Reactive Blending Research Articles

Toward Highly Toughened Polylactide/Polycaprolactone‐Based Polyurethane Blends With Shape Memory Property via Reactive Blending

ABSTRACTReactive blending has proven to be a versatile and efficient method for enhancing the impact toughness of polylactide (PLA). PLA/cross‐linked polycaprolactone‐based polyurethane (c‐PCLU) blends are prepared by reactive blending of PLA with PCL triol and hexamethylene diisocyanate (HDI). The reaction mechanism, compatibility, crystallization behavior, rheology behavior, mechanical performance, and shape memory property are thoroughly studied. The FTIR results confirmed that the NCO groups of HDI reacted with the hydroxyl groups of PLA and PCL triol, leading to the in situ formation of c‐PCLU and PLA‐co‐PCLU. The phase morphology exhibits a sea‐island structure, suggesting incompatibility between the two phases. The compatibility of the blends is improved with the increase of the PCL triol feeding ratio. The crystallization ability of PLA is retarded in the reactive blend. Both the elongation at break and the shape recovery ratio increase with c‐PCLU content, reaching up to 94.0% and 92.6%, respectively. These findings show that the formation of c‐PCLU greatly enhanced the toughness and shape memory performance of PLA.

Simultaneous Enhanced Mechanical Properties and Foamability of Biodegradable PBAT via Physical Cross-Linking through Reactive Blending

Simultaneous Enhanced Mechanical Properties and Foamability of Biodegradable PBAT via Physical Cross-Linking through Reactive Blending

Exploring Biodegradable Poly(butylene succinate terephthalate)/Poly(glycolic acid) Mulch Films: Reactive Blending, Performance, Degradation under UV Irradiation, and Covering Plants on Agriculture Soil

Exploring Biodegradable Poly(butylene succinate terephthalate)/Poly(glycolic acid) Mulch Films: Reactive Blending, Performance, Degradation under UV Irradiation, and Covering Plants on Agriculture Soil

Toughening Immiscible Polymer Blends: The Role of Interface-Crystallization-Induced Compatibilization Explored Through Nanoscale Visualization.

This study explores the novel approach of interface-crystallization-induced compatibilization (ICIC) via stereocomplexation as a promising method to improve the interfacial strength in thermodynamically immiscible polymers. Herein, two distinct reactive interfacial compatibilizers, poly(styrene-co-glycidyl methacrylate)-graft-poly(l-lactic acid) (SAL) and poly(styrene-co-glycidyl methacrylate)-graft-poly(d-lactic acid) (SAD) are synthesized via reactive melt blending in an integrated grafting and blending process. This approach is demonstrated to enhance the interfacial strength of immiscible polyvinylidene fluoride/poly l-lactic acid (PVDF/PLLA) 50/50 blends via ICIC. IR nanoimaging indicates a cocontinuous morphology in the blends. The blend compatibilized with SAD exhibits a higher storage modulus, as unveiled by small amplitude oscillatory shear (SAOS) in the melt state at a temperature below the melting temperature of the stereocomplex (SC) crystals and by DMTA measurements in the solid state. This increase is attributed to the formation of a 200-300 nm thick rigid interfacial SC crystalline layer that is directly visible using AFM imaging and chemically characterized via IR nanospectroscopy. This ICIC also results in a significant toughening of the blend, with the elongation at break increasing more than 20-fold. Moreover, the fracture toughness factor obtained from single edge-notch bending (SENB) tests is doubled with ICIC as compared to the uncompatibilized blend, indicating the strong crack-resistance capability as a result of ICIC. This improvement is also evident in SEM images, where thinner and longer fibrillation is observed on the fractured surface in the presence of ICIC.

