Improvement in toughness of poly(l-lactide) (PLLA) through reactive blending with acrylonitrile-butadiene-styrene copolymer (ABS): Morphology and properties

Poly(l-lactide) (PLLA) was melt-blended with acrylonitrile-butadiene-styrene copolymer (ABS) with the aim of enhancing impact strength and elongation at break of PLLA, but not sacrificing its modulus and stiffness significantly. However, PLLA and ABS were found to be thermodynamically immiscible by simply melt blending and the formed blends show deteriorated mechanical properties. The reactive styrene/acrylonitrile/glycidyl methacrylate copolymer (SAN-GMA) by incorporating with ethyltriphenyl phosphonium bromide (ETPB) as the catalyst was used as the in situ compatibilizer for PLLA/ABS blends to improve the compatibility between PLLA and ABS. The reactive process during melt blending was investigated by Fourier transformed infra-red (FTIR). It showed that the epoxide group of SAN-GMA reacted with PLLA end groups under the mixing conditions and that the addition of ETPB accelerated the reaction. Phase structure and physical properties of the compatibilized blends were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic mechanical analysis (DMA), tensile tests and impact property measurements. It was found that the size of ABS domains in PLLA matrix is significantly decreased by addition of the reactive compatibilizer. The dynamic mechanical analysis revealed markedly shifted glass transition temperatures for both PLLA and ABS, indicating the improved compatibility between PLLA and ABS. The mechanical tests showed the compatibilized PLLA/ABS blends had a very nice stiffness-toughness balance, i.e., the improved impact strength and the elongation at break with a slightly loss in the modulus.     

Fully biodegradable blends of poly(butylene succinate) and poly(butylene carbonate): Miscibility, thermal properties, crystallization behavior and mechanical properties

Fully biodegradable poly(butylene succinate) (PBS) and poly(butylene carbonate) (PBC) blends were prepared by melt blending. Miscibility, thermal properties, crystallization behavior and mechanical properties of PBS/PBC blends were investigated by scanning electron microscopy (SEM), phase contrast optical microscopy (PCOM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and mechanical properties tests. The SEM and PCOM results indicated that PBS was immiscible with PBC. The WAXD results showed that the crystal structures of both PBS and PBC were not changed by blending and the two components crystallized separately in the blends. The isothermal crystallization data showed that the crystallization rate of PBS increased with the increase of PBC content in the blends. The impact strength of PBS was improved significantly by blending with PBC. When the PBC content was 40%, the impact strength of PBS was increased by nearly 9 times.     

Barrier,Mechanical, Morphological and Thermal Properties of Compatibilized High Density Polyethylene and Polyamide 6 Blends

Effectiveness of the content of maleic anhydride (MAH) and polyamide 6 (PA6) on mechanical, thermal, barrier (moisture and oxygen) properties of HDPE/PA6 blends was investigated. Blends of HDPE with PA6 were prepared by in situ method. Molau test and FTIR spectroscopy results confirmed the reactive compatibilization through grafting of MAH on HDPE and PA6 chains in PA6/HDPE blends. Low concentration of benzoyl peroxide (BPO) and MAH reduced the particle size, improved phase morphology and mechanical properties of PA6/HDPE blends. Decrease in mechanical properties of PA6/HDPE blends was observed at high concentration of BPO and MAH.     

Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.     

Structure,properties and interfacial interactions in poly(lactic acid)/polyurethane blends prepared by reactive processing

Polyurethane elastomers are promising candidates for the impact modification of PLA producing blends for example for biomedicine. Poly(lactic acid) (PLA)/polyurethane elastomer (PU) blends were prepared by reactive processing and physical blending as comparison. The blends were characterized by a number of techniques including microscopy (scanning electron microscopy, SEM, and atomic force microscopy, AFM), rotational viscometry, thermal (dynamic mechanical analysis, DMA), and mechanical (tensile) measurements. The analysis and comparison of the structure and properties of physical and reactor blends proved the successful coupling of the phases. Coupling resulted in more advantageous structure and superior mechanical properties compared to those of physical blends as confirmed by morphology, macroscopic properties and the quantitative estimation of interfacial interactions. Structural studies and the composition dependence of properties indicated the formation of a submicron, phase-in-phase structure which positively influenced properties at large PU contents. The results strongly support that reactive processing is a convenient, cost-effective and environmentally friendly technique to obtain blends with superior properties.     

