Protein/glycerol blends and injection‐molded bioplastic matrices: Soybean versus egg albumen

Two well‐known proteins have been selected in order to produce bioplastics through injection molding: a soy protein isolate (SPI) and an egg white albumen concentrate (EW). Each of them has been thoroughly mixed with glycerol (40 wt %) and the blend then obtained have been characterized by means of rheological and thermomechanical techniques, which allowed the optimization of the processing moulding conditions (cylinder temperature, 60°C–65°C; mould temperature, 120°C; post‐injection pressure, 500–600 bars). Once bioplastics were obtained, their thermomechanical and tensile properties, as well as their water uptake capacity and transparency were evaluated. Bioplastics containing EW showed higher values in the elastic and loss moduli, E′ and E″, from ?30°C to 130°C, than the corresponding SPI bioplastic. However, they both showed qualitatively the same evolution with temperature, where E′ and E″ decreased up to a plateau at high temperatures. When examining their tensile and water uptake properties is found that SPI bioplastics are more ductile and present enhanced water uptake behavior over EW bioplastics, which on the other hand possess higher Young's modulus. SPI seems to provide tougher bioplastics, being an excellent option for potential superabsorbent applications, whereas EW would suit for those applications requiring higher mechanical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42980.     

Thermomechanical properties and water uptake capacity of soy protein‐based bioplastics processed by injection molding

The optimization of the processing conditions in the production of soy protein bioplastics by injection molding has been essential in order to develop materials with a great capacity to absorb water while displaying good mechanical properties. Using a 50/50 (wt/wt) soy protein/glycerol mixture, and 40 °C, 500 bar, and 70 °C as reference values for cylinder temperature, injection pressure, and mold temperature, respectively, the effect of those processing parameters over thermomechanical and hydrophilic properties was studied. Processing parameters did not show a great influence over the thermomechanical bending properties within temperatures ranging from ?30 to 130 °C, as most samples displayed a similar response, independently of the parameter studied. On the other hand, when studying tensile and hydrophilic properties, the main effect corresponded to the cylinder and mold temperature values, as pressure did not exert a clear influence when increased from 300 to 900 bar. Samples with a lower water uptake were obtained when processed at higher temperature, as a result of crosslinking promotion. Moreover, a greater extensibility was observed when bioplastics are processed at high mold temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43524.     

Recycling of wood fiber‐reinforced HDPE by multiple reprocessing

The mechanical recycling of high‐density polyethylene (HDPE) reinforced with wood fiber was studied by means of repeated injection moulding. The change in properties during the recycling was monitored by tensile and flexural tests, Charpy impact tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FTIR spectroscopy, and by measuring the fiber lengths. Tests were also done where injection moulding was combined with subsequent accelerated thermo‐oxidative ageing and thereafter repeated numerous times. The results showed that the HDPE composites were relatively stable toward both the ageing conditions and the repeated injection moulding. The change of the mechanical properties was mainly observed as an increased elongation at max. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43877.     

Comparison between pea and soy protein-based bioplastics obtained by injection molding

The elaboration of bioplastics from renewable polymers (e.g., proteins) is a field with great potential for industrial applications such as food packaging and agriculture. This study evaluates the development of bioplastic systems by injection molding using two different raw materials: soy protein isolate (SPI) and pea protein isolate (PPI). Both proteins are by-products, which lowers the price of processed bioplastics. However, it is necessary to control their properties during the manufacture processing, in order to ensure that they can replace conventional plastics. Therefore, the main objective of this work was to compare the properties of SPI and PPI bioplastics processed at different injection times (150, 300, and 450 s) and different mold temperatures (70 and 130°C). Thus, mechanical properties, water uptake capacity, and transparency were evaluated. The results show the potential of these raw materials to produce bioplastics that can replace conventional plastics, and that the processing conditions can be modified to obtain the desired final properties.     

