Synthesis and Characterization of Novel Polyurethane Composites Based on Hybrid Inorganic/Organic Phosphazene‐Containing Microspheres

Novel polyurethane (PU) composites were prepared, based on hybrid inorganic/organic phosphazene‐containing microspheres. The FT‐IR spectra have shown that the microspheres have been linked with PU matrix. The microstructure of the composites is investigated by SEM. In comparison with PU, the glass transition temperatures and thermal stability of the composites are increased. The results from tensile testing of the composites have indicated that tensile strength is improved and elongation at break is almost invariable. The investigation on the surface properties of the composites showed that the water contact angles are obviously increased by adding 2 and 4 wt.‐% microspheres to the matrix.

     

Polyurethane Composites Reinforced with Walnut Shell Filler Treated with Perlite,Montmorillonite and Halloysite

In the following study, polyurethane (PUR) composites were modified with 2 wt.% of walnut shell filler modified with selected mineral compounds–perlite, montmorillonite, and halloysite. The impact of modified walnut shell fillers on selected properties of PUR composites, such as rheological properties (dynamic viscosity, foaming behavior), mechanical properties (compressive strength, flexural strength, impact strength), dynamic-mechanical behavior (glass transition temperature, storage modulus), insulation properties (thermal conductivity), thermal characteristic (temperature of thermal decomposition stages), and flame retardant properties (e.g., ignition time, limiting oxygen index, heat peak release) was investigated. Among all modified types of PUR composites, the greatest improvement was observed for PUR composites filled with walnut shell filler functionalized with halloysite. For example, on the addition of such modified walnut shell filler, the compressive strength was enhanced by ~13%, flexural strength by ~12%, and impact strength by ~14%. Due to the functionalization of walnut shell filler with thermally stable flame retardant compounds, such modified PUR composites were characterized by higher temperatures of thermal decomposition. Most importantly, PUR composites filled with flame retardant compounds exhibited improved flame resistance characteristics-in all cases, the value of peak heat release was reduced by ~12%, while the value of total smoke release was reduced by ~23%.     

Advanced Alumina Composites Reinforced with Titanium-Based Alloys

New (inter)metallic-ceramic composites for high-temperature structural and functional applications are prepared via high-energy ball milling. During compaction by pressureless sintering, dense Al₂O₃/Ti-based alloy composites are formed that consist of inter-connected networks of the ceramic and the (inter)metallic phases. Ti-Al-V/Al₂O₃ and Ti-Al-Nb/Al₂O₃ composites show enhanced damage tolerance over monolithic Al₂O₃, i.e ., fracture toughnesses up to 5.6 MPa·m^0.5 and bending strengths up to 527 MPa. The resistance against abrasive wear is almost doubled with respect to monolithic Al₂O₃ ceramic. Electrical resistivity scales with the ceramic volume fraction and ranges between 0.3 mΩ·cm and 55.1 mΩ·cm, with only a weak temperature dependence ≤700°C.     

竹纤维增强PP复合材料的研究

介绍了竹纤维增强聚丙烯(PP)复合材料的性能,初步探讨了竹纤维的处理、未处理以及纤维含量对增强PP的力学性能的影响因素。实验证明:与PP材料相比,添加竹纤维可使复合材料的力学性能有不同程度的改善,特别是对复合材料的冲击强度、拉伸强度及断裂伸长率影响较明显。     

碳纤维增强聚氨酯弹性体复合材料的研究

为了制备具有优良导热性能、耐热性能和力学性能的新型聚氨酯(PUR)弹性体复合材料,采用预聚体法以聚四氢呋喃醚二醇(PTMG),2,4-甲苯二异氰酸酯(TDI)和碳纤维(CF)粉末为原料,制备了不同CF含量的CF增强PUR弹性体复合材料。对其进行了导热性能、耐热性能和力学性能测试,并通过扫描电子显微镜考察了CF在PUR基体中的分散状态。红外测试结果表明,CF表面含有可以与PUR基体发生反应的—OH和—COOH。当CF质量分数为0.3%时,CF可以均匀地分散在PUR基体中,CF增强PUR弹性体复合材料的拉伸强度、撕裂强度、100%和300%定伸强度、玻璃化转变温度和热导率分别为42.24 MPa,94.03 k N/m,9.33 MPa,24.87 MPa,96.7℃和0.138 5 W/(m·K),比纯PUR弹性体分别提高了27.8%,32.2%,76.4%,102.2%,18.5℃和26.4%,而断裂伸长率为367.62%,仅下降19.5%。     

