Laboratory Internal Mixer Research Articles

Investigation of physico-mechanical, thermal, morphological, and antibacterial effects of bio-based epoxidized soybean oil plasticizer on PLA-ZnO nanocomposites as flexible food packaging

Polylactic acid (PLA) has attracted considerable attention because of its excellent properties compared to petroleum-based materials. However, improving its toughness, crystallization, and functionalities is challenging. Using a laboratory internal batch mixer, we produced unique blended nanocomposites comprising polylactic acid (PLA) as the host matrix, epoxidized soybean oil (ESO) as the plasticizer, and zinc oxide nanoparticles (ZnO NPs) as the reinforcements. The SEM-EDS test showed that neat PLA had a smooth surface, but the PLA-ZnO nanocomposite had rough micrographs and a uniform dispersion state of the nanoparticles. It was also found that adding ESO to the blend nanocomposites created a matrix droplet structure, and the size of the oil domains decreased as the ZnO content increased. All results derived from FTIR, XRD, and DSC tests were consistent with the morphological features in which ZnO NPs acted as the blend’s compatibilizer and heterogeneous nucleating agent. Our team observed that adding ESO decreased the PLA-ZnO nanocomposites’ glass transition temperature (Tg) by an average of 2 °C and increased the crystallization rate. It was also confirmed that the presence of ESO improved the flexibility and reduced the strength of the PLA. The tensile strength was further enhanced by incorporating ZnO into the blend. Adding 5 wt% of ZnO NPs increased the tensile strength of the PLA containing 10 wt% ESO by approximately 3.5 MPa. Furthermore, the tensile modulus was predicted using theoretical models; for example, the Paul model fitted with experimental findings. The addition of ESO increased the overall surface free energy of the nanocomposites. On the other hand, increasing ZnO content resulted in high contact angles and antibacterial properties of the blended nanocomposites. The favorable characteristics of the resulting films emphasized the potential use of these nanocomposite films as a promising choice for food packaging materials.

Synthesis and characterization of barium titanate nanoplatelets/polyvinylidene fluoride nanocomposite for piezoelectric properties

AbstractBarium titanate (BaTiO3) nanostructures with a tetragonal structure have unique mechanical and piezoelectric properties. BaTiO3 nanoplatelets (BTNPs) were synthesized via the precipitation of the hydroxide (Ba‐Ti‐OH) precursor, which was subsequently subjected to hydrothermal treatment. Polyvinylidene fluoride (PVDF) granules and BTNPs powder were compounded through melt‐mixing within a laboratory internal mixer to PVDF/BTNP nanocomposite. The dispersion of BTNPs were analyzed using FE‐SEM images. The examination of the polycrystalline structure of a PVDF/BTNP nanocomposite involved the utilization of FTIR, DSC, and XRD measurements. Further, the tensile test was carried out to study the mechanical properties of the nanocomposites. The piezoelectric tests showed that the PVDF nanocomposite with 10 wt.% of BTNP exhibited the highest output voltage and current due to its maximum crystallinity. The measured current increased from 0.03 μA for PVDF to 0.22 μA for PVDF/BTNP nanocomposite and further to 0.34 after polling. PVDF's piezoelectric properties experienced an 11‐fold enhancement due to alterations in its crystalline structure. Power density improved by 644% (7.5 times), and piezoelectric sensitivity rose by 173%. Consequently, the PVDF/BTNP nanocomposite demonstrates significant potential for applications in electronics and energy harvesting.Highlights Unique Tetragonal nanoplatelets produced via controlled BTNP synthesis. 10% BTNP enhances nanocomposite crystallinity by 22.7% PVDF‐10 displays increase in both voltage and current, enhancing piezoelectricity. Nanocomposites show promise for energy and electronics.

