Evaluation of Poly(lactic acid) and Sugar Beet Pulp Green Composites

Poly(lactic acid) (PLA) and sugar beet pulp (SBP) were compounded by twin-screw extrusion and injection molded into composite forms. Specific mechanical energy decreased with the addition of SBP during processing. PLA–SBP composites retained more tensile strength than expected based on the Nicolais–Narkis model especially at high levels of SBP suggesting adhesion between SBP and PLA. The thermal characteristics of PLA were not affected by thermo-mechanical processing or by the incorporation of SBP up to 30% weight basis. PLA and PLA–SBP composites had similar tensile properties to other thermoplastic resins and may be used as a cost-competitive replacement.

Mechanical Property Characterization of Plasticized Sugar Beet Pulp and Poly(Lactic Acid) Green Composites Using Acoustic Emission and Confocal Microscopy

Sorbitol and glycerol were used to plasticize sugar beet pulp-poly(lactic acid) green composites. The plasticizer was incorporated into sugar beet pulp (SBP) at 0%, 10%, 20%, 30% and 40% w/w at low temperature and shear and then compounded with poly(lactic acid) (PLA) using twin-screw extrusion and injection molding. The SBP:PLA ratio was maintained at 30:70. As expected, tensile strength decreased by 25% and the elongation increased. Acoustic emission (AE) showed correlated debonding and fracture mechanisms for up to 20% w/w plasticizer and uncorrelated debonding and fracture for 30–40% sorbitol and 30% glycerol content in SBP–PLA composites. All samples had a well dispersed SBP phase with some aggregation in the PLA matrix. However, at 40% glycerol plasticized SBP–PLA composites exhibited unique AE behavior and confocal microscopy revealed the plasticized SBP and PLA formed a co-continuous two phase system.

Life Cycle Assessment of Polysaccharide Materials: A Review

Apart from conventional uses of polysaccharide materials, such as food, clothing, paper packaging and construction, new polysaccharide products and materials have been developed. This paper reviews life cycle assessment (LCA) studies in order to gain insight of the environmental profiles of polysaccharide products (e.g. viscose or natural fibre polymer composites) in comparison with their conventional counterparts (e.g. cotton or petrochemical polymers). The application areas covered are textiles, engineering materials and packing. It is found that for each stage of the life cycle (production, use phase and waste management) polysaccharide-based end products show better environmental profiles than their conventional counterparts in terms of non-renewable energy use (NREU) and greenhouse gas (GHG) emissions. Cotton is an exception, with high environmental impacts that are related to the use of fertilisers, herbicides, pesticides and high water consumption. The available literature for man-made cellulose fibres shows that they allow to reduce NREU and GHG emissions in the fibre production phase. No study has been found for the fabric production and the use phase of man-made cellulose textiles.

Biopolymers in the Existing Postconsumer Plastics Recycling Stream

The existing plastic bottle reclaiming industry has working technology, satisfied customers, raw material, and investors. Adding new materials to the current mix requires satisfying all four needs for those materials. Rigid plastic container recycling focuses on high-density polyethylene (HDPE) and polyethylene terephthalate (PET) bottles, the overwhelming percentage of bottles sold in North America. Bottles of other resins, including polyvinyl chloride (PVC), polypropylene and biopolymers, lack critical mass necessary for independent reclamation. To be mechanically recycled, biopolymers must be either completely fungible with existing recycled resins or be available in sufficient quantity to achieve the needed critical mass. So far, biopolymer volume projections are not encouraging. Biopolymers, like all minor bottle resins, must pay their own way in sorting and processing without subsidy from PET and HDPE recycling. Based on limited data, some biopolymers may have little effect on recycled HDPE performance, but will represent a yields loss and added economic burden at some level of occurrence. Biopolymers have not been shown to be compatible with PET and likely will represent performance problems and economic burdens at even low levels of occurrence. Applications for biopolymers should be carefully selected so as to not interfere with currently recycled materials unless critical mass can be achieved quickly.

