Comparing the compatibility of various functionalized polypropylenes with thermoplastic polyurethane (TPU)

Three functionalized polypropylenes (PP), a maleated PP (PP-g-MA), primary amine functionalized PP (PP-g-NH₂), and secondary amine functionalized PP (PP-g-NHR), were melt blended with a thermoplastic polyurethane (TPU) at different compositions. Compatibility of each functionalized PP with TPU was compared by investigating the binary blends using rheological (mixer torques, dynamic shear rheometry), thermal (dynamic mechanical analysis), mechanical (tensile test), and morphological (scanning electron microscopy with image analysis, particle size analysis) measurements. Compatibility of the three functionalized PP's with TPU is ranked in a decreasing order as follows: PP-g-NHR≥PP-g-NH₂?PP-g-MA, which is attributed to higher reactivity of amine (primary and secondary) with urethane linkages. Accordingly, the TPU blends with the two types of amine functionalized PP's exhibited much better synergy, as reflected by much improved mechanical properties including higher tensile strength and ultimate elongation, and finer and more stable morphologies.     

Novel strategy for ternary polymer blend compatibilization

A novel strategy for compatibilization of ternary polymer blends was described. PP (polyolefins)/PA6 (engineering plastics)/PS (styrene polymers) was selected as a model ternary blend system, and the compatibilization effect was investigated by means of SEM, rheometer, dynamic mechanical thermal analysis and mechanical testing. The results indicated that, as a ternary polymer blend compatibilizer, styrene and maleic anhydride dual monomers melt grafted polypropylene [PP-g-(MAH-co-St)] showed more effective compatibilization in the PP/PA6/PS ternary blend system than PP-g-MAH, PP-g-St and their mixture. The good compatibilizing effect of PP-g-(MAH-co-St) can be explained by two mechanisms. One is the in situ formation of [PP-g-(MAH-co-St)]-g-PA6 copolymer at the PP/PA6 interface, and the other is that it also contains styrene blocks, resulting in chemical affinity with PS and PP homopolymers.     

Poly(propylene)-based Films Modified with a Tetracationic Phthalocyanine with Applications in Photodynamic Inactivation of Candida albicans

Photoactive films based on polymer-like poly(propylene) were generated and utilized as support of zinc(II)tetramethyltetrapyridino[2,3-b:2′,3′-g:2″,3″-l:2″′,3″′-q]porphyrazinium salt (ZnTM2,3PyPz). Using a photograft polymerization of acrylic acid, the poly(propylene) film was functionalized with carboxyl groups (PP-g-PAAc), which attached ZnTM2,3PyPz by electrostatic bond to form PP-g-PAAc-Pc films. In vitro investigations indicated that PP-g-PAAc-Pc films produced photodynamic inactivation of Candida albicans cells, mainly mediated by a contribution of type II process. According to the results, the photodynamic activity produced by the PP-g-PAAc-Pc film and visible light irradiation can successfully inactivate C. albicans deposited on the surface of the films.     

Synthesis and properties of polyolefin graft copolymers by a grafting “onto” reactive process

The synthesis of graft copolymers by the grafting “onto” process in the molten state was described. Functional oligomers obtained by telomerization or by ATRP were reacted onto maleic anhydride grafted polypropylene (PP-g-MAH) and poly(ethylene-ter-maleic anhydride-ter-methyl acrylate) (P(E-ter-MAH-ter-MeA)) to obtain PP-g-PMMA and P(E-ter-MAH-ter-MeA)-g-PMMA graft copolymers, respectively. The grafting of different mono-functional oligomers bearing hydroxyl, aliphatic amine or aromatic amine functions was investigated at 180 °C and at 200 °C. The grafting efficiency was very low in the case of hydroxyl-terminated PMMA, while the amine-terminated PMMA led to high yields. In the last part, PP-g-PMMA and P(E-ter-MAH-ter-MeA)-g-PMMA graft copolymers were synthesized by the reaction of aliphatic amine functional PMMA oligomers onto PP-g-MAH and P(E-ter-MAH-ter-MeA), respectively. The influence of the molecular weight of PMMA oligomers was investigated and showed that he grafting efficiency slightly decreases with the increasing molecular weight. However, this process allows the synthesis of PP-g-PMMA graft copolymers containing 6-45 wt% of PMMA side chains. The microstructure of the nanostructured PP-g-PMMA and P(E-ter-MAH-ter-MeA)-g-PMMA graft copolymers was investigated by TEM and SEM. This was established that the addition of PP-g-PMMA in PP/PMMA binary blends allows to control their morphologies and stabilities.     

