Synthetic plastics are extensively used as packaging materials due to their low cost, good processability and good mechanical properties. Approximately 30% of the plastics are used for packaging applications, which is still expanding at a high rate of 12% per annum . However, many plastic packaging products, e.g. for food, pharmaceuticals, cosmetics, detergents and chemicals, have a short service life . After a limited time of use, plastic packaging has to be disposed. Only a limited amount of plastic waste can be recycled and reused. The majority of plastic waste is disposed of through landfill, which creates big issues for the environment since plastics are persistence in the environment. Nowadays, most commodity plastics used are conventional plastics that take decades to degrade. The environmental impact of plastic waste is increasing the need for alternative materials for short-term packaging and disposal applications. Therefore, bio- based polymers are being developed as a replacement for petroleum based packaging plastics. Bio-based polymers are derived from renewable resources, e.g. corn, cane sugar and starch. They can be divided into two categories: 1) One is ‘biopolymers’, which are polymers produced by the metabolic process of the living cells. This type includes some carbohydrates (e.g. cellulose and starch) and some proteins (e.g. keratin); 2) The other category includes the polymers that are synthesised from biomass monomers, for example poly(lactic acid) (PLA).
E96 (ASTM Standards, 1995)  and similar to that manipulated by Ghasemlou et al. (2011)  and corrected for the stagnant air gap inside test cups according to the equations of Gennadios et al. (1994) . Special glass cups with wide rims were used to determine WVP. The cups, contained approximately 80 g of anhydrous calcium chloride desiccant (0 % RH, assay cup) or nothing (control cup), were covered with different films. Films without pinholes or defects were cut circularly (0.002827 m 2 film area) and sealed to the cup mouths using molten paraffin. Each cup was placed in desiccators and maintained at 75 % RH with a sodium-chloride-saturated solution. This difference in RH corresponds to a driving force of 1753.55 Pa, expressed as water vapor partial pressure. After the films were mounted, the weight gain of the whole assembly was recorded every 1 hour during the first 9 hours and finally after 24 hours (with an accuracy of 0.0001 g). The cups were shaken horizontally after every weighing. The slope of the weight versus time plot (the lines’ regression coefficients were >0.998) was divided by the effective film area to obtain the water vapor transmission rate. This was multiplied by the thickness of the film and divided by the pressure difference between the inner and outer surfaces to obtain the WVP (Eq.1).
Polylactide (PLA) is rigid thermoplastic polyester with a semicrystalline or completely amorphous structure depending on the stereopurity of the polymer backbone. PLA has gained a considerable interest due to its bioresorbability, biodegradability, and biocompatibility. Furthermore, its ability to be crystallized under stress, thermally crystallized, filled, and copolymerized, turn it into a polymer with a wide range of applications. The principal drawbacks of such a biodegradable polymer in terms of industrials application like food packaging are its poor thermal resistance, low mechanical and limited gas barrierproperties. These drawbacks could be overcome by improving the thermo mechanical properties through copolymerization, blending, and filling techniques. However, the use of fillers appears to be the most attractive approach because of lower cost. There are different approaches for the preparation of PLA nanocomposites: in-situ polymerization, solution intercalation, and melt intercalation. Since melt
When environmental conservation had not yet become an issue, many manufacturers used manmade fibres as fillers in composites due to their superior composite reinforcing ability (Mohanty et al., 2000). It was not until the late 1980s that research into natural fibres as composite fillers became important (Westman et al., 2010). Specifically in the plastic packaging field, research works on natural fibre reinforced petroleum- derived plastics, the so called “big four” polyethylene (PE), poly(propylene) (PP), polystyrene (PS) and poly(vinyl chloride) (PVC), became prevalent (Mohanty et al., 2000). In recent years, with the intensifying environmental concern and stringent government regulations especially in the Asian and European countries, development of packaging materials that are attuned to the environment such as bio-derived polymers, recyclable materials and reusable packaging have become a main focus (Holbery & Houston, 2006; Satyanarayana et al., 2009; Johansson et al., 2012).
