PP/LDPE blends produced by reactive processing. I. Grafting efficiency and rheological and high‐elastic properties of [PP/LDPE]‐g‐IA melts

Itaconic acid (IA) was grafted onto polypropylene/low‐density polyethylene (PP/LDPE) blends. The ratio of polymeric components was varied from 100 : 0 to 0 : 100. The effect of the variation in the ratios of the components on grafting efficiency and concomitant side processes was studied. Grafting of IA (1 wt %) was initiated by 2,5‐dimethyl‐2,5‐di(tert‐butyl peroxy)‐hexane (0.3 wt %) and was carried out in an extruder reactor equipped with a dynamic mixer. An increase in the PP content of the blend led to a lower yield of the grafted product. With low concentrations of LDPE in the blend (up to 25 wt %), grafting efficiency was observed to increase, and this increase was greater in comparison with the additive rule. Between 25 and 99 wt % of LDPE in the blend, grafting efficiency rose monotonically with LDPE concentration. At or below an LDPE content of 25 wt %, the melt flow index (MFI) of [PP/LDPE]‐g‐IA would increase unlike with PP‐g‐IA systems. But a small quantity of PP (below 25 wt %) in the [PP/LDPE]‐g‐IA blends would result in a decreased MFI unlike with LDPE‐g‐IA. The dependence of swell index and melt strength on the ratio of polymeric components in [PP/LDPE]‐g‐IA blends also was investigated. ©2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5095–5104, 2006     

Graft copolymerisation of N‐vinyl pyrrolidone onto polypropylene copolymer in melt: Effect of grafting on thermomechanical properties and paint adhesion

N‐vinyl pyrrolidone (NVP) was grafted onto a polypropylene copolymer (PP) in melt in a Brabender Plasticorder and single screw extruder. The effect of variation of dicumyl peroxide (DCP) and lupersol (LUP) concentrations alone and with 20 wt % NVP concentration in the Brabender Plasticorder on Melt Flow Index (MFI) and final torque values was studied. Variation of NVP concentration (1–10 wt %) at a fixed DCP concentration on percent grafting (G) and MFI was also studied in the single screw extruder. The graft copolymers (PP‐g‐NVP) obtained by reaction of PP with NVP were soxhlet extracted with isopropanol to remove homopolymer, dried, and finally characterized by Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The PP‐g‐NVP (0–30 wt %) was used as an additive with PP, extruded in the single screw extruder, molded, and the mechanical properties and paint adhesion was measured. MFI values increased and torque values decreased with an increase in initiator concentration, indicating the dominance of the peroxide‐initiated scission reaction over grafting. DCP gave higher grafting compared to LUP. When NVP concentration was increased, MFI values increased initially due to more scission, and then decreased, indicating more graft copolymer formation. Mechanical properties increased by incorporation of PP‐g‐NVP as an additive than PP‐g‐NVP alone. Paint adhesion increased by the presence of PP‐g‐NVP as additive especially with polyurethane primer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2173–2180, 2003     

Compatibilization of polypropylene/Poly(acrylonitrile‐butadiene‐styrene) blends by polypropylene‐graft‐cardanol

The polypropylene‐graft‐cardanol (PP‐g‐cardanol) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol which could increase the interfacial energy of PP and inhibit the degradation of PP during the process of reactive extrusion and usage. In this article, PP‐g‐cardanol and polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) were used as compatibilizers of the polypropylene (PP)/poly(acrylonitrile‐butadiene‐styrene) (ABS) blends. PP/ABS (70/30, wt %) blends with PP‐g‐cardanol and PP‐g‐MAH were prepared by a corotating twin‐screw extruder. From the results of morphological studies, the droplet size of ABS was minimized to 1.93 and 2.01 μm when the content of PP‐g‐cardanol and PP‐g‐MAH up to 5 and 7 phr, respectively. The results of mechanical testing showed that the tensile strength, impact strength and flexural strength of PP/ABS (70/30) blends increase with the increasing of PP‐g‐cardanol content up to 5 phr. The complex viscosity of PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol showed the highest value. Moreover, the change of impact strength and tensile strength of PP/ABS (70/30) blends were investigated by accelerated degradation testing. After 4 accelerated degradation cycles, the impact strength of the PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol decrease less than 6%, but PP/ABS (70/30) blends with 5 phr PP‐g‐MAH and without compatibilizer decrease as much as 12% and 32%, respectively. The tensile strength of PP/ABS (70/30) blends has a similar tendency to that of impact strength. The above results indicated that PP‐g‐cardanol could be used as an impact modifier and a good compatibilizer, which also exhibited better stability performance during accelerated degradation testing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41315.     

