具有核壳结构特征的相包容粒子设计及其对POM树脂的增韧条件

以POM/TPU/CaCO3复合体系为基础,采用界面诱导技术使TPU被诱导并包覆在CaCO3表面上,自动地形成以CaCO3为核,以TPU为壳的相包容粒子,并实现了对POM树脂的有效增韧,改性材料不仅制备方法简单,而且在性能上完全达到了目前POM/TPU合金的水准。首次证明了利用具有包覆层的无机刚性粒子对高分子基体进行增韧时,其脆-韧转变不仅和增韧粒子的粒间距有关,而且和粒子包覆层厚度有关。对POM树脂而言,只有体系的粒间距达到临界值Tc≤0．18μm,且包覆层厚度达到临界值Lc≥0．7μm时,材料才有可能发生脆-韧转变,此时材料的冲击强度可比POM基体树脂增大十数倍,而且拉伸强度可达30MPa左右。     

PP／POE／纳米CaCO3复合材料的制备与性能研究

采用逐级分散共混法，制备了PP/POE／纳米CaCO3复合材料，研究了其力学性能和微观结构。逐级分散法先制备纳米CaCO3母料，然后将PP分多次加入含纳米CaCO3的共混体系中，目的在于改善纳米CaCO3的分散，以提高复合材料的力学性能。研究结果表明：采用逐级分散法制备的PP/POE／纳米CaCO3复合材料的冲击强度为64．2kJ／m^2，比直接共混法高16．9％，比通常的母料法高9．7％。复合材料的微观结构研究表明：纳米CaCO3粒子基本上都分布在连续相PP中。     

热塑性聚氨酯/无机纳米粒子增韧改性聚甲醛研究

采用热塑性聚氨酯弹性体(TPU)和无机纳米粒子复合增韧改性聚甲醛(POM),制备了刚韧平衡的POM/TPU共混物。讨论TPU及无机纳米粒子种类、稳定剂体系及注塑工艺对复合材料力学性能的影响。结果表明,聚酯型TPU-2对POM增韧效果较好;纳米Ca CO3可以有效提高共混材料强度;添加抗氧剂Irganox 245制备的复合材料具有更高的断裂伸长率和冲击韧性;注塑工艺对POM/TPU复合材料性能影响较大。     

纳米CaCO3/SBS共混改性研究

用单螺杆挤出机制备了纳米CaCO3/SBS共混物.分别采用了纳米CaCO3(粉料)和纳米CaCO3母料.结果表明.直接添加纳米CaCO3(粉料)对SBS的补强效果十分有限,纳米CaCO3母料的加入可以改善增强效果.研究了纳米CaCO3母料的添加量对共混物流变性能和耐磨性能的影响,并通过SEM和TEM观察了纳米CaCO3粒子的分散状况.     

MBS核-壳粒子的内部结构对MBS/PVC光学性能的影响

以乳液聚合的方法合成了具有核-壳结构的MBS树脂。恒定MBS中M/B/S的比例为30/42/28,通过采用不同的引发体系及加料方式制备不同内部结构的橡胶粒子。将MBS树脂与聚氯乙烯（PVC）共混,研究了橡胶粒子的内部结构对共混物透光性的影响。用透射电子显微镜对共混物的形态进行了研究,MBS粒子分别具不同的包容物结构。研...     

超高韧性聚甲醛/聚氨酯复合材料的性能与结构研究

采用双螺杆挤出机制备了超高韧性聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)共混物,通过力学测试和扫描电子显微镜(SEM)等手段研究了树脂流动性、TPU种类对POM/TPU共混体系性能及结构的影响。结果表明:当TPU含量50%时,配合不同粘度的POM树脂,可使共混体系达到超高的冲击强度,材料在拉伸过程出现应变-硬化过程,POM和TPU在共混体系中呈现两相双连续结构。相比于聚酯型TPU,使用聚醚型TPU制备的共混体系具有更高的低温缺口冲击强度。     

聚甲醛/纳米CaCO3体系的制备与性能

用纳米CaCO3填充改性聚甲醛(POM)，研究了纳米CaCO3的含量、粒径对POM／纳米CaCO3复合体系力学性能、分散形态等的影响。结果表明，影响复合体系韧性的主导因素是纳米CaCO3在POM中的分散形态及其与POM间的界面粘结状况；纳米粒子在POM中分散均匀，分散相尺寸小，与POM间界面粘结好有利于提高复合体系的冲击韧性；纳米CaCO3的增强增韧作用优于微米CaCO3。     

加工方式对纳米碳酸钙母料的制备及其聚乳酸复合材料性能的影响

采用母料法即通过连续混炼机和双螺杆挤出机分别制备了纳米碳酸钙（nano-CaCO3）母料,后将母料按照一定配比添加到聚乳酸（PLA）树脂中进行注塑。通过热重分析仪、扫描电子显微镜和旋转流变仪等对复合材料进行了分析表征,探讨了母料法加工工艺对nano-CaCO3在PLA树脂中分散的影响。结果表明,连续混炼机制备的母料更有利于nano-CaCO3在PLA基体中分散,降低复合材料复数黏度、提高结晶度;同时当添加母料含量相同时,连续混炼母料对复合材料拉伸强度“损失”程度更低,对缺口冲击强度“补强”程度更高。     

