Morphology,biodegradability, mechanical,and thermal properties of nanocomposite films based on PLA and plasticized PLA

In this study, melt intercalation method is applied to prepare poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG)‐plasticized PLA nanocomposite films including 0, 3, and 5% organoclay (Cloisite 30B) using a laboratory scale compounder, which is connected to a microcast film device. To evaluate the nanomorphology and the dispersion state of the clays, X‐ray diffraction (XRD) and transmission electron microscopy (TEM) are conducted. Tensile tests are performed to characterize the mechanical behavior of the films. Biodegradation rate is determined by degradation tests in composting medium. Differential scanning calorimeter (DSC) is applied to observe the thermal behavior of the films. XRD and TEM show that the exfoliation predominantly occurrs in plasticized PLA nanocomposites, whereas unexfoliated agglomerates together with exfoliated clays are observed in the nonplasticized PLA. Tensile tests indicate that the addition of 3% clay to the neat‐PLA does not affect the strength; however, it enhances the modulus of the nanocomposites in comparison to neat‐PLA. Incorporation of 3% clay to the plasticized PLA improves the modulus with respect to PLA/PEG; on the other hand, the strain at break value is lowered ～ 40%. The increase in the rate of biodegradation in composting medium is found as in the order of PLA > PLA/PEG > 3% Clay/PLA/PEG > 5% Clay/PLA/PEG > 3% Clay/PLA. DSC analysis shows that the addition of 3% clay to the neat PLA results in an increase in T_g. The addition of 20% PEG as a plasticizer to the neat‐PLA decreases T_g about 30°C, however incorporation of clays increases T_g by 4°C for the plasticized PLA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of halloysite nanotubes on the performance of plasticized poly(lactic acid)‐based composites

The objective of this study is processing and characterization of Halloysite nanotube (HNT)/poly(lactic acid) (PLA) nanocomposites. As HNT filler, a domestic source was used (ESAN HNT). The results obtained from this HNT were compared with a well‐known reference HNT (Nanoclay HNT). To achieve the desired physical properties and clay dispersion, composites were compounded via direct melt mixing in a laboratory twin‐screw compounder. However, the constituents were observed to be incompatible without a compatibilizer. To improve the flexibility of nanocomposites and provide compatibilization between PLA and HNT, two types of blends were prepared: PLA plasticized with poly(ethylene glycol) (PEG) denoted as P‐PLA and PLA toughened with a thermoplastic polyurethane (TPU) denoted as T‐PLA. Despite the limited improvement in the P‐PLA blends, TPU addition improved the flexibility of PLA/HNT without deteriorating the tensile strength in a great manner. This was attributed to the relatively better compatibilization effect of TPU and the role of nanotubes acting as bridges between the TPU and PLA phases. POLYM. COMPOS., 37:3134–3148, 2016. © 2015 Society of Plastics Engineers     

Effects of a diisocyanate compatibilizer on the properties of citric acid modified thermoplastic starch/poly(lactic acid) blends

In this article, for the first time in the literature effects of phenylene diisocyanate (PDI)‐based compatibilizer on the physical and chemical properties of citric acid (CA) modified thermoplastic starch (TPS)/poly(lactic acid) (PLA) blends were investigated with respect to PDI and CA content and blend composition. The blends were prepared by melt compounding in a laboratory microcompounder. Fourier transformation infrared spectroscopy results showed that CA interacted with starch and PDI interacted by both starch and PLA through the hydroxyl groups. It was revealed from SEM micrographs that combinatorial usage of CA and PDI resulted in an improved, finer distribution of TPS in PLA matrix. This improvement affected the mechanical properties of blend, especially the toughness related properties such as impact strength and elongation at break. The thermal properties such as T_g and T_m revealed from differential scanning calorimeter analysis were in line with the morphological structure of the blends by suggesting the compatibilization phenomena in the presence of PDI and CA together. Thermogravimetric analysis showed that compatibilization of two phases improved the thermal stability of the blends. As a general conclusion, the combinatorial usage of PDI and CA can be utilized to obtain tougher PLA/TPS blends‐based materials to overcome the brittleness problem. POLYM. ENG. SCI., 53:2183–2193, 2013. © 2013 Society of Plastics Engineers     

Effects of olefin‐based compatibilizers on the morphology,thermal and mechanical properties of ABS/polyamide‐6 blends

In this study, commercially available epoxidized and maleated olefinic copolymers, EMA‐GMA (ethylene‐methyl acrylate‐glycidyl methacrylate) and EnBACO‐MAH (ethylene‐n butyl acrylate‐carbon monoxide‐maleic anhydride), were used at 0, 5, and 10% by weight to compatibilize the blend composed of ABS (acrylonitrile‐butadiene‐styrene) terpolymer and PA6 (polyamide 6). Compatibilizing performance of these two olefinic polymers was investigated from blend morphologies, thermal and mechanical properties as a function of blend composition, and compatibilizer loading level. Scanning electron microscopy (SEM) studies showed that incorporation of compatibilizer resulted in a fine morphology with reduced dispersed particle diameter at the presence of 5% compatibilizer. The crystallization behavior of PA6 phase in the blends was explored for selected blend compositions by differential scanning calorimetry (DSC). At high compatibilizer level a decrease in the degree of crystallization was observed. In 10% compatibilizer containing blends, formation of γ‐crystals was observed contrary to other compatibilizer compositions. The behavior of the compatibilized blend system in tensile testing showed the negative effect of using excess compatibilizer. Different trends in yield strengths and strain at break values were observed depending on compatibilizer type, loading level, and blend composition. With 5% EnBACO‐MAH, the blend toughness was observed to be the highest at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 926–935, 2007     

