共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Background: Rosin‐based nucleating agents, as natural products, do not have any toxicity; hence they could be used in the industrial processing of polypropylene for the manufacture of food containers. As a result they have been the subject of considerable scientific interest in the literature. In this paper, the non‐isothermal crystallization behavior, and optical and mechanical properties of isotactic polypropylene (iPP) nucleated with rosin‐based nucleating agents are reported. Polarized optical microscopy, scanning electron microscopy and wide‐angle X‐ray diffraction were used to investigate the morphology and crystal structure of iPP with different rosin‐based nucleators. The effects of a 1:1:1 co‐crystal on the properties of iPP were also investigated. Results: The addition of rosin‐based nucleating agents led to the following changes in properties: (a) shortened crystallization half time, (b) decreased size of iPP crystals, (c) slightly increased crystallinity and (d) increased transparency, gloss, flexural modulus and tensile strength. The shrinkage of nucleated iPPs was similar to that of the blank iPP. Conclusion: Rosin‐based nucleating agents in iPP were shown to be effective for nucleating crystals, reducing their size and causing preferential growth along the b‐axis, but suppressing detectable spherulites. The 1:1:1 co‐crystal was effective at 0.2 wt%, a greater concentration giving little additional improvement. Copyright © 2007 Society of Chemical Industry 相似文献
3.
Eng Pi Chang 《应用聚合物科学杂志》1977,21(4):937-942
A study of the effect of a series of fire retardants upon the crystallization behavior and morphology of polypropylene suggests three categories: (1) “Insolubilized nucleating additives”—these remain insolubilized at the premelting temperature of polypropylene, resulting in very high nucleation density which leads to numerous irresolveable small spherulites. (2) “Solubilized nucleating additives”—these are soluble at the premelting temperature of polypropylene but recrystallize before and/or simultaneously with the crystallization of polypropylene; the subsequent lower nucleation density results in medium-size spherulites of a fairly heterogeneous distribution. (3) “Nonnucleating additives”—these remain solubilized in the polymer matrix throughout the course of crystallization of polypropylene. The nonnucleating nature and low viscosity of these solubilized additives results in large volume-filling spherulites crystallized at a much faster growth than the unfilled polypropylene. 相似文献
4.
The non‐isothermal crystallization behavior, the crystallization kinetics, the crystallization activation energy and the morphology of isotactic polypropylene (iPP) with varying content of β‐nucleating agent were investigated using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The DSC results showed that the Avrami equation modified by Jeziorny and a method developed by Mo and co‐workers could be successfully used to describe the non‐isothermal crystallization process of the nucleated iPPs. The values of n showed that the non‐isothermal crystallization of α‐ and β‐nucleated iPPs corresponded to a tridimensional growth with homogeneous and heterogeneous nucleation, respectively. The values of crystallization rate constant showed that the rate of crystallization decreased for iPPs with the addition of β‐nucleating agent. The crystallization activation energy increased with a small amount (less than 0.1 wt%) of β‐nucleating agent and decreased with higher concentration (more than 0.1 wt%). The changes of crystallization rate, crystallization time and crystallization activation energy of iPPs with varying contents of β‐nucleating agent were mainly determined by the ratio of the content of α‐ and β‐phase in iPP (α‐PP and β‐PP) from the DSC investigation, and the large size and many intercrossing lamellae between boundaries of β‐spherulites for iPPs with small amounts of β‐nucleating agent and the small size and few intercrossing bands among the boundaries of β‐spherulites for iPPs with large amounts of β‐nucleating agent from the SEM examination. Copyright © 2010 Society of Chemical Industry 相似文献
5.
Karl-Heinz Moos 《大分子材料与工程》1983,111(1):165-177
The influence of the variation of the molecular weight, of the mold temperature and of the temperature of the melt during injection molding as well as of the addition of nucleating agents on the morphology and the mechanical properties of injection molded PA 66 samples was studied. The orientation of the needle-shaped phthalocyanine particles, acting as nucleating agents, which took place preferably in the shear zone, gave rise to the formation of row nucleated spherulites. The mechanical properties remained unchanged although the degree of the crystal orientation increased. The addition of a specific nucleating agent for polyamides resulted in a decrease of the elongation to break by 80% and in an increase of the yield strength by 15%. This behaviour can be attributed to the formation of small spherulites having a diameter of about 3?4 μm as compared to the original sample which is characterized by diameters of spherulites of about 30 μm. The observation that the addition of nucleating agents to PA 66 does not lead to a distinct shift in the temperature of the crystallization exotherm in the DSC-experiment indicates that this method is not beyond doubt in determining the nucleating capacity of a nucleating agent with respect to induced changes in the morphology and the mechanical properties. 相似文献
6.
