Biodegradability of nonwoven flax fiber reinforced polylactic acid biocomposites

Biocomposites of flax reinforced polylactic acid (PLA) were made using a new technique incorporating an air‐laying nonwoven process. PLA and flax fibers were mixed and converted to the webs in the air‐laying process. Prepregs were then made from the fiber webs by thermal consolidation. The prepregs were finally converted to composites by compression molding. This study was investigated the biodegradability and water absorption properties of the composites. The composites were incubated in compost under controlled conditions. The percentage weight loss and the reduction in mechanical properties of PLA and biocomposites were determined at different time intervals. It was found that with increasing flax content, the mechanical properties of the biocomposites decreased more during the burial trial. The increasing of flax content led to the acceleration of weight loss due to preferential degradation of flax. This was further confirmed by the surface morphology of the biodegraded composites from scanning electron microscope image analysis. Morphological observations indicated severe disruption of biocomposites structure between 60 and 120 days of incubation. POLYM. COMPOS., 35:2094–2102, 2014. © 2014 Society of Plastics Engineers     

Effect of nanoclay on physical,mechanical, and microbial degradation of jute‐reinforced,soy milk‐based nano‐biocomposites

Jute‐reinforced, soy milk‐based nano‐biocomposites were fabricated using both natural and organically modified nanoclay to study their effect on physical, mechanical, and degradation properties. Different weight percentages of nanoclays were used to modify soy milk by solution casting process. The jute fibers were then impregnated in modified soy resin and compressed to fabricate nano‐biocomposites. About 5 wt% of organically modified nanoclay‐loaded jute composite showed maximum tensile and flexural strength. X‐ray diffraction and transmission electron microscopy (TEM) analysis of fabricated composites confirmed about the formation of nanostructure. Impact, microhardness, dynamic mechanical analysis results of nano‐biocomposites revealed that nanoclay has influenced to improve such physical and mechanical properties. Microbial degradation study of nano‐biocomposites was carried out in cultured fungal bed. Weight loss, tensile loss, and field emission scanning electron microscopy photographs of composites revealed that composites are biodegradable in nature. The prime advantages of these composite are their eco‐compatibility as jute and soy resin, the basic constituents of composites are biodegradable in nature. These composites can be utilized in automobile, packaging, furniture sectors by replacing nondegradable plastic‐based composite. POLYM. ENG. SCI., 54:345–354, 2014. © 2013 Society of Plastics Engineers     

Thermal and Structural Analysis of Natural Fiber Reinforced Starch-Based Biocomposites

This is the second part of a series of articles dealing with characterization of starch based biodegradable composites. Potato, sweet potato, and corn starch varieties were used as matrices of the biocomposites. Natural fibers including jute, sisal, and cabuya were used as discrete reinforcement. Water and glycols were used as plasticizers. Compression molded specimens were prepared and characterized by a variety of techniques. Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA) were used to characterize the thermal behavior of these composites. Processed specimens did not show the typical endothermic peak observed in DSC scans for native starch powder. No significant difference was observed for weight loss and decomposition due to fiber or plasticizer content among the different specimens. Attenuated Total Reflectance–Infrared Spectroscopy (ATR-IR) was used to characterize the starch compounds and the effect of plasticizers and reinforcing fibers. The spectra found for most specimens were consistent with those of pure starch. Scanning electron microscopy (SEM) pictures showed the morphology of the specimens for different types of starch matrices and different fiber contents.     

Toward faster degradation for natural fiber reinforced poly(lactic acid) biocomposites by enhancing the hydrolysis-induced surface erosion

