丙烯酸酯接枝改性天然橡胶增韧聚乳酸

通过在天然橡胶(NR)分子链上接枝甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA),制备了三种丙烯酸酯接枝改性NR:NR-g-PMMA,NR-g-PBA和NR-g-(PMMA,PBA)。采用核磁共振氢谱对三种接枝物进行了化学结构鉴定。将接枝改性后的NR和未改性的NR与PLA采用哈克密炼机熔融共混,分别制备了PLA/NR,PLA/NR-gPMMA,PLA/NR-g-PBA和PLA/NR-g-(PMMA,PBA)共混物,研究了接枝改性NR和未改性NR含量对共混物力学性能和热性能的影响。各共混物的拉伸弹性模量和拉伸强度均随接枝改性NR和未改性NR含量的增加而降低,断裂伸长率和缺口冲击强度随接枝改性NR和未改性NR含量的增加而提高。其中,PLA/NR-g-PBA共混物的断裂伸长率和缺口冲击强度比其它共混物提高的幅度大,当NR-g-PBA的质量分数为5%时,PLA/NR-g-PBA共混物的断裂伸长率达到78%,缺口冲击强度为5.2 k J/m2,而纯PLA的断裂伸长率仅为7.7%,缺口冲击强度为2.5 k J/m2,说明NR接枝分子柔顺性较高的BA更有利于促进其与PLA共混物的韧性提高。热分析结果表明,PLA/NR-gPBA共混物的热稳定性相比于纯PLA也有所提高。     

Toughness enhancement of poly(lactic acid) by melt blending with natural rubber

Rubber toughened poly(lactic acid) (PLA) was prepared by blending with natural rubber (NR)‐based polymers. The blends contained 10 wt % of rubber and melt blended with a twin screw extruder. Enhancement of impact strength of PLA was primarily concernced. This study was focused on the effect of rubber polarity, rubber viscosity and molecular weight on mechanical properties of the blends. Three types of rubbers were used: NR, epoxidized natural rubber (ENR25 and ENR50), and natural rubber grafted with poly(methyl methacrylate) (NR‐g‐PMMA). Effect of viscosity and molecular weight of NR, rubber mastication with a two‐roll mill was investigated. It was found that all blends showed higher impact strength than PLA and NR became the best toughening agent. Viscosity and molecular weight of NR decreased with increasing number of mastication. Impact strength of PLA/NR blends increased after applying NR mastication due to appropriate particle size. DMTA and DSC characterization were determined as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Blends of polylactic acid with thermoplastic copolyester elastomer: Effect of functionalized terpolymer type on reactive toughening

This study is an attempt to explore the effectiveness of thermoplastic copolyester elastomer (TPCE) as a toughening agent for improving the impact strength of PLA. Biobased Hytrel^® thermoplastic copolyester of polyether glycol and polybutylene terephthalate was selected as the TPCE of choice for this study. Blends of PLA/Hytrel at varying weight ratios were prepared using extrusion followed by injection molding technique. Optimal synergies of two polymers were found in the PLA/Hytrel (70/30) blend, showing impact strength of 234 J/m, a sixfold increase compared to neat PLA. In order to obtain further enhancement in toughness, different functionalized terpolymers were added to accomplish reactive compatibilization. A series of functionalized terpolymers, ethylene methyle acrylate‐glycidyl methacrylate (EMA‐GMA), ethylene butyl acrylate‐glycidyl methacrylate (EBA‐GMA), ethylene methyl acrylate‐maleic anhydride (EMA‐MaH), and ethylene butyl acrylate‐maleic anhydride (EBA‐MaH) were selected. Comparing PLA ternary blends with different terpolymers, GMA containing terpolymers showed better impact toughness compared to MaH terpolymer blends. Unique fracture surface morphology showing debonding cavitation and massive shear yielding in the ternary blends containing EMA‐GMA resulted in super toughened blends. Highest zero shear viscosity and storage modulus was also observed for ternary blends with EMA‐GMA. Under the processing conditions and blend ratio investigated, EMA‐GMA showed better efficiency in improving the toughness of the PLA blends. POLYM. ENG. SCI., 58:280–290, 2018. © 2017 Society of Plastics Engineers     

Mechanical properties,water swelling behavior,and morphology of swellable rubber compatibilized by PVA‐g‐PBA

A novel water swellable rubber (WSR) was prepared by blending chlorohydrin rubber (CHR) with crosslinked polyacrylate (CPA), poly(vinyl alcohol)‐g‐poly(butyl acrylate) (PVA‐g‐PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG). The amphiphilic graft copolymer PVA‐g‐PBA was incorporated as the compatibilizer between CHR and CPA. Water swellable‐rubber with different grafting percentages and contents of PVA‐g‐PBA was investigated by SEM, mechanical measurement, and water‐swelling tests. The results prove that PVA‐g‐PBA increased interfacial cohesion between CHR and CPA before and after water swelling, decreased percentage loss by weight, and improved water‐swelling behavior. Mechanical properties of WSR were significantly improved by PVA‐g‐PBA, especially for the blends of 5 phr PVA‐g‐PBA with G% = 151.7% before water swelling and that with G% = 340.4% after water swelling.     

