热历史对聚醚醚酮及其碳纤维复合材料——Ⅱ.熔融行为的影响

本文利用差示扫描量热仪(DSC)研究了聚醚醚酮(PEEK)和以PEEK为基体的碳纤维复合材料(APC-2)的热历史对它们熔融行为的影响。在200—315℃结晶并退火热处理后,试样的DSC曲线上出现了两个吸热峰。低温吸热峰(峰温T′_m)较小,并与结晶和退火温度(T_c)有关;高温吸热峰(峰温T_m)较大,几乎不受T_n的影响。T′_m的出现与在不同T_c下生成的不完整晶体的熔融和重结晶过程有关,而T_m的出现则与完整晶体的熔融过程有关。实验结果表明,T′_m与T_c之间呈线性关系。按文献报道的方法,将T′_m与T_c的直线外推至与T′_m=T_c直线相交,其交点温度即为平衡熔点.结果表明,PEEK和APC-2试样的“平衡熔点”受不同热历史条件下生成晶体的完整程度的影响。当结晶并退火时间越长,求出的“平衡熔点”值越低,并与理论值接近。实验结果还表明,碳纤维表面具有促进PEEK树脂基体晶体完整化的作用,因而导致APC-2试样中PEEK树脂基体的熔点高于纯PEEK树脂。     

Achieving highly crystalline rate and crystallinity in Poly(l-lactide) via in-situ melting reaction with diisocyanate and benzohydrazine to form nucleating agents

The drawback of the application for poly(_l-lactide) (PLLA) is the low crystalline rate and crystallinity obtaining via normal processing methods. Modifying crystallization of PLLA has been found to be an efficient way to improve its mechanical and heat resistance properties. In this wok, 4, 4′-diphenylmethane diisocyanate (M) and benzohydrazine (P) were employed into PLLA melt to in-situ form nucleating agents. The in-situ melting reaction was confirmed by a nuclear magnetic resonance spectroscopy. The crystallization behavior and crystalline morphology were investigated by a differential scanning calorimetry, a polarized optical microscopy and a field emission scanning electron microscope. The crystalline rate of PLLA was abruptly enhanced by adding (M+P) and melting reaction with PLLA. The crystallization half-time of PLLA dramatically decreased from 42.0 to 1.1 min at 130 °C by the in-situ formation of nucleating agents. The crystallinity of PLLA increased from 10.3 to 42.1 by adding 0.25% (M+P) and melting reaction for 8 min. Furthermore, the size of PLLA crystals was dramatically reduced because of the nucleating effect. Accompanied with improvement on crystallinity, the Vicat softening temperature of PLLA shifted from 57.4 °C to 93.7 °C by the in-situ reaction with 6.00% (M+P), and indicating heat resistance enhancement.     

邻位取代基对芳基杂环磷酸盐成核有效性的影响

以2,4-二叔丁基苯酚为原料分别合成2,2'-亚甲基双(4,6-二叔丁基苯基)磷酸钠(NA-1)和2,2'-亚甲基双(4-叔丁基苯基)磷酸钠(NA-2),并将其应用于等规聚丙烯(i PP),研究该类芳基杂环磷酸盐成核剂邻位取代基对其成核有效性的影响.通过红外吸收光谱(FTIR)、核磁共振谱(NMR)、X-Ray多晶粉末衍射(XRD)、扫描电镜分析(SEM)和热分析对其化学结构、凝聚态结构、颗粒形貌和物性特征进行了表征,确定了NA-1和NA-2的分子结构和凝聚态颗粒的结构、形貌和物性特征.利用偏光显微观察(POM)、扫描电镜(SEM)断口分析、示差式扫描量热分析(DSC)和雾度测试分析对其与i PP的复合材料的晶粒结构、结晶行为及宏观光学性能进行测试表征.结果表明,添加量0.2%时,邻位叔丁基(NA-1)的存在可使复合材料球晶尺度更加细密,结晶温度比无邻位叔丁基(NA-2)增加5.1 K,等温结晶速率提高至0.56 w/g是NA-2的7倍,半结晶时间由NA-2的11.55 min下降至2.36 min,邻位叔丁基存在对材料透光率和雾度值的影响分别达到4.3%,7.4%.SEM断口分析表明二者在i PP基体中分散均匀,平均粒径相近分别为0.79μm和0.82μm,粒径分布曲线相近,二者分散分布的差异性不显著.     

成核剂对聚丙烯熔融行为的影响

成核剂对聚丙烯熔融行为的影响陈彦徐懋（中国科学院化学研究所高分子物理开放实验室北京１０００８０）关键词成核剂，聚丙烯，平衡熔点聚合物的熔融过程受分子量大小、分子量分布、分子链构型（等规度、分子结构单元的键接序列）、不同的结晶晶型、不同的热历史等...     