The poor and uncontrollable biodegradability of poly(lactic acid) (PLA)-based materials is one of the fundamental limitations for widening their applications. To regulate the degradation of PLA/ramie fiber biocomposites, the hydrophilicity of the composites was modified to attract more water attack by introducing water-soluble poly(ethylene glycol) (PEG). Analyses by characterization of sample size, weight loss and microstructure offered intensive information on the degradation behavior of PLA biocomposites. It was revealed that PEG indeed significantly enhanced the surface erosion process and thus facilitated the degradation rate. The biocomposite bar containing 15 wt% PEG completed degradation within 50 days, while only ~50 wt% mass lost for the control biocomposite sample without PEG. Morphological observation confirmed that PEG accelerated the penetration of outside water from the surface to the center driven by the diffusion-in process, which subsequently boosted the hydrolytic action of the PLA backbone ester groups. Our results indicated that the PEG induced water penetration governed the overall degradation kinetics. As a strong response to the degradation, the stiffness of the biocomposite bars suffered from drastic decrease while T _g varied in a climbing trend within the early stage. Microscopic examination of degradation solution formed during hydrolytic degradation of the PLA biocomposites suggested oligomers or lactic acid monomers were released to the solutions. It was of great interest to observe PEG dissolved in the alkaline solution speeded the ramie fibers breaking down to tiny fragments and cellulose macromolecules which further regenerated into cellulose aggregates in various fantastic appearances like coral-like leaves and pine needles. Our success in regulating the degradation of PLA biocomposites also provides an instructive approach for other PLA based materials.

Alkaline treatment of diacetate fibers and subsequent cellulase degradation

The work investigated the degradation behavior of cellulose acetate (CA) fibers in NaOH solutions in heterogeneous conditions and the effect of alkaline treatment on cellulase degradation of CA fibers. Weight analysis and IR spectra showed that the weight loss of CA fibers immersed in NaOH solution chiefly depended on acetylation. Alkaline treatment promoted the degradation of CA fibers in cellulase solution by reason of deacetylation, especially when the degree of substitution (DS) of CA fibers reached 0.8, cellulase degradation increased most markedly. SEM revealed a smooth surface except some thin holes in the CA fibers after immersion in NaOH solution with a lower concentration because of the formation of alkaline cellulose, and only in a higher concentration such as 5.0N, it could be observed that microfibers perpendicular to fiber axis distributed over the surfaces of the fibers. ¹NMR spectra suggested that only in a lower NaOH concentration (≤0.25N), deacetylation reaction was affected by the reactivities of ester groups at position 2, 3, and 6 in anhydroglucose unit, but did not follow the theoretical trend in the three positions. Moreover, the DS for polymer molecules in CA fibers were dispersive after alkaline treatment in heterogeneous condition and the DS of the product increased during sequent cellulase degradation. This was also demonstrated by the result of IR analysis and X‐ray diffraction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Combinatorial design of hydrolytically degradable,bone-like biocomposites based on PHEMA and hydroxyapatite

With advantages such as design flexibility in modifying degradation, surface chemistry, and topography, synthetic bone-graft substitutes are increasingly demanded in orthopedic tissue engineering to meet various requirements in the growing numbers of cases of skeletal impairment worldwide. Using a combinatorial approach, we developed a series of biocompatible, hydrolytically degradable, elastomeric, bone-like biocomposites, comprising 60 wt% poly(2-hydroxyethyl methacrylate-co-methacrylic acid), poly(HEMA-co-MA), and 40 wt% bioceramic hydroxyapatite (HA). Hydrolytic degradation of the biocomposites is rendered by a degradable macromer/crosslinker, dimethacrylated poly(lactide-b-ethylene glycol-b-lactide), which first degrades to break up 3-D hydrogel networks, followed by dissolution of linear pHEMA macromolecules and bioceramic particles. Swelling and degradation were examined at Hank's balanced salt solution at 37 °C in a 12-week period of time. The degradation is strongly modulated by altering the concentration of the co-monomer of methacrylic acid and of the macromer, and chain length/molecular weight of the macromer. 95% weight loss in mass is achieved after degradation for 12 weeks in a composition consisting of HEMA/MA/Macromer = 0/60/40, while 90% weight loss is seen after degradation only for 4 weeks in a composition composed of HEMA/MA/Macromer = 27/13/60 using a longer chain macromer. For compositions without a co-monomer, only about 14% is achieved in weight loss after 12-week degradation. These novel biomaterials offer numerous possibilities as drug delivery carriers and bone grafts particularly for low and medium load-bearing applications.     

