Reactive compatibilization of blends of PET and PP modified by GMA grafting

The melt radical grafting of glycidyl methacrylate (GMA) onto isotactic polypropylene (PP) was carried out in Brabender internal mixer and the influence of reaction procedure, radical initiator concentration and addition of co-monomer (styrene) on the grafting efficiency was examined. The viscosity, the thermal behaviour and melt rheology of PP-g-GMA samples was then analysed as a function of grafted GMA content. Blends of poly(ethylene terephthalate) (PET) with PP and PP-g-GMA (5.2 wt% GMA), prepared in internal mixer, were characterised by SEM, DSC and melt viscosimetry. The morphological analysis of PET/PP-g-GMA blends (80/20, 50/50 w/w) pointed out a marked improvement of phase dispersion (with particle size of about 0.6 μm for 80/20 blend) and interfacial adhesion, as compared to non-compatibilized PET/PP blend. The results of mixing torque and thermal analysis supported the occurrence of in-situ compatibilization reaction between epoxy groups of GMA modified PP and carboxyl end-groups of PET in the melt.     

Oxazoline functionalization of polyethylenes and their blends with polyamides and polyesters

The compatibilization of blends of polyamide‐6 (PA6) with linear low density polyethylene (LLDPE) and of poly(ethylene terephthalate) (PET) with high density polyethylene (HDPE), by functionalization of the polyethylenes with oxazoline groups was investigated. Chemical modification of LLDPE and HDPE was carried out by melt free radical grafting with ricinoloxazoline maleinate. Blends preparation was made either with a two‐steps procedure comprising functionalization and blending, and in a single step in which the chemical modification of polyethylene with the oxazoline monomer was realized in situ, during blending. The characterization of the products was carried out by FTIR spectroscopy and scanning electron microscopy (SEM). The rheological and mechanical properties of the blends were also investigated. The results show that functionalization of the polyethylenes can be achieved by melt blending with ricinoloxazoline maleinate even in the absence of free radical initiators. The compatibilization of the blends enhances the dispersion of the minor phase significantly, increases the melt viscosity, and improves the mechanical properties. The one‐step preparation of the compatibilized blends was also found to be effective, and is thought to be even more promising in view of commercial application.     

Functionalization of Styrene-Olefin Block Copolymers by Melt Radical Grafting of Glycidyl Methacrylate and Reactive Blending with PET

Blocks copolymers styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and styrene-b-(ethylene-co-propylene) (SEP, SEPSEP), with different styrene content and number of blocks in the chain, were functionalized with glycidyl methacrylate (GMA) by melt radical grafting. The influence of monomer concentration, radical initiator and copolymer structure on the grafting degree was examined. The grafted copolymers were characterised by DSC and capillary rheometry. Blends of PET with functionalized SEBS and SEPSEP showed a marked improvement of phase morphology and elongation at break when compared to blends with unfunctionalized copolymers.     

Role of polyethylene‐graft‐glycidyl methacrylate compatibilizer on the biodegradation of poly(ε‐caprolactone)/cellulose acetate blends

Biodegradable polymers provide an attractive solution to reduce environmental pollution caused by the accumulation of plastic waste in landfills. In this study, the effect of polyethylene‐graft‐glycidyl methacrylate (PE‐g‐GMA) on the biodegradation of blends of poly(ε‐caprolactone) (PCL) and cellulose acetate (CA) (80/20, 60/40, 40/60, and 20/80 PCL/CA, w/w) was assessed by mass retention, tensile strength, and morphological properties. The principal fungal strains present in the soil after biodegradation were also identified. PCL and the blends containing 60% and 80% PCL showed greater mass loss and superficial change in simulated soil. PE‐g‐GMA increased the tensile strength retention during 3 months of aging in simulated soil. Scanning electron microscopy (SEM) indicated that pure PCL was more porous, which enhanced the hydrolysis and biodegradation of PCL. PE‐g‐GMA decreased the mass loss of the polymers, possibly by enhancing the interaction between PCL and CA, with the formation of hydrogen bonds between the carbonyl groups of PCL and the hydroxyl groups of CA. This effect was marked in blends with >40% PCL. Microbiological analysis revealed the presence of several species of fungi in the soil. Copyright © 2009 John Wiley & Sons, Ltd.     