Effects of long chain branches on the crystallization and foaming behaviors of polypropylene-g-poly(ethylene-co-1-butene) graft copolymers with well-defined molecular structures

A series of polypropylene-g-poly(ethylene-co-1-butene) graft copolymers (PP-g-EBR) with well-defined long chain branched (LCB) molecular structures, basing on the same PP–BT precursor (PP–BT2), were used to study effects of EBR LCBs on the crystallization and foaming behaviors of PP-g-EBRs. The kinetics results of isothermal and nonisothermal crystallization verify the opposite effects of LCB structure on the crystallization process of PP backbones in PP-g-EBRs: on one hand, the indolent LCB structure can perform the function of heterogeneous nucleation to facilitate the crystallization; on the other hand, the mobility and reptation ability of PP backbones are restrained by the LCB structure, which hinders the crystallization process. Additionally, the fluctuation-assisted nucleation mechanism caused by microphase separation between the EBR rich phase and the PP rich phase may account, to some extent, for the heterogeneous nucleation effect. The PP–BT2 and PP-g-EBRs were foamed by a batch method under the same conditions, using supercritical CO₂ as blowing agent. The resulting PP-g-EBR foams exhibited closed cell structure and increased cell density compared to the PP–BT2 foam, attributing to the enhanced melt strength. The cell density of PP-g-EBR foam increased first and decreased then with the LCB level increasing. The influence of LCB level on cell size was somewhat complex. Increasing LCB level, which promoted melt strength and strain hardening behavior of PP-g-EBRs, decreased the cell size and narrowed the cell size distribution. However, large cells were observed in PP-g-EBR foams with relatively high LCB level, which could be ascribed to the larger growing space introduced by the higher content of amorphous EBR LCBs. Moreover, the melting behaviors of PP–BT2 and PP-g-EBRs before and after foaming treatment were compared.     

Evaluation of polypropylene grafted with maleic anhydride and styrene as a compatibilizer for polypropylene/clay nanocomposites

Among modified Poly(propylene)s (PPs) grafted with polar monomers, PP grafted with maleic anhydride (PP-g-MAH) is known to be the most efficient compatibilizer for PP/clay nanocomposites, since it provides well-dispersed nanostructures and yields optimal physical properties of the nanocomposites. One drawback of this material, however, is that it becomes brittle and its viscosity decreases drastically, leading to nanocomposites with low toughness as the graft degree of MAH increases. Therefore, there is a limitation to increasing both stiffness and toughness of PP/clay nanocomposites with PP-g-MAH. In this study, we investigated the performance of a PP grafted with maleic anhydride and styrene (PP-g-MAH-St) as compatibilizers in PP/clay nanocomposites. It was found that the incorporation of styrene as a comonomer prevents molecular weight reduction of the PP main chain upon high loading of a radical initiator for high graft degree of MAH. The compatibilizers (PP-g-MAH-St) thus obtained show good compatibilizing performance in PP/clay nanocomposites. The PP/clay nanocomposites compatibilized by PP-g-MAH-St show both high stiffness and toughness, which is accomplished by using a compatibilizer of higher viscosity compared with PP-g-MAH.     

Polypropylene-grafted nanoparticles as a promising strategy for boosting physical properties of polypropylene-based nanocomposites

SiO₂ nanoparticles grafted to terminally hydroxylated polypropylene (PP-g-SiO₂) with different molecular weights were melt mixed with PP to prepare a series of PP/PP-g-SiO₂ nanocomposites. PP/PP-g-SiO₂ offered several advantages over pristine PP and PP/unmodified SiO₂ such as highly uniform dispersion up to 10 wt.-%, +200–400% faster crystallization and +30% increments for both the Young's modulus and the tensile strength without largely sacrificing the melt viscosity of PP. We concluded that grafted chains act as crystallization nuclei and co-crystallize with matrix chains to make PP-g-SiO₂ nanoparticles as a physical cross-linker between lamellae, while the linkage disappears in melt and grafted chains minimize the cohesive attraction between nanoparticles.     

