Effect of Cotton Fiber Contents and Lengths on Properties of Thermoplastic Starch Composites Prepared from Rice and Waxy Rice Starches

Biodegradable polymer was prepared as thermoplastic starch (TPS) using rice and waxy rice starches. In order to increase mechanical properties and reduce water absorption of the TPS, cotton fiber was incorporated as the fiber reinforcement into the TPS matrix. The effect of cotton fiber contents and lengths on properties of the TPS was examined. Internal mixer and compression molding machine were used to mix and shape the samples. It was found that the thermoplastic rice starch (TPRS) showed higher stress at maximum load and Young’s modulus but lower strain at maximum load than the thermoplastic waxy rice starch (TPWRS). In addition, stress at maximum load and Young’s modulus of both TPRS and TPWRS increased significantly with the addition of the cotton fiber. Cotton fiber contents and lengths also affected mechanical properties of the TPRS and TPWRS composites. Moreover, water absorption of the TPRS and TPWRS composites decreased by the use of the cotton fibers. FT-IR and XRD techniques were used to study a change in functional group and crystallinity of the thermoplastic starch composites. Morphological, thermal and biodegradable properties of different thermoplastic starch composites were also investigated.     

Behavior of Cellulose Reinforced Cross-Linked Starch Composite Films Made with Tartaric Acid Modified Starch Microparticles

Tartaric acid modified starch microparticles (TA-SM) previously obtained using the dry preparation technique were introduced as filler within glycerol plasticized-corn starch (GCS), the composites being prepared by casting process. The effects of cellulose addition within the TA-SM-GCS matrix on the structure, surface properties and water sorption, as well as mechanical and thermal properties of starch-based composite films were investigated. The water resistance and thermal stability were slightly improved through addition of high content of cellulose due to the inter-component H-bonding between components. The evaluation of mechanical properties evidenced a significant increase of the tensile strength of the composites with increasing the content level of cellulose.     

Preparation and Properties of Green Composites Based on Tapioca Starch and Differently Recycled Paper Cellulose Fibers

Green composites obtained from biodegradable renewable resources have gained much attention due to environmental problems resulting from conventionally synthetic plastics and a global increasing demand for alternatives to fossil resources. In this work we used different cellulose fibers from used office paper and newspaper as reinforcement for thermoplastic starch (TPS) in order to improve their poor mechanical, thermal and water resistance properties. These composites were prepared by using tapioca starch plasticized by glycerol (30 % wt/wt of glycerol to starch) as matrix reinforced by the extracted cellulose fibers with the contents ranging from 0 to 8 % (wt/wt of fibers to matrix). Properties of composites were determined by mechanical tensile tests, differential scanning calorimetry, thermogravimetric analysis, water absorption measurements, scanning electron microscopy, and soil burial tests. The results showed that the introduction of either office paper or newspaper cellulose fibers caused the improvement of tensile strength and elastic modulus, thermal stability, and water resistance for composites when compared to the non-reinforced TPS. Scanning electron microscopy showed a good adhesion between matrix and fibers. Moreover, the composites biological degraded completely after 8 weeks but required a longer time compared to the non-reinforced TPS. The results indicated that these green composites could be utilized as commodity plastics being strong, inexpensive, plentiful and recyclable.     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

Effect of Coconut, Sisal and Jute Fibers on the Properties of Starch/Gluten/Glycerol Matrix

Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torque rheometer (120 °C, 50 rpm) for 6 min. The mixtures obtained were molded by heat compression and further characterized. Addition of lignocellulosic fibers in the matrix decreased the water absorption at equilibrium. The diffusion coefficient decreased sharply around 5% fiber concentration, and further fiber additions caused only small variations. The thermogravimetric (TG) analysis revealed improved thermal stability of matrix upon addition of fibers. The Young’s modulus and ultimate tensile strength increased with fiber content in the matrix. The storage modulus increased with increasing fiber content, whereas tanδ curves decreased, confirming the reinforcing effect of the fibers. Morphology of the composites analyzed under the scanning electron microscope (SEM) exhibited good interfacial adhesion between the matrix and the added fibers. Matrix degraded rapidly in compost, and addition of increased amounts of coconut fiber in the matrix caused a slowdown the biodegradability of the matrix. 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 USDA implies no approval of the product to the exclusion of others that may be suitable.     

