<Emphasis Type="Italic">In situ</Emphasis> synthesis and modification of calcium carbonate nanoparticles via a bobbling method

Modified calcium carbonate (CaCO₃) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO₃ modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO₃ modified in the presence of sodium stearate, ODP and OA. When modified CaCO₃ was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO₃ nanoparticles and the organic matrixes were greatly improved. Supported by the National Natural Science Foundation of China (Grant No. 50372025)     

Thermal decomposition study of intumescent additives: Pentaerythritol phosphate and its blend with melamine phosphate

Thermal decomposition of pentaerythritol phosphate (PEPA) and its blend (PEPAMP) with melamine phosphate were studied by TG, DSC, TOF MS, and FTIR of volatile and solid decomposition products. Both PEPA and PEPAMP produce intumescent char on heating, however that of PEPAMP is less stable to thermo-oxidative decomposition. The main decomposition pathway of PEPA is liberation of phosphoric acid followed by formation of a foamed carbonized residue. In the mixture of PEPAMP, reaction between the components occurs, which strongly reduces the heat release peaks of PEPA. In addition, condensates of melamine and their products of hydrolysis are formed. The hydrolysis reaction causes a low-temperature decomposition of the melamine ring, which results in the formation of urea, carbon dioxide and ammonia. The thermal decomposition of PEPA and PEPAMP is discussed.     

Flame retardation and char formation mechanism of intumescent flame retarded polypropylene composites containing melamine phosphate and pentaerythritol phosphate

The flame retardation of polypropylene (PP) composites containing melamine phosphate (MP) and pentaerythritol phosphate (PEPA) was characterized by cone calorimeter. The formation mechanism of the char obtained from the combustion of the composites after cone calorimeter testing was studied by scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman diffusion. Results demonstrated that the PP composite containing MP and PEPA showed good flame retardancy. It had been found that the intumescent char could be principally divided into three parts, i.e. outer, middle and inner char layer, according to their different structures and components.     

Development of novel cardo‐containing phenylethynyl‐terminated polyimide with high thermal properties

A phenylethynyl‐terminated reactive diluent [Card‐4‐phenylethynylphthalic anhydride (PEPA)], which contained fluorenyl cardo structures, was successfully synthesized and used as a modifier for flexible phenylethynyl‐terminated imide oligomer (PEI‐PEPA). The chemical structure, crosslink characterization, molecular weights, and thermal properties of the products were characterized. The imide systems with addition of 10, 20, 30, and 40 wt% Card‐PEPA to PEI‐PEPA (PEI‐PEPA‐Card) and their cured resin systems were prepared. The thermal curing behaviors of imide systems at different heating rates were analyzed by using differential scanning calorimetry. Thermal properties such as glass transition temperature (T_g) and char yield at 800°C of the resultant resin systems were studied by differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The rheological properties were also investigated using a dynamic rheometry. These properties were found to be outstanding compared with pure PEI‐PEPA. The uncured imide systems exhibited lower T_g and lower isothermal viscosity with addition of Card‐PEPA. Furthermore, the T_g and char yield of the cured resin systems increased with addition of Card‐PEPA. The cured resin systems containing 40 wt% Card‐PEPA exhibited the highest T_g of 359°C and char yield at 800°C of 66.5%. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of microscale calcium carbonate and nanoscale calcium carbonate on the fusion,thermal, and mechanical characterizations of rigid poly(vinyl chloride)/calcium carbonate composites