Reactive processing of polymers: Structural characterisation of products by H and C NMR spectroscopy for glycidyl methacrylate grafting onto EPR in the absence and presence of a reactive comonomer

Grafted GMA on EPR samples were prepared in a Thermo-Haake internal mixer by free radical melt grafting reactions in the absence (conventional system; EPR-g-GMA_CONV) and presence of the reactive comonomer divinyl benzene, DVB (EPR-g-GMA_DVB). The GMA-homopolymer (poly-GMA), a major side reaction product in the conventional system, was almost completely absent in the DVB-containing system, the latter also resulted in a much higher level of GMA grafting. A comprehensive microstructure analysis of the formed poly-GMA was performed based on one-dimensional ¹H and ¹³C NMR spectroscopy and the complete spectral assignments were supported by two-dimensional NMR techniques based on long range two and three bond order carbon-proton couplings from HMBC (Heteronuclear Multiple Bond Coherence) and that of one bond carbon-proton couplings from HSQC (Heteronuclear Single Quantum Coherence), as well as the use of Distortionless Enhancement by Polarization Transfer (DEPT) NMR spectroscopy. The unambiguous analysis of the stereochemical configuration of poly-GMA was further used to help understand the microstructures of the GMA-grafts obtained in the two different free radical melt grafting reactions, the conventional and comonomer-containing systems. In the grafted GMA, in the conventional system (EPR-g-GMA_CONV), the methylene protons of the GMA were found to be sensitive to tetrad configurational sequences and the results showed that 56% of the GMA sequence in the graft is in atactic configuration and 42% is in syndiotactic configuration whereas the poly-GMA was predominantly syndiotactic. The differences in the microstructures of the graft in the conventional EPR-g-GMA_CONV and the DVB-containing (EPR-g-GMA_DVB) systems is also reported     

Compatibilizing effect of isocyanate functional group on polyethylene terephthalate/low density polyethylene blends

To evaluate the compatibilizing effects of isocyanate (NCO) functional group on the polyethylene terephthalate/low density polyethylene (PET/LDPE) blends, LDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared and blended with PET. The chemical reaction occurred during the melt blending in the PET/LDPE-g-HI blends was confirmed by the result of IR spectra. In the light of the blend morphology, the dispersions of the PET/LDPE-g-HI blends were very fine over the PET/LDPE blends. DSC thermograms indicated that PET microdispersions produced by the slow cooling of the PET/LDPE-g-HI blends were largely amorphous, with low crystallinity, due to the chemical bonding. The tensile strengths of the PET/LDPE-g-HI blends were higher than those of the PET/LDPE blends having a poor adhesion. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 447–453, 1998     

Rheological behavior of PET/HDPE in situ microfibrillar blends: Influence of microfibrils' flexibility

Poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) in situ microfibrillar reinforced blends were prepared via a slit die extrusion‐hot stretch‐quenching process. The in situ PET microfibrils contain various contents of a segmented thermoplastic elastomer, Hytrel 5526 (HT), hence having different flexibility as demonstrated by dynamic mechanical analysis. It is interesting that the simple mixing leads to nanoscale particles of the HT phase in PET phase, and the size of the HT particles is almost independent of the HT concentration, as observed from the scanning electron microscope micrographs which show that the microfibrils with different HT concentrations have almost the same diameter and smooth surfaces. The static rheological results by an advanced capillary rheometer show that the entrance pressure drop and the viscosity of the microfibrillar blends both reduced with increasing the microfibrils' flexibility. Furthermore, the data obtained by the temperature scan of the PET/HT/HDPE microfibrillar blends through a dynamic rheometer indicates that the more flexible microfibril leads to lower melt elasticity and slightly decreases the viscosities of blends, presenting a consistent conclusion about influences of the microfibrils' flexibility on the rheological behavior from the static rheometer measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1205–1216, 2007     

Synthesis of Starch-g-Poly(glycidyl methacrylate) and Its Blending with Poly(ϵ-caprolactone) and Nylon 610

