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1.
A poly(butylene terephthalate) (PBT)/linear low‐density polyethylene (LLDPE) alloy was prepared with a reactive extrusion method. For improved compatibility of the blending system, LLDPE grafted with acrylic acid (LLDPE‐g‐AA) by radiation was adopted in place of plain LLDPE. The toughness and extensibility of the PBT/LLDPE‐g‐AA blends, as characterized by the impact strengths and elongations at break, were much improved in comparison with the toughness and extensibility of the PBT/LLDPE blends at the same compositions. However, there was not much difference in their tensile (or flexural) strengths and moduli. Scanning electron microscopy photographs showed that the domains of PBT/LLDPE‐g‐AA were much smaller and their dispersions were more homogeneous than the domains and dispersions of the PBT/LLDPE blends. Compared with the related values of the PBT/LLDPE blends, the contents and melting temperatures of the usual spherulites of PBT in PBT/LLDPE‐g‐AA decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1059–1066, 2002; DOI 10.1002/app.10399  相似文献   

2.
Abstract

Non-cross-linking linear low-density polyethylene-grafted-acrylic acid (LLDPE-g-AA) was prepared by melting reactive extrusion in our laboratory. The thermal behavior of LLDPE-g-AA was investigated by using differential scanning calorimetry (DSC). Compared with neat linear low-density polyethylene (LLDPE), melting temperature (Tm) of LLDPE-g-AA increased a little, the crystallization temperature (Tc) increased about 4[ddot] C, and the melting enthalpy (δ Hm) decreased with increase of acrylic acid content. Isothermal crystallization kinetics of LLDPE and LLDPE-g-AA samples was carried out using DSC. The overall crystallization rate of LLDPE was smaller than that of grafted samples. It showed that the grafted acrylic acid monomer onto LLDPE acted as a nucleating agent. Morphologies of LLDPE-g-AA and LLDPE were examined using SEM. Spherocrystal diameters of LLDPE-g-AA samples were lower than that of LLDPE.  相似文献   

3.
Polypropylene (PP) was functionalized with acrylic acid (AA) and styrene (st) as a comonomer by means of a radical‐initiated melt‐grafting reaction. FTIR, ESCA, and 1H‐NMR spectroscopies were used to characterize the formation of polypropylene grafted with acrylic acid (PP‐g‐AA) and polypropylene grafted with acrylic acid and styrene (PP‐g‐AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0–100 wt % of PP‐g‐AA were prepared by melt mixing. The effect of the modified polymer content on the surfaces of cast films was characterized through FTIR–ATR and ESCA analysis as well as contact‐angle, wetting‐tension, and ink‐adhesion measurements. The influence of the content of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast‐film surfaces of PP/PP‐g‐AA blends decreases with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. A notorious improvement on wetting tension was observed with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. From FTIR–ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl index, the lower the contact‐angle value for the polypropylene blends. An increase in crystallization temperature of PP was observed when AA monomers were grafted into PP and with increasing PP‐g‐AA content in the blend, probably caused by a nucleation effect of AA monomers that would improve the crystallization capability of PP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1497–1505, 2001  相似文献   

4.
The thermal properties of ethylene–propylene copolymer grafted with glycidyl methacrylate (EP-g-GMA) were investigated by using differential scanning calorimetry (DSC). Compared to the plain ethylene–propylene copolymer (EP), peak values of melting temperature (Tm) of the propylene sequences in the grafted EP changed a little, crystallization temperature (Tc) increased about 8–12°C, and melting enthalpy (ΔHm) increased about 4–6 J/g. The isothermal and nonisothermal crystallization kinetics of grafted and ungrafted samples was carried out by DSC. Within the scope of the researched crystallization temperature, the Avrami exponent (n) of ungrafted sample is 1.6–1.8, and those of grafted samples are all above 2. The crystallization rates of propylene sequence in EP-g-GMA were faster than that in the plain EP and increased with increasing of grafted monomer content. It might be attributed to the results of rapid nucleation rate. © 1996 John Wiley & Sons, Inc.  相似文献   

