Rubber Domains Research Articles

Flame Retardancy and Properties of Thermoplastic Vulcanizates from Dibutyl Phosphate-Bound Natural Rubber/Ethylene Vinyl Acetate Blends

ABSTRACT Dibutyl phosphate-bound epoxidized natural rubber (DBNR) was synthesized from natural rubber latex via epoxidation using a 20 mol% intermediate. Successful formation of epoxidized natural rubber (ENR-20) and DBNR was confirmed by FTIR analysis. Thermoplastic vulcanizates (TPVs) were prepared by dynamically vulcanizing blends of DBNR and ethylene-vinyl acetate copolymer (EVA). The 50/50 DBNR/EVA TPV exhibited higher mixing torque during vulcanization, indicative of increased shear stress, shear rate, and tensile strength. This was attributed to finer dispersion of vulcanized rubber domains in the EVA matrix, leading to enhanced interfacial adhesion. Elongation at break decreased with increasing EVA content, while hardness and tension set increased, suggesting reduced elasticity at higher EVA proportions. Under heat aging, TPVs experienced degradation of mechanical properties and increased tension set, indicating loss of elastomeric behavior. Significantly, DBNR exhibited a low burning rate of 0.2 mm/s, imparting inherent flame retardancy. The burning rate of DBNR/EVA TPVs decreased with increasing DBNR content, demonstrating improved flame retardancy. Overall, DBNR/EVA TPVs exhibited favorable mechanical properties and flame retardancy, making them suitable for applications requiring flame-retardant elastomeric materials.

PPR/EPDM/POE-g-MA/OMMT nanocomposites with superior low-temperature toughness based on embedded OMMT within compound rubber dispersion phase

A new approach to produce polypropylene random copolymer/ethylene propylene diene monomer/polyolefin elastomers modified with maleic anhydride/organic modified nanomontmorillonite (PPR/EPDM/POE-g-MA/OMMT) nanocomposites with superior low-temperature toughness was conducted. The brittle-ductile transition temperature (Tbd) of PPR/EPDM/POE-g-MA/OMMT nanocomposites reduced from −20 °C to −40 °C. The incorporation of POE-g-MA results in the distribution of OMMT changing from the interfacial distribution into dispersed inside rubber phase and a compound rubber dispersed phase in PPR/EPDM/POE-g-MA/OMMT nanocomposites was comprised of EPDM, POE-g-MA and embedded OMMT. The synergistic effect of POE-g-MA and OMMT was considered to result from the special compound rubber dispersed phase consisting of EPDM and POE-g-MA as well embedded OMMT, which led to the reduction in space between rubber domains and the increase in internal friction and ultimately brought about the remarkable enhancement in mechanical properties.

Nanoindentation Response of Structural Self-Healing Epoxy Resin: A Hybrid Experimental-Simulation Approach.

In recent years, self-healing polymers have emerged as a topic of considerable interest owing to their capability to partially restore material properties and thereby extend the product's lifespan. The main purpose of this study is to investigate the nanoindentation response in terms of hardness, reduced modulus, contact depth, and coefficient of friction of a self-healing resin developed for use in aeronautical and aerospace contexts. To achieve this, the bifunctional epoxy precursor underwent tailored functionalization to improve its toughness, facilitating effective compatibilization with a rubber phase dispersed within the host epoxy resin. This approach aimed to highlight the significant impact of the quantity and distribution of rubber domains within the resin on enhancing its mechanical properties. The main results are that pure resin (EP sample) exhibits a higher hardness (about 36.7% more) and reduced modulus (about 7% more), consequently leading to a lower contact depth and coefficient of friction (11.4% less) compared to other formulations that, conversely, are well-suited for preserving damage from mechanical stresses due to their capabilities in absorbing mechanical energy. Furthermore, finite element method (FEM) simulations of the nanoindentation process were conducted. The numerical results were meticulously compared with experimental data, demonstrating good agreement. The simulation study confirms that the EP sample with higher hardness and reduced modulus shows less penetration depth under the same applied load with respect to the other analyzed samples. Values of 877 nm (close to the experimental result of 876.1 nm) and 1010 nm (close to the experimental result of 1008.8 nm) were calculated for EP and the toughened self-healing sample (EP-R-160-T), respectively. The numerical results of the hardness provide a value of 0.42 GPa and 0.32 GPa for EP and EP-R-160-T, respectively, which match the experimental data of 0.41 GPa and 0.30 GPa. This validation of the FEM model underscores its efficacy in predicting the mechanical behavior of nanocomposite materials under nanoindentation. The proposed investigation aims to contribute knowledge and optimization tips about self-healing resins.

