Microstructural and mechanical properties of Al2O3 and ZTA foams prepared by thermo-foaming technique

Alumina and zirconia toughened alumina foams were fabricated through a thermo-foaming method using varying amounts of powder to sucrose weight ratio. All the fabricated foams were characterized for their compressive strength, bending strength, and fracture toughness under static loading conditions. The compressive strength increases with an increase in a weight ratio from 0.4 to 1.2. The maximum compressive strength values were found to be 1.9 MPa, and 1.8 MPa for alumina and zirconia toughened alumina foams, respectively. Further increase in powder to sucrose weight ratio led to a decrease in the compressive strength due to the partial collapse of the cell walls during the foaming process. The 3-point bend test results revealed an improvement of bending strength and fracture toughness values of zirconia toughened alumina foams compared to alumina foam, which can be attributed to the transformation toughening mechanism.     

改性条件对阻燃型硬质聚氨酯泡沫塑料性能的影响

选择阻燃剂三聚氰胺和甲基磷酸二甲酯（DMMP）对硬质聚氨酯泡沫塑料进行阻燃改性,研究了异氰酸酯指数、水、三聚氰胺以及DMMP添加量对硬质聚氨酯泡沫塑料阻燃性能和拉伸强度的影响主次顺序。结果表明,添加三聚氰胺和DMMP可以提高硬质聚氨酯泡沫塑料的阻燃性能,当三聚氰胺的添加量为25份、DMMP的添加量为25份、异氰酸酯指数为1.15、水添加量为1.5份时,硬质聚氨酯泡沫塑料的综合性能最佳。     

Thermogravimetric and qualitative analysis of thermal decomposition characteristics of polyurethane foams based on polyols with carbamide or oxamide and borate groups

The thermal stability and the kinds of products of thermal decomposition of polyurethane foams modified with urea or oxamide and borate groups were studied. Incorporation of urea or oxamide groups and borate groups enhances the thermal stability of polyurethane foams compared to polyurethane foams based on typical polyols. Thermal stability of foams modified with oxamide groups is somewhat higher that of foams modified with urea groups. In turn, simultaneous incorporation of borate groups results in an increase in thermal stability of the foams modified with urea. The temperature of thermal decomposition of the foams with oxamide and borate groups does not change or undergoes a slight decrease. The thermal degradation products of investigated foams are similar and they are usually water, ammonia, carbon dioxide and/or nitrous oxide. Additionally, hydrogen cyanide can be released during thermal decomposition of polyurethane foams modified with urea groups. The presence of borate groups prevents the formation of hydrogen cyanide. The opposite situation is observed in the case of the foams modified with oxamide and borate groups. Thus, from the point of view of a fire hazard, the use of the foams modified with urea and borate groups is safer. © 2017 Society of Chemical Industry     

Phenolic foams toughened with crosslinked poly (n‐butyl acrylate)/silica core‐shell nanocomposite particles

A new type of crosslinked poly (n‐butyl acrylate) (PBA)/silica core‐shell nanocomposite particles was adopted as toughening agent to improve the mechanical properties of phenolic foams. The effects of the nanocomposite particles on the structures and properties of lightweight phenolic foams were investigated. SEM result showed that the addition of a small quantity of the nanocomposite particles can significantly enhance the structural homogeneity of phenolic foams. Thermalgravimetric analysis result suggested that the incorporation of the nanocomposite particles did not affect the thermal stability of the toughened phenolic foams. The flexural strength, compressive strength, and elastic modulus of the phenolic foams increased distinctively after the addition of the nanocomposite particles, the maximum values of which increased by 36.0%, 42.9%, and 32.3%, respectively. In this study, the optimum dosage of the nanocomposite particles is 0.03 phr in the modified phenolic foams. Moreover, the influence on the flammability of phenolic foams by toughening can almost be neglected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42590.     