5.
Nano‐CaCO3/polypropylene (PP) composites modified with polypropylene grafted with acrylic acid (PP‐g‐AA) or acrylic acid with and without dicumyl peroxide (DCP) were prepared by a twin‐screw extruder. The crystallization and melting behavior of PP in the composites were investigated by DSC. The experimental results showed that the crystallization temperature of PP in the composites increased with increasing nano‐CaCO3 content. Addition of PP‐g‐AA further increased the crystallization temperatures of PP in the composites. It is suggested that PP‐g‐AA could improve the nucleation effect of nano‐CaCO3. However, the improvement in the nucleation effect of nano‐CaCO3 would be saturated when the PP‐g‐AA content of 5 phf (parts per hundred based on weight of filler) was used. The increase in the crystallization temperature of PP was observed by adding AA into the composites and the crystallization temperature of the composites increased with increasing AA content. It is suggested that the AA reacted with nano‐CaCO3 and the formation of Ca(AA)2 promoted the nucleation of PP. In the presence of DCP, the increment of the AA content had no significant influence on the crystallization temperature of PP in the composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2443–2453, 2004  相似文献   

6.
Crystallization of glassy‐crystalline‐glassy poly(vinylcyclohexane)‐b‐polyethylene‐b‐poly(vinylcyclo hexane) (PVCH‐PE‐PVCH) triblock copolymer treated in supercritical Carbon Dioxide (scCO2) was investigated by using differential scanning calorimetry (DSC) and atomic force microscope (AFM). It was found that the melting temperatures (Tm) and the crystallinity (Xc) of the PVCH‐PE‐PVCH samples treated in scCO2 at different annealing temperatures (T) were all much higher than those of the untreated PVCH‐PE‐PVCH, indicating that the scCO2 could effectively induce the samples to further crystallize. With increasing the T, the Tm of the samples linearly increased, even up to 108°C, close to the Tm (~ 110°C) of the PE homopolymer hydrogenated from polybutadiene which is equal to the PE block in the triblock copolymer. The results could be ascribed to the released PE chain ends linked to the PVCH block due to the lowered Tg of the PVCH block swollen by scCO2. It suggested that the origin of the confined crystallization in PVCH‐PE‐PVCH was the fixed PE chain ends by the glassy PVCH. AFM images of the samples treated in scCO2 showed that the PVCH lamella phase tended to connect each other and led to the aggregated structures. The result indicated that the PVCH block could be availably swollen by scCO2. It supported the DSC experiment results of the samples treated in scCO2. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2584–2589, 2006  相似文献   

7.
The nonisothermal crystallization kinetics of high‐density polyethylene (HDPE) and polyethylene (PE)/PE‐grafted maleic anhydride (PE‐g‐MAH)/organic‐montmorillonite (Org‐MMT) nanocomposite were investigated by differential scanning calorimetry (DSC) at various cooling rates. Avrami analysis modified by Jeziorny, Ozawa analysis, and a method developed by Liu well described the nonisothermal crystallization process of these samples. The difference in the exponent n, m, and a between HDPE and the nanocomposite indicated that nucleation mechanism and dimension of spherulite growth of the nanocomposite were different from that of HDPE to some extent. The values of half‐time (t1/2), K(T), and F(T) showed that the crystallization rate increased with the increase of cooling rates for HDPE and composite, but the crystallization rate of composite was faster than that of HDPE at a given cooling rate. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. It was 223.7 kJ/mol for composite, which was much smaller than that for HDPE (304.6 kJ/mol). Overall, the results indicated that the addition of Org‐MMT and PE‐g‐MAH could accelerate the overall nonisothermal crystallization process of PE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3054–3059, 2004  相似文献   

8.
Copolymers of linear low‐density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATWEEN80), containing hydrophilic and hydrophobic groups and 1‐olefin double bond were prepared by using a plasticorder at 190°C. To evaluate the grafting degree, two different approaches based on 1H‐NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small‐amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (TC) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films. The results indicated that the novel polyoxyethylene surfactant ATWEEN80 could greatly improve the hydrophilicity of LLDPE and the surface free energy varied from 33 mN/m of neat LLDPE to 106 mN/m of the grafted LLDPE film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