Study on a water‐swellable rubber compatibilized by amphiphilic block polymer based on poly(ethylene oxide) and poly(butyl acrylate)

A water‐swellable rubber (WSR), compatibilized by the amphiphilic block copolymer, has been prepared by blending a natural rubber (NR) matrix with crosslinked sodium polyacrylate (CSP), poly(ethylene oxide)‐b‐poly(butyl acrylate) (PEO‐b‐PBA), poly(ethylene glycol) (PEG), reinforced filler, and vulcanizing agents. The preparation process was described. The microphase structure of WSR was characterized by a scanning electron microscopy (SEM) photograph. The dependence of the degree of the water‐absorbing and the water‐swelling, the water‐absorbing and water‐swelling rates on CSP, PEG, and PEO‐b‐PBA contents were investigated. The compatibilizing mechanism of PEO‐b‐PBA on WSR was studied. And the optimum composition range was identified: CSP (30–60 phr), PEG (10–20 phr) PEO‐b‐PBA (PEO/PBA = 0.36, 5 phr). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3120–3125, 2002     

Toughness improvement of poly(lactic acid) with poly(vinyl propionate)-grafted natural rubber

Natural rubber (NR) grafted with poly(vinyl propionate) (NR-g-PVP) was prepared by emulsion polymerization. The monomer content was set at 5, 10, 20, and 30 wt%. The chemical structure of NR-g-PVP was confirmed by ¹H-NMR and FTIR techniques. The grafting parameters of purified NR-g-PVP were evaluated. Binary (PLA/NR and PLA/NR-g-PVP) and ternary (PLA/NR/NR-g-PVP) blends were prepared by melt blending using a twin-screw extruder. The percentage of grafted PVP on NR affected morphology, thermal and mechanical properties of the blends. In binary blends, 5% grafting showed the greatest improvement of toughness and ductility with PLA, whereas there was no improvement in the mechanical properties of PLA/NR blend from using NR-g-PVP as a compatibilizer. The mechanical properties of the blends are related to mutual compatibility of the components. Good interfacial adhesion and proper particle size of NR were the key factors contributing to mechanical properties.     

Bio‐based diblock copolymers prepared from poly(lactic acid) and natural rubber

New bio‐based diblock copolymers were synthesized from poly(lactic acid) (PLA) and natural rubber (NR). NR polymer chains were modified to obtain hydroxyl telechelic natural rubber oligomers (HTNR). Condensation polymerization between PLA and HTNR was performed at 110°C during 24 or 48 h. The molecular weight of PLA and HTNR and the molar ratio PLA : HTNR were varied. The new ester linkage in the diblock copolymers was determined by ¹H‐NMR. The molecular weight of the diblock copolymers determined from SEC agreed with that expected from calculation. The thermal behavior and degradation temperature were determined by DSC and TGA, respectively. The diblock copolymers were used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. PLA blended with the diblock copolymer showed higher impact strength, which was comparable to the one of a PLA/NR blend. The former blend showed smaller dispersed particles as showed by SEM images, indicating the increase in miscibility in the blend due to the PLA block. The compatibilization was effective in the blends containing ～10 wt % of rubber. At a higher rubber content (>10 wt %), coalescence of the NR and diblock copolymer was responsible of the larger rubber diameter in the blends, which causes a decrease of the impact strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41426.     

