聚酰胺热氧化降解机理

通过详细分析测定反应产物 ,研究了聚酰胺 (PA6)的热氧化降解机理 .用化学方法测定了PA6热氧化过程中几种主要基团含量的变化 ,对PA6热氧化的气相挥发产物进行收集和分析鉴定 ,还对经过氧化的PA6样品进行水解并用GC MS法对水解产物进行了分析鉴定 .在这些实验结果的基础上 ,提出了较完整的聚酰胺热氧化降解机理 .该机理包含了自由基在与酰胺基的羰基相连的亚甲基上的夺氢反应及一系列自由基加成环化和诱导断链的反应 ,能很好地解释反应产物的分析结果 .     

苯乙烯/异戊二烯/丁二烯共聚物热降解过程

利用热重法研究了聚苯乙烯-聚异戊二烯／丁二烯-聚苯乙烯三嵌段共聚物S(IB)S在N2气氛以不同速率β升温时的热降解过程及动力学。结果表明，S(IB)S的热降解过程随着升温速率的增大由三步变为两步进行，热降解温度随着升温速率的增大而升高；分别采用Kissinger方程、Doyle方程计算热降解过程的表观活化能，并与用Coats-Redfen方法计算结果比较，分析鉴别出热降解过程的动力学表达式，从而确定了S(IB)S的热降解机理。     

纳米SiO2对火焰喷涂聚酰胺12涂层非等温结晶与熔融行为的影响

采用火焰喷涂法制备了聚酰胺12/纳米SiO2(PA12/nano-SiO2)复合涂层,利用差示扫描量热法(DSC)对复合涂层的非等温结晶过程、熔融行为进行了分析.结果表明:纳米SiO2粒子的加入不仅能提高复合涂层的结晶度和结晶温度,而且使复合涂层的熔融峰温度高于纯PA12涂层,说明纳米SiO2粒子具有明显的成核剂作用,它能诱导聚酰胺大分子结晶,提高其结晶能力、结晶速率、结晶的完善程度及结晶度,并能改善涂层的力学、耐老化及耐摩擦磨损性能.     

新型侧基含磷共聚酯的阻燃和热降解动力学

利用动态热重分析法(TG)研究了聚酯(PET )及侧基含磷共聚酯(FR-PET)在不同升温速率下的热稳定性及热降解动力学, 并通过极限氧指数法(LOI)考察了FR-PET的阻燃性能; 采用Flynn-Wall-Ozawa方法分析了PET和FR-PET的热降解表观活化能; 利用Coast-Redfern方法通过对不同机理模型的选取, 确定了PET和FR-PET热降解动力学机理及其模型, 得出了主降解阶段的非等温动力学方程及热降解速率曲线图. 研究结果表明, 侧基含磷单元的引入提高了聚酯的阻燃性能, 侧基上的P—C和P—O键易断裂, 从而降低了聚酯的热稳定性. PET和FR-PET的热降解表观活化能(0.1≤α≤0.85)分别为194-227和184-209 kJ/mol; PET和FR-PET热降解反应均属于受减速形α-t曲线控制的反应级数机理, 其机理函数为f(α)=3(1-α)2/3(0.1≤α≤0.85). 侧基含磷单元的引入对PET的主降解阶段的热降解速率并无实质上的影响. 侧基含磷共聚酯的凝聚相阻燃作用有限, 可能以气相阻燃机理为主发挥阻燃作用.     

