength. Cells cultured on PHA films exhibited high levels of cell adhesion. Cell morphology, protein synthesis and DNA synthesis were estimated by extent of 3H-thymidine incorporation into the animal cell cultures of various origins (fibroblasts, endothelium cells, and isolated hepatocytes) in direct contact with PHAs. The investigation showed that this material can be used to make matrices for in vitro proliferous cells. The investigated properties of poly-(3HB) and poly(3HB-co-3HV) films proved to be fundamentally similar.     

Microparticles prepared from biodegradable polyhydroxyalkanoates as matrix for encapsulation of cytostatic drug

Microparticles made from degradable polyhydroxyalkanoates of different chemical compositions a homopolymer of 3-hydroxybutyric acid, copolymers of 3-hydroxybutyric and 4-hydroxybutyric acids (P3HB/4HB), 3-hydroxybutyric and 3-hydroxyvaleric acids (P3HB/3HV), 3-hydroxybutyric and 3-hydroxyhexanoic acids (P3HB/3HHx) were prepared using the solvent evaporation technique, from double emulsions. The study addresses the influence of the chemical compositions on the size and ξ-potential of microparticles. P3HB microparticles loaded with doxorubicin have been prepared and investigated. Their average diameter and ξ-potential have been found to be dependent upon the level of loading (1, 5, and 10 % of the polymer mass). Investigation of the in vitro drug release behavior showed that the total drug released from the microparticle into the medium increased with mass concentration of the drug. In this study mouse fibroblast NIH 3T3 cells were cultivated on PHA microparticles, and results of using fluorescent DAPI DNA stain, and MTT assay showed that microparticles prepared from PHAs of different chemical compositions did not exhibit cytotoxicity to cells cultured on them and proved to be highly biocompatible. Cell attachment and proliferation on PHA microparticles were similar to those on polystyrene. The cytostatic drug encapsulated in P3HB/3HV microparticles has been proven to be effective against HeLa tumor cells.     

Influence of calcium and phosphorus release from bioactive glasses on viability and differentiation of dental pulp stem cells

The release of ions that can significantly contribute toward cellular response is an important characteristic of bioactive glasses (BG). Here, ionic extracts of three different compositions of BG powders in 60 mol% SiO₂, x mol% CaO (x = 28, 32 and 36), x mol% P₂O₅ (x = 12, 8 and 4) compositional system were utilized to study their effect on the viability, differentiation and mineralization of dental pulp stem cells (DPSCs) in vitro. ICP was applied to detect the exact ionic concentrations released from different composition of BG. DPSCs treated with conditioned media from the glass with 4 mol% P₂O₅ (BGCM1, media containing 44.01 ± 0.6 mg/L Si, 61.72 ± 0.1 mg/L Ca and 7.57 ± 0.01 mg/L P) were more metabolically active compared to conditioned media from the glass with 8 mol% P₂O₅ (BGCM2, media with 47.36 ± 0.7 mg/L Si, 57.4 ± 0.1 mg/L Ca and 14.54 ± 0.2 mg/L P), at all times tested, but in all cases the process was slower than the control. Cells exposed to media conditioned by the glass with 12 mol% P₂O₅ (BGCM3, 40.46 ± 0.5 mg/L Si, 61. 85 ± 0.3 mg/L Ca and 28.43 ± 0.3 mg/L P) responded differently, such that cells showed to be more metabolically active than control at day 3, but then similar to or lower than control at higher time points. Differentiation of DPSCs toward osteogenic lineage in the presence of BGCM was assessed by Alizarin red staining. Cells treated with high phosphate BGCM3 displayed a higher density of red mineralized nodules than cells treated with BGCM1 and BGCM2 after 21 days of culture in non-osteogenic medium. BGCM3 was therefore chosen for gene expression studies. Osteogenic differentiation of DPSCs in the presence and/or absence of BGCM3 or osteogenic supplements were studied by RT-PCR. Overall, the results demonstrated that, in the absence of osteogenic supplements, BGCM3 group showed a significantly higher mRNA expression levels for alkaline phosphatase at day 7, osteopontin and osteonectin at days 7 and 14, and a high level of collagen I at day 14, compared to negative control group (BM?). Overall, the results obtained from BGCM3 group are beneficial for the design and manufacture of scaffolds or particulates with tailored ion release for a range of bone repair applications.     