Moisture-Resistant and Mechanically Strong Polyimide-Polymethylsilsesquioxane Hybrid Aerogels with Tunable Microstructure

Moisture-resistant and mechanically strong polyimide (PI)-polymethylsilsesquioxane hybrid aerogels with doubly cross-linked structures are synthesized through sol–gel technology and supercritical CO₂ fluid drying. By using bis(trimethoxysilylpropyl) amine as a cross-linker, the end-capped polyamide acid derived from biphenyl-3,3′,4,4′-tetracarboxylic dianhydride and 4,4′-oxydianiline is cross-linked with a silica network using methyltrimethoxysilane as the silica source precursor. The resultant hybrid aerogels show low density (0.12–0.15 g cm⁻³), low thermal conductivity (0.032–0.049 W m⁻¹ K⁻¹), high hydrophobicity (125–140°) and good thermal stability (above 435 °C) with tunable microstructure. With the increase of silica sol volume, the microstructure of hybrid aerogels transforms from fibrous network to hierarchical microstructure. Aerogels with high content of silica sol exhibit good moisture resistance, high Young's modulus (Max. 19.6 MPa), and high specific modulus (Max. 131 kN m kg⁻¹), which are attributed to their unique hierarchical microstructure with a sheet skeleton. These hybrid aerogels are promising in the fields of thermal insulation, aerospace applications and so on.     

Biobased Polyurethane Composite Foams Reinforced with Plum Stones and Silanized Plum Stones

In the following study, ground plum stones and silanized ground plum stones were used as natural fillers for novel polyurethane (PUR) composite foams. The impact of 1, 2, and 5 wt.% of fillers on the cellular structure, foaming parameters, and mechanical, thermomechanical, and thermal properties of produced foams were assessed. The results showed that the silanization process leads to acquiring fillers with a smoother surface compared to unmodified filler. The results also showed that the morphology of the obtained materials is affected by the type and content of filler. Moreover, the modified PUR foams showed improved properties. For example, compared with the reference foam (PUR_REF), the foam with the addition of 1 wt.% of unmodified plum filler showed better mechanical properties, such as higher compressive strength (~8% improvement) and better flexural strength (~6% improvement). The addition of silanized plum filler improved the thermal stability and hydrophobic character of PUR foams. This work shows the relationship between the mechanical, thermal, and application properties of the obtained PUR composites depending on the modification of the filler used during synthesis.     

Fiber Reinforced Polyimide Aerogel Composites with High Mechanical Strength for High Temperature Insulation

Glass fiber/polyimide aerogel composites are prepared by adding glass fiber mat to a polyimide sol derived from diamine, 4,4′‐oxydianiline, p‐phenylene diamine, and dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. The fiber felt acts as a skeleton for support and shaping, reduces aerogel shrinkage during the preparation process, and improves the mechanical strength and thermal stability of the composite materials. These composites possess a mesoporous structure with densities as low as 0.143–0.177 g cm^?3, with the glass fiber functioning to improve the overall mechanical properties of the polyimide aerogel, which results in its Young's modulus increasing from 42.7 to 113.5 MPa. These composites are found to retain their structure after heating at 500 °C, in contrast to pure aerogels which decompose into shrunken ball‐like structures. These composites maintain their thermal stability in air and N₂ atmospheres, exhibiting a low thermal conductivity range of 0.023 to 0.029 W m^?1 K^?1 at room temperature and 0.057to 0.082 W m^?1 K^?1 at 500 °C. The high mechanical strengths, excellent thermal stabilities, and low thermal conductivities of these aerogel composites should ensure that they are potentially useful materials for insulation applications at high temperature.     

Simultaneously Improved Thermal Conductivity and Dielectric Properties of NBR Composites by Constructing 3D Hybrid Filler Networks

