Toughening polylactide with epoxidized styrene–butadiene impact resin: Mechanical,morphological, and rheological characterization

Styrene–butadiene impact resin (SBC) was chosen as the toughening agent to improve the tensile toughness of polylactide (PLA). Epoxidized SBC (ESBC) with different epoxidation degree were prepared by epoxidation using in situ peroxoformic acid method and a series of PLA/SBC(ESBC) blends were prepared by melt blending. The elongation at break of the PLA/ESBC blends was greatly improved, which was reflected in the slight decrease in the tensile strength and tensile modulus. Moreover, the tensile strength and tensile modulus were not significantly affected by the epoxidation degree of ESBC. For example, the incorporation of ESBC28.8% (30 wt %) to PLA caused an obvious increment of elongation at break from 3.5% of pure PLA to 305.0%, while the tensile modulus and tensile strength decreased to 80 and 78% of pure PLA, respectively. Scanning electron microscopy observations of cryo‐fractured surface morphology and particle size analysis demonstrated that the compatibility of the PLA/ESBC blends was improved significantly compared to PLA/SBC blend. PLA/ESBC(70/30) blends exhibited shear‐thinning behavior over the range of the studied shear rate. With an increase in shear rate, the non‐Newtonian index of the blends decreased gradually. Furthermore, the flow behavior of PLA/ESBC(70/30) blends was more sensitive to the shear rate than pure PLA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46058.     

Toughening polylactide with a catalyzed epoxy‐acid interfacial reaction

Polylactide (PLA) is a promising material, with favorable modulus, renewable sources, and biodegradability. However, its low extension at break (4–7%) and toughness (notched Izod, 26 J/m) limit its applications (Anderson et al., Polym. Rev., 48, 85 (2008)). PLA toughening has been the subject of recent reviews, and is the basis for several commercial products. This work aims to increase PLA toughness using rubbery, linear low‐density polyethylene (LLDPE), glycidyl methacrylate functional PE compatibilizer (EGMA), and novel catalysts that promote copolymer formation at the interface of immiscible blends of PLA and EGMA/LLDPE. Droplet size was reduced from 2.7 µm to 1.7 µm with addition of 5 wt% EGMA, and further to 1.0 µm with the addition of cobalt octoate catalyst. Extension at break of 200% is achieved with only 5 wt% EGMA, 15 wt% LLDPE, and 0.01 M cobalt octoate, leading to an increase in tensile toughness of over an order of magnitude (compared to neat PLA). This work demonstrates that catalysts can reduce the amount of reactive compatibilizer necessary to achieve a given PLA toughness. POLYM. ENG. SCI., 58:28–36, 2018. © 2017 Society of Plastics Engineers     

Toughening epoxy resins with solid acrylonitrile–butadiene rubber

The feasibility of using solid acrylonitrile–butadiene rubbers (NBR) with 19 and 33% w/w acrylonitrile to toughen diglycidyl ether of bisphenol A (DGEBA) epoxy resins has been investigated. Thermal analysis experiments revealed a two‐phase morphology of these rubber‐modified epoxies. However, the higher content of acrylonitrile in the rubber caused better compatibility between NBR and the epoxy resin. The rubber with 33% acrylonitrile was found to be an effective toughening agent for DGEBA epoxy resins. Fracture surface studies and also the high tensile strength of crosslinked high molecular weight NBR suggest that the toughening effect should arise from rubber bridging and tearing mechanisms. © 2000 Society of Chemical Industry     

Structural morphology and properties of star styrene–isoprene–butadiene rubber and natural rubber/star styrene–butadiene rubber blends

Star styrene–isoprene–butadiene rubber (SIBR) was synthesized with a new kind of star anionic initiator made from naphthalene lithium and an SnCl₄ coupled agent. The relationship between the structure and properties of star SIBR was studied. Star block styrene–isoprene–butadiene rubber (SB‐SIBR), having low hysteresis, high road‐hugging, and excellent mechanical properties, was closer to meeting the overall performance requirements of ideal tire‐tread rubber according to a comparison of the morphology and various properties of SB‐SIBR with those of star random SIBR and natural rubber/star styrene–butadiene rubber blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 336–341, 2004     