Evaluation of the Biodegradability of Polyvinyl Alcohol/Starch Blends: A Methodological Comparison of Environmentally Friendly Materials

Polyvinyl alcohol (PVA) and starch are both biodegradable polymers. These two polymers can be prepared as biodegradable plastics that are emerging as one of the environmental friendly materials available now. In this study, after reacting with sodium trimetaphosphate (STMP), modified corn starch was blended with PVA in different ratios by a barbender. Test samples were prepared for mechanical and thermal properties measurements. The surface roughness and morphology of fractured surface of the samples were observed by an atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements. Aqueous degradation by enzyme, water absorption and biodegradability behavior were evaluated for the degradability. The biodegradability of these materials was followed by bio-reactivity kinetics models. Results showed that the addition of modified starch could enhance its water uptake. With an addition of 20 wt% of modified starch, the blend had a maximum weight loss during enzymatic degradation. It was found that the degradability was enhanced with the addition of the starch. Analyzing the results of the biodegradability based on the kinetic models, the growth rate of the microorganism was found to be increasing with the increase of the content of starch in the PVA/starch blends in the first order reaction fashion. In our biodegradability analysis, i.e., based on the China national standards (CNS) 14432 regulations, we estimated the decomposition behavior based on the mentioned first order reaction. We found that the PVA/starch blends would take 32.47, 16.20 and 12.47 years to degrade by 70% as their starch content 0, 20 and 40 wt%, respectively.     

Properties of Regenerated Cellulose Short Fibers/Cellulose Green Composite Films

Green composites of regenerated cellulose short fibers/cellulose were prepared by dissolving cellulose in a green solvent of 7% NaOH/12% Urea aqueous solution that was pre cooled at ?12?°C. The effect of fiber loading on the tensile, optical, thermal degradation and cell viability was studied. The tensile properties of cellulose were improved by the regenerated cellulose fiber reinforcement. The interfacial bonding between the fibers and matrix was assessed using the fractographs and found it to be good.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

The Effect of Polymeric Chain Extenders on Physical Properties of Thermoplastic Starch and Polylactic Acid Blends

The effects of a polymeric chain extender on the properties of bioplastic film made from blends of plasticized polylactic acid (p-PLA) and thermoplastic starch (TPS) were studied. Joncryl^? ADR 4370S, a polymeric chain extender, was blended with TPS and p-PLA at a level of 1% (w/w). A co-rotating twin-screw extrusion process was used to prepare films with various ratios of TPS and p-PLA. Mechanical and physical properties of films, including film tensile properties, surface energy, moisture content, hydrophilicity, moisture sorption behaviour and thermal mechanical properties were determined. During extrusion, films enhanced by 1% Joncryl addition demonstrated more desirable and consistent qualities, such as smoother film edge and surface. Addition of Joncryl significantly improved film tensile strength, 0.2% offset yield strength, and elongation, especially evident with the 250% elongation of 70/30 (TPS/p-PLA) film. Total surface energy of films was not significantly influenced by addition of Joncryl. However, the polar contribution to the total surface energy of 70/30 (TPS/p-PLA) film increased after the addition of Joncryl. The study showed that blending TPS with p-PLA transformed TPS film from being highly hydrophilic to highly hydrophobic. On the other hand, addition of Joncryl had limited effects on moisture content, water solubility, glass transition temperature and moisture sorption behaviour of TPS/p-PLA blend films.     