9.
Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. The effect of graft modification with PVP on the thermal and mechanical properties of PHBV was investigated. The thermal stability of grafted PHBV was remarkably improved while the melting temperature (Tm) was almost not affected by graft modification. The isothermal crystallization behavior of samples was observed by polarized optical microscopy and the results showed that the spherulitic radial growth rates (G) of grafted PHBV at the same crystallization temperature (Tc) decreased with increasing graft yield (graft%) of samples. Analysis of isothermal crystallization kinetics showed that both the surface free energy (σe) and the work of chain‐folding per molecular fold (q) of grafted PHBV increased with increasing graft%, implying that the chains of grafted PHBV are less flexible than ungrafted PHBV. This conclusion was in agreement with the mechanical testing results. The Young's modulus of grafted PHBV increased while the elongation decreased with increasing graft%. The hydrophilicity of polymer films was also investigated by the water contact angle measurement and the results revealed that the hydrophilicity of grafted PHBV was enhanced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

10.
Polymer blends typically are the most economical means to develop new resins for specific applications with the best cost/performance balance. In this paper, the mechanical properties, melting, glass transition, and crystallization behavoir of 80 phr polypropylene (PP) with varying weights of linear low density polyethylene (LLDPE) at 10, 20/ 20 wt % CaCO3, 30, 40, and 50 phr were studied. A variety of physical properties such as tensile strength, impact strength, and flexural strength of these blends were evaluated. The compatibility of these composite was examined by differential scanning calorimetry (DSC) to estimate Tm and Tc, and by dynamic mechanical analysis (DMA) to estimate Tg. The fractographic analysis of these blends was examined by scanning electron microscopy (SEM). It has been confirmed that increasing the LLDPE content trends to decreases the tensile strength and flexural strength. However, increasing the LLDPE content led to increases in the impact strength of PP/LLDPE blends. It was also found that up to 40 phr the corresponding melting point (Tm) was not effected with increasing LLDPE content. Each compound has more than one Tg, which was informed that there is a brittle‐ductile transition in fracture nature of these blends, the amount of material plastically deformed on the failure surface seems to increase with the increasing the LLDPE content. And PP/LLDPE blends at temperature (23°C) showed a ductile fracture mode characterized by the co‐existence of a shear yielding process; whereas at lower temperature (−20°C) the fractured surfaces of specimens appear completely brittle. The specimens broke into two pieces with no evidence of stress whitening, permanent macroscopic deformation or yielding. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

11.
The chain structure, spherulite morphology, and rheological property of LLDPE‐g‐AA were studied by using electronspray mass spectroscopy, 13C–NMR, and rheometer. Experimental evidence proved that AA monomers grafted onto the LLDPE backbone formed multiunit AA branch chains. It was found that AA branch chains could hinder movement of the LLDPE main chain during crystallization. Spherulites of LLDPE became more anomalous because of the presence of AA branch chains. Rheological behavior showed that AA branch chains could act as an inner plasticizer at the temperature range of 170–200°C, which made LLDPE‐g‐AA easy to further process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2538–2544, 2001  相似文献   

12.
In this study, tetra isopropyl ortho titanate (TTIP) and polycaprolactone (PCL) were chosen as the ceramic precursor and the continuous phase, respectively, for the preparation of novel nanocomposites by using an in situ sol‐gel process. In addition, acrylic acid grafted polycaprolactone (PCL‐g‐AA) was investigated as an alternative to PCL. The hybrids (PCL/TiO2 and PCL‐g‐AA/TiO2) were characterized via Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical thermal analysis (DMA), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and Instron mechanical testing. It was found that the carboxylic acid groups of acrylic acid acted as coordination sites for the titania phase to form chemical bonds, thus improving the properties of the acrylic acid grafted composite compared with its acrylic‐acid‐free counterpart. The TiO2 content also determined the strength of interfacial bonding between the polymer chains and the ceramic phase, as shown by changes in glass transition temperature (Tg) with TiO2 content. The maximum values of tensile strength and Tg were obtained with the PCL‐g‐AA/TiO2 composite at 10 wt % TiO2. At TiO2 contents above this, excess particles led to segregation between the organic and inorganic phases. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1749–1757, 2004  相似文献   