Study of compostable behavior of jute nano fiber reinforced biocopolyester composites in aerobic compost environment

Jute nano fiber (JNF) reinforced biocopolyester‐based composite sheets were prepared with 2% and 10 wt % filler loading and compostability tests were performed in simulated aerobic compost environment at ambient temperature for a period of 50 days. Weight loss study revealed that the incorporation of JNF enhanced the rate of degradation significantly. The unreinforced sample exhibited a steady loss in weight, whereas, the JNF reinforced samples showed three phase degradation. They had a steady weight loss up to 30 days followed by a plateau zone between 30 and 40 days and after that, there was again an increase in weight loss up to 50 days. The biodegraded samples were investigated for their change in molecular weight by Gel Permeation Chromatography (GPC). The change in structure was examined by Differential Scanning Calorimetry (DSC) and morphological change was observed by Scanning Electron Microscopy (SEM). Molecular weight study revealed the fact that Biocopolyester molecules had a significant breakdown in chain length during melt mixing with 10 wt % JNF, which was much less predominant in 2 wt % JNF loaded composites. Such a decrease in chain length and presence of 10 wt % JNF might have facilitated the biodegradation process resulting in highest weight loss. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of pseudomonas lipase enzyme on the degradation of polycaprolactone/polycaprolactone-polyglycolide fiber blended nanocomposites

This study describes the interaction resulting from adding pseudomonas lipase (PS) enzyme to polycaprolactone-based composites designed for orthopedic applications. The biopolymer composite evaluated in this study consists of electrospun polycaprolactone (PCL)/polyglycolide (PGA) blended fibers impregnated with double stranded deoxyribonucleic acid wrapped single-walled carbon nanotubes encapsulated by a PCL matrix. PS enzyme was used to catalyze the degradation of PCL-based biocomposites. PCL present in the biocomposites showed considerable degradation in 4 weeks in the presence of the enzyme, exhibiting a contrast to hydrolytic degradation which lasts several years. PGA-consisting fibers degraded completely within one week of exposure to the enzyme.     

Formulation‐properties versatility of wood fiber biocomposites based on polylactide and polylactide/thermoplastic starch blends

This article discusses the interrelation between formulation, processing, and properties of biocomposites composed of a bioplastic reinforced with wood fibers. Polylactide (PLA) and polylactide/thermoplastic starch blends (PLA/TPS) were used as polymeric matrices. Two grades of PLA, an amorphous and a semicrystalline one, were studied. TPS content in the PLA/TPS blends was set at 30, 50, and 70 wt%. Two types of wood fiber were selected, a hardwood (HW) and a softwood (SW), to investigate the effect of the fiber type on the biocomposite properties. Finally, the impact of different additives on biocomposite properties was studied with the purpose to enhance the bioplastic/wood fiber adhesion and, therefore, the final mechanical performance. The biocomposites containing 30 wt% of wood fibers were obtained by twin‐screw extrusion. The properties of the biocomposites are described in terms of morphology, thermal, rheological, and mechanical properties. Furthermore, the biocomposites were tested for humidity and water absorption and biodegradability. An almost 100% increase in elastic modulus and 25% in tensile strength were observed for PLA/wood fiber biocomposite with the best compatibilization strategy used. The presence of the TPS in the biocomposites at 30 and 50 wt% maintained the tensile strength higher or at least equal as for the virgin PLA. These superior tensile results were due to the inherent affinity between the matrices and wood fibers improved by the addition of a combination of coupling and a branching agent. In addition to their outstanding mechanical performance, the biocomposites showed high biodegradation within 60 days. POLYM. ENG. SCI., 54:1325–1340, 2014. © Her Majesty the Queen in Right of Canada 2013 ¹      

Effect of surface treatments of banana fiber on mechanical,thermal, and biodegradability properties of PLA/banana fiber biocomposites