Thermal and mechanical properties of nanocomposites based on a PLLA‐b‐PEO‐b‐PLLA triblock copolymer and nanohydroxyapatite

Composites which combine biocompatible polymers and hydroxyapatite are unique materials with regards to their mechanical properties and bioactivity in the development of temporary bone‐fixation devices. Nanocomposites based on a biocompatible and amphiphilic triblock copolymer of poly(l‐ lactide) (PLLA) and poly(ethylene oxide) (PEO) —PLLA‐b‐PEO‐b‐PLLA— and neat (nHAp) or PEO‐modified (nHAp@PEO) hydroxyapatite nanoparticles were prepared by dispersion in benzene solutions, followed by freeze‐drying and injection moulding processes. The morphology of the copolymers of a PEO block dispersed throughout a PLLA matrix was not changed with addition of the nanofillers. The nHAp particles were spherical and, after modification, the nHAp@PEO nanoparticles were partially agglomerated. In the nanocomposites, these particles characteristics remained unchanged, and the nHAp particles and nHAp@PEO agglomerates were uniformly dispersed through the copolymer matrix. These particles acted as nucleating agents, with nHAp@PEO being more efficient. The incorporation of nHAp increased both the reduced elastic modulus (～22%) and the indentation hardness (～15%) in comparison to the copolymer matrix, as determined by nanoindentation tests, while nHAp@PEO addition resulted in lower increments of these mechanical parameters. The incorporation of untreated nHAp was, therefore, more beneficial with regards to the mechanical properties, since the amphiphilic PLLA‐b‐PEO‐b‐PLLA matrix was already efficient for nHAp nanoparticles dispersion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44187.     

Novel biocomposites based on wheat gluten and rubber wood sawdust

Rubber wood sawdust (RWS) was used as a reinforcement for wheat gluten based bioplastics. The RWS content was varied from 0, 5, 10, 15–20 wt %. Effects of the RWS content on the morphology, water absorption, mechanical, thermal, and biodegradation properties of the wheat gluten based bioplastic were investigated. An addition of RWS caused an improvement of the tensile strength and water resistance of the wheat gluten based bioplastics. Scanning electron micrograph of the wheat gluten/RWS composites with a 10 wt % of RWS revealed a good dispersion and uniform embedding of the RWS within the wheat gluten matrix. Agglomeration of RWS was observed when the RWS loads were increased (15 and 20 wt %). The biodegradation process of the composites depended on the amount of RWS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43705.     

Cassava starch‐based nanocomposites reinforced with cellulose nanofibers extracted from sisal

Cellulose nanofibers were extracted from sisal and incorporated at different concentrations (0–5%) into cassava starch to produce nanocomposites. Films' morphology, thickness, transparency, swelling degree in water, water vapor permeability (WVP) as well as thermal and mechanical properties were studied. Cellulose nanofiber addition affected neither thickness (56.637 ± 2.939 µm) nor transparency (2.97 ± 1.07 mm^?1). WVP was reduced until a cellulose nanofiber content of 3.44%. Tensile force was increased up to a nanocellulose concentration of 3.25%. Elongation was decreased linearly upon cellulose nanofiber addition. Among all films, the greatest Young's modulus was 2.2 GPa. Cellulose nanofibers were found to reduce the onset temperature of thermal degradation, although melting temperature and enthalpy were higher for the nanocomposites. Because cellulose nanofibers were able to improve key properties of the films, the results obtained here can pave the route for the development and large‐scale production of novel biodegradable packaging materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44637.     

Toughening of polylactic acid using styrene ethylene butylene styrene: Mechanical,thermal, and morphological studies

