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1.
N,N,N′‐Tris(1H‐benzotriazole) trimesinic acid acethydrazide (BD) was synthesized from 1H‐benzotriazole acetohydrazide and trischloride to serve as an organic nucleating agent for the crystallization of poly(l ‐lactic acid) (PLLA). First, the thermogravimetric analysis of BD exhibited a high thermal decomposition temperature; this indicated that BD maybe used as a heterogeneous nucleating agent of PLLA. Then, the effect of BD on the crystallization and melting behavior of PLLA was investigated through differential scanning calorimetry, depolarized light intensity measurements, and wide‐angle X‐ray diffraction. The appearance of a nonisothermal crystallization peak and increases in the glass‐transition temperature and the intensity of the diffraction peak suggested that the presence of BD accelerated the overall PLLA crystallization. Upon cooling at a rate of 1°C/min, the addition of just 0.5 wt % BD to PLLA increased the onset crystallization temperature from 101.4 to 111.3°C, and the nonisothermal crystallization enthalpy increased from 0.1 to 38.6 J/g. The isothermal crystallization behavior showed that the crystallization half‐time of PLLA with 0.5 wt % BD (PLLA/0.5% BD) decreased from 49.9 to 1.1 min at 105°C. However, the equilibrium melting point of PLLA/0.5% BD was lower than that of the pristine PLLA; this resulted from the increasing nucleating density of PLLA. The melting behavior of PLLA/0.5% BD further confirmed that BD improved the crystallization of PLLA, and the double‐melting peaks of PLLA/0.5% BD were assigned to melting–recrystallization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42402.  相似文献   

2.
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  相似文献   

3.
Nucleation effects of 2,2′‐methylene‐bis (4,6‐di‐tert‐butylphenyl) phosphate metal salts as a nucleating agent for isotactic polypropylene (iPP) were investigated with differential scanning calorimeter and polarized optical microscope, and their effects on mechanical, optical, and heat resistance properties of iPP were also studied. The results showed that monovalent metal salts of substituted aromatic heterocyclic phosphate such as sodium salt, lithium salt, and potassium salt had a good performance. With 0.2 wt % of sodium salt, lithium salt, or potassium salt incorporated into iPP, the crystallization peak temperature of iPP could be increased by 13.5, 13.6, and 15.0°C, respectively; the mass fraction of crystallinity of iPP could be increased by about 5%; and crystallization rate was enhanced increasingly. Meanwhile the tensile strength and flexural modulus of iPP could be increased by about 10 and 30%, respectively, and the clarity and heat distortion temperature of iPP could also be improved significantly. But bivalent and trivalent metal salts of substituted aromatic heterocyclic phosphate had little effect on properties of iPP. Meanwhile the morphology study showed that the addition of monovalent sodium salt could decrease the spherulite size of iPP significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4868–4874, 2006  相似文献   

4.
The effect of nucleating agents on the crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was studied. A differential scanning calorimeter was used to monitor the energy of the crystallization process from the melt and melting behavior. During the crystallization process from the melt, nucleating agent led to an increase in crystallization temperature (Tc) of PHBV compared with that for plain PHBV (without nucleating agent). The melting temperature of PHBV changed little with addition of nucleating agent. However, the areas of two melting peaks changed considerably with added nucleating agent. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of nucleating agent caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation and growth of the PHB crystals. The equilibrium melting temperature of PHBV was determined as 187°C. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2145–2152, 2002  相似文献   

5.
The nucleation ability of isotactic poly(propylene) (iPP) to ammonium 2,2′‐methylene‐bis‐(4,6‐di‐t‐butylphenylene) phosphate (An) was investigated in the present work comparing with sodium 2,2′‐methylene‐bis‐(4,6‐di‐t‐butylphenylene) phosphate (NA‐11). Scanning electron microscope (SEM) revealed the crystalline morphology of both An and NA‐11 with planar surface characteristics. The observation of the fracture surface of nucleation iPP samples by SEM showed An particles were dispersed uniformly in polymer and had a better compatibility with iPP matrix than NA‐11 particles. Differential scanning calorimeter (DSC) showed that the melting temperature of An was 262°C significantly lower than that measured from NA‐11 group (above 400°C). Crystallization behaviors of iPP/NA‐11 and iPP/An were also investigated by DSC analysis, respectively. The results showed the crystallization peak temperature and the crystallinity of iPP/An were almost near to that of iPP/NA‐11. Furthermore, mechanical and optical properties of iPP were strongly improved in the presences of An and NA‐11. The flexural strength of iPP was elevated 34 and 35% and the haze value was reduced from 40.4 to 15.1 and 14.9% by the addition of 0.15 wt% NA‐11 and An, respectively. These results demonstrate that the nucleating agent of An described here is a good nucleating agent for the crystallization of iPP as well as NA‐11. POLYM. ENG. SCI., 55: 22–28, 2015. © 2014 Society of Plastics Engineers  相似文献   