Influence of Processing Oil Content on Rubber-Filler Interactions in Silica/Carbon Black-Filled Natural Rubber Compounding

To ensure the production of high-quality rubber products, establishing effective compatibility and robusting interactions between rubber and fillers is crucial. Since the rubber production industry faces significant environmental challenges, sustainability is becoming a necessity in the rubber business. Various materials, such as the presence of processing aids, might influence rubber-filler and filler-filler interactions. Petroleum oil as general processing oil has environmental issues, thus it is urgent to replace it with bio-based oil. This study addresses these concerns by investigating the impact of paraffinic oil and bio-based oil content on the interactions between silica/carbon black and natural rubber chains. Ranging from 0 to 10 phr, different dosages of these oils were employed. The rubber compound underwent milling using two rolled laboratory open mills post-blending with a laboratory internal mixer. Subsequently, mechanical properties were assessed. A Rubber Processing Analyzer was utilized to characterize interactions between uncured and cured silica/carbon black-filled natural rubber blends. The results revealed that all variations were distributed uniformly. Tan Delta results confirm that a chemical with a high bio-based oil concentration is easier to process. The carbon black with the largest peak of modulus values at low strain has the highest reinforcing or the poorest dispersion. Compounding with paraffinic oil has a high peak modulus value, resulting in poor dispersion when compared to bio-based oil. This research sheds light on the potential of bio-based oils as an eco-friendly alternative in rubber processing, contributing to sustainability efforts in the industry.

Crystallization kinetics modeling, thermal properties and biodegradability of poly (ε-caprolactone)/niobium pentoxide and alumina compounds

Biocomposites based on poly (caprolactone) (PCL) incorporating different contents of niobium pentoxide (Nb2O5) and alumina (Al2O3) were prepared in a laboratory internal mixer. The thermal properties, biodegradability and non-isothermal crystallization kinetics modeling of the composites were investigated. Crystallization kinetics were analyzed using the methods of Pseudo-Avrami and Mo models with cooling rates of 2, 4, 8 and 16 °C/min, and the results indicated that the models described well the non-isothermal crystallization kinetics of the tested samples. The addition of oxides leads to a slight increase in the thermal stability of the polymeric matrix, either with alumina or niobium pentoxide and regardless of concentration, delaying the degradation process. The melting temperature tends to remain constant regardless of the increase in the heating rate or content of niobium pentoxide or alumina present, indicating that the melting temperature does not appear to be affected by these parameters. The presence of the fillers accelerates the biodegradation of the PCL matrix in the composites and this effect becomes more evident with the increase in the filler content, and more for alumina than niobium pentoxide.

The role of multiwall carbon nanotubes on physical, mechanical and rheological properties of poly(lactic acid)/natural rubber/CNT hybrid systems

The main objective of the present work was to study the role of carbon nanotube (CNT) on the microstructure development and physical, mechanical, and rheological properties of poly(lactic acid) (PLA)/natural rubber (NR)/CNT hybrid nanocomposites. The PLA/NR blend samples with constant blend ratio (90/10) were prepared by melt mixing in a laboratory internal mixer at a temperature of 190°C. The behavior of the PLA/NR blend was examined depending on the CNT content (0.5–6 wt%). The droplet size and droplet size distribution of the NR phase decreases with the increase in CNTs content. This could be explained in terms of compatibilizing effect of CNT and the changing of the viscosity ratio of the blend phases. The development of the microstructure and the physical properties of the blend were also investigated according to the CNT contents by measuring the linear viscoelasticity. The elongational behavior and mechanical properties of the blends were strongly dependent on the location of the CNT. The CNT worked as an efficient compatibilizer and also it worked as a reinforcing filler making the matrix more rigid.

Crystallization behavior of polycaprolactone/babassu compounds

Polycaprolactone/babassu compounds were prepared in a laboratory internal mixer, their melt crystallization behavior was investigated using a differential scanning calorimeter, and their kinetics was correlated using the Pseudo-Avrami model, with cooling rates ranging from 2.5 to 15 °C min−1. Babassu filler did not affect significantly crystallization parameters, with maximum differences of 1.2 K in temperature and 3% in crystallinity, within experimental uncertainty. Regarding Pseudo-Avrami parameters, data were correlated for the interval 5–95% conversion, which seems to be appropriate for processing applications; the uncertainty associated with Pseudo-Avrami individual parameters is less than 1%, whereas the “rate parameter” K was found to be well represented by a quadratic function.

