碳酸钙在塑料中的应用

CaCO_3是塑料加工中使用最广泛,用量最大的一种无机填料。本文介绍了CaCO_3品种及其在国内外的应用动向;较系统地阐明了CaCO_3在塑料应用中的表面处理技术和CaCO_3填充母料的配方设计原则及生产工艺路线。     

改性碳酸钙用于聚氯乙烯的研究

研究了一种改性碳酸钙的性质及其在聚氯乙烯中的应用情况。研究结果表明,这种改性碳酸钙与普通碳酸钙相比,具有吸油值低、堆积密度大、分散性好、热稳定性高等特点。填充于聚氯乙烯中,不仅能改善物料的加工性能及制品的物理力学性能,而且还具有较高的热稳定性能。     

纳米碳酸钙在橡胶中的应用

分别将纳米碳酸钙与白炭黑、半补强炭黑、沉淀碳酸钙和活性硅粉在NR,SBR,EPDM和NBR中的应用进行了对比试验。结果表明,纳米碳酸钙分别对4种橡胶具有较好补强性能,可提高拉伸强度、拉断伸长率、撕裂强度、弹性和热老化性能,降低低温性能;对非补强性橡胶的补强性能特别明显。     

高性能无机填料在PP改性中的应用

讨论了无机填料微细化和表面活化以及无机粒子对聚丙烯增韧增强机理,介绍了无机填料对聚丙烯的改性效果与应用。     

碳酸钙市场前景看好

碳酸钙是重要的无机化工产品。由于价格低、原料广、无毒性，被广泛地用作橡胶、塑料、纸张、涂料、牙膏等的填料。全世界每年在纸张中碳酸钙的用量约1100万t，占填料总量的60％以上，用于塑料的约150万t以上。近来科学家发现，超细碳酸钙具有补强作用，可用作汽车底盘防石击的涂料。日本、美国和英国在超细碳酸钙的研制、生产、应用方面处于国际     

碳酸钙填充PP的断裂韧性研究

用仪器化落重式冲击实验装置研究CaCO_3填充PP复合材料的断裂韧性。测量了CaCO_3含量为10wt%～40wt%复合材料试样的冲击强度、G_(?)(临界应变能释放速率)和K_(?)(临界应力强度因子)。结果表明,在上述CaCO_3含量范围内,CaCO_3填充PP的断裂韧性高于纯PP,当CaCO_3含量为20～30wt%时,断裂韧性达最大值。由此说明,在一定条件下,CaCO_3可改善PP的断裂韧性。此外,还简要地讨论了增韧机理。     

碳酸钙的活化改性

一、前言碳酸钙作为一种无机填料,使用已有一百余年历史,但是在填充各种高聚物时,也存在着明显的缺点;一是碳酸钙是无机化合物,它表面性质是亲水疏油,在高聚物内部,分散性极差,另一是碳酸钙不能与高聚物产生化学结合,不能起补强作用,仅能起增容作用。所以,由于碳酸钙的填充,会造成高聚物的某些性能降低,特别是过量填充,使高聚物性能急剧下降,以致制品无法使用。     

碳酸钙在粉末涂料中的应用

根据多年来从事粉末涂料生产的经验，结合碳酸钙的综合性能，提出了在粉末涂料中用不含重金属的碳酸钙填料代替常用的硫酸钡填料，并列举其应用配方。     

Polypropylene/calcium carbonate nanocomposites

Polypropylene (PP) and calcium carbonate nanocomposites were prepared by melt mixing in a Haake mixer. The average primary particle size of the CaCO₃ nanoparticles was measured to be about 44 nm. The dispersion of the CaCO₃ nanoparticles in PP was good for filler content below 9.2 vol%. Differential scanning calorimetry (DSC) results indicated that the CaCO₃ nanoparticles are a very effective nucleating agent for PP. Tensile tests showed that the modulus of the nanocomposites increased by approximately 85%, while the ultimate stress and strain, as well as yield stress and strain were not much affected by the presence of CaCO₃ nanoparticles. The results of the tensile test can be explained by the presence of the two-counter balancing forces—the reinforcing effect of the CaCO₃ nanoparticles and the decrease in spherulite size of the PP. Izod impact tests suggested that the incorporation of CaCO₃ nanoparticles in PP has significantly increased its impact strength by approximately 300%. J-integral tests showed a dramatic 500% increase in the notched fracture toughness. Micrographs of scanning electron microscopy revealed the absence of spherulitic structure for the PP matrix. In addition, DSC results indicated the presence of a small amount of β phase PP after the addition of the calcium carbonate nanoparticles. We believe that the large number of CaCO₃ nanoparticles can act as stress concentration sites, which can promote cavitation at the particle-polymer boundaries during loading. The cavitation can release the plastic constraints and trigger mass plastic deformation of the matrix, leading to much improved fracture toughness.     