Preparation of poly(methyl methacrylate‐co‐butyl methacrylate) nanoparticles and their reinforcing effect on natural rubber

Poly(methyl methacrylate‐co‐butyl methacrylate) [P(MMA‐co‐BMA)] nanoparticles were synthesized via emulsion polymerization, and incorporated into natural rubber (NR) by latex compounding. Monodispersed, core‐shell P(MMA‐co‐BMA)/casein nanoparticles (abbreviated as PMBMA‐CA) were produced with casein (CA) as surfactant. The chemical structure of P(MMA‐co‐BMA) copolymers were confirmed by ¹H‐NMR and FTIR analyses. Transmission electron microscopy demonstrated the core–shell structure of PMBMA‐CA, and PMBMA‐CA homogenously distributed around NR particles, indicating the interaction between PMBMA‐CA and NR. As a result, the tensile strength and modulus of NR/PMBMA‐CA films were significantly enhanced. The tensile strength was increased by 100% with 10% copolymer addition, when the molar ratio of MMA:BMA was 8:2. In addition, scanning electron microscopy and atomic force microscopy results presented that the NR/PMBMA‐CA films exhibited smooth surfaces with low roughness, and PMBMA‐CA was compatible with NR. FTIR‐ATR analyses also suggested fewer PMBMA‐CA nanoparticles migrated out of NR. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43843.     

Toughening effects of nucleating agent on impact polypropylene copolymer

In this study, the impact polypropylene copolymer (IPC) blended with the sorbitol‐based nucleating agent (NA) NX8000 was prepared and then characterized using a wide range of instrumentations. The results showed that the NA formed a fibril network which resulted in the increased viscosity of system and the decreased size of ethylene–propylene random copolymer (EPR) phase. The results of mechanical tests revealed “the brittle–ductile transition (BDT)” occurred while the ethylene content was between 3.5 wt % and 6 wt % and indicated that the impact strength of IPC was greatly improved by the addition of NX8000 when the EPR content was right over the critical value of BDT. The investigations provided valuable information for the further development of IPC materials and boarded its potential industrial applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40705.     

Toughening of polylactide by melt blending with linear low‐density polyethylene

Melt blending of polylactide and linear low‐density polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactide‐polyethylene (PLLA‐PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA‐PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA–;PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3757–3768, 2003     

Toughening of polylactide with natural rubber grafted with poly(butyl acrylate)

Natural rubber grafted with poly(butyl acrylate) (NR‐g‐PBA) in an attempt to toughen polylactide (PLA) was prepared by grafting butyl acrylate onto natural rubber (NR) through emulsion polymerization. The purified NR‐g‐PBA was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. NR‐g‐PBA/PLA blend and NR/PLA blend were prepared with a Haake internal melt mixer. The morphology and mechanical properties of the blends were investigated as a function of rubber content. Observations by scanning electron microscopy showed that the spherical‐particle‐dispersed phase appearing in the NR/PLA blend was not found in the NR‐g‐PBA/PLA blend, which showed that NR grafted with PBA is compatible with PLA, and accounted for the efficient toughening effect on PLA. The elongation at break and the impact strength were significantly improved with an increase in NR‐g‐PBA content. The thermal stability of PLA decreased when blended with NR but was retained with NR‐g‐PBA. Copyright © 2011 Society of Chemical Industry     

Tin‐coupled star‐shaped block copolymer of styrene and butadiene (II) properties and application