A Haake torque rheometer equipped with an internal mixer has been used to study the influence of microscale calcium carbonate (micro‐CaCO₃) and nanoscale calcium carbonate (nano‐CaCO₃) on the fusion, thermal, and mechanical characteristics of rigid poly(vinyl chloride) (PVC)/micro‐CaCO₃ and PVC/nano‐CaCO₃ composites, respectively. The fusion characteristics discussed in this article include the fusion time, fusion temperature, fusion torque, and fusion percolation threshold (FPT). The fusion time, fusion temperature, and FPT of rigid PVC/calcium carbonate (CaCO₃) composites increase with an increase in the addition of micro‐CaCO₃ or nano‐CaCO₃. In contrast, the fusion torque of rigid PVC/CaCO₃ composites decreases with an increase in the addition of micro‐CaCO₃ or nano‐CaCO₃. The results of thermal analysis show that the first thermal degradation onset temperature (T_onset) of rigid PVC/micro‐CaCO₃ is 7.5 °C lower than that of PVC. Meanwhile, the glass‐transition temperature (T_g) of rigid PVC/micro‐CaCO₃ is similar to that of PVC. However, T_onset and T_g of PVC/nano‐CaCO₃ composites can be increased by up to 30 and 4.4%, respectively, via blending with 10 phr nano‐CaCO₃. Mechanical testing results for PVC/micro‐CaCO₃ composites with the addition of 5–15 phr micro‐CaCO₃ and PVC/nano‐CaCO₃ composites with the addition of 5–20 phr nano‐CaCO₃ are better than those of PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 451–460, 2006     

Thermal degradation of pentaerythritol phosphate alcohol

Intumescent material, 2,6,7-trioxa-1-phosphabicyclo-[2,2,2]-octane-4-methanol phosphate (PEPA), is synthesized and characterized using FTIR, ¹HNMR and ¹³CNMR. The degradation properties of PEPA are studied by employing TG and TG?CMS technique. The activation energies for the degradation process of PEPA are calculated by using TG curves obtained from multiple heating rates (Friedman, Kissinger?CAkahira?CSunose and Flynn?CWall?COzawa methods). The degradation that is occurring in the temperature region 307?C366?°C has the highest activation energy. Eventhough the calculated activation energies for the degradation differ depending on the approximation method employed, the trend in variation of activation energy for degradation is similar. Single ion monitoring technique proved the evolution of H₂O, CO/C₂H₄, HCHO, C₂H₅OH/HCOOH and trace amounts of C₂H₇O₃P and C₄H₉O₄P from the degrading PEPA. The thermal conductivity and stability of the char formed during the TG analysis are also discussed.     

Effect of a novel phosphorous-nitrogen containing intumescent flame retardant on the fire retardancy and the thermal behaviour of poly(butylene terephthalate)

A novel phosphorus-nitrogen containing intumescent flame retardant (P-N IFR) was prepared via the reaction of a caged bicyclic phosphorus (PEPA) compound and 4,4′-diamino diphenyl methane (DDM) in two steps. The product was added to poly(butylene terephthalate) (PBT) to obtain halogen-free flame retarded polyester. UL-94 test, thermogravimetry and in situ infrared spectroscopy were used to characterize the flammability, thermal degradation properties and the char-forming process. It was shown that the phosphorus-nitrogen containing compound could improve both the flame retardancy and thermal stability more effectively than other P-N flame retardants. Furthermore, it was a good char-forming agent incorporated with the co-addition of polyurethane (PU) when the combustion occurred. The formation of P-N structure was incorporated in the char layer.     

Synthesis of a caged bicyclic phosphates derived anhydride and its performance as a flame‐retardant curing agent for epoxy resins

A novel curing and flame‐retardant agent (PEPA‐TMAC) was successfully synthesized. The chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Use of PEPA‐TMAC as part of the curing agent in combination with another anhydride for a commercial epoxy resin (EP) was studied. Results of differential scanning calorimetry (DSC) indicated that PEPA‐TMAC was an effective curing agent for EP. The dynamic mechanical analysis (DMA) results showed that the glass transition temperature (T_g) and cross‐linking density (V_e) of EP composites exhibited an increase trend with the addition of PEPA‐TMAC. The limiting oxygen index (LOI) value of EP composites reached 26.9%, and the cone calorimeter results indicated that peak heat release rate (PHRR), total heat release (THR), smoke produce rate (SPR), and total smoke produce (TSP) remarkably decreased with increasing PEPA‐TMAC content. TGA data showed that the addition of PEPA‐TMAC greatly increased the amount of residual char during combustion. The morphology of the residual char was studied by SEM and showed that the addition of PEPA‐TMAC greatly increased the stability of EP composites. The thermogravimetric analysis (TGA), energy‐dispersive X‐ray spectroscopy (EDS), and FTIR results revealed the flame‐retardant mechanism that PEPA‐TMAC can promote the formation of charred layers with the phospho‐carbonaceous complexes in the condensed phase during burning of EP composites.     

