A novel highly efficient β‐nucleating agent for polypropylene using nano‐CaCO3 as a support

In order to increase the isotactic content of β‐nucleated polypropylene (β‐iPP) and decrease the cost of its production, the investigation and development of novel highly efficient β‐nucleators are important issues. Nano‐CaCO₃ was used as a support to prepare a supported β‐nucleator, nano‐CaCO₃‐supported calcium pimelate. Fourier transform infrared spectral analysis shows that an in situ chemical reaction takes place between nano‐CaCO₃ and pimelic acid. Differential scanning calorimetry results indicate that the crystallization and melting temperatures of β‐phase in supported β‐nucleator‐nucleated iPP are higher than those of calcium pimelate‐nucleated iPP. The β‐nucleating ability of the supported β‐nucleator is little influenced by the cooling rate and crystallization temperature over a wide range. The decreased content of pimelic acid in the supported β‐nucleator slightly decreases the crystallization temperature of iPP but it has no influence on the content of β‐phase in nucleated iPP. A novel supported β‐nucleator has been successfully synthesized via pimelic acid supported on the surface of CaCO₃. The crystallization temperature of iPP and melting temperature of β‐phase in iPP nucleated using the supported β‐nucleator are higher than those of iPP nucleated using calcium pimelate. The concept of a supported nucleator will provide a new way to increase the efficiency of polymer additives and to decrease the amounts of them that need to be used by using nanoparticles as supports. Copyright © 2010 Society of Chemical Industry     

Influence of different β‐nucleating agent on crystallization behavior,morphology, and melting characteristic of multiwalled carbon nanotube‐filled isotactic polypropylene nanocomposites

To obtain isotactic polypropylene (iPP) nanocomposites with high β‐crystal content, TMB5, calcium pimelate and calcium pimelate supported on the surface of nano‐CaCO₃ were used as β‐nucleating agent and MWCNT filled β‐nucleated iPP nanocomposites were prepared. The effect of different β‐nucleating agent and MWCNT on the crystallization behavior and morphology, melting characteristic and β‐crystal content of β‐nucleated iPP nanocomposites were investigated by DSC, XRD and POM. The results indicated that addition of MWCNT increased the crystallization temperature of iPP and MWCNT filled iPP nanocomposites mainly formed α‐crystal. The β‐nucleating agent can induce the formation of β‐crystal in MWCNT filled iPP nanocomposites. The β‐nucleating ability and β‐crystal content in MWCNT filled β‐nucleated iPP nanocomposites decreased with increasing MWCNT content and increased with increasing β‐nucleating agent content due to the nucleation competition between MWCNT and β‐nucleating agents. It is found that the calcium pimelate supported on the surface of inorganic particles as β‐nucleating agent has stronger heterogeneous β‐nucleation than calcium pimelate and TMB5. The MWCNT filled iPP nanocomposites with high β‐crystal content can be obtained by supported β‐nucleating agent. POLYM. COMPOS., 36:635–643, 2015. © 2014 Society of Plastics Engineers     

Pimelic acid-based nucleating agents for hexagonal crystalline polypropylene

Isotactic polypropylene (PP) resin was doped with pimelic acid, sodium pimelate, and calcium pimelate to stimulate the growth of hexagonal crystalline polypropylene (β-PP). The doped resin was crystallized in a differential scanning calorimeter (DSC) and during compression molding and injection molding. The effect of the additives on the formation of β-PP was examined using DSC and wide angle X-ray scattering (WAXS). Pimelic acid alone was found ineffective while the pimelates induced 64% to 90% of β-growth depending on the nucleating agent system and crystallization condition. In particular, the pimelic acid/calcium stearate system produced a more consistent and higher yield of β-PP. This was attributed to finer particle size and better dispersion of the nucleating agent.     