热塑弹性体热寿命和热降解动力学

利用热重法研究了聚苯乙烯/聚二烯烃/聚苯乙烯三嵌段共聚物(SIS,SBS,SI/BS)在氮气气氛条件下以不同升温速率β时热降解动力学及其热寿命。确定了热降解温度与升温速率的关系,求得了热降解过程的表观活化能和热降解速率常数,得到了不同失重率时的热寿命方程,计算出三种化合物在不同温度下的寿命。     

新型阻燃聚丙烯腈共聚物在空气中的非等温热分解动力学

用O,O-二乙基-O-烯丙基硫代磷酸酯(DATP)与丙烯腈共聚合成了新型阻燃聚丙烯腈共聚物(FR-PAN), 对其在空气中的非等温动力学通过TG-DTG技术进行了研究, 并通过极限氧指数法(LOI)考查了FR-PAN的阻燃性能; 利用Kissinger方法和Flynn-Wall-Ozawa (FWO)方法计算出了FR-PAN热降解过程中的表观活化能; 采用Satava-Sestak方法通过对不同机理模型的选取, 确定了FR-PAN的热降解机理. 结果表明, 由Kissinger法和FWO法所计算得到的FR-PAN的表观活化能分别为119.62和123.99 kJ•mol－1; FR-PAN的热降解反应属于随机成核和随后增长机理, 其机理函数为G(α)＝－ln(1－α), 反应级数n＝1.     

粉末状半芳香尼龙PA12T的合成

以对苯二甲酸和1,12-十二碳二胺为原料,采用无水乙醇为溶剂,合成了粉末状的半芳香尼龙聚对苯二甲酰十二碳二胺(PA12T)。对影响PA12T聚合的各因素进行了分析研究,确定了合适的聚合工艺条件;利用红外光谱图(FT-IR)和核磁氢谱图(1H-NMR)对PA12T的结构进行了表征。该方法工艺简单,易于实现,适合工业化生产。     

阻燃共聚酯/粘土复合物热降解动力学研究

用插层共聚方法合成了含磷共聚酯／粘土复合物。用热重(TG)方法考察热降解动力学。通过在空气中以不同的升温速率升温至设定温度,用Kissinger法和Hymn-Wall-Ozawa法对数据进行处理。结果表明,粘土组分含量较高的反应活化能较大,热稳定性较好。     

半芳香尼龙6T/66的合成和非等温结晶动力学的研究

采用成盐、预聚合、固相聚合三步法制备高分子量的PA6T/66,用差示扫描量热法(DSC)研究了PA6T/66的非等温结晶动力学,结果表明:结晶温度随着降温速率的增大而降低;半结晶期T1/2随降温速率Ф的增大呈指数下降,表明结晶速率随降温速率的增大而提高;由用R-T法可以得到在不同结晶度下lgΦ对lgT有较好的线性关系。用Kissinger方法计算得到PA6T/66(55/45)非等温结晶活化能分别为ΔE=-61.51kJ/mol。     

聚酰胺6/蒙脱石纳米复合材料的紫外光老化

聚合物 /层状硅酸盐纳米复合材料的研究十分活跃 [1～ 4 ] .聚酰胺 6/蒙脱石 ( PA6/MMT)纳米复合材料与纯聚酰胺 6( PA6)相比 ,模量和强度明显提高 ,耐热性能提高尤为显著 .光氧化行为材料科学领域的重要研究课题 .Admas等 [5]报道在紫外光照射下 ,聚丙烯 /粘土纳米复合材料的氧化速度要比纯聚丙烯的快 .对于 PA6/MMT纳米复合材料的光老化研究尚未见报道 .本文以傅里叶变换红外光谱定量研究手段 ,对比分析了 PA6/MMT纳米复合材料与 PA6的紫外光氧化性能 .1　实验部分　　采用熔体插层技术 ,将 PA6( Honeywell B1 0 0 MP)和有机蒙…     