6.
The effect of zeolite 5A on the crystalline behavior of polypropylene (PP) in PP/β‐nucleating agent system was investigated with X‐ray diffractometer (XRD), differential scanning calorimeter (DSC), and polarized light microscope (PLM) in this study. Zeolite 5A has less effect on crystalline phase of PP/β‐nucleating agent than does n‐CaCO3, which is ascribed to the stronger surficial polarity and better dispersibility of zeolite 5A. The data of DSC indicated that the crystallization peak temperature of PP increases by 8.3°C in the presence of zeolite 5A, and n‐CaCO3 increases 5.7°C in PP/TMB‐5 system, relative to pure PP. And the initial crystallization temperature (Tc0) and the relative crystallinity (Xc) of PP is much more dramatically raised in the presence of zeolite 5A than CaCO3. The efficiency of zeolite 5A in reducing the spherulites size of PP was seen clearly from the PLM photographs. The mechanical testing results showed that the flexural strength and impact strength of PP/β‐nucleating agent system increased in the presence of zeolite 5A. POLYM. COMPOS., 2008. © Society of Plastics Engineers  相似文献   

7.
Non‐isothermal crystallization of aluminum nanopowder‐filled poly(3,3‐bis‐azidomethyl oxetane) (PBAMO) from melt at various constant cooling rates from 1 to 10 °C min−1 was studied. Ozawa's approach was used to analyze non‐isothermal crystallization kinetics. It was found that Ozawa's approach was effective at medium constant cooling rate. The crystallization activation energy derived from Kissinger's equation was 80.8 kJ mol−1. The experimental results showed that the aluminum nanopowder acted as a nucleating agent to raise the peak crystallization temperature and to accelerate the crystallization rate at higher constant cooling rates. Uniform crystals which showed one melting peak could be obtained at a constant cooling rate of 1 °C min−1.  相似文献   

8.
This article provides a detailed investigation of crystallization behavior and morphology of polylactic acid (PLA) in the presence of a nucleating agent: potassium salt of 5‐dimethyl sulfoisothalate, an aromatic sulfonate derivative (Lak‐301). Isothermal crystallization kinetics of PLA melt mixed with Lak at concentrations of 0.25–1 wt % was investigated at a range of crystallization temperature, 140–150 °C. To gain further insight on the effect of Lak, nonisothermal differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized optical microscope (POM), heat deflection temperature (HDT), and rheology were also performed. At 0.25 wt % Lak, crystallinity of PLA increased from 10% to 45%, and in 1 wt % Lak, maximum crystallinity of 50% was achieved. With 1 wt % Lak, crystallization half time reduced to 1.8 min from 61 min for neat PLA at 140 °C. The isothermal crystallization kinetics was analyzed using Avrami model. Values of the Avrami exponent for PLA with Lak were mainly in the range of 3 indicating a three dimensional crystal growth is favored. Crystallization rate was found to increase with increase in Lak content. Observation from POM confirmed that the presence of Lak in the PLA matrix significantly increased the nucleation density. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43673.  相似文献   

9.
Benzoylhydrazide compounds were evaluated as a nucleating agent for poly(L ‐lactic acid) (PLA). From the results of the differential scanning calorimetry, octamethylenedicarboxylic dibenzoylhydrazide (OMBH) was found to be most effective for acceleration of PLA crystallization under higher cooling rate of ?50°C min?1. PLA with OMBH of 1 wt % exhibited very short crystallization half‐time with wide range of isothermal temperature from 90 to 130°C. The molding cycle time of PLA with OMBH in injection molding was less than 3 min, and the cooling time was one‐third of ethylenebis(12‐hydroxystearylamide)/talc system as a nucleating agent. Physical and mechanical properties improved extremely, and the heat distortion temperature of 124°C, flexural modulus of 4.1 GPa, and Izod impact strength of 7.9 kJ m?2 were achieved. This indicates that the utilization of OMBH makes it possible to extend the application range of PLA as automotive parts and electric appliances, which require higher heat resistance and stiffness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 244–250, 2007  相似文献   

