Preparation of piperazine cyanurate by hydrogen‐bonding self‐assembly reaction and its application in intumescent flame‐retardant polypropylene composites

Piperazine cyanurate (PCA) is designed and synthesized via hydrogen‐bonding self‐assembly reactions between piperazine and cyanuric acid. Chemical structure and morphology of PCA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The prepared PCA is combined with ammonium polyphosphate (APP) to prepare flame‐retardant polypropylene (PP) composites. Thermostability, flammability, and combustion characteristics of PP composites are analyzed. The maximum thermal decomposition rate of flame‐retarded PP composites has an apparent reduction compared with that of pure PP, and obvious char is left for this intumescent flame retardant (IFR) system of APP and PCA. A high limiting oxygen index value and UL‐94 V‐0 rating are achieved with addition of APP and PCA. In cone calorimetry test, heat and smoke releases of PP are significantly decreased by this IFR system. Gaseous decomposition products during the thermal decomposition of flame‐retardant composites are studied. Chemical structure and morphology of char residues are analyzed. The results illustrate that APP and PCA have a superb synergistic action in the aspect of improvement in fire safety of PP. A possible flame‐retardant mechanism is concluded to reveal the synergism between APP and PCA.     

Flammability and thermal degradation of flame retarded polypropylene composites containing melamine phosphate and pentaerythritol derivatives

The flammability of polypropylene (PP) composites containing intumescent flame retardant additives, i.e. melamine phosphate (MP) and pentaerythritol (PER), dipentaerythritol (DPER) or tripentaerythritol (TPER) was characterized by limiting oxygen index (LOI), UL 94 and the cone calorimeter, and the thermal degradation of the composites was studied using thermogravimetric analysis (TG) and real time Fourier transform infrared (RTFTIR). It has been found that the PP composite containing only MP does not show good flame retardancy even at 40% additive level. Compared with the PP/MP binary composite, the LOI values of the PP/MP/PER (PP/MP/DPER or PP/MP/TPER) ternary composites at the same additive loading are all increased, and UL 94 ratings of most ternary composites studied are raised to V-0 from no rating (PP/MP). The cone calorimeter results show that the heat release rate and smoke emission of some ternary composites decrease in comparison with the binary composite. It is noted from the TG data that initial decomposition temperatures of ternary composites are lower than that of the binary composite. The RTFTIR study indicates that the PP/IFR composites have higher thermal oxidative stability than the pure PP.     

Nanosized carbon black as synergist in PP/POE-MA/IFR system for simultaneously improving thermal,electrical and mechanical properties

Nanosized carbon black (CB) was introduced into polypropylene/maleic anhydride-grafted polyolefin elastomer/intumescent flame retardant (PP/POE-MA/IFR) system to investigate the effect of nanofiller as synergist on thermal, electrical and mechanical properties of polymer composites. With 5 mass% CB into PP/POE-MA/IFR system (POFC5), the T_max (corresponded to the temperature at the maximum mass loss rate) under air was increased by 122.4 °C; its limited oxygen index was as high as 31.4%; its vertical burning rating (UL-94) reached V0, and the peak value of heat release rate was decreased to only 19% of neat PP in cone calorimeter testing. Moreover, PP composites exhibited good electrical conductivity with more than 1.6 mass% CB, which is a low loading level to reach the critical percolation concentration. In addition, a good balance on stiffness and toughness of PP composites was achieved; especially, Young’s moduli and impact strength of POFC5 were increased to 1.26 and 2.5 times in comparison with that of neat PP, respectively. These results indicated that CB was an effective synergist in multi-component PP composites to simultaneously improve thermal, electrical and mechanical properties.