13.
The nonisothermal crystallization behavior and melting characteristics of high‐density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (?f) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (Tm) and crystallization temperature (Tp) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE‐g‐MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ?f in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

14.
Multiwalled carbon nanotubes (MWNTs) with acyl chloride functional groups and a metallocene polyethylene–octene elastomer (POE) or an acrylic acid‐grafted metallocene polyethylene–octene elastomer (POE‐g‐AA) were used to prepare hybrids (POE/MWNTs or POE‐g‐AA/MWNTs) using a melting method, with a view to identify a hybrid with improved thermal properties. Hybrids were characterized using Fourier transform infrared spectroscopy, 13C solid‐state nuclear magnetic resonance, X‐ray diffraction, thermogravimetry analysis, and scanning electron microscopy. MWNTs were purified using acid treatment, and results showed that ? COOH of MWNTs increased with acid treatment time and leveled off after 24‐h treatment. Much better dispersion and homogeneity of MWNTs was obtained with POE‐g‐AA in place of POE as the matrix. As a result, tensile strength at break of POE‐g‐AA/MWNTs was significantly improved even at 5 wt % MWNT content. Moreover, temperature of thermal decomposition for POE‐g‐AA/MWNTs was about 40–50°C higher than that for POE‐g‐AA, indicating higher thermal stability. This was because the carboxylic acid groups in POE‐g‐AA and the acyl chloride functional sites in MWNTs allow the formation of stronger chemical bonds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1328–1337, 2007  相似文献   

15.
Summary: Blends of M‐LLDPE and CAB were prepared in an internal laboratory mixer with 5, 10, 20, 30, 40 and 50 wt.‐% of CAB. Structure and properties of the blends were studied by means of tensile tests, DSC, SEM, extraction with a selective solvent, Raman spectroscopy and XRD. Blends prepared with 5 and 10 wt.‐% of CAB displayed the best mechanical properties. SEM and extraction with a selective solvent followed by Raman spectroscopy showed good interfacial adhesion between CAB and M‐LLDPE. No significant change on the melting temperatures (Tm) of the M‐LLDPE/CAB blends could be observed when compared with the Tm obtained for pure M‐LLDPE. XRD demonstrated that the addition of CAB has no influence on the lattice constants of M‐LLDPE, but the introduction of CAB increased the amorphous region, confirming that the miscibility occurs on the amorphous region of the polyethylene.

SEM image of the cryofracture surface of CAB‐20%.  相似文献   


16.
A series of graft polymers having polypropylene (PP) backbone and poly(ethylene‐co‐propylene) (EPR) side chains was prepared. PP backbone molecular weight (Mn) was 28–98 kg/mol, EPR side chain Mn was 2.6–17 kg/mol, and EPR content was 0–16 wt %. In this work, thermal analysis of the copolymers was performed using differential scanning calorimetry (DSC). Nonisothermal crystallization was performed at different cooling rates. The DSC thermograms revealed multiple melting peaks for slowly cooled samples, most likely the result of the melting of thinner tangential lamellae followed by the melting of thicker radial lamellae. Equilibrium melting temperature (Tm0) was determined using the linear Hoffman–Weeks method. Another approach was also used for determining Tm0: melting temperature (Tm) and crystallization temperature (Tc) were plotted as functions of logarithmic cooling rate. Linear relationships were observed for all samples with the cross points as Tm0's. As cooling rate decreased, Tc, Tm, and enthalpy of fusion (ΔHf) increased. Tm and Tm0 increased with increasing PP Mn. Tc and Tm were unaffected by the grafting of EPR onto the PP backbone. Tm0 and ΔHf decreased as EPR content increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3380–3388, 2006  相似文献   