S. Radhakrishnan M. Tapale N. Shah E. Rairkar V. Shirodkar H. P. Natu 《应用聚合物科学杂志》1997,64(7):1247-1253
The structure development and mechanical properties of blow extruded polypropylene containing β-phase nucleating additives was studied. Quinacridone red and cadmium red were both found to nucleate the β phase in polypropylene, the former being a much more efficient nucleator than the latter. The β-phase spherulites formed in the presence of these nucleating agents were small and extensively volume filled, yielding high crystallinity. The modulus increased 2–3 times, elongation at break decreased, and there was a sharp break point without much yield when the β-phase nucleating agents were added as compared to the pure α-phase polypropylene. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1247–1253, 1997 相似文献
7.
The nonisothermal crystallization of Isotactic polypropylene (iPP) containing different concentration of nucleating agent potassium dehydroabietate (DHAA‐K) or sodium dehydroabietate (DHAA‐Na) at the cooling rate of 10°C/min was investigated using differential scanning calorimetry (DSC) together with Jeziorny's method. It was found that the temperature at which the maximum rate of crystallization occurred shifted to a higher region by about 13.7–16.9°C, and the rate of crystallization became faster for iPP with DHAA‐K (PPK) or DHAA‐Na (PPNa) in comparison to the virgin iPP. Avrami exponent for virgin PP, PPK, and PPNa was about 3.1, 2.2, and 2.2, respectively, suggesting the change of the crystal growth mechanism of iPP with the addition of the nucleating agents. The morphology of iPP with and without nucleating agent examined by a cross polarized light microscope indicated that the size of spherulites marginally decreased, which then remained stable with the increase of the concentration of DHAA‐K or DHAA‐Na. The measurements of the optical and mechanical properties of iPP showed that the transparency, gloss, and flexural modulus increased with increasing nucleating agent before its optimal concentration. POLYM. ENG. SCI., 47:889–897, 2007. © 2007 Society of Plastics Engineers 相似文献
8.
Nucleation effects of two sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) were studied by means of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). A nonisothermal crystallization kinetic equation was employed to analyze the crystallization characteristics of iPP with or without the nucleating agents from DSC crystallization thermograms. The equilibrium melting temperature of iPP necessary for the kinetic study was obtained by the extrapolation method to be 209°C. The nonisothermal crystallization kinetic analysis for the unnucleated iPP at different cooling rates was possible by assuming the spherulite growth initiated simultaneously by heterogeneous and homogeneous nucleation. On the other hand, the crystallization kinetics of the nucleated iPP could be described by the heterogeneous nucleation and growth process alone. The addition of the nucleating agents up to their saturation concentrations in iPP increased the crystallization peak temperature by 17°C, and the number of effective nuclei by three orders of magnitude. A high concentration of the nucleating agents caused agglomeration of the agents to lower the number of effective nuclei. 相似文献
9.
The temperature dependence of the nucleation effect of three sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) was studied by means of isothermal crystallization kinetic analysis. Isothermal crystallization thermograms obtained by differential scanning calorimetry (DSC) were analyzed based on the Avrami equation. The Avrami analysis for the nucleated iPP was carried out with DSC data collected to 35% relative crystallinity, and the rate constants were corrected assuming the heterogeneous nucleation and three dimensional growth of iPP spherulites. A semi-empirical equation for the radial growth rate of iPP spherulites was given as a function of temperature and was used to determine the number of effective nuclei at different temperatures. The number of effective nuclei in the nucleated samples was estimated to be 3 × 102 ∽ 105 times larger than that in the neat iPP. The logarithmic numbers of the effective nuclei decreased linearly with decreasing degree of supercooling in the range of crystallization temperatures tested. The temperature dependence of the effect of the nucleating agents on iPP crystallization was given quantitatively in terms of the deactivation factor defined as a fraction of the particles that are active at a particular temperature but inert at the temperature one degree higher. The nucleation activity and its temperature dependence are considered to be cooperative effects of many factors, including the dispersion and the physical or chemical nature of the agent as well as the interaction between the agent and the polymer. It is suggested that the temperature dependence of the effect of a nucleating agent should be treated as a characteristic of a given polymer/ nucleating agent mixture. 相似文献
10.