填充间规聚苯乙烯的结晶

间规聚苯乙烯(sPS)性能取决于结晶行为与晶型,sPS结晶行为与形态有许多研究.本文重点综述了黏土、纳米CaCO3、滑石粉、SiO2、Mg(OH)2、TiO2,和成核剂等对sPS结晶行为、结晶形态、熔融特性与晶型的影响.认为sPS结晶行为与晶型取决于成核能垒.成核能垒低,有利于形成α-晶.熔融温度提高,提高成核能垒,有利于形成β-晶.填料加入阻碍sPS结晶成核,提高成核能垒,有利于形成β-晶.成核剂加入,降低成核能垒,有利于形成α-晶.     

Synergistic toughening effect of β-nucleating agent and long chain branching on polypropylene random copolymer

β-nucleated long chain branched (LCB) polypropylene random copolymers (PPRs) were prepared via reactive extrusion by introducing β nucleating agent (NA), dicumyl peroxide (DCP) and various contents of 1, 6-Hexanediol diacrylate (HDDA) into PPR. Results of Fourier infrared spectroscopy (FTIR) and the rheological properties demonstrate the existence of LCB polypropylene. Mechanical properties including impact strength, tensile strength and elongation at break were studied. The crystal structure, morphology and crystallization behavior were investigated via wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM) and differential scanning calorimetry (DSC). Non-isothermal crystallization kinetics using the Jeziorny method was also studied. The results show an increased LCB degree with increasing HDDA amount. For the sample with a moderate LCB level, synergistic toughening effect of NA and LCB is achieved without deterioration of yield strength or elongation at break, partially because of its higher β-phase content and much smaller spherulite size. It exhibits the minimum values of T_c and Z_c1, and the maximum values of t_1/2 and n₁ in the primary stage of crystallization, regardless of the cooling rate, indicating a slower crystallization rate and more complicated nucleation and crystal growth model.     

红外光谱法研究成核剂对聚丙烯光氧化降解的影响

采用红外光谱和显微红外光谱,对添加两种α成核剂(TM-1、TM-3)和一种β成核剂(TMB-5)的聚丙烯(PP)的自然光氧化降解行为及机理进行了研究。结果表明,添加成核剂前后,PP的光氧化降解产物均含有酮、羧酸、酯、醇和不饱和烃等。三种成核剂的加入并没有改变PP的光氧化降解机理和降解产物,但都对PP的光氧化反应起了一定的加速作用。各体系的光氧化速率依次为：PP/TMB-5>PP/TM-3>PP/TM-1>PP。PP与添加成核剂的PP中的光氧化程度沿深度的分布表现出相似的规律：表面处的羰基指数最高,自曝晒表面向内部,羰基指数逐渐降低,到约250 μm处减小到约为0,这个范围称之为表面氧化层。表面氧化层的厚度不随曝晒时间的不同而不同,而是由紫外光的穿透能力、氧气的扩散、尤其是加工时样品中的温度梯度所决定的。     

成核剂和促进剂对聚对苯二甲酸乙二酯结晶的影响

研究了一种成核剂和结晶促进剂及其混合物对聚对苯二甲酸乙二酯（ＰＥＴ）结晶过程和熔融行为的影响．结果表明,成核剂的引入降低了ＰＥＴ的结晶成核界面自由能,起到促进ＰＥＴ结晶成核的作用,从而加快了ＰＥＴ的结晶速度．而结晶促进剂对ＰＥＴ的结晶速度影响很小,不能促进ＰＥＴ的成核结晶,但能使ＰＥＴ结晶更完善,使ＰＥＴ的结晶度提高．当两者并用时,ＰＥＴ由熔体降温的结晶行为主要由成核剂控制,而成核促进剂的作用不明显．     

MELTING BEHAVIOR OF LOW ETHYLENE CONTENT POLYPROPYLENE COPOLYMERS WITH AND WITHOUT NUCLEATING AGENTS

The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystalto a more perfect crystal during the heating process of samples.     

聚醚醚酮及其碳纤维复合材料——恒温结晶动力学的研究

本文研究了聚醚醚酮(PEEK)和以PEEK树脂为基体的碳纤维复合材料(APC-2)在恒温条件下的结晶行为。采用差示扫描量热仪(DSC)测定从熔体和橡胶体结晶过程中热焓的变化。利用Avrami方程分析了PEEK和APC-2试样的恒温结晶动力学。PEEK从熔体和橡胶体结晶的活化能分别为532.1和531.7KJ/mol,Avrami指数的平均值分别为5.0和3.9;而APC-2则分别为444.2和432.5KJ/mol,3.5和2.3。这些实验结果表明,APC-2试样中碳纤维表面对PEEK树脂基体具有显著的成核作用,能降低其结晶活化能,因而导致PEEK树脂基体结晶速率加快和促进其结晶更加完整。