Polycaprolactone (PCL)/alumina and PCL/niobium pentoxide composites: Rheology, crystallization, and mechanical properties

AbstractPolymeric polycaprolactone (PCL) matrix composites reinforced with alumina and niobium pentoxide were prepared in a laboratory internal mixer and studied by differential scanning calorimetry (DSC), tensile and impact tests, in addition to the particle distribution in the matrix. The objective of this study was to evaluate the influence of the oxide content on the rheology, crystallization, and mechanical properties of these composites. According to the rheological analysis, the composites were well mixed and the polymer matrix used in the composites can be considered thermally stable during processing. The effect of the fillers on degradation during processing was minimal. DSC analyses indicate that, in general, the increase in the filler content does not change the crystallization temperature, irrespectively of the oxide added. For the niobium pentoxide composites, crystallinity does not appear to be affected by an increase in filler content or cooling rate. Both tensile strength and elongation at break decreased with filler addition while impact strength decreased and Young's modulus was apparently unaffected. There was good distribution of the oxide particles in the polymer matrix.

HDPE/Chitosan Composites Modified with PE-g-MA. Thermal, Morphological and Antibacterial Analysis.

In this work, composites of high density polyethylene (HDPE) with chitosan were prepared by melt compounding in a laboratory internal mixer. Maleic anhydride grafted HDPE (PE-g-MA) in a concentration up to 25 phr was used as a compatibilizer to enhance the dispersing effect of chitosan in the HDPE matrix. The degree of crystallinity was investigated by X-ray diffraction (XRD) and the thermal properties were analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TG). The morphology was investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The integrity of composites was evaluated by mechanical properties and antibacterial properties were assessed against Escherichia coli (DH5a). Neither crystallinity nor HDPE’s melting parameters changed upon addition of chitosan and PE-g-MA. Chitosan aggregates were observed, which were dispersed upon addition of PE-g-MA, which also provided improved mechanical performance. Chitosan significantly improved the bacteriostatic effect of HDPE compounds preventing bacteria to colonize thus reducing the number of viable colony-forming units (CFU). This study revealed that HDPE/chitosan composites could be obtained by melt compounding, at lower cost and additionally having antibacterial properties, which might provide a new formulation option for developing antimicrobial film for food packaging.

Effect of filler type on properties of PBAT/organoclay nanocomposites

The goal of this study is to evaluate the effect of different organoclays on the properties of poly(butylene adipate-co-terephthalate) (PBAT)/organoclay systems. PBAT/organoclay nanocomposites containing 2.5, 5.0 and 7.5% of three different commercial organically modified clays (Cloisite® C10A, C20A and C30B) were prepared as a masterbatch in a laboratory internal mixer, let down to the appropriate concentration in a co-rotating twin-screw extruder, and test specimens were injection molded. Nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry (TGA) and dynamic mechanical analysis (DMA) as a function of clay identity and content. XRD results showed a significant increase in the interlayer spacing of the clay, suggesting that intercalated structures were obtained with all systems investigated, as confirmed by TEM. Organoclay incorporation into PBAT resulted in lower melt crystallization temperatures compared with the neat polymer, particularly in PBAT/C30B nanocomposites, slightly improved thermal stability, increased stiffness and no changes in the glass transition temperature. Compounding PBAT with up to 7.5% of C10A, C20A or C30B organoclays is an option to improve the performance of PBAT.

Crystallization kinetics of poly (butylene adipate terephthalate) in biocomposite with coconut fiber

ABSTRACT The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

Polycaprolactone matrix composites reinforced with brown coir: Rheological, crystallization, and mechanical behavior

Polycaprolactone matrix composites reinforced with natural and chemically treated coir were prepared in a laboratory internal mixer and studied by differential scanning calorimetry (DSC) and tensile tests. The aim of this work was to evaluate the influence of the filler and its surface modification on the rheological, mechanical, and crystallization behaviors of the composites. According to rheological analysis, the higher the filler content, the higher the viscosity of the material and the lower its local pseudoplasticity index. DSC analyses showed that the presence of coir anticipates the crystallization process; however, it does not affect the absolute crystallinity of the matrix. Mechanical tests indicated that an increase in filler content leads to an increase in Young's modulus and a decrease in the elongation at break. Additionally, composites with filler content from 20% can stand higher tensile stress than the neat polymer, and this effect is intensified by the surface modification applied to the filler. POLYM. COMPOS., 40:E678–E686, 2019. © 2018 Society of Plastics Engineers