Different amounts of glycidyl methacrylate (GMA) were grafted onto corn starch dispersed in water or dimethyl sulfoxide (DMSO) to yield starch-graft-poly(glycidyl methacrylate) (ST-g-PGMA). ST-g-PGMAW, obtained by grafting PGMA onto corn starch that was dispersed in water, showed a higher PGMA grafting content and a lower content of the homopolymerized PGMA than ST-g-PGMAD, which was prepared in DMSO. The modified starches were blended with poly(ϵ-caprolactone) (PCL) and nylon 610, respectively, and the tensile properties of the blends were measured by UTM. Mechanical properties of the biodegradable ST-g-PGMA/PCL blends were dependent on the PGMAD content grafted on starch. Without dramatic loss of the tensile properties of PCL, ST-g-PGMAW was melt blended with PCL. Meanwhile, an increase in the tensile modulus was observed in the ST-g-PGMAW/nylon 610 blend. When nylon 610 was reacted with ST-g-PGMAW in DMSO in the presence of triethylamine, the tensile modulus and strength were much higher than those of the pure nylon 610, and phase-separated domains of starch were not observed microscopically.     

Thermal,physico‐mechanical,and morphological properties of HDPE graft‐copolymerized with polystyrene

In this study, polystyrene was graft‐copolymerized onto high‐density polyethylene (HDPE) by in situ polymerization of styrene monomer to change the physico‐mechanical and thermal properties of HDPE. The grafting was carried out in a Brabender‐type static mixer by injecting styrene monomer directly into the molten HDPE in the presence of a free‐radical initiator (lauroyl peroxide or LP). The effect of wt% of styrene and initiator concentrations on thermal, physico‐mechanical, and morphological properties of HDPE was investigated. The neat and modified HDPE was characterized by differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and also by tensile strength and contact angle measurements. It was found that the increase in wt% of styrene and LP dosage reduced elongation at break, hygroscopic expansion and also the melting, and the crystallization temperatures of HDPE but increased its tensile strength. The tensile strength was increased from 14.6 MPa for the neat HDPE to 20.6 MPA for the 10 wt% of styrene grafted onto HDPE using 0.8% LP. Scanning electron microscopy results show that there was no phase separation, and the grafted polystyrene became integral part of HDPE. The results demonstrate that styrene could be used in melt compounding to improve various properties of HDPE. Copyright © 2015 John Wiley & Sons, Ltd.     

GMA熔融接枝EPDM的研究

以甲基丙烯酸缩水甘油酯（ＧＭＡ）为接枝单体，过氧化二异丙苯（ＤＣＰ）为引发剂，对三元乙丙胶（ＥＰＤＭ）进行了熔融接枝，在烃链上引入极性基团，以改善ＥＰＤＭ与极性聚合物的相容性。用差示扫描量热计（ＤＳＣ）研究了ＧＭＡ的聚合温度，用富里叶红外（ＦＴ－ＩＲ）、凝胶渗透色谱（ＧＰＣ）对接枝产物进行了表征。实验结果表明，产物的接枝率和凝胶量可以通过反应条件（温度、时间、反应物组成及加料方式）来控制。     

Effect of novel compatibilizers on the properties and morphology of PP/PC blends

A series of compatibilizers, including polypropylene (PP) grafted with 2‐tertbutyl‐6‐(3‐tertbutyl‐ 2‐hydroxy‐5‐methylbenzyl)‐4‐methylphenyl acrylic ester (BPA), glycidyl methacrylate (GMA), GMA/styrene (GMA‐st), and 2‐allyl bisphenol A (2A) were investigated for the purpose of improving the compatibility of PP/polycarbonate (PC) blends. PP‐g‐BPA shows a remarkable compatibilizing effect on PP/PC blends since it has similar group‐benzene ring with PC, and it is a sort of heat‐resistant antioxidant in the meantime, which can reduce the molecular degradation of PP during grafting and blending under high temperatures. Its compatibilizing effect was examined in terms of the mechanical, thermal properties, and morphologies. PP/PC blends show a decreasing and much more homogeneous size of dispersed PC particles through addition of a small amount of PP‐g‐BPA, and dynamic mechanical analysis (DMA) reveals a noticeable approach of T_g between PP and PC, indicating the improvement of the compatibility of PP/PC blends. Furthermore, styrene‐ethylene‐butylene‐styrene (SEBS) as a toughening rubber and a compatibilizer was applied to PP/PC blends. Around 25 wt% SEBS and 20 wt% PC lead to high toughness and strength of PP. Copyright © 2008 John Wiley & Sons, Ltd.     