不同方法制备的庚二酸钙对改性聚丙烯结晶和熔融行为的影响

分别采用复分解反应法（D-CaPi）、中和反应法（N-CaPi）以及硬脂酸钙与庚二酸共混法（S-CaPi）3种不同方法制备了庚二酸钙,研究了3种庚二酸钙对聚丙烯结晶和熔融行为的影响。利用傅里叶变换红外光谱仪和差示扫描量热仪测试了庚二酸钙的结构及庚二酸钙改性聚丙烯的结晶和熔融行为。结果表明,3种制备方法都可以使庚二酸完全反应得到庚二酸钙;3种庚二酸钙对聚丙烯均有成核能力,其中D-CaPi和N-CaPi使聚丙烯结晶峰温度提高了约4.9 ℃,S-CaPi使聚丙烯结晶峰温度提高了6.5 ℃,同时,S-CaPi对于聚丙烯β晶型得诱导能力明显优于D-CaPi和N-CaPi,可使改性聚丙烯中的β晶型相对含量达到84.5 %。     

β‐Nucleation of pimelic acid supported on metal oxides in isotactic polypropylene

To investigate the nucleation of metal pimelate for isotactic polypropylene (iPP) crystallization, iPP filled with a series of metal oxides with and without metal pimelate on their surface was prepared. There was a chemical reaction between pimelic acid (PA) and metal oxides MgO, CaO, BaO or ZnO, but not TiO₂. The corresponding metal pimelate formed by the chemical reaction between PA and MgO, CaO, BaO or ZnO had a different influence on the crystallization behavior and melting characteristics of iPP. Addition of metal oxides increased the crystallization temperature of iPP and mainly formed α‐phase due to the heterogeneous α‐nucleation of metal oxides. The α‐nucleation of CaO could be easily changed into β‐nucleation using CaO‐supported PA, and 90.1% β‐phase was obtained. The β‐nucleation of BaO could be markedly enhanced by barium pimelate formed using supported PA. However, no β‐phase was observed for iPP filled with MgO‐ or ZnO‐supported PA. The various metal oxides with supported PA had a different influence on the crystallization behavior and melting characteristics of iPP due to the different structure of metal pimelate formed by chemical reaction between PA and the metal oxides. Copyright © 2012 Society of Chemical Industry     

Effect of carbon nanotube‐supported β nucleating agent on the thermal properties,morphology, and mechanical properties of polyamide 6/isotactic polypropylene blends

A new kind of β nucleating agent, multi‐wall carbon nanotube (MWCNT)‐supported calcium pimelate was introduced into polyamide 6 (PA 6)/isotactic polypropylene (iPP; 10/90 by weight) blend and the thermal properties, morphology, and mechanical properties were investigated. The results showed that β‐iPP appeared at low content of MWCNT‐supported calcium pimelate which surmounted the α‐nucleating effect of PA 6 for iPP, and the content of β‐iPP increased with increasing content of MWCNT‐supported calcium pimelate. The impact strength, elongation at break, and flexural modulus were improved with increasing content of MWCNT‐supported calcium pimelate without significantly deteriorating the tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A novel β‐nucleating agent for isotactic polypropylene

The nucleating ability of p‐cyclohexylamide carboxybenzene (β‐NA) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry, X‐ray diffraction, polarized optical microscopy and scanning electron microscopy. β‐NA is identified to have dual nucleating ability for α‐iPP and β‐iPP under appropriate kinetic conditions. The formation of β‐iPP is dependent on the content of β‐NA. The content of β‐phase can reach as high as 96.96% with the addition of only 0.05 wt% β‐NA. Under non‐isothermal crystallization the content of β‐iPP increases with increasing cooling rate. The maximum β‐crystal content is obtained at a cooling rate of 40 °C min^–1. The supermolecular structure of the β‐iPP is identified as a leaf‐like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β‐NA. Under isothermal crystallization β‐crystals can be formed in the temperature range 80–140 °C. The content of β‐crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry     

辛二酸盐成核改性等规聚丙烯的研究

采用DSC、WAXD、PLM等分析手段研究了辛二酸和辛二酸盐对等规聚丙(烯iPP)结晶行为的影响。结果表明:辛二酸、辛二酸锂、辛二酸钠、辛二酸钾、辛二酸镁、辛二酸钡和辛二酸锌都不是β晶成核剂,辛二酸锶和辛二酸镉是弱β晶成核剂,辛二酸钙是强β晶成核剂。通过分析结晶温度发现,辛二酸和辛二酸盐对iPP成核能力的大小顺序为:辛二酸>辛二酸钙>辛二酸镁>辛二酸锌>辛二酸钾>辛二酸镉>辛二酸钡>辛二酸钠>辛二酸锶>辛二酸锂。     