Polylactic acid, PLA, derived from renewable resources has gained great attention nowadays owing to their sustainability, biodegradability, superior property, and transparency. However, intrinsic brittleness and low toughness severely limits its variety of applications. Blending of PLA with other polymers is more economical and more flexible technique for the property improvement of PLA. In this study, Styrene Ethylene Butylene Styrene (SEBS) and Maleic Anhydride grafted SEBS (MA‐g‐SEBS) are used as toughening agents to study their effect for its toughness, high strength and heat resistance on PLA. PLA/SEBS and PLA/Maleic Anhydride grafted SEBS blends were prepared under four different compositions by melt mixing technique using a corotating twin–screw extruder after optimizing the mixing conditions. The mechanical properties of the blends such as tensile, flexural, and impact strengths were investigated using specimens prepared by injection molding process. The percentage elongation and impact strength of PLA/MA‐g‐SEBS blends were found to be increased significantly by 540 and 135%, respectively in comparison with virgin PLA and PLA/SEBS blends. However, tensile strength and modulus of PLA/SEBS and PLA/MA‐g‐SEBS blends decreased compared with pristine PLA. SEM behaviour supported the higher impact property of PLA with the incorporation of modified SEBS via multiple crazing and cavitation mechanisms. DSC study also supported greater compatibility between maleated SEBS and PLA. POLYM. ENG. SCI., 56:669–675, 2016. © 2016 Society of Plastics Engineers     

Preparation,physical, and mechanical properties of soy protein isolate/guar gum composite films prepared by solution casting

Guar gum (GG) was incorporated into soy protein isolate (SPI) films using a blending solution casting method to form SPI/GG composite films. The effects of SPI and GG contents on the transparency, water susceptibility, mechanical, and gas‐barrier properties of SPI/GG composite films were analyzed. The results showed that SPI/GG composite films with added GG were much more tensile‐resistant, water‐resistant, gas‐barrier properties but less deformable property than SPI control film. The presence of GG also improved film barrier to the light. The analysis results of contact angle measurement, Fourier transform infrared spectroscopy, and scanning electron microscope indicated that GG induced increased network compactness of the composite films which resulted from strong intermolecular interactions, such as hydrogen bonding, that existed between SPI and GG. Findings indicate that GG may be used as a natural means to improve specific properties of SPI films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43382.     

Gas assisted injection moulding: Finite element modelling and experimental validation

Abstract

Gas assisted injection moulding of a rectangular cross-section tensile test specimen has been modelled using a finite element implementation of the pseudo-concentration method, in which the velocity components and pres sure are interpolated as primitive variables. Two-dimensional and three- dimensional modelling formulations are presented and in each case wall thickness predictions are compared with actual measurements taken from specimens obtained from computer monitored gas assisted injection moulding production. Two different boundary conditions were used for the injection of gas into the cavity.

Initial mechanical testing is used to compare the apparent elastic modulus of the solid material in gas assisted injection moulding specimens with that in solid polymer specimens.     

ABS/HIPS blends obtained from WEEE: Influence of processing conditions and composition

The recycling of acrylonitrile–butadiene–styrene (ABS) and high‐impact polystyrene (HIPS) from postconsumer electronic equipment housing was investigated. A preliminary study of shot size and particle size effects on the mechanical properties of ABS/HIPS (50/50) blends obtained directly via injection molding was conducted. Injection‐molded specimens of ABS/HIPS blends, obtained at different compositions with or without previous extrusion, were subjected to mechanical, thermal, and morphological testing. Preliminary studies showed that a smaller particle size resulted in higher tensile and impact strength, regardless of the shot size used during injection molding. ABS/HIPS blends obtained using previous extrusion presented a slight increase in Young's modulus and a decrease in elongation at break and impact strength. The increase in glass‐transition temperature related to the Polybutadiene (PB) phases of these blends indicated a possible increase in crosslinking structures during extrusion. In addition, these blends showed a coarse and heterogeneous morphology, suggesting that ABS did not completely mix with HIPS. Compared to processing conditions, the blend composition appeared to have a much stronger effect on the mechanical properties. The results obtained suggest the possibility of obtaining ABS/HIPS blends directly via injection molding as long as small ground particles are used. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43831.     

