A novel phase-change composites based on silicone rubber containing energy-storage microcapsules

A novel phase-change composites based on silicone rubber (MVQ) containing n-octadecane/poly (styrene-methyl methacrylate) microcapsules were successfully obtained by mixing energy-storage microcapsules into MVQ matrix using three preparation methods. The effect of microcapsules content on thermal property of the composites was investigated by thermogravimetric analysis. The mechanical properties of the composites prepared by three methods were also investigated. The morphology and thermal properties of the composites were characterized by scanning electron microscopy (SEM), differential scanning calorimetry, and thermal response. Thermal and mechanical properties of the composites were excellent when the microcapsules were added into room temperature vulcanized silicone rubber with 2 phr (per hundred rubber) content and cured at room temperature. The composites were proved to have good energy-storage performance with 67.6 J g^?1 enthalpy value.     

Synthesis of functionalized α-zirconium phosphate modified with intumescent flame retardant and its application in poly(lactic acid)

A novel functionalized α-zirconium phosphate (F-ZrP) modified with intumescent flame retardant was synthesized by co-precipitation method and characterized. Poly (lactic acid) (PLA)/F-ZrP nanocomposites were prepared by melt blending method. The thermal stability and combustion behavior of PLA/F-ZrP nanocomposites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), scanning electronic microscopy (SEM), and cone calorimeter test (CCT). The results showed that the addition of flame retardant F-ZrP slightly affect PLA's thermal stability, but significantly improve the flame retardancy of PLA composites. In comparison with neat PLA, the LOI value of PLA/F-ZrP was increased from 19.0 to 26.5, and the UL-94 rating was enhanced to V-0 as the loading of F-ZrP at 10%. SEM results suggested the introduction of F-ZrP in the PLA system can form compact intumescent char layer during burning. All these results showed that the F-ZrP performed good flame retardancy for PLA.     

Influence of chemical shell structure on the thermal properties of microcapsules containing a flame retardant agent

Microcapsules containing ammonium phosphate as the acid source for an intumescent system were prepared by various processes. The microcapsules have different morphologies, load content and various types of polymeric shell. The polymers for our microcapsule shell are polymers considered as carbon source for intumescent formulations. In this paper we discuss the influence of polymeric shell and phosphate content of the microcapsules on the capacity to produce a thermally stable residue at high temperature, one of the characteristics for an intumescent formulation.     

Microencapsulation of decabromodiphenyl ether by in situ polymerization: Preparation and characterization

Melamine-formaldehyde (MF) resin microcapsules containing decabromodiphenyl ether (DBDPO) with better thermal stability were successfully prepared by in situ polymerization, DBDPO being the core material and MF resins being the wall materials. Chemical structure of the prepared microcapsules was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Morphologies and thermal properties were also investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively. The results indicated that MF microcapsules with DBDPO particles prepared in this study showed better thermal stability, and could be used as effective flame retardant even for the resins which should be processed at temperatures higher than 350 °C.     

Polypropylene fabrics padded with microencapsulated ammonium phosphate: Effect of the shell structure on the thermal stability and fire performance

Three types of microcapsules of di-ammonium hydrogen phosphate (DAHP) with different polymeric shells were evaluated as flame retardants in commercial polyurea padding for textiles. Encapsulated FR agent has the advantage of being compatible with the polymer matrix. The thermal degradation for the three types of DAHP microcapsules shows that our microcapsules act as intumescent fire retardants. The reaction to fire of polypropylene fabrics padded with FR polyurea loaded with neat DAHP or microencapsulated DAHP was studied with the cone calorimeter as a fire model.     

Development and characterisation of flame-retardant fibres from isotactic polypropylene melt-compounded with melamine-formaldehyde microcapsules

Intumescent flame-retardant textiles have been developed from flame-retardant microcapsules. The work is based on the synthesis of different melamine-formaldehyde microcapsules containing di-ammonium hydrogen phosphate and/or poly(1,6-hexamethylene adipate) by in-situ polymerisation. Two types of shell have been produced, composed of melamine formaldehyde or melamine formaldehyde-poly(hexamethylene adipate glycol). The microcapsules obtained were melt-compounded at 5%-wt with an isotactic polypropylene matrix using a twin-screw extruder, and multi-filaments have afterwards been spun from the various extrudates. The manufactured fibres were mechanically characterized by measuring their tensile properties, and their thermal properties were investigated by DSC and TGA. Finally, knitted fabrics were processed from the multi-filaments: their flame-retardant properties were evaluated by performing a fire test with a cone calorimeter, and their thermal conductivity measured with a Hot Disk. The different thermal behaviours are discussed in terms of the influence of system formulation on the overall thermal degradation, due to interactions between the different components of the flame-retardant microcapsules. The results showed that for one of the structures, an intrinsic intumescent flame-retardant system has been achieved.     

