Poly(ethylene oxide)-coated granular starch-poly(hydroxybutyrate-co-hydroxyvalerate) composite materials

Granular cornstarch was coated with several biodegradable polymers in an effort to improve the mechanical properties of starch-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites. Only samples containing poly(ethylene oxide) (PEO)-coated granular starch showed a large improvement in tensile properties over uncoated starch. For example, a 50/50 blend of PEO-coated starch and PHBV had a tensile strength of 19 MPa and an ultimate elongation of 23%, compared to 10 MPa and 11% for a similar blend containing uncoated starch. PEO may act as an adhesive between the starch and the PHBV and/or increase the toughness and resistance to crack growth of PHBV around the starch granules.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Study of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/Bamboo Pulp Fiber Composites: Effects of Nucleation Agent and Compatibilizer

In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/bamboo pulp fiber (BPF) composites were prepared by melt compounding and injection molding. The crystallization ability, tensile strength and modulus, flexural strength and modulus, and impact strength were found substantially increased by the addition of BPF. Tensile and flexural elongations were also moderately increased at low fiber contents (<20%). BPF demonstrated not only higher strength and modulus, but also higher failure strain than the PHBV8 matrix. Boron nitride (BN) was also investigated as a nucleation agent for PHBV8 and maleic anhydride grafted PHBV8 (MA-PHBV8) as a compatibilizer for the composite system. BN was found to increase the overall properties of the neat polymer and the composites due to refined crystalline structures. MA-PHBV8 improved polymer/fiber interactions and therefore resulted in increased strength and modulus. However, the toughness of the composites was substantially reduced due to the hindrance to fiber pullout, a major energy dissipation source during the composite deformation.     

A Biobased Blend of Cellulose Diacetate with Starch

Two bio-based polymers, cellulose diacetate (CDA) and starch, were used to prepare blends with reasonable properties and low cost. Due to the poor processing properties, starch was modified in the presence of glycerol and epoxidized soybean oil (ESO), and CDA was plasticized by triacetin (TA) and ESO, respectively. The morphologies of the blends with different amounts of modified starch (MST) were studied by scanning electron microscope (SEM), and the physical properties of the blends, including thermal stability, mechanical property, water and moisture resistance, were investigated. The equilibrium moisture absorption rates of the blends containing 30 and 50 wt% MST at 100 % of relative humidity(RH) were 9.4 and 15.0 %, respectively. SEM and DMA results demonstrated that CDA and MST had a certain extent of compatibility. Due to the partial plasticization of starch, the tensile strength of the blends was nearly not affected by the amount of MST. Even if 50 wt% MST was added, the tensile strength of the blend was as high as 24.7 MPa. The obtained blend containing 30 wt% MST can keep good mechanical properties at 50 % RH, and its tensile strength and elongation at break are 30.2 MPa and 3.6 %, respectively. All the results show that the CDA/MST blends have a potential as an environmental friendly material.     

Grafting of Glycidyl Methacrylate onto Poly(lactide) and Properties of PLA/Starch Blends Compatibilized by the Grafted Copolymer

Poly(lactide)-graft-glycidyl methacrylate (PLA-g-GMA) copolymer was prepared by grafting GMA onto PLA in a batch mixer using benzoyl peroxide as an initiator. The graft content was determined with the ¹H-NMR spectroscopy by calculating the relative area of the characteristic peaks of PLA and GMA. The result shows that the graft content increases from 1.8 to 11.0 wt% as the GMA concentration in the feed varies from 5 to 20 wt%. The PLA/starch blends were prepared by the PLA-g-GMA copolymer as a compatibilizer, and the structure and properties of PLA/starch blends with or without the PLA-g-GMA copolymer were characterized by SEM, DSC, tensile test and medium resistance test. The result shows that the PLA/starch blends without the PLA-g-GMA copolymer show a poor interfacial adhesion and the starch granules are clearly observed, nevertheless the starch granules are better dispersed and covered by PLA when the PLA-g-GMA copolymer as a compatibilizer. The mechanical properties of the PLA/starch blends with the PLA-g-GMA copolymer are obviously improved, such as tensile strength at break increasing from 18.6 ± 3.8 MPa to 29.3 ± 5.8 MPa, tensile modulus from 510 ± 62 MPa to 901 ± 62 MPa and elongation at break from 1.8 ± 0.4 % to 3.4 ± 0.6 %, respectively, for without the PLA-g-GMA copolymer. In addition, the medium resistance of PLA/starch blends with the PLA-g-GMA copolymer was much better than PLA/starch blends.     