The Effect of Spray-Freeze Drying of Montmorillonite on the Morphology,Dispersion, and Crystallization in Polypropylene Nanocomposites

The spray-freeze drying (SFD) technique was applied to sonicated aqueous suspensions of spray-dried montmorillonite clay (MMT) to produce highly porous agglomerates (SFD-MMT). Both MMT (used as a reference) and SFD-MMT were subsequently incorporated in polypropylene (PP) via melt compounding to produce 2 wt % nanocomposites with and without maleic anhydride grafted polypropylene (PP-g-MA). Polypropylene nanocomposites containing SFD-MMT exhibited thinner silicate flake layers compared to large agglomerates in PP/MMT nanocomposites. SFD-MMT particles became even more finer in the presence of PP-g-MA (i.e., in PP/PP-g-MA /SFD-MMT) where it hindered PP crystallization instead of serving as nucleation sites for the PP crystallization during rapid cooling. SFD-MMT improved the thermal stability of PP/PP-g-MA by 30°C compared to only 5–8°C for MMT/nanocomposites. MMT acts as a heterogeneous nucleating agent in the nucleation-controlled PP nanocomposites, but the hindrance effect was observed for the PP/PP-g-MA with SFD-MMT. PP/PP-g-MA/SFD-MMT exhibited twice the edge surface energy as compared to PP/PP-g-MA/MMT. The incorporation of both types of MMT raised the tensile moduli of PP and PP/PP-g-MA, with no improvement in their tensile strength and a decrease in the elongation at break. The PP/PP-g-MA/SFD-MMT showed brittle failure. POLYM. ENG. SCI., 60:168–179, 2020. © 2019 Society of Plastics Engineers     

Rheologically determined phase behavior and miscibility of reactively compatibilized poly(ethylene terephthalate)/polypropylene blends

Rheology, phase behavior and morphology of poly(ethylene terephthalate)/polypropylene (PET/PP) blends compatibilized with maleic-anhydrate-grafted-PP (PP-g-MA) and n-butyl-acrylate-glycidyl-methacrylate-ethylene (EBGMA) were studied. According to infrared spectroscopy results, whereas PP-g-MA was merely capable of reacting with hydroxyl groups of PET, epoxy groups of EBGMA could react with both the hydroxyl and carboxyl end groups of PET. The enhanced compatibilizing effect of EBGMA on PET/PP systems over PP-g-MA was also revealed by scanning electron microscopy and mechanical experiments. From frequency and temperature sweep rheological experiments, the dynamic characteristics of the compatibilized blends found to be improved in comparison with those of the uncompatibilized system. Such enhancement was interpreted as a result of the higher miscibility of the compatibilized blends which was further supported by Cole–Cole plot analyses.     

Influence of degree of grafting and grafting temperature on the permeabilities of grafted polypropylene membranes

Polypropylene dialysis membranes were prepared using cobalt-60 gamma radiation to directly graft 2-hydroxyethyl methacrylate (HEMA) onto polypropylene (PP) membranes. The surface structures of both the grafted membranes and the PP membrane were observed by using FTIR–PAS and ESCA methods. The X-ray diffraction diagrams of the PP and PP-g-HEMA membranes indicated a transformation process of the β-form toward the α-form crystallinity with increasing degree of grafting. The SEM data of the membrane grafted under a low grafting temperature showed many spheres of PHEMA embedded in the PP matrix, whose size was well distributed and increased with the degree of grafting. The influences of the degree of grafting and grafting temperature on the permeabilities of PP-g-HEMA membranes toward urea and creatinine were studied in a dialyzer. In all cases, the PP-g-HEMA membrane obtained under higher grafting temperature showed higher permeability toward those solutes. The permeation coefficients of urea and creatinine through the PP-g-HEMA membrane obtained at 59°C were about 10.4 and 28.8 times that through the PP membrane, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:83–89, 1998     

