Mechanical properties,hydrophobic properties and thermal stability of the biodegradable poly(butylene adipate-<Emphasis Type="Italic">co</Emphasis>-terephthalate)/maleated thermoplastic starch blown films

Poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) were blended by using maleic anhydride (MA) as a compatibilizer. Preferentially, TPS could be reacted with MA to obtain maleated thermoplastic starch (MTPS). Then PBAT/MTPS blends were blown films using blown technique. From dynamic mechanical analysis, the shifting of the glass transition temperatures toward each other suggested that PBAT was partially miscible with MTPS. From wide angle X-ray diffraction analysis, the degree of crystallinity of PBAT/MTPS films was decreased with increasing MTPS content. From rheological measurements, the melt elasticity and viscosity of the PBAT/MTPS blends increased. It was benefit to extrude blend and blow film. The contact angle values of bipolar liquid water were range from 100.2 to 77.7 ° decreased with increasing MTPS content from 0 to 50 %. The PBAT/MTPS films could satisfy the requirement for applying in our life.     

Influence of carboxylic acids on mechanical properties of thermoplastic starch by spray drying

Biodegradable packaging is gaining much attention in food industry as the awareness on sustainability has increased. Thermoplastic starch is a possible alternative. This study evaluated the influence of malic acid (MA) and citric acid (CA), used as a plasticizer, on the mechanical properties of thermoplastic starch (TPS) obtained by spray drying. TPS powder was produced from solution spray drying. This powder was further compression molded to prepare TPS dog-bone test samples. X-ray Diffraction (XRD) results showed that both the spray dried TPS powder and dog-bone test samples were amorphous in nature irrespective of the amount of plasticizer added. Scanning electron microscope (SEM) was used to examine the morphology of solution spray dried TPS powder. No noticeable difference was observed in the morphology. Particles were spherical in shape with homogenous surface. The FT-IR analysis indicated the interaction of plasticizers with starch chains by hydrogen bonding. During TGA analysis, apart from moisture loss at 100 °C, samples were thermally stable up to 170 °C. Mechanical testing of TPS dog-bone revealed that sample containing malic acid as plasticizer exhibited a more elastic behavior as compared to citric acid plasticized formulations. It was revealed that the tensile strength of TPS dog-bone samples was inversely proportional to the quantity of plasticizer used.     

Properties of thermoplastic starch from cassava bagasse and cassava starch and their blends with poly (lactic acid)

Cassava bagasse is an inexpensive and broadly available waste byproduct from cassava starch production. It contains roughly 50% cassava starch along with mostly fiber and could be a valuable feedstock for various bioproducts. Cassava bagasse and cassava starch were used in this study to make fiber-reinforced thermoplastic starch (TPS_B and TPS_I, respectively). In addition, blends of poly (lactic acid) and TPS_I (20%) and TPS_B (5, 10, 15, 20%) were prepared as a means of producing low cost composite materials with good performance. The TPS and PLA blends were prepared by extrusion and their morphological, mechanical, spectral, and thermal properties were evaluated. The results showed the feasibility of obtaining thermoplastic starches from cassava bagasse. The presence of fiber in the bagasse acted as reinforcement in the TPS matrix and increased the maximum tensile strength (0.60 MPa) and the tensile modulus (41.6 MPa) compared to cassava starch TPS (0.40 and 2.04 MPa, respectively). As expected, blending TPS with PLA reduced the tensile strength (55.4 MPa) and modulus (2.4 GPa) of neat PLA. At higher TPS_B content (20%) the maximum strength (19.9 MPa) and tensile modulus (1.7 GPa) were reduced about 64% and 32%, respectively, compared to the PLA matrix. In comparison, the tensile strength (16.7) and modulus (1.2 GPa) of PLA blends made with TPS_I were reduced 70% and 51% respectively. The fiber from the cassava bagasse was considered a filler since no increase in tensile strength of PLA/TPS blends was observed. The TPS_I (33.1%) had higher elongation to break compared to both TPS_B (4.9%) and PLA (2.6%). The elongation to break increased from 2.6% to 14.5% by blending TPS_I with PLA. In contrast, elongation to break decreased slightly by blending TPS_B with PLA. Thermal analysis indicated there was some low level of interaction between PLA and TPS. In PLA/TPS_B blends, the TPS_B increased the crystallinity of the PLA component compared to neat PLA. The fiber component of TPS_B appeared to have a nucleating effect favoring PLA crystallization.     