硼-磷-氮协效膨胀型阻燃剂的合成与性能研究

以三聚氰胺(MEL)、磷酸(PA)、硼酸(BA)等为原料,合成了三聚氰胺磷酸盐(MP)和三聚氰胺硼酸盐(MB)中间体,以及三聚氰胺磷酸硼酸盐(MPB)硼-磷-氮协效"三位一体"膨胀型阻燃剂,用红外光谱和元素分析等方法对合成产物的结构和组成进行了表征,确定了阻燃剂合成的最佳条件。探讨了MPB的元素组成对MPB阻燃环氧树脂复合材料氧指数的影响,以及MPB的协同阻燃机理。结果表明:合成MP时,三聚氰胺和磷酸的最佳摩尔比为1:0.5;合成MB时,三聚氰胺和硼酸的最佳摩尔比为10:1;合成MPB-1(以MP为中间体)的最佳质量比为w(MP):w(BA)=3:1;合成MPB-2(以MB为中间体)的最佳质量比为w(MB):w(PA)=0.92:1。MPB-2对环氧树脂的阻燃性能优于MPB-1,这是由于MPB-2中元素组成均衡,使得B-P-N协效作用明显。     

Melamine amino trimethylene phosphate as a novel flame retardant for rigid polyurethane foams with improved flame retardant,mechanical and thermal properties

Melamine amino trimethylene phosphate (MATMP) as a novel nitrogen‐phosphorus flame retardant, was synthesized by the reaction of melamine with amino trimethylene phosphonic acid (ATMP) in aqueous solution. The structure of MATMP was characterized by Fourier transform infrared spectroscopy, solid state 31 P nuclear magnetic resonance, and thermogravimetric analysis. Rigid polyurethane (RPU) foams were prepared by one‐shot and free‐rise method, using MATMP as a flame retardant. The flame retardant, mechanical and thermal properties of MATMP in RPU foams were studied. It is found that the RPU foam containing 15 wt % MATMP (sample RPUMA‐15) can pass the UL‐94 V0 test with a limiting oxygen index of 25.5%. The cone calorimeter test results show that the peak heat release rate of RPUMA‐15 is reduced about 34% compared with that of untreated RPU foam. SEM results indicate that the RPU foams with MATMP can form the good and compact char during burning which provides better flame retardancy. The compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content comparing with that of untreated RPU foam. Moreover, thermal conductivities of the MATMP filled RPU foams are about 0.03 W/m K. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45234.     

Application of products of reaction between melamine and glycidol as substrates for oligoetherols and polyurethane foams containing 1,3,5‐triazine rings

Hydroxyalkyl derivatives of melamine were obtained by addition of melamine to glycidol. These derivatives were then used to obtain multifunctional oligoetherols by reaction with oxiranes and alkylene carbonates. The structure and properties of the oligoetherols were studied in detail. The oligoetherols were then used to obtain polyurethane foams of enhanced thermal stability. The foams showed marked thermal resistance at 200 °C. The beneficial feature of the obtained foams was their increased compression strength after thermal exposure. © 2013 Society of Chemical Industry     

Bi-phase flame-retardant effect of hexa-phenoxy-cyclotriphosphazene on rigid polyurethane foams containing expandable graphite

The flame-retardant rigid polyurethane (PU) foams with hexa-phenoxy-cyclotriphosphazene/expandable graphite (HPCP/EG) were prepared through box-foaming in our laboratory. The flame retardancy of PU foams was characterized using the limiting oxygen index and cone calorimeter. The results show that the incorporation of HPCP into the PU foams containing EG enhanced flame retardancy. The main degradation process of HPCP in PU foams was investigated by pyrolysis gas chromatography/mass spectroscopy. HPCP during combustion generated phenoxyl and PO₂ free radicals, which could quench the flammable free radicals produced by the matrix and hamper the free radical chain reaction of combustion. This observation shows that HPCP produced a gas-phase flame-retardant effect in this specimen. Additionally, micro-morphology, elemental composition and content of residual char of the flame-retardant PU foams after the cone calorimeter test were also characterized using scanning electron microscope and energy dispersive X-ray microanalyser. The results exhibit that the partial phosphorus from HPCP remained in the residual char, and HPCP significantly enhanced the strength and compatibility of the char layer formed by the PU foams containing EG. These results indicate the important function of HPCP in condensed phase. Thus, HPCP exhibited gas-phase and condensed-phase flame-retardant effects on the PU/EG foams.     