Preparation and reaction kinetics of polypropylene‐graft‐cardanol by reactive extrusion and its compatibilization on polypropylene/polystyrene

Polypropylene‐graft‐cardanol (CAPP) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol, which improved the inherent defects of PP such as its chemical inertness and hydrophobicity. Moreover, the cardanol grafted onto PP resolved the degradation of PP during reactive extrusion and use. The effects of reactive extrusion on the change of the molecular structure of PP, the change in the free‐radical concentration during processing, and the compatibilization of CAPP on the PP/polystyrene (PS) composite materials were examined in this study. The constants of the grafting reaction rate at the beginning of reactive extrusion were also deduced. The results show that cardanol was grafted onto PP, and the p–π conjugate system in cardanol was observed to stabilize free radicals. The grafting reaction rate (R_g) at the initial stage of the grafting reaction process was calculated through the equation R_g = k_g[M·][Cardanol], where k_g is the constant of the apparent grafting reaction rate and [M·] is the concentration of free radicals in the reaction system. k_g first increased with the growth of temperature and then began to decrease when the temperature exceeded the critical temperature of 200°C. The mechanical properties showed almost no change after the samples were aged for 72 h. This was due to CAPP, which changed PP/PS to a ductile material from a brittle one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39911.     

Novel multimonomer‐grafted polypropylene preparation and application in polypropylene/poly(vinyl chloride) blends

A novel grafted polymer was prepared in one step through free‐radical melt grafting in a single‐screw extruder. It was shown that the addition of styrene (St) to the melt‐grafting system as a comonomer could significantly enhance the grafting degree of methyl methacrylate (MMA) onto polypropylene (PP) and reduce the degradation of the PP matrix by means of Fourier transform infrared and melt flow rate testing, respectively. Then, the potential of using multimonomer‐grafted PP, which was designated PP‐g‐(St‐co‐MMA), as the compatibilizer in PP/poly(vinyl chloride) (PVC) blends was also examined. In comparison with PP/PVC blends, the average size of the dispersed phase was greatly reduced in grafted polypropylene (gPP)/PVC blends because of the addition of the PP‐g‐(St‐co‐MMA) graft copolymer. The tensile strength of the gPP/PVC blends increased significantly, and the impact strength was unchanged from that of the pure PP/PVC blends. The results of differential scanning calorimetry and scanning electron microscopy suggested that the compatibility of the PP/PVC blends was improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study of multi‐monomer melt‐grafting onto polypropylene in an extruder

Free‐radical melt‐grafting of the dual‐monomer systems glycidyl methacrylate–styrene (GMA‐St) and hydroxyethyl methacrylate–styrene (HEMA‐St) onto polypropylene (PP) has been studied using a single‐screw extruder. For single monomer grafting systems, degradation of PP was unavoidable and deterioration of the mechanical properties of the grafted PP subsequently occurred because of β‐scission of PP chains during the free‐radical melt‐grafting process. However, for the dual‐monomer systems, it is shown that the addition of styrene as a comonomer can significantly enhance the GMA or HEMA grafting levels on PP and reduce the extent of β‐scission of PP backbone. It has been found that the grafting degree of dual‐monomer melt‐grafted PP, such as PP‐g‐(GMA‐co‐St) or PP‐g‐(HEMA‐co‐St), is about quadruple that of single‐monomer grafted PP for the same monomer and dicumyl peroxide concentrations. Moreover, the melt flow rate of the dual‐monomer grafted PP is smaller than that of the unmodified PP. Hence, PP not only was endowed with higher polarity, but also kept its good mechanical properties. © 2000 Society of Chemical Industry     

Melt grafting of maleic anhydride onto polypropylene with 1‐decene as a second monomer