A nonequilibrium constitutive equation for tensile behavior of polyolefinic thermoplastic vulcanizates

Polyolefinic thermoplastic vulcanizates (TPVs) composed of iPP (isotactic polypropylene) and crosslinked EPDM (ethylene-propylene-diene rubber) prepared by dynamic vulcanization process exhibit rubber domains dispersed in the iPP matrix, even though the EPDM component is the major component. Here we proposed a kinetic nonequilibrium constitutive equation that considers the transition of the mechanical nature from plasto-rigid deformation to rubbery deformation during uniaxial extension to explore the origin of the thermoplastic elastomer behavior of TPV (thermoplastic vulcanizate) materials. Fitting of the constitutive equation to the experimental stress‒strain curves quantitatively revealed the critical transition point of the mechanical properties. The transition shifted to higher strains with decreasing EPDM content. In situ wide-angle X-ray diffraction profiles monitored during the uniaxial extension confirmed the mechanical transition process.

Importance of an interfacial agent for stabilizing rubber domains of thermoplastic vulcanizates during strong shearing

Rubber nanoparticles in thermoplastic vulcanizate (TPV) may agglomerate during processing, leading to the deterioration of mechanical properties of TPV. This work shows how important an interfacial agent (Polyolefin Elastomer, POE) can be for stabilizing rubber particles in Ethylene-Propylene-Diene Monomer (EPDM)/polypropylene (PP) TPV during processing. The optimal type and dosage of POE was theoretically calculated. The time at which the POE interfacial agent is added is optimized based on the fragmentation kinetics of the EPDM rubber particles. The experimental results show that POE is indeed encapsulated on EPDM rubber particles in TPV, resulting in the large decrease in average size of EPDM rubber particles from 1.2 μm for TPV without encapsulation to 0.7 μm for TPV encapsulated with optimal dosage of POE. As a result, at an optimal dosage of POE, the elastic modulus, tensile strength, and elongation at break of TPV simultaneously increases by 70 %, 44 %, and 37 %, respectively.

Processing–microstructure–fracture toughness relationships in PP/EPDM/SiO2 blend‐nanocomposites: Effect of mixing sequence

AbstractThis study investigates the mechanical properties and fracture behavior of polypropylene (PP)‐based blend‐nanocomposites comprising 30 wt.% ethylene–propylene–diene monomer (EPDM) and 5 wt.% SiO2 nanoparticles. Different mixing sequences were employed to prepare the nanocomposites, and the resulting morphology development and dispersion states of modifiers were analyzed. Mechanical performance of the nanocomposites was evaluated through quasi‐static and high‐speed dynamic fracture tests. The dispersion and distribution of SiO2 nanoparticles within the nanocomposites were significantly influenced by the mixing protocol. In impact fracture tests, the presence of nanoparticles exhibited a beneficial efffect on fracture energy, demonstrating a synergistic toughening effect of the soft EPDM and rigid SiO2 particles. Conversely, adverse effects were observed in quasi‐static tests. Essential work of fracture (EWF) parameters indicated an increase in the yielding component and a decrease in the necking‐to‐tearing component with SiO2 incorporation into the PP/EPDM blends. During impact loadings, the highest improvement in crack propagation resistance was observed in nanocomposites with nanoparticles localized around the rubbery domains forming a network‐like structure of EPDM/SiO2‐nanoparticles. Morphologies where rubber domains and nanoparticles were separately distributed in the PP matrix resulted in the lowest fracture parameters. Energy dissipation mechanisms were elucidated, revealing multiple void formation followed by matrix shear yielding as the primary source under both quasi‐static and impact fracture conditions. In the latter case, stress‐concentrating percolated structures in the PP matrix facilitated the nucleation of dilatational bands evolving into highly stretched void‐fibrillar structures upon further loading. These findings contribute valuable insights into tailoring nanocomposite morphologies for enhanced mechanical performance in different loading scenarios.Highlights Fracture behavior of PP/EPDM/SiO2 ternary systems was evaluated by EWF methodology and Izod impact test. Rubber particles surrounded by silica nanoparticles led to a percolated morphology and as a result to superior impact resistance. EWF parameters were mostly controlled by the tearing‐related parts regardless of phase morphology. The impact toughness was mainly controlled by the dispersion and distribution characteristics of the SiO2 nanoparticles.