Polypropylene/organoclay nanocomposites containing nucleating agents, viz., aluminum hydroxybis[2,2-methylenebis(4,6-di-tert-butylphenyl) phosphate (NA21) and 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (Millad 3988), were prepared by direct melt
intercalation in a twin-screw extruder. Nucleating agents were added to polypropylene during compounding and their effect
on the properties of the nanocomposites was studied. X-ray diffraction (XRD) and transmission electron microscopy (TEM) exhibited
clay layers to be intercalated and partially exfoliated. The expansion of inter-gallery distance of the clay layers was governed
by the interaction between polypropylene, compatibilizer, and different nucleating agents. Thermogravimetric analysis (TGA)
and differential scanning calorimetry (DSC) indicated higher thermal stability and crystallization temperature for nanocomposites
compared to virgin polymer. Even a small addition of the nanoscale filler with 0.2% nucleating agents was found to promote
concurrently several PP material properties, including improved tensile characteristics, higher Young’s modulus, increased
thermal stability and rate of crystallization. 相似文献
11.
12.
Ahmed Mohamed El-Hadi 《Polymer Bulletin》2014,71(6):1449-1470
PHB is a thermoplastic biopolymer produced by fermentation of renewable resources. Secondary crystallization during storage leading to an increased degree of crystallinity is a principal reason of PHB brittleness. In addition, pure PHB has no residues of catalysts, meaning low nucleation density and slow crystallization rates, leading to the formation of large spherulites with cracks and brittleness. To overcome the brittleness of PHB, polymer composites based on PHB, plasticizers, and nano-clays A and B were prepared by solvent casting. The addition of plasticizer decreases T g from 5 to ?13 °C in all composites. Furthermore, the addition of nano-clays acts as a nucleating agent to PHB. The effect of nano-clays A and B on spherulites morphology, thermal behavior, and crystal structure of PHB composites were tested by several techniques. Differential scanning calorimetry analysis shows that the addition of nano-clay A does not change the crystallization temperature and the crystallization half-time (t 1/2) of the PHB matrix but that nano-clay B accelerates the crystallization process. Thermogravimetric analysis revealed an increase in thermal stability of composites containing nano-clay B. Polarized optical microscopy showed that nano-clays serve as nucleating agents in PHB matrix. Therefore, the spherulites become smaller and the nuclei density increases at the selected crystallization temperature, compared to pure PHB. 相似文献
13.
Organic nucleating agents and inorganic nanoparticles, as well as their hybrid composites, affect the crystallization temperature and morphology of the monoclinic α-form of isotactic polypropylene (iPP). Techniques such as differential scanning calorimetry, hot-stage optical microscopy with cross polars, wide angle X-ray diffraction, and transmission electron microscopy were employed. Nanoparticles of zinc oxide function as efficient supports for 1,3,5-benzene tricarboxylic-(N-2-methylcyclohexyl)triamine because the temperature at which the maximum rate of iPP crystallization occurs during 10 °C/min cooling from the molten state increases from 111 °C for the pure polymer to 125 °C at low concentrations of this hybrid nucleating agent. In the absence of zinc oxide, 0.06 wt% of this aliphatic triamine recrystallizes near 165 °C and increases the crystallization temperature of iPP by 7 °C, relative to the pure polymer. Fluorinated aromatic triamines, such as 1,3,5-benzene tricaboxylic-(N-4-fluorophenyl)triamine, are weak nucleating agents that reduce spherulite size in isotactic polypropylene but only increase the crystallization temperature marginally when the polymer is cooled from the molten state. Both micro- and nanoparticles of zinc oxide reduce spherulite size in isotactic polypropylene, but smaller spherulites are observed when the inorganic nanoparticles exhibit dimensions on the order of 40-150 nm relative to micron-size particles. In contrast, 0.06 wt% of the aliphatic triamine in iPP yields a distorted birefringent texture under cross polars that is not spherulitic. Non-spherulitic birefringent textures in iPP are also observed when the aliphatic triamine nucleating agent is coated onto micro- or nanoparticles of zinc oxide. This study demonstrates that the nonisothermal crystallization temperature of isotactic polypropylene increases by an additional 7 °C when an aliphatic triamine is distributed efficiently within the polymeric matrix by coating this nucleating agent onto zinc oxide nanoparticles. 相似文献
14.