Reactive compatibilization of PLA/PBS bio-blends via a new generation of hybrid nanoparticles

Poly(butylene succinate) (PBS) is a worthy biodegradable thermoplastic polyester for blending along with other biopolymers, especially with poly (lactic acid) (PLA), to overcome its inadequacies in mechanical and thermal characteristics. Since binary blends of PLA and PBS showed that they are incompatible, compatibilization is required. In this work, multi-epoxide polyhedral oligomeric silsesquioxane (Glycidyl POSS) was added to PLA and PBS using the melt blending method to make them compatible. The blends were prepared at different weight ratios having different amounts of compatibilizer. SEM analysis showed that the Glycidyl POSS impacted the interfacial adhesion and other properties of PLA and PBS blends. Noticeable improvements in mechanical properties were revealed by tensile and impact test results. Tensile strength and Young's modulus were improved when epoxy-POSS was added up to 1 and 3 wt% into ternary blends, but further increasing POSS concentrations resulted in lower values. FTIR analysis showed a strong interaction between the epoxide group of POSS and the end groups of PBS or PLA. The thermal properties of samples were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The shifts in glass transition temperatures of the PLA phase towards lower values appeared in DSC, confirming the enhanced compatibility of PLA and PBS. Also, the reinforcing ability of the POSS inorganic core structure impacted the thermal stability of the blends.     

The influence of POSS type on the properties of PLA

In this study, the effects of reactive and non‐reactive poly(hedral oligomeric silsesquoxane) (POSS) type and their loading level on the mechanical, morphological and thermal properties of PLA composites were investigated for the first time in the literature. A decrease in the melt viscosity of PLA was obtained from the vertical force measurements in the presence of POSS particles except for high O‐POSS loading level. This played an important role for power consumption during micro‐compounding process. The mechanical test results showed that, the elastic‐modulus and yield strength of the PLA/POSS composites were lower than pure PLA in most cases. Moreover, a significant improvement in Izod impact strength of PLA composites was achieved by incorporation of POSS particles into PLA regardless of POSS type. Morphological analysis showed that POSS particles dispersed homogeneously in polymer matrix for all compositions. The glass transition temperature of PLA decreased with the addition of POSS particles. POSS particles also enhanced the decomposition temperature of PLA. POLYM. COMPOS., 37:1497–1506, 2016. © 2014 Society of Plastics Engineers     

Properties of talc/wollastonite/polyamide 6 hybrid composites

In this study, it was aimed to investigate the mechanical, thermal, and morphological properties of PA6 hybrid composites containing talc and wollastonite. Talc and wollastonite filled single and hybrid composites were prepared with melt compounding in a twin screw extruder. The filler content was 40% by weight and the wollastonite/talc ratio was 40/0, 30/10, 20/20, 10/30, and 40/0. The melt flow rate measurements showed that incorporation of fillers into the polyamide 6 (PA6) resulted in an increment in melt viscosity of composites. The presence of a homogeneous dispersion of fillers in the matrix was obtained from morphological analysis. It was revealed from the mechanical tests that in most cases, mechanical properties of 20/20 hybrid composites were significantly higher than that of the single and the other hybrid composites. Heat deflection temperature of the composite was markedly improved by the addition of fillers. Differential scanning calorimeter analysis showed that talc and wollastonite acted as a nucleating agent for PA6. POLYM. COMPOS., 36:739–746, 2015. © 2014 Society of Plastics Engineers     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Reactive compatibilization of PLA/TPU blends with a diisocyanate

This study focuses on the compatibilization of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends by using 1,4 phenylene diisocyanate (PDI) for the first time, as the compatibilizer. Because of the potential interactions of diisocyanates with ? OH/? COOH, they are useful for reactive processing of PLA/TPU blends in the melt processing. To have insight on the reactively compatibilized structure of PLA/TPU blends, phase morphologies are observed by means of scanning electron microscopy. The mechanical, thermal, and rheological responses of the blends are investigated. The observations are that the brittle behavior of PLA changes to ductile with the addition of TPUs. The addition of PDI improves the tensile properties of the blends. The compatibilization action of PDI is monitored with DMA and rheological experiments. Cross‐over in the G′ and G″ curves of compatibilized blends indicates the relaxation of branches formed in the presence of PDI. The dispersed phase size of TPU decreases in PLA in the presence of PDI due to the improved compatibility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40251.