Preparation and characterization of cellulose nanofiber reinforced thermoplastic starch composites

In the present study, cellulose nanofibers composite films were manufactured based on thermoplastic starch. Nanofibers were extracted from rice straw employing a developed chemo-mechanical method. In the chemical step, almost all of non-cellulosic components were removed and a white pulp of cellulose microfibers was obtained. Then, a diluted suspension of fibers was ultrasonicated to destruct intermolecular hydrogen bonds achieving nanofibers networks. Afterward, bio-nanocomposites were prepared by film casting. In order to study the effect of nanofibers content on the composite properties, the mechanical and dynamic mechanical properties, morphology, humidity absorption, and transparency of films were investigated. The yield strength and Young modulus of nanocomposites were satisfactorily enhanced compared to the pure thermoplastic starch film. The glass transition temperature of films was shifted to higher temperatures by increasing nanofibers contents. The uniform dispersion of the nanofibers was investigated using SEM images. The humidity absorption resistance of films was significantly enhanced by using 10 wt% cellulose nanofibers. The transparency of the nanocomposites was reduced compared to the pure starch films.     

Controlling the moisture absorption capacity in a fiber-reinforced thermoplastic starch using sodium trimetaphosphate

A novel biodegradable material derived from thermoplastic potato starch was prepared with intended uses in high moisture environments where its high water sorption characteristics are beneficial, such as wound dressing, transdermal patches or food packaging. A modified composite was prepared for this purpose by reactive extrusion whereby potato starch and 2.5-25% (w/w) sisal cellulose fibers were compounded together in the presence of 2.7% (w/w) sodium trimetaphosphate. The fibers were included to increase the wet strength of the material. A low degree of substitution (0.088-0.113) was sought by bound phosphate groups with anionic character in order to overcome a reduction in moisture absorption capacity resulting from fiber incorporation, yet being insufficient to cause embrittlement via crosslinking. The results showed the approach has sufficient merit to minimize the influence of the hydrophobic fibers on the water absorption capacity of the starch material but adhering to so low of a degree of substitution could not fully prevent a reduction. The results also suggested that the fibers may have participated in the crosslinking reaction.     

Properties of thermoplastic composites with cotton and guayule biomass residues as fiber fillers

This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical properties (ash, lignin and cellulose contents). A laboratory experiment was designed with five fiber filler treatments, namely control (oak wood fiber as the filler - OWF), cotton burr and sticks (CBS), CBS with 2% (by weight) second cut linters (CBL), CBS with 30% (by weight) guayule whole plant (CGP), and CBS with 30% (by weight) guayule bagasse (CGB). The composite samples were manufactured with 50% of fiber filler, 40% of virgin high-density polyethylene (HDPE), and 10% other additives by weight. The samples were extruded to approximately 32 × 7 mm cross-sectional profiles, and tested for physico-mechanical properties. The CBS and CBL had considerably lower bulk density than the other fibers. Cotton linters had the highest α-cellulose (66.6%), and lowest hemicellulose (15.8%) and lignin (10.5%) of all fibers tested. Guayule whole plant had the lowest α-cellulose and highest ash content. Both CBS and guayule bagasse contained α-cellulose comparable to OWF, but slightly lower hemicellulose. Evaluation of composite samples made from the five fiber treatments indicated that fibers from cotton gin byproducts and guayule byproducts reduced the specific gravity of the composites significantly. However, the CBS and CBL samples exhibited high water absorption and thickness swelling, but the addition of guayule bagasse reduced both properties to similar levels as the wood fiber. The CGP exhibited significantly lower coefficient of thermal expansion. Composite samples with the five different fiber fillers showed similar hardness and nail holding capacity, yet oak fibers imparted superior strength and modulus under flexure and compression with the exception of the compressive modulus of CGB composites. In general, both cotton ginning and guayule processing byproducts hold great potential as fiber fillers in thermoplastic composites.     

New strategies in the preparation of exfoliated thermoplastic starch-montmorillonite nanocomposites

A simple method based on the combination of the intercalation from solution and melt-processing preparation methods was used to prepare highly exfoliated and compatible thermoplastic starch (TPS) and montmorillonite clay (MMT) nanocomposites. The effects of the MMT content on the thermal, structural, and mechanical properties of the nanocomposites were investigated. XRD diffraction was used to investigate the MMT exfoliation/intercalation degrees in the TPS matrix. Data from thermogravimetric analysis and differential scanning calorimetry revealed that the addition of MMT increased the thermal stabilities of TPS nanocomposites. Young's modulus and tensile strength increased from 8.0 to 23.8 MPa and 1.5 to 2.8 MPa with an increasing MMT content from 0 to 5 wt% without diminishing their flexibility. The improvement in such properties can be attributed to the good dispersion/exfoliation of MMT in the TPS matrix. Combining both methods, it was possible to obtain homogenous and transparent nanocomposites with excellent thermal and mechanical properties for application as packaging materials.     

