Nucleating Agent For PLA Research Articles

The effect of filler loading, biological treatment, and bioplastic blend ratio on flexural and impact properties of blended bioplastic reinforced with spent coffee ground

AbstractIn this study, the mechanical and morphological characteristics of poly(hydroxyalkanoate) (PHA)/poly(lactic acid) (PLA) blend matrix reinforced with spent coffee ground (SCG) were investigated across various weight ratios (100/0, 75/25, 50/50, 25/75, and 0/100) and SCG contents (10–40 wt%). SEM micrographs revealed a phase‐separated structure with cracks on the fracture surface, consistent with the lower flexural properties of biocomposites. The incorporation of SCG reduced mechanical properties, mainly due to its incompatibility with the PHA/PLA matrix. Biocomposites with high SCG content demonstrated lower energy absorption capabilities, likely due to SCG aggregates acting as stress concentrators and disrupting load‐transferring mechanisms. Moreover, increasing PHA content in the blends led to higher PLA crystallinity, as PHA acted as a nucleating agent for PLA. For biological treatment, biocomposites with PHA/PLA ratio (50/50) and SCG loading (20 wt%) were employed. The microscopic analysis highlighted well‐dispersed treated SCG within the matrix and improved interfacial contact. Biocomposites with treated SCG demonstrated remarkable enhancements of 52% and 113% in flexural strength and modulus, respectively. These findings proved the effectiveness of sustainable fungal treatment in enhancing interfacial adhesion and improving the mechanical performance of biocomposites.Highlights Percentage of SCG in bioplastic blend as a significant effect on the flexural properties and impact strength. The ratio of the bioplastic blend has the strong influence on the flexural properties and impact properties. Biological treatment of SCG has improved the interfacial interaction between SCG and bioplastic blend. The treated SCG has rougher surface which facilitates the interfacial locking between bioplastic blend and treated SCG. The biological treatment of SCG has improved the mechanical properties of the composites.

Morphological characteristics and properties of TPS/PLA/cassava pulp biocomposites

The effect of cassava pulp (CP) on morphological, tensile, and thermal properties of a thermoplastic cassava starch (TPS)/poly (lactic acid) (PLA) blend was investigated. TPS/PLA/CP biocomposites were manufactured by melt extrusion and then converted into specimens using an injection molding. The weight fraction of PLA to TPS/CP was fixed at 40:60, whereas the final CP concentration in the composites was varied in the range of 4.4–22.1 wt%. CP could act as a reinforcement for TPS/PLA blend to enhance its tensile strength up to 354% and Young's modulus up to 722% when 22.1 wt% of CP was loaded and a nucleating agent for PLA as confirmed from the reduced Tcc. In addition, TPS/PLA/CP composites showed a discrete phase structure (i.e., droplets in matrix) when CP with lower concentration (i.e., 4.4 wt%, 8.8 wt%, and 13.3 wt%) was incorporated and a bicontinuous phase structure (i.e., co-continuous) when higher concentration of CP (i.e., 17.7 wt% and 22.1 wt%) was employed. The results suggest that TPS/PLA/CP biocomposites have potential to be used in the manufacturing of injection-molded articles, particularly when biodegradability and renewability of the material are required.

Synthesis of Inorganic Silica Grafted Three-arm PLLA and Their Behaviors for PLA Matrix

The low melt strength and poor crystallization behavior severely limit the processing and application of poly(lactic acid) (PLA) as biodegradable film materials. In this work, three-arm poly(L-lactic acid) (3A-PLLA) grafted silica nanoparticles with two kinds of topology structures were introduced into PLA matrix to improve the biodegradation performance. Different methods were used to characterize the structure of the grafted 3A-PLLA chains, the grafting density, and the thermal decomposition behavior of the nanoparticles. By varying the mass ratios of raw materials and altering the order of dropping solution in the reaction, high grafting densitytangled 3A-PLLA grafted SiO2 was synthesized as “3A-PLLA grafting to SiO2” (GTS), while low grafting density-stretched 3A-PLLA grafted SiO2 was obtained as “SiO2 grafting to 3A-PLLA” (GTA). Topology of nanoparticles as well as the filler-matrix interaction is critically important to structure bio-nanocomposites with desirable properties. Thus, the GTS and GTA nanoparticles were introduced into PLA matrix to assess the effect. The SEM images showed the uniform dispersion of the modified nanoparticles, while the shear rheology results revealed that GTA nanoparticles made a more significant contribution on the melt-strengthening and relaxation time-extension of PLA. Moreover, it is suggested that GTA nanoparticles were more effective to act as a nucleating agent for PLA, which was proved by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) researches. All of the improvements mentioned above of GTA nanocomposites can be ascribed to stronger entanglements between 3A-PLLA stretched by nano-SiO2 and PLA matrix.