Effect of glycidyl methacrylate-grafted natural rubber on physical properties of polylactic acid and natural rubber blends

Natural rubber (NR) was melt blended with polylactic acid (PLA) at various ratios using an internal mixer. The impact strength and elongation at break of PLA/NR blend dramatically increased with increasing NR content up to 10% (w/w). Glycidyl methacrylate-grafted natural rubber (NR-g-GMA) was used as a compatibilizer for PLA/NR blend. The effects of content and %grafting of NR-g-GMA on mechanical properties of PLA/NR blend were studied. The experimental result showed that the addition of NR-g-GMA in PLA/NR blend significantly improved impact strength and elongation at break of PLA/NR blend when compared with that of neat PLA and PLA/NR blend without NR-g-GMA. The impact strength and elongation at break of PLA/NR blend increased with increasing NR-g-GMA content up to 1% (w/w). Moreover, with increasing % grafting of NR-g-GMA in PLA/NR blend up to 4.35, the impact strength and elongation at break of the blend increased. Morphological and thermal property of PLA, PLA/NR, and PLA/NR/NR-g-GMA were elucidated as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Irradiation‐induced surface graft polymerization onto calcium carbonate nanoparticles and its toughening effects on polypropylene composites

Nano‐sized calcium carbonate was pretreated with silane coupling agent and then mixed with butyl acrylate that is of larger amount than the nanoparticles. Under γ‐irradiation, graft polymerization occurred on the nanoparticle surface, forming a nanocomposite structure consisting of grafted poly(butyl acrylate) (PBA), homopolymerized PBA, and the segregated nanoparticles. It was found that the silane pretreatment significantly promoted the graft reaction. When the grafted nano‐CaCO₃ particles were melt compounded with polypropylene (PP), an obvious synergistic effect, offered by (i) the chemical bonding between the elastomer type grafted PBA and nano‐CaCO₃ and (ii) the deliberately introduced thick interlayer mainly constructed by the homopolymerized PBA, led to a significant increase in notch impact strengths and elongation to break of PP at a rather low content of nano‐CaCO₃. Meanwhile, the tensile stiffness of the composites was also slightly increased and the yielding strength of the composites was almost unchanged. The results are different from those with conventional rubber‐toughened plastics, in which the improvement of ductility is acquired at high additive fraction and a great expense of strength performance. POLYM. ENG. SCI., 45:529–538, 2005. © 2005 Society of Plastics Engineers     

Use of natural rubber‐g‐polystyrene as a compatibilizer in casting natural rubber/polystyrene blend films

Natural rubber/polystyrene (NR/PS) blend films with weight ratios of 70/30, 60/40, and 50/50 were prepared using polystyrene grafted natural rubber copolymers (NR‐g‐PS) as the compatibilizer. Copolymers with molar ratios of 90/10, 80/20, and 70/30 were synthesized via emulsion copolymerization using tert‐butyl hydroperoxide/tetraethylene pentamine as an initiator. The copolymers were subsequently added into the blends at 0, 5, 10, 15, 20, 25, and 30 phr. The mixtures were cast into films by the solution‐casting method using toluene as the casting solvent. Mechanical and morphological properties of the prepared films were investigated. The film prepared from 80/20 NR‐g‐PS showed higher tensile and tear strength, as well as finer domain size of the dispersed phase, than those prepared from 90/10 and 70/30 NR‐g‐PS. However, the mechanical properties of the films were decreased at high loading of the copolymers. In addition, themogravimetric analysis revealed that weight loss was decreased upon introduction of the compatibilizer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 826–831, 2005     

Synthesis of poly(butyl acrylate)—laponite nanocomposite nanoparticles for improving the impact strength of poly(lactic acid)

This work aims at preparing and characterizing poly(butyl acrylate) (PBA)—laponite (LRD) nanocomposite nanoparticles and nanocomposite core (PBA‐LRD)‐shell poly(methyl methacrylate) (PMMA) nanoparticles, on the one hand, and the morphology and properties of poly(lactic acid) (PLA)‐based blends containing PBA‐LRD nanocomposite nanoparticles or (PBA‐LRD)/PMMA core–shell nanoparticles as the dispersed phase, on the other hand. The PBA and (PBA‐LRD)/PMMA nanoparticles were synthesized by miniemulsion or emulsion polymerization using LRD platelets modified by 3‐methacryloxypropyltrimethoxysilane (MPTMS). The grafting of MPTMS onto the LRD surfaces was characterized qualitatively using FTIR and quantitatively using thermogravimetric analysis (TGA). The amounts of LRD in the PBA‐LRD nanocomposites were characterized by TGA. The PBA/PMMA core–shell particles were analyzed by ¹H‐NMR. Their morphology was confirmed by SEM and TEM. Mechanical properties of (PBA‐LRD)/PLA blends and (PBA‐LRD)/PMMA/PLA ones were tested and compared with those of the pure PLA, showing that core–shell particles allowed increasing impact strength of the PLA while minimizing loss in Young modulus and tensile strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Bulk and emulsion copolymerizations of n-butyl acrylate and poly(methyl methacrylate) macromonomer

