【作者】 吴昆；

【导师】 胡源； 王正洲； Baljinder Kandola；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2009， 博士

【摘要】 为解决膨胀型阻燃剂（IFR）在实际应用中存在的添加量相对较大、和聚合物相容性差、耐水性差、易团聚、在聚合物制品中易渗出以及在加工过程中酸源与炭源易反应等问题,本论文将微胶囊概念和膨胀阻燃技术相结合,选用适当的微胶囊技术与囊材对IFR组分之一聚磷酸铵（APP）进行包裹改性,制备核-壳结构膨胀型阻燃剂,可有效减小阻燃剂吸湿性,增加与基体的相容性,明显提高阻燃复合材料耐水与阻燃性能。本论文研究工作主要涉及以下几个方面:1.选用三聚氰胺-甲醛（MF）树脂为囊材,采用分段升温的新方法,运用原位聚合微胶囊化技术,得到包裹完全、分散性更好的核-壳结构APP（MFAPP）。MFAPP的溶解度降低,MFAPP颗粒相对APP而言具有更好的分散性与更小的粒径。微胶囊化可显著改善APP在聚丙烯（PP）中的分散性以及PP/APP阻燃体系的耐水性。PP/MFAPP复合材料的氧指数高于PP/APP;但由于缺少炭源,PP/MFAPP仍达不到任何阻燃级别。引入炭源季戊四醇（PER）,发现PP/MFAPP/PER的氧指数增加,且大部分体系都达到了V-0级。锥形量热计的结果表明PP/MFAPP与PP/MFAPP/PER阻燃体系在燃烧过程中,可形成有效炭层覆盖在材料表面,降低复合材料的热释放速率,阻止材料的进一步燃烧。2.选择以尿素-三聚氰胺-甲醛（UMF）树脂为囊材来微胶囊化APP。一方面,三聚氰胺（MEL）用于改善UF树脂的耐水性;另一方面,尿素-甲醛（UF）树脂有利于成炭,形成具有较好阻隔性能的保护炭层。虽然PPA/UMFAPP的氧指数较高,但仍然无法通过任何垂直燃烧级别。选择耐水性相对较好的双季戊四醇（DPER）作为炭源制备PP/UMFAPP/DPER三元阻燃复合体系,发现三元阻燃复合体系不仅氧指数有所提高,而且可以达到V-0级。在50℃的热水中浸泡24小时后,PP/UMFAPP/DPER的垂直燃烧级别仍保持的很好。UMFAPP/DPER是一种相比传统APP基膨胀阻燃体系具有更佳耐水与阻燃性能的阻燃体系。3.首先选用UF树脂作为第一层囊材包裹APP,然后将MF树脂再包裹在外层。双层壳壁既可以作为保护层提高囊芯的耐水性,又可以作为炭源（UF）、气源（MF）与囊芯（APP,可作为酸源）起到阻燃协效作用。相比APP,MUFAPP不仅降低了水溶性,而且提高了PP阻燃复合材料的阻燃与耐水性能。相比PP/APP,不仅PP/MUFAPP复合材料的氧指数得到了很大的提高,且当MUFAPP的添加量为40%时,PP/MUFAPP可通过V-0级;经过热水处理后,MUFAPP膨胀阻燃体系在PP中的阻燃性能仍保持的很好。在燃烧过程中MUFAPP会降解成炭,在聚合物表面形成耐热、隔热、隔氧的保护层,从而阻止火焰的蔓延与扩展,降低材料的热释放。4.虽然双季戊四醇（DPER）的添加可以进一步提高阻燃复合材料的阻燃性能,但由于DPER也具有一定的水溶性,阻燃复合材料的耐水性同时亦会遭到削弱。选用MF树脂同时微胶囊化APP与DPER（M（A&D））,以同时提高酸源（APP）与炭源（DPER）在聚合物中的相容性与耐水性。另一方面,MF树脂可作为气源与酸源、炭源起到阻燃协效,从而进一步提高APP/DPER在聚合物中的阻燃性能。相比APP/DPER,M（A&D）不仅降低了水溶性,具有更好的分散性与更小的粒径,而且提高了PP阻燃复合材料的阻燃与耐水性能。在30%的添加量下,PP/ M（A&D）的氧指数达到了34.0%,可通过V-0级;而PP/APP/DPER的氧指数为28.5%,仅可通过V-1级。热水浸泡处理后,PP/ M（A&D）体系的氧指数变化较小,且阻燃级别没有变化（V-0）。5.为了解决上述微胶囊化APP中缺少炭源（MFAPP,UMFAPP）或炭源成炭效率（MUFAPP）一般的问题,在本部分,首先制备多羟基大分子化合物（PVA或淀粉）改性的MF预聚体,然后微胶囊包裹APP。此集酸源、炭源、气源于一体的核-壳结构膨胀型阻燃剂相比传统的APP基膨胀阻燃体系具有更好的阻燃与耐水性能。相比APP,VMFAPP或SMFAPP不仅水溶性降低,而且提高了PP阻燃复合材料的阻燃与耐水性能。不仅PP/VMFAPP和PP/SMFAPP的氧指数得到了提高,且当阻燃剂的添加量为30%时,可通过V-0级。经过50℃热水24小时浸泡后,PP/VMFAPP和PP/SMFAPP体系的阻燃级别仍为V-0。锥形量热计实验结果也证明VMFAPP和SMFAPP相比APP在PP中的阻燃效率更高。探讨了阻燃机理:燃烧时,VMFAPP和SMFAPP的囊芯会释放出酸,催化囊材成炭,在凝聚相中可以形成稳定、膨胀炭层,阻碍热传递与氧气交换,抑制底部材料的热降解,从而起到阻燃的作用。6.选用微胶囊化聚磷酸铵（MFAPP）作为阻燃剂膨胀阻燃热塑性淀粉基可降解材料（TPS）。一方面,MFAPP中的APP与MF树脂可以充当酸源和气源,含有大量羟基的TPS基体可以直接作为炭源使用;另一方面,阻燃剂核-壳结构中囊材的存在可以有效的阻止酸源与炭源（淀粉、PVA、丙三醇等）在加工过程中发生的不良反应。当MFAPP的添加量为2%时,TPS/MFAPP就可以通过垂直燃烧测试的V-0级,此时材料的LOI高达31.0%;而TPS的氧指数仅为23.0%,无法通过UL-94测试任何级别。TG结果表明囊材的存在可以有效的阻止酸源（APP）与炭源（淀粉、PVA、丙三醇等）在加工过程中发生的不良反应。TPS的热裂解产物主要为水蒸汽,甲醇,碳氢化合物,CO₂,CO和甲醛等:而MFAPP催化了TPS的降解,在降解初期释放更多的不燃性气体。揭示了MFAPP在TPS中的阻燃机理:在燃烧初期囊材破裂,MFAPP放出酸,催化了TPS的降解,同时释放大量不燃性气体,从而形成膨胀、保护炭层。更多还原