     

Synergistic improvement of fire retardancy and mechanical properties of ferrocene‐based polymer in intumescent polypropylene composite

The ferrocene‐based polymer (PDPFDE) accompanied with traditional intumescent flame retardant (IFR) system (ammonium polyphosphate (APP)/pentaerythritol (PER) = 3/1, mass ratio) has been used as additive flame retardant in polypropylene (PP), aiming to lower the total loading amount. The thermal stability and fire retardant properties were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical combustion (UL‐94), and cone calorimetry (CONE). The fire retardant mechanism was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The results showed that the PP1 with 25 wt% IFR only passed the UL‐94 V‐1 rating, but the PP6 loaded by 0.5 wt% PDPFDE and 22.5 wt% IFR possessed an LOI value of 28.5% and passed the UL‐94 V‐0 rating; the peak heat release rate (pHRR) and total heat release (THR) are decreased by 63% and 43%, respectively, compared with pure PP. In addition, the char residue of PP6 manifested a very compact and smooth surface, indicating a more effective barrier layer. Meanwhile, it was interesting that the addition of PDPFDE evidently improved the impact strength and elongation at break of PP/IFR composites.     

Tensile and flexural properties of polypropylene composites filled with highly effective flame retardant magnesium hydroxide

The reinforcing effects of highly effective flame retardant magnesium hydroxide (FMX) content on the tensile and flexural properties of filled polypropylene (PP) composites were investigated within the FMX weight fraction range from 5 to 60 wt%. It was found that the Young's modulus and flexural modulus increased approximately linearly while the tensile yield strength and tensile fracture strength decreased slightly with increasing the FMX weight fraction. When the FMX weight fraction was lower than 20%, the tensile elongation at break decreased considerably, and then decreased slightly; the flexural strength increased when the FMX weight fraction was lower than 30%, and then decreased slightly. The tensile properties increased with increasing rate of tension. Moreover, the tensile yield strength of the composites was estimated using an equation proposed in previous work, and good agreement was shown between the predicted and the measured data.     

A study of PP/PET composites: Factorial design,mechanical and thermal properties

Due to the economic importance of polypropylene (PP) and polyethylene terephthalate (PET), and the large amount of composites made with PP matrix and recycled PET as reinforcing material; an investigation was performed regarding the mechanical and thermal behavior of PP composites containing recycled polyethylene terephthalate fibers (rPET). Interfacial adhesion between the two materials was achieved by adding a compatibilizer, maleic anhydride grafted polypropylene, PP-g-MA. Mechanical behavior was assessed by tensile, flexural, impact and fatigue tests, and thermal behavior by HDT (Heat Deflection Temperature). Fractured surfaces and fiber were investigated by scanning electron microscopy. Multiple regression statistical analysis was performed to interpret interaction effects of the variables. Tensile strength, tensile modulus, flexural strength, flexural modulus and HDT increased after rPET fiber incorporation while strain at break, impact strength and fatigue life decreased. Addition of compatibilizer increased tensile strength, flexural strength and flexural modulus, fatigue life and HDT while tensile modulus, strain at break and impact strength decreased. However, at low fiber content, the impact strength increased, probably due to nucleation effects on PP.     

Synthesis of a novel hybrid synergistic flame retardant and its application in PP/IFR

A novel inorganic-organic hybrid synergistic flame retardant was prepared by sol-gel reaction and characterized by NMR and FT-IR. It showed that the fire resistance of polypropylene/intumescent flame retardant (PP/IFR) composites could be improved with the combination of hybrid synergistic flame retardant. The char morphology and structure of PP composites were characterized by SEM and Raman spectra. The influence of the hybrid flame retardant on the thermal degradation process of PP composites was analyzed by FT-IR and the rheological behavior of the PP composites was also evaluated. The thermal stability of PP composites was characterized by TGA, weight loss difference and integral procedural decomposition temperature (IPDT). It indicated that the hybrid synergistic flame retardant had good synergistic effect with IFR.     