Crystallization morphologies and non-isothermal crystallization kinetics of isotactic polypropylene modified by α/β compounded nucleating agents 下载免费PDF全文
采用偏光显微镜(POM)及示差扫描量热(DSC)法考察了3种α/β复合成核剂NA40/NABW、NA40/HHPA-Ba、NA40/PA-03对成核等规聚丙烯(iPP)的结晶形态及非等温结晶动力学的影响。对成核iPP结晶形态的研究结果表明:α/β复合成核剂的加入能够减小iPP的球晶尺寸。影响α/β复合成核剂成核iPP结晶形态的主要因素是ΔTCp(ΔTCp为成核iPP结晶峰值温度与iPP结晶峰值温度的差值),即复合体系中ΔTCp较大的成核剂在iPP结晶过程中起主导作用,最终的结晶形态与单独添加这一成核剂时iPP的结晶形态相类似;当两种成核剂的ΔTCp接近相同时,两者竞争成核,成核iPP的结晶形态表现为两种成核剂共同作用的结果。因此,通过改变α/β复合成核剂的复合比例即改变两种成核剂的添加浓度,进而改变其ΔTCp,可以得到结晶形态完全不同的iPP。采用Caze法对非等温动力学进行了研究,结果表明:添加α/β复合成核剂能够提高iPP的结晶温度,缩短半结晶时间。复合成核剂成核iPP的结晶行为也同样受成核剂ΔTCp的影响,复合成核iPP的Avrami指数接近于复合体系中ΔTCp较大的成核剂单独添加时iPP的Avrami指数。 相似文献
15.
Effects of additives on non-isothermal crystallization kinetics and morphology of isotactic polypropylene 总被引:1,自引:1,他引:0
In this study, effects of commercial additives such as antioxidant and stabilizer on the non-isothermal crystallization kinetics
of isotactic polypropylene without nucleating agents were investigated by differential scanning calorimetry (DSC) method.
Kinetic parameters by Osawa, Avrami and Liu-Mo models and apparent activation energy of the crystallization by Kissinger model
were calculated. A polarized optical microscope was also used to observe crystalline morphology of the polypropylene samples
crystallized at different cooling rates. On the contrary rate inducing effects of the nucleating agents on the crystallization
kinetics of the polypropylene, interestingly, it was found that such types of commercial additives reduced the overall crystallization
rate of the polypropylene. Based on the crystallization kinetics and morphology of the samples, it was observed that commercial
additives inhibit the chain diffusion toward the growing crystal faces thus slow the crystal growth rate. Furthermore, calculated
nucleation activity (ϕ) for the additives showed that they do not act as effective nucleating agents. It was found that the crystallization activation
energy of additive-free sample was higher than that of the sample which has commercial additives. Activation energies were
found to be 233.6 and 276.7 kJ mol−1 for the PP-1 and PP-2, respectively. Kinetic results also show importance of using of nucleating agents to increase the crystallization
rate of polypropylene by increasing the nucleation and thus overall crystallization rate during polypropylene processing operations
(esp. for a fast processing cycle in injection molding). 相似文献
16.
In this research, the effects of different kinds of nucleating agents on the crystallization and mechanical properties of polyoxymethylene (POM) were studied, including inorganic, organic, and polymer nucleating agents and their compounds. These properties showed that nanoCaCO3, sorbitol derivative TMB-5, polyamide PA-4, and compound C-1/polyamide (PA)-4 can make spherulites of POM finer and more perfect, and effectively improve its notched impact toughness, in which the compound C-1/PA-4 displayed more remarkable nucleation effect. The study on the nonisothermal crystallization of POM showed that the crystallization temperature and crystallization growth rate of POM increased when C-1/PA-4 was added. The isothermal crystallization kinetics were also analyzed by the Avrami equation. The addition of C-1/PA-4 can increase the values of the Avrami exponent (n) and crystallization rate constant (k), and reduce the half-time of isothermal crystallization, t1/2, and the time corresponding to the maximum rate of crystallization, tP, indicating its remarkable nucleating effect on POM. 相似文献
17.