Crystallization behavior and crystallization kinetic studies of isotactic polypropylene modified by long‐chain branching polypropylene

In this article, we discuss the crystallization behavior and crystallization kinetics of isotactic polypropylene (iPP) modified by long‐chain‐branching (LCB) high‐melt‐strength iPP over a wide composition range, that is, LCB‐iPP from 10 to 50 wt %. Over the entire range we investigated, the presence of LCB‐iPP accelerated crystallization in both the isothermal crystallization process and nonisothermal crystallization process, even when the LCB‐iPP content was as low as 10%, and both crystallization processes were enhanced more significantly as the LCB‐iPP content increased. Hoffman–Lauritzen theory analysis revealed that the fold‐free energy decreased effectively with the occurrence of the LCB structure, although the growth rate of spherulites was depressed, as shown by polarized optical microscopy. Meanwhile, the regime III–regime II transition temperature was about 15° higher for all of the LCB‐iPP compositions than that of iPP because the LCB structure reduced the mobility of the polypropylene chains. Furthermore, the γ‐form crystal structure was favored by LCB compared to the β form, which was supported by wide‐angle X‐ray diffraction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Highly active thermally stable β‐nucleating agents for isotactic polypropylene

Calcium salts of suberic (Ca‐Sub) and pimelic (Ca‐Pim) acids were synthesized and implemented as in different grades of isotactic polypropylene (iPP). Propylene homopolymer, as well as random and block copolymers containing these additives, crystallized iPP into pure or nearly pure β modification in the isothermal and nonisothermal crystallization experiments. Recently, Ca‐Sub proved to be the most effective β‐nucleating agent of iPP. The Ca‐Sub nucleating agent widens the upper crystallization temperature range of pure β‐iPP formation up to 140°C. In this study the effect of the these additives on the crystallization, melting characteristics, and structure of the PP were studied. The degree of crystallinity of β‐iPP was markedly higher than that of α‐iPP. A widening in the melting peak of the samples crystallized in a high temperature range was first observed and discussed in regard to literature results of the same phenomenon for α‐iPP. The morphology of the β‐iPP samples was revealed by scanning electron microscopy. Independent of the type of polymer or nucleating agent, hedritic structures were found in the early stages of growth of the β‐spherulites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2357–2368, 1999     

Calcium dicarboxylates nucleation of β‐polypropylene

Seven dicarboxylates of calcium were synthesized. The effect of dicarboxylate on the formation of β‐form polypropylene was investigated by X‐ray diffraction. Calcium pimelate, calcium suberate, calcium phthalate, and calcium terephthalate have been found to be an effective β‐nucleator. The K_x values of the isotatic propylene samples with 0.5 wt % of the nucleators above are 0.95, 0.96, 0.93, and 0.62, respectively. Calcium succinate, calcium adipate, and calcium sebacate behave invalidly on the nucleating of the β‐phase. We conducted an investigation on the affect of particle shape, crystal form, and crystallinity upon the level of the β‐form. The X‐ray diffraction of the effective nucleators reveals a common character that their first reflection locate at the d‐spacing between 10 to 13 Å, indicating structural similarity of the nucleators with β‐polypropylene. The nucleation mechanism is explained by the cooperative effect of the nonpolar and polar part of nucleating agents in the crystallization of polypropylene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 633–638, 2002     

Effects of mineral additives on the β‐crystalline form of isotactic polypropylene

Nineteen kinds of minerals, alone and in bicomponent mixtures with LaC (a mixed ternary complex of trivalent lanthanum stearate and stearin), were added to isotactic polypropylene (iPP). The influences of the minerals on the crystallographic forms of iPP were investigated. A wide‐angle X‐ray diffraction examination demonstrated that no mineral or LaC acting alone could induce the occurrence of the hexagonal β‐form, whereas the bicomponent mixtures could when the mineral was a calcium compound or contained calcium compounds, whether the calcium compounds had a hexagonal crystallographic form or not. We surmise that the actual β‐iPP substrate in such a system might be some binuclear complexes of calcium and rare earth elements with some specific ligands. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1742–1748, 2002     