Grafting of methacrylates and styrene on to polystyrene backbone via a “grafting from” ATRP process at ambient temperature

Well defined graft copolymers are prepared by “grafting from” atom transfer radical polymerization (ATRP) at room temperature (30 °C). The experiments were aimed at grafting methacrylates and styrene at latent initiating sites of polystyrene. For this purpose, the benzylic hydrogen in polystyrene was subjected to allylic bromination with N‐bromosuccinimide and azobisisobutrylnitirle to generate tertiary bromide ATRP initiating sites (Br? C? PS). The use of Br? C? PS with lesser mol % of bromide initiating groups results in better control and successful graft copolymerization. This was used to synthesize a series of new graft copolymers such as PS‐g‐PBnMA, PS‐g‐PBMA, PS‐g‐GMA, and PS‐g‐(PMMA‐b‐PtBA) catalyzed by CuBr/PMDETA system, in bulk, at room temperature. The polymers are characterized by GPC, NMR, FTIR, TEM, and TGA. Graft copolymerization followed by block polymerization enabled the synthesis of highly branched polymer brush, in which the grafting density can be adjusted by appropriate choice of bromide concentration in the polystyrene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3818–3832, 2007     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Thermoplastic elastomer based on high‐density polyethylene/natural rubber blends: rheological,thermal, and morphological properties

Thermoplastic elastomer (TPE) comprising air‐dried sheet or natural rubber (ADS or NR) and high‐density polyethylene (HDPE) was prepared by a simple blending technique. NR and HDPE were mixed with each type of phenolic compatibilizer (HRJ‐10518 or SP‐1045) or liquid natural rubber (LNR) at 180°C in an internal mixer. The mixing torque, shear stress, and shear viscosity of the blends increased with increasing amounts of NR. Positive deviation blend (PDB) for the blends containing active hydroxyl methyl phenolic resin in HRJ‐10518 or dimethyl phenolic resin in SP‐1045 was obtained. PDB was not observed for the blends without the compatibilizers or with LNR. The blends with HRJ‐10518 or SP‐1045 were compatible or partially compatible while the LNR blends were incompatible. In the phenolic compatibilized blends, NR dispersed in the HDPE matrix was found in the NR/HDPE blends of 20/80, 40/60, and 50/50 ratios. HDPE dispersed in NR matrix was obtained in the NR/HDPE blend of 80/20 ratio, and the co‐continuous phase was accomplished in the NR/HDPE blend of 60/40 ratio. The NR/HDPE blend at 60/40 ratio compatibilized with HRJ‐10518 and fabricated by a simple plastic injection molding machine exhibited higher ultimate tensile strength and elongation at break (EB). Incorporation of parafinic oil caused a decreasing tendency in tensile strength with increases in EB. The TPNRs exhibited high elastomeric nature with low‐tension set. Copyright © 2007 John Wiley & Sons, Ltd.     

Binary and ternary blends of high‐density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials

Binary blends of recycled high‐density polyethylene (R‐HDPE) with poly(ethylene terephthalate) (R‐PET) and recycled polystyrene (R‐PS), as well as the ternary blends, i.e. R‐HDPE/R‐PET/R‐PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R‐HDPE/R‐PET and R‐HDPE/R‐PS blends show phase inversion but at different compositions. The R‐PET was found to have much higher influence on the properties enhancement of the R‐HDPE compared to R‐PS, but at the phase inverted situation, a significant loss in the tensile strength of R‐HDPE/R‐PET blend was observed due to the weak interaction at this morphological state. However, the ternary blends with higher loading of second phase, namely greater than 50 wt% of R‐PET+R‐PS, demonstrated better mechanical properties than the binary blends with the same content of either R‐PET or R‐PS. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene compatibilizer on the recycled polypropylene and recycled high‐impact polystyrene blends

