Toughening Of Poly Research Articles

Design of highly tough poly(l‐lactide)‐based ternary blends for automotive applications

ABSTRACTTechnical renewable poly(l‐lactide) (PLA)‐based blends represent an elegant way to achieve attractive properties for engineering applications. Recently, the miscibility between PLA and poly(methyl methacrylate) (PMMA) gave rise to new formulations with enhanced thermo‐mechanical properties but their high brittleness still remains a challenge to be overcome. This work here focuses on rubber‐toughened PLA/PMMA formulations for injection‐molding processes upon the addition of a commercially available ethylene‐acrylate impact modifier (BS). The miscibility between PLA and PMMA is not altered by the presence of BS but the incorporation of BS (17% by weight) into a PLA/PMMA matrix could enhance both ductility and toughness of PLA/PMMA blends for PMMA content up to 50 wt %. An optimum range of particle sizes (dn ∼0.5 µm) of the dispersed domains for high impact toughness is identified. These bio‐based ternary blends appear as promising alternatives to petro‐sourced blends such as ABS‐based blends in engineering injection‐molding parts. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43402.

Fabrication of super tough poly(lactic acid)/ethylene-co-vinyl-acetate blends via a melt recirculation approach: static-short term mechanical and morphological interpretation

The notched Izod impact strength of PLA/EVA blends was enhanced significantly with improved toughness making blends super tough.

Toughening of poly(L-lactide) by polyester-urethane networks based on castor oil-modified ɛ-caprolactone oligomers

Hydroxy-terminated castor oil-modified ɛ-caprolactone oligomers (CO-CLOns) with the theoretical degrees of polymerization per one arm, n = 3, 5 and 10 were prepared by ring-opening polymerizations of ɛ-caprolactone initiated with castor oil. The reactions of CO-CLOns and tolylene 2,4-diisocyanate (TDI) in the presence of poly(L-lactide) (PLLA) produced semi-interpenetrating polymer networks (SIPNs) composed of TDI-bridged CO-CLOn networks (TCO-CLOns) and PLLA. Although all the SIPNs had micro-phase separated morphologies, interfacial delamination was not observed for TCO-CLO5/PLLA 75/25, TCO-CLO10/PLLA 75/25 and TCO-CLO10/PLLA 50/50. The DSC analysis revealed that TCO-CLO10 is semi-crystalline, while TCO-CLO3 and TCO-CLO5 are substantially amorphous, that T g of TCO-CLOn decreased with increasing n value, and that the T g of each component for TCO-CLOn/PLLA was higher than that of the corresponding pure polymer. TCO-CLO10/PLLA 75/25 displayed the highest tensile toughness (8.54 MJ m−3) among all the SIPNs, which was much higher than that of poly(ɛ-caprolactone)/PLLA 75/25 blend.

Mechanical and Thermal Properties of Rubber Toughened Poly(Lactic Acid)

The effect of rubber toughening on mechanical and thermal properties of poly (lactic acid) (PLA) was investigated by using three types of rubbers; natural rubber (NR), epoxidized natural rubber (ENR) and core-shell rubber (CSR). The PLA/rubber blends were prepared by melt blending in a counter-rotating twin-screw extruder, where the rubber content for all blends was kept at 5 wt%. It was found that the addition of the rubbers increased the impact strength for all blends as compared to pure PLA. On the other hand, all PLA/rubber blends showed notable decrease of Young’s modulus especially for PLA/NR blend which decreased by 72% than pure PLA. Similarly, significant decrease of tensile strength was also observed for all PLA/rubber blends. PLA/ENR blend showed a morebalance mechanical properties with fairly significant improvement of impact strength and moderate decrease of tensile strength, Young’s modulus and elongation at break. In general, PLA/NR blend showed the highest overall impact strength, while the PLA/CSR showed the highest tensile strength and Young’s modulus among the blends. Thermal analysis revealed that the Tg of PLA decreased with incorporation of the three types of rubbers with NR showing the largest decrease. This study indicates that NR, ENR and CSR are effective in enhancing toughness of PLA

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

ABSTRACTA 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.