Poly lactic acid (PLA)/Banana fiber (BF) biocomposites were fabricated employing melt blending technique followed by compression molding. BF were surface‐treated by NaOH and various silanes viz. 3‐aminopropyltriethoxysilane (APS) and bis‐(3‐triethoxy silyl propyl) tetrasulfane (Si69) to improve the compatibility of the fibers within the matrix polymer. Mechanical tests revealed an increase of tensile strength to the tune 136% and impact strength to 49% as compared with the untreated biocomposite. Thermal properties of the composites have been evaluated using DSC and TGA. DSC thermograms revealed an increase in the melting transitions thus revealing effective fiber/matrix interface. The thermal stability in the biocomposites also increased in case of banana fiber treated with Si69. Viscoelastic measurements using DMA confirmed an increase of storage modulus and low damping values in the silane treated biocomposites. Biodegradation studies in the biocomposites have been investigated in B. cepacia medium through morphological and weight loss studies. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Biodegradable composites based on starch/EVOH/glycerol blends and coconut fibers

Unripe coconut fibers were used as fillers in a biodegradable polymer matrix of starch/ethylene vinyl alcohol (EVOH)/glycerol. The effects of fiber content on the mechanical, thermal, and structural properties were evaluated. The addition of coconut fiber into starch/EVOH/glycerol blends reduced the ductile behavior of the matrix by making the composites more brittle. At low fiber content, blends were more flexible, with higher tensile strength than at higher fiber levels. The temperature at the maximum degradation rate slightly shifted to lower values as fiber content increased. Comparing blends with and without fibers, there was no drastic change in melt temperature of the matrix with increase of fiber content, indicating that fibers did not lead to significant changes in crystalline structure. The micrographs of the tensile fractured specimens showed a large number of holes resulting from fiber pull‐out from the matrix, indicating poor adhesion between fiber and matrix. Although starch alone degraded readily, starch/EVOH/glycerol blends exhibited much slower degradation in compost. Composites produced 24.4–28.8% less CO₂ compared with starch in a closed‐circuit respirometer. Addition of increasing amount of fiber in starch/EVOH/glycerol composite had no impact on its biodegradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Degradability in a natural compost medium of (linear low‐density polyethylene)/(soya powder) blends compatibilized with epoxidized natural rubber

The objective of this study was to investigate the degradability of linear low‐density polyethylene (LLDPE)/(soya powder) blends. The blends were compatibilized by epoxidized natural rubber with 50 mol% of epoxidation. They were exposed to a natural compost medium located in northern Malaysia. The degradability was evaluated by using tensile tests, a morphological study, carbonyl indices, crystallinity measurements, weight loss, and molecular‐weight changes. The tensile strength and elongation at break of the compatibilized blends decreased during one year of exposure. The colonization of fungus and the formation of pores were observed in micrographs. The carbonyl indices, crystallinity, and weight loss increased during exposure, thereby indicating the degradation of the blends. The reduction in molecular weight revealed the degradation of the LLDPE upon composting. Surprisingly, after composting, the compatibilized blends showed more degradation than the uncompatibilized ones. J. VINYL ADDIT. TECHNOL., 20:42–48, 2014. © 2014 Society of Plastics Engineers     

Degradation of polyethylene–starch blends in soil

Binary polymer films containing different percentages of corn starch and low-density polyethylene (LDPE) were exposed to soils over a period of 8 months and monitored for starch removal and chemical changes of the matrix using FTIR spectroscopy. A standard curve using the area of the C? O stretch band and an empirical second-degree polynomial to fit the data made it possible to calculate starch concentration over a wide range (0–46% by mass). Starch removal was found to proceed rapidly during the first 40 days and to nearcompletion in very high starch blends (52% and 67% by weight). Starch removal was slower, consisting of mostly surface removal in 29% starch blends. Weight loss data supported spectroscopic data showing similar gross features. Weight loss and spectroscopic data were consistent with percolation theory and suggested that starch removal continues past 240 days. Degradation rates in different soils containing different amounts of organic matter were approximately the same after a period of a few weeks. IR analysis did not show significant chemical changes in the polyethylene matrix after 240 days. However, the matrix did show evidence of swelling, an increase in surface area, and removal of low molecular weight components.     