Effect of ZnO content change on the structure and properties of zinc borophosphate glasses

The glass system xZnO-10B₂O₃-(100 ? x)P₂O₅ was prepared by cooling using the melt-quenching technique in the composition series x from 30 to 60 mol %. The density, thermal expansion coefficient, glass transition temperature, and softening temperature of the glass system were determined. Structural characterization was performed by using a combination of IR and Raman spectroscopy and ¹¹B/³¹P solid state NMR spectroscopy data. In particular, variations in the phosphate network structure upon the addition of ZnO were investigated. Data analysis indicated that increasing the ZnO content and decreasing the P₂O₅ content increased the extent of cross-linking between the phosphate and borate units in the glass network; this was because incorporation of ZnO polyhedra into the structural network of ZnO increased the network dimensionality. These structural changes were confirmed by Raman and IR spectroscopy.     

Flame retardancy of ceramic-based rigid polyurethane foam composites

In this work, ceramic fillers zirconia and alumina powder were incorporated in the rigid polyurethane foams derived from modified castor oil and their impact on the mechanical, thermal, and fire performances of composite foams have been analyzed. It was observed that the addition of ceramic filler showed improved mechanical and thermal properties and best properties were shown by 6% zirconia with compressive strength of 6.61 MPa and flexural strength of 5.72 MPa. Zirconia also demonstrated an increase in T_5% up to 260 °C. Cone calorimetry shows a decrease in peak of heat release from 118 to 84 kW m⁻² and 94 kW m⁻² by the incorporation of alumina and zirconia powder, respectively. Furthermore, total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decrease remarkably on the incorporation of ceramic fillers. So, these fillers have a great potential as an additive to incorporate good mechanical, thermal, and fire properties in bio-based rigid PU foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48250.     

Effect of high temperature on the mechanical properties of hierarchical porous cenosphere/geopolymer composite foams

A hierarchical porous cenosphere/geopolymer composite foam (FHCs/KGP) was fabricated by the simultaneous incorporation of O₂ pore from hydrogen peroxide and cenosphere filler addition. Effects of both H₂O₂ content and high-temperature treatment on the microstructure, porosity and strength of porous FHCs/KGP foams were investigated systematically. The obtained FHCs/KGP foams showed typical amorphous structure and desirable porosity from 65 to 82%. The composites could crystallize in situ to FHCs/leucite foams above 1000℃. Compression strength of the FHCs/leucite foams showed a maximum value of 5 ± 0.3 MPa when treated at 1000°C. The improvement of mechanical properties for the composite foams was attributed to crack deflection, fractured microspheres and the good bond between the FHCs and matrix. This study could open opportunities to employ cellular foams as alternatives in structure and filtration applications.     

Thermal and fire behavior of isophorone diisocyanate based polyurethane foams containing conventional flame retardants

This work reports on the fire behavior of isophorone diisocyanate‐based polyurethane foams containing different conventional flame retardants (FRs) such as melamine, ammonium polyphosphate, aluminum hydroxide, expandable graphite, and their combinations. The foams were obtained in a laboratory scale and characterized in terms of their morphology, density, thermal stability, and fire behavior. According to atomic force microscopy, the incorporation of FRs decreased the phase separated domain size. The cellular structure of the foams was examined qualitatively by scanning electron microscopy while the quantitative analysis of the surrounding skin was performed by optical microscopy and Image J. The FR containing foams showed more and smaller cells. The thermogravimetric analysis showed that the FRs had no influence in the initial degradation temperature of the foams. However, the obtained residue values were higher than the theoretical ones, indicating that there was some type of interaction between the FRs and the foams. The fire behavior of polyurethane foams was studied by the cone calorimeter and the data showed that the introduction of expandable graphite and combinations of ammonium polyphosphate/melamine to the reference foam gave rise to a significant reduction in the total heat release. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45944.     

Physicomechanical,friction, and abrasion properties of EVA/PU blend foams foamed by supercritical nitrogen

Elastomer foams based on EVA, PU, and EVA/PU blends formulated for shoe‐sole applications were prepared by a supercritical N₂ batch foaming process and characterized for physicomechanical, friction and abrasion properties. The blending of EVA with PU was aimed for improving the friction and wear characteristics of the EVA based foams. All of the foams prepared showed spherical cells with closed‐cell morphology and the cell sizes varied with varying the EVA/PU blend ratio and CaCO₃ content of the foams. The properties such as hardness and resilience, friction coefficients and abrasion resistance improved for the EVA/PU blend foams compared to the EVA foam, but their compression set, tensile strength, and tear strength were inferior to the EVA foam. The incorporation of CaCO₃ filler increased density, hardness, tensile strength, and tear strength of the EVA/PU blend foams but decreased resilience, compression set, friction coefficients, and abrasion resistance. The improvement in friction coefficients and wear resistance obtained in the EVA/PU blend foams was significant for shoe‐sole applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Preparation of biphasic hydroxyapatite/ β-tricalcium phosphate foam using the replication technique