【Abstract】 Ammonium polyphosphate(APP),a well known component of the intumescent flame retardant(IFR) systems is easily attacked by moisture,migrates to the surface and leads to a decrease in the properties of the polymer composites,not only flame retardancy,but also some other properties.To deal with the problems of the moisture absorption and poor compatibility with polymers,microencapsulation with water-insoluble polymers is a good choice.The research work of this dissertation is composed of the following parts:1.Microencapsulated ammonium polyphosphate(MFAPP) with a melamine-formaldehyde(MF) resin coating layer is prepared by in situ polymerization.MFAPP is characterized by Fourier transform infrared(FTIR),X-ray photoelectron spectroscopy(XPS),etc.The results show that the microencapsulation with the MF resin leads to a decrease in the particles’ size and water absorption.The flame retardant action and mechanism of MFAPP and APP in polypropylene(PP) are studied using limiting oxygen index(LOI) and UL 94 test,and their thermal stability is evaluated by thermogravimetric analysis(TG).The LOI value of the PP/MFAPP composite at 30 wt%loading is 30.5%,whereas the corresponding value of the PP/APP composite is only 20.0%.Moreover,the PP/MFAPP/PER composites with suitable ratios of MFAPP to pentaerythritol(PER) can reach the V-0 rating in UL-94 test.2.Since the water resistance of the urea-formaldehyde(UF) resin is weak compared with the MF resin and melamine can be used as a blowing agent to improve the flame retardant efficiency of the IFR system,the microencapsulated APP (UMFAPP) with a urea-melamine-formaldehyde(UMF) resin was prepared in this work by in situ polymerization.The microencapsulation of APP with the UMF resin leads to a decrease in the particle’s water solubility.The flame retardant action of UMFAPP and APP in PP are studied using LOI and UL 94 test,and their thermal stability is evaluated by thermogravimetric analysis.It is found that the LOI value of the PP/UMFAPP composite is higher than the value of the PP/APP composite.In comparison with the PP/UMFAPP composites,the LOI values of the PP/UMFAPP/DPER composites at the same additive loading increase,and UL-94 ratings of most composites are raised to V-0.The water resistant properties of the PP composites containing APP and UMFAPP are studied.Moreover,the combustion behavior of the PP composites is investigated by the cone calorimeter.Above results show that UMFAPP/DPER is a novel IFR system which has better water resistance and flame retardance compared with traditional APP based IFR system.3.We microencapsulated APP with UF resin as primary layer,and then coated the particles with MF resin compactly.The double shell outside APP particles can be used as a protective layer and carbonization or blowing agent synchronously. Microencapsulated ammonium polyphosphate(MUFAPP) with a double shell is characterized by FTIR,XPS and SEM,etc.The microencapsulation of APP can increase its flame retardance and water resistance in PP.The flame retardant action of MUFAPP and APP in PP are studied using LOI and UL-94 test,and their thermal stability