Effect of Calcium Salts of Glutaric Acid and Pimelic Acid on the Formation of β Crystalline Form in Isotactic Polypropylene

The effect of calcium glutarate (Cagt) and calcium pimelate (Capt) on the formation of β crystalline form in isotactic polypropylene (iPP) after isothermal crystallization at 130°C for 30 min has been investigated. The maximum K_WAXD and K_DSC values were 31.97% and 38.06%, respectively, for iPP doped with 0.2 wt.% Cagt. The maximum values of K_WAXD and K_DSC were 73.60% and 68.44% for iPP doped with 0.3 wt.% and 0.15 wt.% Capt, respectively. The crystal size of iPP doped with Capt is finer than that of iPP doped with Cagt. It is shown that the β nucleation ability of Capt is superior to that of Cagt. The difference in the β nucleation ability between Cagt and Capt is explained by the structural difference of the nucleators with β-iPP.     

β成核剂对抗冲聚丙烯共聚物的结晶和力学性能研究

分别用α晶型成核剂和β晶型成核剂对抗冲聚丙烯共聚物（iPP）的结晶和力学性能进行研究,并用偏光显微镜（POM）、广角X射线衍射仪（WAXD）和差示扫描量热仪（DSC）对其进行了详细的表征。结果表明,α和β成核剂使iPP的起始结晶温度（ton）提高15.3℃和12.7℃,结晶峰温度（tp）提高17℃和13.7℃,结晶速率加快。两种成核剂都能使球晶细化,使结晶更加均匀化、规整化,从而使结晶度增加。α成核剂（TMA-3）使iPP的拉伸强度、冲击强度和断裂伸长率分别提高到23.43MPa、22.27kJ/m2和788%;β成核剂因主要是改变球晶的形态,形成与α球晶完全不同的β晶型,使iPP的拉伸强度、冲击强度和断裂伸长率的提高比α成核剂显著,分别达到24MPa、32.81kJ/m2和861%。     

Effects of La3+‐containing additive on crystalline characteristics of isotactic polypropylene

The influence of a mixed additive of lanthanum stearate and stearic acid on the crystalline characteristics of isotactic polypropylene (iPP) has been investigated. The results of the wide‐angle X‐ray diffraction (WAXD) measurements and the melting behaviour examination by differential scanning calorimetry (DSC) show that the additive might induce a high proportion of β‐form and act as a β‐form nucleating agent. The relative content of β‐form estimated by WAXD is 33.1% in a PP containing 2.5% (by weight) of the additive. Isothermal crystallization at 130 °C, examined by DSC, reveals that the additive considerably accelerates the overall rate of crystallization: the half crystallization period t_1/2, decreases from 11.7 min for pure PP to 7.3 min for PP containing 2.5% of the additive. However, the additive has no obvious influence on the nucleation mechanism and crystal growth mode. Polarized light microscopy (POM) examinations indicate that the addition of the additive to PP causes spherulites to become much finer. © 2003 Society of Chemical Industry     

辛二酸/硬脂酸钙双组分成核剂对等规聚丙烯中β晶生成的影响

研究了在120 ℃等温结晶30 min 的条件下,辛二酸/硬脂酸钙双组分成核剂对等规聚丙烯中β晶含量的影响。当加入0.15 %的辛二酸时,等规聚丙烯的β晶消失。固定辛二酸含量为0.15 %、硬脂酸钙含量超过0.525 %时,等规聚丙烯中又开始出现β晶,当硬脂酸钙含量为0.675 %时,β晶含量达到最大值。红外分析表明,辛二酸和硬脂酸钙在双螺杆挤出机中发生原位化学反应,生成高效成核剂辛二酸钙。     

Influence of a novel β‐nucleating agent on the structure,morphology, and nonisothermal crystallization behavior of isotactic polypropylene

