EFFECTS OF COUPLING AGENTS ON THE CRYSTALLIZATION BEHAVIOR OF PP/T-ZnOw COMPOSITES

The objectives of this paper are to understand the crystallization behavior of polypropylene(PP)composites with surface modified tetra-needle-shaped zinc oxide whisker(T-ZnOw).T-ZnOw was surface modified with different coupling agents,such as silane coupling agents(KH-550,KH-560)and titanate coupling agent(NDZ-105),in order to improve the compatibility between PP and T-ZnOw.DSC and POM were used to characterize the melt and crystallization behavior and the crystalline structures of the composites,respectively.The results show that the surface modified T-ZnOw acts as a nucleating agent of PP crystallization,depending on the coupling agent used for modification.KH-550 and KH-560 have more apparent role in improving the interfacial interaction than NDZ-105 and induce PP crystallization at higher temperature and with smaller spherulites size.The results also suggest that the crystallization behavior depends on not only the content of coupling agent,but also the content of the surface modified T-ZnOw used in the composites.     

Influence of surface modification of fillers and polymer on flammability and tensile behaviour of polypropylene-composites

An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and natural zeolite (clinoptilolite, Gördes II) as a synergistic agent was used in this study to enhance flame retardancy of polypropylene (FR-PP). Zeolite was incorporated into flame retardant formulation at four different concentrations (1, 2, 5, and 10 wt%) to investigate synergism with the flame retardant materials. Filler content was fixed at 30 wt% of total amounts of flame retardant PP composites. Zeolite and APP were treated with two different coupling agents namely, 3-(trimethoxysilyl)-1-propanethiol and (3-aminopropyl)-triethoxysilane for investigation of the influence of surface treatments on mechanical properties and flame retardant performance of composites. Maleic anhydride grafted polypropylene (MAPP) was used for making polypropylene hydrophilic. Flammability of FR-PP composites was measured by the determination of limiting oxygen index (LOI). The LOI values reached to a maximum value of 41% for mercapto silane treated APP:PER (2:1) PP composite containing 5 wt% zeolite. The tensile strength of composites was increased by the addition of MAPP and elongation at break of composites was increased with silane treatments.     

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.     

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.     

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.     

Synthesis of a triazine-based macromolecular hybrid charring agent containing zinc borate and its flame retardancy and thermal properties in polypropylene

Abstract

A triazine-based macromolecular hybrid charring agent containing zinc borate (MCA-K-ZB) was synthesized and combined with ammonium polyphosphate (APP) to improve the flame retardancy of polypropylene (PP). The flame retardancy and thermal properties of PP composites were investigated using limited oxygen index, vertical burning test, and thermogravimetric analysis. The results showed APP/MCA-K-ZB can improve the flame retardancy of PP compared with APP/MCA-K/ZB. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The SEM result shows that MCA-K-ZB can improve the compactness and continuity of char residue compared with MCA-K/ZB, therefore improving the flame retardancy of PP composites.     

Preparation of 3‐aminopropyltriethoxy silane modified cellulose microcrystalline and their applications as flame retardant and reinforcing agents in epoxy resin

Cellulose microcrystalline (CMC), a linear polysaccharide with glucosidic bond, was successfully extracted from bamboo powder and modified by 3‐aminopropyltriethoxy silane coupling agent (KH550) to prepare KH550‐CMC. The prepared KH550‐CMC, in association with ammonium polyphosphate (APP), was introduced into epoxy resin (EP) by casting process to obtain flame retardant composites. The fire performance evaluation indicated that the presence of 10‐phr APP and 5‐phr KH550‐CMC in EP achieved the maximal LOI value of 28.9%, passed the UL‐94 V‐0 rating, and significantly decreased the peak heat release rate from 1055 kW/m² of neat EP to 286 kW/m². The improved fire performance is due to the improvement of dispersity of CMC in EP matrix and formation of better char layer, thus protecting the matrix effectively. Moreover, the introduction of KH550‐CMC could also partly eliminate the negative influence of flame retardants on the mechanical properties of EP composites due to the strengthening effect of CMC and better interfacial compatibility after modification with KH550.     