Mechanical properties and morphology of intumescent flame retardant filled polypropylene composites

The intumescent flame retardant (IFR) filled polypropylene (PP) composites were prepared using a twin‐screw extruder. The tensile and impact fracture behavior of the composites were measured at room temperature. It was found that the Young's modulus increased roughly, while the tensile strength decreased slightly with increasing the IFR weight fraction; the toughening effect of the filler on the PP resin was significant. Both the V‐notched Izod impact strength and the V‐notched Charpy impact strength of the PP/IFR composites showed a nonlinear increase with increasing the filler weight fraction (φ_f) as φ_f was less than 20%, then it decreased. The limited oxygen index of the composites increases nonlinearly with increasing φ_f. The relationship between them obeyed a quadratic equation. The impact fracture surface was observed by means of a scanning electronic microscope to understand the toughening mechanisms for the composite systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of polysiloxane and silane‐modified SiO2 on a novel intumescent flame retardant polypropylene system

The effects of polysiloxane and silane‐modified SiO₂ (M‐SiO₂) on properties of intumescent flame retardant polypropylene (IFR‐PP) have been studied. The results demonstrate that both polysiloxane and M‐SiO₂ could effectively enhance the flame retardancy of the IFR‐PP, despite only 20 wt% loading of IFRs. Remarkably, the polysiloxane can clearly improve the water resistance of IFR‐PP. It can obtain UL‐94 V‐0 rating, and its LOI remains over 34% after the water treatment. The surface tension data, XPS data, and SEM sufficiently prove that the some of polysiloxane transfers to the IFR‐PP surface during processing. The TGA data show that the polysiloxane more effectively enhances the thermal stability of the IFR‐PP at high temperature and increases the char residue. The CONE results reveal that the polysiloxane can clearly change the decomposition behavior of PP and markedly reduce flammability parameters. The homogenous and compact intumescent char layers further confirm that polysiloxane is a very effective silicon‐containing additive for the flame retardancy and water resistance of the IFR‐PP. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic Effect of Novel Synergists–Transition Metal Ion-incorporated Nickel Phosphates with Intumescent Flame Retardants in Polypropylene

The two kinds of transition metal ion-incorporated nickel phosphates (TMIVSB-1) were synthesized by the hydrothermal method. The flame retardancy and thermal behavior of intumescent flame retardants (IFR), with and without TMIVSB-1 for PP, were investigated by LOI, UL-94 test, thermogravimetric analyses (TGA) and cone calorimetry. TMIVSB-1 can obviously improve the flame retardant behavior of IFR systems according to the results of LOI values and UL-94 test. The results of LOI show that 2 wt% TMIVSB-1 can increase the LOI value by 3–5 unit compared with that of PP/IFR composite. The UL-94 test shows that PP with 20% IFR burns and has no rating, but the addition of a small content 2 wt% of TMIVSB-1 with 18 wt% of IFR can reach a UL-94 V-0 rating. TGA results show that the thermal stability of PP/IFR/TMIVSB-1 increases obviously more than that of PP/IFR when the temperature is above 265°C. From cone calorimetry results, it can be observed that the HRR peaks are not obviously decreased, but the burning time of PP/IFR/FeVSB-1 (351s) and PP/IFR/ZnVSB-1 (380s) is obviously prolonged compared with that of PP/IFR (303s). The real time FTIR spectra (RTFTIR) demonstrates that the addition of TMIVSB-1 further staves the decomposition of the PP composites. The scanning electron microscopy (SEM) indicates the quality of char forming of PP/IFR/ TMIVSB-1 is superior to that of PP/IFR.     