Synthesis and characterization of microencapsulated dicyclopentadiene with melamine–formaldehyde resins

Microcapsules containing healing agents have been used to develop the self-healing polymeric composites. These microcapsules must possess special properties such as appropriate strength and stability in surrounding medium. A new series of microcapsules containing dicyclopentadiene (DCPD) with melamine–formaldehyde (MF) resin as shell material were synthesized by in situ polymerization technology. These microcapsules may satisfy the requirements for self-healing polymeric composites. The chemical structure of microcapsule was identified by using Fourier transform infrared (FTIR) spectrometer. The morphology of microcapsule was observed by using optical microscope (OM) and scanning electron microscope. Size distribution and mean diameter of microcapsules were determined with OM. The thermal properties of microcapsules were investigated by using thermogravimetric analysis and differential scanning calorimetry. Additionally, the self-healing efficiency was evaluated. The results indicate that the poly(melamine–formaldehyde) (PMF) microcapsules containing DCPD have been synthesized successfully, and their mean diameters fall in the range of 65.2∼202.0 μm when the adjusting agitation rate varies from 150 to 500 rpm. Increasing the surfactant concentration can decrease the diameters of microcapsules. The prepared microcapsules are thermally stable up to 69 °C. The PMF microcapsules containing DCPD can be applied to polymeric composites to fabricate the self-healing composites.     

Thermal stability of microencapsulated epoxy resins with poly(urea-formaldehyde)

A series of microcapsules filled with epoxy resins with poly(urea-formaldehyde) (PUF) shell were synthesized by in situ polymerization, and they were heat-treated for 2 h at 100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C. The effects of surface morphology, wall shell thickness and diameter on the thermal stability of microcapsules were investigated. The chemical structure and surface morphology of microcapsules were investigated using Fourier-transform infrared spectroscope (FTIR) and scanning electron microscope (SEM), respectively. The thermal properties of microcapsules were investigated by thermogravimetric analysis (TGA and DTA) and by differential scanning calorimetry (DSC). The thermal damage mechanisms of microcapsules at lower temperature (<251 °C) are the diffusion of the core material out of the wall shell or the breakage of the wall shell owing to the mismatch of the thermal expansion of core and shell materials of microcapsules. The thermal damage mechanisms of microcapsules at higher temperature (>251 °C) are the decomposition of shell material and core materials. Increasing the wall shell thickness and surface compactness can enhance significantly the weight loss temperatures (T_d) of microcapsules. The microcapsules with mean wall shell thickness of 30 ± 5 μm and smoother surface exhibit higher thermal stability and can maintain quite intact up to approximately 180 °C.     

Optimization of parameters in preparation of PCM microcapsules based on melamine formaldehyde through dispersion polymerization

Microencapsulated phase change materials have attracted special attention due to their wide applications in saving and releasing energy. Here, microencapsulation of hexadecane (HD) in melamine formaldehyde shell was carried out through in situ dispersion polymerization in the aqueous media. Some important parameters such as stabilizer type and amount, surfactant amount, homogenization conditions as the critical affective factors on final particle size, morphology, and thermal resistance of the microcapsules were investigated extensively. The obtained microcapsules were concurrently analyzed by SEM, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. SEM images showed that the best stabilization was achieved by polyvinyl alcohol. Also, particle size, as an indication of surface area for heat transfer properties, showed a decrement by increasing stabilizer amount, surfactant amount, and homogenization speed. The amount of entrapped HD and efficiencies of microencapsulation were determined by DSC, and the reason for observing such changes were discussed in detail. Thermal stability of the microcapsules as an important property for their performance was investigated, too. The results illustrated that an improved thermal stability would be obtained by an efficient stabilization in the emulsification step. Also the highest thermal stability up to 388 °C was reached at homogenization speed of 6,000 rpm. Finally, the optimized conditions for desirable encapsulation were proposed in such systems.     