A novel tin‐coupled star‐shaped block copolymer (SB‐B)₄Sn was synthesized by anionic polymeric techniques. This new copolymer exhibited two different types: One was star‐shaped polybutadiene‐b‐poly(butadiene‐ran‐styrene) (S‐PB‐PSB), and the other was star‐shaped polybutadiene‐b‐poly(butadiene‐ran‐styrene)‐b‐polystyrene (S‐PB‐PSB‐PS). In this article, properties of (SB‐B)₄Sn were contrasted with that of tin‐coupled star‐shaped random styrene‐butadiene rubber (S‐SBR) and S‐SBR/cis‐BR blend rubbers. Physical property testing results showed that (SB‐B)₄Sn possessed good mechanical properties like S‐SBR. Rheological study indicated that these star‐shaped block copolymers had good processing properties. Rubber processing analyzer (RPA) spectra showed that the dispersion of additives in (SB‐B)₄Sn and S‐SBR/cis‐BR blend rubber was much better than that in S‐SBR. Dynamic mechanical thermal analyzer (DMTA) spectra showed that (SB‐B)₄Sn had a good combination of low rolling resistance and high wet skid resistance, which made it satisfactory materials to produce high performance tire tread. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enzymatic degradation of polylactide/layered silicate nanocomposites: Effect of organic modifiers

Biodegradable polylactide (PLA)/layered silicate nanocomposites have been prepared via solution route using two different kinds of organically modified nanoclays. The nanostructure as observed from wide‐angle X‐ray diffraction indicates intercalated hybrids and the extent of intercalation depends on the type of organic modifiers used. Melt‐quenched PLA and its nanocomposites are predominantly amorphous but, after annealing, they are fairly crystalline. The nanohybrids show significant improvement in thermal properties as compared to neat polymer. The nature of interaction between nanoclays and matrix polymer depends on the organic modifiers used, as evident from varying heat of fusion and shifting of Fourier transform infrared peaks. The nanoclays act as nucleating agent, and thereby, control the spherulite dimension of the matrix. The comparison of biodegradation of PLA and its nanocomposites has been studied in enzyme, compost, and buffer solution. Biodegradability of PLA has significantly been enhanced in the presence of nanoclays and the rate varies on organic modifications. The surface morphology, before and after enzymatic degradation, confirms the relative rate of degradation through laser scanning confocal images, scanning electron microscope, and atomic force microscope. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of electron‐beam irradiation on ethylene–methyl acrylate copolymer

Ethylene–methyl acrylate copolymer (Elvaloy 1330) was irradiated by an electron beam at different levels of radiation both in the presence and absence of a trimethylolpropane trimethacrylate sensitizer at various dosages of incorporation. The mechanical, thermal, and electrical properties of these samples were compared. The mechanical properties were observed to reach an optimum maximum around 6 Mrad of irradiation and 1 phr of sensitizer incorporation. Furthermore, an increase in either the radiation dose or the sensitizer level helped very little to further modify the properties. The thermal properties as determined by the thermogravimetric analysis and differential scanning calorimetry studies were quite supportive of the observation made during the study of the mechanical properties. The thermal stability of the irradiated samples underwent an increase with increasing electron‐beam dosage. In a manner similar to those of the mechanical properties, the increase in thermal stability was found to reach a maximum at a particular level of treatment and sensitizer incorporation, beyond which there was marginal or no effect at all. The α transition temperature underwent a substantial increase with increasing crosslink density, as evidenced by the increase in gel content with increasing proportion of electron‐beam radiation dose. The other glass‐transition temperature, however, appeared to remain unaffected. The electrical properties, as described by the dielectric constant, volume resistivity, and breakdown voltage, appeared to be affected very little by the electron‐beam radiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Upgrading of acrylonitrile–butadiene copolymer properties using natural rubber–graft–N‐(4‐aminodiphenylether) acrylamide

The grafting of ADPEA onto natural rubber was executed with UV radiation. Benzoyl peroxide was used to initiate the free‐radical grafting copolymerization. Natural rubber‐graft‐N‐(4‐aminodiphenylether) acrylamide (NR‐g‐ADPEA) was characterized with an IR technique. The ultrasonic velocities of both longitudinal and shear waves were measured in thermoplastic discs of NBR vulcanizates as a function of aging time. Ultrasonic velocity measurements were taken at 2 MHz ultrasonic frequency using the pulse echo method. We studied the effect of aging on the mechanical properties and the swelling and extraction phenomena for acrylonitrile–butadiene copolymer (NBR) vulcanizates, which contained the prepared NR‐g‐ADPEA and a commercial antioxidant, N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine. The prepared antioxidant enhanced both the mechanical properties of the NBR vulcanizates and the permanence of the ingredients in these vulcanizates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Hollow polylactide microcapsules with controlled morphology and thermal and mechanical properties