Compatibilization effectiveness of maleated polypropylene compared to organoclay in PBT/PP blends

The compatibilization efficiency of a conventional compatibilizer (PP-grafted maleic anhydride) is compared with an organoclay of hydrophilic modifier (Cloisite 30B) in poly(butylene terephthalate)/polypropylene (PBT/PP) immiscible polymer blend. Moreover, the effect of PP-grafted maleic anhydride (PP-g-MA) on localization of Cloisite 30B organoclays is investigated, in this research. Accordingly, PBT/PP blends containing PP-g-MA, organoclay and PP-g-MA/organoclay are prepared by melt mixing method. According to morphological analysis, organoclays are more efficient than PP-g-MA in dispersion and distribution of droplets in PBT/PP blend. Additionally, the size of dispersed-droplets in PBT/PP/organoclay nanocomposite is lower than PBT/PP/PP-g-MA/organoclay sample. From X-ray diffractometry (XRD) and transmission electron microscopy illustrations, it is shown that organoclays represent the higher level of intercalation structure in PBT/PP/organoclay compared to PBT/PP/PP-g-MA/organoclay nanocomposite. PBT/PP/Organoclay nanocomposite indicates higher viscosity and elasticity in comparison with PBT/PP/PP-g-MA/organoclay, as well. The present subject can be explained by the role of PP-g-MA in transferring some parts of organoclays from PBT matrix into PP droplets which hinders the break-up of dispersed-droplets. According to non-linear viscoelastic properties, PBT/PP/organoclay sample shows stronger stress overshoots than PBT/PP/PP-g-MA/organoclay in start-up of shear flow. Modified De Kee-Turcotte model is studied to investigate the yield stress and viscoelastic behavior of different samples. PBT/PP/Organoclay nanocomposite shows higher yield stress compared to PBT/PP blend filled by PP-g-MA/organoclay system.     

Rheological properties and interfacial tension of polypropylene-poly(styrene-co-acrylonitrile) blend containing compatibilizer

Rheological and morphological properties of the polypropylene (PP) and poly(styrene-co-acrylonitrile) (SAN) blend containing polypropylene-g-poly(styrene-co-acrylonitrile) (PP-g-SAN) was studied by advanced rheometric expansion system (ARES) and scanning electron microscopy (SEM). Blends of the PP-SAN (20/80) with compatibilizer of the PP-g-SAN, ranging from 0 to 20 wt% (phr) were prepared using a twin screw extruder. In the study of the complex viscosity of the PP-SAN (20/80) blend, the complex viscosity of the blend showed maximum value in the 1.0 phr PP-g-SAN copolymer content, which suggested that the compatibilizing effect of the PP-g-SAN copolymer was achieved. From the morphological studies, the PP-SAN (20/80) blend showed droplet dispersion type morphology, and the PP droplet size showed minimum value (0.44 μm) in the 1.0 phr PP-g-SAN copolymer content. The interfacial tension of the PP-SAN (20/80) blend was determined from the morphological studies and form relaxation time using the Palierne and the Choi and Schowalter models and showed minimum value in the 1.0 phr PP-g-SAN copolymer content in each models. The results of the interfacial tension was consistent with the results obtained from the rheological and morphological studies of the PP-SAN (20/80) blend. From the results of the morphological, rheological studies and the values of the interfacial tension, it was suggested that the compatibility of the PP-SAN (20/80) blend increased more in the 1.0 phr PP-g-SAN copolymer content.     

Excellent tensile ductility in highly oriented injection-molded bars of polypropylene/carbon nanotubes composites

Multi-wall carbon nanotubes (MWNTs) grafted with alkyl chain were used for reinforcement of polypropylene (PP). For achieving excellent tensile properties, the as-prepared PP/MWNTs composites were subjected to a unique injection molding, as so-called dynamic packing injection molding, to induce a highly oriented structure with both PP chains and MWNTs aligned along the shear flow direction. Not only Young's modulus and tensile strength were enhanced, as expected for oriented materials, but also more importantly composites containing only 0.1-0.3 wt% MWNTs were much ductile compared with the polymer matrix. The addition of PP-g-MMA made a drop in the elongation at break to only 15%; however, it could be improved to 80-100% after incorporation of small amount of MWNTs. This improvement in ductility could be ascribed to: (1) the increased mobility of both the PP chains and MWNTs, as they are oriented along tensile deformation direction and (2) the bridging effect of the oriented MWNTs on the crack development during tensile failure.     

