微胶囊Mg (OH)2的合成及其对乙烯-乙酸乙烯酯共聚物的阻燃作用

用原位聚合方法合成了以微米Mg（OH）₂粒子为芯材、交联聚脲为壁材的微胶囊Mg（OH）₂（M-Mg（OH）₂）阻燃剂,并把M-Mg（OH）₂加入到乙烯-乙酸乙烯酯共聚物（EVA）中,研究了M-Mg（OH）₂对EVA的阻燃作用。采用FTIR、SEM、热分析和酸滴定方法研究了M-Mg（OH）₂的性质,用极限氧指数（LOI）和垂直燃烧方法（UL-94）研究了M-Mg（OH）₂/EVA复合材料的阻燃性能以及酸腐蚀对M-Mg（OH）₂/EVA复合材料阻燃性能的影响。结果表明,采用原位聚合方法能够成功地在Mg（OH）₂粒子表面包覆交联聚脲壁材,得到M-Mg（OH）₂。与纯Mg（OH）₂相比,M-Mg（OH）₂的颗粒尺寸增大,热稳定性增加,在水中溶解度显著降低,在EVA基体中分散更加均匀。阻燃剂用量相同时,M-Mg（OH）₂/EVA复合材料的LOI总是比Mg（OH）₂/EVA复合材料的数值稍大。阻燃剂与EVA质量比小于135∶100时,两种复合材料的垂直燃烧级别均为V-2级,阻燃剂与EVA质量比在135∶100~150∶100之间时,前者的燃烧级别为V-0级,而后者只能达到V-2级,阻燃剂与EVA质量比超过150∶100时,两种复合材料都能达到V-0级。M-Mg（OH）₂/EVA复合材料的耐酸性比Mg（OH）₂/EVA大幅度提高,可以在酸性环境中使用。     

环交联聚磷腈包覆羟基锡酸锶杂化纳米棒的合成及阻燃环氧树脂研究

为了开发新型无机-有机杂化的阻燃消烟剂, 本研究采用共沉淀法合成了棒状纳米羟基锡酸锶(SrSn(OH)₆), 并用环交联聚磷腈(PZS)对其进行包覆, 得到一种核壳结构的有机无机杂化纳米阻燃剂(PZS@SrSn(OH)₆)。通过扫描电镜、透射电镜和红外光谱研究了PZS@SrSn(OH)₆的微观形貌和化学结构。通过热重分析研究了PZS@SrSn(OH)₆及EP/PZS@SrSn(OH)₆阻燃复合材料的热降解行为。采用极限氧指数和锥形量热对复合材料阻燃性能进行测试, 用X射线衍射、扫描电镜、能谱分析及红外光谱对EP/PZS@SrSn(OH)₆的阻燃机理进行分析。结果表明PZS@SrSn(OH)₆在环氧树脂中展现出高阻燃效率和抑烟效果, 且PZS与SrSn(OH)₆之间存在显著的协同阻燃效应。与纯环氧树脂相比, 仅添加3wt%的PZS@SrSn(OH)₆时, 极限氧指数(LOI)值从26.2%增加到29.6%。锥形量热结果表明热释放速率峰值降低了约29%, 烟释放速率峰值降低了约37%, 残炭率提高了242%。PZS@SrSn(OH)₆在高温下形成致密结构炭层, 隔绝分解产物及热量和氧气交换, 从而显著提高环氧树脂的阻燃效果。     

碳纳米管包裹聚磷酸铵协同Mg(OH)2构筑乙烯-醋酸乙烯酯共聚物复合材料及其火安全性能

本文采用微胶囊法制备了具有多层次结构的碳纳米管包裹聚磷酸铵(APP@CNT)阻燃剂,在此基础上与Mg(OH)₂复配,采用纳米复合技术制备了火安全的电线电缆用阻燃乙烯-醋酸乙烯酯共聚物(EVA)复合材料(APP@CNT/EVA-Mg(OH)₂)。采用SEM、TGA、极限氧指数(LOI)、垂直燃烧(UL-94)、微型锥形量热仪(MCC),电子万能拉伸机和高阻计对阻燃EVA复合材料的结构与性能进行系统研究。结果表明,APP@CNT/EVA-Mg(OH)₂的残炭率从2.4%上升至43.9%,氧指数高达38%,垂直燃烧达到UL-94 V-0级,热释放峰值(PHRR)比纯EVA下降了57.85%,总热释放(THR)下降了57.80%,屈服强度提高了408%,复合材料体积电阻率仍高达3.9×10¹⁵Ω·cm。以上数据表明多层次结构APP@CNT协同Mg(OH)₂阻燃EVA复合材料(APP@CNT/EVA-Mg(OH)₂)具有良好的火安全性能。     