The field of nanoscience has blossomed over the last two decades and the importance of nanotechnology increase in areas such as computing, sensors, biomedical and many other applications. In this regard the discovery of graphene  and graphene-based polymer nanocomposites is an important addition in area of nanoscience. The superior properties of graphene compared to polymers are reflected in graphene-based polymer composites. Graphene-based polymer composites show superior mechanical, thermal, gas barrier, electrical and flame retardant properties, compared to the neat polymer [27–31]. Our study adds new knowledge about tunable physicochemical properties of the nanocomposites by varying the GNP content and distribution of graphene layers in the polymer matrix, as well as interfacial bonding between the graphene layers and polymer matrix. These properties open new opportunities to revolutionize a variety of practical applications, e.g. multifunctional composites, detectors, smart wearables, paints and printing. Carbon nanofillers have great advantages as additives in polymers for application in Additive Manufacturing (3D printing). It should be highlighted that 3D printing is not only an innovative processing technology, but it is the future of the manufacturing industries. Therefore, unlimited needs exist for novel materials suitable for 3D printing for variety of applications that require improved mechanical performances, conductivity and other functional properties of the final products.
Abstract: Calcium phosphate-based biomaterials have been well studied in biomedical fields due to their outstanding chemical and biological properties which are similar to the inorganic constituents in bone tissue. In this study, amorphous calcium phosphate (ACP) nanoparticles were prepared by a precipitation method, and used for preparation of ACP-poly( d , l -lactic acid) (ACP-PLA) nanofibers and water-soluble drug-containing ACP-PLA nanofibers by electrospin- ning. Promoting the encapsulation efficiency of water-soluble drugs in electrospun hydrophobic polymer nanofibers is a common problem due to the incompatibility between the water-soluble drug molecules and hydrophobic polymers solution. Herein, we used a native biomolecule of lecithin as a biocompatible surfactant to overcome this problem, and successfully prepared water-soluble drug-containing ACP-PLA nanofibers. The lecithin and ACP nanoparticles played important roles in stabilizing water-soluble drug in the electrospinning composite solution. The electrospun drug-containing ACP-PLA nanofibers exhibited fast mineralization in simulated body fluid. The ACP nanoparticles played the key role of seeds in the process of mineraliza- tion. Furthermore, the drug-containing ACP-PLA nanofibers exhibited sustained drug release which simultaneously occurred with the in situ mineralization in simulated body fluid. The osteoblast-like (MG63) cells with spreading filopodia were well observed on the as-prepared nanofibrous mats after culturing for 24 hours, indicating a high cytocompatibility. Due to the high biocompatibility, sustained drug release, and fast mineralization, the as-prepared com- posite nanofibers may have potential applications in water-soluble drug loading and release for tissue engineering.
group has been working on PLA nanocomposites with surface-hydroxylated magnesium oxide (MgO) nanoparticles, including conventionally prepared NanoActive MgO (CP-MgO) and aerogel-prepared NanoActive MgO plus (AP-MgO) (Beavers et al., 2009; Li & Sun, 2010; Wang et al., 2009). These two types of MgO nanoparticles were developed by Dr. Klabunde and his co-workers (Itoh et al., 1993; Utamapanya et al., 1991) and have been commercialized. Compared with commercial MgO, these nanoparticles have a much smaller crystal size, higher surface area, more surface defects, and higher reactivity, which result in large numbers of surface hydroxyl groups because of water dissociation (Itoh et al., 1993; Lucas et al., 2001). We have prepared PLA nanocomposites with CP-MgO nanocrystals (hexagonal plate-like structure, 50 to 100 nm long, 5 nm thick, about 250 m 2 /g surface area) through thermal compounding (Wang et al., 2009). At a CP-MgO loading ratio of 0.4 wt% or less, mechanical properties of nanocomposites were significantly improved, probably because of the affinity PLA segments have for the CP-MgO surface by hydrogen bonding. However, because inorganic nanoparticles typically agglomerate and are not always miscible with the organic polymer phase, it is usually a challenge to achieve better dispersion and strong interfacial interaction between nanoparticles and the polymer matrix. One strategy to
The WVPs of the composite films are closely related to how the clay is dispersed within. At very low loadings of clay (i.e. 3 pph) the dispersion is likely to be optimized due to a lower probability of physical, direct clay-clay interactions. This presumably leads to the enhanced WVP improvement for Na-MMT and Q-MMT composites at this clay content. At higher clay loadings (>6 pph) the extent of dispersion will be less due to there being insufficient volume within the polymer matrix for the clays to exfoliate; the resulting agglomeration of the clay particles may present channels for water to pass through more readily. Above a certain clay concentration, i.e. the observed maximum, the layers are combined such that a closely packed distribution is formed that limits the passage of water vapor. The combination of Q-MMT and EPVOH resulted in the lowest overall water vapor permeability (<1.0 g/Pa·s·m x 10 -5 ) at the lowest addition of clay, which supports the creation of a highly impermeable and segregated or self-stratifying clay layer within the film, as indicated by the XRD and FTIR data. Perhaps the organophilic Q-MMT clay also contributes to reduce the water sensitivity of the polymer.