Effect of anion of polyoxometalate based organic–inorganic hybrid material on intumescent flame retardant polypropylene

In this work, 12‐tungestocobaltic acid based organic–inorganic hybrid material, [Bmim]₆CoW₁₂O₄₀ (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were investigated by the limiting oxygen index (LOI), UL‐94 vertical burning test, thermal gravimetric analyzer (TGA), cone calorimeter and scanning electron microscopy (SEM) etc. The results showed that the PP composites with 16 wt% IFR and 1 wt% CoW achieves the UL‐94 V‐0 rating and gets a LOI value 28.0. However, only add no less than 25 wt% single IFR, can the PP composites obtain the UL‐94 V‐0 rating, which suggests that CoW has good synergistic effects on flame retardancy of PP/IFR composites. In addition, the SEM and cone calorimeter tests indicated the CoW improves the quality of char layer. The rate of char formation has been enhanced also because of the existence of CoW. It is the combination of a better char quality and a high rate of char formation promoted by CoW that results in the excellent flame retardancy of PP/IFR composites. Copyright © 2016 John Wiley & Sons, Ltd.     

The influence of recycling on the properties of wood fibre — Plastic composites

The manufacture of composites offers the greatest flexibility to convert and utilize waste plastics, paper and wood into high-value products. This paper reports on two studies regarding the recycling of these materials. In one study, recycling was simulated by regrinding and injection-moulding composites of polypropylene (PP), polyethylene (PE) and old newsprint (ONP) eight times. The results indicated that reprocessing had only minor deleterious effect on the mechanical properties (tensile and flexural). The viscosity of neat PP decreased with repeated recycling indicating some thermo-oxidative degradation. The overall rheological character of PP composites did not change much. PE composites, on the other hand, showed increasing melt flow with reprocessing. The second study examined the effects of various coupling agents on the properties of multicomponent PP composites. Maleated polypropylene (MAPP) was the most effective coupling agent.     

Preparation of Intumescent Flame Retardant Polypropylene composite through Solid State Mechanochemical Method

Polypropylene (PP), with characteristics of good mechanical properties, good resistance to water and low cost, has been widely used in many fields such as building, transport, furniture and electrical industries. However, a fateful drawback of polypropylene is its high flammability,restricting its wider applications. Addition of flame retardants is an effective way to improve its flame retardancy. An effective halogen-free flame retardant system used is the mixture of melamine, ammounium phosphate and pentaerythritol (intumescent flame retardant). But how to enhance the dispersion of this mixture in polypropylene matrix is a big problem. A self-made mechanochemical reactor, pan type milling equipment, can exert strong shear and squeeze forces,and has good mixing function. As a result, a uniform dispersion of flame retardants in the polymer matrix can be expectably obtained by using this equipment.In this paper, flame-retarded Polypropylene (PP) composites with intumescent flame retardant (IFR) were prepared via solid state mechanochemical method (pan-mill) and conventional method (twin-roll masticator) respectively. Particle diameter analysis, melt flow index (MFI), differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM) were used to characterize these composites, and the mechanical properties and flame retardancy were also determined. The experimental results showed that the blend of PP and IFR were effectively pulverized from 3～4 mm to less than 300i m under the strong shear forces of pan-mill. With increasing the milling cycles, the MFI value of IFR/PP blend decreased first and then increased. The mechanical properties and flame retardancy of IFR/PP blends prepared by solid state mechanochemical method were proved to be better than those prepared by conventional method because of the dispersing function of pan-mill.Also it was found that IFRs were the nucleating agent for PP and the crystallinity of PP increased first and then decreased with increasing the milling cycles.     

Synthesis of a novel ionic liquid containing phosphorus and its application in intumescent flame retardant polypropylene system

A novel ionic liquid containing phosphorus ([PCMIM]Cl) was synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR. Moreover, a new intumescent flame retardant (IFR) system, which was composed of [PCMIM]Cl and ammonium polyphosphate (APP), was used to impart flame retardancy and dripping resistance to polypropylene (PP). The flammability and thermal behaviors of intumescent flame‐retarded PP (PP/IFR) composites were evaluated by limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA) and cone calorimeter test. It was found that there was an obvious synergistic effect between [PCMIM]Cl and APP. When the weight ratio of [PCMIM]Cl and APP was 1:5 and the total amount of IFR was kept at 30 wt%, LOI value of PP/IFR composite reached 31.8, and V‐0 rating was obtained. Moreover, both the peak heat release rate and the peak mass loss rate of PP/IFR composites decreased significantly relative to PP and PP/APP composite from cone calorimeter analysis. The TGA curves suggested that [PCMIM]Cl had good ability of char formation, and when combined with APP, it could greatly promote the char formation of PP/IFR composites, hence improved the flame retardancy. Additionally, the rheological behaviors and mechanical properties of PP/IFR composites were also investigated, and it was found that [PCMIM]Cl could also serve as an efficient lubricant and compatibilizer between APP and PP, endowing the materials with satisfying processability and mechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.     