POM/TPU共混合金的增韧与断裂行为研究

采用熔融共混法制备了聚甲醛(POM)/热塑性聚氨酯(TPU)共混合金。通过扫描电子显微镜(SEM)研究了POM/TPU共混合金的两相形态,借助Considere作图法从唯象角度分析了TPU对POM基体的增韧行为,利用Newman模型和J-积分法解释分析了POM/TPU共混合金的断裂力学行为。结果表明,在POM/TPU共混合金中,TPU与POM具有良好的黏结效果;TPU有利于POM形成稳定的细颈,增韧效果明显;TPU能有效传递载荷,降低了POM对裂缝的敏感程度,显著提高POM的断裂韧性。     

聚甲醛/弹性体/碳酸钙复合材料的研究

用弹性体和CaCO3复合改性POM。采用TPU为增韧剂，CaCO3为增强剂，研究了加工方法、组成比、填料用量、粒径及分散形态等因素对复合材料性能尤其是冲击韧性的影响。结果表明，两步法制备复合材料的冲击韧性大大高于一步法；且纳米级CaCO3填充复合材料的综合性能优于其它粒径大小的填料；适量的弹性体及无机纳米填料的加入利于获得较好的增韧效果，当弹性体用量约为10％，CaCO3用量为3％时，与纯POM相比，冲击强度提高了3倍，弯曲模量与纯POM接近。     

核-壳结构纳米CaCO_3/SiO_2复合粒子的制备

采用在氢氧化钙碳化过程中向体系中滴加硅酸钠溶液的方法来制备核-壳结构的纳米CaCO3/SiO2复合粒子。将超细碳酸钙的制备和表面包覆改性工艺融为一体,在碳化反应的末期加入硅酸盐水溶液,通过控制碳化末期的反应及硅酸盐水解反应的进程,有效地防止了碳酸钙粒子的团聚,同时在超细碳酸钙粒子表面成膜包覆二氧化硅薄层,获得核-壳结构的CaCO3/SiO2复合颗粒。用耐酸性测试、吸油值、TEM、IR等方法对复合粒子的包覆效果、粒径大小、形貌、化学组成等做了分析和表征。     

TPU增韧改性POM的研究

利用双螺杆挤出机制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)和POM/TPU/异氰酸酯预聚物(Z)共混物.采用力学性能测试方法、偏光显微镜(PLM)、傅立叶转换红外线光谱 (FTIR)、扫描电子显微镜(SEM)等研究了共混物的力学性能、结晶行为及形态结构.结果表明,不同种类TPU增韧的共混物的缺口冲击强度和断裂伸长率都随TPU含量的增加而增加,TPU(95A)增韧的POM/TPU共混物的刚性较好,TPU(250)增韧的POM/TPU共混物的韧性较好;Z能促进TPU在基体树脂中的均匀分散,增强两相界面的粘结力,并能细化球晶.     

Impact modification of polyacetal by thermoplastic elastomer polyurethane

The main goal of this study was impact modification of polyacetal [polyoxymethylene (POM)] with thermoplastic elastomer polyurethane (TPU). We modified the impact strength of POM 10‐fold. The mechanical properties, thermal behavior, and morphology of POM/TPU blends consisting of 5 to 50% of TPU were studied. It was found that the best impact modification of the blends was at 15% concentration of TPU and the maximum elongation at break was at 30% concentration of TPU. The impact strength of POM/TPU blends can be improved by using diphenylmethane diisocyanate (MDI) as compatibilizer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2573–2582, 2002     

聚氨酯增韧聚甲醛的研究

采用机械共混的方法，制备了聚甲醛(POM)／热塑性聚氨酯弹性体(TPU)复合材料；研究了缺口曲率半径对纯POM以及TPU增韧体系冲击韧性的影响；并对其形态结构进行了测试分析。结果表明，纯POM的冲击韧性受缺口尖锐程度影响大，TPU能减小POM结晶度，缩小球晶尺寸，显著降低POM的缺口敏感性；POM／TPU形成双连续结构时成为超韧体系。     

导电增韧聚甲醛的制备及性能

探讨了炭黑和抗静电剂改性硅油分别使用与协同使用对聚甲醛(POM)导电性能和力学性能的影响,同时研究了增韧剂聚氨酯弹性体(TPU)对POM导电性能和力学性能的影响。结果表明:炭黑和改性硅油配合使用,可使POM的表面电阻率达到102Ω,而其力学性能也比单独使用炭黑有所改善。增韧剂TPU进一步提高了导电POM的冲击强度,但使导电POM的表面电阻率增加到106Ω。     