Intumescent flame retardation and silane crosslinking of PP/EPDM elastomer

This study deals with the silane crosslinking and intumescent flame retardation of polypropylene/ethylene‐propylene‐diene copolymer (PP/EPDM) elastomers. The effect of silane crosslinking on the flame retardancy of the PP/EPDM composites containing melamine phosphate (MP) and dipentaerythritol (DPER) was studied by limiting oxygen index, UL 94 and cone calorimetry tests. The chemical composition of the silane crosslinked and flame retarded PP/EPDM composites treated at different temperatures was studied by X‐ray photoelectron spectroscopy and real time Fourier transform infrared (FTIR) spectrometry. Thermal decomposition and crystallization behavior of the PP/EPDM composites were investigated using thermogravimetric analysis and differential scanning calorimetry, respectively. Moreover, the mechanical properties of the composites were also studied. It is found that the flame retardancy, mechanical properties, and thermal decomposition behavior of the composites are influenced by silane grafting and crosslinking. Copyright © 2008 John Wiley & Sons, Ltd.     

正十六烷聚脲微胶囊化相变材料

用界面聚合法，合成了直径大约2.5 μm可用于热能储存含相变材料的聚脲包覆微胶囊.在含乳化剂的水溶液中，将溶有芯材正十六烷的有机相乳化成微米级油性液滴，随后加入的水溶性单体二胺与甲苯2,4-二异氰酸酯在胶束界面相互反应形成囊壁.分别用乙烯二胺，1,6-己二胺和它们的混合物作为水溶性单体进行了研究.并用红外光谱和热分析分别考察了不同胺类对微胶囊化学结构和热性质的影响.红外谱图显示合成了聚脲微胶囊，热重曲线表明含正十六烷的聚脲微胶囊能够耐受大约300 ℃高温，差示扫描量热测试表明所有样品均具有合适的相转变热，冷热循环实验揭示微胶囊能够维持储热容量不衰减.研究表明微胶囊化的正十六烷作为相变储热材料具有良好的应用前景.     

Thermal degradation behavior of hyperbranched polyphosphate acrylate/tri(acryloyloxyethyl) phosphate as an intumescent flame retardant system

The hyperbranched polyphosphate acrylate (HPPA) was blended in different ratios with tri(acryloyloxyethyl) phosphate (TAEP) to obtain a series of UV curable intumescent flame retardant resins. The thermal degradation mechanism of their cured films in air was studied by thermogravimetric analysis and in situ Fourier-transform infrared spectroscopy. The results showed that the addition of HPPA reduced the initial decomposition temperature (T_di) but increased the char residue. Moreover, the decomposition was considered to be divided into three stages: firstly the degradation of phosphate group, secondly ester group and finally alkyl chain. The morphological structure of the formed char was observed by scanning electron microscopy, demonstrating the formation mechanism of the intumescent charred crust.     

Microencapsulation of bisphenol-A bis (diphenyl phosphate) and influence of particle loading on thermal and fire properties of polypropylene and polyethylene terephtalate

Microencapsulated flame retardant, bisphenol-A bis (diphenyl phosphate) (BDP), with a silane shell was prepared by sol–gel process with the goal of incorporating them in polymeric matrices by melt blending to improve the flame retardancy of isotactic polypropylene (iPP) and polyethylene terephtalate (PET). The influence of the loading content on thermal transitions has been studied by differential scanning calorimetry (DSC), the thermal stability of the polymer/microcapsules composites has been assessed by thermogravimetric analysis (TGA) and cone calorimetry has been used to study the fire reaction. It was noticed that the microcapsules have a limited influence on the thermal transitions of iPP matrix, but a decrease of the melting and glass transition temperatures was detected for the PET microcomposites. TGA results showed that the addition of microcapsules could improve char formation of the PET systems both in nitrogen and in air atmospheres, whereas only a small improvement of the thermal stability was detected in oxidative atmosphere for the iPP samples. Furthermore, cone calorimeter experiments show that the incorporation of microcapsules in the iPP gives almost no improvement in the iPP fire reaction. However, the microcapsules act as flame retardant in PET reducing the heat release rate during the combustion and the total heat evolved. Therefore, microcapsules can act as a char promoter agent to enhance the fire resistance in the case of PET.     

