复合成核剂对PP/POE共混体系等温结晶行为的影响

以低分子量尼龙6为主体制备了一种新型复合成核剂NF-10,采用差示扫描量热分析仪、偏光显微镜等分析手段研究了该成核剂对聚丙烯/乙烯-辛烯共聚物(PP/POE)共混体系结晶温度、结晶形态、等温结晶及其动力学的影响。结果表明:NF-10可以提高PP/POE体系的结晶温度、结晶度和结晶速率,减小体系结晶球晶的尺寸,提高晶核密度,显著改善PP/POE共混体系结晶性能。     

Nonisothermal crystallization kinetics of PA6 and PA6/SEBS-g-MA blends

The non-isothermal crystallization kinetics of neat PA6 and binary blends of PA6/SEBS-g-MA were investigated by means of differential scanning calorimetry at four different coolings rates. Three macro kinetic models, viz. Avrami, Jeziorny and Tobin, were used to describe the non-isothermal crystallization kinetics. Primary and secondary crystallization were analyzed by Avrami equation. The results obtained by Avrami equation suggested that under non-isothermal condition, the mechanism of primary crystallization is more complex, while secondary crystallization showed one to three dimensional crystal growths. Tobin model described the overall crystallization kinetics and results were almost similar to those of Avrami model. The results obtained by Dobreva and Gutzowa method suggested that SEBS-g-MA did not act as a nucleating agent for PA6. Three isokinetic models (Augis-Bennet, Kissinger and Takhore) have been used for the evaluation of the activation energy of non-isothermal crystallization kinetics process. The value of activation energy ?E slightly increases in the presence of 5, 10, 20?phr content of SEBS-g-MA and then decreases with at 35 and 50?phr contents of SEBS-g-MA. These results showed that up to 20?phr SEBS-g-MA hinder the mobility of PA6 chain segments and at 35 and 50?phr SEBS-g-MA eases the mobility of PA6 chain segments.     

Effects of swelling agents on the crystallization behavior and mechanical properties of polyamide 6/clay nanocomposites

Montomorillonite was organically modified with three different swelling agents: n‐dodecylamine, 12‐aminolauric acid, and 1,12‐diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X‐ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1686–1693, 2003     

尼龙6/聚酯(PET)共混体系结晶相分离的研究

用差示扫描量热（ＤＳＣ）考察尼龙６／聚酯（ＰＥＴ）共混体系的结晶行为，表明是结晶相分离的。不同条件下，结晶相分离的过程和形成的结晶态不同，反映在热行为上，如熔融过程和相应特征参数值，便随着处理的条件、组成比等而改变。研究结果还表明，当尼龙６组分的质量分数Ｗ ＰＡ－６＜ ０．１ 时，它被ＰＥＴ 阻隔而不再结晶，因两者形成部分氢键，酯基对尼龙６ 结晶影响的结果，尼龙６／聚酯（ＰＥＴ）共混体系中尼龙６ 的熔融峰温，随组成比的变化呈现波浪形曲线。     

Influence of a synthetic ureido nucleating agent on crystallization behavior and mechanical properties of polyamide 6

A synthetic ureido mixture prepared from the reaction of 4,4′‐diphenylmethane disocynanate (MDI) and cyclohexylamine without using any harmful organic solvents, has been used as a nucleating agent (PNA) for polyamide 6 (PA6). The effect of PNA on the crystallization and mechanical properties of PA6 has been studied by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM), tensile test, melt flow index (MFI), and X‐ray diffraction (XRD). The results show that PNA is an effective nucleation agent for PA6. PNA affects the nucleation mechanism of PA6, and substantially accelerates the crystallization rate of PA6 and gives rise to smaller crystal size. In comparison with PA6, the crystallization temperature (T_c) of PA6/PNA (100/0.5) increases 21.3°C and the degree of sub‐cooling (ΔT_c) decreases 23.7°C. Furthermore, because of the heterogeneous nucleation induced by PNA, the spherulites of PA6 become even and tiny based on POM observation. Polymorph transform has been obtained from XRD analysis. The virgin PA6 is free of γ‐phase crystals, presented as α‐phase crystals in this study, but γ‐phase crystal appears after the introduction of PNA. The mechanical and thermal properties of PA6 are obviously improved by the addition of PNA. POLYM. ENG. SCI., 55:2011–2017, 2015. © 2015 Society of Plastics Engineers     