In situ polarity functionalization and properties of styrenic triblock copolymers synthesized via RAFT emulsion polymerization

The in situ polarity functionalization of the styrenic triblock copolymers was accomplished via the block introduction of polar monomer, n‐butyl acrylate, with the help of reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization. The polarity functionalization, microphase separation, static and dynamic mechanical properties, water resistance, transparency, and thermal stability of the synthesized polarity‐functionalized triblock copolymers, polystyrene‐block‐poly(n‐butyl acrylate)‐block‐polystyrene (SAS), were extensively studied. The poly(n‐butyl acrylate) (PBA) middle block higher than 10 wt % has the favorable toughening effect on polystyrene (PSt) two‐end block due to the microphase separation in SAS. The glass transition of the continuous plastic phase (mainly composed of PSt block) has a much greater influence on the storage modulus than that of the dispersed rubber phase (mainly composed of PBA block). The polarity‐functionalized SAS has good water resistance, high transparency, and robust thermal stability. The polarity‐functionalized SAS will have such a potential application broadening as polar adhesive. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44603.     

The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer

In this work, the mechanical and failure behavior of injection molded aviation standard optical grade polycarbonate (PC) was investigated through uniaxial tensile testing. The effect of different injection molding process parameters including injection velocity, packing pressure, cooling time, mold temperature, and melt temperature were determined to observe their effect on yield and postyield behavior of PC. Out of these examined parameters, the mold and melt temperature show significant effect on mechanical behavior of studied polymer. The yield and flow stresses in polymer increase with the increase in mold and melt temperature during injection molding. However, other process parameters i.e., packing pressure, injection velocity, and cooling time showed little effect on mechanical performance of the polymer. The molded specimens were annealed at different temperatures and residence time to evaluate its effect on mechanical behavior and fracture morphology. The yield stress increases gradually with the increase in annealing temperature and time. The annealing treatment also changed the failure mode of PC specimens from ductile to brittle. In addition to process parameters, the effect of increased loading rate was also undertaken which shows substantial effect on mechanical and failure behavior of PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44474.     

Influence of the amorphous phase molecular mobility on impact and tensile properties of polyamide 6,6

In this work, the relationship between molecular mobility of polyamide 6,6 amorphous phase and mechanical properties is studied. PA66 formulations having different glass transition temperatures (T_g) obtained by additivation, chemical modification of the polyamide chains, and/or water conditioning at different hygrometry levels, are considered. The main emphasis is put on the impact strength, as measured by instrumented Charpy impact tests over a broad temperature range. It is observed that the brittle‐tough transition temperature T_B/T is closely correlated with the T_g of the samples rather than to the β secondary relaxation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43457.     

Effect of plasticizer and storage conditions on thermomechanical properties of albumen/tragacanth based bioplastics

The effects of composition of the plasticizer fraction and storage conditions on the physical and thermomechanical properties of egg albumen/tragacanth gum based bioplastics were studied. Thus, glycerol (G) and water (W) were used as plasticizers at different G/W ratios (1:0, 3:1, 1:1, 1:3, 0:1), keeping the biopolymer fraction always at 60% (w/w). Tragacanth gum was included in the formulation for its well-known hydrophilic character, as possible future applications of these bioplastics may be moisture dependent (e.g. modified atmosphere packaging). Moreover, properties of bioplastics stored at room temperature under no control of relative humidity were different of those obtained when bioplastics were equilibrated a 53% relative humidity (RH) atmosphere. This is reflected in the DMTA and tensile tests results, for which water loss in the samples with the highest water contents (1:3, 0:1) involves very significant increases in viscoelastic moduli and tensile strength when equilibrated at 53% RH. Glycerol presence when no RH control was taken promotes water uptake, probably due to an interaction between both plasticizers, which eventually lead to a greater plastic region in the tensile tests.     

Development of novel soy-protein-based superabsorbent matrixes through the addition of salts

The addition of salts, like sodium bicarbonate (SB) or carbonate (SC), into the formulation of bioplastic materials may alter their hydrophilic character to a significant extent. Soy protein isolate (SPI) is a byproduct of the soybean oil industry, which, when properly blended with glycerol (GL), can be further processed through a lab-scale injection molding device. A maximum in the water uptake around 2250 or 2500% is obtained for bioplastics obtained when either SB or SC content is around 1 wt %, respectively. Thus, they exceed the limit to be considered superabsorbent materials (SAMs). Regarding their mechanical properties, a higher presence of SB within the SPI/GL matrix provides materials with a higher extensibility and lower Young's modulus. A higher water uptake is observed after replacing SB for SC in the formulation, probably related to a higher alkalinization of the material as well as to the high hydrophilicity of the carbonate. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47012.     