Synergistic effects of cerium phosphate and intumescent flame retardant on EPDM/PP composites

An intumescent flame retardant system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) was used for flame retarding ethylene–propylene–diene‐modified elastomer (EPDM)/polypropylene (PP) blends. Cerium phosphate (CeP) was synthesized and the effect on flame retardancy and thermal stability of EPDM/PP composites based on intumescent flame retardant (IFR) were studied by limiting oxygen index (LOI), UL‐94, and thermogravimetic analysis (TGA), respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) were used to analyze the morphological structure and the component of the residue chars formed from the EPDM/PP composites, and the mechanical properties of the materials were also studied. The addition of CeP to the EPDM/PP/APP/PER composites gives better flame retardancy than that of EPDM/PP/APP/PER composites. TGA and RT‐FTIR studies indicated that an interaction occurs among APP, PER, and EPDM/PP. The incorporation of CeP improved the mechanical properties of the materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene with MP/TPMP

The performances of the novel intumescent flame retardant (IFR) polypropylene (PP) composites containing melamine phosphate (MP) and tris(1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2,2,2]methylene‐4)phosphate (TPMP) were investigated. The flame retardancy of IFR‐PP system was characterized by limiting oxygen index (LOI) and UL 94 and cone calorimeter. The morphology of the char obtained after cone calorimeter testing was studied by scanning electron microscopy (SEM). The thermal oxidative degradation (TOD) of the composites was investigated by using thermogravimetric analysis (TGA) and real‐time Fourier transform infrared spectroscopy (RT‐FTIR). Compared with the PP/ TPMP or PP/ MP binary composite, at the same addition level, the LOI values of the PP/MP/TPMP ternary composites increase and reach V‐0 at the suitable MP/TPMP ratio. The results of TGA and RT‐FTIR showed the existence of the interaction between IFR and PP. Copyright © 2008 John Wiley & Sons, Ltd.     

Fire behavior of flame retarded unsaturated polyester resin with high nitrogen content additives

The novel flame retarded unsaturated polyester resins have been developed and prepared by introduction of high nitrogen content additives into the polymer matrix in order to verify their effectiveness in the formation of swollen carbonaceous char inhibiting the burning process of the polymer. The intumescent flame retardants (IFRs) based on mixture or metal complex were developed and characterized by particle size distribution, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD), elemental analysis (CHN) and thermogravimetric analysis (TGA). The evaluation of the efficiency of IFRs addition on the flammability and smoke emission of the unsaturated polyester resins (UP) was carried out using the fire hazard (UL-94), limiting oxygen index (LOI) and cone calorimeter (CC) tests, as well as smoke density chamber tests. The volatile compounds evolved during the burning of materials were determined using a steady state tube furnace and a gas chromatograph with mass spectrometer. Furthermore, the prepared materials were subjected to differential scanning calorimetry (DSC), thermogravimetric analysis and water resistance tests. The mechanical properties of the materials were investigated using Shore D hardness and dynamic mechanical thermal analysis (DMA). The structural evaluation of the manufactured materials and samples after the cone calorimetry tests was carried out using scanning electron microscopy (SEM). It was found that the incorporation of new intumescent flame retardants led to the formation of carbonaceous char layers’ inhibiting the decomposition process and limiting the smoke emission. The most promising results were obtained for the resin containing complex designated as ZN3AT, for which the highest reduction in maximum values of heat release rate (419 kW/m²) compared to unmodified polymer (792 kW/m²) were recorded. Apart from that, the prepared intumescent flame retardants affect the cross-linking process as well as the thermal and mechanical properties of the UP.     

Enhancing the flame-retardant and smoke suppression properties of transparent intumescent fire-retardant coatings by introducing boric acid as synergistic agent

