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.     

Effects of thermoplastic poly(ether-ester) elastomer and bentonite nanoclay on properties of poly(lactic acid)

This work presented the influence of thermoplastic poly(ether-ester) elastomer (TPEE) and bentonite (BTN) on improving the mechanical and thermal properties of poly(lactic acid) (PLA). PLA was initially melt mixed with TPEE at six different loadings (5–30 wt%) on a twin screw extruder and then injection molded. The mechanical tests revealed an increasing impact strength and elongation at break with increasing TPEE loading, but a diminishing Young's modulus and tensile strength with respect to pure PLA. The blend at 30 wt% TPEE provided the optimum improvement in toughness, exhibiting an increase in the impact strength and elongation at break by 3.21- and 10.62-fold over those of the pure PLA, respectively. Scanning electron microscopy analysis illustrated a ductile fractured surface of the blends with the small dispersed TPEE domains in PLA matrix, indicating their immiscibility. The 70/30 (wt/wt) PLA/TPEE blend was subsequently filled with three loadings of BTN (1, 3, and 5 parts by weight per hundred of blend resin [phr]), where the impact strength, Young's modulus, tensile strength and thermal stability of all the blends were improved, while the elongation at break was deteriorated. Among the three nanocomposites, that with 1 phr BTN formed exfoliated structure and so exhibited the highest impact strength, elongation at break, and tensile strength compared to the other intercalated nanocomposites. Moreover, the addition of BTN was found to increase the thermal stability of the neat PLA/TPEE blend due to the barrier properties and high thermal stability of BTN.     

Toughening of polylactide via in situ formation of polyurethane crosslinked elastomer during reactive blending

Polylactide (PLA)/polyurethane (PU) composites were prepared by reactive blending method with in situ formation of PU particles via the reaction between polyester polyol (PPG) and toluene‐2,4‐diisocyanate (TDI). The interfacial compatibility and adhesion between the PLA and PU phases were greatly improved by the reaction of the terminal hydroxyl groups of PLA and N?C?O groups of TDI forming graft copolymer, as confirmed by FTIR spectroscopy. The elongation at break and notch impact strength of PLA/PU composites increased considerably with increasing PU content, and the tensile strength of PLA/PU composites decreased slightly compared with that of pure PLA. Upon addition of 12 wt % PU, the elongation at break and notch impact strength increased to 175.17% and 10.96 kJ/m², respectively, about 27 times and 5.4 times greater than the corresponding values for the pure PLA. The tensile strength decreased only slightly to 48.65 MPa. The excellent interfacial adhesion, the dispersed PU elastomeric particles acting as stress concentration areas, and the triggering of large matrix shear yield as well as many fibrils by internal cavitation were the main mechanical toughening mechanisms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44383.     

Impact Modification of Polylactide with a Biodegradable Ethylene/Acrylate Copolymer

The effectiveness and efficiency of an ethylene/acrylate copolymer in toughening semicrystalline and amorphous PLA through melt blending is studied. The mechanical properties, phase morphologies, miscibilities, and toughening mechanisms of the blends are assessed. The ethylene/acrylate impact modifier effectively improved the impact strength of the blends, regardless of the PLA type. The semicrystalline blends showed decreased tensile strength and modulus with increased impact modifier content. In contrast, the ductility, elongation at break, and energy to break increased significantly. The relatively low BDT temperature obtained for the PLA blends renders the ethylene/acrylate copolymer impact modifier a desirable additive to toughen PLA for use in cold temperatures.

     

PLA/PPC/OMMT纳米复合材料的结构与性能研究

采用双螺杆挤出机制备了聚乳酸（PLA）/聚碳酸亚丙酯（PPC）共混物和PLA/PPC/有机改性蒙脱土（OMMT）纳米复合材料,采用偏光显微镜、差示扫描量热仪和力学性能试验机等对共混物和纳米复合材料的相态结构、熔融与结晶行为和力学性能等进行了研究。结果表明,在PPC含量低于30 %时,随着PPC含量的增加,PLA/PPC和PLA/PPC/OMMT体系中PLA的玻璃化转变温度（Tg）均降低,在PPC含量为50 %时出现了明显的相分离;随着PPC含量的增加,PLA/PPC的冲击强度增大;OMMT的含量小于1.5 %时,PLA/PPC/OMMT体系的结晶度、拉伸强度、断裂伸长率和冲击强度均随OMMT含量的增加而增大。     

Effect of talc on the properties of polypropylene/ethylene/propylene/diene terpolymer blends