Composite materials of thermoplastic starch and fibers from the ethanol-water fractionation of bagasse

The aim of this study was to evaluate the potential of the fibrous material obtained from ethanol-water fractionation of bagasse as reinforcement of thermoplastic starches in order to improve their mechanical properties. The composites were elaborated using matrices of corn and cassava starches plasticized with 30 wt% glycerin. The mixtures (0, 5, 10 and 15 wt% bagasse fiber) were elaborated in a rheometer at 150 °C. The mixtures obtained were pressed on a hot plate press at 155 °C. The test specimens were obtained according to ASTM D638. Tensile tests, moisture absorption tests for 24 days (20-23 °C and 53% RH, ASTM E104), and dynamic-mechanical analyses (DMA) in tensile mode were carried out. Images by scanning electron microscopy (SEM) and X-ray diffraction were obtained. Fibers (10 wt% bagasse fiber) increased tensile strength by 44% and 47% compared to corn and cassava starches, respectively. The reinforcement (15 wt% bagasse fiber) increased more than fourfold the elastic modulus on starch matrices. The storage modulus at 30 °C (E_30 °C′) increased as the bagasse fiber content increased, following the trend of tensile elastic modulus. The results indicate that these fibers have potential applications in the development of biodegradable composite materials.     

Green composites. I. physical properties of ramie fibers for environment-friendly green composites

The surface topography, tensile properties, and thermal properties of ramie fibers were investigated as reinforcement for fully biodegradable and environmental-friendly ‘green’ composites. SEM micrographs of a longitudinal and cross-sectional view of a single ramie fiber showed a fibrillar structure and rough surface with irregular cross-section, which is considered to provide good interfacial adhesion with polymer resin in composites. An average tensile strength, Young’s modulus, and fracture strain of ramie fibers were measured to be 627 MPa, 31.8 GPa, and 2.7 %, respectively. The specific tensile properties of the ramie fiber calculated per unit density were found to be comparable to those of E-glass fibers. Ramie fibers exhibited good thermal stability after aging up to 160°C with no decrease in tensile strength or Young’s modulus. However, at temperatures higher than 160°C the tensile strength decreased significantly and its fracture behavior was also affected. The moisture content of the ramie fiber was 9.9%. These properties make ramie fibers suitable as reinforcement for ‘green’ composites. Also, the green composites can be fabricated at temperatures up to 160°C without reducing the fiber properties.     

Characterization of plant and animal based natural fibers reinforced polypropylene composites and their comparative study

Natural fibers are largely divided into two categories depending on their origin: plant based and animal based. Plant based natural jute fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated by compression molding. Bending strength (BS), bending modulus (BM), tensile strength (TS), Young’s modulus (YM), and impact strength (IS) of the composites were found 44.2 MPa, 2200 MPa, 41.3 MPa, 750 MPa and 12 kJ/m², respectively. Animal based natural B. mori silk fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated in the same way and the mechanical properties were compared over the silk based composites. TS, YM, BS, BM, IS of silk fiber reinforced polypropylene composites were found 55.6 MPa, 760 MPa, 57.1 MPa, 3320 MPa and 17 kJ/m² respectively. Degradation of composites in soil was measured upto twelve weeks. It was found that plant based jute fiber/PP composite losses its strength more than animal based silk fiber/PP composite for the same period of time. The comparative study makes it clear that mechanical properties of silk/PP composites are greater than those values of jute/PP composites. But jute/PP composites are more degradable than silk/PP composites i.e., silk/PP composites retain their strength for a longer period than jute/PP composites.     

Experimental study on structure and mechanical properties of hemp/PBTG composites with fiber contents and thermal exposures

Most materials used in daily life are polymeric materials based on petrochemistry. The used polymeric materials can cause land pollution and air pollution after landfill or incineration. In contrast, natural fiber reinforced (NFR) composites are more suitable for the environment, however the reliability in terms of the durability and weatherability of NFR composites is still lacking. Thus, NFR composites require the reliability involved with durability and weatherability. In this work, poly(butylene terephthalate-co-glutarate) (PBTG), with a chemical structure similar to biodegradable PBAT, was used as the matrix in the composites, and hemp fibers were used as the reinforcement. Hemp/PBTG composites were fabricated by stacking hemp-fiberwebs and PBTG films with various fiber contents and thermal exposure times. Characteristics of the composites, such as the morphological structure, chemical structure, tensile properties, compressive properties, flexural properties, and impact strength, were analyzed to obtain the effects of fiber volume fraction and thermal exposure. As a result, hemp/PBTG composites were hardened in proportion to fiber volume fractions, and the hardening behavior of the composites increased tensile strength and flexural strength. However, the hardened structure of the composites decreased the impact strength and compressive strength of the composites. On the other hand, the mechanical properties of hemp/PBTG composites with thermal exposure times, were governed significantly by the brittleness behavior of the resin and the increased crystallinity of hemp fibers. Thus, the hemp fibers contributed to the improvements on structural stability, tensile strength and flexural strength of the hemp/PBTG composites, and increased the thermal durability of the composites with various thermal exposures.     