无机填料对环氧模塑料导热和阻燃性能的影响

采用两种无机填料Si₃N₄和Al(OH)₃ 复合填充环氧树脂制备了环氧模塑料(EMCs), 研究了两种填料用量及单独添加和复合添加对环氧模塑料导热性能和阻燃性能的影响。研究结果表明, 单独添加Si₃N₄或Al(OH)₃对环氧模塑料导热性能和阻燃性能的影响规律基本一致, 即随着填料含量的增加, 环氧模塑料的导热性能和阻燃性能均有不同程度的提高; 复合添加Si₃N₄和Al(OH)₃对环氧模塑料的导热性能和阻燃性能均起到积极作用, 但是随着填料中Si₃N₄与Al(OH)₃体积比的变化, 材料导热性能与阻燃性能会产生交叉耦合作用。当 填料中Si₃N₄与Al(OH)₃体积比为3∶2, 总体积分数为60%时, 环氧模塑料的导热率可以达到2.15 W/(m·K), 氧指数为53.5%, 垂直燃烧达到UL-94 V-0级。      

PPO/SEBS/SEBS-g-MAH共混物的阻燃性能研究

以苯乙烯-乙烯/丁二烯-苯乙烯嵌段共聚物(SEBS)为弹性体改性剂，SEBS-g-MAH为相容剂，红磷和Mg(OH)₂作为阻燃剂，采用双螺杆挤出技术，制备了阻燃聚苯醚(PPO)/SEBS/SEBS-g-MAH共混物。结果表明：当红磷用量为15份时，Mg(OH)₂仅用80份，PPO/弹性体共混物的极限氧指数(LOI)就能达到28%,燃烧等级达UL94 V-0级，同时燃烧时的热释放速率(HRR)及生烟速率(SPR)均大幅降低。     

环保型阻燃组合木材料的制备与性能

为了获得环保型阻燃组合木材料,利用桉木旋切单板、酚醛树脂胶黏剂、Mg(OH)2阻燃剂制备阻燃组合木试样,通过拉伸试验、扫描电子显微镜、极限氧指数、热重分析对材料进行力学性能、阻燃性能测试和分析。结果表明,适量添加Mg(OH)2可以明显提高复合材料的胶合强度和阻燃性能;当添加Mg(OH)2的质量为胶黏剂固含量(胶黏剂干基质量)的1.2倍时,材料胶合强度增大48.1%,阻燃体系的极限氧指数达到36.3%;通过Mg(OH)2、Al(OH)3复配,极限氧指数进一步增大至38.7%,阻燃性能进一步提高。     

水菱镁石-Mg(OH)_2协同聚乙烯阻燃复合材料的性能与分解行为

以水菱镁石(HM)和Mg(OH)_2为阻燃剂,利用双螺杆挤出机制备了一系列HM-Mg(OH)_2协同聚乙烯(PE)阻燃复合材料。采用垂直燃烧仪、极限氧指数仪、锥形量热仪和拉伸性能测试仪分别测试了HMMg(OH)_2协同PE阻燃复合材料的阻燃性能和拉伸性能,采用热重分析仪研究了HM-Mg(OH)_2协同PE阻燃复合材料的热分解行为。结果表明,HM与Mg(OH)_2以适当比例复配作为阻燃剂能在更宽的燃烧温度范围内发生分解,起到更好的阻燃效果,在极限氧指数和拉伸强度不变的前提下,HM-Mg(OH)_2协同PE阻燃复合材料的成本大幅下降。两种阻燃剂协同可以减少复合材料点燃初期的无效甚至负面分解,保留了HM分解产物对PE基体高温下分解的抑制作用,同时还可以在燃烧区域表面形成较为稳定和不易破坏的鳞片状保护层,加之复合阻燃剂总体更高的总分解释放率,多种因素共同作用,使复合材料的阻燃效果提高。当HM和Mg(OH)_2以质量比1∶2协同且用量达到复合材料总质量的60wt%时,HM-Mg(OH)_2协同PE阻燃复合材料的极限氧指数为28%,垂直燃烧级别达到UL-94V-0级,拉伸强度达到28.8 MPa。     