This work aims to address the heat accumulation issue in electronic components during high-frequency operation through the preparation of novel thermally conductive composites. First, polydopamine (PDA) and in-situ growth of silver (Ag) nanoparticles are applied for the surface modification of graphene oxide (GO) and carbon nanotube (CNT) to prepare pGO@Ag and pCNT@Ag hybrid filler, respectively. Then, nitrile butadiene rubber (NBR) is chosen as the polymeric matrix and simultaneously incorporated with both pGO@Ag and pCNT@Ag to prepare polymeric composites with excellent thermal conductivity (TC) and dielectric constant (ɛ_r). Due to the construction of 3D heat conduction networks by utilizing 2D pGO@Ag and 1D pCNT@Ag, the fabricated NBR composites achieved the maximum TC of 1.0112 W/(mK), which is 636% higher than that of neat NBR (0.1373 W (mK)⁻¹). At the filler loading of 9 vol%, the TC of pGO@Ag/pCNT@Ag/NBR composite is 152% that of GO/CNT/NBR composite (0.6660 W (mK)⁻¹). Moreover, due to electron polarization effect of GO and CNT and micro-capacitor effect of Ag nanoparticles, a large ɛ_r of 147.12 is attained at 10 Hz for NBR composites. Overall, the development of dielectric polymer materials with high TC is beneficial for enhancing the service life and safety stability of the electronic components.     

Polyurethane foams with 1,3‐pyrimidine ring

Attempts of obtaining of polyurethane foams using polyetherols with 1,3‐pyrimidine ring (obtained in reactions of 6‐aminouracil with oxiranes) are reported. Properties of the foams are investigated, especially their thermal stability. The foams show an improved thermal stability up to 200°C for a long time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on Preparation and Properties of HVBR Reinforced with Si69-modified Carbon Nanotubes

Si69-modified CNTs/HVBR nanocomposites were prepared in dependence of different loadings of Si69-modified CNTs fabricated by mixing acid-treated CNTs with Si69 in toluene. FT-IR analysis illustrated the successful modification of CNTs. Experimental results showed that the Si69-modified CNTs could more significantly enhance the mechanical strength and thermal conductivity of the composites than the unmodified CNTs, indicating the Si69-modified CNTs could be more uniformly dispersed in the HVBR matrix, which was also verified form the SEM results. The DMA results indicated that the incorporation of Si69-modified CNTs could remarkably increase the glass transition temperature and decrease the height of the tanδ peak.     

Thermal,Thermomechanical, and Morphological Properties of Spartium junceum Fiber Reinforced Polypropylene Composites

The composites investigated in this article were polypropylene reinforced with Spanish broom (Spartium junceum) fibers. These fibers were modified with N[-3 Trimethoxysilyl propyl] ethylene diamine (Z6020) or stearic acid, which work as coupling agents between fibers and matrix. This work studied the thermal (differential scanning calorimetry) and thermomechanical (dynamic mechanical thermal) analysis. The surfaces of the composites were characterized by electron microscopy. It was found that silane-treated fiber composites show superior properties compared with the specimens made of pure polypropylene. Microscopic observations correlate with these results.     

Enhanced Thermal Conductivity of Epoxy Composites with MWCNTs/AlN Hybrid Filler

To further improve the thermal conductivity of epoxy resin, the multi-walled carbon nanotube/aluminum nitride (MWCNTs/AlN) hybrid filler was employed to prepare thermal conductivity MWCNTs/AlN/epoxy composite by casting process, and the silane coupling reagent of γ-glycidoxy propyl trimethoxy silane(KH-560) was also used to functionalize the surface of MWCNTs and/or AlN. Results revealed that, the thermal conductivity of epoxy resin was improved remarkably with the addition of MWCNTs/AlN hybrid filler, a higher thermal conductivity of 1.04 W/mK could be achieved with 29 wt% MWCNTs/AlN hybrid filler (4 wt% MWCNTs +25 wt% AlN), about 5 times higher than that of native epoxy resin. And the epoxy composite with 29 wt% MWCNTs/AlN hybrid filler possessed better thermal conductivity and mechanical properties than those of single 5 wt% MWCNTs or 40 wt% AlN. The thermal decomposition temperature of MWCNTs/AlN/epoxy composite was increased with the addition of MWCNTs/AlN hybrid filler. For given filler loading, surface treatment of MWCNTs and/or AlN by KH-560 exhibited a positive effect on the thermal conductivity of epoxy composite.     