Preparation and Characterization of Gamma Irradiated Sugar Containing Starch/Poly (Vinyl Alcohol)-Based Blend Films

Blends based on different ratios of starch (35–20%) and plasticizer (sugar; 0–15%) keeping the amount of poly(vinyl alcohol) (PVA) constant, were prepared in the form of thin films by casting solutions. The effects of gamma-irradiation on thermal, mechanical, and morphological properties were investigated. The studies of mechanical properties showed improved tensile strength (TS) (9.61 MPa) and elongation at break (EB) (409%) of the starch-PVA-sugar blend film containing 10% sugar. The mechanical testing of the irradiated film (irradiated at 200 Krad radiation dose) showed higher TS but lower EB than that of the non-radiated film. FTIR spectroscopy studies supported the molecular interactions among starch, PVA, and sugar in the blend films, that was improved by irradiation. Thermal properties of the film were also improved due to irradiation and confirmed by thermo-mechanical analysis (TMA), differential thermo-gravimetric analysis (DTG), differential thermal analysis (DTA), and thermo-gravimetric analysis (TGA). Surface of the films were examined by scanning electron microscope (SEM) image that supported the evidence of crosslinking obtained after gamma irradiation on the film. The water up-take and degradation test in soil of the film were also evaluated. In this study, sugar acted as a good plasticizing agent in starch/PVA blend films, which was significantly improved by gamma radiation and the prepared starch-PVA-sugar blend film could be used as biodegradable packaging materials.     

Biopolymers Based Green Composites: Mechanical, Thermal and Physico-chemical Characterization

Natural cellulosic fibers are one of the smartest materials for use as reinforcement in polymers possessing a number of applications. Keeping in mind the immense advantages of the natural fibers, in present work synthesis of natural cellulosic fibers reinforced polymer composites through compression molding technique have been reported. Scanning Electron microscopy (SEM), Thermo gravimetric/Differential thermal/Derivative Thermogravimetry (TGA/DTA/DTG), absorption in different solvents, moisture absorbance, water uptake and chemical resistance measurements were used as characterization techniques for evaluating the different behaviour of cellulosic natural fibers reinforced polymer composites. Effect of fiber loading on mechanical properties like tensile strength, flexural strength, compressive strength and wear resistances has also been determined. Reinforcing of the polymer matrix with natural fibers was done in the form of short fiber. Present work indicates that green composites can be successfully fabricated with useful mechanical properties. These composites may be used in secondary structural applications in automotive, housing etc.     

Biodegradable nanocomposites based on poly(butylene succinate)/organoclay

In this work, we try to incorporate the inorganic system into the biodegradable polymers to compose an organic/inorganic polymer hybrid. Various nanocomposites of poly(butylene succinates) (PBS) with different ratios of organically modified layered silicates (OMLS) prepared by solution blending were investigated. The OMLS used for the preparation of nanocomposites were functionalized ammonium salts modified montmorillonite. The effects of OMLS on the nanocomposites were investigated by XRD, TEM, DMA and TGA in the aspect of the d-spacing of clay, mechanical and thermal properties. Interestingly, all these nanocomposites exhibited improved properties when compared with the pristine PBS sample. XRD indicates that the layers of clay were intercalated by the modifiers, and the interlayer distance of organoclay in the nanocomposites could be extended to about 29.4 Å. Moreover, the thermal stability of the nanocomposites was enhanced by the addition of organoclay via TGA study, closely related to the organoclay content in the PBS matrix. DMA data shows that the storage and loss moduli were concurrently enhanced by the addition of organoclay as compared to the pristine PBS sample. Moreover, the glass transition temperatures also increased about 5 to 20 °C (from DMA, peak of tanδ) for the various organoclay-containing samples. The enhanced mechanical and thermal properties can be achieved from these organoclay modified-nanocomposites.     

Hybrid Composites from Waste Materials

Hybrid composites of thermoplastic biofiber reinforced with waste newspaper fiber (NF) and poplar wood flour (WF) were prepared. The weight ratio of the lignocellulosic materials to polymer was 30:70 (w:w). Polypropylene (PP) and maleic anhydride grafted polypropylene (MAPP) were also used as the polymer matrix and coupling agent, respectively. The mechanical properties, morphology and thermal properties were investigated. The obtained results showed that tensile and flexural modulus of the composites were significantly enhanced with addition of biofibers in both types (fiber and flour), as compared with pure PP. However, the increasing in WF content substantially reduced the tensile, flexural and impact modulus, but improved the thermal stability. This effect is explained by variations in fiber morphological properties and thermal degradation. Increasing fiber aspect ratio improved mechanical properties. The effect of fiber size on impact was minimal compared to the effects of fiber content. Scanning electron microscopy has shown that the composite, with coupling agent, promotes better fiber–matrix interaction. The largest improvement on the thermal stability of hybrid composites was achieved when WF was added more. In all cases, the degradation temperatures shifted to higher values after addition of MAPP. This work clearly showed that biofiber materials in both forms of fiber and flour could be effectively used as reinforcing elements in thermoplastic PP matrix.     