中空多壳层TiO2填充对环氧树脂复合材料力学性能的影响

为改善环氧树脂(EP)材料的力学性能, 采用次序模板法合成了TiO₂中空多壳层结构(HoMS)材料, 利用偶联剂对获得的TiO₂ HoMSs进行接枝改性后填充到EP中, 制备了TiO₂ HoMSs/EP复合材料; 并与单壳层TiO₂中空结构进行比较, 研究了壳层数和偶联剂改性对复合材料力学性能的影响规律. 结果表明, 随着壳层数的增加, 复合材料的力学性能增强, 并且偶联剂改性的TiO₂ HoMSs可进一步提高复合材料的力学性能. 在该体系中, 经硅烷偶联剂KH-560改性后的三壳层TiO₂ HoMSs(3S-TiO₂ HoMSs)/EP复合材料的拉伸强度、 断裂伸长率和冲击强度可分别达到71.66 MPa, 7.4%和35.81 kJ/m². 扫描电子显微镜(SEM)断面形貌表征结果显示, 相较于纯EP材料, TiO₂ HoMSs/EP复合材料的断面更加粗糙, 说明TiO₂ HoMSs材料起到了吸收外界应力和阻碍裂纹扩展的作用, 提高了复合材料的韧性, 提升了复合材料的冲击性能.     

Microencapsulated Ammonium Polyphosphate with Polyurethane Shell: Application to Flame Retarded Polypropylene/Ethylene-propylene Diene Terpolymer Blends

Microencapsulated ammonium polyphosphate with polyurethane resin (PUMAPP) was prepared by in situ polymerization and characterized by X-ray photoelectron spectroscopy (XPS). The flame retardation of PUMAPP/dipentaerythritol(DPER) and ammonium polyphosphate (APP)/DPER flame retarded polypropylene (PP)/ethylene propylene diene rubber (EPDM) composites were studied using limiting oxygen index (LOI), UL-94 test and cone calorimeter. Results demonstrated that the flame retardancy of the PP/EPDM/PUMAPP/DPER composites was better than that of the PP/EPDM/APP/DPER composites at the same additive loading. Real time Fourier transform infrared (FTIR) and thermogravimetric analysis (TG) were used to study the thermal degradation and stability of the PP/EPDM/PUMAPP/DPER composite. The hydrolytic stability of the flame retarded PP/EPDM composites was studied. It was found that the microencapsulation of APP with the PU resin leaded to a decrease in the particle's water solubility. Moreover, the synergistic effect of vinyltrimethoxysilane (VTMS) on the PP/EPDM/PUMAPP/DPER composite was also investigated.     

Water resistance,thermal stability,and flame retardation of polypropylene composites containing a novel ammonium polyphosphate microencapsulated by UV‐curable epoxy acrylate resin

In this work, ammonium polyphosphate (APP) was microencapsulated by UV‐curable epoxy acrylate (EA) resin. The resulting novel EA‐microencapsulated APP (EA‐APP) was characterized by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, granulometry, and thermogravimetric (TG) analysis. EA‐APP was used to flame retard polypropylene (PP). The water solubility of EA‐APP and the water resistance of PP/EA‐APP systems were investigated. The thermal stability and combustion behaviors of PP/EA‐APP composites were studied through TG and cone calorimeter (CC) tests, respectively. The water resistance test showed that the EA shell could significantly improve the water resistance of PP/APP. TG data illustrated that the char residue of EA‐APP greatly increased by 149% compared with uncoated APP, and the thermal stability of PP/EA‐APP composite was improved because of the microencapsulation of APP, with an increment of 248% for the char residue compared with PP/APP. CC test results indicated that the peak value of heat release rate, the total heat release, and the peak of smoke production rate of PP/EA‐APP decreased in comparison with PP/APP. The mechanism for the improvement of flame retardancy in CC test was discussed based on the experimental results. EA resin containing a large number of hydroxyl groups might promote the dehydration reaction in EA‐APP, which facilitated the formation of char residue and the stabilization of APP. Consequently, the flame‐retardant efficiency for APP was improved because of the presence of EA shell. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous improvement in the flame retardancy and water resistance of PP/APP through coating UV-curable pentaerythritol triacrylate onto APP

To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate(APP), the UV-curable pentaerythritol triacrylate(PETA) was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP(PETA-APP) was characterized by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), and thermogravimetric(TG) analysis. PETA-APP was used as intumescent flame retardant(IFR) alone to flame retard polypropylene(PP). The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index(LOI), vertical burning test(UL-94) and cone calorimeter(CC) test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate(HRR), mass loss rate(MLR) and smoke production rate(SPR) of PP/PETAAPP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy(XPS) tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.     

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.     