Flexible and Tough Poly(lactic acid) Films for Packaging Applications: Property and Processability Improvement by Effective Reactive Blending

This study demonstrates a practical means to overcome inherent brittleness problem of poly(lactic acid) (PLA) and make PLA feasible as packaging material. PLA with suitable processability is utterly required for package manufacturers, where flexible, tough PLA film is essential for packers and end users. Highly flexible PLA films with 60-fold increase in elongation at break (Eb) over that of the neat PLA were successfully produced by integrating effective reactive blending and economical film blowing process. The ‘two-step’ blending was used to prepare PLA compound; poly(butylene adipate-co-terephthalate) (PBAT – another biodegradable polymer) was first blended with 0.5–1% chain extender (epoxy-functionalized styrene acrylic copolymer) (ESA), followed by subsequent blending with PLA in twin-screw extruder. Blown films of reactive blend of PLA/PBAT/ESA (80/20/1) showed impressively high Eb of 250% versus a very low Eb of 4% for the neat PLA. Resulting blown films still possessed high modulus of 2 GPa, yield stress of 50–60 MPa and good toughness of ~100 MPa. Significant enhancement in the film's ductility was attributed to homogeneous blend with developed fine strand-like structure as a result of effective in situ compatibilization and good interfacial adhesion between the PLA and PBAT. PLA/PBAT/ESA blend also offered improved processability. Resulting films had acceptable haze of ~10% for common packaging, and clearer film close to PLA (≤2%) could be obtained by designing PLA skin layers in multilayer structure. Films of PLA/PBAT/1%ESA exhibit potential as packaging material; their mechanical and optical properties are comparable with or even exceed some existing films used in the market. Copyright © 2015 John Wiley & Sons, Ltd.

Toughening of poly(propylene carbonate) by carbon dioxide copolymer poly(urethane-amine) via hydrogen bonding interaction

A carbon dioxide copolymer poly(urethane-amine) (PUA) was blended with poly(propylene carbonate) (PPC) in order to improve the toughness and flexibility of PPC without sacrificing other mechanical properties. Compared with pure PPC, the PPC/PUA blend with 5 wt% PUA loading showed a 400% increase in elongation at break, whilst the corresponding yielding strength remained as high as 33.5 MPa and Young’s modulus showed slightly decrease. The intermolecular hydrogen bonding interaction in PPC/PUA blends was confirmed by FTIR, 2D IR and XPS spectra analysis, and finely dispersed particulate structure of PUA in PPC was observed in the SEM images, which provided good evidence for the toughening mechanism of PPC.

Toughening of poly(lactide) using polyethylene glycol methyl ether acrylate: Reactive versus physical blending

To design high‐performance poly(lactide)‐based materials (PLA‐based) with improved toughness, two approaches based on the reactive extrusion (REx) process are investigated and compared in the present study. The first approach relies upon a two‐step procedure using a REx‐polymerized poly(ethylene glycol) methyl ether acrylate, i.e., poly(AcrylPEG), as a highly‐branched and compatible impact modifier for PLA. The free‐radical polymerization proves to be very efficient with a peroxide initiator concentration of 1 wt%. The as‐produced poly(AcrylPEG) is then melt‐blended with PLA by extrusion. The resulting materials exhibit largely increase impact resistance (ca. 35 kJ/m2) in presence of 20 wt% poly(AcrylPEG) in comparison with neat PLA (2.7 kJ/m2), while moderate ductility (tensile elongation at break <40%) and limited plasticization effect are observed. The second “one‐step” approach consists in in situ grafting of AcrylPEG onto PLA backbone via a one‐stage REx. The resulting materials exhibit substantially improved impact resistance (ca. 102 kJ/m2) for AcrylPEG loading of 20 wt%, high ductility (tensile elongation at break of ca. 150%) and efficient plasticization. A detailed characterization of the morphology of the materials has been performed using PF‐QNM‐AFM to better elucidate the structure‐property relationships. POLYM. ENG. SCI., 55:1408–1419, 2015. © 2015 Society of Plastics Engineers

Super-tough Poly(butylene terephthalate) Materials: Blending with CSSP Nanoparticles

Core-shell structured polyacrylic (CSSP) impact modifiers, consisting of a rubbery poly(n-butyl acrylate) core and a rigid poly(methyl methacrylate) shell, were synthesized by seed emulsion polymerization. The CSSP modifier with core-shell weight ratio 75/25 was used to modify the toughness of poly(butylene terephthalate) (PBT) by melt blending. The CSSP morphology was confirmed by TEM and SEM. Dynamic mechanical analyses of PBT/CSSP blends showed two merged transition peaks of PBT matrix. Increasing CSSP content increased elongation at break and impact strength, but decreased tensile strength. The notch impact strength of PBT/CSSP blends with weight ratio 85/15 was eight times greater than pure PBT.