Fabrication of coloured zirconia ceramics by infiltrating water debound injection moulded green body

Abstract

Abstract

The authors developed a new technique combining ceramic injection moulding and liquid precursor infiltration, presenting a new strategy for fabrication of coloured zirconia ceramics. The authors’ strategy includes ceramic injection moulding 3Y‐TZP powder using a water debinding binder system, debinding moulded parts in water and drying, immersing debound parts in solutions containing different colouring ions and then sintering and creating coloured zirconia ceramics. The fabricated coloured ceramic bars exhibit a core shell structure, and the thickness of the coloured shell can be tailored by adjusting immersion time and temperature. Using solutions containing different colouring ions, ceramic bars with various colours can be prepared.     

Preparation and property investigation of crosslinked alginate/silicon dioxide nanocomposite films

Crosslinked nanocomposite films of sodium alginate (SA) and silicon dioxide (SiO₂) with different SiO₂ loading values were prepared by in situ synthesis. Biocomposite films were produced by solution casting and solvent evaporation with glycerol as the plasticizer and calcium chloride as the crosslinking agent. The effects of the addition of nano silicon dioxide (nano‐SiO₂) in SA on the microstructural, physical, mechanical, and optical properties of the nanocomposite films were characterized. The results show that nano‐SiO₂ was dispersed homogeneously in the SA matrix; it thereby formed a strong interfacial interaction between the nano‐SiO₂ particles and the matrix. The transparency of the bionanocomposite films was enhanced. Thermogravimetric analysis also revealed that nano‐SiO₂ improved the thermal stability of the SA films. The incorporation of SiO₂ further reduced the water vapor permeability and swelling degree and significantly increased the tensile strength and elongation, which are parameters important for packaging industries. Finally, the lower light transmission of UV light from 200 to 250 nm indicated that SA/SiO₂ nanocomposite films could potentially be used to prevent lipid damage by UV light in food conservation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43489.     

Polymer ferroelectret based on polypropylene foam: Piezoelectric properties improvement using post‐processing thermomechanical treatment

In this work, the effect of post‐processing parameters (time, temperature, and pressure) on the morphology as well as mechanical and piezoelectric properties of foamed polypropylene (PP) films were studied. Two different post‐processing methods, based on the saturation of a foamed film with supercritical nitrogen (N₂), were used to obtain an optimized eye‐like cellular structure with a high cell aspect ratio (AR). The results showed that, when the PP‐foamed films were exposed to a gradual temperature and pressure increase, an appropriate cellular structure with high AR value (about 6.6) was obtained. This structure led to a high quasi‐static piezoelectric d₃₃ coefficient of 800 pC/N (45% higher than for untreated ones) indicating the importance of the post‐processing treatment on the piezoelectric behavior of these films. On the other hand, when the treatment was performed in steps, cell morphology changed from an eye‐like to a less elongated shape, resulting in lower d₃₃ values. The tensile characterization showed that higher cell aspect ratio led to lower Young's modulus, which is suitable to achieve higher piezoelectric properties. Finally, dynamic mechanical analysis (DMA) was used as a simple method to correlate mechanical and piezoelectric properties of cellular PP. This was done via the ratio of the storage moduli in the longitudinal and transverse directions, which is directly related to film anisotropy (AR value) and thus to the piezoelectric behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44577.     

Relevance of the acid–base approach in prediction of adhesion properties in two‐component injection moulding

We demonstrate the use of innovative wetting method in prediction of the adhesion properties of biobased polymers for two‐component injection moulding, taking into account the acid–base surface properties of joined materials. The measurements were carried out in accordance with modified Berger method by calculation of the difference in shortened acidity parameter ΔD_short between hard and soft component. Correlation factors up to 0.99 were observed between ΔD_short and peel force. In comparison to results obtained by conventional wetting methods, high potential for the selection of components with high interface adhesion and for prediction of the functionality by the acid–base approach was demonstrated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43048.