The crystalline structure, morphology, and nonisothermal crystallization behavior of isotactic polypropylene (iPP) with and without a novel rare earth‐containing β‐nucleating agent (WBG) were investigated with wide‐angle X‐ray diffraction, polar optical microscopy, and differential scanning calorimetry. WBG could induce the formation of the β form, and a higher proportion of the β form could be obtained by the combined effect of the optimum WBG concentration and a lower cooling rate. The content of the β form could reach more than 0.90 in a 0.08 wt % WBG nucleated sample at cooling rates lower than 5°C/min. Polar optical microscopy showed that WBG led to substantial changes in both the morphological development and crystallization process of iPP. At all the studied cooling rates, the temperature at which the maximum rate of crystallization occurred was increased by 8–11°C in the presence of the nucleating agent. An analysis of the nonisothermal crystallization kinetics also revealed that the introduction of WBG significantly shortened both the apparent incubation period for crystallization and the overall crystallization time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Different β nucleants and the resultant microstructural,fracture, and tensile properties for filled and unfilled ISO polypropylene

This article explores the use of two β nucleants to improve the fracture behavior of filled and unfilled homo‐polypropylene (PP). The first was based upon an organic quinacridone, whereas the second was based upon the inorganic calcium pimelate. Formulations containing various concentrations of nucleant were prepared using single screw extrusion and then characterized by X‐ray diffraction, differential scanning calorimetry (DSC), Izod impact strength, and tensile testing. The quinacridone nucleating agent produced higher levels of β crystallinity and better improvement in strain to failure, whereas the calcium pimelate imparted greater improvement in impact strength regardless of whether the PP was filled or unfilled. No direct relationship between β crystallinity and fracture properties was observed though synergistic enhancement in impact strength was evident. By varying the concentration of calcium carbonate in the calcium pimelate from 10 : 1, 5 : 1, 2 : 1, and 1 : 1 weight composition of calcium carbonate to pimelic acid, similar property enhancements were achieved regardless of composition although the 10 : 1 sample did produce superior elongation to break. The importance of cooling rate on microstructure within each sample was explored via a through the thickness study using DSC and nano‐indenting methods. Variations in the β content through the thickness were related to cooling and found to be independent of sample composition and processing. Elastic properties varied inversely with β content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of TMB-5 on dispersion of MWCNTs in iPP and crystallization of β-nucleated iPP/MWCNTs composites

In this work, multiwall-carbon-nanotubes (MWCNTs), β nucleating agent(TMB-5) and isotactic polypropylene(iPP) were mixed to prepare MWCNTs/iPP composites, which were processed by a corotating twin screw extruder at 270 °C. MWCNTs at 0 wt%, 0.05 wt%, 0.3 wt%, 1 wt%, 2 wt% and 3 wt% were added into the composites respectively and the concentration of TMB-5 was 0.3 wt% consistently. Polarized light microscopy (POM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and Wide-angle X-ray diffraction (WAXD) were used to study the dispersion of MWCNTs in the β-Nucleated iPP and the crystallization of the composites. SEM and TEM graphs showed that MWCNTs dispersed individually in the iPP matrix when TMB-5 was added in the composites. In the contrast, there were many aggregates of MWCNTs in iPP matrix without TMB-5. DSC and WAXD results indicate that TMB-5 and individual MWCNTs have a synergistic effect on inducing the formation of β crystals. However, with the content of MWCNTs increasing in the composites, β crystal content decreased and α crystal content increased, which indicated that MWCNTs aggregating in the iPP matrix acted as α nucleating agent restricting the formation of β crystals and the effect of TMB-5 on dispersion became limited at a relatively high MWCNTs content.     

Structural characterization of α‐ and β‐nucleated isotactic polypropylene

Modification of isotactic polypropylene (iPP) with two nucleation agents, namely 1,3:24‐bis(3,4‐dimethylobenzylideno) sorbitol (DMDBS) (α‐nucleator) and N, N′‐dicyclohexylo‐2,6‐naphthaleno dicarboxy amide (NJ) (β‐nucleator), leads to significant changes of the structure, morphology and properties. Both nucleating agents cause an increase in the crystallization temperature. The efficiency determined in a self‐nucleation test is 73.4 % for DMDBS and 55.9 % for NJ. The modification with NJ induces the creation of the hexagonal β‐form of iPP. The addition of DMDBS lowers the haze of iPP while the presence of NJ increases the haze. Copyright © 2004 Society of Chemical Industry