Improving poly(lactic acid) fire performances via blending with benzoxazine

Improving the mechanical performance of PLA via reactive blending with thermosets is an interesting approach, however, not well explored for its fire performance improvement. With our approach, the fire performances of PLA were improved by blending PLA with a commercially available bisphenol-F-based benzoxazine. To establish the proof of concept, the benzoxazine was initially pre-cured at either 100 °C or 150 °C for a pre-selected time i.e. 60′, 80′, or 120′. The benzoxazine samples were then blended with PLA matrix via an extrusion process at 10 wt.% or 20 wt.% loadings. Detailed thermal and chemical investigations via Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC), and the evaluation of the mechanical properties, confirmed that the addition of benzoxazine does not influence the intrinsic properties of PLA. The fire performance was tested by Mass Loss Cone (MLC) calorimetry. PLA formulation with 20 wt.% of the benzoxazine cured 80′ at 150 °C, lead to a 43 % reduction of the peak of heat release rate compared to neat PLA. This was attributed to increased char formation during the combustion process. Also, the char formation permits a significant delay in the temperature increase of the sample.

Covalent Adaptable Network of Semicrystalline Polyolefin Blend with Triple-Shape Memory Effect

A covalent adaptable network (CAN) of semicrystalline polyolefin blends with triple-shape memory effects was fabricated by the reactive melt blending of maleated polypropylene (mPP) and maleated polyolefin elastomer (mPOE) (50 wt/50 wt) in the presence of a small amount of a tetrafunctional thiol (PETMP) and 1,5,7-triazabicyclo [4,4,0]dec-5-ene (TBD). The polymer blend formed a chemically crosslinked network via the reaction between the thiol group of PETMP and maleic anhydride of both polymers in the blend, which was confirmed by FTIR, the variation of torque during the melt mixing process, a solubility test, and DMA. DSC analysis revealed that the crosslinked polyolefin blends show two distinct crystalline melting transitions corresponding to each component polymer. Improved tensile strength as well as elongation at break were observed in the crosslinked blend as compared to the simple blend, and the mechanical properties were maintained after repeated melt processing. These results suggest that thermoplastic polyolefin blends can be transformed into a high-performance and value-added material with good recyclability and reprocessability.

Preparation of super toughened flame-retardant polylactic acid with an in situ hyperbranched structure by reactive blending with a phosphorus-containing copolyester and hexamethylene glycidyl cyclotriphosphazene

Achieving both super toughness and flame retardancy in polylactic acid (PLA) materials hinges on resolving the interface compatibility issues between flame retardants, toughening agents, and PLA, as well as overcoming potential antagonisms between these components. Here, we present an approach employing hyperbranched structures to simultaneously enhance the toughness and flame retardancy of PLA materials. Our strategy involved the reactive blending of PLA with a quaternary bio-based phosphorus-containing copolyester (PPE) featuring side hydroxyl groups and hexamethylene glycidyl cyclotriphosphazene (HGCP). The multi-epoxy groups of HGCP reacted with the hydroxyl and carboxyl groups present in PPE and PLA, resulting in the formation of hyperbranched PLA-PPE copolymers. The hyperbranched copolymers provided great interfacial compatibilization and low viscosity, synergistically promoting the melt-dripping flame-retardant mechanism facilitated by PPE, aiding in the rapid removal of heat and combustible material from the pyrolysis zone. Consequently, the PLA/PPE/HGCP blends exhibited super toughness, achieving a maximum notched impact strength of 70.2 kJ/m2. Additionally, the blends demonstrated a 27 % LOI and can pass the UL-94 V-0 rating. Moreover, all the blends are biodegradable in a Proteinase K solution. This research underscores the efficacy of utilizing hyperbranched structures as a promising strategy for the development of PLA materials with simultaneous enhancement of processability, toughness, and flame retardancy.

Flame-retardant and tough poly(lactic acid) with well-preserved mechanical strength via reactive blending with bio-plasticizer and phosphorus derivative