Effects of two low-shrinkage composites on dental stem cells (viability, cell damaged or apoptosis and mesenchymal markers expression)

To investigate the effects of new two low-shrinkage composites SDR^® and Venus^®Bulk Fill on the cell viability, cellular damage and expression of mesenchymal markers on dental stem cells. Specimens from two low-shrinkage composites were eluted with culture medium for 24 h. After 24 h of incubation, cytotoxicity of elutes were evaluated by MTT assay; apoptosis was determined using the DNA-specific fluorochrome Hoechst 33342 and the mesenchymal stem cells markers expression was analyzed by immunofluorescence staining. After 24 h of cell exposure to each extract media, dental stem cells expressed MSCs markers. The interaction among the material and cell line was not significantly correlated [F(1,60) = 2.251, P = 0.39], whereas statistically significant differences among cells lines were observed [F(1,60) = 9.157, P = 0.004], being dental pulp stem cells more resistant that periodontal ligament stem cells. Also, we did not find any significant effect between the tested materials [F(1,60) = 0.090, P = 0.765]. Furthermore, a very low proportion of exposed cells showed condensed or fragmented nuclei, typical of apoptotic cells at 24 h. The results suggest that SDR^® and Venus^® Bulk fill and should be considered when selecting an appropriate resin-based dental restorative material.     

Experimental wound dressings of degradable PHA for skin defect repair

The present study reports construction of wound dressing materials from degradable natural polymers such as hydroxy derivatives of carboxylic acids (PHAs) and 3-hydroxybutyrate/4-hydroxybutyrate [P(3HB/4HB)] as copolymer. The developed polymer films and electrospun membranes were evaluated for its wound healing properties with Grafts—elastic nonwoven membranes carrying fibroblast cells derived from adipose tissue multipotent mesenchymal stem cells. The efficacy of nonwoven membranes of P(3HB/4HB) carrying the culture of allogenic fibroblasts was assessed against model skin defects in Wistar rats. The morphological, histological and molecular studies revealed the presence of fibroblasts on dressing materials which facilitated wound healing, vascularization and regeneration. Further it was also observed that cells secreted extracellular matrix proteins which formed a layer on the surface of membranes and promoted the migration of epidermal cells from the neighboring tissues surrounding the wound. The wounds under the P(3HB/4HB) membrane carrying cells healed 1.4 times faster than the wounds under the cell-free membrane and 3.5 times faster than the wounds healing under the eschar (control).The complete wound healing process was achieved at Day 14. Thus the study highlights the importance of nonwoven membranes developed from degradable P(3HB/4HB) polymers in reducing inflammation, enhancing angiogenic properties of skin and facilitating better wound healing process.     

Preparation and characterization of biomedical highly porous Ti–Nb alloy

The compressive strength and the biocompatibility were assessed for the porous Ti–25 wt%Nb alloy fabricated by the combination of the sponge impregnation technique and sintering technique. The alloy provided pore sizes of 300–600 μm, porosity levels of 71 ± 1.5 %, in which the volume fraction of open pores was 94 ± 1.3 %. The measurements also showed that the alloy had the compressive Young’s modulus of 2.23 ± 0.5 GPa and the strength of 98.4 ± 4.5 MPa, indicating that the mechanical properties of the alloy are similar to those of human bone. The scanning electron microscopy (SEM) observations revealed that the pores were well connected to form three-dimension (3D) network open cell structure. Moreover, no obvious impurities were detected in the porous structure. The experiments also confirmed that rabbit bone mesebchymal stem cells (MSCs) could adhere and proliferate in the porous Ti–25 wt%Nb alloy. The interactions between the porous alloy and the cells are attributed to the porous structure with relatively higher surface. The suitable mechanical and biocompatible properties confirmed that this material has a promising potential in the application for tissue engineering.     