The influence of 1‐decene as the second monomer on the melt‐grafting behavior of maleic anhydride (MAH) onto polypropylene (PP) was studied with differential scanning calorimetry and Fourier transform infrared spectroscopy. We found that the value of the grafting degree increased from 0.68% for pure MAH‐g‐PP to 1.43% for the system with a 1‐decene/MAH molar ratio of 0.3, whereas the maximum value with styrene (St) as the second monomer was 0.98% under an St/MAH molar ratio of 1.0. Compared with the contribution of St/MAH‐g‐PP to the peeling strength between the PP and polyamide (PA) layer for a PP/PA laminated film, the introduction of 1‐decene/MAH‐g‐PP increased the peeling strength from 180 g/15 mm to 250 g/15 mm. 1‐Decene inhibited the chain scission behavior of PP. 1‐Decene reacted with MAH to form a 1‐decene/MAH copolymer or the Alder‐ene reaction product before the two monomers grafted onto PP. The grafting of the reactive product onto PP greatly improved the grafting degree of MAH. What is more, because of the similar chemical structures of 1‐decene and PP, the affinity of 1‐decene with PP was higher than that of St. Compared with St, the introduction of less 1‐decene led to a higher grafting degree and higher peeling strength. Therefore, we concluded that 1‐decene was more effective for improving the grafting degree of MAH onto PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Styrene‐assisted grafting of maleic anhydride onto polypropylene by reactive processing

The grafting of maleic anhydride (MA) onto polypropylene (PP) was performed in the presence of the electron‐donating monomer styrene (ST) according to a central composite experimental design, in which the initial MA and ST concentrations were varied. The grafting of MA onto PP in the absence of ST was also performed. All reactions were carried out in the molten state in a Haake rheometer. The amount of reacted MA and the extent of degradation in PP were determined by means of Fourier transform infrared spectroscopy and melt flow index (MFI) measurements, respectively. The results showed that the presence of ST in the reactive processing caused a reduction in MFI and an increase in the level of reacted MA when the initial MA concentration equaled the initial ST concentration. An increase in the initial MA concentration presented distinct behavior that depended on the ST content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology and mechanical properties of polypropylene‐POSS hybrid nanocomposites obtained by reactive blending

The polypropylene‐polyhedral oligomeric silsesquioxane (PP‐POSS) organic–inorganic hybrids were obtained and studied. The hybrids were prepared by grafting of POSS on PP chains during a reactive melt‐blending of polypropylene (iPP), maleic anhydride functionalized PP (PP‐g‐MA), and amine‐functionalized POSS (aminopropylheptaisobutyl‐POSS, ambPOSS, aminopropylheptaisooctyl‐POSS, amoPOSS, or aminoethylaminopropylheptaisobutyl‐POSS, am2bPOSS), taking advantage of the high efficiency of amino‐anhydride reaction in the molten state. The structure, morphology, and physical properties of the obtained hybrids and blends were studied by means of wide‐ and small‐angle X‐ray scattering, dynamic scanning calorimetry, scanning electron microscopy, dynamic mechanical thermal analysis, as well as tensile and impact experiments. The influence of POSS chemical structure and grafting degree on the morphological characteristics and mechanical properties was investigated. It was found that grafting of POSS cages on PP chains leads to the POSS dispersion on the molecular level. On contrary, when POSS was mixed with plain iPP any grafting of POSS on iPP chains was impossible, which resulted in phase‐separated blend with crystallites of POSS dispersed in iPP matrix. The mechanical tests revealed that modification of polypropylene by grafting with POSS molecules does not affect significantly its mechanical properties, both static and dynamic, except ultimate strain, which is markedly lower in hybrids and their blends than in plain iPP. Also the impact properties of PP were practically not improved by modification with POSS. POLYM. COMPOS., 34:929–941, 2013. © 2013 Society of Plastics Engineers     