Morphology evaluation and mechanical properties of oil-resistant thermoplastic vulcanizates comprising carboxylated nitrile butadiene rubber and thermoplastic polyurethane and their comparison with commercial grades

The morphology, the mechanical properties, and the oil-resistance of thermoplastic vulcanizates (TPVs) of carboxylated nitrile butadiene rubber (XNBR) and thermoplastic polyurethane (TPU) were studied & compared with the commercial ethylene-propylene-diene monomer (EPDM)/polypropylene (PP) TPVs from two suppliers. The rubber phase in these new generations of TPVs was cured with an addition-type curative, and no oil & compatibilizer were required to make these TPVs processable. Three XNBR/TPU TPVs were made with different rubber/plastic ratios (15/85, 30/70, and 45/55). The AFM analysis showed that the morphology shifted from a continuous plastic phase to a co-continuous phase with increased rubber content. The rubber domains in these TPVs were not as discrete as reported in the literature for the EPDM/PP TPVs. Still, because of using an addition-type curative, unlike peroxide and resole phenolic resin curatives for the latter, the former TPVs had a significantly better balance of rubber and plastic properties. The oil resistance of these TPVs was 3.5–5 times better than the commercial EPDM/PP TPVs. These promising results show advancement in the TPV world and make these TPVs appealing for hydraulic oil applications.

Functionalized liquid polyisoprene as a promising toughening agent for poly(lactic acid): Combining stiffness and toughness

AbstractLiquid polyisoprene rubbers (LIR) containing anhydride and carboxylic groups along their chains were successfully employed as toughening agent for poly(lactic acid) (PLA) without great influence on the stiffness of the matrix. In fact, the addition of 5% of these functionalized LIR resulted in an improvement of toughness and impact resistance of more than 2000%, whereas the reduction of the yield stress stayed in the range of 12%. No significant variation of the Young modulus was observed for the modified PLA samples. The effect of the LIR on the rheological and thermal properties of PLA was also investigated. The glass transition temperature obtained from dynamic‐mechanical analysis of the PLA matrix was not affected by the addition of 10% of the liquid rubber. The scanning electron microscopy analysis revealed a significant decrease in the rubber domains for the blends containing LIR functionalized with anhydride groups. Finally, the modified PLA with anhydride‐functionalized LIR was able to produce transparent film with outstanding mechanical performance than neat PLA, making this material a good option for food packaging.

Unleashing the power of SAN: Innovative in situ fibrillation and moisture-crosslinking techniques yield stronger, tougher, and Greener material than ABS

Styrene-acrylonitrile (SAN) is widely used in various applications due to its excellent properties, including thermal stability, dimensional stability, and chemical resistance. However, poor toughness has limited its applications. In this study, an innovative in-situ fibrillation technique was employed to create nanofibers of thermoplastic polyurethane (TPU) in the SAN matrix. Silane was initially grafted onto TPU, followed by the development of nanofibril TPU, and lastly, post-crosslinking was conducted to retain the nanofibril structure. The grafting reaction was analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR). FTIR and NMR data were used in conjunction with the gel content test to confirm the involved grafting, hydrolysis, and crosslinking reactions. Observations with a Scanning Electron Microscope (SEM) revealed the formation of nanoscale TPU fibers ranging from 90 to 360 nm for various TPU contents. Because of nanofibril TPU's high aspect ratio and the effective SAN-TPU interaction, the required TPU decreased to 1 wt%. Due to the minimal use of rubber, SAN's stiffness was not compromised and compared to pure SAN and a spherical structure with the same concentration, tensile toughness increased by 350% and 200%, respectively. The fracture mechanism was investigated for both the short and long timeframes of deformation, and several potential hypotheses were proposed. Finally, this novel toughened SAN was compared with one of the most effective toughened acrylonitrile butadiene styrene (ABS) materials that contain 40 wt% spherical butadiene rubber (BR) domains.

Mechanical and morphological properties of PP/XNBR blends produced with rubber latex

In this work, polypropylene (PP)/carboxylated acrylonitrile butadiene rubber (XNBR) binary blends were prepared with the elastomer component dosed in its suspension (latex) form into the polymer matrix during melt compounding. For this purpose, samples containing 0-20 wt.% rubber were prepared using two different PP grades as matrices with lower and higher viscosity. Analogous reference samples with the same composition were also fabricated using traditional melt mixing by introducing the rubber in its dry, bulk form in order to analyze the efficiency of the latex route. Mechanical, thermomechanical and morphological analyses were used to investigate the structure-property relationships of the blends. Based on the SEM images the average domain size of the dispersed XNBR domains became markedly smaller when the rubber was introduced in its suspension form into the PP. Based on the Charpy impact tests and the tensile test results, the decreased rubber domain size led to improved ductility and toughness. The improvement was more prominent when the difference between the viscosity of the PP matrix and the XNBR rubber was higher.