17.
In attempts to improve the compatibility of polypropylene (PP) with polyethylene terephthalate (PET), a maleic anhydride grafted PP (PP‐g‐MA) was evaluated as a compatibilizer in a blend of 30/70 wt % PP/PET. PP‐g‐MA was produced from isotactic homopolymer PP utilizing the technique of solid phase graft copolymerization. Qualitative confirmations of the grafting were made by Fourier transform infrared spectroscopy (FTIR). Three different weight percent of compatibilizer, PP‐g‐MA, i.e., 5, 10, and 15 wt % have been used in PP/PET blends. The compatibilizing efficiency for PP/PET blend was examined using differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM) of crycrofractured surfaces, and energy dispersive X‐ray spectrum (EDAX). The results show that the grafted PP promotes a fine dispersed phase morphology, improves processability, and modifies the crystallization behavior of the polyester component. These effects are attributed to enhance phase interaction resulting in reduced interfacial tension. Also, the results show that the compatibilizing effects of the three amounts of grafted PP in blend are different and dependent on the amount used. Adding 10 wt % of compatibilizer into blend produced the finest dispersed morphology. Elemental analysis results show that PP is matrix. DSC determination revealed that the melting temperature (Tm) of the PET component declined to some extent by comparison with neat PET. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3986–3993, 2007  相似文献   

18.
Blends of two biodegradable semicrystalline polymers, poly(p‐dioxanone) (PPDO) and poly(vinyl alcohol) (PVA) were prepared with different compositions. The thermal stability, phase morphology and thermal behavior of the blends were studied by using thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). From the TGA data, it can be seen that the addition of PVA improves the thermal stability of PPDO. DSC analysis showed that the glass transition temperature (Tg) and the melting temperature (Tm) of PPDO in the blends were nearly constant and equal to the values for neat PPDO, thus suggesting that PPDO and PVA are immiscible. It was found from the SEM images that the blends were phase‐separated, which was consistent with the DSC results. Additionally, non‐isothermal crystallization under controlled cooling rates was explored, and the Ozawa theory was employed to describe the non‐isothermal crystallization kinetics. Copyright © 2006 Society of Chemical Industry  相似文献   

19.
A series of poly(ethylene terephthalate‐co‐4,4′‐bibenzoate)s (PETBBs) were prepared via direct esterification from the monomers of terephthalic acid (TPA), 4,4′‐biphenyl dicarboxylic acid (BPDA), and ethylene glycol (EG) with different molar ratios. The chemical compositions of the obtained PETBBs, investigated by H1‐NMR, were identical with the feed ratio, and the high molecular weights of PETBBs were confirmed by GPC analysis. The glass transition, crystallization, and melting behavior of them were measured by DSC; the results indicated that, in the range of 5–25 mol% of BPDA addition, the glass transition temperature (Tg) increased almost linearly and the melting temperature (Tm) decreased with increasing content of BPDA unit. As expected, the crystallization of PETBB became difficult with increasing introduction of BPDA, explained by higher crystallization temperature and smaller crystallization enthalpy from the glassy state. This decrease of crystallization rate may be beneficial to film processing. Moreover, owing to the introduction of rigid‐rod BPDA unit, the initial and maximum thermal‐oxidative decomposition temperatures were enhanced. The kinetic analysis of the thermal‐oxidative degradation indicated that the apparent activation energies of degradation for these PETBBs became higher than that of PET. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers  相似文献   

20.
EVA was blended with phenoxy over the whole range of composition using a twin‐screw Brabender. Two‐phase separation caused by EVA crystallization was observed in the EVA‐rich blends and the dispersed domain of EVA was not clearly shown in the phenoxy‐rich blends. Differential scanning calorimetry (DSC) showed that the glass transition temperature (Tg) of EVA was increased by 5–10°C in the EVA‐rich blends but the Tg of phenoxy was superposed over the melting behavior of EVA. X‐ray diffraction measurement indicated that EVA crystallization was restricted in the phenoxy‐rich blends and the EVA crystal structure was influenced by incorporation of phenoxy into the EVA‐rich blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 227–236, 1999  相似文献   

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