Preparation and Characterization of Clay Nanocomposites of Plasticized Starch and Polypropylene Polymer Blends

Plasticized starch (PLS) is a renewable, degradable, and inexpensive polymer, but it suffers from poor mechanical properties. The mechanical properties can be improved by blending PLS with polyolefins, nonetheless, at high PLS content, the mechanical properties remain poor. Here we show that addition of clay can greatly improve the mechanical properties of PLS/polypropylene blends at high starch content. Unmodified and organically modified montmorillonite clays, MMT and Cloisite 30B respectively, were added to blends of glycerol-plasticized starch and polypropylene, compatibilized using maleated polypropylene. TEM indicates that MMT is well dispersed in the PLS phase of the blends, while Cloisite 30B is located both within the PLS phase as well as at the interface between PLS and PP. At high PLS content, the addition of clay increased the tensile strength and tensile modulus by an order of magnitude, while reducing the ultimate elongation only slightly. Such improvements are attributable to both the addition of clay as a reinforcing component, as well as to the change in the two phase morphology due to addition of clay.     

Performance of Cow Dung Reinforced Biodegradable Poly(Lactic Acid) Biocomposites for Structural Applications

In this work, performance of cow dung (CD) reinforced poly(lactic acid) (PLA) biocomposites was investigated for the potential use in load bearing application. CD of average 4 mm size was blended with PLA at different CD ratios (0–50 wt%) and their effects on the biocomposite properties were studied. The results showed an improvement in the flexural properties, while the tensile and impact strength dropped by 20 and 28% with the addition of 50% CD. The decline in the tensile and impact strength was due to micro-cracking and voids formation at higher CD content. Also, the incorporation of CD slightly decreased the thermal stability of the biocomposite. However, dynamic mechanical properties of the biocomposites generally improved. SEM analysis of tensile and impact fractured surfaces indicated that the CD had a reasonable adhesion with matrix. Moreover, the SEM micrographs of soil burial studies showed an accelerated degradation of higher CD wt% biocomposites.     

Potential Use of Recycled PET in Comparison with Liquid Crystalline Polyester as a Dual Functional Additive for Enhancing Heat Stability and Reinforcement for High Density Polyethylene Composite Fibers

The recycle poly(ethylene terephthalate) (rPET) used as an alternative reinforcing material for in situ microfibrillar-reinforced composite, compared with liquid crystalline polymer (LCP), was investigated. The PE-LCP and PE-rPET composites were prepared as fiber using hot drawing process. The effects of draw ratios and compatibilizer (styrene-ethylene butylene-styrene-grafted maleic anhydride, SEBS-g-MA) loading on morphology, tensile properties, thermal stability and dynamic mechanical characteristics of the LCP- and rPET-composite systems were studied. In as-spun samples containing compatibilizer, the fibrillation of LCP domains was observed whereas rPET domains appeared as droplets. After drawing, good fibrillation of LCP and rPET domains is remarkably observed especially in the composite fibers with compatibilizer loading. The mechanical properties of the composite fibers were strongly depended on the fibrillation of the dispersed phases which directly related the levels of draw ratio and compatibilizer loading. The mechanical properties enhanced by SEBS-g-MA were more pronounced in the rPET than LCP systems. The presence of rPET in the composite fibers alone or with the compatibilizer clearly improved the thermal resistance of PE whereas no significant change in thermal stability for the LCP-containing composite fibers with and without compatibilizer loading. The results from dynamic mechanical analysis revealed that an improvement in dynamic mechanical properties of the composite fibers could be achieved by drawing with optimum draw ratio together with optimum compatibilizer dosage. All obtained results suggested the high potential of rPET minor blend-component as a good reinforcing and thermal resistant materials for the thermoplastic composite fiber, in replacing the more expensive LCP.     