10.
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  相似文献   

11.
A series of compounds having hydrazide groups was prepared and evaluated as nucleating agent for poly(L ‐lactic acid) by differential scanning calorimetry. Hydrazide compounds derived from benzoic acid, 2‐hydroxybenzoic acid, 3‐tert‐butylbenzoic acid, and 2‐aminobenzoic acid, where two of hydrazide compounds connected by four methylene chain were evaluated in series. Benzoylhydrazide type was found to be more effective on the enhancement of crystallization of poly(L ‐lactic acid). Effects of connecting length of methylene chain numbers between two of benzoylhydrazide on the nucleation ability were also evaluated. Benzoylhydrazide‐type compound having 10 methylenes, that is, decamethylenedicarboxylic dibenzoylhydrazide demonstrated excellent nucleation ability, and the resulted crystallization temperature and enthalpy of PLA with the compound of 1 wt % loading were 131°C and 46 J g?1. The achieved crystallization temperature and enthalpy were over 10°C and over 10 J g?1 higher than PLA with conventional nucleating agents, such as talc and ethylenebis (12‐hydroxystearylamide). Thus, the improvement in processability, productivity, and heat resistance of PLA is suggested to be achieved by using decamethylenedicarboxylic dibenzoylhydrazide as a nucleating agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 198–203, 2007  相似文献   

12.
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   

13.
Nanocomposites of the segmented polyurethane (SPU) elastomer with different concentrations of multiwall carbon nanotubes (MWCNTs) have been prepared. Scanning electron microscopy has been used to visualize the surface morphology and distribution of the nanotubes inside the matrix. Differential scanning calorimetry has been utilized to investigate the effects of MWCNTs on the crystallization characteristics of the SPU by collecting data at four cooling rates namely 5, 10, 15, and 20°C/min in the temperature range between 200°C to ambient. The results reveal that MWCNTs act as effective nucleating agent for crystallization of the hard segment of SPU and advance the onset and peak temperatures of crystallization by 38 and 23°C, respectively. The associated enthalpy and extent of crystallization are also increased by 34%. Different crystallization kinetic parameters have been calculated using both modified Avrami and combined Ozawa‐Avrami models to suggest a three dimensional growth of crystallization of SPU and its nanocomposites. The activation energy has been calculated using Kissinger method, which indicates that activation energy decreases with increasing concentration of MWCNTs. The calorimetric results have further been correlated with thermomechanical analysis and glass transition temperature of the nanocomposites corresponding to soft segment is found to increase by 20°C. POLYM. ENG. SCI., 56:1248–1258, 2016. © 2016 Society of Plastics Engineers  相似文献   

14.
Polyester/clay nanocomposites were prepared by melt compounding with different clay loadings. Comparing against neat polyester resins, the crystallization and multiple melting behavior of the nanocomposites was investigated by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Nanoclay filler is an effective heterogeneous nucleating agent, as evidenced by a decrease and an increase in the crystallization temperature for both cold and melt crystallization of polyesters, respectively. The degree of crystallinity was found to increase with increasing clay content, due to heterogeneous nucleation effects by the addition of a nanofiller. For the annealed samples, multiple melting peaks were always observed for both neat polyester and its nanocomposites. The origins of the multiple melting behavior are discussed, based on the DSC and XRD results. Interestingly, an ‘abnormal’ high‐temperature endothermic peak (Tm, 3) at about 260 °C was observed when the nanocomposite samples were annealed at higher temperatures (eg ≥240 °C). The constrained polyester crystals formed within intercalated clay platelets due to confinement effects were probably responsible for this melting event at these higher temperatures. Copyright © 2004 Society of Chemical Industry  相似文献   