Biphasic hydroxyapatite/β-tricalcium phosphate foams were prepared using the replication technique starting from a precipitated hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: HAP) powder, and sodium glycerophosphate (GP). The effect of the grinding time, solid loading, dispersant amount, and etching, replication, and sintering processes were investigated. The SEM, OEM and FTIR analyses proved that the surface of the polyurethane template must be treated with NaOH solution to make it more hydrophilic prior to the coating process. With a solid loading of 40 wt-%, the slurries prepared from the precipitated hydroxyapatite presented a shear thinning behavior, which was useful for the coating process. The SEM analysis of the foams showed that the optimum number of coating layers to obtain foam with an identical structure with the template was limited to three. The use of GP and the optimized preparation parameters helped to decrease the consolidation temperature of the ceramic foams to 1000 °C. The XRD and FTIR analyses of the prepared foams showed that the thermal treatment of the GP and the HAP mixture led to a partial decomposition of the HAP to tricalcium phosphate. The fitting of the XRD patterns and the obtained lattice parameters proved that the decomposition was accompanied by the insertion of sodium from GP toward the lattice of tricalcium phosphate and the formation of Na-β-tricalcium. The results of the SEM analysis, the pore size distribution and the mechanical strength showed that the presence of the Na-β-tricalcium reduced the pore size distribution from 500-2700 to 100–1700 μm, decreased slightly the total porosity from 80 vol-% to 70 vol-%; and improved the mechanical strength of the obtained foam from 1.56 MPa to 2.60 MPa.     

POE/EPDM热塑性弹性体的阻燃改性研究

采用动态硫化的方法制备了聚烯烃类共聚物/三元乙丙橡胶(POE/EPDM)热塑性弹性体,并进行了阻燃改性的探索.讨论了各种无卤阻燃体系,如膨胀剂PNP、三聚氰胺、硅酸铝、磷酸二氢铵、滑石粉、磷酸酯、硼酸锌等新型的阻燃剂以及与其他阻燃剂并用对体系的影响.结果表明,新型阻燃剂对热塑性弹性体的阻燃效果较好,但由于加入量大,使其力学性能下降较快.又通过TG热失重分析从理论上对个别阻燃体系进行了阻燃机理的研究.进一步用表面活化剂SB-182对体系进行改性.结果表明,活化剂SB-182可以使制品硬度适中,强度合乎要求,制得了具有良好力学性能和阻燃性能的制品.     

淀粉磷酸酯蜜胺盐的合成

以淀粉、焦磷酸钠、蜜胺为原料,首先合成淀粉磷酸酯,进一步合成淀粉磷酸酯蜜胺盐,用红外光谱进行结构表征,并且测定其氧指数。结果表明,淀粉磷酸酯的最佳合成反应条件为:温度125℃,pH为5,反应时间为2.5 h;合成淀粉磷酸酯蜜胺盐的最佳反应条件为:温度120℃,pH为6,淀粉磷酸酯和蜜胺的比例为1∶1,反应时间为5 h。红外图谱表明,该阻燃剂具有环状结构;将该阻燃剂掺入聚乙烯中进行氧指数测试,表明该阻燃剂具有一定的阻燃效果。     