Novel Biodegradable Potato Starch-based Compositions as Candidates in Packaging Industry,Safe for Marine Environment

About 70 % of our planet’s surface is covered by seas and oceans to which even 10 million tons of waste go every year. It makes these places the largest global landfills, containing up to 90 % of plastic waste. In this article we present the results of research on novel starch-based compositions expected to be more safe for the marine environment. For these purpose biopolymers such as, thermoplastic starch (TPS), polylactide (PLA) and poly(vinyl alcohol) (PVA) were reactive extruded and formed into films by high-pressure compressing. Their physical, thermal and mechanical properties were examined. Compositions were tested in seawater collected from the Gulf of Gdansk Baltic Sea. The obtained samples were completely disintegrated after 3 weeks. BOD test in the presence of bacteria pseudomonas augerinosa confirmed biodegradation of prepared compositions. The impact assessment of received materials on the marine environment was also evaluated by degradation tests in the presence of Phaeodactylum tricornutum diatom. Cells growth of Phaeodactylum tricornutum diatoms was only slightly inhibited in the presence of TPS/PLA/PVA compositions.     

Thermal and mechanical properties of flax-reinforced polycaprolactone composites

Thermomechanical and mechanical properties of polycaprolactone/flax composites were investigated. The composites were prepared by melt mixing with three different filler loadings. Except from heating (to eliminate the moisture) no other procedures were applied to the raw materials, neither compatibilizer agent was used. The tensile and impact properties were evaluated and dynamic mechanical analysis was performed. Additionally the materials have been characterized by means of DSC technique. The resulting material reveal enhanced mechanical properties due to reinforcement caused by fibers and by high interfacial adhesion.     

The novel use of sodium borohydride as a protective agent for the chemical treatment of vegetable fibers

The vegetable fibers used as reinforcement for polymer matrix composites are usually treated to improve their adhesion with the matrix. The chemical treatment with sodium hydroxide (NaOH) is widely employed, but it may damage the fiber surface structure, reducing its strength. This novel study is related to the use of hydride ions (H^?) as protective agent for vegetable fibers, under alkaline treatment, as a way to promote their use in polymeric composites. Sisal fibers were modified by immersion in a NaOH aqueous solution (2, 5, and 10 % wt/vol) with or without the addition of sodium borohydride (NaBH₄) (1 % wt/vol) under different treatment conditions. The treated fibers were characterized via density and moisture content analyses and also using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effectiveness of NaBH₄ to protect the sisal fiber was more pronounced in moderate NaOH concentrations (5 %) at room temperature or higher for shorter alkaline treatment times.     

Mechanical properties,morphology and dynamic mechanical properties of LGF/TPU/SAN composites

A series of the long glass fiber reinforced thermoplastic polyurethane elastomers and poly (styrene-acrylonitrile) (LGF/TPU/SAN) composites with different contents of long glass fiber were prepared by using self-designed impregnation device. Dynamic mechanical properties of TPU/SAN matrix reinforced with 10, 20 and 30 % by weight long glass fibers have been investigated by using dynamic mechanical thermal analysis (DMA). The results indicated that the content of long glass fiber and scanning frequency had some influence on dynamic mechanical properties and glass transition of LGF/TPU/SAN composites. In addition, the Arrhenius relationship has been used to calculate the activation energy of a-transition of the LGF/TPU/SAN composites. SEM demonstrates the relatively good dispersion of the long glass fiber in the TPU/SAN matrix. In addition, Effects of the content of long glass fiber on mechanical properties of the LGF/TPU/SAN composites are investigated.     

Effect of pineapple protease on the characteristics of protein fibers

A pineapple protease, bromelain, was used to improve the dyeing properties of protein fibers such as wool and silk. The optimal condition for the activity of the pineapple protease was about 60 °C at pH 7. The wool and silk were treated with the protease extracted from a pineapple and the K/S values of the dyed wool and silk were measured using a spectrophotometer in order to compare the dye uptake. The protease treatment enhanced the dyeing properties of protein fibers without severe changes in mechanical properties. The surface appearances of protease-treated fibers were observed by microscopy.     