Epoxy-modified, unsaturated polyester hybrid networks

Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin. The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin. Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to other epoxy resins.     

Physico-Mechanical Properties of Biodegradable Rubber Toughened Polymers

Summary: In this study, blends of poly(lactic acid) (PLA) with poly(butylene adipate-co-terephthalate) (PBAT) were studied for their mechanical and thermal properties as a function of the PBAT content. Tensile testing, impact testing, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA) and scanning electron microscopy (SEM) were used to characterize the blends. It was observed that PLA/PBAT blends maintained quite high modulus and tensile strength compared to pure PLA. Small amounts of PBAT improved the elongation at break and the impact resistance showing a debonding effect typical of rubber toughened systems.     

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.     

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.     

Use of maleic anhydride compatibilization to improve toughness and other properties of polylactide blended with thermoplastic elastomers

Polylactide (PLA) being a very brittle biopolymer could be toughened by blending with thermoplastic elastomers such as thermoplastic polyurethane elastomer (TPU) and thermoplastic polyester elastomer (TPE); unfortunately, these blends are immiscible forming round domains in the PLA matrix. Therefore, the purpose of this study was to investigate the effects of using maleic anhydride (MA) compatibilization on the toughness and other properties of PLA blended with TPU and TPE. MA grafting on the PLA backbone (PLA‐g‐MA) was prepared separately by reactive extrusion and added during melt blending of PLA/thermoplastic elastomers. IR spectroscopy revealed that MA graft might interact with the functional groups present in the hard segments of TPU and TPE domains via primary chemical reactions, so that higher level of compatibilization could be obtained. SEM studies indicated that PLA‐g‐MA compatibilization also decreased the size of elastomeric domains leading to higher level of surface area for more interfacial interactions. Toughness tests revealed that Charpy impact toughness and fracture toughness (K_IC and G_IC) of inherently brittle PLA increased enormously when the blends were compatibilized with PLA‐g‐MA. For instance, G_IC fracture toughness of PLA increased as much as 166%. It was also observed that PLA‐g‐MA compatibilization resulted in no detrimental effects on the other mechanical and thermal properties of PLA blends. Copyright © 2014 John Wiley & Sons, Ltd.     

MECHANICAL PROPERTIES OF SMC WHISKER REINFORCED HIGH DENSITY POLYETHYLENE COMPOSITES

A new type of SiO_2-MgO-CaO (SMC) whisker was used to modify high density polyethylene (HDPE).The melting behavior and crystallinity were investigated by differential scanning calorimetry (DSC).The dispersion of whiskers and interfacial adhesion in the prepared HDPE/SMC whisker composites were investigated by scanning electron microscopy (SEM).The mechanical properties were evaluated by mechanical tests and dynamic mechanical analysis (DMA).DSC data indicated that the melting temperature and the crystall...     

Solid-state relaxations in linear low-density (1-octene comonomer), low-density,and high-density polyethylene blends