Antioxidative activity of sage (Salvia officinalis L.), savory (Satureja hortensis L.) and borage (Borago officinalis L.) extracts in rapeseed oil

The antioxidant activity (AA) of acetone oleoresins (AcO) and deodorised acetone extracts (DAE) of sage (Salvia officinalis L.), savory (Satureja hortensis L.) and borage (Borago officinalis L.) were tested in refined, bleached and deodorised rapeseed oil applying the Schaal Oven Test and weight gain methods at 80 °C and the Rancimat method at 120 °C. The additives (0.1 wt‐%) of plant extracts stabilised rapeseed oil efficiently against its autoxidation; their effect was higher than that of the synthetic antioxidant butylated hydroxytoluene (0.02%). AcO and DAE obtained from the same herbal material extracted a different AA. The activity of sage and borage DAE was lower than that of AcO obtained from the same herb, whereas the AA of savory DAE was higher than that of savory AcO. The effect of the extracts on the oil oxidation rate measured by the Rancimat method was less significant. In that case higher concentrations (0.5 wt‐%) of sage and savory AcO were needed to achieve a more distinct oil stabilisation.     

Ultrasonic-Assisted Method for the Preparation of Carbon Nanotube-Graphene/Polydimethylsiloxane Composites with Integrated Thermal Conductivity,Electromagnetic Interference Shielding,and Mechanical Performances

Due to the rapid development of the miniaturization and portability of electronic devices, the demand for polymer composites with high thermal conductivity and mechanical flexibility has significantly increased. A carbon nanotube (CNT)-graphene (Gr)/polydimethylsiloxane (PDMS) composite with excellent thermal conductivity and mechanical flexibility is prepared by ultrasonic-assisted forced infiltration (UAFI). When the mass ratio of CNT and Gr reaches 3:1, the thermal conductivity of the CNT-Gr(3:1)/PDMS composite is 4.641 W/(m·K), which is 1619% higher than that of a pure PDMS matrix. In addition, the CNT-Gr(3:1)/PDMS composite also has excellent mechanical properties. The tensile strength and elongation at break of CNT-Gr(3:1)/PDMS composites are 3.29 MPa and 29.40%, respectively. The CNT-Gr/PDMS composite also shows good performance in terms of electromagnetic shielding and thermal stability. The PDMS composites have great potential in the thermal management of electronic devices.     

A Study on Polyurethane Hybrid Nanocomposite Foams Reinforced with Multiwalled Carbon Nanotubes and Silica Nanoparticles

Multifunctional polyurethane foams reinforced with multiwalled carbon nanotubes and silica nanoparticles enhanced specific properties. We studied the effects of nanoparticle addition into polyurethane on mechanical properties and thermal stability by means of tensile, Charpy impact, hardness tests, and thermogravimetric analysis. Nanoparticles added to polyurethane are multiwalled carbon nanotubes, two types of silica nanoparticles, and multiwalled carbon nanotube/spherical silica as hybrid filler. Hybrid polyurethane/spherical silica/multiwalled carbon nanotube nanocomposite with the constant overall content of 0.75?wt% showed higher tensile strength, hardness, and thermal stability than either of nanoparticles at this content, which approves a synergistic effect between multiwalled carbon nanotubes and silica nanoparticles.     

聚氨酯填充型泡沫混凝土复合材料的性能研究

将不同掺量聚氨酯（PU）加入泡沫混凝土（FC）,研究聚氨酯填充型泡沫混凝土（FC/PU）复合材料的性能。结果表明：随着PU掺量的增加,FC/PU复合材料的导热系数不断降低,阻燃性能变差。PU掺量为0～4%时,随着PU掺量的增加,FC/PU复合材料的浆体黏度逐渐降低,气孔特性变好,抗压强度不断增大。PU掺量超过4%时,FC/PU复合材料黏度开始增大,气孔特性变差,抗压强度逐渐降低。PU掺量为4%时,FC/PU复合材料的综合性能最优,与未掺入PU相比,黏度降低62.7%,气孔特性较好,抗压强度提高75.0%,导热系数降低18.7%,阻燃性能仍能达到A1级。     

Hierarchical Carbon Nanotube@SiO2-TiO2 Reinforced Polyurethane Composites: Thermal,Mechanical and Abrasion Resistance Properties

In this study, novel polyurethane-based composites reinforced by hierarchical CNTs@SiO₂-TiO₂ were fabricated via in situ polymerization. Significant improvement of the composites in thermal stability was achieved by incorporating functionalized CNTs up to 2.0 wt%. Meanwhile, the tensile strength, strain-at-break, and Young’s modulus were greatly improved by increasing nanotube loading. The Abrasion losses could be significantly decreased to 30 mm³/1.61 km due to the addition of functionalized CNTs. Therefore, the introduction of nanosized hierarchical SiO₂-TiO₂ coated CNTs has a stimulative effect on the simultaneous mechanical reinforcement and abrasion resistance modification for polyurethane.