PP-g-(MAH/St)和PP-g-MAH对聚丙烯/木粉复合材料性能的影响

在转矩流变仪中用熔融接枝法制备马来酸酐(MAH)和苯乙烯(St)接枝聚丙烯（PP）-PP-g-(MAH/St)和PP-g-MAH,将其作为聚丙烯/木粉复合材料的相容剂。 FTIR证实MAH和St单体与PP发生接枝反应。 用SEM和DSC等手段考察两种相容剂对PP/木粉复合材料微观形貌和结晶性能的影响,探索了各种PP/木粉复合材料加工和力学性能不同的内在原因。 SEM显示,PP-g-(MAH/St)改性木粉比PP-g-MAH改性木粉在PP基体中分散性更佳,木粉与PP的界面更加模糊,相容性进一步改善。 DSC结果表明,PP-g-(MAH/St)改性体系可增强木粉对PP的异相成核作用,提高结晶温度和结晶度。 复合材料的加工和力学性能测试结果表明,PP-g-(MAH/St)改性效果明显优于PP-g-MAH。 复合材料的熔体质量流动速率随相容剂用量的增加而逐步下降,PP-g-(MAH/St)改性体系拉伸强度和弯曲强度却逐步上升,并在相容剂用量为4.8 g/100 g PP时达到极值。 此时其拉伸强度达40.62 MPa,分别是未改性体系和PP-g-MAH改性体系的1.29和1.17倍;其弯曲强度达45.72 MPa,分别是未改性体系和PP-g-MAH改性体系的1.23和1.59倍;而无缺口冲击强度却在相容剂用量为3.6 g/100 g PP时达到极值13.35 kJ/m2,分别是未改性体系和PP-g-MAH改性体系的1.62倍和1.42倍。     

Synergistic effect of organophilic Fe-montmorillonite on flammability in polypropylene/intumescent flame retardant system

Polypropylene/intumescent flame retardant/organophilic Fe-montmorillonite (PP/IFR/Fe-OMT) nanocomposites were prepared by melting intercalation. In order to investigate the effect of structural Fe³⁺ in the PP/IFR system, the corresponding PP/IFR and PP/IFR/Na-OMT composites were prepared under the same conditions. The thermo-gravimetric analysis data show that the PP/IFR/Fe-OMT nanocomposites have higher thermal stability than the PP/IFR and PP/IFR/Na-OMT composites. The flame retardant results indicate that the limiting oxygen index values of the nanocomposites with Fe-OMT are basically higher than those of the pure PP and the composites containing IFR or Na-OMT/IFR. And the addition of a suitable amount of Fe-OMT in PP/IFR composites can apparently favor UL94 test, and no dripping phenomenon was found. The cone calorimeter test indicates that the heat release rate (HRR) is significantly reduced by the formation of the nanocomposites, and the HRR of the PP/IFR/Fe-OMT nanocomposites are decreased in comparison with those of the PP/IFR/Na-OMT nanocomposites. It is noteworthy that Fe-OMT is helpful to smoke suppression by smoke density test.     