TRANSAMIDATION IN THE in situ BLENDING OF POLYAMIDE 1212 WITH POLYAMIDE 6 THROUGH ANIONIC POLYMERIZATION OF CAPROLACTAM

20 wt% polyamide 12(PA1212)pellets were dissolved in molten caprolactam.The caprolactam was then catalyzed at 180℃and polymerized by means of anionic ring-opening polymerization to produce in situ blends of the resultant polyamide 6(PA6)and PA1212.Mechanical blends with same ingredient were prepared through melt blending on a twin-screw extruder.Scanning electron microscopy(SEM)observation revealed that contrary to the mechanical blends with small spherulites embedded in the matrix,no phase-separation existed in the in situ blends.The results of thermal analysis by differential scanning calorimetry(DSC)showed that single melting peak and crystallization peak existed for the in situ blends,while two melting and crystallization peaks appeared for the mechanical blends.The in situ blend film and the mixed blend film,both cast from a dilute formic acid solution with a concentration of 0.5 g/L,remained similar crystallization and melting behavior as above.It is proved by solution ~(13)C-NMR analysis that transamidation took place during the in situ blending,and it is suggested that the combination of temperature increasing and the basic surrounding derived from NaOH during polymerization resulted in the occurrence of transamidation.Furthermore,it is proposed that the interchange reaction between PA1212 and PA6 also resulted from the degradative reaction during the anionic polymerization.     

Thermal degradation and crystallisation studies of reactively compatibilised polymer blends

The thermal degradation and crystallisation behaviours of polyamide12/isotactic polypropylene (PA12/PP) blends were studied. Effects of blend ratio and compatibiliser concentration on the thermal degradation properties of the blends were analysed. The activation energy for degradation in compatibilised and uncompatibilised blends computed using Horowitz-Metzger equation was reported. The blend ratio as well as the presence of compatibiliser has significant effect on the thermal stability of the blends. Phase morphology was found to be one of the decisive factors that affected the thermal stability of both uncompatibilised and compatibilised blends. Melting and crystallisation behaviours of the blends in the presence and absence of compatibiliser were evaluated. It was observed that blending has no significant effect on the melting and crystallisation properties of PA12 and PP. Compatibilisation of 70/30 and 50/50 PA12/PP blends didn't affect the crystallisation and melting behaviours of PA12 and PP even though some discrepancies were observed.     

尼龙1212/尼龙6共混体系的非等温结晶行为

用DSC研究了尼龙 12 12 ,尼龙 6及其共混体系的非等温结晶行为 .结果表明 ,加工历史对尼龙的结晶和熔融行为影响很大 .经双螺杆挤出机挤出的尼龙 12 12和尼龙 6 ,由于应力诱导分子链取向 ,其结晶温度都有不同程度的提高 ,且表现出多重熔融现象 .在共混体系中 ,尼龙 12 12分子在共混物的界面上异相成核结晶 ,提高了其结晶温度 ,但酸酐化SEBS的加入抑制了分子链的运动又使其结晶温度降低 .共混体系降低了尼龙12 12的熔融温度 ,并使得其高熔点的熔融峰逐渐消失 ;而尼龙 6的熔融行为基本上没有变化 .     

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.     

Complementary effects of multiwalled carbon nanotubes and conductive carbon black on polyamide 6

This article introduces a newly innovative idea for preparation of superconductive ternary polymeric composites of polyamide 6 (PA6), conductive carbon black (CCB), and multiwalled carbon nanotubes (MWCNTs) with different weight ratios by a melt‐mixing technique. The complementary effects of CCB and MWCNTs at different compositions on rheological, physical, morphological, thermal, and dynamic mechanical and electrical properties of the ternary composites have been examined systematically. We have used a novel formulation to produce high‐weight fraction ternary polymer composites that show extremely higher conductivity when compared with their corresponding binary polymer composites at the same carbon loading. For example, with an addition of 10 wt % MWCNTs into the CCB/PA6 composite preloaded with 10 wt % CCB, the electrical conductivity of these ternary composites was about 5 S/m, which was 10 times that of the CCB/PA6 binary composite (0.5 S/m) and 125 times that of the MWCNT/PA6 binary composite (0.04 S/m) at 20 wt % carbon loading. The incorporation of the MWCNTs effectively enhanced the thermal stability and crystallization of the PA6 matrix in the CCB/PA6 composites through heterogeneous nucleation. The MWCNTs appeared to significantly affect the mechanical and rheological properties of the PA6 in the CCB/PA6 composites, a way notably dependent on the MWCNT contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1203–1212, 2010     