Toughening mechanism in polyoxymethylene/thermoplastic polyurethane blends

In order to better understand the toughening mechanism in polyoxymethylene (POM)/thermoplastic polyurethane (TPU) blends and obtain ‘super‐toughened’ POM, we carried out an investigation on the notched impact strength, fractured surface, inter‐particle distance and spherulite size of POM as a function of the TPU content. A compatibilizer, namely polystyrene‐block‐poly(ethylene–butylene)‐block‐polystyrene, grafted with maleic anhydride (SEBS‐graft‐MA), was used to enhance the interfacial interaction between the POM and TPU. The impact strength is found to increase in two steps as a function of TPU content, namely a linear increase at the very beginning, and then a jump of impact strength is seen when the TPU content is larger than 30 wt%. A ‘supertough behavior’ is not observed for POM/TPU blends at room temperature, but can be achieved after adding 5 wt% of SEBS‐graft‐MA as the compatibilizer. The impact strength was found to depend not only on the interparticle distance but also on the interfacial interactions between POM and TPU. The dependence of impact strength on crystal size is considered for the first time, and a single curve is constructed, regardless of the composition and interfacial interactions. Our results indicate that the crystal size of POM indeed plays a role in determining the toughness, and has to be considered when discussing the toughening mechanism. Copyright © 2004 Society of Chemical Industry     

Brittle‐Ductile Transition and Toughening Mechanism in POM/TPU/CaCO3 Ternary Composites

Summary: Polyoxymethylene (POM)/elastomer/filler ternary composites were prepared, in which thermoplastic polyurethane(TPU) and an inorganic filler, CaCO₃, were used to achieve balanced mechanical properties of POM. A two‐step processing method, in which the elastomer and the filler were mixed to a masterbatch first and then the masterbatch was melt‐blended with pure POM, was used to obtain a core‐shell microstructure with CaCO₃ covered by TPU. A brittle‐ductile transition phenomenon was observed with increasing TPU content for this ternary system. To better understand the toughening mechanism, we investigated the fractured surface, interparticle distance, and the spherulite size of POM as function of the TPU and CaCO₃ content. The critical TPU content depended on not only the content of CaCO₃, but also the size of CaCO₃ particles. The observed brittle‐ductile transition was discussed based on the crystallinity and spherulite size of POM as well as Wu's critical interparticle distance theory. The results showed that the impact strength of POM/TPU/CaCO₃ ternary system depends on a critical, interparticle distance, which varies from one system to another. The dependence of the impact strength on the spherulite size was considered for the first time, and a single curve was constructed. A critical spherulite size of 40 micron was found, at which brittle‐ductile transition occurs, regardless of the TPU and CaCO₃ content or the size of CaCO₃ particles. Our results indicate that the spherulite size of POM indeed plays a role in determining the toughness, and must be considered when discussing the toughening mechanism.

Izod impact strength vs. the crystal size for POM/TPU blends and POM/TPU/CaCO₃ ternary composites.     

有机杂化纳米CaCO3/SiO2复合粒子对硅橡胶性能的影响

以纳米碳酸钙（CaCO3）为原料,采用溶胶沉积法制备出具有核/壳结构的纳米CaCO3/SiO2复合粒子,并将其原位有机杂化。用纳米CaCO3/SiO2复合粒子替代部分气相法白炭黑作为硅橡胶的补强填料,采用扫描电子显微镜、拉力试验机、热失重仪等对改性硅橡胶的力学性能和热稳定性能进行表征。结果表明：有机杂化剂的种类不同,纳为CaCO3/SiO2复合粒子对硅橡胶的补强效果不同;与用未杂化的纳米CaCO3/SiO2复合粒子取代部分气相法白炭黑的硅橡胶相比,用经A-151杂化的复合粒子取代部分气相法白炭黑的硅橡胶,其拉伸强度、断裂伸长率得到明显改善,耐热性也得到提高;但撕裂强度大大降低。同时还发现,硅橡胶的力学性能及耐热性能在很大程度上也与复合粒子的取代量有关;即使是经KH-570杂化的复合粒子,当取代量小于10%时,其硅橡胶的性能也优于全部用气相法白炭黑补强的硅橡胶。     

Morphology control of polyoxy‐methylene/thermoplastic polyurethane blends by adjusting their viscosity ratio

Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = η_TPU/η_POM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (T_p) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at T_p < 190 °C, filamental morphology when P ≈ 1 at T_p ≈ 190 °C and spheroidal morphology when P < 1 at T_p > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (～14 kJ m^?2). Copyright © 2006 Society of Chemical Industry     

含异氰酸酯基的低聚物和聚醚增容改性POM/TPU共混物

利用双螺杆挤出机制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)、POM/TPU/含异氰酸酯基的低聚物(Z)以及POM/TPU/Z/聚醚3种共混物。采用力学性能测试、差示扫描量热分析(DSC)、偏光显微镜(PLM)、傅里叶转换红外线光谱 (FTIR)、扫描电子显微镜(SEM)、动态力学性能分析(DMA)等,研究了3种共混物的力学性能、结晶行为及形态结构。结果表明：共混物的缺口冲击强度和断裂伸长率随TPU含量的增加而提高;异氰酸酯基低聚物（Z）和聚醚在促进分散相分散、增强两相间的相容性方面发挥重要作用,降低了聚甲醛的结晶度,能够有效地提高共混物的缺口冲击强度和断裂伸长率。