In the present study, the effect of talc content on the mechanical, thermal, and microstructural properties of the isotactic polypropylene (i‐PP) and elastomeric ethylene/propylene/diene terpolymer (EPDM) blends were investigated. In the experimental study, five different talc concentrations, 3, 6, 9, 12, and 15 wt %, were added to i‐PP/EPDM (88/12) blends to produce ternary composites. The mechanical properties such as yield and tensile strengths, elongation at break, elasticity modulus, izod impact strength for notch tip radius of 1 mm, and hardness with and without heat treatments and thermal properties, such as melt flow index (MFI), of the ternary composites have been investigated. The annealing heat treatment was carried out at 100°C for holding time of 75 h. From the tensile test results, an increased trend for the yield and tensile strengths and elasticity modulus was seen for lower talc contents, while elongation at break showed a sharp decrease with the addition of talc. In the case of MFI, talc addition decreased the MFI of i‐PP/EPDM blends. It was concluded that, taking into consideration, mechanical properties and annealing heat treatment, heat treatment has much more effect on higher yield and tensile strengths, elongation at break, elasticity modulus, impact strength, and hardness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3033–3039, 2006     

胺端基型超支化乙二胺三嗪聚合物对PLA/PPC的增韧改性研究

以乙二胺和三聚氯氰作为原料,以丙酮为溶剂,通过“一步法”合成了胺端基型的超支化乙二胺三嗪聚合物(HBETP)。以HBETP作为改性剂,采用双螺杆挤出机熔融共混和注射成型法制备了聚乳酸(PLA)/聚碳酸亚丙酯(PPC)共混物,并用差示扫描量热仪(DSC)、 热失重分析仪(TGA)、电子万能试验机、扫描电字显微镜(SEM)等测试手段对共混物的热性能、力学性能以及断面形貌等进行表征与测试。结果表明,与PLA/PPC共混物相比,当HBETP含量为0.6份时,PLA/PPC/HBETP共混体系在保持拉伸强度基本不变的基础上,断裂伸长率和冲击强度分别提高了266.0 %和122.9 %;HBETP是一种增韧PLA/PPC共混物的有效助剂。     

Preparation and characterization of poly(lactic acid)/recycled polypropylene blends with and without the coupling agent,n-(6-aminohexyl)aminomethyltriethoxysilane

Blends of polylactide (PLA) and recycled polypropylene (rPP) were prepared by melt-processing using a corotating twin-screw extruder and subsequent pelletizing of the extrudates for injection molding. The PLA/rPP blends were characterized by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), rheometer (MCR-102), scanning electron microscopy(SEM), tensile tests, and impact measurements. The results indicate that the PLA/rPP blend is immiscible and has a two-phase structure. TGA revealed enhancement of the thermal stability of the blends upon addition of rPP. The storage modulus, loss modulus, and complex viscosity of the blends increased with rPP concentration. Mechanical studies showed that introduction of rPP results in a decrease in tensile strength and modulus and enhancement of the impact strength of PLA in the blends. The effects of a silane coupling agent on the morphology and on the tensile and impact properties of the rPP blends of silane-modified PLA were also examined. SEM studies suggest that silane is an effective interfacial modifier. Thus, better interfacial adhesion was observed with silane-modified blends as compared with unmodified blends. Silane also improved the mechanical properties of the modified blends. The blends reached maximum tensile strength at 1.5 wt.% silane (relative to modified PLA content), and impact strength increased with increasing silane concentration. These results confirm the enhancing effect of silane on modified PLA/rPP blends.     

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.     

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。     

Poly(lactic acid) blends with desired end-use properties by addition of thermoplastic polyester elastomer and MDI

The disadvantages of the poor mechanical properties of polylactic acid (PLA) limit its ability to be used in a wide number of applications. Melt blending of PLA and thermoplastic polyester elastomer (TPEE) has been performed in an effort to toughen the PLA without significant losses in modulus and ultimate tensile strength. In order to enhance the compatibility of PLA and TPEE, a diisocyanate compound was used as a reactive modifier. The thermal and mechanical properties, miscibility and phase morphologies of the blends were investigated. A blend of PLA and TPEE with a modifier does not lead to an important drop in tensile strength and modulus whereas the elongation at break is characterized by a significant increase (above 300%), compared with that of neat PLA and PLA/TPEE. The blends of PLA/TPEE/Modifier were found by thermal and fractured surface analysis to be an immiscible system with the addition of a modifier. However, the relative ductility of PLA/TPEE/Modifier is 34 times higher than that of neat PLA. The brittle fracture of neat PLA was transformed into a ductile fracture by the addition of a modifier.     