Hollow polylactide microcapsules were prepared by multistage premix membrane emulsification of polylactide/dichloromethane/oil solutions in water (nonsolvent). The effects of the different oils on the morphology, thermal, and mechanical properties of the hollow microcapsules were investigated. All oils resulted in hollow microcapsules with controlled shell thickness of ～60 nm except for eugenol, in which irregular, massive capsules were obtained. The properties of the microcapsules were strongly dependent on the oil used, for example the thermal transition temperatures found for hollow capsules were lower than for solid particles prepared without any oil. The crystallinity and transition temperatures of the capsules prepared with linear alkanes were higher than for cyclic alkanes; terpenes gave the lowest transition temperatures. The shell stiffness, measured with atomic force microscopy, was highly dependent on the oil used. Capsules prepared with dodecane showed higher stiffness (3.3 N m^?1) than with limonene (2 N m^?1) or cyclohexane (1.4 N m^?1). © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Toughening of poly(l‐lactide) modified by a small amount of acrylonitrile−butadiene−styrene core‐shell copolymer

A small amount of acrylonitrile‐butadiene‐styrene (ABS) core shell copolymer particles are used to improve the toughness of poly(l ‐lactide) (PLLA) matrix. The incorporation of ABS copolymer dramatically increased the elongation yield at break of PLLA. For PLLA blend with 6.0 wt % ABS copolymer particles, the elongation yield at break increased by 28 times and the notched impact strength improved by 100% comparing with those of neat PLLA. Fourier transformed infrared (FTIR) and dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) measurement results indicated that the special polarity interaction between ester group of PLLA matrix and nitrile group of PSAN shell phase enhanced the interfacial adhesion between PB rubber phase and PLLA matrix and promoted the fine dispersion of ABS particles in PLLA matrix. Meanwhile, ABS core shell particles also showed a certain extent of effects on the crystallinity behavior of PLLA. A small amount of ABS particles became the nucleating sites, and then the degree of crystallinity of PLLA/ABS blends increased. However, the notched impact of PLLA blends decreased because of the aggregation of more ABS particles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42554.     

Influence of the molecular weight of ethylene vinyl acetate copolymers on the flow and mechanical properties of uncompatibilized polystyrene/ethylene–vinyl acetate copolymer blends

Rubber‐toughened polystyrene (PS) has been extensively studied and is a well‐established material. However, the use of thermoplastic elastomers to toughen PS is new and not well understood. In this study, three types of ethylene vinyl acetate (EVA) copolymers with the same vinyl acetate (VA) content (27.2–28.8 wt %) but with different melt flow indexes (MFI; g (10 min)⁻¹) of 365–440 (Elvax 210), 38.0–48.0 (Elvax 240) and 2.6–3.4 (Elvax 265) were used as impact modifiers for PS. The uncompatibilized blend systems at different compositions were prepared using a twin‐screw extruder and injection moulding to produce the required test pieces. The viscosity of the dispersed phase (EVA) has a significant effect on the mechanical properties of the blends. Rheological studies show that uncompatibilized PS/EVA265 blends exhibit some degree of compatibility when the amount of EVA265 added is below 30 wt %. These results indicate that EVA265 with the lowest melt flow index or highest molecular weight is the most effective impact modifier for PS. The mechanism for such behaviour is still unclear. © 2001 Society of Chemical Industry     

Blends of LDPE/chitosan using epoxy‐functionalized LDPE as compatibilizer

LDPE and chitosan blends were prepared using an epoxy‐functionalized polyethylene as compatibilizing agent for improving interfacial adhesion. Compatibilization improved both tensile and flexural properties (with values approaching close to that of neat LDPE) when compared with that of uncompatibilized blends. However, the elongation at break reduced due to the addition of rigid chitosan. Thermogravimetric analysis showed a two‐stage degradation, while differential scanning calorimetry exhibited reduced crystallinity for compatibilized blends. Biodegradation studies revealed increased biodegradability with increase in chitosan loading. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology and mechanical properties of PVC/straw‐fiber coated with liquid nitrile‐butadiene rubber composites