Polypropylene/polyolefin elastomer composites with enhanced impact strength: the effect of rubber domain size on toughness

Polypropylene/polyolefin elastomer composites with enhanced impact strength: the effect of rubber domain size on toughness

Effect of Temperature on the Functionalization Process of Structural Self-Healing Epoxy Resin

This work deals with developing a self-healing resin designed for aeronautical and aerospace applications. The bifunctional epoxy precursor was suitably functionalized to enhance its toughness to realize good compatibilization with a rubber phase dispersed in the hosting epoxy resin. Subsequently, the resulting mixture was loaded with healing molecules. The effect of the temperature on the epoxy precursor’s functionalization process was deeply studied. Fourier trans-former infrared (FT-IR) spectroscopy and dynamic mechanical analyses (DMA) evidenced that the highest temperature (160 °C) allows for obtaining a bigger amount of rubber phase bonded to the matrix. Elastomeric domains of dimensions lower than 500–600 nanometers were found well distributed in the matrix. Self-healing efficiency evaluated with the tapered double cantilever beam (TDCB) method evidenced a healing efficiency for the system functionalized at 160 °C higher than 69% for all the explored fillers. The highest value was detected for the sample with DBA, for which 88% was found. The healing efficiency of the same sample functionalized at 120 °C was found to decrease to the value of 52%. These results evidence the relevant role of the amount and distribution of rubber domains into the resin for improving the resin’s dynamic properties. The adopted strategy allows for optimizing the self-healing performance.

Rigid molecular chains trapped reactive elastomers for high performance PLLA composites with excellent tough-strength balance

The enhancement in the stiffness-toughness balance of PLLA composites poses great challenges. Herein, we proposed a two-step reactive processing strategy to design unique “sub-inclusion” microstructure for high performance polylactide (PLLA) composites. The rigid PLLA chains trapped reactive elastomer (RCRE) was first prepared by the reactive blending of a multiple-carboxyl PLLA (mcPLLA) with the random copolymer of ethylene-acrylic ester-glycidyl methacrylate (EGMA). The pre-grafted mcPLLA chains can be fixed and trapped in the rubber domains, inducing sub-inclusion morphology after the following mixing of RCRE with the virgin PLLA. Promisingly, excellent stiffness-toughness balance can be realized: on the one hand, the notched impact strength of the obtained PLLA alloys was as high as 58.7 kJ/m2, which was more than 8 times of the virgin EGMA toughened PLLA blend (7.0 kJ/m2) at the same EGMA content (15 wt%); on the other hand, the Young's modulus and tensile strength kept almost the same (1.4 GPa and 47 MPa). The synergistic improvement of the PLLA composites is attributed to the sub-inclusion structure in the dispersed rubber domains, as well as the strong interfacial adhesions. This work expands the scope promising to prepare high-performance polymer composites with excellent stiffness-toughness balance via construction of sub-inclusion morphology, and also provides depth of understanding on toughening mechanism for plastic/elastomer system.

Miscibility and Optimization of the Liquid Rubber Content in the Resins of Light-Cured Dental Composites

Fracture toughness is one of the main factors influencing the durability of light-cured composites used for dental restorations and fillings. One of the methods of increasing the fracture toughness is the modification of the matrix with liquid acrylonitrile-free liquid rubber. This study aimed to assess the miscibility of acrylonitrile-free liquid rubber with a blend of resins and their stability over time, and to determine the optimal amount of liquid rubber (LR) in the blend due to mechanical properties. Two blends of dimethacrylate resins were used: resin "F" composed of BisGMA (60 wt.%), TEGDMA (20 wt.%), BisEMA (10 wt.%) and UDMA (10 wt.%), and "C" resin containing BisGMA (40 wt.%), TEGDMA (40 wt.%), BisEMA (10 wt.%) and UDMA (10 wt.%). The modifier Hypro® 2000X168LC VTB liquid rubber was used in at 1%, 2%, 3%, 4%, 5%, 10%, 15% and 20% by weight in the resin blend. The miscibility was assessed by microscopy. The fracture toughness, flexural strength and Young's modulus were determined in the bending test. The results showed that the solubility of the liquid rubber depends on the ratio of BisGMA/TEGDMA in the resins. In resins with 40 wt.% TEGDMA, the LR solubility was as high as 5%, while resins with 20 wt.% TEGDMA, the liquid rubber did not dissolve. The LR-resin mixtures showed good time stability, and no changes in the size or morphology of the rubber domains were found after 24 h of mixing. The maximum fracture toughness (2.46 MPa m1/2) was obtained for 5 wt.% LR in resin F and for 15 wt.% LR in resin C (2.53 MPa m1/2). The modification with liquid rubber resulted in an exponential reduction in both flexural strength and Young's modulus. The analysis of the results of the mechanical tests allowed us to determine the optimal amount of LR for both resins. For resin F it was 5.4 wt.%, and for resin C it was 8.3 wt.%. It can be stated that the optimal amount of liquid rubber increases with its solubility in the resin.