Effect of a novel charring-foaming agent on flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A new triazine polymer was synthesized by using cyanuric chloride, ethanolamine and ethylenediamine as raw materials. It is used both as a charring agent and as a foaming agent in intumescent flame retardants, designated as charring-foaming agent (CFA). Effect of CFA on flame retardancy, thermal degradation and mechanical properties of intumescent flame retardant polypropylene (PP) system (IFR-PP system) has been investigated. The results demonstrated that the intumescent flame retardant (IFR) consisting of CFA, APP and Zeolite 4A is very effective in flame retardancy of PP. It was found that when the weight ratio of CFA to APP is 1:2, that is, the components of the IFR are 64 wt% APP, 32 wt% CFA and 4 wt% Zeolite 4A, the IFR presents the most effective flame retardancy in PP systems. LOI value of IFR-PP reaches 37.0, when the IFR loading is 25 wt% in PP. It was also found that when the IFR loading is only 18 wt% in PP, the flame retardancy of IFR-PP can still pass V-0 rating, and its LOI value reaches 30.2. TGA data obtained in pure nitrogen demonstrated that CFA has a good ability of char formation itself, and CFA shows a high initial temperature of the thermal degradation. The char residue of CFA can reach 35.7 wt% at 700 °C. APP could effectively promote the char formation of the APP-CFA system. The char residue reaches 39.7 wt% at 700 °C, while it is 19.5% based on calculation. The IFR can change the thermal degradation behaviour of PP, enhance T_max of the decomposition peak of PP, and promote PP to form char, based upon the results of the calculation and the experiment. This is attributed to the fact that endothermic reactions took place in IFR charring process and the char layer formed by IFR prevented heat from transferring into inside of IFR-PP system. TGA results further explained the effective flame retardancy of the IFR containing CFA.     

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.     

Synergistic effect of nanoflaky manganese phosphate on thermal degradation and flame retardant properties of intumescent flame retardant polypropylene system

Nanoflaky manganese phosphate (NMP) was synthesized from manganese nitrate and trisodium phosphate dodecahydrate, and used as a synergistic agent on the flame retardancy of polypropylene (PP)/intumescent flame retardant (IFR) system. The thermogravimetric analysis (TGA), real time Fourier-transform infrared (RTFTIR) spectroscopy measurements, cone calorimeter (CONE) and microscale combustion calorimeter (MCC) were used to evaluate the synergistic effects of NMP on PP/IFR system. When IFR + NMP was fixed at 20 wt% in flame retardant PP system, the TGA tests showed that NMP could enhance the thermal stability of PP/IFR system at initial temperature from about room temperature to 440 °C and effectively increase the char residue formation. The RTFTIR results revealed that NMP could clearly change the decomposition behavior of PP in PP/IFR system, which promotes decomposition at the initial temperature from about room temperature to 260 °C and forms more effective barrier layer to protect PP from decomposing at high temperature from about 260 °C to 500 °C. The CONE tests indicated that the addition of NMP in PP/IFR system not only reduced the peak heat release rate (HRR), but also prolonged the ignition time. The MCC results revealed that PP/IFR/NMP system generated less combustion heat over the course of heating than that of PP/IFR system. And scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to explore the char residues of the PP/IFR systems with and without NMP.     

The role of graphene interactions and geometry on thermal and electrical properties of epoxy nanocomposites: A theoretical to experimental approach

The influence of dispersion procedure and nanofiller geometry on thermal and electrical properties of graphene nanoplatelet (GNP) based composites has been investigated. A theoretical model, based on the contacts between adjacent nanoparticles, has been proposed aiming to connect thermal and electrical properties. It has been observed that GNP overlapping (type I) induces a decrease on thermal conductivity. Its effect on electrical conductivity is more complex and depends on the areas of overlap and in-plane contacts (type II). A higher type I area in comparison to type II implies an increase of electrical conductivity with overlapping whereas the opposite effect is found when type II area is higher than type I. The predicted results of the theoretical model fitted experimental measurements at different GNP contents and three roll milling processing conditions, giving a better overview of the influence of GNP geometry and interactions on electrical and thermal properties of nanocomposites.