Novel Tough Crystalline Blends of Polylactide with Ethylene Glycol Derivative of POSS

Blending of polylactide (PLA) with low stereoregularity and polyhedral oligomeric silsesquioxane grafted with arms of poly(ethylene glycol) methyl ether, acting as a plasticizer, allowed us previously to obtain a novel stable elastomeric-like material. The present contribution focuses on the properties of semi-crystalline PLA plasticized with this compound. Melt blends of PLA with 5–15 wt% of the plasticizer, were compression molded, quenched and annealed, which enabled cold-crystallization. The glass transition temperature of the blends and their drawability depended on their crystallinity and plasticizer content. The best ductility was reached at the plasticizer content of 15 wt%; the achieved strain at break was 6.5 (650%) and 1.3 (130%), for the quenched and annealed material, respectively. The latter value exceeded 20 times the strain at break of neat crystalline PLA. The tensile toughness of the annealed 15 wt% blend was 12 times larger than that of crystalline PLA. Moreover, annealing of 15 wt% blend improved its yield strength by 40%. Despite the two peaks of the loss modulus, indicating the two glass transitions in this blend, no heterogeneities were found by scanning electron microscopy, indicating that the plasticizer enriched phase formed instead of distinct inclusions of the plasticizer.     

Comparison of the Effect of Plasticizers on PHBV—and Organoclay—Based Biodegradable Polymer Nanocomposites

The aim of this work was to evaluate the effect of different plasticizers on the morphology, crystallization, and mechanical properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/organomodified montmorillonite (OMt) nanocomposites. We investigated three different plasticizers: dioctyl phthalate (DOP), a commonly used additive in the polymer industry, and two natural and biodegradable plasticizers: epoxidized soybean oil (ESO) and triethyl citrate (TEC). The nanocomposites with 3 wt% OMt were obtained by melt processing in an internal mixer. The plasticizers were used alone or in combination with clay in a concentration of 10 wt%. X-ray diffraction and scanning electron microscopy results revealed a partially intercalated structure. The degree of crystallinity was higher for all of the samples compared to neat PHBV, although the melting temperature decreased with the use of plasticizers combined with OMt. The impact strength results were dependent on the interaction between the components of the system. Triethyl citrate was the most effective plasticizer due to its more pronounced interaction with the PHBV matrix, which yielded improvements in processing conditions and PHBV’s flexibility and impact properties.     

Injection Molded Biocomposites from Soy Protein Based Bioplastic and Short Industrial Hemp Fiber

Biocomposites from soy based bioplastic and chopped industrial hemp fiber were fabricated using twin-screw extrusion and injection molding process. Soy based bioplastics were prepared through cooking with plasticizer and blending with biodegradable poly(ester amide). Mechanical, thermal properties and fracture surface morphology of the “green”/biocomposites were evaluated with universal testing system (UTS), dynamic mechanical analysis (DMA), Environmental Scanning Electron Microscopy (ESEM). It was found that the tensile strength and modulus, flexural strength and modulus, impact strength and heat deflection temperature of industrial hemp fiber reinforced biocomposites significantly improved. The fracture surfaces showed no signs of matrix on the fiber surface suggesting poor interfacial adhesion.     