Effect of Organo‐Modified Nanosepiolite on Fire Behaviors and Mechanical Performance of Polypropylene Composites

The objective of the study was to investigate the effect of the organo‐modified nanosepiolite (ONSep) on improving the fire safety of polypropylene (PP). The composites based on PP, flame retardant master batch (MB‐FR, 25 wt% PP+50 wt% decabromodiphenyl ether (DBDPE)+25% antimony trioxide (ATO)) and ONSep were prepared via melt blending. The results of the limiting oxygen index (LOI) and vertical burning rating (UL‐94) test indicated that PP/40 wt% MB composites had no rating with seriously dripping phenomenon, while the LOI value was only 22.5. However, as 4 wt% ONSep was added in PP/40 wt% MB composites, the composites achieved UL94 V‐0 rating and the LOI value was 24.3. In comparison, PP/50 wt% MB composites could not reach the V‐0 rating either. The TGA results revealed that the addition of ONSep enhanced the thermal stability of the PP/MB‐FR composites. The cone calorimeter results indicated that the heat release rate, average mass loss rate, smoke production rate and smoke temperature of the PP/40 wt% MB‐FR/4 wt% ONSep composites decreased in comparison with those of PP/40 wt% MB‐FR composites. Simultaneously, the Young modulus and impact strength were also much better improved with the increase of ONSep loading. Therefore, the synergistic flame retardancy of ONSep in PP/MB‐FR matrix significantly containing a halogen based flame retardant (DBDPE) significantly improved the fire safety and mechanical properties of the composites, and allowed to decrease the total amount of brominated fire retardants.     

Great enhancement of efficiency of intumescent flame retardants by titanate coupling agent and polysiloxane

Modified intumescent flame retardants (MIFRs) and polysiloxane (APID) have been used in combination to enhance the flame retardancy of polypropylene (PP). The IFR system was composed of melamine (MEL), ammonium polyphosphate (APP) and pentaerythritol (PER). Aimed to improve the thermal stability of the IFR and its dispersivity in PP, titanate coupling agent NDZ‐201 was used to modify the IFRs via ball milling. MIFRs and APID have a cooperative effect on the flame retardant properties of PP. With 25 wt.% of MIFR and APID, the flame retardant sample (PPMA) was rated V0 for UL‐94, the LOI value was 34.3%, and the peak heat release rate (PHRR) was reduced by 80% in cone calorimeter test. In addition, APID could improve the compatibility of MIFR with the PP matrix, thereby increasing the mechanical properties of PP blends. The flame retardant effect of APID and MIFR in PP was presented in the condensed phase resulting in a rigid, thermally stable and expanded carbon layer due to different char structures.     

Supramolecular self‐assembly modification of ammonium polyphosphate and its flame retardant application in polypropylene

In order to improve its water resistance and compatibility with polymer matrix, ammonium polyphosphate (APP) is modified with melamine‐trimesic acid (MEL‐TA) aggregates by supramolecular self‐assembly technology. Chemical structure and morphology of APP@MEL‐TA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM), respectively. Intumescent flame retardant system of APP@MEL‐TA and charring‐foaming agent is introduced into polypropylene (PP) matrix. The flammability and combustion behavior of PP composites are investigated by limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests. In terms of LOI values and cone combustion results, APP@MEL‐TA performs better than pristine APP. Char residue of PP composites is investigated by SEM and Raman spectra. Flame retardant mechanisms are proposed based on thermal decomposition, combustion results, and analysis on char residue.     

A method for simultaneously improving the flame retardancy and toughness of PLA

In order to modify the brittleness and flame retardant properties of poly(lactic acid) (PLA), a series of flame retardant toughened PLA composites were prepared using poly(ethylene glycol) 6000 (PEG6000) as a toughening and charring agent together with ammonium polyphosphate (APP) as an acid source and blowing agent. The fire and thermal behavior of PLA/PEG/APP composites was evaluated by limiting oxygen index (LOI), UL‐94, cone calorimeter, and thermogravimetric analysis (TGA). The results showed that the PLA/PEG/APP system had good charring ability and could improve the flame retardancy of PLA. When the content of APP in the composites was more than 5 wt%, all samples could reach UL‐94 V‐0 rating. The results of mechanical property tests demonstrated that the brittleness of PLA was also improved after blended with PEG6000. All the PLA/PEG/APP composites with an APP content of less than 10 wt% showed an obvious neck and fracture behavior, that is, the tensile behavior of PLA was changed from brittle to ductile. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic effects of β‐cyclodextrin containing silicone oligomer on intumescent flame retardant polypropylene system