苯甲酸功能化石墨烯-Al(OH)3协同阻燃聚丙烯

以氧化石墨（GO）为原料,制备了苯甲酸功能化石墨烯（BFG）,采用IR和XRD对BFG结构进行了表征。再将BFG作为阻燃协效剂添加到Al（OH）₃/聚丙烯（PP）中,研究不同质量比的BFG与Al（OH）₃对PP材料阻燃和力学性能的影响。通过对阻燃BFG-Al（OH）₃/PP复合材料进行极限氧指数（LOI）测试、热失重分析、锥形量热分析、拉伸测试及残炭SEM分析,考察BFG-Al（OH）₃/PP复合材料的阻燃性能和力学性能。研究结果表明,与其他阻燃PP相比,1.5wt% BFG-38.5wt% Al（OH）₃/PP的阻燃和力学性能最佳,LOI可达到24.6%,拉伸强度为20.64 MPa,且其热释放速率峰值和总热释放量比纯PP分别降低了51.5%和18.6%。     

聚甲醛阻燃的研究

选用氢氧化镁(Mg(OH)2)、聚磷酸铵(APP)作为聚甲醛(POM)的阻燃剂,研究了它们对POM阻燃效果及力学性能的影响。结果表明,加入Mg(OH)2阻燃剂后,POM的阻燃性能有较大的提高,当Mg(OH)2的加入量为60％时．极限氧指数由15提高到40．水平燃烧速度由0．33mm／s降至0．31mm／s。APP阻燃POM的效果优于Mg(OH)2,在APP加入量达到25％时即制得自熄的POM。两种阻燃剂的加入都使POM的力学性能下降。     

Mg(OH)2/聚苯乙烯复合材料的阻燃机制

把Mg(OH)₂ (Magnesium hydroxide, MH) 在不同温度热处理不同时间, 得到一系列不同热分解状态的Mg(OH)₂ (Treated magnesium hydroxide, t-MH)。以MH和t-MH为无卤阻燃剂, 聚苯乙烯(PS)为基体, 采用熔体共混法制备了MH/PS和t-MH/PS复合材料。详细研究了MH热处理对t-MH/PS复合材料燃烧性能的影响, 并以此实验结果为基础提出了复合材料的阻燃机制模型。结果表明, 随着热处理温度升高、热处理时间延长, MH逐渐分解并转化成MgO。在相同条件下t-MH/PS复合材料的阻燃性能较MH/PS复合材料显著降低, 但是仍然比纯PS有明显提高。此外, MH热分解产生的MgO有促进PS成炭的作用。MH/PS复合材料的阻燃机制是以下几种因素协同作用的结果: (1)MH分解吸热的冷却降温作用;(2)MH热分解释放水蒸气的气相稀释作用;(3)MH热分解产物MgO的固相阻隔与防护作用;(4)MgO促进PS成炭阻燃作用。     

Electron beam irradiated HDPE/EVA/Mg(OH) composites for flame-retardant electric cables

The mechanical properties and flammability of high-density polyethylene (HDPE)/ethylene vinyl acetate (EVA) mixed with various amounts of magnesium hydroxide (Mg(OH)₂) as the filler in composites, irradiated with electron beam at an irradiation dose of 150 kGy, have been studied. It is found that high-energy electron beam irradiation has significant effects on the mechanical properties of the HDPE/EVA/Mg(OH)₂ composites. The tensile strength and elastic modulus increased greater than in the unirradiated ones. Meanwhile, with increasing the content of Mg(OH)₂ in the composites, the limiting oxygen index (LOI) value increased sharply. The microstructure of the caves of the unirradiated HDPE/EVA/Mg(OH)₂ composites show poor interface of composites compared with the irradiated ones, as observed in SEM micrographs.     