Preparation and Properties of Propylene Glycol Plasticized Wheat Protein Isolate Novel Green Films

Novel bio-based green films were prepared using wheat protein isolate (WPI) by solution casting method using Propylene Glycol as a plasticizer for packaging applications. The effect of the plasticizer content (10, 15, 20 and 25 wt%) on mechanical properties (tensile strength, young’s modulus and  % of elongation) was investigated. A thermal degradation and phase transition of the prepared WPI was assessed by means of TGA and DSC analysis. The results showed that the tensile strength and young’s modulus decreased and  % of elongation increased with increasing PG content. The ATR-FTIR and SEM were used for structural characterization and morphology of the films, respectively. FTIR studies reveals that the intensity of the bands corresponding to the amide groups increases with increasing PG content tending to increase protein–PG interactions. Further, the glass transition temperature was decreased and the thermal stability of the WPI was found to be increased by plasticization. The overall thermal stability of the films was improved and is attributed to the increase in mobility of the polymer chains.     

Mechanical Properties of Microcrystalline Cellulose (MCC) Filled Engineering Thermoplastic Composites

In this study, engineering thermoplastic composites were prepared from microcrystalline cellulose (MCC)-filled nylon 6. MCC were added to nylon 6 using melt mixing to produce compounded pellets. The MCC-filled nylon 6 composites with varying concentrations of MCC (from 2.5 to 30 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of MCC. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a MCC weight fraction of 20 %. The Izod impact strength of composites decreased with the incorporation of MCC without any surface treatments and coupling agent. This observation is quite expected for filled polymer systems and has been commonly observed. There was a strong correlation between density and tensile (r = 0.94) and flexural modulus of elasticity (r = 0.9). MCC filled composites manufactured by injection method had highly uniform density distribution through their thickness. The higher mechanical results with lower density demonstrate that MCC can be used as a sufficient reinforcing material for low cost, eco-friendly composites in the automotive industry especially for under-the-hood applications (engine covers, intake manifolds and radiator end tanks) as well as in other applications such as the building and construction industries, packaging, consumer products etc.     

Tensile Strength, Elongation, Hardness, and Tensile and Flexural Moduli of Injection-Molded TPS Filled with Glycerol-Plasticized DDGS

Continuing growth of biofuel industries is generating large amounts of coproducts such as distillers dried grains with solubles (DDGS) from ethanol production and glycerol from biodiesel. Currently these coproducts are undervalued, but they have application in the plastics industry as property modifiers. This research effort has quantified the effects on mechanical properties of adding DDGS and glycerol to a commercial thermoplastic starch (TPS). The methodology was to physically mix DDGS, as filler, with the TPS pellets and injection mold the blends into test bars using glycerol as a processing aid. The bars were then mechanically tested with blends from 0 to 65 %, by weight, of plasticized filler. The test bars were typically relatively brittle with little yielding prior to fracture with elongation between 1 and 3 %. The addition of glycerol enabled molding of blends with high levels of DDGS but did not increase strength. Any presence of filler decreased the tensile strength of the starch, and up to 30 % filler, the tensile strength drops about 15 %. The 20 and 50 % blends (without glycerol) have slightly greater stiffness than pure starch. With some other blends, the presence of plasticized filler degrades the tensile modulus with 35 % filler yielding about 1/3 the stiffness. Changes in the flexural modulus are much more pronounced as 20–25 % filled TPS has a 30 % increase in flexural stiffness. In terms of surface hardness, blends up to 60 % filler are within 20 % of the TPS baseline.     

Injection-Molded Bioblends from Lignin and Biodegradable Polymers: Processing and Performance Evaluation

This paper investigates the effects of the incorporation of lignin and small quantities of epoxidized natural rubber (ENR) as an impact modifying agent on blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL). The addition of lignin resulted in a slight improvement of flexural strength and modulus of the ternary blending system. Incorporation of ENR into the blend resulted in an increase in notched Izod impact strength from 40 to 135% depending on the concentration of ENR. The addition of lignin into the blend resulted in an improvement of thermal stability of the ternary blend system. Morphological analysis showed a good dispersion of PHBV phases and lignin within the PCL matrix. Rheological characterization revealed that the presence of lignin resulted in increased storage modulus of the bioblend.     