Performance and Environmental Impact of Biodegradable Films in Agriculture: A Field Study on Protected Cultivation

The performance, the degradability in soil and the environmental impact of biodegradable starch-based soil mulching and low tunnel films were assessed by means of field and laboratory tests. The lifetime of the biodegradable mulches was 9 months and of the biodegradable low-tunnel films 6 months. The radiometric properties of the biodegradable films influenced positively the microclimate: air temperature under the biodegradable low tunnel films was 2 °C higher than under the low density polyethylene films, resulting in an up to 20% higher yield of strawberries. At the end of the cultivation period, the biodegradable mulches were broken up and buried in the field soil together with the plant residues. One year after burial, less than 4% of the initial weight of the biodegradable film was found in the soil. According to ecotoxicity tests, the kinetic luminescent bacteria test with Vibrio fischeri and the Enchytraeus albidus ISO/CD 16387 reproduction potential, there was no evidence of ecotoxicity in the soil during the biodegradation process. Furthermore, there was no change in the diversity of ammonia-oxidizing bacteria in the soil determined on the basis of the appearance of amoA gene diversity in denaturing gradient gel electrophoresis.     

Preparation of Chitin/Cellulose Films Compatibilized with Polymeric Ionic Liquids

This paper reports the preparation of chitin/cellulose films compatibilized with polymeric ionic liquids. In-situ (co)polymerization of polymerizable ionic liquids, 1-(3-methacryloyloxypropyl)-3-vinylimidazolium bromide (1) and 1-methyl-3-vinylbenzylimidazolium chloride (3), was carried out in the presence of a radical initiator, AIBN, in the chitin/cellulose solution with ionic liquid solvents (1-butyl-3-methylimidazolium acetate and chloride, BMIMOAc and BMIMCl, respectively), followed by the appropriate procedure to give the desired films. The presence of the polymeric ionic liquid in the film was confirmed by the IR measurement. The powder X-ray diffraction analysis suggested that crystalline structures of the polysaccharides were largely disrupted in the film, as same as that of a chitin/cellulose film prepared by the AMIMOAc/BMIMCl system. These results were different from the XRD result of a chitin/cellulose film prepared by the 1-allyl-3-methylimidazolium bromide/BMIMCl system reported in our previous study, in which some crystalline structures were still remained in the film. Furthermore, the mechanical properties of the present films were evaluated by tensile testing, which were affected by the molar ratios of the polymeric ionic liquids to the polysaccharides and the compositional ratios of the two units 1 and 3.     

An Overview on the Mechanical Behaviour of Biodegradable Agricultural Films

The mechanical behavior of various types of biodegradable materials depends, mainly, on their chemical composition and the application conditions. Various additives are added into the bioblends to improve their properties, which sometimes even reach the levels of the conventional plastics. It is well known that the environmental conditions during production, storage, and usage of these materials influence their mechanical properties. Ageing during the useful lifetime also causes great losses in the elongation. In the present paper, the overall mechanical behavior of biodegradable films, which may be considered suitable for agricultural applications, but also of partially biodegradable films, is reviewed and analyzed. Selected critical mechanical properties of films before their exposure to biodegradation are investigated and compared against those of conventional agricultural films.     

The influence of soil macroinvertebrates on primary biodegradation of starch-containing polyethylene films

The primary biodegradability of polyethylene (PE) films containing different percentages of cornstarch (0–50%) and other additives (prooxidant, oxidized polyethylene) was tested using four species of earthworms (Eisenia fetida, Lumbricus terrestris, Aporectodea trapezoides, Aporectodea tuberculata), three species of cockroaches (Periplaneta americana, Blaberus sp.,Blattella germanica), termites (Reticulotermes flavipes), sowbugs (Porcellio laevis), and crickets (Acheta domesticus). These studies were conducted to elucidate the potential role of soil macroinvertebrates in degrading starch/PE biodegradable plastics. The results of the macroinvertebrate bioassays indicate that crickets, cockroaches, and sowbugs consumed starch-containing PE films most readily. In addition, the degree to which the films were attacked and consumed was directly related to the starch content of the film. Films with oxidized polyethylene and those containing prooxidant (vegetable oil and a transition metal catalyst) were also consumed. None of the four species of earthworms tested or the termites showed any activity toward the starch/polyethylene films. These results have important implications for determining the fate of novel plastic formulations which claim to be biodegradable in natural environments. Studies such as these, coupled with studies on microbial degradation, will help provide the type of information needed to assess the environmental fate of biodegradable starch/PE plastics and fill the voids in the scientific database regarding this rapidly developing field.     