A series of novel phosphorus-boron flame retardants (BPEAs) were successfully synthesized by introducing boric acid (BA) into cyclic phosphate ester acid (PEA) via the esterification and thoroughly characterized by ¹H nuclear magnetic resonance spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Five kinds of transparent fire-retardant coatings applied to wood substrates were produced by thoroughly mixing amino resin with PEA and BPEAs. The effects of BA on the optical transparency, thermal stability, fire performance and smoke emission characteristics of the coatings were investigated by various analytical instruments. The transparency analysis reveals that the transparency value of the coatings gradually decreases with increasing BA loading, and MPEA4 with the highest BA content still exhibits a high degree of transparency. The results from fire protection, cone calorimeter and smoke density tests show that the introduction of BA greatly decreases the flame spread rating, mass loss, char index, heat release rate, smoke production rate, total heat release, total smoke release and specific optical density of the coatings concomitant with the increase in the residual mass and intumescent factor, which is ascribed to the formation of a more dense and continuous intumescent char judging by digital photographs and scanning electron microscope images. Thermo-gravimetric analysis indicates that the onset decomposition temperature, high-temperature stability and residual mass of the coatings greatly improve with increasing BA content. FTIR analysis shows that the introduction of BA into the coatings contributes to generate more phosphorus-rich cross-linked structures and aromatic structures and then create a compact and intumescent char layer, thereby effectively enhancing the flame retardancy and smoke suppression properties of the coatings.     

The investigation of intumescent flame-retarded polypropylene using poly(hexamethylene terephthalamide) as carbonization agent

A novel intumescent flame retardant, containing ammonium polyphosphate (APP), and poly(hexamethylene terephthalamide) (PA6T), was prepared for flame retarding polypropylene (PP). The flame retardation of the PP composites was characterized by limiting oxygen index (LOI). The thermal degradation of the composites was investigated by means of thermogravimetric analysis (TG) and TG coupled with Fourier transform infrared spectroscopy (TG-FTIR). The morphology of the char obtained after combustion of the composites was studied by scanning electron microscopy. It has been found the intumescent flame retardant showed good flame retardancy, with the LOI value of the PA6T/APP/PP (5/25/70) system increasing from 17.5 to 32. Meanwhile, the TG and TG-FTIR work indicated that PA6T could be effective as a carbonization agent and there was a synergistic reaction between PA6T and APP, which effectively promoted the char formation of the PP composites. Moreover, it was revealed that uniform and compact intumescent char layer was formed after combustion of the intumescent flame retarded PP composites.     

Application of cooling curve analysis in solidification pattern and structure control of grey cast irons

In this article, the composites based on long glass fibre reinforced polypropylene/intumescent flame retardant (LGFPP/IFR) were prepared by melt blending. The influence of thermal oxidative ageing on the LGFPP/IFR composites with different thermal oxidative ageing time at 140 °C was studied by means of oven heating. The thermal stability and flammability of the composites were respectively investigated by thermal gravimetric analysis (TG), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), scanning electronic microscopy (SEM), mechanical properties test and energy-dispersive X-ray analysis (EDAX). A trend of increase first and then decrease in LOI values was shown in 0–50 days ageing, with the same trend as thermal stability obtained from TG in nitrogen condition. The CCT results indicated that the LGFPP/IFR composites after ageing achieved a higher heat release rate, which means a higher fire risk. The mechanical properties showed a global decrease in just 10 days ageing. Morphologies obtained from SEM showed that both the rupture of PP matrix and fibre interface debonding led to the decrease in mechanical properties. The EDAX proved that IFR particles could emerge and gather on the surface of sample in ageing procedure, which had great effects on the thermal stability and flame retardancy of the composites.     

The synergistic effect of adjuvant on the intumescent flame-retardant ABS with a novel charring agent

A laboratory-made poly-N,N′-ethyleneterephthalamide (PETA) was used as a novel charring agent and it was combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame retardant efficiency of IFR on acrylonitrile–butadiene–styrene copolymer (ABS), several adjuvant (Adj), such as zeolite 4A (4A), aluminum phosphinate (AlPi), organic montmorillonite, and 2,2′-bis(2-oxazoline), was added, and the synergistic effect was investigated by the limiting oxygen index (LOI), the UL-94 (vertical flame) test, the thermogravimetric analysis (TG), and the scanning electron microscopy (SEM). The results showed that the LOI values of ABS/IFR/Adj (70/30/2) system exceeded 30, and they passed the V-0 rating in the UL-94 test. The TG data demonstrated that the thermal stability and the mass residue of ABS/IFR/Adj were effectively enhanced. Besides, the SEM indicated that adjuvant promoted the formation of the compact, uniform, dense, and intumescent charred layer after burning. After that, the synergistic effect of AlPi and 4A on APP/PETA was investigated by Thermogravimetry-Fourier transform infrared spectroscopy.