With sustainable development, advanced poly(lactic acid) (PLA) with superior toughness and flame retardancy is highly demanded in various industries, but the current design strategies often fail to achieve such bioplastics. In this work, flame-retardant and tough PLA bioplastics with well-preserved thermal stability and mechanical strength and enhanced UV resistance and soil degradation are prepared by solvent-free, reactive blending of PLA, bio-based epoxidized soyabean oil (ESO) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). With the introduction of 10.0 wt% ESO and 3.0 wt% DOPO, the resultant PLA/10E/3D bioplastic has a high tensile strength of 52.8 MPa, with 26.3 times and 67.5 % increases in elongation at break and impact strength compared to those of PLA due to the toughening effect of ESO and the rigid structure of DOPO. The superior toughness of PLA/10E/3D enables it to outperform previous flame-retardant PLA counterparts. PLA/10E/3D achieves a vertical burning (UL-94) V-0 classification and a limiting oxygen index (LOI) of 27.5 %, indicative of satisfactory flame retardancy. Compared with PLA, PLA/10E/3D maintains high thermal stability and shows significantly enhanced UV-protecting and soil degradation properties. Therefore, this work delivers a green and scalable reactive processing method to create flame-retardant, tough yet strong bioplastics with improved soil decomposition and UV resistance, which contributes to sustainable development.

Zinc oxide as a new catalyst for poly(lactic acid)/maleated polypropylene reactive blending: an approach to enhance miscibility and mechanical properties

Zinc oxide as a new catalyst for poly(lactic acid)/maleated polypropylene reactive blending: an approach to enhance miscibility and mechanical properties

Effects of chain extender types and contents on the properties of modified recycled polyethylene terephthalate

AbstractRecycling polyethylene terephthalate (PET) bottles post‐consumption is highly desirable but remains challenging because of their poor properties after recycling. Using a chain extender to rejoin the cleaved polymer chains is considered a reasonable solution to this issue. However, the functionality of the chain extenders affects the cross‐linking and properties of the resulting products. Therefore, this study focuses on the effects of functional groups and number of chain extenders on the properties of recycled polyethylene terephthalate (rPET). Three commercial chain extenders—methylene diphenyl diisocyanate (MDI), triphenyl phosphite (TPP), and Joncryl (JC), represented as di‐, tri‐, and multi‐functional chain extenders, respectively—are introduced into rPET by reactive blending. The intrinsic viscosity, rheological properties, thermal properties, and mechanical properties of the chain‐extended rPET are investigated. The results indicate that all the chain extenders increase the molecular weight of rPET. Di‐ and multi‐functional chain extenders (MDI and JC) induce branching and cross‐linking owing to the highly reactive functional groups, whereas a tri‐functional chain extender (TPP) showed the lowest improvement in mechanical properties, owing to chain scission from by‐products occurring during chain extension. Furthermore, increasing the content of all chain extenders significantly increased their intrinsic viscosity, cross‐linking, and mechanical properties.

Reprocessable Cross-Linked EVA/Silica Nanocomposites with Superior Mechanical Properties via One-Step and Scalable Reactive Blending

Reprocessable Cross-Linked EVA/Silica Nanocomposites with Superior Mechanical Properties via One-Step and Scalable Reactive Blending

Super-tough polylactic acid blends via tunable dynamic vulcanization of polyurethanes with ultrahigh bio-based content

Polylactic acid (PLA), a biodegradable plastic derived from renewable resources, is commercially available but has been limited in application owing to its inherent brittleness. To address this, researchers explored a reactive blending strategy using polyurethane (PU) to enhance PLA toughness. This method is straightforward and effective, yet most PUs are derived from petroleum or containing low bio-based content. Herein, we developed a bio-based PU (BPU) with double bonds for dynamic vulcanization to toughen PLA, using 1,3-polypropanediol (PO3G) and 1,5-pentane diisocyanate (PDI) with an ultrahigh bio-based content of 93.8 %. The toughness and tensile strength of the PLA/BPU blends were adjustable by modifying the BPU content. In particular, the toughness of the blends could reach 68.69 kJ/m2 by varying the amount of BPU. In addition, the BPU20–0.1 sample demonstrated an optimal balance of stiffness and toughness, exhibiting a tensile strength of 47.8 MPa and a notched impact strength of 54.86 kJ/m2. This research broadens the scope for toughening PLA using BPUs, thereby diminishing the dependency on petrochemical resources.