Development of Regenerated Cellulose/Citric Acid Films with Ionic Liquids

Nowadays, the importance of green and biodegradable plastics as viable substitutes for non-degradable petroleum-based materials is felt more than ever. Regenerated cellulose (RC) as a potential candidate suffers from poor processability and inferior properties, limiting its wide applications. In this study, it is demonstrated that citric acid (CA) enhances physical, mechanical, and thermal properties of RC films, due to RC-citric acid compatibility. 1-ethyl-3-methylimidazolium chloride (EMIMCl) as a green ionic liquid was employed for the processing of RC. The optimum properties in terms of thermal stability, mechanical strength, contact angle, water uptake, and oxygen permeability were achieved at 10 wt% of CA. However, further incorporation of CA adversely affected the film properties. This behaviour was explained by the crosslinking and plasticizing effects of CA. Furthermore, in vitro cytotoxicity test demonstrated that RC/CA films are cytocompatible, suggesting the potential advantage of using these biopolymeric films for biomaterial and biological applications.

     

Physical properties and biodegradability of blends containing poly(ε-caprolactone) and tropical starches

In order to assess feasibility of tropical starches (sago and cassava starches) as biodegradable plastic materials, blending with poly(-caprolactone) (PCL), a biodegradable polymer, was carried out. It was confirmed that the physical properties (tensile strength and elongation) of PCL/sago and PCL/cassava blends were similar to those of PCL/corn blend, suggesting that sago and cassava starches can also be blended with PCL for production of biodegradable plastic. However, the properties of all PCL/starch blends were still low compared with those of polyethylene. Enzymatic degradability evaluation showed that lipase degradation of PCL and-amylase degradation of starch increased as the starch content in the blend increased. Burial test of the blends for 1, 3, and 5 months was carried out and the rate of degradation of the PCL/sago blend was confirmed to be slower than those of PCL/corn and PCL/cassava blends. Observation of the film blends structure by scanning electron microscope revealed that the starch was dispersed in a PCL continuous phase. Furthermore, changes in the film surface before and after enyzme treatments were observed.     

Effect of the Incorporation of Lysozyme on the Properties of Jackfruit Starch Films

Jackfruit starch based biodegradable films containing lysozyme were characterized for their antimicrobial activity, thickness, solubility, water vapor permeability and mechanical properties. The biodegradable films had good appearance and antimicrobial activity against Micrococcus lysodeikticus. The thickness of the biodegradable films were not affected by the variation in pH, but the addition of lysozyme increased the thickness, the thickest films being those with the highest lysozyme concentrations. The variation in pH of the filmogenic solutions affected the solubility of the biodegradable films, water solubility being greatest at pH 7.0 and with the highest lysozyme concentration. The permeability of the biodegradable films was increased by incorporating lysozyme. The lysozyme concentration and pH variation caused changes in the mechanical properties. The addition of 8% lysozyme increased the tensile strength and Young’s modulus for all the pH values studied. With respect to the release of antimicrobial activity, the diffusion of lysozyme was shown to follow Fickian transport mechanism.     