Bulk and emulsion copolymerizations of an ω-unsaturated poly(methyl methacrylate) (PMMA) macromonomer with n-butyl acrylate (n-BA) were investigated. The reactivity of PMMA macromonomer in bulk copolymerization with n-BA was found to be lower than that of methyl methacrylate monomer with n-BA. The incorporation of PMMA macromonomer into poly(butyl acrylate) (PBA) latex particles by miniemulsion copolymerization was proved by high performance liquid chromatography-silica adsorption spectroscopy. Dynamic mechanical studies showed that PMMA macromonomer was grafted to the PBA backbone, and the degree of grafting increased as the ratio of PMMA macromonomer to n-BA increased. Microphase separation of the PMMA macromonomer grafts was observed at higher ratio of macromonomer (higher or equal to 10% weight of macromonomer based on total polymer phase). The n-BA/PMMA macromonomer copolymer behaved completely differently from the physical blend of PBA and PMMA macromonomer particles of the same composition. © 1996 John Wiley & Sons, Inc.     

High‐performance bio‐based poly(lactic acid)/natural rubber/epoxidized natural rubber blends: effect of epoxidized natural rubber on microstructure,toughness and static and dynamic mechanical properties

Attempts have been made to prepare high‐performance bio‐based blends through blending of poly(lactic acid) (PLA) with natural rubber (NR) in the presence of epoxidized natural rubber (ENR) as a compatibilizer. The prepared samples were characterized using differential scanning calorimetry, measuring the tensile properties and impact resistance, scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMTA). Morphological studies revealed a matrix‐dispersed morphology for all blends, in which the average droplet size significantly decreased with the use of ENR. The elongation at break and impact strength of the blend containing 3 wt% ENR were 45 and 16 times those of neat PLA, respectively. These values are significantly higher than those previously reported for various simple and dynamically vulcanized rubber‐toughened PLAs. The influence of ENR on compatibility was confirmed by rheological tests, FTIR spectra and DMTA. DMTA also showed a marked increase in elastic modulus for the blend in the presence of 3 wt% ENR. The tensile properties and impact resistance were directly dependent on the ENR content and rubber droplet size. © 2018 Society of Chemical Industry     

Synthesis and characterization of poly(butyl acrylate)/silica and poly(butyl acrylate)/silica/poly(methyl methacrylate) composite particles

Poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) core–shell particles embedded with nanometer‐sized silica particles were prepared by emulsion polymerization of butyl acrylate (BA) in the presence of silica particles preabsorbed with 2,2′‐azobis(2‐amidinopropane)dihydrochloride (AIBA) initiator and subsequent MMA emulsion polymerization in the presence of PBA/silica composite particles. The morphologies of the resulting PBA/silica and PBA/silica/PMMA composite particles were characterized, which showed that AIBA could be absorbed effectively onto silica particles when the pH of the dispersion medium was greater than the isoelectric potential point of silica. The critical amount of AIBA added to have stable dispersion of silica particles increased as the pH of the dispersion medium increased. PBA/silica composite particles prepared by in situ emulsion polymerization using silica preabsorbed with AIBA showed higher silica absorption efficiency than did the PBA/silica composite particles prepared by direct mixing of PBA latex and silica dispersion or by emulsion polymerization in which AIBA was added after the mixing of BA and silica. The PBA/silica composite particles exhibited a raspberrylike morphology, with silica particles “adhered” to the surfaces of the PBA particles, whereas the PBA/silica/PMMA composite latex particles exhibited a sandwich morphology, with silica particles mainly at the interface between the PBA core and the PMMA shell. Subsequently, the PBA/silica/PMMA composite latex obtained had a narrow particle size distribution and good dispersion stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3425–3432, 2006     

粒径可控的聚丙烯酸丁酯/聚甲基丙烯酸甲酯核壳乳液的制备及表征

采用种子乳液聚合法制备了聚丙烯酸丁酯(PBA)乳液,然后通过第二单体甲基丙烯酸甲酯的预溶胀法聚合制备了PBA/聚甲基丙烯酸甲酯(PMMA)乳液,用激光散射粒度仪和透射电子显微镜对乳液粒径和结构进行了表征.结果表明,当乳化剂十二烷基硫酸钠质量分数为丙烯酸丁酯的1.5%时,可制备粒径为53.6 nm且分布窄的PBA种子乳液;通过调整补加乳化剂、单体与种子乳液的用量,可制得粒径为53.6～443.8 nm的一系列单分散PBA乳液;PBA/PMMA乳液具有完善的核壳结构,且在核壳两相间存在着一个过渡层.     