Effects of compatibilizers on microstructural and viscoelastic properties of polypropylene/polybutadiene thermoplastics vulcanizates

AbstractCompatibilized thermoplastic vulcanizates (TPVs) based on polypropylene (PP) and polybutadiene rubber (PBR) were developed through the melt‐mixing method, and their morphological, rheological, and dynamic mechanical properties were investigated. The composition of PBR/PP blends (30/70 and 40/60) was designed in a way to study the interrelationship between the compatibilizer content and blend composition. In this study, a hydrocarbon resin (MS 40) was employed as the compatibilizer. Based on morphological analysis, the addition of compatibilizer in both blend compositions led to a finer and more uniform distribution of rubber domains; however, only for 40/60 composition, the higher content of compatibilizer caused the formation of a co‐continuous morphology. Both dynamic and static rheology results were highly susceptible to the compatibilizer content and blend composition. According to the storage and loss modulus curves, the incorporation of PBR into PP resulted in a significantly enhanced elastic response with 30/70 composition showing lower elasticity. The viscosity upturn in complex viscosity curves indicated the formation of a three‐dimensional network of dispersed rubber domains within the matrix, which led to the appearance of a highly elastic response. Based on the dynamic mechanical analysis, the highly restricted macromolecular motions upon the addition of a compatibilizer confirmed the enhanced compatibility of TPVs.

The effect of dynamic vulcanization systems on the mechanical properties and phase morphology of PLA/NR reactive blends

The effects of dynamic vulcanization systems including sulfur, peroxide, and sulfur/peroxide mixed vulcanization were investigated for dynamically-vulcanized blends of polylactic acid (PLA) and natural rubber (NR) at the PLA/NR ratio of 85/15. For the sulfur system, the CV sub-system (CV1), which used much lower accelerator (TBBS) content than the EV sub-system, rendered higher impact strength and higher %crystallinity. When compared to the peroxide system using DCP as a curative, the impact strength of CV1 sample was almost 4 times lower than the peroxide-cured sample even though their rubber domain sizes and size distributions were comparable. Interestingly, the highest impact strength which was almost 6 times that of the unmodified PLA/NR was achieved when using the mixed sulfur/peroxide system at the CV1/peroxide ratio of 30:70 (S30/DCP70). The lower impact strength of the sulfur-cured system (CV1) compared to those of the peroxide and the mixed-vulcanization systems was potentially due to its significantly higher % crystallinity.

Evaluation of the Role of Devulcanized Rubber on the Thermo-mechanical Properties of Polystyrene

In this paper, different amounts of both devulcanized rubber (DR) and non-devulcanized rubber (NDR) were melt compounded and compression moulded with a brittle thermoplastic matrix such as polystyrene (PS). Scanning electron microscopy observations of the prepared blends showed that the PS/rubber interfacial adhesion, although rather limited, was improved in the case of DR, and that DR domains within the PS matrix had a lower size than NDR particles. Thermogravimetric analysis highlighted that the onset degradation temperature decreased upon the addition of rubber, and the maximum mass loss rate temperature increased. Differential scanning calorimetry tests showed that the glass transition temperature slightly decreased upon addition of DR and NDR. This increase also enhanced the maximum service temperature determined by measuring the Vicat grade. The surface hardness, the tensile modulus and stress at break were negatively affected when recycled rubber was added, because of the limited compatibility between PS and rubber particles and the relatively large size of the rubber domains. A notable increase in material ductility, with an enhancement of the tensile strain at break and of the impact resistance, was detected at elevated rubber amounts. Quite interestingly, mechanical properties of the blends with DR were systematically higher than those of the corresponding blends with NDR.