改性纤维素纳米晶对聚酰胺6结晶行为的影响

通过表面基团反应制备了异氰酸酯改性纤维素纳米晶（IPDI?CNC)，将其与聚酰胺6（PA6）共混后研究了有机纳米晶对PA6结晶行为的影响。利用差示扫描量热仪（DSC）对比分析了纤维素纳米晶（CNC）和IPDI?CNC对PA6的结晶度、结晶动力学参数及结晶速率的影响。结果表明，由于IPDI的引入，IPDI?CNC在PA6中的分散性更好，可以有效提高PA6的结晶度；采用 Jeziorny法研究非等温结晶过程，发现IPDI?CNC起到了异相成核作用，提高了PA6的结晶速度和结晶度；由于PA6的结晶能力提高了，IPDI?CNC的加入使PA6的吸水率降低了71.4 %。     

Characterization of thermal behavior and kinetics of crystallization of a thermotropic rigid-chain copolymer

Thermal analysis was employed to estimate the heat of transition, equilibrium melting temperature and surface free energy of a thermotropic liquid crystal copolyester resin (70 mol% p-hydroxybenzoic acid and 30 mol% 2,6-hydroxynaphthoic acid). Specific heats and melting and crystallization behavior were evaluated using differential scanning calorimetry (DSC). Experiments over a wide range of cooling rates indicate two different crystallization processes: a rapid crystallization process and a slow crystallization process. The kinetics of the rapid crystallization process were evaluated using a non-isothermal method. The analysis indicates that the rapid crystallization process can be suitably described by the non-isothermal Avrami equation. The Avrami exponent is found to be equal to 2, which is in agreement with the nucleation and growth mechanism of the rigid rodlike molecules. The kinetics of the slow crystallization process, which were studied using an isothermal method, indicate that the degree of crystallinity varies linearly with log(time). The equilibrium melting temperature for this process is found to be 372°C. The Arrhenius plot yields a linear relationship in the lower temperature range.     

不同相对黏度PA6的非等温结晶动力学研究

以相对黏度(η_r)为2.0,2.4,2.8,3.4,4.0的5种聚酰胺6(PA 6)切片为研究对象,采用差示扫描量热法测试其在不同冷却速率(?)下的非等温结晶过程;基于Jeziorny法和Mo法对不同η_r的PA 6的非等温结晶动力学进行对比分析,并采用Kissinger法计算其结晶活化能(E)。结果表明:PA 6的η_r影响其熔体冷却成形过程中晶核的形成和晶体生长机制;随?的增加,不同η_r的PA 6的起始结晶温度、结晶峰温度、结晶结束温度均有向低温区移动的趋势,结晶焓逐渐降低;基于Jeziorny法,在相同的?下,随着η_r的增加,PA 6的结晶速率呈现先增后减的趋势,η_r为2.8的PA 6的结晶速率最高,η_r为2.0的PA 6的结晶速率最低;基于Mo法,η_r为2.8的PA 6综合表现出较高的结晶速率;由Kissinger法计算得到η_r为2.0的PA 6的E最高。     

液晶环氧/二元胺/CYD-128体系固化行为的研究——Ⅱ性能及增韧机理

采用液晶环氧 (PHBHQ)增韧环氧CYD - 12 8,研究了液晶含量对浇铸体耐热性、冲击强度、弯曲强度的影响。结果表明 ,随液晶含量的增加 ,凝胶时间逐渐缩短 ;当液晶含量为 5 0 %时 ,冲击强度为 40 1kJ/m2比不加液晶环氧时CYD - 12 8体系 (2 3kJ/m2 )提高了近 0 7倍 ,热变形温度提高近 30℃。结合DMTA图和SEM照片 ,分析了液晶环氧增韧的机理。PHBHQ/CYD - 12 8/固化剂体系是部分相容体系 ,在成型过程中发生相分离 ,PHBHQ能形成介晶域 ,起增强和诱发银纹和剪切带的作用 ,从而吸收大量的能量 ,使环氧的韧性得以大幅度地提高     

PA11/SiC复合材料非等温结晶动力学研究

通过熔融共混法制备了尼龙11/碳化硅(PA11/SiC)复合材料,利用差示扫描量热仪(DSC)研究了该复合材料的非等温结晶过程,且采用Avrami方程修正的Jeziorny法和Mo法对其非等温结晶动力学进行了研究,并计算得到相关非等温结晶动力学参数。结果表明:Jeziorny法和Mo法都适用于处理PA11及PA11/SiC复合材料的非等温结晶过程,其分析结果均显示,SiC的加入影响了PA11复合材料的非等温结晶行为,少量(1%)SiC的加入促进了PA11复合材料的成核及晶体生长,提高了结晶速率;由Jeziorny法可知,PA11及其复合材料的非等温过程可分为初期结晶和二次结晶两个阶段,在二次结晶阶段,结晶方式为一维线性、二维盘状和三维球晶生长并存。     

Melting characteristic and β‐crystal content of β‐nucleated polypropylene/polyamide 6 alloys prepared using different compounding methods