The recycled polypropylene/recycled high‐impact polystyrene (R‐PP/R‐HIPS) blends were melt extruded by twin‐screw extruder and produced by injection molding machine. The effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene copolymer (SEPS) used as compatibilizer on the mechanical properties, morphology, melt flow index, equilibrium torque, and glass transition temperature (T_g) of the blends were investigated. It was found that the notch impact strength and the elongation at break of the R‐PP/R‐HIPS blends with the addition of 10 wt% SEPS were 6.46 kJ/m² and 31.96%, which were significantly improved by 162.46% and 57.06%, respectively, than that of the uncompatibilized blends. Moreover, the addition of SEPS had a negligible effect on the tensile strength of the R‐PP/R‐HIPS blends. Additionally, the morphology of the blends demonstrated improved distribution and decreased size of the dispersed R‐HIPS phase with increasing the SEPS content. The increase of the melt flow index and the equilibrium torque indicated that the viscosity of the blends increased when the SEPS was incorporated into the R‐PP/R‐HIPS blends. The dynamic mechanical properties test showed that when the content of SEPS was 10 wt%, the difference of T_g decreased from 91.72°C to 81.51°C. The results obtained by differential scanning calorimetry were similar to those measured by dynamic mechanical properties, indicating an improved compatibility of the blends with the addition of SEPS.     

One‐step synthesis of poly(lactic‐co‐glycolic acid)‐g‐poly‐1‐vinylpyrrolidin‐2‐one copolymers

The radical polymerization of 1‐vinylpyrrolidin‐2‐one (NVP) in poly(lactic‐co‐glycolic acid) (PLGA) 50:50 at 100 °C leads to amphiphilic PLGA‐g‐PVP copolymers. Their composition is determined by FT‐IR spectroscopy. Thermogravimetric analyses agree with FT‐IR determinations. Saponification of the PLGA‐g‐PVP polyester portion allows isolating the PVP side chains and measuring their molecular weight, from which the average chain transfer constant (C_T) of the PLGA units is estimated. The MALDI‐TOF spectra of PVP reveal the presence at one chain end of residues of either glycolic acid‐ or lactic acid‐ or lactic/glycolic acid dimers, trimers and one tetramer, the other terminal being hydrogen. This unequivocally demonstrates that grafting occurred. Accordingly, the orthogonal solvent pair ethyl acetate—methanol, while separating the components of PLGA/PVP intimate mixtures, fails to separate pure PVP or PLGA from the reaction products. All PLGA‐g‐PVP and PLGA/PLGA‐g‐PVP blends, but not PLGA/PVP blends, give long‐time stable dispersions in water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1919–1928     

Polyolefin-functionalized graphene oxide and its GO/HDPE nanocomposite with excellent mechanical properties

An effective strategy for the polyolefin-functionalized graphene oxide (fGO) using two-step methods has been reported for GO/HDPE nanocomposite with excellent mechanical properties.     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

Effect of PPO‐g‐MA on structures and properties of PPO/PA6/short glass fiber composites

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6) blends were reactively compatibilized by maleic anhydride (MA) grafted PPO (PPO‐g‐MA) and reinforced by short glass fibers (SGF) via melt extrusion. An observation of the SGF‐polymer interface by scanning electronic microscope (SEM) together with etching techniques indicated that the PPO‐g‐MA played a decisive role in the adhesion of polymers to SGF. The rheological behavior was investigated by capillary rheometer, and the addition of PPO‐g‐MA, and SGF could increase the viscosity of the PPO/PA6 blends. The analysis of fiber orientation and distribution in the PPO/PA6/SGF composites showed PPO‐g‐MA favored to the random dispersion of SGF. The statistic analysis of SGF length showed that PPO‐g‐MA was helpful to maintain the fiber length during melt‐processing. For the composites at a given SGF content of 30 wt %, the addition of PPO‐g‐MA increased the tensile strength from 59.4 MPa to 97.1 MPa and increased SGF efficiency factor from 0.028 to 0.132. The experimental data were consistent with the theoretical predictions of the extension of Kelly‐Tyson model for tensile strength. The fracture toughness of the composites was investigated by single edge notch three‐point bending test. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2188–2197, 2009