Biodegradation of Injection Molded Starch-Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Blends in a Natural Compost Environment

Injection molded specimens were prepared by blending poly (hydroxybutyrate-co-valerate) (PHBV) with cornstarch. Blended formulations incorporated 30% or 50% starch in the presence or absence of poly-(ethylene oxide) (PEO), which enhances the adherence of starch granules to PHBV. These formulations were evaluated for their biodegradability in natural compost by measuring changes in physical and chemical properties over a period of 125 days. The degradation of plastic material, as evidenced by weight loss and deterioration in tensile properties, correlated with the amount of starch present in the blends (neat PHBV < 30% starch < 50% starch). Incorporation of PEO into starch-PHBV blends had little or no effect on the rate of weight loss. Starch in blends degraded faster than PHBV and it accelerated PHBV degradation. Also, PHBV did not retard starch degradation. After 125 days of exposure to compost, neat PHBV lost 7% of its weight (0.056% weight loss/day), while the PHBV component of a 50% starch blend lost 41% of its weight (0.328% weight loss/day). PHB and PHV moieties within the copolymer degraded at similar rates, regardless of the presence of starch, as determined by ¹H-NMR spectroscopy. GPC analyses revealed that, while the number average molecular weight (Mn) of PHBV in all exposed samples decreased, there was no significant difference in this decrease between neat PHBV as opposed to PHBV blended with starch. SEM showed homogeneously distributed starch granules embedded in a PHBV matrix, typical of a filler material. Starch granules were rapidly depleted during exposure to compost, increasing the surface area of the PHBV matrix.     

Study on Biodegradable Starch/OMMT Nanocomposites for Packaging Applications

The thermoplastic starch (TPS) and nanocomposite(TPS/OMMT) was prepared with 15% carbamide, 15% ethanolamine and different contents of organic activated montmorillonite (OMMT) by twin-screw extruder with a 130 °C barrel temperature. Fourier transforms infrared spectroscopy and wide angle X-ray diffraction shown that the alkylamine in dodecyl benzyl dimethyl ammonium bromide could react with MMT via cation exchange reaction. After treated, the d(001)space distance of MMT increased from 1.5 to 1.7 nm. Scanning electron microscope revealed that the lower contents of OMMT could disperse well in the matrixes of TPS. The carbamide, ethanolamine and the OMMT could destroy the crystallization behavior of starch, but only the OMMT restrained this behavior for long-term storing. Mechanical properties investigation indicated that the tensile strength and modulus of TPS/OMMT nanocomposites were better than those of TPS, while the elongation at break was descended with the increasing of OMMT contents. When the content of OMMT was 4%, the tensile strength and modulus of TPS was improved from 4.2 and 42 MPa to 6.0 and 76 MPa, respectively.     

A Processing,Characterization and Marine Biodegradation Study of Melt-Extruded Polyhydroxyalkanoate (PHA) Films

A series of polyhydroxyalkanoates (PHA), all containing 1% nucleating agent but varying in structure, were melt-processed into films through single screw extrusion techniques. This series consisted of three polyhydroxybutyrate (PHB) and three polyhydroxybutyrate-valerate (PHBV) resins with varying valerate content. Processing parameters of temperature in the barrel (165–173 °C) and chill rolls (60 °C) were optimized to obtain cast films. The gel-permeation chromatography (GPC) results showed a loss of 8–19% of the polymer’s initial molecular weight due to extrusion processing. Modulated differential scanning calorimetry (MDSC) displayed glass transition temperatures of the films ranging from −4.6 to 6.7 °C depending on the amount of crystallinity in the film. DSC data were also used to calculate the percent crystallinity of each sample and slightly higher crystallinity was observed in the PHBV series of samples. X-ray diffraction patterns did not vary significantly for any of the samples and crystallinity was confirmed with X-ray data. Dynamic mechanical analysis (DMA) verified the glass transition trends for the films from DSC while loss modulus (E′) reported at 20 °C showed that the PHBV (3,950–3,600 MPa) had the higher E′ values than the PHB (3,500–2,698 MPa) samples. The Young’s modulus values of the PHB and PHBV samples ranged from 700 to 900 MPa and 900 to 1,500 MPa, respectively. Polarized light microscopy images revealed gel particles in the films processed through single-screw extrusion, which may have caused diminished Young’s modulus and tensile strength of these films. The PHBV film samples exhibited the greatest barrier properties to oxygen and water vapor when compared to the PHB film samples. The average oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) for the PHBV samples was 247 (cc-mil/m²-day) and 118 (g-mil/m²-day), respectively; while the average OTR and WVTR for the PHB samples was 350 (cc-mil/m²-day) and 178 (g-mil/m²-day), respectively. Biodegradation data of the films in the marine environment demonstrated that all PHA film samples achieved a minimum of 70% mineralization in 40 days when run in accordance with ASTM 6691. For static and dynamic incubation experiments in seawater, microbial action resulting in weight loss as a function of time showed all samples to be highly biodegradable and correlated with the ASTM 6691 biodegradation data.     