Thermal and crystallization behavior of silane‐crosslinked polypropylene

Silane‐crosslinked polypropylene (PP) has been prepared first by the grafting of silane onto the backbone of PP in a melt process and then by crosslinking in warm water. The effects of type and concentration of silane and peroxide on the silane grafting on PP were investigated. The thermal behavior of the silane‐crosslinked PP was studied by thermogravimetric (TG) and differential scanning calorimetry (DSC) methods. TG results show that PP prepared via silane crosslinking increases its thermal stability greatly. It has been found from DSC measurements that the crystallization temperatures, ie the onset temperature and peak temperature of the exotherm of the silane‐crosslinked PP, increase compared with those of the pure PP. The silane crosslinking hardly changes the crystallinity degree of PP. The crystallization behavior of the silane‐crosslinked PP was also studied by wide‐angle X‐ray diffraction analysis. Copyright © 2004 Society of Chemical Industry     

Synthesis of polypropylene graft copolymers from a hydroxyl‐groups‐containing polypropylene precursor via atom‐transfer radical polymerization

Isotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl₂‐supported TiCl₄ as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry     

Surface functionalization of polypropylene by entrapment of polypropylene‐grafted‐poly(ethylene glycol)

A surface functionalization polypropylene was prepared by entrapment a copolymer of polypropylene‐grafted‐poly(ethylene glycol) into polypropylene. The effects of structure of copolymer, contact dies, and content of modifiers were studied. The results of attenuated total reflection infrared spectroscopy(ATR‐FTIR) and contact angle measurements indicated that PP‐g‐PEG could preferably diffuse onto the surface and effectively increase the hydrophilicity of PP. PPw‐g‐PEG with lower PEG contents, lower molecular weight of PPw and PEG had better selective enrichment on the surface of PP blend film. By grafting of PEG‐OH onto the MPP, PP macromolecular surface modifier with better solvent‐resistance than that of PEG can be achieved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of the high‐density polyethylene melt index on the microcellular foaming of high‐density polyethylene/polypropylene blends

The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004     

Studies on rheology and morphology of POE/PP thermoplastic elastomer dynamically crosslinked by peroxide

An ethylene‐octene copolymer (POE)/polypropylene (PP) thermoplastic elastomer was prepared through dynamically crosslinking by 2,5‐dimethyl‐2,5‐dilbuty (Peroxy) hexane (DHBP). The effects of DHBP concentration, POE/PP ratio, melt flow index (MFI) of PP, and mixer rotation on rheology and morphology of the thermoplastic elastomer were studied. The results showed that with increasing DHBP concentration or POE content, the size of crosslinked particles as well as the melt viscosity increased. Furthermore, agglomerates or a network structure formed as the size of crosslinked particles increased. The melt viscosity also increased as MFI of PP decreased, while the size of crosslinked particles decreased under the same condition. Research on the morphology of dynamically crosslinked POE/PP thermoplastic elastomer flowing through a capillary rheometer at different shear rates show that the reprocessing had little effect on the morphology of dynamically crosslinked elastomer. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.     

加工工艺对反应挤出腰果酚接枝聚丙烯的影响

利用转矩流变仪反应挤出制备腰果酚接枝聚丙烯,考查了加工温度和螺杆转速对反应产物接枝率和聚丙烯主链降解的影响。结果表明,当加工温度为180 ℃、螺杆转速为30 r/min时,制得的腰果酚接枝聚丙烯的接枝率最大,为4.37 %,此时聚丙烯主链的降解副反应最少,其熔体流动速率为4.44 g/10 min,在此条件下制得的产物的剪切应力和黏度均达到最大值。     

Influence of grafting formulations and extrusion conditions on properties of silane‐grafted polypropylenes

The melt grafting of unsaturated silanes onto powdered polypropylene (PP) in a Haake TW100 twin‐screw extruder and curing in hot water were studied. The influence of grafting formulations and extrusion conditions on the melt flow rates of grafted PP and the gel percentages of crosslinked PP was investigated. The gel percentages of methacryloylpropyltrimethoxysilane (VMMS)‐grafted PP were markedly higher than those of vinyltriethoxysilane (VTES)‐ and vinyltrimethoxysilane (VTMS)‐grafted PP, while significantly less degradation of PP during grafting was observed for VMMS‐grafted PP. When benzoyl peroxide (BPO) was used as an initiator, no degradation of PP during grafting was observed, and the melt flow rates of grafted PP decreased with increasing BPO concentration. In contrast, use of dicumyl peroxide (DCP) as an initiator resulted in severe degradation of PP, and the melt flow rates of grafted PP increased gradually with increasing DCP concentration. BPO resulted in higher gel percentages than those of DCP at a fixed initiator concentration. Introduction of styrene into the grafting system greatly improved the gel percentage of crosslinked PP and reduced the degradation of PP during grafting. The optimum molar ratio of styrene to monomer is at about 1.5:1. Relatively low processing temperatures and high screw speeds are favorable. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1233–1238, 2000     