Comparison of dynamic and static degradation of poly(vinyl chloride)

The thermal degradation of PVC was measured under dynamic and static conditions. The UV and IR spectra, as well as the molecular weight distribution of the PVC samples, taken after different time intervals were measured. It was established that during the dynamic PVC degradation, performed in a mixing chamber, two stages with different degradation rates can be distinguished both in extinction and torque vs. time curves. While oxygen does not, dissolved HCl does play an important role in the dynamic degradation: HCl steps into reaction with the formed polyenes and has a catalytic action. The chemical degradation, particularly the crosslinking, produces the changes in the rheological behavior of the material. Results were compared with those obtained under static conditions in argon, air, and HCl atmosphere.     

Biodegradability and improved mechanical performance of polyhydroxyalkanoates/agave fiber biocomposites compatibilized by different strategies

In this work, biocomposites made of polyhydroxyalkanoates (PHA) with natural fibers were produced via compression molding. In particular, polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV) were reinforced with 20 wt% of agave fibers. Different compatibilization strategies were investigated to improve the fiber-matrix interaction: fiber surface treatment in PHA solution, fiber surface treatment in maleated PHA solution, fiber propionylation, and extrusion with maleated PHA. The biocomposites were characterized in terms of morphology, mechanical properties, water absorption, and biodegradability by CO₂ production tracking. In general, fiber propionylation was the best strategy for mechanical properties enhancement and water uptake decreasing. Biocomposites with propionylated fibers showed improved flexural strength (170% for PHB and 84% for PHBV). The flexural modulus was also enhanced with propionylated fibers up to 19% and 18% compared to uncompatibilized biocomposites (PHB and PHBV, respectively). Tensile strength increased by 16% (PHB) and 14% (PHBV), and the water absorption was reduced using propionylated fibers going from 6.6% to 4.4% compared with biocomposites with untreated fibers. Most importantly, the impact strength was also improved for all biocomposites by up to 96% compared with the neat PHA matrices. Finally, it was found that the compatibilization did not negatively modify the PHA biodegradability.     

Photocuring of Empty Fruit Bunches of Oil Palm (Elaeis guineensis) Fibers with Allyl Methacrylate (AMA): Effect of Additives on Mechanical and Degradable Properties

Empty fruit bunches of oil palm fibers can be used as environmentally friendly alternatives to conventional reinforcing fibers, like glass, carbon, etc. In order to improve the interfacial properties, this fiber was subjected to grafting with bulk monomer allyl methacrylate (AMA) and cured under UV radiation. It was found that UV curing enhanced the physicomechanical properties to a large extent compared to the untreated virgin fiber. Among different AMA concentration, the fibers treated with 10% monomer showed the best mechanical properties after 15 passes of UV radiation. Different additives such as urea, acrylamide, and NVP were added with the 10% AMA solution, and the effect of additives was studied. It was found that fibers treated with 2% urea showed even better PL and tensile properties than those treated only with AMA. the treated and untreated fiber samples were also subjected to various weather conditions such as simulating weather, soil, and water aging to determine the degradable properties. It was observed that the minimum loss in each case was shown by the sample treated with the formulations that contain urea as additives with AMA and that fiber aged in soil showed higher loss of weight and tensile properties than that aged in water.     

静电纺PLGA纤维膜的体外降解性能研究

采用静电纺丝制备了聚乳酸-乙酵酸（PLGA）纤维膜,通过失重率、相对分子质量变化、断裂强度测试、SEM、DTA和X-射线衍射等方法详细研究了静电纺PLGA纤维膜的降解性能。结果证明：PLGA纤维膜可在磷酸酯（PBS）溶液中降解,降解前两周相对分子质量和断裂强度快速下降,失重率快速提高;降解4w时纤维发生断裂;10w时纤维大部分断裂崩解成小碎粒;降解前后静电纺PLGA纤维膜始终为无定形聚合物。     

Fabrication of acrylic modified coconut fiber reinforced polypropylene biocomposites: Study of mechanical,thermal, and erosion properties