BACKGROUND: The distribution of nucleating agents in different phases is still an open question in general, and how to control conditions to prepare alloys rich in β‐crystals of polypropylene (PP) is hardly reported. The main goal of this study was to find out the factors influencing the β‐crystal content in β‐nucleated PP/polyamide 6 (PA6) alloys and determine the best preparation conditions to obtain β‐nucleated PP/PA6 alloys rich in β‐crystals. RESULTS: The compounding methods had little influence on the crystallization temperature of both PP and PA6. However, the melting characteristic and β‐crystal content in β‐nucleated PP/PA6 alloys not only depended upon the compounding methods, but also on the temperature at which the nucleating agent was added. A higher β‐crystal content can be obtained by adding the nucleating agent at a temperature below 190 °C, which is also dependent on the mixing time. CONCLUSION: It is proved by etching the alloys with sulfuric acid that the nucleating agent mainly disperses in the PA6 phase and/or the interface between PP and PA6 when blended at high temperature. Copyright © 2009 Society of Chemical Industry     

尼龙11/HGB复合材料的非等温结晶动力学

采用熔融共混法制备了尼龙(PA)11/空心玻璃微珠(HGB)(PA11/HGB)复合材料,应用差示扫描量热(DSC)仪研究了不同HGB用量下的PA11/HGB复合材料的非等温结晶过程,采用Jeziorny法和Mo法研究了复合材料的非等温结晶动力学,采用X射线衍射(XRD)仪研究了复合材料的晶型变化情况。DSC结果表明,随着降温速率的增加,复合材料的结晶温度总体上降低,结晶温度区间变宽;HGB在PA11基体中起到了异相成核作用。Jeziorny法不适用于PA11/HGB复合材料的非等温结晶动力学研究,而Mo法较为适合,其研究结果表明适量的HGB具有加速PA11基体结晶的作用,但当HGB用量达到8份后,这种作用趋于稳定。XRD结果表明,HGB可诱导PA11基体生成新的β晶。     

Toughening mechanism of SAN resin

SAN resin poly(styrene-co-acrylonitrile) combine, the gloss and transparency of PS with added chemical resistance, high heat distortion temperature, dimensional stability and stiffness characteristics. However brittleness restricts its wider application. The morphology, impact behavior and toughening mechanism of four rubbers toughened SAN resin were investigated in this study.     

硫酸钙晶须及硅灰石纤维填充PA6复合材料的非等温结晶动力学研究

采用差示扫描量热法(DSC)研究了尼龙6(PA6)及其两种复合材料的非等温结晶行为,分别采用Jeziorny法和Mo法对非等温结晶动力学进行了分析,经计算得到相应的非等温结晶动力学参数。结果表明,硫酸钙晶须和硅灰石纤维的加入都能降低复合材料体系的结晶温度;硅灰石纤维的加入可以很好的促进PA6复合材料的结晶,有效的提高体系的结晶速率,而相同含量的硫酸钙晶须对PA6复合材料有一定的阻碍作用,降低了体系的结晶速率。     

Effect of interfacial stress on the crystalline structure of the matrix and the mechanical properties of high‐density polyethylene/CaCO3 blends

A series of high‐density polyethylene (HDPE)/CaCO₃ blends were prepared with different kinds of coupling agents, with CaCO₃ particles of different sizes, and with matrixes of different molecular weights during the melt‐mixing of HDPE and CaCO₃ particles. The mechanical properties of these blends and their dependence on the interfacial adhesion and matrix crystalline structure were studied. The results showed that the Charpy notched impact strength of these blends could be significantly improved with an increase in the interfacial adhesion or matrix molecular weight or a decrease in the CaCO₃ particle size. When a CaCO₃ surface was treated with a compounded coupling agent, the impact strength of the HDPE/CaCO₃(60/40) blend was 62.0 kJ/m², 2.3 times higher than that of unimproved HDPE; its Young's modulus was 2070 MPa, 1.07 times higher than that of unimproved HDPE. The heat distortion temperature of this blend was also obviously improved. The improvement of the mechanical properties and the occurrence of the brittle–tough transition of these blends were the results of a crystallization effect induced by the interfacial stress. When the interfacial adhesion was higher and the CaCO₃ content was greater than 30%, the interfacial stress produced from matrix shrinkage in the blend molding process could strain‐induce crystallization of the matrix, leading to an increase in the matrix crystallinity and the formation of an extended‐chain (or microfibrillar) crystal network. The increase in the critical ligament thickness with an increasing matrix molecular weight was attributed to the strain‐induced areas becoming wider, the extended‐chain crystal layers becoming thicker, and the interparticle distance that formed the extended‐chain crystal network structure becoming larger with a higher matrix molecular weight. The formation of the extended‐chain crystal network and the increase in the matrix crystallinity were also the main reasons that Young's modulus and the heat distortion temperature of this blend were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2120–2129, 2003     