PBAT/PLA薄膜的制备及性能研究

将聚乳酸（PLA）和聚对苯二甲酸-己二酸-丁二醇酯（PBAT）共混制备成共混材料,探讨了不同PLA含量对材料性能的影响。结果表明,PBAT/PLA共混材料中,随着PLA含量的增加,拉伸强度先降低后升高,当PLA含量为90 %时,拉伸强度达到60.12 MPa,而其断裂伸长率从703 %降低至8 %,由韧性材料逐渐转变为脆性材料;PLA含量为30 %时,性能变化出现拐点;PLA含量为50 %时出现明显相分离,且PLA的加入可以加速PBAT材料的结晶,使结晶温度由38 ℃提高至82 ℃;PBAT/PLA共混材料在PLA含量低于70 %时,都可以实现较好的吹膜过程,且薄膜材料的拉伸强度为39.59 MPa,断裂伸长率不低于137 %。     

Mechanical,rheological, and crystallinity properties of polylactic acid/polyethylene glycol-polydimethylsiloxane copolymer blends by melt blending

Polylactic acid (PLA) is high in strength and modulus, but its applications are limited partly due to its inherent brittleness. It is difficult to keep the toughness and transparency of modified PLA without damaging its tensile strength and crystallinity. To improve the properties of PLA, polyethylene glycol-polydimethylsiloxane copolymer (PEG-PDMS) was incorporated to PLA via melt blending. By incorporating only 5 wt% of PEG-PDMS into PLA matrix, the elongation at break of the blends increased from 6% to 58% and the tensile strength was found to be 48.8 MPa. Differential scanning calorimetry demonstrated that the crystallinity of PLA/5%PEG-PDMS blends reached 33.5%. At the same time, the energy storage modulus (G) and complex viscosity (η*) of the blends had been improved. UV–vis test showed the light transmittance of the PLA/5%PEG-PDMS blends was slightly decreased. The toughened materials are sufficient to cope with the challenges brought by complex environments, achieving an efficient toughening effect.     

Morphologies and mechanical properties of polylactide/thermoplastic polyurethane elastomer blends

To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to prepare PLA/TPU blends suitable for a wide range of applications of PLA as general‐purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J‐integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal,mechanical, and rheological properties of polylactide/poly(1,2‐propylene glycol adipate)

Polylactide (PLA) was melt blended with poly(1,2‐propylene glycol adipate) (PPA) in a Thermo‐Haake mixer. Thermal, mechanical, and rheological properties of the blends were investigated by means of differential scanning calorimetry, dynamic mechanical analysis, tensile test, and small amplitude oscillatory shear rheometry. PPA lowered the glass transition temperature and increased the ability of PLA to cold crystallization. With the increase in PPA content (5–25 wt%), the blends showed decreased tensile strength and Young's modulus; however, impact strength and elongation‐at‐break along were dramatically increased due to the plastic deformation. Morphological results of PLA/PPA blends showed that PPA was good compatible with PLA. The plasticization effect of PPA was also manifested by the lowering of dynamic storage modulus and viscosity in the melt state of the blends compared with neat PLA. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Toughening of polylactide with epoxy-functionalized methyl methacrylate–butyl acrylate copolymer

Glycidyl methacrylate-functionalized methyl methacrylate–butyl acrylate (GACR) core–shell structure copolymers were synthesized to toughen polylactide (PLA). With an increase in GACR content, the PLA/GACR blends showed decreased tensile strength and modulus; however, the elongation at break and the impact strength were significantly increased compared with that of PLA. The brittle fracture of neat PLA was gradually transformed into ductile fracture by the addiction of GACR. From dynamic mechanical analysis, the rigidity of the PLA/GACR blends was decreased with the increase of GACR content. The addition of GACR decreased the degree of crystallinity of PLA. The GACR was found to aggregate to form clusters with size increasing with increasing GACR content by transmission electron microscope analysis. The clusters dispersed in PLA matrix uniformly. It was found that PLA demonstrated large area, plastic deformation (shear yielding) and cavities in the blend upon being subjected the tensile and impact tests, which was an important energy-dissipation process and led to a toughened and transparent blend.     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.     

SEBS-g-MAH增韧聚乳酸的性能研究

采用哈克密炼机制备了聚乳酸(PLA)与马来酸酐接枝苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚弹性体(SEBS-g-MAH)的共混物,并对共混物的力学性能、流变性能和微观结构进行了分析。结果表明,共混物的拉伸强度随着SEBS-g-MAH含量的增加而下降,断裂伸长率随着SEBS-g-MAH含量的增加而增大。当SEBS-g-MAH的含量为30 %时,共混物的冲击强度提高了2.5倍,共混物的韧性得到提高。随着SEBS-g-MAH含量的增加,PLA熔体黏度的变化趋势与SEBS-g-MAH越来越相似,即熔体黏度随着频率的增大而下降。扫描电镜分析表明,MAH基团改善了两相间的界面作用,增韧作用明显。     

PVC/ABS共混体系力学性能的研究

用冲击试验机、材料试验机和另外一些相关的仪器对PVC/ABS共混体系的力学性能进行了测试、研究,结果发现,PVC/ABS共混体系的性能是组分的函数。ABS的加入改善了PVC/ABS共混体系的力学性能,随着ABS的增加,体系的冲击强度和断裂伸长率明显地提高,而体系的拉伸强度、拉伸模量几乎是随ABS含量的增加而单调地下降。     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005