The effects of early osseointegration in different implant sites in rabbit tibias

The aim of this study was to evaluate the early osseointegration of implants with the same surface treatment in different implant sites in rabbit tibias after 4 weeks. A total of 42 acid-etched implants were implanted in three different sites in the tibia: group A was 2.08 ± 0.18 mm below epiphyseal line; group B was 7.00 ± 0.61 mm below the epiphyseal line; group C was 13.01 ± 1.26 mm below the epiphyseal line. After 4 weeks, the average bone-to-implant contact (BIC) values were as follows: group A, 40.02 ± 4.82 %; group B, 28.20 ± 5.41 %; group C, 20.76 ± 3.10 %. The BIC measurements yielded statistically significant differences among group A, group B and group C (P < 0.01); group A demonstrated the best osseointegration. In the present study, the different implantation sites in the selected 20-mm area demonstrated different early osseointegration; the sites located 7 ± 1.5 mm below the epiphyseal line were best suited for observing the effectiveness of early osseointegration among the three sites. The statistical results of the early osseointegration of implants are therefore affected by the location of the implant sites in this 20-mm area.     

聚(3-羟基丁酸酯-co-4-羟基丁酸酯)/POSS共混体系的性能

采用熔融模压法分别制备了聚(3-羟基丁酸酯-co-4-羟基丁酸酯)[P(3HB-co-4HB)]和两种多面体笼型硅氧烷(POSS)[八异丁基倍半硅氧烷(OIBS)和八氨基苯基倍半硅氧烷(OAPS)]的共混物,考察了不同含量的OIBS,OAPS对共混体系性能的影响。结果表明,两种POSS都起到成核剂的作用。OIBS,OAPS的质量分数小于1%时,可以提高体系结晶温度,力学性能;随着OIBS,OAPS质量分数的提高,成核性有所增加,但因分散性变差,体系热稳定性和力学性能变差。由于OAPS的活泼氨基可与P(3HB-co-4HB)发生化学反应,改性效果较OIBS优。     

Preparation and characterization of ibuprofen-loaded microspheres consisting of poly(3-hydroxybutyrate) and methoxy poly (ethylene glycol)-b-poly (D,L-lactide) blends or poly(3-hydroxybutyrate) and gelatin composites for controlled drug release

Poly-(3-hydroxybutyrate) (P(3HB)) is a biodegradable and biocompatible polymer that has been used to obtain polymer-based drug carriers. However, due to the high crystallinity degree of this polymer, drug release from P(3HB) microspheres frequently occurs at excessive rates. In this study, two strategies for prolonging ibuprofen release from P(3HB)-based microspheres were tested: blending with poly(D,L-lactide)-b-polyethylene glycol (mPEG-PLA); and obtaining composite particles with gelatin (GEL). SEM micrographs showed particles that were spherical and had a rough surface. A slight decrease of the crystallinity degree of P(3HB) was observed only in the DSC thermogram obtained from unloaded-microspheres prepared from 1:1 P(3HB):mPEG-PLA blend. For IBF-loaded microspheres, a reduction of around 10 °C in the melting temperature of P(3HB) was observed, indicating that the crystalline structure of the polymer was affected in the presence of the drug. DSC studies also yielded evidence of the presence of a molecular dispersion coexisting with a crystalline dispersion in the drug in the matrix. Similar results were obtained from X-ray diffractograms. In spite of 1:1 mPEG-PLA:P(3HB) blends having contributed to the reduction of the burst effect, a more controlled drug release was provided by the use of the 3:1 P(3HB):mPEGPLA blend. This result indicated that particle hydration played an important role in the drug release. On the other hand, the preparation of P(3HB):GEL composite microspheres did not allow control of the IBF release.     