Al(H2PO2)3/聚氨酯弹性体复合材料的制备及阻燃性能

采用熔融共混技术,将Al（H₂PO₂）₃引入聚氨酯热塑性弹性体,制备了一系列次磷酸铝/聚氨酯弹性体复合材料（Al（H₂PO₂）₃/TPU）。采用极限氧指数（LOI）、垂直燃烧（UL-94）、锥形量热测试、TG和SEM研究了Al（H₂PO₂）₃对Al（H₂PO₂）₃/TPU复合材料阻燃性能及热稳定性的影响,采用力学测试研究Al（H₂PO₂）₃对其力学性能的影响。阻燃测试表明,Al（H₂PO₂）₃可以有效提高Al（H₂PO₂）₃/TPU复合材料的阻燃性能。当Al（H₂PO₂）₃添加量为20wt%时,Al（H₂PO₂）₃/TPU复合材料UL-94级别达到V-0级,LOI达到30.5vol%。热重测试表明,Al（H₂PO₂）₃的加入会导致复合材料热分解温度降低,但其残炭率有明显升高。锥形量热测试表明,Al（H₂PO₂）₃的加入有效降低复合材料热释放速率峰值（pHRR）和总热释放（THR）,并明显提高其火灾安全性能,其中20wt% Al（H₂PO₂）₃/TPU的pHRR和THR相对纯TPU分别下降65.7%和20.2%。SEM表明,Al（H₂PO₂）₃/TPU复合材料炭渣致密性有明显提高。在此基础上,采用TGA-FTIR联用分析Al（H₂PO₂）₃/TPU复合材料阻燃机制,研究发现,Al（H₂PO₂）₃在燃烧过程中可以有效促进TPU裂解产物成炭,降低可燃性气体生成量,从而提高复合材料阻燃性能。     

Microdebonding investigation of the effects of thermal residual stress on the bond strength of a graphite/polymide composite

The microdebonding test was used to investigate the effects of thermal residual stresses resulting from different lay-ups in fabrication on the fiber/matrix bond strength of a graphite-fiber-reinforced polyimide composite. This was accomplished by comparing the results of a cross-plied laminate with those of a unidirectional laminate. The results indicated that the measured interfacial bond strength of the unidirectional composites was greater than that of the cross-plied laminate. The thermal radial stress distribution around the fiber for the unidirectional and the [0₂, 90₂]_s laminates were estimated, to explain this reduction of the interfacial bond strength.     

Stress and strength analysis of pin joints in laminated anisotropic plates

Mechanical joints in composites can be tailored to achieve improved performance and better life by appropriately selecting the laminate parameters. In order to gain the best advantage of this possibility of tailoring the laminate, it is necessary to understand the influence of laminate parameters on the behaviour of joints in composites. Most of the earlier studies in this direction were based on simplified assumptions regarding load transfer at the pin-plate interface and such studies were only carried out on orthotropic and quasi-isotropic laminates. In the present study, a more rigorous analysis is carried out to study pin joints in laminates with anisotropic properties. Two types of laminates with (0/ + ₄/90)_s and (0/ ± ₂/90)_s layups made out of graphite epoxy T300/5208 material system are considered. The analysis mainly concentrates on clearance fit in which the pin is of smaller diameter compared to the hole. The main aspect of the analysis of pin joints is the changing contact between the pin and the plate with increasing load levels. The analysis is carried out by an iterative finite element technique and a computationally efficient routine is developed for this purpose. Numerical studies indicate that the location and magnitude of the peak stresses along the hole boundary are functions of fibre angle and the overall anisotropic properties. It is also shown that the conventional assumption of cosine distribution for the contact pressure between pin and the plate in the analysis lead to underestimation of bearing failure load and overestimation of shear and tensile failure loads in typical (0/90₅)_s cross-ply laminates.     

Fatigue damage mechanics of composite materials Part III: Prediction of post-fatigue strength

A damage-based model for post-fatigue notch strength is presented. The model is an extension of a method developed previously to predict the notch strength of laminated composites. A simple finite element representation of the notch tip damage zone is used to obtain the localized damage-modified stress distribution. A uniaxial tensile stress failure criterion is applied to the 0° plies from which the laminate strength is evaluated. In conjunction with the fatigue damage growth law described in Part II, residual strength is calculated as a function of the applied loading conditions, specimen geometry and lay-up for (90/0)_s, (90/0)_2s and (90₂/0₂)_s T300/914C carbon-fibre/epoxy laminates subjected to tension-tension fatigue cycling.