15.
Nonisothermal crystallization kinetics of pure polypropylene and polypropylene/down feather fiber composites were investigated using a differential scanning calorimeter at five different cooling rates. The experimental data on crystallinity versus temperature were analyzed by Avrami, Ozawa, and Liu models, respectively. The results indicated that the presence of down feather fiber served as nucleating agent and increased the onset and peak temperatures of crystallization of polypropylene/down feather fiber composites. Interestingly, polypropylene/down feather fiber composites showed a slower primary crystallization and a faster secondary crystallization than pure PP, meaning that down feather fiber retired the crystallizaiton process of PP matrix. The nucleation activity and activation energies were also calculated and agreed well with these results. Wide‐Angle X‐ray diffraction patterns indicated that down feather fiber induced the formation of β‐monoclinic crystals in polypropylene matrix. These phenomena were definitely different from the nonisothermal crystallization kinetics of polypropylene composite based on inorganic particles and organic cellulose fibers. POLYM. COMPOS., 37:3103–3112, 2016. © 2015 Society of Plastics Engineers  相似文献   

16.
The crystallization behavior of polylactic acid (PLA) was studied in the presence of a crystal nucleating agent, ethylenebishydroxystearamide (EBH). The crystallization rate and crystallinity were significantly increased with addition of EBH. The isothermal crystallization half-time at 105°C was decreased from 18.8 minutes for neat PLA to 2.8 minutes for PLA with 1.0 wt % of EBH. The crystallinity of PLA with 1.0 wt % EBH was about 35% after 5-minute annealing at 105°C. Like neat PLA, the double melting peaks were also observed for nucleated PLA. The changes of the double melt peaks were investigated with various crystallization temperatures, heating rates, and annealing times. The heat deflection temperature (HDT) of nucleated PLA was up to 93°C after annealing. The correlation between crystallinity and HDT was demonstrated. A percolation threshold of crystallinity was found corresponding to HDT. The crystal size of nucleated PLA was significantly decreased with addition of EBH. The mechanical properties of annealed PLA blends simultaneously; showed improved modulus and impact strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

17.
Currently, use of poly(lactic acid) (PLA) for injection molded articles is limited for commercial applications because PLA has a slow crystallization rate when compared with many other thermoplastics as well as standard injection molding cycle times. The overall crystallization rate and final crystallinity of PLA were controlled by the addition of physical nucleating agents as well as optimization of injection molding processing conditions. Talc and ethylene bis‐stearamide (EBS) nucleating agents both showed dramatic increases in crystallization rate and final crystalline content as indicated by isothermal and nonisothermal crystallization measurements. Isothermal crystallization half‐times were found to decrease nearly 65‐fold by the addition of only 2% talc. Process changes also had a significant effect on the final crystallinity of molded neat PLA, which was shown to increase from 5 to 42%. The combination of nucleating agents and process optimization not only resulted in an increase in final injection molded crystallinity level, but also allowed for a decreased processing time. An increase of over 30°C in the heat distortion temperature and improved strength and modulus by upwards of 25% were achieved through these material and process changes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

18.
In this work, use of myo‐inositol as a biobased nucleating agent (NA) for PLLA was researched. Effects of myo‐inositol on non‐isothermal and isothermal crystallization behaviors of PLLA at temperatures ranged from 85 °C to 130 °C were studied by using DSC, POM and WAXD. Isothermal crystallization kinetics results showed that the incorporation of myo‐inositol enhanced significantly the crystallization rate of the PLLA samples. It was confirmed that the optimum isothermal crystallization temperature range was 100 to 110 °C. The above results were instructive to confirm proper heat treatment time and temperature for compression or injection molding to fabricate highly crystallized PLLA articles. The relations among heat treatment time, crystallinity, heat resistance, and mechanical performances of the neat PLLA and PLLA/1% myo‐inositol specimens prepared by compression molding were investigated. Compared with the PLLA specimens, the PLLA/1% myo‐inositol specimens showed a shorter heat treatment time to reach the maximum crystallinity. Vicat softening temperature, as well as tensile strength, modulus, and toughness of the PLLA/1% myo‐inositol specimens was improved when crystallinity increased from 5.4% to 38.1%. Considering the nontoxicity and biocompatibility of myo‐inositol, PLLA/myo‐inositol blends would be potential to prepare some products, which are required higher health standard and can be used in elevated temperature environments. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44732.  相似文献   

19.
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  相似文献   

20.
Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers  相似文献   

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