Effect of heat cycling on melting and crystallization of PHB/TiO2 compounds

Compounds of poly(3-hydroxybutyrate) (PHB) and titanium dioxide (TiO2) with filler content between 1% and 10% were prepared in a laboratory internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/TiO2 compounds was investigated by differential scanning calorimetry (DSC). Melt and cold crystallization rates rise with increasing cooling/heating rates. A higher cooling rate translates to a lower melt crystallization temperature, while a higher heating rate results in a higher cold crystallization temperature. TiO2 promotes melt crystallization of PHB, behaving as a nucleant agent. The total crystallinity developed after melt and cold crystallization decreases for low levels of TiO2, i.e. 2% per weight, and is almost independent of the heating/cooling rate. The melting temperatures and rates are minimally affected by both the heating rate and filler content. The results suggest that the desired PHB microstructure can be controlled by filler content and adjusted heating/cooling rate.

HDPE/Chitosan Blends Modified with Organobentonite Synthesized with Quaternary Ammonium Salt Impregnated Chitosan.

In this study, blends based on a high density polyethylene (HDPE) and chitosan (CS) were successfully prepared by melt processing, in a laboratory internal mixer. The CS biopolymer content effect (up to maximum of 40%), and, the addition of bentonite clay modified with quaternary ammonium salt (CTAB) impregnated chitosan as a compatibilizing agent, on the properties of the blends was analyzed by Fourier transform-infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile strength, and scanning electron microscopy (SEM). The use of clay modified with CTAB impregnated chitosan, employing a method developed here, improved the compatibility of HDPE with chitosan, and therefore the thermal and some of the mechanical properties were enhanced, making HDPE/chitosan blends suitable candidates for food packaging. It was possible to obtain products of synthetic polymer, HDPE, with natural polymer, chitosan, using a method very used industrially, with acceptable and more friendly properties to the environment, when compared to conventional synthetic polymers. In addition, due to the possibility of impregnated chitosan with quaternary ammonium salt exhibit higher antibacterial activity than neat chitosan, the HDPE/chitosan/organobentonite blends may be potentially applied in food containers to favor the preservation of food for a longer time in comparison to conventional materials.

An Investigation of the Effect of Taurit Filling of Rubber Mixes for the Coating of Radial Lorry Tyre Breakers

The results of investigating the effect of the shungite analogue Taurit (grade TSD) on the properties (measured on an RPA 2000 instrument) of a breaker rubber mix and of a rubber compound based on synthetic isoprene rubber SKI-3 are set out. Different methods of introducing Taurit have been tested: 10 parts into the rubber at the stage of its production; 10 parts into the standard rubber mix at the first stage of mixing; 10 parts into the rubber subjected to preliminary mechanical plasticisation in a laboratory internal mixer at a temperature of 100°C. The introduction of Taurit into the rubber in small quantities in order to reduce the proportion of rubber constituent in the rubber mix has also been tested. The test results have been compared with results for standard rubber mixes and rubber compounds. When Taurit is introduced into rubber at the stage of its production, the cohesive strength of the rubber mix and the rate of its vulcanisation and also the dynamic modulus components G′ and G″ are increased. When Taurit is introduced into plasticised rubber, again G′ and G″ are increased, there is an increase in plasticity, and the elastic recovery of the rubber mix is reduced. The breaker rubber compound from this mix has the best adhesion to metal cord and the highest dynamic strength. Data on the Payne effect indicate a better carbon black particle distribution when Taurit is introduced into the rubber at the stage of its production. Reduction in the proportion of rubber constituent in the rubber mix leads to a deterioration in the carbon black particle distribution.