聚磷酸酯阻燃剂复配聚磷酸铵对环氧树脂阻燃性能的影响

合成了一种9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)的衍生物——聚苯氧基磷酸-2-10-氢-9-氧杂-磷杂菲基对苯二酚酯(POPP), 以间苯二胺(m-PDA)为固化剂, 环氧树脂(EP)为基料, POPP为阻燃剂, 复配聚磷酸铵(APP), 制备了不同磷含量的阻燃环氧树脂. 利用极限氧指数(LOI)和垂直燃烧(UL94)实验表征了环氧树脂的阻燃性能; 以热重分析、 锥型量热和扫描电镜分析了阻燃环氧树脂的热性能和表面形态. 研究结果表明, 阻燃剂总加入量(质量分数)为5%时即可达到UL94 V-0级, 同时LOI值为27.7%; 当总加入量为15%, 即w_POPP=5%, w_APP=10 %时, 其LOI值可达到33.8%. 随着磷含量的增加, 阻燃环氧树脂的初始降解温度略有降低, 但高温下的残炭率明显增加. POPP/APP的加入在很大程度上降低了环氧树脂的热释放速率、 有效燃烧热、 烟释放量和有毒气体释放量. 阻燃环氧树脂在高温下形成比较稳定的致密膨胀炭层, 为底层的环氧树脂主体隔绝了分解产物及热量和氧气交换, 增强了高温下的热稳定性.     

Facile synthesis of calcium carbonate/polyacrylic acid hydrogels for pH-responsive delivery of cytarabine

Cytarabine (Cyt) encapsulated calcium carbonate (CaCO₃) nanospheres were facilely synthesized through a simple co-precipitation method, and the Cyt encapsulated CaCO₃ nanospheres (CaCO₃/Cyt) were modified by polyacrylic acid (PAA) hydrogels through in situ polymerization of acrylic acid (AA) monomer on the surface of the CaCO₃/Cyt. Successful preparation of the Cyt loaded CaCO₃/PAA hydrogels were confirmed by the characterization of SEM, TEM and FT-IR. Premature release of Cyt in acidic medium (pH = 1.2) could be effectively circumvented by the introduction of the PAA hydrogels. More importantly, pH-responsive delivery of Cyt from the as-prepared CaCO₃/PAA hydrogels could be achieved due to the pH-sensitivity of the PAA. Although the highest swelling ratio of PAA was obtained at pH 7.3 (27.7), the highest cumulative release of Cyt from the carrier was achieved at pH 5.3 (86.75%), which might be attributed to the high stability of CaCO₃ at pH 7.3. That is to say, the highest cumulative release of Cyt at pH 5.3 was a compromise by considering the relatively high swelling ratio of PAA and the relatively low stability of CaCO₃.     

Preparation and properties of negative ion/polyurethane flexible foam composites

Abstract

In this study, negative ionpowder was modified with a silane coupling agent and then added to the polyurethane flexible foam to prepare NI/PU flexible foam composites by the one-step foaming method. The effects of the amount of negative ion powder on the mechanical properties, thermal properties and release of negative ions were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and negative ion detectors. The SEM results showed that modified negative ion powder could be more uniformly distributed around the cell walls of the polyurethane flexible foam. The thermal stability, tensile strength and resilience of the NI/PU flexible foam composite were improved with the increase of the amount of modified negative ion powder. Increasing the amount of modified negative ion powder could also result in an increase in the release of negative ions, and it reached 5500/cm³ or higher at a negative ion content of 3%.     