Preparation and Optimization of Starch/Poly Vinyl Alcohol/ZnO Nanocomposite Films Applicable for Food Packaging

Pollution and destruction of the environment due to the accumulation of non-degradable plastics are some of the most important concerns in the world. A significant amount of this waste is related to the polymers used in food packaging. Therefore, experts in the food industry have been looking for suitable biodegradable alternatives to synthetic polymers. Preparing biocompatible and biodegradable films based on starch is a good choice. In this study, various factors affecting films of starch/polyvinyl alcohol (PVA)/containing ZnO nanoparticles such as the amount of starch, PVA, glycerol, and ZnO were evaluated by response surface methodology (RSM). Film formation by solvent casting method, mechanical properties, swelling, solubility, and water vapor permeability (WVP) were selected as responses of RSM. The results showed that hydrogen bonding interactions between polyvinyl alcohol and starch improved the film formation. The effect of glycerol and PVA content on the mechanical strength was contrary to each other. As the amount of PVA increased, the tensile strength first decreased and then increased. The value of WVP was for all Runs from 0 to 6.77?×?10^??8 g m^??1 s^??1 Pa^??1. Finally, films with high film formation, maximum tensile strength, and high elongation at break, minimum solubility, permeability, and swelling were optimized.

     

Photodegradation of Poly(lactic acid) Stereocomplex by UV-Irradiation

Neat poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) films and PLLA/PDLA blend films were prepared by solution casting, and their photodegradation by UV-irradiation was investigated using wide-angle X-ray scattering (WAXS), gel permeation chromatography, differential scanning calorimetry, tensile testing, and polarized optical microscopy. The PLLA/PDLA blend film was more photodegradation-resistant than the neat PLLA and PDLA films when photodegradation was monitored by molecular weight, melting temperature, and WAXS crystalline peak positions. This indicates that the chains in both amorphous and crystalline regions of the PLLA/PDLA blend film were photo-cleavage-resistant compared to those of the neat PLLA and PDLA films. The changes in melting temperature and WAXS crystalline peak positions before and after photodegradation respectively indicated the increased crystalline lattice disorder and the decreased crystalline lattice sizes of the neat PLLA and PDLA films, whereas these changes were insignificant for the blend films. Photodegradation caused no significant change in tensile properties, with the exception of significant decreases in the tensile strength and elongation at break of PLLA/PDLA blend film. However, the tensile strength and elongation at break of the PLLA/PDLA blend film retained higher values compared to those of the neat PLLA and PDLA films during photodegradation. In spite of the slower photodegradation of the PLLA/PDLA blend film traced by M _n, T _m, and WAXS crystalline peak positions than that of neat PLLA and PDLA films, the rapid decrease in tensile strength and elongation at break of the former than that of the latter should be due to the highly-ordered structural difference between them, i.e., the three dimensional dry gel of the former and the spherulites of the latter.     

Mechanical Property and Biodegradability of Cast Films Prepared from Blends of Oppositely Charged Biopolymers

Biodegradable cast films of about 50 m thickness were fabricated by blending oppositely charged biopolymers such as anionic starch–chitosan, and cationic starch–pectin. The tensile strength and elongation at break (%) of films were evaluated as well as their capacity to degrade in compost. Films recovered from soil every 48 h showed consistent degradation (weight loss), diminution of the polymers characteristic peak absorbance in the carbohydrate fingerprint region of the FTIR, and changes in the surface morphology via scanning electron microscopy (SEM). Anionic starch–chitosan films had much superior tensile strength and elongation compared to cationic starch–pectin, suggesting that the ionic bonds formed between anionic-starch and positively charged groups in chitosan polymer were much more stable and stronger. Initially, both films lost about 36% weight within 96 h, which also correlated well with the loss in the characteristic absorption peaks in the region of the infrared spectrum typical of biopolymers. The total mineralization of films by microorganisms in compost soil was also measured using respirometric techniques. Though the rate of mineralization differed for two formulations, total mineralization (extent) for both films were achieved within 45 days.     