One‐pot synthesis of polyamide 12,T–polyamide‐6 block copolymers

Polyamide 12,T–polyamide‐6 (PA‐12,T–PA‐6) block copolymers were synthesized by anionic polymerization of caprolactam using a PA‐12,T macrocoinitiator (McI). PA‐12,T McI and its precursors are soluble in molten caprolactam allowing for both the McI step‐growth polymerization and anionic polymerization to be performed in one‐pot. It was found that the competing reaction rates of caprolactam ring‐opening polymerization and McI transamidation are both deterred by a common ion effect using CaCl₂ and soluble materials were obtained using >1 mol % CaCl₂. Without CaCl₂, the reaction mixture solidifies in less than 30 s and produces crosslinked materials. To understand this effect, PA‐12,T McI reactions with caprolactam were performed with 1–10 mol % CaCl₂, and polymer structures were characterized using ¹³C NMR and dilute solution viscometry. These data were then correlated with unique thermal properties and swelling behavior of the block copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) filled with metal phosphinates

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) (PA10T) containing aluminum diethlyphosphinate (BEPAL) were investigated. The influence of BEPAL on the thermal degradation behavior of PA10T was studied using thermogravimetry, flammability test and chemical analysis. A decomposition model was given on the basis of Lewis acid-base interaction. The introduction of BEPAL led to reduced decomposition temperature, while the limiting oxygen index was greatly improved. The investigation of mechanical properties of PA10T/BEPAL composites indicated that the tensile strength firstly increased when low content BEPAL was added, then decreased with further increasing the concentration of BEPAL due to the agglomeration of filler particles. Dynamic mechanical analysis (DMA) results revealed that the presence of BEPAL hindered the movement of molecular chain.     

Thermal degradation behavior of multi-walled carbon nanotubes/polyamide 6 composites

This paper focuses on the thermal degradation behavior of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites under air and nitrogen atmosphere using thermogravimetric analysis (TGA). The results show that the dispersion of amino-functionalized MWNTs (f-MWNTs) in PA6 is more homogeneous than purified MWNTs (p-MWNTs). The presence of MWNTs improves the thermal stability of PA6 under air obviously, but has little effect on the thermal degradation behavior of PA6 under nitrogen atmosphere. The activation energies for degradation under air, E_a, estimated by Kissinger method, are 153, 165 and 169 kJ/mol for neat PA6, p-MWNTs/PA6 and f-MWNTs/PA6 composites, respectively. The p-MWNTs/PA6 composites show two-step degradation not only under air but also under nitrogen atmosphere, however, neat PA6 and the f-MWNTs/PA6 composites exhibit two-step degradation only under air.     

Thermal,physical and mechanical properties of hydrogenated dimer acid-based Nylon 636/Nylon 66 copolymers

Hydrogenated dimer acid-based Nylon 636/NyIon 66 copolymers were synthesized by in situ polymerization.The effects of Nylon 66 contents on the copolymers were characterized by intrinsic viscosity measurements,attenuated total reflection-Fourier transform infrared spectroscopy,X-ray diffraction,differential scanning calorimetry,tliermogravimetric analysis and mechanical tests.The results showed that incorporation of Nylon 66 into hydrogenated dimer acid-based Nylon had no significant effect on the glass transition or melting temperatures.However,the crystallization temperature,crystallinity degree and the maximum rate of decomposition temperature from derivative thermogravimetry measurements vary.Mechanical testing data revealed that with increasing Nylon 66 concentrations,the tensile strength of copolymers increased,while the elongation at break point and notched izod impact strength decreased.The physical and mechanical properties of HN-40,HN-50 and HN-60 are similar to those of the current PA11,PA1212,and PA1111 Nylon products.