Investigation of crystallization behavior in dynamically vulcanized EPDM–nylon copolymer blends

A thermoplastic vulcanizate (TPV) of a ethylene–propylene–diene terpolymer (EPDM) and nylon copolymer (PA) was prepared by dynamic vulcanization. Maleic anhydride (MAH)–grafted EPDM (EPDM–g–MAH), MAH‐grafted EPR (EPR–g–MAH), and chlorinated polyethylene (CPE) were used as compatibilizers. The effect of dynamic vulcanization and compatibilizer on the crystallization behavior of PA was investigated. Differential scanning calorimeter measurement results showed no pronounced shift in the crystallization temperature for PA in EPDM–PA TPV compared to that for PA in the neat state, whereas the crystallization temperature increased after adding compatibilizer. The decrease in the crystallinity of TPVs was a result of the crystallization occurring in confined spaces between rubber particles. The equilibrium melting temperature (Tm⁰) of the PA copolymer was measured and was determined to be 157°C. The isothermal crystallization kinetics of PA in the neat and TPV states also was investigated. The crystallization rate was highest in the compatibilized TPV and lowest in the neat PA, whereas it was intermediate in the uncompatibilized TPV unvulcanized blends. Compared with unvulcanized EPDM–PA blends, the dynamic vulcanization process seemed to cause an obvious increase in the crystallization rate of the PA copolymer, especially when a suitable compatibilizer was used. This occurred because the dynamic vulcanization introduced fine crosslinked rubber particles that could act as heterogeneous nucleating centers. In addition, the use of a suitable compatibilizer permitted the formation of finely dispersed vulcanized rubber particles and therefore increased the density of the nucleating centers. The complex morphology of the blends was investigated by atomic force microscopy to evaluate the effect of compatibilizer on the size of the dispersed rubber particles. Compared with the morphology of TPVs with the same dosage of EPDM–g–MAH compatibilizer, the morphology of TPVs using EPR–g–MAH as compatibilizer showed much smaller dispersed rubber particles, which may have contributed to the higher crystallization rate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 824–829, 2003     

Melting behavior and nonisothermal crystallization kinetics of polyamide 6/polyamide 66 molecular composites via in situ polymerization

The melting behavior and nonisothermal crystallization kinetics of pure polyamide 6 (PA 6) and its molecular composites with polyamide 66 (PA 66) were investigated with differential scanning calorimetry. The PA 6/PA 66 composites had one melting peak, whereas the coextruded PA 6/PA 66 blends had two melting peaks. With the addition of PA 66 to PA 6 via in situ anionic polymerization, the melting temperature, crystallization temperature, and crystallinity of PA 6 in the composites decreased. The half‐time of nonisothermal crystallization increased for a PA 6/PA 66 molecular composite containing 12 wt % PA 66, in comparison with that of pure PA 6. The commonly used Ozawa equation was used to fit the nonisothermal crystallization of pure PA 6 and its composites. The Ozawa exponent values in the primary stage were equal to 1.28–3.03 and 1.28–2.97 for PA 6 and its composite with 12 wt % PA 66, respectively, and this revealed that the mechanism of primary crystallization of PA 6 and PA 6/PA 66 was mainly heterogeneous nucleation and growth. All the results indicated that the incorporation of PA 66 into PA 6 at the molecular level retarded the crystallization of PA 6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2172–2177, 2005     

Crystallization behavior and mechanical properties of polypropylene copolymer by in situ copolymerization with a nucleating agent and/or nano‐calcium carbonate

The crystallization behavior of polypropylene (PP) copolymer obtained by in situ reactor copolymerization with or without a nucleating agent and/or nano‐CaCO₃ particles was investigated both by thermal analysis and by polarized light microscopy. The Avrami model is successfully used to describe the crystallization kinetics of the studied copolymer. The results of the investigation show that a dramatic decrease of the half‐time of crystallization t_1/2, as well as a significant increase of the overall crystallization rate, are observed in the presence of the nucleating agent. These effects are further promoted in the presence of the nano‐CaCO₃ particles. The incorporation of the nucleating agent and nano‐CaCO₃ particles into PP copolymer remarkably improved the mechanical properties and heat distortion temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 431–438, 2004     

PA11/HGB复合材料的等温结晶动力学研究

利用差示扫描量热仪,Avrami方程和Hoffman-Weeks理论,研究了不同结晶温度下,尼龙11/空心玻璃微珠(PA11/HGB)复合材料的等温结晶和其熔融行为。结果表明,Avrami方程能够较好地描述复合材料PA11/HGB的等温结晶动力学;且材料随温度的升高,结晶速率呈逐渐降低趋势,HGB在复合材料起到成核剂的作用。