Hydrophobic,superabsorbing materials from reduced graphene oxide/MoS2 polyurethane foam as a promising sorbent for oil and organic solvents

This study illustrates the preparation of robust superhydrophobic and superoleophilic reduced graphene oxide (rGO) and MoS₂ nanoparticles incorporated polyurethane (PU) foam by in-situ polymerization via the one-shot method. Spectroscopic analyses confirmed the successful formation of nanoparticles and also the development of the hybrid PU material. The sponges were evaluated based on hydrophobicity and oil absorbance capacities and the modified foam exhibits the water contact angle of 151°. The pore size of the foam analyzed using an optical microscope and the effect on the density and porosity were also analyzed. The oil absorption capacity of the foam was studied using standard sorption testing. The oil and organic solvent selectivity and recyclability of hybrid PU foam were performed to estimate whether the foams could be recycled and reused. The modified system shows very high selectivity (83–94%). The recyclability of the foam was about 35 cycles without much reduction in its own weight and after 55 cycles more than 80% of the oil absorption capacity was conserved. The resulting hybrid PU material is highly efficient, porous, ultralight, hydrophobic and reusable sorbent material and displays great potential for versatile environmental remediation.     

Porous Organic Polymers as Fire-Resistant Additives and Precursors for Hyperporous Carbon towards Oxygen Reduction Reactions

Cyclotriphosphazene (CP) based porous organic polymers (POPs) have been designed and prepared. The introduction of CP into the porous skeleton endowed special thermal stability and outstanding flame retardancy to prepared polymers. The nonflammable level of PNK-CMP fabricated via the condensation of 2,2′-(1,4-phenylene)diacetonitrile (DAN) and hexakis(4-acetylphenoxy)cyclotriphosphazene (HACTP) through Knoevenagel reaction, in vertical burning tests reached V-2 class (UL-94) and the limiting oxygen index (LOI) reached 20.8 %. When used as additive, PNK-CMP could suppress the dissolving out of PEPA effectively, reducing environment pollution and improving the flame retardant efficiency. The POP and PEPA co-added PU (m_POP%: m_PEPA%=5.0 %: 5.0 %) could not be ignited under simulated real-scale fire conditions. The nonflammable level of POP/PEPA/PU in vertical burning tests (UL-94) reached V-0 class with a LOI as high as 23.2 %. The smoke emission could also be suppressed, thus reducing the potential for flame spread and fire hazards. Furthermore, carbonization of PNK-CMP under the activation of KOH yield a hyperporous carbon (PNKA-800) with ultrahigh BET surface area (3001 m² g⁻¹) and ultramicropore size showing excellent ORR activity in alkaline conditions.     

The study of mechanical behavior and flame retardancy of castor oil phosphate-based rigid polyurethane foam composites containing expanded graphite and triethyl phosphate