Enhancing poly(lactic acid)/maleated polypropylene blend with magnesium oxide catalyst: a reactive blending approach for improved mechanical properties

Some defects of polylactic acid (PLA), especially its poor mechanical properties, were modified using a minimum content of non-biodegradable maleated polypropylene (MAPP). To this end, first, the amount of MAPP was optimized, which was 20 wt.%. Second, MgO was used as a new catalyst to improve the exchange reactions between active groups in both polymers in a reactive blending process. Tensile and izod analyses showed that, compared to neat PLA, with a slight decrease in modulus and tensile strength, elongation at break, and impact resistance were improved in the presence of 20 and 0.1 wt.% of MAPP and MgO, respectively. This improvement in mechanical properties can be related to the exchange reactions between two polymers and the formation of PLA-MAPP block copolymers. MFI and WDCA analyses demonstrated the increase in melt flowability and surface hydrophilicity of the resulting blends, respectively. DSC analysis showed that the Tg values of both polymers approached each other in the presence of catalyst. Also, the elimination of cold crystallization of PLA and the decrease in the Tm and crystallinity of both polymers are clear reasons for the miscibility of the alloy. TEM displayed the proper dispersion of MgO nanoparticles within the polymer matrix, and in addition, the XRD test also proved the decrease in the crystallinity of both polymers and appropriate miscibility of the samples containing 20 and 0.1 wt.% of MAPP and MgO, respectively. These results can promise the design of a compound with the maximum amount of PLA for further use in various industries.

Crystallographic Texture Evolution in 3D Printed Polyethylene Reactor Blends.

In this work, crystallographic texture evolution in 3D printed trimodal polyethylene (PE) blends and high-density PE (HDPE) benchmark material were investigated to quantify the resulting material anisotropy, and the results were compared to materials made from conventional injection molded (IM) samples. Trimodal PE reactor blends consisting of HDPE, ultrahigh molecular weight PE (UHMWPE), and HDPE_wax have been used for 3D printing and injection molding. Changes in the preferred orientation and distribution of crystallites, i.e., texture evolution, were quantified utilizing the wide angle X-ray diffraction through pole figures and orientation distribution functions (ODFs) for 3D printed and IM samples. Since the change in weight-average molecular weight (Mw) of the blend was expected to significantly affect the resulting crystallinity and orientation, the overall Mw of the trimodal PE blend was varied while keeping the UHMWPE component weight fraction to 10% in the blend. The resulting texture was analyzed by varying the overall Mw of the trimodal blend and the process parameters in 3D printing and compared to the texture of conventional IM samples. The printing speed and orientation (defined with respect to the axis along the length of the samples) were used as the variable process parameters for 3D printing. The degree of anisotropy increases with an increase in the nonuniform distribution of intensities in pole figures and ODFs. All the highest intensity major texture components in IM and 3D printed samples (0° printing orientation) of reactor blends are observed to have crystals oriented in [001] or [001̅]. Overall, for the same throughput, 3D printed samples in the 0° orientation showed greater texture evolution and higher anisotropy compared to IM samples. Most notably, an increase in 3D printing speed increased the crystalline distribution closer to the 0° direction, increasing the anisotropy, while deviation from this printing orientation reduced crystalline distribution closer to the 0° direction, thus increasing isotropy. This demonstrates that tailoring material properties in specific directions can be achieved more effectively with 3D printing than with the injection molding process. Change in the overall Mw of the trimodal PE blend changed the preferential orientation distribution of the crystal planes to some degree. However, the degree of anisotropy remained the same in almost all cases, indicating that the effect of molecular weight distribution is not as significant as the printing speed and printing orientation in tailoring the resulting properties. The 3D printing process parameters (speed and orientation) were shown to have more influence on the texture than the material parameters associated with the blend.

Effect of Palm Stearin as a Compatibilizers in PBAT/Zein Blends Biodegradable Polymer

In this study, the introduction of PBAT was conducted through reactive blending with Zein, a renewable natural biopolymer derived from corn, in the presence of Palm Stearin (PS); one of the components in palm oil. The objective of this study is to examine the impact of mechanical forces on PBAT/Zein composites, both with and without the presence of PS. The PBAT/Zein and PBAT/Zein/PS blends will be subjected to various experiments, including mechanical testing and thermal analysis. Variation of different formulations of composition, comprised of PBAT, Zein and PS were used in this study. The thermal and mechanical properties of the PBAT/Zn blend were assessed through the utilization of mixing characteristics as well as thermal and mechanical properties. Based on the findings, it has been determined that the optimal composition for the PBAT/Zein blend is achieved when the blend contains 10% zein content. Furthermore, the optimal composition of PBAT/Zein/PS is achieved when 10 phr of PS are included in the blend.