Coconut shell fiber‐reinforced polypropylene (PP/CSP) biocomposites were prepared by using hand lay‐out technique with different fractions of the modified fibers. Before proceeding to fabrication method, fibers were made compatible by chemical modification with acrylic acid. The interaction of acrylic modified coconut shell fibers with PP matrix was studied by using Fourier transforms Infrared spectroscopy. The morphology of chemically modified coconut fibers and coconut shell fibers reinforced polypropylene biocomposites were studied by using field emission scanning electron microscope. Due to strong interfacial interaction between PP and CSP, mechanical properties were improved. It was found that the tensile strength, elongation at break and loss modulus, rigidity of PP bio‐composites were investigated as compared with that of virgin PP matrix. The thermal properties of the fabricated biocomposites were investigated by using thermogravimetric analysis. The semi‐ductile properties of the fabricated PP biohybrids were confirmed through erosion ring test. POLYM. COMPOS., 38:2852–2862, 2017. © 2015 Society of Plastics Engineers     

Assessing the influence of cotton fibers on the degradation in soil of a thermoplastic starch‐based biopolymer

Biocomposites consisting of cotton fibers and a commercial starch‐based thermoplastic were subjected to accelerated soil burial test. Fourier transform infrared (FTIR) spectrometry analysis was carried out to provide chemical–structural information of the polymeric matrix and its reinforced biocomposites. The effects that take place as a consequence of the degradation in soil of both materials were studied by FTIR‐ATR, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). When the polymeric matrix and the reinforced biocomposite are submitted to soil burial test, the infrared studies display a decrease in the CO band associated to the ester group of the synthetic component as a consequence of its degradation. The crystalline index of both materials decreased as a function of the degradation process, where the crystalline structure of the reinforced biocomposite was the most affected. In accordance, the degraded reinforced biocomposite micrographs displayed a more damaged morphology and fracture surface than the degraded polymeric matrix micrographs. On the other hand, the same thermal decomposition regions were assessed for both materials, regardless of the degradation time. Kissinger, Criado, and Coats‐Redfern methods were applied to analyze the thermogravimetric results. The kinetic triplet of each thermal decomposition process was determined for monitoring the degradation test. The thermal study confirms that starch was the most biodegradable polymeric matrix component in soil. However, the presence of cotton fiber modified the degradation rate of both matrix components; the degradability in soil of the synthetic component was slightly enhanced, whereas the biodegradation rate of the starch slowed down as a function of the soil exposure time. POLYM. COMPOS., 31:2102–2111, 2010. © 2010 Society of Plastics Engineers     

Effect of electron beam radiation on the performance of biodegradable Bionolle-jute composite

To study the radiation effect on the physical, thermal, mechanical and degradable properties of biodegradable polymer Bionolle (chemosynthetic polyester poly(1,4-butylene succinate)), Bionolle films prepared by compression molding process and were irradiated with electron beam (EB) radiation of different doses. Gel content was found to increase with increase of radiation dose. Tensile strength of Bionolle was enhanced when Bionolle film was exposed under 20 kGy radiation. The loss of tensile strength of both unirradiated and irradiated Bionolle is 70% and 8% due to thermal aging at 70°C for 30 days. Both irradiated and unirradiated films of Bionolle were subjected to different degradation test in compost (soil burial), enzyme and storage degradation both in outdoor and indoors conditions. The loss of weight due to soil (compost) degradation test decreased with increase of radiation dose. The loss of weights of irradiated samples were found to be very less within the first three months of compost degradation. After 120 days, tensile strength of the Bionolle films irradiated at 20 kGy and 100 kGy were 68 MPa and 40 MPa, respectively, compared to the value (30 MPa) of the unirradiated Bionolle samples. Loss of tensile strength of irradiated Bionolle due to storage degradation like in roof, ground and indoors was minimum compared to unirradiated Bionolle. The weight loss due to enzymatic degradation was found to be decreased with increase of radiation dose. The tensile strength of jute reinforced Bionolle composites (23 wt.-% jute content) irradiated at 20 kGy was found to be higher (22%) than that of an unirradiated composite.