The toughening mechanism of polypropylene/calcium carbonate nanocomposites

The toughening mechanism of polypropylene (PP) filled with calcium carbonate (CaCO₃) nanoparticles is described. In a previous study (Macromolecule 2008;41:9204), we observed that intensive ligament-stretching following debonding of nanoparticles was responsible for the significant improvement in the impact toughness of the annealed PP/CaCO₃ nanocomposites. Furthermore, we hypothesized that strong ligaments, which have high fracture stresses, are needed to stabilize the crack-initiation process and to increase the energy dissipation in the crack-initiation stage. In this study, we used a high-molecular-weight PP to test this hypothesis because strong ligaments could be created from this high-molecular-weight PP. The notched Izod impact strength of the nanocomposites containing the high-molecular-weight PP and 20 wt% CaCO₃ nanoparticles with a monolayer coating of stearic acid was measured to be about 370 J/m, whereas the impact strength of the unfilled PP was 50 J/m. The size of the plastic deformation zone was found to be dependent on the molecular weight of the PP matrix because the strong ligaments of the high-molecular-weight PP enabled the expansion of the plastic deformation zone, leading to a considerable increase in the impact strength. The synergic effect of the high-molecular-weight PP and the monolayer-coated nanoparticles produced nanocomposites with high impact strength, which is much greater than the inherent impact strength of the unfilled polymer. In addition, the effect of the high-molecular-weight PP on the dispersion of the nanoparticles was investigated.     

粉石英/重质碳酸钙复合填料表面改性工艺研究

本文研究了表面改性剂配方、用量、改性时间等对粉石英／重质碳酸钙复合填料表面改性效果的影响，试验得到最佳配方为复合填料：硅烷偶联剂：硬脂酸＝100：0．5：1，并对表面改性剂与粉石英／重质碳酸钙复合填料表面的作用机理进行了探讨。     

国外耐酸碳酸钙之开发

介绍了国外有关耐酸碳酸钙产品的开发和研究进展。     

超细碳酸钙填料在脱丙酮型RTV-1硅橡胶中的应用研究

研究了碳酸钙粒径大小及其在体系中的分散状况对脱丙酮型ＲＴＶ－１硅橡胶性能的影响。结果表明,采用粒径小于０．０８μｍ、表面经脂肪酸处理的超细碳酸钙可制备拉伸强度大于１．３５ＭＰａ,扯断伸长率大于３５７％且具有较好触变性能的脱丙酮型ＲＴＶ－１硅橡胶;混料过程中采用较高的脱水温度易产生碳酸钙密集的聚集体,使硅橡胶拉伸强度和扯断伸长率下降;体系中分散不均匀的聚集体可能容易诱发应力缺陷,是导致硅橡胶断裂的重     

碳酸钙疏水改性及性能表征

采用单一改性剂油酸、硬脂酸、二甲基硅油及复合改性剂对碳酸钙颗粒进行疏水改性。介绍了改性碳酸钙的作用机理。探讨了改性剂种类和加入量对碳酸钙颗粒表面疏水程度的影响,并通过活化度表征疏水程度。采用红外光谱仪表征改性前后碳酸钙的结构,说明改性剂被引入到了碳酸钙颗粒表面上;采用Zeta电位仪测定改性前后碳酸钙随pH变化的Zeta电位,得知改性碳酸钙的Zeta电位受pH影响比较大;采用激光粒度仪测定改性前后碳酸钙的粒径,得知改性碳酸钙比未改性碳酸钙的平均粒径小,且其分散稳定性要优于未改性碳酸钙。该研究也提供了随改性剂种类和加量变化来调整颗粒表面疏水程度的方法,有一定实际意义。     

复合偶联剂改性纳米CaCO3工艺研究

采用正交试验法对钛酸酯和硬脂酸复合改性纳米CaCO3工艺进行了研究,探讨了改性剂用量、乳化温度、乳化时间和保温时间等因素对纳米CaCO3改性的影响,并优化出了最佳操作工艺条件：钛酸酯用量为纳米ca0。3的1,2％(质量分数)、硬脂酸用量为纳米CaCO3 4％(质量分数)、乳化温度70℃、乳化时间90min和保温时间80min。测定了改性纳米CaCO3和未改性纳米CaCO3的活化指数、吸油量、沉降体积以及在邻苯二甲酸二辛酯(DOP)中的粘度,结果表明钛酸酯和硬脂酸复合改性纳米CaCO3活化指数可达99．90％,吸油量降为15．23mL／100g,CaCO3／DOP糊粘度显著降低,亲油性得到显著提高。     

碳酸钙表面改性研究进展

介绍了碳酸钙粉体表面改性的方法——局部反应改性、表面包覆改性、高能表面改性及机械化学改性,对碳酸钙粉体表面改性的发展前景进行了展望。     

Controllable synthesis of calcium carbonate polymorphs at different temperatures

Calcium carbonate with various structures and morphologies were prepared by double injection of the CaCl₂ and NH₄HCO₃ solutions with molar ratio of 1:1 at 30-80 °C. The lamellar vaterite particles, the mixture composed of vaterite, aragonite and calcite, and the aragonite whiskers were formed at 30-40 °C, 50-70 °C and 80 °C, respectively. Thermodynamic calculation showed that the value of [CO₃²⁻]/[Ca²⁺] decreased with the increase of temperature, which may be one of the reasons for the formation of the lamellar vaterite at 30-40 °C and the aragonite whiskers at 80 °C.     

Use of polymeric compatibilizers in polypropylene/calcium carbonate composites

The effects of compatibilizing agents on the mechanical properties, viscoelastic properties, and morphology of polypropylene filled with calcium carbonate composites are investigated. It is found that the use of PP-g-MA and PP-g-AA significantly increases the tensile strength and improves particle dispersion and interfacial adhesion. The higher effect of compatibilization is obtained by using PP-g-MA as a compatibilizer. The results on the dynamic thermomechanical properties, viscoelastic properties, and SEM pictures also support the improved interfacial characteristics. It is also found that there exists a limiting amount of PP-g-MA at about 5% beyond which a further increase in the tensile strength is not obtained. The use of untreated calcium carbonate or SEBS-g-MA does not allow films to be drawn for the purpose of testing.