Preparation of flexible,self‐extinguishing silicone foams

Flexible, self‐extinguishing silicone foams (SFs) with a relatively low density (0.25–0.45 g/cm³) were obtained from a mixture of α,ω‐(dihydroxy)polydimethylsiloxanes, water, flame retardants (melamine and/or expanded graphite), and polyisocyanates [poly(diphenylmethane isocyanate)]. These compositions were crosslinked at room temperature with branched polymethylhydrosiloxanes with the structure (MeSiO_1.5)₃ (MeHSiO)₁₀₂(Me₃SiO_0.5)₅ in the presence of tin octoate as a catalyst. The SFs were modified by the addition of linear or graft carbofunctional polysiloxanes containing γ‐hydroxypropyl groups. Only the SFs prepared by means of a dehydrocondensation reaction had a good homogeneity of pores, whereas the foams formed with two kinds of blowing agents (hydrogen and carbon dioxide, generated in the reaction of water with isocyanate groups) had lower densities but a poor homogeneity of pores. Unmodified SFs showed a tensile strength of 20 kPa or less, whereas the foams formed with the addition of poly(diphenylmethane isocyanate) and water had a tensile strength of 23–25 kPa. The SFs with 15 and 30% contents of melamine or expanded graphite had tensile strengths in the ranges 38–45 and 51–54 kPa, respectively. All of the prepared SFs were combustible materials. The SFs without the addition of flame retardants had a limiting oxygen index of approximately 21%, whereas the SFs with a 30% content of fire retardant had self‐extinguishing properties and a limited oxygen index of 41–43%. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Modifications of the rigid polyurethane–polyisocyanurate foams

The method of boroorganic compounds preparation by esterification of boric acid and glycols has been presented. The obtained compounds tri(2‐hydroxybutyl)borate, tri(hydroxythiodiethylene)borate, tri[(3‐chloro‐2‐hydroxy‐1‐propoxy)‐1‐methylpropyl]borate, and tri[3‐chloro‐2‐hydroxy‐1‐propoxy)thiodiethyl]borate were used to produce the rigid polyurethane–polyisocyanurate (PUR‐PIR) foams. The foams were prepared by one‐stage method and the amount of borates added varied, within the range from 0.0 to 0.4 of chemical equivalent. The method of preparation, determination of foaming parameters, and methods of testing of the physicochemical properties of PUR‐PIR foams as well as their results have been presented. A special emphasis was put on reduction of the foam flammability. It was found that application of the obtained compounds as polyolic components has a favorable effect on the properties of the produced rigid PUR‐PIR foams. The obtained rigid PUR‐PIR foams were characterized by a higher compressive strength, lower brittleness, considerably reduced flammability, and higher content of the closed cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2020–2029, 2006     

磷酸三聚氰胺硼酸盐阻燃剂的合成

采用水为溶剂经过二步反应合成了含硼膨胀型阻燃剂磷酸三聚氰胺硼酸盐（melamine phosphate borate,MPB）。通过IR、EDAX确定了其结构。首先磷酸和三聚氰胺反应得到磷酸三聚氰胺（MP）,然后MP再与硼酸反应,得到MPB。研究了物料配比、反应温度、溶剂用馒、反应时间等因索对MPB收率的影响以及MPB的阻燃性能。认为MPB最佳的合成条件为：n（H3803）：n（MP）=1．5：1,溶剂用量为45mL（MP为0．073m01）．在80％下反应3h,MPB的收率为82．97％。在MPB最佳添加量20％时,环氧树脂的极限氧指数达到25％,并有膨胀效应。     

Direct pyrolysis mass spectrometry analyses of polyamide‐6 containing melamine and boron compounds

In this work, the thermal degradation characteristics of polyamide 6 (PA6) containing melamine (Me) and a boron‐containing additive, borophosphate (BPO₄), zinc borate (ZnB) or a boron and silicon‐containing oligomer (BSi) are investigated systematically via direct pyrolysis mass spectrometry. In the presence of boron compounds, not only the release of melamine and its degradation products but also thermal characteristics of PA6 are affected significantly and the interactions between melamine and PA6 are enhanced. For the composite involving BPO₄, sublimation of melamine and degradation of PA6 are slightly shifted to high temperatures. Whereas, for the composites involving ZnB and BSi, sublimation of melamine is depressed due to the glassy surface formed by ZnB and BSi and release of thermal degradation products of PA6 are shifted to lower temperatures noticeably. The glassy surface generated by ZnB allows the release of degradation products of melamine to a certain extent. Conversely, for the composite involving BSi, reduction in the yields of degradation products of melamine is also noted. The trap of degradation products of melamine in the polymer matrix causes significant decrease in the the temperature region where thermal degradation products of PA6 are recorded. POLYM. COMPOS. 34:1389–1395, 2013. © 2013 Society of Plastics Engineers