The cytoprotective capacity of processed human cardiac extracellular matrix

Freshly isolated human cardiac extracellular matrix sheets (cECM) have been shown to support stem cell proliferation and tissue-specific lineage commitment. We now developed a protocol for standardized production of durable, bio-functional hcECM microparticles and corresponding hydrogel, and tested its cytoprotective effects on contractile cells subjected to ischemia-like conditions. Human ventricular myocardium was decellularized by a 3-step protocol, including Tris/EDTA, SDS and serum incubation (cECM). Following snap-freezing and lyophilization, microparticles were created and characterized by laser diffraction, dynamic image analysis (DIA), and mass spectrometry. Moreover, cECM hydrogel was produced by pepsin digestion. Baseline cell-support characteristics were determined using murine HL-1 cardiomyocytes, and the cytoprotective effects of ECM products were tested under hypoxia and glucose/serum deprivation. In cECM, glycoproteins (thrombospondin 1, fibronectin, collagens and nidogen-1) and proteoglycans (dermatopontin, lumican and mimecan) were preserved, but residual intracellular and blood-borne proteins were also detected. The median particle feret diameter was 66 μm (15–157 μm) by laser diffraction, and 57 μm (20–182 μm) by DIA with crystal violet staining. HL-1 cells displayed enhanced metabolic activity (39 ± 12 %, P < 0.05) and proliferation (16 ± 3 %, P < 0.05) when grown on cECM microparticles in normoxia. During simulated ischemia, cECM microparticles exerted distinct cytoprotective effects (MTS conversion, 240 ± 32 %; BrdU uptake, 45 ± 14 %; LDH release, ?72 ± 7 %; P < 0.01, each). When cECM microparticles were solubilized to form a hydrogel, the cytoprotective effect was initially abolished. However, modifying the preparation process (pepsin digestion at pH 2 and 25 °C, 1 mg/ml final cECM concentration) restored the cytoprotective cECM activity. Extracellular matrix from human myocardium can be processed to yield standardized durable microparticles that exert specific cytoprotective effects on cardiomyocyte-like cells. The use of processed cECM may help to optimize future clinical-grade myocardial tissue engineering approaches.     

Simultaneous expansion and harvest of hematopoietic stem cells and mesenchymal stem cells derived from umbilical cord blood

The simultaneous expansion and harvest of hematopoietic stem cells and mesenchymal stem cells derived from umbilical cord blood were carried out using bioreactors. The co-culture of umbilical cord blood (UCB)-derived hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) was performed within spinner flasks and a rotating wall vessel (RWV) bioreactor using glass-coated styrene copolymer (GCSC) microcarriers. The medium used was composed of serum-free IMDM containing a cocktail of SCF 15 ng·mL^?1, FL 5 ng·mL^?1, TPO 6 ng·mL^?1, IL-3 15 ng·mL^?1, G-CSF 1 ng·mL^?1 and GM-CSF 5 ng·mL^?1. Accessory stromal cells derived from normal allogeneic adipose tissue were encapsulated in alginate-chitosan (AC) beads and used as feeding cells. The quality of the harvested UCB-HSCs and MSCs was assessed by immunophenotype analysis, methylcellulose colony and multi-lineage differentiation assays. After 12 days of culture, the fold-expansion of total cell numbers, colony-forming units (CFU-C), CD34⁺/CD45⁺/CD105^? (HSCs) cells and CD34^?/CD45^?/CD105⁺ (MSCs) cells using the RWV bioreactor were (3.7 ± 0.3)- , (5.1 ± 1.2)- , (5.2 ± 0.4)- , and (13.9 ± 1.2)-fold respectively, significantly better than those obtained using spinner flasks. Moreover, UCB-HSCs and UCB-MSCs could be easily separated by gravity sedimentation after the co-culture period as only UCB-MSCs adhered on to the microcarriers. Simultaneously, we found that the fibroblast-like cells growing on the surface of the GCSC microcarriers could be induced and differentiated towards the osteoblastic, chondrocytic and adipocytic lineages. Phenotypically, these cells were very similarly to the MSCs derived from bone marrow positively expressing the MSCs-related markers CD13, CD44, CD73 and CD105, while negatively expressing the HSCs-related markers CD34, CD45 and HLA-DR. It was thus demonstrated that the simultaneous expansion and harvest of UCB-HSCs and UCB-MSCs is possible to be accomplished using a feasible bioreactor culture system such as the RWV bioreactor with the support of GCSC microcarriers.     