Chlorohydrin water‐swellable rubber compatibilized by an amphiphilic graft copolymer. III. Effects of PEG and PSA on water‐swelling behavior

Chlorohydrin water‐swellable rubber—composed of chlorohydrin rubber (CHR), crosslinked polyacrylate (CPA), the amphiphilic compatibilizer poly(vinyl alcohol)‐g‐poly(butyl acrylate) (PVA‐g‐PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG)—was prepared. The dispersion of PEG in the blend was characterized by wide‐angle X‐ray diffraction (WAXD). The dependence of the water absorbing ratio by weight, the water‐swelling ratio by volume, and the percentage loss by weight on PEG and PSA contents were investigated. The effects of PEG and PSA on the second water‐swelling behaviors and long‐term water‐retention behaviors were also studied. Optimums for the water‐absorbing and water‐swelling abilities within the range of the experiment were obtained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2509–2516, 2001     

Improved mechanical properties of NR/EPDM blends by controlling the migration of curative and filler via reactive processing technique

Simple blending of natural rubber/ethylene–propylene–diene rubber (NR/EPDM) generally results in inferior mechanical properties because of curative migration and their differences for filler affinity. In this work, the 70/30 and 50/50 NR/EPDM blends prepared by reactive processing techniques were investigated and compared with the simple, nonreactive blends. The reactive blend compounds were prepared by preheating EPDM, containing all curatives to a predetermined time related to their scorch time prior to blending with NR. For the 70/30 gum blends, four types of accelerators were studied: 2,2‐mercaptobenzothiazole (MBT), 2,2‐dithiobis‐ (benzothiazole) (MBTS), N‐cyclohexyl‐2‐benzothiazolesulfenamide (CBS), and N‐tert‐butyl‐2‐benzothiazolesulfenamide (TBBS). When compared with the simple blends, the reactive blends cured with CBS and MBTS showed a clearly improved tensile strength whereas the increase of tensile strength in the blends cured with TBBS and MBT was marginal. However, a dramatic improvement of ultimate tensile properties in the reactive 50/50 NR/EPDM blends cured with TBBS was observed when compared with the simple blend. For the N‐550‐filled blends at the blend ratios of 70/30 and 50/50, the reactive‐filled blends prepared under the optimized preheating times demonstrated superior tensile strength and elongation at break over the simple blends. The improved crosslink and/or filler distribution between the two rubber phases in the reactive blends accounts for such improvement in their mechanical properties. This is shown in the scanning electron micrographs of the tensile fractured surfaces of the reactive blends, which indicate a more homogeneous blend. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of rubber content on mechanical,thermal, and morphological behavior of natural rubber toughened poly(lactic acid)–multiwalled carbon nanotube nanocomposites

The effects of natural rubber (NR) on the mechanical, thermal, and morphological properties of multiwalled carbon nanotube (CNT) reinforced poly(lactic acid) (PLA) nanocomposites prepared by melt blending were investigated. A PLA/NR blend and PLA/CNT nanocomposites were also produced for comparison. The tensile strength and Young's modulus of PLA/CNT nanocomposites improved significantly, whereas the impact strength decreased compared to neat PLA. The incorporation of NR into PLA/CNT significantly improved the impact strength and elongation at break of the nanocomposites, which showed approximately 200% and 850% increases at 20 wt % NR, respectively. However, the tensile strength and Young's modulus of PLA/NR/CNT nanocomposites decreased compared to PLA/CNT nanocomposites. The morphology analysis showed the homogeneous dispersion of NR particles in PLA/NR/CNT nanocomposites, while CNTs preferentially reside in the NR phase rather than the PLA matrix. In addition, the incorporation of NR into PLA/CNT lowered the thermal stability and glass‐transition temperature of the nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44344.     

Study of Drug Transport Phenomenon of Acrylic IPNs Embedded with Iron Oxide Nanoparticles

Interpenetrating polymer networks (IPNs) are formed involving hydrophobic poly(butyl acrylate) (PBA) and hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) in presence of superparamagnetic ferric oxide nanoparticles (<30 nm) through free radical polymerization. Ferric oxide (Fe₃O₄) particles are synthesized using thermal arc plasma technique. IPNs are prepared by taking the two acrylates, PBA/PHEA in blend ratios of 60:40, 50:50, and 40:60 (w/w). The samples are characterized in terms of swelling, FTIR, DSC, TGA, and SEM. Bactericidal effect on IPNs is checked by cell growth study of E. coli. Drug diffusion phenomenon of multi drug-loaded samples is compared with respect to the PBA/PHEA blend ratio (w/w).