Strengthening and toughening of poly(L-lactide) composites by surface modified MgO whiskers

To improve both the strength and toughness of poly(L-lactide) (PLLA), fibrous-like MgO whiskers with diameters of 0.15–1μm and lengths of 15–110μm were prepared, and subsequently surface modified with L-lactide to obtain grafted MgO whiskers (g-MgO whiskers). The structures and properties of MgO whiskers and g-MgO whiskers were studied. Then, a series of MgO whiskers/PLLA and g-MgO whiskers/PLLA composites were prepared by solution casting method, for comparison, MgO particles/PLLA composite was prepared too. The resulting composites were evaluated in terms of hydrophilicity, crystallinity, dispersion of whiskers, interfacial adhesion and mechanical performance by means of polarized optical microscopy (POM), contact angle measurement, field emission scanning electron microscope (FSEM), transmission electron microscopy (TEM) and tensile testing. The results revealed that the crystallization rate and hydrophilicity of PLLA were improved by the introduction of MgO whiskers and g-MgO whiskers. The g-MgO whiskers can disperse more uniformly in and show stronger interfacial adhesion with the matrix than MgO whiskers as a result of the surface modification. Due to the bridge effect of the whiskers and the excellent interfacial adhesion between g-MgO whiskers and PLLA, g-MgO whiskers/PLLA composites exhibited remarkably higher strength, modulus and toughness compared to the pristine PLLA, MgO particles/PLLA and MgO whiskers/PLLA composites.

Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

This paper aims at improving the mechanical behavior of biobased brittle amorphous polylactide (PLA) by extrusion melt-blending with biobased semi-crystalline polyamide 11 (PA 11) and addition of natural halloysite nanotubes (HNT). The structure and properties of PLA/PA11/HNT blends were studied in terms of morphological, thermal and mechanical properties. The morphological analysis of the PLA/PA11/HNT blends shows a strong interface between the two polymeric phases due to hydrogen bonding, and the migration of HNTs towards PA 11 phase inducing their selective localization in one of the polymeric phases of the blend. A “salami-like” structure is formed revealing a HNTs-rich tubular-like (fibrillar) PA11 phase. Moreover, HNTs localized in the dispersed phase acts as nucleating agents for PA11. Blending PLA (80 wt.%) and PA11 (20 wt.%) increases PLA ductility (elongation at break, ɛr, is multiplied by more than 20), however at the slight expense of strength and stiffness. Further addition of HNTs (2 wt.%) further increases ductility (ɛr reaches 155 %, i.e. it is multiplied by more than 40) whereas tensile strength and modulus of PLA are unchanged and impact strength is more than doubled. The toughening mechanism is discussed based on the combined effect of resistance to crack propagation and nanotubes load bearing capacity due to the existence of the fibrillar structure. Thus, blending brittle PLA with PA11 and HNT nanotubes results in tailor-made PLA-based compounds with enhanced ductility without sacrificing stiffness and strength.

Thermal, mechanical and thermomechanical properties of tough electrospun poly(imide-co-benzoxazole) nanofiber belts

Electrospun PI-co-PBO nanofiber belts possessed superior thermomechanical properties.