合成了两种具有相似化学结构的聚丙烯(iPP)α晶型成核剂二环[2.2.1]庚⁃5⁃烯⁃2,3⁃二羧酸钠(NA1)和二环[2.2.1]庚烷⁃2,3⁃二羧酸钠(NA2),研究了其在iPP中的成核效果。首先,利用差示扫描量热仪(DSC)和偏光显微镜(PLM)分别考察了两种成核剂对iPP结晶行为的影响。结果表明,当NA1和NA2的含量为0.3 %(质量分数,下同)时,iPP的结晶峰值温度分别提升了14.5 ℃和16.0 ℃。同时,两种成核剂都能够明显细化iPP球晶尺寸。其次,利用广角X射线衍射仪(WXAD)对成核iPP进行了表征,两种成核剂都诱导iPP产生了α晶型,说明均为α晶型成核剂。然后,对成核iPP的力学性能进行了表征。结果表明,随着两种成核剂用量的增加,iPP的拉伸强度和弯曲模量呈现先升高后平稳的趋势。当NA1和NA2含量为0.05 %时,成核iPP的拉伸强度较纯iPP分别提升了4.6 %和8.6 %,弯曲模量分别提升了8.2 %和21.7 %;冲击强度基本保持不变。 相似文献
18.
Effect of aliphatic diacyl adipic dihydrazides on the crystallization of poly(lactic acid) 下载免费PDF全文
A series of aliphatic diacyl adipic dihydrazides (ADHs) with different alkyl moieties were synthesized by the reaction between adipic dihydrazide and acyl chloride. Then these ADHs were solution blended with PLA respectively and were evaluated as nucleating agents. Through the investigation of nonisothermal and isothermal crystallization, it was found that both the crystallization rate and the crystallinity of PLA could be enhanced by adding only 1 wt % of ADHs. Especially for ADH‐Oc (ADH‐Octyl), the crystallization rate of PLA increased about 4 times at 105°C. Optical morphology showed that and the size of PLA spherulites decreased and the nucleation density increased with the existence of ADH‐Oc. Meanwhile, the crystal structure of PLA were not discerniblly affected after the addition of ADHs as found by wide‐angle X‐ray diffraction. Thus, this study suggested these ADHs compounds are simple and potential nucleating agents to enhance crystallization ability of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42028. 相似文献
19.
采用偏光显微镜(POM)及示差扫描量热(DSC)法考察了3种α/β复合成核剂NA40/NABW、NA40/HHPA-Ba、NA40/PA-03对成核等规聚丙烯(iPP)的结晶形态及非等温结晶动力学的影响。对成核iPP结晶形态的研究结果表明:α/β复合成核剂的加入能够减小iPP的球晶尺寸。影响α/β复合成核剂成核iPP结晶形态的主要因素是ΔTCp(ΔTCp为成核iPP结晶峰值温度与iPP结晶峰值温度的差值),即复合体系中ΔTCp较大的成核剂在iPP结晶过程中起主导作用,最终的结晶形态与单独添加这一成核剂时iPP的结晶形态相类似;当两种成核剂的ΔTCp接近相同时,两者竞争成核,成核iPP的结晶形态表现为两种成核剂共同作用的结果。因此,通过改变α/β复合成核剂的复合比例即改变两种成核剂的添加浓度,进而改变其ΔTCp,可以得到结晶形态完全不同的iPP。采用Caze法对非等温动力学进行了研究,结果表明:添加α/β复合成核剂能够提高iPP的结晶温度,缩短半结晶时间。复合成核剂成核iPP的结晶行为也同样受成核剂ΔTCp的影响,复合成核iPP的Avrami指数接近于复合体系中ΔTCp较大的成核剂单独添加时iPP的Avrami指数。 相似文献
20.
以单丙烯酸酯液晶单体(RLC)为成核剂,通过共混反应法对等规聚丙烯(iPP)进行改性,制备含β晶型的聚丙烯产品(β-iPP)。首先介绍了β-iPP的制备工艺,然后通过偏光显微镜、广角X射线衍射对纯iPP、iPP/RLC共混物的球晶结构进行了分析;最后通过X射线衍射、差示扫描量热分析等测试方法研究共混物的结晶结构、结晶行为和热性能。结果表明,液晶成核剂RLC能够诱导iPP生成β晶型;制备β-iPP的最佳工艺条件是RLC含量为0.5 %(质量分数,下同),结晶温度为110 ℃;β晶型相比于α晶型处于热力学亚稳态,在升温过程中,会发生β晶向α晶的转变,但较高的升温速率会抑制这一转变。 相似文献