Studies on grafting of acrylic acid onto polypropylene melt‐blown nonwovens induced by electron‐beam preirradiation

We report the graft copolymerization of acrylic acid onto the polypropylene (PP) melt‐blown nonwovens induced by electron beam (EB) preirradiation in this article. The occurrence of the graft copolymerization was confirmed by means of XPS, FTIR, and SEM. The effects of preirradiation dose, monomer concentration, bath ratio, reaction time, and temperature on the graft ratio were investigated. The water conservation, water absorption rate, and K⁺ exchange capacity were also determined on the grafted PP melt‐blown nonwovens, which showed that EB preirradiation‐induced grafting was an effective way to improve the hydrophicility of PP melt‐blown nonwovens. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4971–4977, 2006     

Preparation of polypropylene–clay nanocomposites by the co‐intercalation of modified polypropylene and short‐chain amide molecules

The effect of short‐chain amide (AM) molecules on the intercalation of montmorillonite clay has been investigated by the melt blending of polypropylene (PP) with clay in the presence of AM molecules such as 13‐cis‐docosenamide (erucamide). Polypropylene–clay nanocomposites (PPCNs) were prepared by the co‐intercalation of maleic anhydride grafted polypropylene (PP–MA) and an AM compound. The resulting nanocomposite structures were characterized with X‐ray diffraction (XRD) and transmission electron microscopy, whereas the thermal characterization of the PPCNs was conducted by thermogravimetric analysis. XRD results showed that the AM molecules intercalated into clay galleries and increased the interlayer spacing, a result confirmed by surface energy (contact angle) and melt flow index measurements. This additive allowed the formation of an intercalated nanocomposite structure, but an exfoliated PPCN structure was also formed with the use of AM with a PP–MA‐based compatibilizer. A new preparation method for PPCNs was, therefore, developed by the co‐intercalation of AM and PP–MA; this resulted in a significantly improved degree of intercalation and dispersion. The enhanced thermal stability of PPCN, relative to pure PP, further demonstrated the improved clay dispersion in the nanocomposite structures prepared by this method. A possible mechanism for the co‐intercalation of AM and PP–MA into the clay galleries is proposed, based on hydrogen bonding between these additives and the silicate layers. Consideration is also given to possible chemical reactions and physical interactions in this rather complex system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A facile,green, versatile protocol to prepare polypropylene‐g‐poly(methyl methacrylate) copolymer by water‐solid phase suspension grafting polymerization using the surface of reactor granule technology polypropylene granules as reaction loci

A facile and environment friendly process, called water‐solid phase suspension grafting polymerization, was developed to prepare polypropylene‐g‐poly(methyl methacrylate) (PP‐g‐PMMA) copolymer with a submicrometer microdomain. In this approach, graft polymerization was elaborately regulated to occur within micropores of polypropylene particles prepared by reactor granule technology. FTIR spectra of the samples after extraction demonstrated that PMMA was successfully grafted onto the PP. The results showed grafting percentage (GP) of PMMA increased with the increasing monomer ratios to PP and that could reach 13.6%. Whereas the grafting efficiency decreased as the monomer ratio increased. The addition of second monomer styrene improved GP up to 24.5%. Differential Scanning Calorimetry tests showed that the grafting of PMMA have a slight effect on the melting point and the relative crystallinity of PP. TEM micrographs demonstrated PMMA domains distributed in PP matrix with sizes ranging from about 100 to 300 nm. In addition, Shear viscosity increased with the growing GP indicated by rheological measurement. The preliminary evaluation showed PP‐g‐PMMA was effective in improving the compatibility of PP/acrylonitrile‐styrene‐acrylate blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene/polypropylene‐grafted acrylic acid blends for multilayer films: Preparation and characterization

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