The goal of this work was the synthesis of novel flame-retarded polyurethane rigid foam with a high percentage of castor oil phosphate flame-retarded polyol (COFPL) derived from renewable castor oil. Rigid flame-retarded polyurethane foams (PUFs) filled with expandable graphite (EG) and diethyl phosphate (TEP) were fabricated by cast molding. Castor oil phosphate flame-retarded polyol was derived by glycerolysis castor oil (GCO), H₂O₂, diethyl phosphate and catalyst via a three-step synthesis. Mechanical property, morphological characterization, limiting oxygen index (LOI) and thermostability analysis of PUFs were assessed by universal tester, scanning electron microscopy (SEM), oxygen index testing apparatus, cone calorimeter and thermogravimetric analysis (TGA). It has been shown that although the content of P element is only about 3%, the fire retardant incorporated in the castor oil molecule chain increased thermal stability and LOI value of polyurethane foam can reach to 24.3% without any other flame retardant. An increase in flame retardant was accompanied by an increase in EG, TEP and the cooperation of the two. Polyurethane foams synthesized from castor oil phosphate flame-retarded polyol showed higher flame retardancy than that synthesized from GCO. The EG, in addition to the castor oil phosphate, provided excellent flame retardancy. This castor oil phosphate flame-retarded polyol with diethyl phosphate as plasticizer avoided foam destroy by EG, thus improving the mechanical properties. The flame retardancy determined with two different flame-retarded systems COFPL/EG and EG/COFPL/TEP flame-retarded systems revealed increased flame retardancy in polyurethane foams, indicating EG/COFPL or EG/COFPL/TEP systems have a synergistic effect as a common flame retardant in castor oil-based PUFs. This EG/COFPL PUF exhibited a large reduction of peak of heat release rate (PHRR) compared to EG/GCO PUF. The SEM results showed that the incorporation of COFPL and EG allowed the formation of a cohesive and dense char layer, which inhibited the transfer of heat and combustible gas and thus increased the thermal stability of PUF. The enhancement in flame retardancy will expand the application range of COFPL-based polyurethane foam materials.     

Effect of charring agents on solvent‐free fireproof coatings

The choice of charring agent is one of the major issues for solvent‐free fireproof coatings. The effects of processing method and charring agent on the thermal insulation and fire resistance of the coatings were investigated in simulated fire scenarios. Dipentaerythritol (DPER), triazine agent (CFA), and pentaerythritol phosphate (PEPA) were compared as charring agent, and the thermal, combustion, fire resistance, and charring behaviors in different fire scenario were characterized for the fireproof coatings. Compared with high‐speed dispersing equipment, kneading processing equipment is favorable for improving the thermal stability and fire resistance of the coatings, because the stronger shearing force has promoted mixing and dispersion of the ingredients in solvent‐free fireproof coatings. As for charring agents, it is found that the fireproof coatings containing CFA or PEPA show better thermal and flame‐retardant performances. More residue was observed under nitrogen atmosphere in thermogravimetric analysis, less heat and smoke were released in cone calorimetry test. However, during the high temperature fire resistance test, their char layers were prone to delaminate while DPER‐containing coatings produced intact and stronger char layer with better heat insulation. For practical applications, the coating formulations need to be optimized to achieve both fire resistance and flame retardancy.     

以乙烯基酯树脂为多元醇制备聚氨酯硬质泡沫塑料的研究

研究了用乙烯基酯树脂（ＶＥＲ）直接代替通常的聚醚或聚酯型多元醇制备聚氨酯（ＰＵ）硬质泡沫塑料的可能性。实验结果表明,发泡配方中促进氨酯化反应的催化剂Ｎ,Ｎ－二甲基环己胺能与ＢＰＯ复合形成室温引发体系,加速ＶＢＲ的共聚合反应,影响了ＰＵ硬质泡沫塑料形成过程中的发泡与凝胶反应,导致泡了孔骨架基材的交联密度较低,泡孔结构不规整,并显示出较差的物理性能。以ＡＩＢＮ为引发剂时,反应初期主要进行氨酯化反应;仅     

Mechanical properties,thermal stability,sound absorption,and flame retardancy of rigid PU foam composites containing a fire‐retarding agent: Effect of magnesium hydroxide and aluminum hydroxide

Isocyanate, polyether polyol, a flame retardant (10 wt%), and aluminum hydroxide/magnesium hydroxide (0, 5, 10, 15, and 20 wt%) are used to form the rigid polyurethane (PU) foam, while nylon nonwoven fabrics and a polyester aluminum foil are combined to serve as the panel. The rigid PU foam and panel are combined to form the rigid foam composites. The cell structure, compressive stress, combustion resistance, thermal stability, sound absorption, and electromagnetic interference shielding effectiveness (EMI SE) of the rigid foam composites are evaluated, examining the effects of using aluminum hydroxide and magnesium hydroxide. Compared with magnesium hydroxide, aluminum hydroxide exhibits superior performance to the rigid foam composites. When aluminum hydroxide is 20 wt%, the rigid foam composite has an optimal density of 0.153 g/cm³, an average cell size of 0.2466 mm, a maximum compressive stress of 546.44 Kpa, an optimal limiting oxygen index (LOI) of 29.5%, an optimal EMI SE of 40 dB, and excellent thermal stability and sound absorption.     