Preparation of core-shell structured polyacrylic modifiers and effects of the core-shell weight ratio on toughening of poly(butylene terephthalate)

Core-shell structured polyacrylic (named CSSP) impact modifiers consisting of a rubbery poly(n-butyl acrylate) core and a rigid poly(methyl methacrylate) shell with a size of about 353 nm were prepared by seed emulsion polymerization. The CSSP modifiers with different core-shell weight ratios (90/10, 85/15, 80/20, 75/25, 70/30, 65/35 and 60/40) were used to modify the toughness of poly(butylene terephthalate) (PBT) by melt blending. It was found that the polymerization had a very high instantaneous conversion (> 95.7%) and overall conversion (99.7%). The morphology of the core-shell structure was confirmed by means of transmission electron microscopy. Scanning electron microscopy was used to observe the morphology of the fractured surfaces. Differential scanning calorimeter was used to study the crystallization behaviors of PBT/CSSP blends. The dynamic mechanical analyses of PBT/CSSP blends showed two merged transition peaks of PBT matrix, with the presence of CSSP core-shell structured modifier, that were responsible for the improvement of PBT toughness. The results indicated that the notch impact strength of PBT/CSSP blends with a core-shell weight ratio of 75/25 was almost 8.64 times greater than that of pure PBT, and the mechanical properties agreed well with the SEM observation.

Effect of blending with polyamidoamine (PAMAM) dendrimer on the toughness of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)

Different proportions of polyamidoamine (PAMAM) dendrimer were blended with poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) resin in chloroform for film casting. Differential scanning calorimetry and scanning electron microscopy were employed to characterize the PHBV/PAMAM composite films upon stretching and tangential breaking. The results indicated that with the addition of PAMAM dendrimer, the glass transition temperature of the PHBV/PAMAM composite films became more distinct, indicating that the blends had a greater toughness than pure PHBV. The calculated crystallinity values indicated that the crystallinity of the PHBV/PAMAM blends was lower than that of PHBV (0.09–56.18 % vs. 73.18 %, respectively). Moreover, the mechanical performance tests indicated that the addition of PAMAM dendrimer considerably increased the tangential breaking strength of PHBV from 24.08 kN/m to as high as 62.03 kN/m, whereas the tensile strength remained basically unchanged. The optimal toughening effect was observed with a PAMAM dendrimer content of 3.0 phr.

Toughening of Poly(Lactic Acid) by Blending with Poly(Ethylene-co-Octene)

Poly (lactic acid) or PLA is one of the most promising biodegradable and bio-based materials commercially available for the manufacturing of environmentally friendly plastic products. Although, PLA has high modulus and biodegradable property, its brittleness and low thermal stability are the disadvantages. Several means have been explored so as to overcome this drawback, i.e. copolymerization, addition of some additives as well as blending with other polymers. The polymer blending technique has attracted the most attention because of its simplicity and economical reason. It was reported that the addition of a polyolefin elastomer e.g. poly (ethylene-co-octene) or POE in PLA matrix can effectively improve its brittleness. The aim of this study is thus to investigate the effect of the amount of POE on mechanical properties of the polymer blends. POE was also modified with glycidyl methacrylate in order to improve the compatibility between the two polymers. The results pointed out that the impact strength of PLA markedly increased while tensile and flexural properties of the blends were slightly lower than that of neat PLA. It was also observed that the tensile and flexural properties were slightly higher when the modified POE was used rather than those with unmodified POE which indicated the improved interfacial compatibility between two polymers.

Toughening of poly(propylene carbonate) using rubbery non-isocyanate polyurethane: Transition from brittle to marginally tough

To overcome the brittleness of poly(propylene carbonate) (PPC), rubbery non-isocyanate polyurethane (NIPU) with rich hydrogen bonding moiety was synthesized for toughening PPC. Debonding phenomenon of NIPU was observed during the impact process of PPC/NIPU blends, which was beneficial for toughening PPC. When the NIPU loading increased to 10 wt%, the unnotched impact strength increased 3 times compared with neat PPC. The NIPU dispersed uniformly and a transition from brittle to marginally tough occurred when L/d reached a critical value, 1.74, where L and d were center-to-center distance and the diameter of the particle, respectively. The debonding of NIPU accounted for the increase of toughness, and shear yielding of the matrix was limited around the microvoids. When the NIPU loading reached 13 wt%, NIPU flocculated in the matrix leading to decline in toughness. The equilibrium between self-associating hydrogen bonding and intermolecular one formed between PPC and NIPU affected their miscibility and thereby the morphology of the blends.