The effects of β‐cyclodextrin containing silicone oligomer(CDS), as a synergistic agent, on the flame retardancy and mechanical properties of intumescent flame retardant polypropylene composites were studied by adding different amounts of CDS in intumescent flame retardants. The limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to evaluate the synergistic effects of CDS in the composites. It was found that after a little amount of CDS partially replaced a charring‐foaming agent (CFA) in IFR, LOI values of the composites were enhanced and they obtained a UL‐94 V‐0 rating. IFR system containing 6.25wt% CDS presented the best flame retardancy in PP. The experimental results obtained from LOI and UL‐94, TGA, SEM, and mechanical properties indicated that the combination of CDS and CFA presents synergistic effects in flame retardancy, char formation, and mechanical properties of the composites. This is probably due to different structures of polyhydroxyl macromolecules (CDS and CFA), the existence of dimethyl silicone group in CDS, and the toughness of epoxy silicon chain in CDS. SEM results proved that the interfacial compatibility between IFR and PP was improved by CDS. Copyright © 2009 John Wiley & Sons, Ltd.     

金属氧化物对聚丙烯膨胀阻燃体系阻燃性能的影响

将Bi2O3、Sb2O3、SnO2添加到聚磷酸铵(APP)和双季戊四醇(DPER)膨胀型阻燃聚丙烯(PP)体系中,采用氧指数(OI)、热分析(TGA)、热红联用(TG-FTIR)和扫描电镜(SEM),考察它们对膨胀阻燃体系的催化协效作用,探讨其作用机理.结果表明,3种金属氧化物在适量的添加下都可以提高体系的氧指数.TG结果表明,Bi2O3的加入可以提高膨胀炭层在高温时的热稳定性,增加高温时残余物的量;TG-FTIR结果显示添加Bi2O3后,膨胀阻燃剂在热分解过程中,气体的释放过程发生了改变.膨胀炭层的SEM图表明,Bi2O3可以改善膨胀炭层的形貌,提高炭层的隔热隔质性能.0.1 wt%的Bi2O3和1 wt%的纳米黏土复配用于膨胀阻燃体系中,可以在阻燃剂添加20份下,样品氧指数达到28.3;在阻燃剂添加25时,样品(3.2 mm)通过UL-94 V-0级.0.1 wt%的Bi2O3和1 wt%纳黏粘土的添加,还可以提高体系的力学性能.     

静电纺丝制备SiO2短纤维对聚丙烯冲击性能的影响

采用静电纺丝技术, 结合正硅酸乙酯(TEOS)的溶胶-凝胶反应制备出了直径为500 nm的SiO2短纤维(n-SF). 纤维经过硅烷偶联剂KH570表面处理后, 与聚丙烯(PP)通过螺杆混合制得复合材料. 通过SEM观察, KH570处理过的SiO2短纤维(n-MSF)在PP基体中分散均匀, 界面结合良好. DSC和XRD测试结果表明, n-SF和n-MSF的加入均可提高PP的结晶速率, 同时改变PP中β晶含量, 进而影响冲击强度; 冲击实验结果表明, n-MSF添加量为3%(质量分数)时, 复合材料冲击性能比纯PP提高了40.3%.     

CaSO_4晶须补强增韧聚氨酯弹性体机理的研究

提高聚氨酯弹性体的力学性能是聚氨酯研究领域里普遍关心的课题之一,一般采用刚性粒子和纤维类无机填料增强聚氨酯弹性体,但上述填料在提高强度的同时,会导致韧性降低,空易造成脆性断裂,因此填料能否同时补强增韧聚氨酯弹性体具有重要的实际应用价值,晶须是一种单晶纤维状材料,其直径极小,几乎不存在任何缺陷,由于内在的完整性,高度有序的原子排列,使其强度接近晶体理论－－原子间价键的强度,晶须凭借微细的直径、较短的长度、极高的强度,成为一种新型补强增韧剂,目前晶须的复合基体多为陶瓷基、金属基和树脂基,有关复合基体多为陶瓷基、金属基和树脂基,有关复合聚氨酯弹性体的理论及应用研究报道很少,本文制备了具有较高强度和韧性的CaSO4晶须／聚氨酯弹性体复合材料,通过微观分析揭示了CaSO4晶须对聚氨酯弹性体补强增韧的机理,并对其影响因素进行了讨论。