Study of thermal properties of intumescent additive

Bicyclic compounds containing phosphorus on their skeleton such as 2,4,6-trioxa-1-phosphabicyclo[2,2,2]octane-4-methanol phosphate (PEPA) having three active ingredients required for intumescence have been synthesized. The structural characterization of PEPA was carried out by FT-IR, ¹H and ¹³C NMR. The thermal behaviour of the material was studied using TGA, TGA–MS and pyrolysis GC–MS. Thermogravimetric analysis reveals that PEPA undergoes several stages of degradation with a char of about 12% at 800 °C. The TGA–MS studies indicate that the material degrades with the liberation of water, formaldehyde, alkene and alcohols as the major degradation products. Pyrolysis GC–MS results reveal that PEPA isomerizes in the acidic medium. PEPA and/or isomers of PEPA react with formaldehyde, one of the degradation products, to form cross-linked structure and cyclic products with the elimination of water molecule. The thermal degradation mechanisms for PEPA are presented and discussed.     

Effect of a Nanodispersed Clay Fillers on Glass Transition of Thermosetting Polyurethane

In this work polyurethane (PU) matrix nanocomposite, obtained using an organically modified montmorillonite (OMM), was synthesized and characterized. An amount of organoclay ranging from 2% up to 6% by volume was added to the polyol component of the resin before mixing with isocyanate. The microstructure of the composites was investigated by X-ray diffraction. The glass transition temperature (T_g) of PU nanocomposites, measured using differential scanning calorimeter, increases with increasing the volume fraction of OMM. On the other hand, the heat capacity increment, ΔC_p, decreases from that the unfilled PU to that of the sample with 5.7% vol of OMM. Therefore a corresponding increase of the rigid amorphous fraction of PU nanocomposites with nanoclay was observed. Finally, the definition of molecular cooperativity was discussed for this system and the characteristic length of the cooperative region was determined, using the approach proposed by Donth.     

The thermal stability of fully charged and discharged LiCoO2 cathode and graphite anode in nitrogen and air atmospheres

Polyethylene glycol (PEG) compounds and mixtures have many properties that make them suitable for thermal applications in buildings, such as having high heat of fusion, phase change repeatability, chemical stability, non-corrosive behavior, and low-cost. In this study, we developed a number of PU rigid foams incorporated with three types of PEGs, as new insulation materials provided with an enhanced thermal capacity, and sought their suitability for various applications such as layer of floor and ceiling coverings in constructions, insulations in controlled temperature transportation packaging, inner coverings of automobile seats, etc. In order to investigate the thermal properties of PEG-containing PU foams, differential scanning calorimeter (DSC) tests were conducted first. Then, a two-layer concrete–PU foam system was designed in the laboratory conditions to examine the insulation performances via using a computer-aided thermal measurement setup which was sensitive to the simulated environmental temperature changes. The PU-PEG composites produced here can be helpful for the design of thermal insulators. PUI, including 44% PEG 600, exhibited fairly efficient thermal regulation under moderate ambient temperature conditions, whereas PUII (49% PEG 1000) is suitable for temperature control in both mild and hot surroundings. PUIII, containing 53% PEG 1500, showed suitable heat storage and thermal stability characteristics. PUIV, containing 38% PEG 600/PEG 1000/PEG 1500, also confirmed good thermal and durability characteristics. The blend of three PEGs is suitable for preventing discontinuous thermal regulation when the external temperature increases or decreases. PU foams containing PEGs can be assumed to be leak-resistant, which is promising for their industrial applications.