Structure and properties of polypropylene-based nanocomposites: Effect of PP-g-MA to organoclay ratio

The structure-property relationships of polypropylene (PP)-based nanocomposites prepared by melt processing have been investigated with a main focus on the ratio of polypropylene grafted with maleic anhydride (PP-g-MA) to organoclay. The morphological observations by transmission electron microscopy and X-ray diffraction are presented in conjunction with the mechanical, rheological and thermal expansion properties of these nanocomposites. Detailed morphological studies and subsequent quantitative particle analyses for the dispersed clay phase reveal that the aspect ratio of clay particles decreases as the amount of clay increases, and it increases as the amount of PP-g-MA increases. The rheological properties suggest that the extent of a percolation network can be enhanced by increasing the number of organoclay particles at a fixed ratio of PP-g-MA to organoclay and by increasing the degree of exfoliation at fixed clay content. However, mechanical and thermal expansion behaviors do not improve correspondingly in all cases because of the reduction of matrix properties by PP-g-MA. The reduction of the modulus and the increase in the expansion of the polymer matrix caused by the presence of PP-g-MA are compared to the prediction of the Chow model. Clearly, the amount of PP-g-MA added along with its lower crystallinity are important factors affecting the mechanical and thermal expansion properties of PP-based nanocomposites.     

Effect of blend ratio on bulk properties and matrix-fibril morphology of polypropylene/nylon 6 polyblend fibers

Ternary blends of polypropylene (PP), nylon 6 (N6) and polypropylene grafted with maleic anhydride (PP/N6/PP-g-MAH) as compatibilizer with up to 50 wt% of N6 were investigated. PP-g-MAH content was varied from 2.5 to 10%. Blends of the two polymers PP/N6 (80/20) without the compatibilizer were also prepared using an internal batch mixer and studied. The ternary blends showed different rheological properties at low and high shear rates. The difference depended on the amount of N6 dispersed phase. Co-continuous morphology was observed for the blend containing 50% N6. This blend also exhibited higher viscosity at low shear rate and lower viscosity at high shear rates than the value calculated by the simple rule of mixture. At higher shear rates, viscosity was lower than that given by the rule of mixture for all blend ratios. An increase in viscosity was observed in the 80/20 PP/N6 blend after the concentration of the interfacial agent (PP-g-MAH) was increased. Polyblends containing up to 30% N6 could be successfully melt spun into fibers. DSC results showed that dispersed and matrix phases in the fiber maintained crystallinity comparable to or better than the corresponding values found in the neat fibers. The dispersed phase was found to contain fibrils. By using SEM and LSCM analyses we were able to show that the N6 droplets coalesced during melt spinning which led to the development of fibrillar morphology.     

Synthesis and hydrophilic property of polypropylene-graft-poly(polyethylene glycol-methacrylate) (PP-g-P(PEGMA))

Polypropylene-graft-poly(polyethylene glycol-methacrylate) (PP-g-P(PEGMA)), which is a hydrophobic-hydrophilic graft copolymer, was synthesized by a combination of an atom transfer radical polymerization (ATRP) of PEGMA with brominated polypropylene (PP-Br), which was synthesized from PP-OH prepared by metallocene-catalyzed copolymerization. Its structure was confirmed by ¹H NMR and GPC analyses. Transmission electron microscope (TEM) micrographs of PP-g-P(PEGMA) revealed the nanometer level microphase-separation morphology between the PP segment and the P(PEGMA) segment. The obtained PP-g-P(PEGMA) showed water-absorbing property as well as thermostability.     