The effect of polylactic acid (PLA)/poly‐d‐lactidestereocomplex on the thermal and mechanical properties of various PLA/rubber blends

AbstractThis study investigated the effect of polylactic acid (PLA)/poly‐d‐lactide (PDLA) stereocomplex (ST) on the improvement of the mechanical and thermal properties of various rubber‐toughened PLAs. In this work, natural rubber (NR), synthetic polyisoprene rubber (IR), silicone rubber (SI), acrylic rubber (ACM), acrylic core–shell rubber (CSR), thermoplastic copolyester (TPE) and thermoplastic polyurethane (TPU) were chosen as the toughening agents. 5 wt% PDLA was melt‐blended with PLA to form ST crystals in the presence of 15 wt% rubber in an internal mixer at 180 °C and 50 rpm. It was found that the melting temperature of ST crystal (Tm,sc) and the impact strength of ST/rubber blends were strongly correlated with the rubber domain size. For the blends of ST with compatible rubbers (ACM, CSR, TPE and TPU), the rubber domain sizes tended to be smaller with higher Tm,sc and higher impact strength than the blends with incompatible rubbers (NR, IR and SI). However, the presence of ST crystals in PLA/incompatible rubber blends, especially the blends with NR and IR, led to a significant increase in the rubber domain size and plunges in tensile toughness and impact strength. On the other hand, the presence of these crystals in PLA/compatible blends did not change the rubber size or the impact strength significantly compared with those without ST crystals except in the case of ST/ACM, which resulted in a large increase in the impact strength. Among all rubber types, CSR provided the highest impact strength for both the PLA and ST systems. © 2019 Society of Chemical Industry

A facile fabrication of polypropylene composites with excellent low-temperature toughness through tuning interfacial area between matrix and rubber dispersion by silica nanoparticles located at the interface

In order to fabricate super low-temperature tough polymer composites which can withstand extreme environments, hydrophobic silica nanoparticles were incorporated into polypropylene/ethylene propylene rubber (PP/EPR) blends with the hope to tailor the brittle ductile transition temperature (Tbd). Compared with PP/EPR blends, PP/EPR/SiO2 composites presented much lower Tbd, and Tbd decreased with the increase of EPR content and SiO2 content. It was found that PP/EPR/SiO2 composites could present excellent low-temperature toughness with little rigidity loss. Phase morphology showed that the silica nanoparticles were located at the interface of PP and EPR. It was found that silica nanoparticles at the interface could not only suppress the phase coarsening in PP/EPR/SiO2 composites greatly, but also tailor the shape of rubber particles. A detailed investigation on rubber particle size, interparticle distance and interfacial area indicated that the tremendous drop of Tbd should be ascribed to the increased interfacial area between the matrix and rubber phase due to the decreased size and more irregular shape of rubber particles. As a result, a quantitative correlation between Tbd and interfacial area in PP/EPR/SiO2 composites was established. This study provided a facile approach to fabricate polymer composites with super low-temperature toughness or other functions through tuning the size and shape of rubber domains by adding nanoparticles.

The Effect of Dynamic Vulcanization on the Mechanical and Thermal Properties of Stereocomplex PLLA/PDLA/rubber Blends

This study investigated the influence of dynamic vulcanization of sterecomplex PLA/PDLA (ST) containing various types of rubbers by using dicumyl peroxide (DCP) as a vulcanizing agent. In this work, natural rubber (NR), isoprene rubber (IR), silicone rubber (SI), acrylic rubber (AR), thermoplastic copolyester (TPE) and thermoplastic polyurethane (TPU) were selected. Here, 5 wt% of PDLA, 15 wt% of rubber and 2 wt% DCP as an initiator were melt-blended with PLA in an internal mixer at 180 0C and 50 rpm. It was found that the addition of DCP in (NR and IR) led to a significantly increase in the impact strength and % elongation at break. On the other hand, for the rubbers that do not have double bonds in the main chain (SI, AR, TPE and TPU), the addition of DCP led to a decrease in impact strength and % elongation at break compare to the case without DCP due to the lack of double bonds to react with DCP. For the effect of DCP on the rubber dispersion, it was found that the addition of DCP on the NR and IR could improve the interface compatibility of the rubber and PLA leading to smaller average rubber domain sizes than without DCP. For other types of rubbers, the average rubber domain sizes were bigger with poorer interface compatibility than without DCP. For the effect of DCP on the crystallinity, it was found that the addition of DCP could increase the crystal density and could consequently reduce the crystal sizes of the ST/rubber blends.