Extensive thermal and relaxational behavior in the blends of linear low-density polyethylene (LLDPE) (1-octene comonomer) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated to elucidate miscibility and molecular relaxations in the crystalline and amorphous phases by using a differential scanning calorimeter (DSC) and a dynamic mechanical thermal analyzer (DMTA). In the LLDPE/LDPE blends, two distinct endotherms during melting and crystallization by DSC were observed supporting the belief that LLDPE and LDPE exclude one another during crystallization. However, the dynamic mechanical β and γ relaxations of the blends indicate that the two constituents are miscible in the amorphous phase, while LLDPE dominates α relaxation. In the LLDPE/HDPE system, there was a single composition-dependent peak during melting and crystallization, and the heat of fusion varied linearly with composition supporting the incorporation of HDPE into the LLDPE crystals. The dynamic mechanical α, β, and γ relaxations of the blends display an intermediate behavior that indicates miscibility in both the crystalline and amorphous phases. In the LDPE/HDPE blend, the melting or crystallization peaks of LDPE were strongly influenced by HDPE. The behavior of the α relaxation was dominated by HDPE, while those of β and γ relaxations were intermediate of the constituents, which were similar to those of the LLDPE/HDPE blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1633–1642, 1997     

Dynamic vulcanization of reclaimed tire rubber and high density polyethylene blends

Dynamic vulcanization of reclaimed tire rubber (RTR) and HDPE blends was reported. The effect of blend ratio, methods of vulcanization, i.e. sulphur, peroxide, and mixed system and the addition of compatibilizer on mechanical, thermal, and rheological properties were investigated. The blend with highest impact strength was obtained from 50/50 RTR/HDPE vulcanized by sulphur. Increasing the RTR content to more than 50% resulted in a decrease in the impact strength of blend, most likely due to the increasing carbon black content. For tensile strength, the presence of rubber and carbon black, however, unavoidably caused a drop in this property. Comparing among three methods of vulcanization, sulphur system seems to be the most effective method. Results from solvent swelling ratio, glass transition temperatures and viscosity indicated that the sulphur vulcanization created the highest degree of cross-link and filler-matrix interaction in the RTR/HDPE blend. Morphology of the blends was also assessed by scanning electron microscopy (SEM).     

Effect of Electron Beam Irradiation and Ethylene Vinyl Acetate Copolymer on the Properties of NBR/HDPE Blends

The mechanical and physical properties of blends based essentially on nitrile butadiene rubber (NBR) and different ratios of high density polyethylene (HDPE) up to 25 parts per hundred part of rubber (phr) before and after electron beam irradiation were investigated. The values of tensile strength (TS), tensile modulus at 50% elongation (M₅₀), hardness and gel fraction % (GF%) of NBR/HDPE blends were increased with both irradiation dose and by increasing the content of HDPE in the blends. On the other hand, the values of elongation at break (E _b ) were decreased with both irradiation dose and the content of HDPE in the blends. By loading NBR/HDPE (100/25) blend with ethylene vinyl acetate (EVA) copolymer the mechanical and physico-chemical properties were improved. Moreover, the degree of improvement is proportional to the loading content of EVA.     

PET/R‐PP/PC blends by two‐stage reactive extrusion: effect of polypropylene reactively functionalized with an oxazoline group on morphology and mechanical properties

A series of PET/R‐PP/PC blends was studied in a chemical modification involving reactive extrusion with a ricinyl‐2‐oxazoline maleinate. The interfacial reaction between blend components were studied by the differential scanning calorimetry (DSC) and the scanning electron microscopy (SEM). The static tensile and flexural properties, and impact resistance response of the blends were tested. The phase morphology of the blends was of interpenetrating network (IPN) type according to SEM results. The blends offer excellent mechanical properties and improved impact strength as an effect of chemical reactions on reactive extrusion, even if PET waste and low PC contents (below 20%) have been used.     

RELATIONSHIP BETWEEN INTERFACIAL REACTION AND BULK PROPERTIES OF PET/FUNCTIONALIZED HDPE BLENDS

High-density polyethylene (HDPE) grafted with blocked isocyanate group (BHI) was blended with polyethylene terephthalate (PET) to observe the relationship between interfacial chemical reaction and bulk properties of the blends. BHI was prepared by reacting ?-caprolactam (CPL) with hydroxyethyl methacrylate-isophorone diisocyanate (HI). Atomic force microscopy (AFM) analysis was used to confirm the interfacial chemical reaction of isocyanate (NCO) groups in the functionalized HDPE (HDPE-g-BHI) with carboxylic acid and hydroxyl end groups in PET after annealing. Interfacial topologies and mean roughness were observed. Morphological changes of the blends were observed by scanning electron microscopy (SEM) photographs. Measurements of elongation property and dynamic mechanical analysis (DMA) of the blends were also done.     