Basic properties of grain by-products and their viability in polypropylene composites

The objective was to study the potential of grain by-products (husk) of grains such as wheat (Triticum aestivum L; German name is Weizen) and rice (Oryza sativa) as reinforcements for thermoplastics as an alternative to or in combination with wood fibres. Prior to composites preparation, the chemical components of fibres such as cellulose, hemi-cellulose, lignin, starch, protein and fat were measured and the surface chemistry and functionality of grain by-products were studied using EDX and FT-IR. Structural constituents (cellulose, starch) were found in wheat husk (W) equal 42%, in rice husk 50% and in soft wood 42%, respectively. Thermal degradation characteristics, the bulk density, water absorption and the solubility index were also investigated. Wheat husk (W) and rice husk were found thermally stable at temperatures as low as 178 °C and 208 °C, respectively. The particle morphology and particle size were investigated using microscopy. Water absorption properties of the fibres were studied to evaluate the viability of these fibres as reinforcements. Polypropylene composites were fabricated using a high speed mixer and an ensuing injection moulding process with 40 wt% fibre. The tensile and Charpy impact strength of the resulting composites were investigated. The tensile elongation at break was found to 75% for wheat husk (W) composites and 23% for rice husk composites better than soft wood composites. Rice husk composites showed 13% better Charpy impact strength than soft wood composites. Due to coupling agent, tensile strength of composites found to improve 25% for soft wood, 35% for wheat husk (W) and 45% for rice husk.     

茶多糖对氟离子的吸附特性研究

为研究茶多糖对氟的吸附特性,分析了不同温度、不同加氟量条件下,多糖吸附氟的能力,并对多糖吸附氟的等温吸附模型进行了拟合,分析了多糖结构和组成可能对吸附氟的影响。结果表明:温度对多糖结合氟的影响较大,40℃下多糖表面空松,吸附氟的能力最强,随着温度的升高,多糖表面逐渐变得致密,结合氟的能力下降,温度高于70℃后,多糖吸附氟量又会有所增加;40℃下,随着氟添加量的增加,多糖吸附氟量增加,当添加量达到多糖量1.8倍后,多糖吸附氟量不再增加。多糖吸附氟符合Langmuir等温吸附模型,分配因子RL均大于0小于1,属于有利的吸附。粗多糖脱蛋白脱色后,结构和组成发生较大变化,表面变得光滑平整,F~-、Al~(3+)、Mn~(2+)和Fe~(3+)的含量都急剧下降,吸附氟的能力也下降。说明多糖吸附氟的能力与多糖的组成、结构有关,蛋白质及Mn~(2+)、Fe~(3+)、Al~(3+)在多糖结合氟中起到较重要作用。     

The reinforcement effect of carbon fiber on the friction and wear properties of carbon fiber reinforced PA6 composites

The tribological performance of PA6 and carbon fiber reinforced polyamide 6 (CF/PA6) under dry sliding condition was examined. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyamide 6 composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. The worn surface morphologies of neat PA6 and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. Moreover, all filled polyamide 6 have superior tribological characteristics to unfilled polyamides 6. The optimum wear reduction was obtained when the content of carbon fiber is 20 vol%.     

Mechanical properties of flax-g-poly(methyl acrylate) reinforced phenolic composites

In order to develop composites with better mechanical properties and environmental performance, it becomes necessary to increase the hydrophobicity of the natural fibers and to improve the interface between matrix and natural fibers. Graft copolymerization of natural fibers is one of the best methods to attain these improvements. Only few workers have reported the use of graft copolymers as reinforcing material in the preparation of composites. So in the present paper, we report the preparation of graft copolymers of flax fibers with methyl acrylate (MA) using Fenton’s reagent (FAS-H₂O₂) as redox system. Synthesized flax-g-poly(MA) was characterized with FTIR, TGA/DTA, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. Composites were prepared using flax-g-poly(MA) as a reinforcement and phenolformaldehyde (PF) as the binding material. Mechanical properties of phenol-formaldehyde composites were compared and it has been found that composites reinforced with flax-g-poly(MA) showed improvement in mechanical properties. Composites reinforced with flax-g-poly(MA) showed better tensile strength (235 N) and compressive strength (814 N) in comparison to composites reinforced with original flax fiber which showed lesser tensile strength (162 N) and compressive strength (372 N). Composites reinforced with flax-g-poly(MA) shows the improved MOR, MOE, and SP.