This study exhibited an approach of high‐value utilization of straw fiber (SF) in polymer composites. The rigid poly(vinyl chloride) [PVC]/SF and PVC/SF coated with liquid nitrile‐butadiene rubber (PVC/LNBR‐SF) composites were both fabricated by melt mixing. The chemical structure and crystal structure of LNBR‐SF were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X‐ray diffraction (XRD). The mechanical properties and micro‐structure of PVC/SF and PVC/LNBR‐SF composites were also studied. FTIR and XRD results showed that the chemical structure and crystal structure of SF did not change after modifying with LNBR. The mechanical properties analysis showed that the PVC/LNBR‐SF composites exhibited better tensile strength, elongation at break and notched impact strength than those of PVC/SF composites owing to the compatibilization and toughening effect of LNBR. Scanning electron microscope results indicated that the LNBR improved the dispersion of SF in PVC matrix to some extent. The interface adhesion between SF and PVC matrix with adding LNBR was also enhanced. These results suggested that PVC/LNBR‐SF composites exhibited promising potential for practical application in substitute for wood. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44119.     

Effect of an epoxy‐based bonding agent on the cure characteristics and mechanical properties of short‐nylon‐fiber‐reinforced acrylonitrile–butadiene rubber composites

The cure characteristics and mechanical properties of short‐nylon‐fiber‐reinforced acrylonitrile–butadiene rubber composites with and without an epoxy resin as a bonding agent were studied. The epoxy resin was a good interfacial‐bonding agent for this composite system. The minimum torque showed a marginal increase with the resin concentration. The maximum–minimum torque showed only a marginal change with the resin. The scorch time decreased with the fiber concentration and resin content. The tensile strength and abrasion resistance were improved and the tear resistance and resilience were reduced with the resin concentration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 532–539, 2006     

Morphology and micromechanical deformation behavior of styrene–butadiene block copolymers. IV. Structure–property correlation in binary block copolymer blends

The structure–property correlation in blends consisting of styrene/butadiene block copolymers forming alternating polystyrene (PS) and polybutadiene (PB) lamellae, and PS domains in rubbery matrix was investigated by different microscopic techniques (transmission electron microscopy, scanning force microscopy, and scanning electron microscopy), uniaxial tensile testing, and dynamic mechanical analysis. Unlike the pure lamellar block copolymer, the blends showed predominantly disordered wormlike morphology formed by the intermolecular mixing. These structures allowed a precise control of stiffness/toughness ratio of the blends over a wide range. The blends showed a gradual transition from predominantly viscoplastic to elastomeric behavior with increasing triblock copolymer content. The results demonstrated that the binary block copolymer blends provide the unique possibility of tailoring mechanical properties on the basis of nanostructured polymeric materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1219–1230, 2004     

Compatibilization of poly(lactic acid)/high impact polystyrene interface using copolymer poly(stylene‐ran‐methyl acrylate)

In this work, a surfactant‐free emulsion polymerization method was utilized to synthesize poly(styrene‐ran‐methyl acrylate) (PSMA) at a styrene/(methyl acrylate) mole ratio of 75/25 with the aim to compatibilize high impact polystyrene (HIPS)/poly(lactic acid) (PLA) interface. HIPS/PLA blends with different PSMA contents were prepared. Their phase morphologies, mechanical properties, and rheological and crystallization behaviors were investigated using scanning electron microscopy, tensile tests, rotational rheometry, and differential scanning calorimetry. The rheological results showed that the complex viscosity, storage moduli, and loss moduli of PLA/HIPS blends were enhanced with increasing PSMA content. A decrease in the degree of crystallinity of PLA in PLA/HIPS blends with the addition of PSMA was observed in the differential scanning calorimetry results. It was also revealed that the addition of a small amount of PSMA can effectively improve the compatibility and thus the interfacial adhesion of the PLA/HIPS blends, thereby reducing the size of the HIPS dispersion phase. When 1 wt % of PSMA was used, compared with the PLA/HIPS blends without PSMA, the tensile strength and notched Charpy impact strength of PLA/HIPS blends were improved by 95.3% and 104.8%, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45799.