Biodegradable corn starch loose- fill. I. The effect of the extrusion temperature on the physical properties of loose-fill

Extrusion with an intermeshing corotating twin-screw extruder with a limited amount of water caused structural changes in corn starch. The structural changes resulted in a transformation-from a semicrystalline to an amorphous state and the development of orientation of molecular chains in the amorphous region during extrusion. These structural changes, in turn, caused an increase in theT _g, tensile strength, and resilience of the extruded corn starch. Our experimental results showed that the tensile properties and resilience of the expanded corn starch extruded at 240‡C were the best: tensile strength, 1.7 kPa; tensile modulus, 40.4 kPa; and resilience, 57.2%. Extrusion produced an expanded corn starch suitable for protective loose-fill.     

Mechanical Properties of Poly (Lactic Acid)/Hemp Fiber Composites Prepared with a Novel Method

This research dealt with a novel method of fabricating green composites with biodegradable poly (lactic acid) (PLA) and natural hemp fiber. The new preparation method was that hemp fibers were firstly blending-spun with a small amount of PLA fibers to form compound fiber pellets, and then the traditional twin-screw extruding and injection-molding method were applied for preparing the composites containing 10–40 wt% hemp fibers with PLA pellets and compound fiber pellets. This method was very effective to control the feeding and dispersing of fibers uniformly in the matrix thus much powerful for improving the mechanical properties. The tensile strength and modulus were improved by 39 and 92 %, respectively without a significant decrease in elongation at break, and the corresponding flexural strength and modulus of composites were also improved by 62 and 90 %, respectively, when the hemp fiber content was 40 wt%. The impact strength of composite with 20 wt% hemp fiber was improved nearly 68 % compared with the neat PLA. The application of the silane coupling agent promoted further the mechanical properties of composites attributed to the improvement of interaction between fiber and resin matrix.     

Tensile Strength, Elongation, Hardness, and Tensile and Flexural Moduli of PLA Filled with Glycerol-Plasticized DDGS

Rapid growth of the biofuel industry is generating large amounts of coproducts such as distillers dried grains with solubles (DDGS) from ethanol production and glycerol from biodiesel. Currently these coproducts are undervalued, but they have application in the plastics industry as property modifiers. The objective of this research effort is to quantify the effects on mechanical properties of adding DDGS and glycerol to polylactic acid (PLA). The methodology was to physically mix DDGS, as filler, with PLA pellets and injection mold the blends into test bars using glycerol as a plasticizer. The bars were subject to mechanical testing procedures to obtain tensile strength, tensile and flexural moduli, elongation to break, and surface hardness of blends from 0 to 90?%, by weight, of plasticized filler. Blends were typically relatively brittle with little or no yielding prior to fracture, and the addition of glycerol enabled molding of blends with high levels of DDGS but did not increase strength. Any presence of filler decreased the tensile strength of the PLA, and 20?C30?% filler reduced strength by 60?%. The 35?C50?% filled PLA had about one-fifth the value for pure PLA; at 60?C65?% filler level, about 10?% tensile strength remained; and over 80?% filler, 95?% of the strength was lost. Over 20?% filler, the tensile modulus decreased. The 35?% plasticized, filled blend yielded about one-half the stiffness as the pure PLA case; flexural modulus trended in the same manner but demonstrated a greater loss of stiffness. Most blends had less than 3?% elongation to break while surface hardness measurements indicated that up to 60?% filler reduced Shore D hardness by less than 20?%. The tensile strength and modulus data are consistent with the findings of other researchers and indicate that the type of filler and amount and sequence of plasticization are secondary effects, and the total PLA displaced is the dominant factor in determining the mechanical strength of the PLA and DDGS blends. Up to 65?% plasticized DDGS filler can be injection molded, and sufficient mechanical strength exists to create a variety of products. Such a novel material provides higher-value utilization of the biofuel coproducts of glycerol and DDGS and maintains the biodegradable and biocompatible nature of PLA.     