A generalizable reactive blending strategy to construct flame-retardant, mechanically-strong and toughened poly(L-lactic acid) bioplastics

Poly(L-lactic acid) (PLA) is an environmentally-friendly bioplastic with high mechanical strength, but suffers from inherent flammability and poor toughness. Many tougheners have been reported for PLA, but their synthesis usually involves organic solvents, and they tend to dramatically reduce the mechanical strength and cannot settle the flammability matter. Herein, we develop strong, tough, and flame-retardant PLA composites by reactive blending PLA, 6-((double (2-hydroxyethyl) amino) methyl) dibenzo [c, e] [1,2] oxyphosphate acid 6-oxide (DHDP) and diphenylmethane diisocyanate (MDI) and define it PLA/xGH, where x indicates that the molar ratio of -NCO group in MDI to -OH group in PLA and DHDP is 1.0x: 1. This fabrication requires no solvents. PLA/2GH with a -NCO/-OH molar ratio of 1.02: 1 maintains high tensile strength of 63.0 MPa and achieves a 23.4 % increase in impact strength compared to PLA due to the incorporation of rigid polyurethane chain segment. The vertical combustion (UL-94) classification and limiting oxygen index (LOI) of PLA/2GH reaches V-0 and 29.8 %, respectively, because DHDP and MDI function in gas and condensed phases. This study displays a generalizable strategy to create flame-retardant bioplastics with great mechanical performances by the in-situ formation of P/N-containing polyurethane segment within PLA.

Super-tough polylactic acid blends via tunable dynamic vulcanization of biobased polyurethanes

Polylactic acid (PLA) is a biobased plastic with biodegradability, biocompatibility, and high-strength properties; however, its inherent brittleness limits its widespread application. Toughness can be improved by physical blending, chemical copolymerization, and reactive blending of PLA with flexible components. As highly engineered block polymers, polyurethanes (PUs) can improve the toughness of PLA through physical blending or in situ polymerization. However, current research on PU-toughened PLA is hindered by poor compatibility, toughening, and dependence on petrochemical resources. Therefore, to address these issues, we developed a novel biobased millable polyurethane (PO3G-MPU) containing unsaturated double bonds and used it to toughen PLA via peroxide-initiated dynamic vulcanization. The results showed that balancing toughness and strength is possible, with the notched impact strength and tensile strength of the prepared PLA/MPU blends reaching 59.01 kJ/m2 and 43.97 MPa, respectively. The massive shear yielding and plastic deformation of the PLA matrix induced by the crosslinked PO3G-MPU were responsible for the main toughening mechanism. These results provide a new perspective on research on PU-toughened PLA.

In situ synthesis of novel trans‐1, 4‐polyisoprene/isotactic polybutene reactor blends with multi‐component structure

AbstractIn this paper, a series of novel trans‐1, 4‐polyisoprene/isotactic polybutene (TPI/iPB) in‐reactor blends were synthesized by isoprene and butene sequential two‐stage polymerization technology with spherical TiCl4/MgCl2 type Ziegler‐Natta catalyst. The components, structures, and properties of the as‐obtained TPI/iPB reactor blends were characterized by gel permeation chromatography, Fourier transform Infrared spectroscopy, and differential scanning calorimetry. The active trans‐1, 4‐polyisoprene (TPI) particles obtained in the initial isoprene polymerization by the Z‐N catalyst can be acted as microreactors to initiate butene polymerization subsequently. The TPI/iPB reactor blends with varied components were in situ synthesized within the reactor. The preparative‐temperature rising elution fractionation (p‐TREF) technique was used to fractionate the TPI/iPB reactor blends based on the elution temperature ranged from −40°C to 90°C. The weight distribution and microstructure of each fraction were investigated. The reactor blends are composed of crystallizable high trans‐1, 4‐uint polyisoprene obtained from the first‐stage isoprene polymerization, high isotactic polybutene obtained from the second‐stage butene polymerization and TPI‐b‐iPB block copolymer with different sequence structure obtained from the initial time of the second stage. This work is expected to propose the possible polymerizations of a‐olefins and conjugated dienes by using heterogeneous Ziegler‐Natta catalyst and provide a kind of novel rubber/plastic reactor blend materials.Highlights The first synthesis of the trans‐1, 4‐polyisoprene/isotactic polybutene reactor blends. p‐TREF technique was used to analyze the composition of TPI/iPB reactor blends. Detailed structure characterization of the fractions including GPC and NMR TPI‐b‐iPB block copolymer can be obtained through the sequential polymerization. Rubber/plastic reactor blend materials were fabricated by the Z‐N catalyst.