is evaluated by TG.The LOI value of the PP/MUFAPP composite at the same loading is higher than that of PP/APP composite,and the UL-94 rating of PP/MUFAPP can pass V-0 at 40 wt%loading.The results of the cone calorimeter also indicate that MUFAPP is an effective flame retardant in PP.The thermal degradation behaviors of APP and MUFAPP are studied using TG and dynamic FTIR,and their flame retardant mechanisms in PP are explained.4.Due to the comparatively weak water resistance of dipentaerythritol(DPER), co-microencapsulated ammonium polyphosphate and dipentaerythritol(M(A&D)) is prepared using a melamine-formaldehyde(MF) resin by in situ polymerization method.The co-microencapsulation of APP and DPER leads to a great improvement in water solubility of the additives.The flame retardant effect of M(A&D) in PP is evaluated using limiting oxygen index(LOI) and UL 94 test,and the water resistance of the PP/M(A&D) composites is also studied.The flame retardant properties and water resistance of the PP/M(A&D) composites are much better than the ones of the PP/APP/DPER composites.Moreover,the thermal stability of the PP/M(A&D) composites is improved compared with the PP/APP/DPER composites. 5.With a shell of PVA-melamine-formaldehyde(VMF) or starch-melamine-formaldehyde (SMF) resin,core/shell-like ammonium polyphosphate(VMFAPP or SMFAPP) is prepared by in situ polymerization,and is characterized by SEM,FTIR and XPS.This core/shell-like intumescent flame retardant contains three components of a typical IFR system:APP(as an acid source),PVA/starch(as a carbonization agent) and melamine(as a blowing agent).The results show that shell leads VMFAPP and SMFAPP a high water resistance and flame retardance compared with APP in PP.UL 94 ratings of PP/VMFAPP and PP/SMFAPP can reach V-0 at 30 wt%loading.The flame retardant mechanism of VMFAPP and SMFAPP is studied by dynamic FTIR, TG and cone calorimeter,etc.6.Biodegradable PVA/glycerol-plasticized thermoplastic starch(TPS) and its intumescent flame retarded composites are prepared.Microencapsulated ammonium polyphosphate(MFAPP) was used not only in order to utilize the charring capacity of the polyhydric compounds in TPS,but also restrain the reaction between APP and starch during processing.The flame retardancy and thermal stability of TPS and TPS/MFAPP were characterized by LOI,UL-94,TG,Microscale Combustion Calorimeter(MCC),etc.TPS/MFAPP composites with only 2 wt%MFAPP can pass V-0 in UL-94 test.However,neat TPS can’t pass any rating.The presence of MFAPP can reduce the total heat release of TPS sharply in MCC test.The thermal degradation and gas products of TPS and TPS/MFAPP were monitored by TG-FTIR and dynamic FTIR.XPS and SEM measurements were utilized to investigate the chemical structure, as well as the surface morphology of the residual char.更多还原