Synthesis and characterization of macromolecular surface modifier PP-g-PEG for polypropylene

A novel macromolecular surface modifier, polypropylene-grafted-poly(ethylene glycol) copolymer (PP-g-PEG), was synthesized by coupling polypropylene containing maleic anhydride with monohydroxyl-terminated poly(ethylene glycol). The effects of the reaction condition on the graft reactions were studied. The copolymers were characterized by IR, ¹H NMR, thermogravimetry (TG) and differential scanning calorimetry (DSC). The results indicated that the graft reactions were hindered by increasing the molecular weight of PP or PEG. The graft copolymer was found to have a higher initial thermal degradation temperature and lower crystallization capacity as compared with pure PP, and the side chain of PEG hindered the PP chain from forming a perfect β crystal. The thermal stability of PP-g-PEG decreased with the increasing content or molecular weight of PEG. The copolymers were blended with polypropylene to modify the surface hydrophilicity of the products. The results of attenuated total reflectance FTIR spectroscopy (ATR-FTIR) showed that PP-g-PEG could diffuse preferably onto the surface of the blends and be suitable as an effectual macromolecular surface modifier for PP. __________ Translated from Acta Polymerica Sinica, 2007, (2): 203–208 [译自:高分子学报]     

Dispersion of nanoclay into polypropylene with carbon dioxide in the presence of maleated polypropylene

The effect of maleic anhydride grafted polypropylene (PP-g-MA) on the mechanical and rheological properties of polypropylene (PP)–clay nanocomposites prepared with nanoclay expanded with CO₂ and direct melt blending was studied. The results from the studies of the mechanical properties, rheological properties, and transmission electron microscopy show that when PP-g-MA was combined with the technique that used CO₂, greater enhancements in the mechanical properties and degree of dispersion of nanoclay in PP were observed. Furthermore, yieldlike behavior in the viscosity and a tail in the low-frequency behavior of the elastic modulus was attributed to the reaction of PP-g-MA with the nanoclay surface and not exfoliation. A fairly well-dispersed morphology was observed for concentrations as high 6.8 wt % clay when the clay was expanded and mixed with CO₂. At this concentration, mechanical properties such as yield strength and modulus increased by as much as 13 and 69%, respectively, relative to the pure PP. Furthermore, the modulus of the composite samples prepared with PP-g-MA and CO₂ was some 15% higher than that of samples prepared by direct melt compounding (without the use of CO₂). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase behaviors of poly(oxyethylene)-grafted polypropylene copolymers

A family of amphiphilic graft copolymers were prepared from a maleated polypropylene (PP-g-MA) and various crystalline poly(oxyethylene)-segmented amines of 1000 to 3000 molecular weight. Structurally, these copolymers consist of polypropylene (PP) backbone and several crystalline poly(oxyethylene) (POE) pendants in the structure. In the observation of their phase behaviors by using a differential scanning calorimeter (DSC), the interference between the POE segments and PP backbone was found. In a particular case (PP-g-MA/ED-2001), the heat of POE crystallization did not show off in the cooling curve of the DSC, but appeared during the consecutive heating process. Generally, heating and cooling patterns of the DSC analyses showed the shifts of melting and crystallizing temperatures, depending on the length and the termini of POE, from those of the starting materials— PP-g-MA and POE amines. The TGA and optical microscopy observation further supported the DSC analyses.     

Rate of the activated anionic polymerisation of ε-caprolactam onto an isocyanate bearing polypropylene in the melt

This paper concerns the rate of the activated anionic polymerisation of ε-caprolactam (CL) onto 3-isopropenyl-α,α-dimethylbenzyl isocyanate bearing PP (PP-g-TMI) in the melt to form a graft copolymer with PP as backbone and PA6 as grafts. The polymerisation was catalysed by sodium ε-caprolactam (NaCL). The PP-g-TMI/NaCL/CL polymerisation system being heterogeneous, the polymerisation was carried out in a batch mixer. Emphasis was placed on the effects of temperature and the concentrations of NaCL and the isocyanate group in the form of PP-g-TMI on the polymerisation rate. Results suggested that if the polymerisation is to be carried out by a reactive extrusion process whose mean residence time is less than a few minutes, it is recommended that the polymerisation temperature be higher than 220 °C. Moreover, the molar ratio between NaCL and CL should be higher than 0.5 and at the same time that between the isocyanate group in the form of PP-g-TMI and NaCL, should be smaller than 4.