Reactive Blends of Poly(phenylene sulfide)/Hyperbranched Poly(phenylene sulfide)

Summary: Polymer blends consisting of linear poly(phenylene sulfide) (PPS) and hyperbranched PPS (HPPS) were obtained in melt. The solid-state properties of PPS and their blends were investigated by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), extraction measurement, differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). Blends prepared by melt mixing turned out to be reactive as shown by the TGA and extraction measurement. SEM indicated that no phase separation occurs in PPS/HPPS blends. The degree of crystallization of the blends decreased with increasing HPPS content. Both the storage modulus and loss modulus increased as HPPS content increasing.     

Study on damping properties of HVBR/EVM blends prepared by in situ polymerization

In comparison with normal damping rubbers such as natural rubber (NR), styrene butadiene rubber (SBR), isobutylene isoprene rubber (IIR) etc., Mo-based high vinyl polybutadiene rubber (HVBR) with high loss factor, excellent aging resistance and glass transition temperature closer to room temperature, is a promising damping material. The effective damping temperature range of HVBR could be further broadened by blending with ethylene-vinyl acetate (EVM) and the effects of blending methods (in situ polymerization blending or mechanical blending) and blending ratios on the damping properties and physical properties of HVBR/EVM blended rubber were studied. HVBR/EVM in situ polymerization blends was prepared by butadiene coordination polymerization by Mo-base catalyst in a toluene solution of EVM. The results of dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) of the blended vulcanizates via in situ polymerization blending revealed that the compatibility between HVBR and EVM was improved compared with that of the blended vulcanizates via the traditional mechanical blending method. The two phases of HVBR/EVM in situ polymerization blends had good dispersion and uniformity, the damping temperature range was significantly expanded, and the peak and valley of the damping temperature range were greatly improved. A blending ratio of HVBR/EVM900 = 100/40 showed the best damping properties and the effective damping temperature range (tanδ>0.3) was extended from −6.6 °C to 39.4 °C.     

Preparation and properties of POSS grafted polypropylene by reactive blending

The octavinyl polyhedral oligomeric silsesquioxane (POSS) grafted polypropylene (PP) was first prepared by reactive blending. The structure and properties of physical blending and reactive blending composites of PP/POSS were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA). WAXD analysis shows that the POSS in the reactive blending composites has better compatibility with PP than in the physical blending composites. The β-form crystalline hence disappears even the non-reactive POSS can act as an effective β-nucleating agents. DSC analysis shows the reactive blending composites have higher crystalline temperature while POSS in the physical blending composites have little effect on the crystalline temperature. The modulus of reactive blending composites increases in the presence of POSS, while that of the physical blending composites decreases with increasing POSS content.     

The influence of core-shell structured modifiers on the toughness of poly (vinyl chloride)

The core-shell structured grafted copolymer particles of polybutadiene grafted polymethyl methacrylate (PB-g-PMMA, MB) were prepared by emulsion polymerization. The MB particles were used to modify poly (vinyl chloride) (PVC) by melt blending. The mechanical properties of the PVC blends were investigated. The micro-morphology of the PVC blends was observed by scanning electron microscopy (SEM). The results indicated that the samples with the best impact strength could be obtained when the core-shell weight ratio of PB to PMMA is lower than 93:7, the mechanical properties correlated well with SEM morphologies, the addition of modifier with the ratio core to shell of 93:7 could reduce the domain size of the dispersed phase. Furthermore, the compatibility and properties of the blends were greatly enhanced and improved. The modifier particles could be well dispersed in the PVC matrix.