Preparation and dielectric properties of a polyurethane elastomer filled with resol-derived ordered mesoporous carbon

This study deals with the preparation and dielectric properties of polyurethane (PU) elastomer films by resol-derived ordered mesoporous carbon (OMC) nanopowder incorporation in the PU polymer matrix. Resol-derived OMC with a 2D hexagonal mesoporous carbon framework is used as conducting fillers to achieve homogeneous dispersion and favorable interfacial interactions in the polymer matrix. The dielectric properties depend on the applied field frequency and the carbon filler weight fraction. The carbon fraction has little effect on the relative permittivity. The relative permittivity of all the PU-OMC composites increases with the decline of frequency. Incorporating a small amount of OMC into the PU polymer had no influence on the dielectric loss. Along with the increasing carbon fraction above the percolation threshold, dielectric loss of PU-OMC composites increases exponentially in the low frequency range. PU-0.75 wt% OMC composite possesses the best dielectric properties, and the obtained relative permittivity and dielectric loss at 1 kHz is 9.59 and 0.03018, respectively.     

Investigation on microwave absorption capacity of nanocomposites based on metal oxides and graphene

Graphene and its nanocomposites were prepared via solution mixing process. Graphene based polymer nanocomposites were prepared by two step process. Firstly, graphene/poly(3-methyl thiophene)(PMT)/BaTiO₃ nanocomposite was prepared by in situ chemical oxidation polymerization technique. In the second step these nanocomposites were dispersed in thermoplastic polyurethane (TPU) matrix by solution blending process. All the four nanocomposites in TPU [30 % modified graphene (P1), 30 % Poly(3-methyl thiophene) (P2), 30 % graphene/PMT/BaTiO₃ (P3) and 15 % graphene/PMT/BaTiO₃ + 15 % Fe₃O₄ (P4)] were analyzed by different analytical techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Microwave absorbing property was measured by Agilent vector network analyzer (ENA E5071C) in the X-band region (8–12 GHz). Microwave absorption result was interpreted with the help of complex permittivity and permeability of the prepared materials. Matching of both dielectric loss and magnetic loss is essential for an effective radar absorbing material (RAM). P1, P2, P3 and P4 showed the maximum return loss of ?14.37, ?9.3, ?30.02 and ?47.59 dB respectively. Thermal stability of the RAMs was determined by the help of thermogravimetric analysis (TGA) instrument. Among the all, P4 showed better thermal property. All results support their use as RAM in different field.     

Soft-type polyurethane foams derived from molasses

Molasses (ML)-based soft-type polyurethane (PU) foams were successfully prepared by controlling evolved heat during chemical reaction. Two kinds of isocyanate, poly(phenylene methylene) polyisocyanate (MDI) and tolylene diisocyanate (TDI), and polypropylene glycol with a long molecular chain length were utilized to control the chemical reaction. The hydroxyl group in ML was used as the reaction site and soft-type PU foams were synthesized at isocyanate (NCO)/hydroxyl group (OH) ratios of 1.05. Mechanical properties of the above foams were controlled by changing the mixing ratio of MDI and TDI. Pore size and distribution were measured by scanning electron microscopy. With increasing thickness of cell wall, compression strength and modulus increased. Thermal properties of PU foams were investigated by differential scanning calorimetry, thermogravimetry, and thermal conductivity measurements. Two-step glass transition temperatures were observed at around ca. ?55 and 80 °C, regardless of kind of isocyanate. The low temperature side glass transition is attributed to the molecular motion of long oxyethylene chains and the high temperature side transition is caused by rigid components including saccharide components. Thermal decomposition of PU foams started from ca. 270 °C. Thermal conductivity of soft-type PU was observed in a range from 0.034 to 0.035 J s^?1 m^?1 K^?1.