Nonisothermal crystallization studies of PBT/ZnO compounds

Compounds of poly(butylene terephthalate) (PBT) and zinc oxide (ZnO) with filler content between 1 and 10% were prepared in a laboratory internal mixer. The processing parameters did not damage PBT thermal stability or its molecular weight as evidenced by torque rheology. The melt crystallization of PBT/ZnO compounds was investigated by differential scanning calorimetry and their morphology by scanning electron microscopy and optical microscopy. From morphological analyses, ZnO particles are well dispersed in PBT matrix, which crystallizes in typical spherulites. The melt crystallization temperatures and maximum melt crystallization rates are almost unaffected by the filler. Equally the overall crystallinity did not show any dependence on the filler content or the cooling rate. Mo’s model was found to be suitable for a description of the melt crystallization kinetics, while Ozawa model turned out to be inadequate.

Melting and crystallization of PHB/ZnO compounds

Compounds of poly(3-hydroxybutyrate) (PHB) and zinc oxide with filler content between 1 and 10% were prepared in a laboratory internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/ZnO compounds was investigated by differential scanning calorimetry. Physical aspects of the compounds were examined by means of scanning electron microscopy and optical microscopy. Melt and cold crystallization rates rise with increasing cooling/heating rates. The melt crystallization temperatures and maximum melt crystallization rates are almost unaffected by the filler, independent on the filler concentration. The main effect of ZnO on PHB is to reduce the overall crystallinity obtained after a successive melt and cold crystallization events. For defined filler content, Mo model can be applied for the description of tested and untested heating/cooling rates, provided that a lower accuracy is acceptable.

Comparative study of the effect of TiO2 and ZnO on the crystallization of PHB

ABSTRACT PHB/TiO2 and PHB/ZnO compounds were prepared in a laboratory internal mixer. Crystallization was investigated by differential scanning calorimetry (DSC) with heating and cooling rates ranging from 5 to 30 °C/min. Fractured surface of selected samples was analysed by scanning electron microscopy (SEM). From the SEM images, it was observed that ZnO and TiO2 nanoparticles were properly dispersed in the PHB matrix. DSC studies revealed that the addition of TiO2 and ZnO changed the temperature and crystallization rate but did not affect the total crystallinity significantly. In general, TiO2 behaved as nucleating agent greatly influencing the PHB crystallization.

PHB/Bentonite Compounds. Effect of Clay Modification and Thermal Aging on Properties

Poly(3-hydroxybutyrate) (PHB) was compounded with three different Bentonite clays: natural, purified by ultrasound/sonicated and organically modified with hexadecyltrimethylammonium bromide. PHB/Bentonite masterbatches with 30% clay were prepared in a laboratory internal mixer and letdown with pure matrix to 1% and 3% w/w clay. Test samples were injection molded and characterized by x-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Increase in Bentonite hydrophobic character was evinced by FTIR for organoclays. XRD of composites showed increase in clay interlayer distance and peak broadening, suggesting formation of intercalated nanocomposites. DSC showed increase in crystallinity and crystallization rate for compounds, especially for PHB/organoclay formulations. Thermal aging was conducted by exposing specimens at 115oC for up to 120 hours, and mechanical properties were measured according to ASTM standards. Elastic modulus increased and impact strength decreased with time and clay content; clay purification had little effect on the tensile properties. Tensile strength of thermal aged samples showed little variation, except for the organoclay nanocomposites, for which it significantly decreased with exposure time. SEM images displayed a whitened honeycomb structure and detachment of PHB/Bentonite layers which may be connected to cold crystallization and degradation processes taking place during thermal aging.Keywords:

PBAT/organoclay composite films: preparation and properties

Environmental problems caused by the increased waste associated with short-term use of plastic materials, particularly by the food packaging industry, prompted the search for biodegradable alternatives. This contribution studied one of these alternatives, poly(butylene adipate-co-terephthalate)—PBAT, a polymer that is fully biodegradable in common landfills, compounded with a small amount of Cloisite 20A organoclay. Materials were mixed in a laboratory internal mixer and films prepared in a chill roll extruder. Results show that the presence of organoclay does not increase degradation of the polymer matrix during processing, nor affects its crystallization characteristics. However, organoclay addition significantly diminished oxygen and carbon dioxide permeability of the films, making them a very interesting alternative for the food packaging industry.

Rheological properties of HDPE/chitosan composites modified with PE-g-MA

Abstract