Interactive Influence of Biofiber Composition and Elastomer on Physico-Mechanical Properties of PLA Green Composites

The objective of this work was to improve the impact and thermal properties of polylactic acid (PLA)-based biocomposite by appropriate application of cellulosic fiber and a bioelastomer. Biocomposites formulations with fiber contents of up to 20% in combination with a bioelastomer were extrusion-compounded in a twin-screw extruder followed by molding in an injection molding system. Fibers used in the formulations included three types of cellulosic fiber; namely, raw fiber from oat hull biomass (RF), hydrolysis byproduct (ATF) which was the solid fraction obtained from an acid-catalyzed hydrolysis of RF, and delignified fibers (AD30, AD65, AD100) which were the products of delignification of ATF. Formulated biocomposites were characterized for thermal (glass transition and melting temperatures, and enthalpy of melting) and physico-mechanical (tensile and bending strengths, stiffness, impact energy, and water absorption) properties. Among all types of biofibers, RF resulted in poor properties in the biocomposites due to the high hemicellulose content in the structure. On the other hand, the ratio of lignin to cellulose (in the absence of hemicellulose) in the modified fibers did not significantly affect the physico-mechanical and thermal properties of the biocomposites. The elastomer applied in the formulations improved the impact energy, thermal properties, and elongation at break of the composites. However, it adversely affected the strength and water resistance of biocomposites, especially in the presence of hemicellulose. The results indicated that, depending on the application, a wide range of PLA green composites with different physico-mechanical properties can be achieved.     

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.     

Preparation and Biodegradation of Starch/Polycaprolactone Films

Starch granules were modified with trisodium trimetaphosphate (TSTP) and characterized by P³¹-NMR, FTIR and DSC. Seventy-micron films were prepared from modified starch and polycaprolactone blends by solvent casting technique. Three different types of films—PCL (100% polycaprolactone), MOD-ST/PCL (50% modified starch and 50% polycaprolactone blend) and NONMOD-ST/PCL (50% nonmodified starch and 50% polycaprolactone blends)—were prepared, and their thermal, mechanical, and morphologic properties were investigated to show the increased performance of PCL with the addition of starch and also the effect of modification. It was observed that with the addition of starch the Young's modulus of polycaprolactone was increased and became less ductile, whereas tensile strength and elongation at break values decreased. Biodegradation of these films was inspected under different aerobic environments with the presence of Pseudomonas putida, activated sludge, and compost. It was observed that whereas P. putida had almost no effect on degradation during 90 days, with the presence of activated sludge, considerable deformation of films was observed even in the first 7 days of degradation. In a compost environment, degradation was even faster, and all polymer films were broken into pieces within first 7 days of degradation and no film remained after 15 days.     

Storage stability of injection-molded starch-zein plastics under dry and humid conditions

Corn starch and zein mixtures (4 : 1 dry weight) were extruded and injection-molded in the presence of plasticizers (glycerol and water). Tensile strength and percentage elongation of the molded plastics were measured before and after 1 week of storage under a dry or humid condition (11 or 93% RH). With 10–12% glycerol and 6–8% water, injection-molded plastics had relatively good tensile properties (20- to 25-MPa tensile strength and 3.5–4.7% elongation). But while exposed to dry conditions (11% RH), the molded plastics lost weight (0.5–1.5% in 7 days) and became very brittle, with significant decreases in tensile strength and elongation. Partial replacement (5–10%) of starch with a maltodextrin (average DE 5) reduced the glass transition and melting temperatures of the starch-zein mixture as well as the dry storage stability. Using potato starch instead of corn starch significantly improved the dry storage stability of the injection-molded starch-zein plastics (18- vs 11-MPa tensile strength). Anionic corn starches with a maleate or succinate group (DS<0.01) produced injection-molded plastics with improved tensile properties and storage stability. Plastics prepared from the starch maleate and zein mixture retained the strength during 1 week of dry storage without a significant change (26-MPa tensile strength and 3.7% elongation after 1 week of storage).Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Journal paper No. J-15561 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2863.