Preparation and characterization of benzoyl‐hydrazide‐derivatized poly(lactic acid) and γ‐cyclodextrin inclusion complex and its effect on the performance of poly(lactic acid)

A nucleating agent, benzyl‐hydrazide‐derivatized poly(lactic acid) (PLA) and γ‐cyclodextrin inclusion complex (PLA‐IC‐BH), was synthesized through a series of reactions. Poly(lactic acid) and γ‐cyclodextrin inclusion complex (PLA‐IC) was first obtained by ultrasonic co‐precipitation, which was then subjected to carboxylation, acylation, and amidation using benzoyl hydrazine and thionyl chloride. The composition and structure of PLA‐IC‐BH was confirmed by 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. PLA/PLA‐IC‐BH composites were prepared by melt blending and a hot‐press forming process. Mechanical properties, thermal stabilities, and crystallization behaviors of PLA/PLA‐IC‐BH samples were investigated by thermogravimetric analysis, differential scanning calorimetry (DSC), polarized optical microscopy (POM), rheological analysis, and so on. Mechanical testing and thermogravimetric analysis showed that the tensile strengths, impact properties, and thermal stabilities of PLA/PLA‐IC‐BH composites were improved significantly compared to pure PLA and PLA/PLA‐IC. DSC results showed that crystallinity of PLA was increased from 5.17% to 38.93% after introduction of PLA‐IC‐BH. POM results showed that PLA‐IC‐BH acted as a nucleating agent for PLA and enhanced its crystallization rate. Rotational rheological behaviors of PLA/PLA‐IC‐BH demonstrated that incorporation of PLA‐IC‐BH increased the rigidity of the network structure of the PLA matrix. Compared to those of PLA, the maximum torque and apparent viscosity of PLA/PLA‐IC‐BH composites were increased by 55.56% and 25.59%, respectively. Copyright © 2017 John Wiley & Sons, Ltd.

Structure, properties and rheological behavior of thermoplastic poly(lactic acid)/quaternary fulvic acid-intercalated saponite nanocomposites

Sodium humate was oxidized with nitric acid to obtain fulvic acid (FA), which was further quaternized to obtain quaternary fulvic acid (QFA). QFA-intercalated saponite (QFA-saponite) was prepared ultrasonically. Thermoplastic poly(lactic acid) (PLA)/quaternary fulvic acid-intercalated saponite nanocomposites were prepared by melt intercalation technique. The morphology and dispersion of QFA-saponite were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Mechanical properties, thermal stability and crystallization behavior of PLA/QFA-saponite nanocomposites were also tested. Results showed a predominantly flocculated structure and partially intercalated morphology for QFA-saponite. Mechanical testing and thermogravimetric analysis showed that the tensile strength, impact properties, and thermostability of PLA/QFA-saponite nanocomposites improved significantly compared to pure PLA. Differential scanning calorimetry results showed that crystallinity of PLA increased from 22.5 to 68.3 % on addition of QFA-saponite. Polarized optical microscopy showed QFA-saponite as a nucleating agent for PLA that enhanced its crystallization rate. Rotational rheological behaviors of PLA/QFA-saponite nanocomposites demonstrated that incorporation of QFA-saponite increased rigidity of the network structure in PLA matrix.

Thermal, rheological and morphological properties of poly (lactic acid) (PLA) and talc composites

In this study, composites based on poly(lactic acid) (PLA)/talc were prepared at different compositions by melt mixing in a twin screw extruder. The effect of a nucleating agent, talc, on the crystallization behavior, rheological and morphological properties of PLA was investigated. DSC results showed that the addition of the mineral filler in the range between 1 and 5 wt. % to the PLA matrix increases the degree of crystallinity. This finding shows that talc acted as a nucleating agent for PLA during the processing stage. The composites morphology was also studied using a scanning electron microscope (SEM). The micrographs showed that a good dispersion of talc was achieved in all compositions analyzed. The rheology of PLA/talc composites was evaluated with the dynamic mode and correlated with the aforementioned observed morphology. The results showed that the addition of the mineral filler to the PLA matrix decreased system viscosity, thus highlighting the filler's lubricant effect. As talc content increased, system's viscosity also increased, providing material with higher elastic behavior. Thermal analysis showed that the composition of 3 wt.% of talc added to polymer matrix seems to be interesting with regard to the need of articles possessing good dimension stability.

Crystallization Behavior of Poly(lactic acid) Nucleated by a Hydrazide Compound

A hydrazide compound (N-4) was used as a nucleating agent to induce the crystallization of poly (lactic acid) (PLA). PLA/N-4 samples were prepared by melt blending in an internal mixer. The melting and crystallization behavior and spherulitic morphology of the samples doped with different contents of N-4 were investigated by means of differential scanning calorimetry (DSC) and polarized light microscopy (PLM). It is found that the crystallization temperature and crystallinity increased but the spherulitic size of PLA decreased for the nucleated samples. It is indicated that N-4 is an effective nucleating agent for PLA.

Effects of POSS particles on the mechanical, thermal, and morphological properties of PLA and Plasticised PLA

AbstractThe mechanical, thermal, and morphological properties of melt compounded aminopropylisobutyl‐polyhedral oligomeric silsesquioxane (POSS)/poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG)‐plasticized PLA composites were investigated. It was found that the addition of POSS to the PLA reduced the melt viscosity of the composites acting as a lubricating agent. Dynamic mechanical analysis and tensile tests showed that the modulus and elongation at break values improved at low (1% and 3%) POSS loading levels. Scanning electron microscopy observation indicated that POSS particles were well dispersed in both PLA and plasticized PLA. The interfacial interaction of POSS with the polymer matrix was found to be better in the presence of plasticizer. The presence of POSS also affected the thermal properties of the PLA and plasticized PLA. It was revealed from DSC that POSS particles acted as a nucleating agent for PLA. Moreover, the percent crystallinity was found to be higher in the presence of POSS for both PLA and plasticized PLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011