The Effect of Nanoclays on the Properties of PLLA-modified Polymers Part 1: Mechanical and Thermal Properties

Organically modified montmorillonite clays were incorporated at a 5% loading level into film grade of poly-L-lactic acid (PLLA) using a variety of masterbatches based on either semi-crystalline or amorphous poly-(lactic acid), as well as biodegradable aromatic aliphatic polyester. The PLLA masterbatches and compounded formulations were prepared using a twin screw compounding extruder, while the films were prepared using a single screw cast film extruder. The thermal and mechanical properties of the films were examined in order to determine the effect of the clay and different carriers on the polymer–clay interactions. In the optimal case, when a PLLA-based masterbatch was used, the tensile modulus increased by 30%, elongation increased by 40%, and the cold crystallization temperature decreased by 15 °C, compared to neat PLLA. The properties improvement of PLLA films containing nano clays demonstrated the possibility to extend the range of biodegradable film applications, especially in the field of packaging.     

Process,Characterization and Biodegradability of Aliphatic Aromatic Polyester/Sisal Fiber Composites

The biodegradability, morphology, and mechanical properties of composite materials made of Poly(butylene adipate-co-terephthalate) (PBAT) and sisal fiber (SF) were evaluated. Composites containing acrylic acid-grafted PBAT (PBAT-g-AA/SF) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of SF in the PBAT-g-AA matrix was highly homogeneous as a result of ester formation between the carboxyl groups of PBAT-g-AA and hydroxyl groups in SF and the consequent creation of branched and cross-linked macromolecules. Each composite was subjected to biodegradation tests in Rhizopus oryzae compost. Morphological observations indicated severe disruption of film structure after 60 days of incubation, and both the PBAT and the PBAT-g-AA/SF composite films were eventually completely degraded. Water resistance of PBAT-g-AA/SF was higher than that of PBAT/SF, although weight loss of composites buried in Rhizopus oryzae compost indicated that both were biodegradable, even at high levels of SF substitution. The PBAT-g-AA/SF films were more biodegradable than those made of PBAT, implying a strong connection between these characteristics and biodegradability.     

Cellulose acetate biodegradability upon exposure to simulated aerobic composting and anaerobic bioreactor environments

Cellulose acetate (CA) films with degree of substitution (d.s.) values of 1.7 and 2.5 were exposed to biologically active in-laboratory composting test vessels maintained at approximately 53 °C. The CA 1.7- and 2.5-d.s. films (thickness values of 0.5–1.0 and 2.0 mil, respectively) had completely disappeared by the end of 7- and 18-day exposure time periods in the biologically active bioreactors, respectively. The relatively small CA film weight loss observed in the poisoned control test vessels allows the conclusion that CA film erosion during the composting exposures resulted, at least in part, from biologically mediated processes. Under strictly anaerobic conditions, an active methanogenic inoculum was developed by acclimation of a sewage sludge to a synthetic municipal solid waste (SMSW) mixture at 42°C. The CA 1.7-d.s. film samples (0.5- to 1.0-mil thickness) were exposed in anaerobic serum bottles containing a 25% solids loading of SMSW in which methanogenic activity was rapidly established after introducing of the developed inoculum. For exposures of 30 days only small visually distinguishable fragments of the CA 1.7-d.s. films were recovered. In contrast, exposure of the CA 1.7-d.s. film to a poisoned control test vessel resulted in negligible weight loss. Therefore, degradation of the CA 1.7-d.s. films upon exposure to the anaerobic bioreactors was due, at least in part, to biologically mediated processes.Guest Editor: Dr. Graham Swift, Rohm & Haas.     

Miscibility and Biodegradability of Poly(Butylene Succinate)/Poly(Butylene Terephthalate) Blends

As one of the biodegradable polymers, the blend of poly(butylene succinate) and poly(butylene terephthalate) is dealt with in this study. In our previous work, it was demonstrated that PBS and PBT are immiscible not only from the changes of T _g but also from logG–log G plots. It is expected that the biodegradability of the blends could be improved by enhancing the miscibility. We tried to induce the transesterification reaction between two polyesters with various time intervals to enhance the miscibility of the blends. The extent of transesterification reaction was examined by ¹H-NMR. We utilized a dynamic mechanical thermal analyzer and a rotational rheometer to investigate the changes in miscibility. We also verified the biodegradability of PBS/PBT blends after the transesterification reaction by the composting method.