Dual reconfigurable network from a semi-crystalline functional polyolefin

A statistical copolymer p(E-co-GMA) of ethylene and glycidyle methacrylate (4.5 wt%) is considered as a starting point towards semicrystalline networks with exchangeable links. Application of the binomial law to size exclusion chromatographic data suggests that chains deprived of reactive comonomers would represent less than 6 wt% of the total, allowing to expect the formation of high gel-content networks. Experimentally, up to 98 wt% gel is obtained upon modification with 3,3′-dithiopropionic acid (DTPA). The crosslinking reaction can be performed in the molten state through a 2-steps procedure: 1°) x mol. of a commercial grade p(E-co-GMA), y mol. of DTPA and z mol. of triazabicyclodecene (TBD) are sheared in a twin-screw compounder at 115 °C, a temperature right above the melting point of the polymer precursor, without triggerring the epoxy-acid addition; 2°) the thermolatent reactive blend thereby obtained is then crosslinked at 170 °C. Samples with x = 1, y = 1 to 4 and z = 0 to 0.8 were thus prepared and evaluated. The presence of TBD accelerates disulfide exchange reaction, possibly by involvement of the thiolate anion whereas it decelerates the epoxy-acid addition. The final networks present several characteristic properties of vitrimers such as insolubility in xylene above the melting point, thermo-activated stress relaxation and creep. Particular shape memory regimes, related to the semicrystalline vitrimer character and the high insoluble fraction are demonstrated. Eventually, production scale-up using continuous reactive extrusion is evaluated.

Formulating PBS/PLA/PBAT blends for biodegradable, compostable packaging: The crucial roles of PBS content and reactive extrusion

The use of biodegradable polymers such as Poly (lactic acid) (PLA), Poly(butylene succinate) (PBS), and Poly(butylene adipate-co-terephthalate) (PBAT) is constantly increasing to try to substitute non-biodegradable plastics. Blending is a viable option to improve the morphology and the mechanical and heat resistance properties of biodegradable polymers. Thus, in this work, a biodegradable and compostable PLA/PBAT blend was improved by adding PBS, leading to non-reactive, melt-mixed PLA/PBAT/PBS ternary blends. The PLA/PBAT ratio was fixed at 1:1, while the PBS varied from 0 to 40 wt%. Polarized Light Optical Microscopy (PLOM) imaging showed that micro-spherulitic PBS was localized at the interface between PLA and PBAT in the blend, acting as a compatibilizer, reducing the interfacial tension and refining the ternary blend's morphology. Consequently, the mechanical properties improved, such as the elongation at break, which increased from 70 to 300 %. However, these tertiary non-reactive blends were found to lack adequate rheological properties to be processed by blown film extrusion. Therefore, reactive blending was performed by adding peroxide and carbodiimide, leading to a finer morphology and improved rheological properties. Thus, these reactive blends were successfully processed by blown film extrusion. Two types of blown films were produced, Tubular and Champagne films (DDR/BUR ratio of 37.6 and 5.2, respectively). Both types of blown films exhibited adequate ductile mechanical properties for film packaging applications, as well as high seal strength and good thermal resistance. In addition, their specific mechanical properties were a function of blend composition and the degree of biaxial orientation produced during the extrusion-blowing process.