Effect of Orientation on the Morphology and Mechanical Properties of PLA/Starch Composite Filaments

Polylactic acid (PLA)/starch fibers were produced by twin screw extrusion of PLA with granular or gelatinized starch/glycerol followed by drawing through a set of winders with an intermediate oven. At 30% starch, fibers drawn 2–5x were highly flexible (elongation 20–100%) while undrawn filaments were brittle (elongation 2–9%). Tensile strength and moduli increased with increasing draw ratio but decreased with increasing starch content. Mechanical properties were better for composites made with gelatinized starch/glycerol than granular starch. In conclusion, orientation greatly increases the flexibility of PLA/starch composites and this may be useful not only in fibers but also possibly in molded articles. Other advantages of starch addition could include fiber softness without added plasticizer, moisture/odor absorbency and as a carrier for active compounds.     

Effect of Hexadecyl Lactate as Plasticizer on the Properties of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) Films for Food Packaging Applications

In this study, poly(l-lactide) (PLA) films were fabricated by melt processing and the plasticizing effect of hexadecyl lactate (HL) (0, 5, 7.5, 10, and 12.5 wt% on PLA were investigated by scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis, tensile, transparency, and water vapor permeability tests. The SEM analysis revealed that PLA with 10 wt% HL appeared uniform with extra small bumps, confirmed the interaction between PLA and HL. The thermal analysis revealed a glass transition temperature of 57.4 °C for neat PLA film, but the addition of HL elicited a decrease in the temperature of the peak (43.8 °C). The incorporation of plasticizer into PLA resulted in the increase of elongation at break, as well as the decrease of tensile strength and tensile modulus. Even though a decrease in transparency was recorded, the PLA/HL blend films appeared transparent by visually observation. The water vapor permeability of PLA/HL blend films increased with the increase of HL. The PLA/HL blend films could effectively extend the shelf-life of fresh-cut pears as the commercial low density polyethylene films. The results indicated that the properties of PLA films can be modified with the addition of HL and PLA/HL blend films could serve as an alternative as food packaging materials to reduce environmental problems associated with synthetic packaging films.     

Possible use of sludge ash as filler in natural rubber

Potential use of sludge ash as a filler in NR was studied. In this study, two grades of sludge ash namely SA-300 and SA-700 were prepared by sintering sludge waste obtained from concentrated natural rubber (NR) latex production at 300 and 700 °C, respectively. Properties of NR filled with various contents of SA-300 and SA-700 were then investigated and compared with those of NR filled with precipitated calcium carbonate (CaCO₃). The results reveal that, regardless of the filler type, both scorch time (t _s1) and optimum cure time (t _c90) decrease whereas hardness and modulus increase with increasing filler loading. At a given loading, both SA-300 and SA-700 give shorter scorch time and cure time with higher hardness and modulus than CaCO₃. Due to their higher specific surface area and greater cure activation efficiency, SA-300 and SA-700 provide better reinforcement, i.e., greater tensile strength; tear strength and abrasion resistance than CaCO₃. Taken as a whole, it could be said that the two grades of sludge ash could be utilized as rubber fillers with economic advantage.