Super Toughened Poly(L-lactide)/Thermoplastic Polyurethane Blends Achieved by Adding Dicumyl Peroxide

Dicumyl peroxide (DCP) was introduced into thermoplastic polyurethane (TPU) toughened poly(L-lactide) (PLLA) blends. The results showed that the presence of DCP at relatively high concentration (0.2–0.5 wt.%) not only resulted in the homogeneous distribution of TPU particles with largely decreased particle size but also improved the interfacial interaction between PLLA and TPU components. Consequently, super toughened PLLA/TPU blends with largely enhanced impact strength were achieved successfully. The toughening mechanism was analyzed based on the impact-fractured surface morphologies of samples. Further enhanced impact toughness could be achieved by introducing crystalline structure to PLLA matrix, which was realized by annealing treatment.

High‐impact toughness poly(vinyl chloride)/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer/acrylic resin blends: Thermal properties and toughening mechanism

High impact toughness poly(vinyl chloride) (PVC)/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer (70/30)/acrylic resin (ACR) blends were prepared. Incorporation of ACR did not play a negative role in thermal properties. The glass transition temperature, heat distortion temperature, and thermal stability remained constant as ACR content increased. With the addition of 10 phr (parts by weight per hundred parts of resin) of ACR, the impact strength increased by 20.0 times and 7.2 times compared with that of pure PVC and that of PVC/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer (70/30) blends, respectively. However, tensile strength and flexural properties decreased. The morphology changed from domain distortions to crazing with fibrillar plastic deformation as ACR content increased. The toughening mechanism varied from “shear yielding” to “craze with shear yielding,” which depended on the content of ACR. This study presents the finding that addition of ACR drastically improved impact toughness without sacrificing any heat resistance, and the enhanced impact strength could be at the same level of supertough nylon. J. VINYL ADDIT. TECHNOL., 21:205–214, 2015. © 2014 Society of Plastics Engineers

Toughening of poly(butylene terephthalate) by polyacrylic impact modifier

Core–shell structured polyacrylic (named ACR) impact modifiers consisting of a rubbery poly(n-butyl acrylate) (BA) core and a rigid poly(methyl methacrylate) shell with a size of about 310 nm were prepared by seed emulsion polymerization. The ACR modifiers with different core–shell weight ratios (85:15; 80:20; 75:25; 70:30) were used to modify the toughness of poly(butylene terephthalate) (PBT) by melt blending. It was found that the polymerization had a very high instantaneous conversion (>90 %) and overall conversion (98 %). The ACR latexes had an obvious core–shell structure confirmed by transmission electron microscope. The mechanical properties of the PBT/ACR blends were evaluated, and scanning electron microscope (SEM) was used to observe the fractured morphology. Dynamic mechanical analysis and differential scanning calorimeter were used to study the molecular movement and crystallization behaviors of PBT/ACR blends. The results indicated that with an appropriate value of the core–shell weight ratio, poly(BA) could disperse well in the matrix and the brittle–ductile transition point could emerge. As a result, the notch impact strength of PBT/ACR blends with a core–shell weight ratio of 80:20 was 6.7 times greater than that of pure PBT, and the mechanical properties agreed well with the SEM observation.

Toughening of poly(lactic acid) with the renewable bioplastic poly(trimethylene malonate)

ABSTRACTThe aim of this work was to enhance poly(lactic acid)'s (PLA) flexibility and ductility by blending it with another bioplastic. Poly(trimethylene malonate) (PTM), developed as part of this study, was synthesized from 1,3‐propane diol and malonic acid via melt polycondensation. Blend films of PLA and PTM were prepared by solvent casting from chloroform. Differential scanning calorimetry and thermogravimetric analysis were used to show shifted phase transitions and a single glass‐transition temperature, indicating miscibility of PTM in the blend films. Morphology and mechanical characterizations of the PLA/PTM blend films were performed by atomic force microscopy using a quantitative nanomechanical property mapping mode, tensile testing, and scanning electron microscopy. Miscible blends exhibited Young's modulus and elongation at break values that can significantly extend the usefulness of PLA in commercial applications. The blending of PTM with PLA resulted in films with a 27‐fold increase in toughness compared with neat PLA film. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40888.