PLA is a biodegradable thermoplastic polyester and has attracted increasing attention due to their potential applications as biomedical and environment friendly materials. Polylactic acid (PLA) is the most attractive biodegradable polymer for food packaging applications by several advantages such as its high transparency, good mechanical properties, renewable origin and biodegradation . PLA is rigid and brittle below the glass transition temperature (Tg) which is in the range of 50-60C° so plasticization is the good alternative in its various applications. Polyethylene glycol soluble in water shows hydrophilicity and biocompatibility and plasticizers is frequently used, not only to improve the process-ability of polymers, but also to increase the flexibility and ductility of glassy polymers and decrease the glass transition temperature of the polymer, meaning the plasticizer and polymer must be miscible. Typically, amounts from 10 to 20wt% plasticizers(PEG) are required to provide a substantial reduction of the glass transition temperature (Tg) of the PLA matrix and adequate mechanical properties and can be any biodegradable product, sufficiently nonvolatile, with a relatively low molecular weight to produce a desired decrease in Young‘s modulus value and increase in impact strength . PLA plasticization is required to improve PLA ductility. Polyethylene glycol (PEG) has been used as PLA plasticizers increase the PLA thermal stability, which is detrimental for food packaging use. Nanomaterials for food packaging include metal, ceramic , paper and inorganic nanoparticles such as silica, titanium oxide or metal such as silver was usually considered to be an effective method to improve the properties of materials by interaction with components .Since the properties of films were settled by factors such as crystalline structures of ingredients, morphologies of films and molecular interactions, the investigation about the influences of inorganic nanoparticles on these properties will be highly necessary.
Ag nanoparticles . The main bands of DMF in Ag/ PMMA nanocomposites spectra are clearly seen. The similarities between DMF and Ag/PMMA nanocomposite spectra verify the vital element of DMF in Ag/PMMA nanocomposites. It is found that the C = O (approximately 1,651 cm −1 ) and O = C-N-C (approximately 659 cm −1 vi- bration modes of DMF in Ag/PMMA nanocomposites was similar to those in DMF solvent. The bands corres- pond to C-O-C of the methoxy group, and skeletal C-C in Ag/PMMA nanocomposites appeared at 1,151 and 1,257 cm −1 , respectively. These bands strongly affect their shape and size. A broad band of the carboxylic acid group due to the O-H (approximately 3,499 cm −1 ) in Ag/PMMA nanocomposites becomes broader as the temperature in- creases. The increase in water content may be originated from the environment or product of the chemical reac- tions. Both bands at approximately 1,065 and 1,088 cm −1 in Ag/PMMA nanocomposites are assigned to the sensi- tive metal complexes of methyl rocking vibrations coupled with a C-N vibration mode. The Ag/PMMA nanocompos- ite band at approximately 1,387 cm −1 is coupled in vibra- tion, with the major contributions from CH 3 deformation
PET/Cloisite 30B (C30B) nanocomposites of different organoclay contents were prepared using water-assisted melt-mixing. The reduction of the molecular weight of the PET matrix, caused by hydrolysis during the water-assisted extrusion, was compensated by subsequent solid- state polymerization (SSP). SSP of PET was carried out at a temperature below the melting point but above the glass transition of PET using two particle sizes for different reaction times. The zero-shear viscosity was found to vary with the weight-average molecular weight to the 3.6 power for the linear PETs. The Maron-Pierce model was used in this work to determine the molecular weight of the PET in the nanocomposites. Significant increases in molecular weight (M W ) were found for the neat PETs and PET nanocomposites using SSP, which were accompanied by substantial reductions of the carboxyl end groups. Lower M W was observed for the nanocomposites compared to the neat PETs. This could be attributed to a restricted mobility of reactive groups and diffusion of by-products formed during SSP (i.e. water and ethylene glycol) due to the presence of nanoparticles. The linear viscoelastic data for the neat PETs and PET nanocomposites could be correlated using the zero-shear viscosity of the matrix. However, our results showed enhanced rheological properties (mostly for the storage modulus) for samples containing more carboxyl groups, suggesting that the interactions between PET chains and C30B for hydrolyzed samples in the melt state was stronger than for SSP samples due to the larger content of carboxyl groups. DSC results showed reductions in the crystallization temperature and the degree of crystallinity as well as increases in the half-time of crystallization with increasing
Measurements of gloss determined from the film side in contact with air are presented in Figure 11 for the EPVOH composite films containing 3 pph filler alongside those of the pure polymer films. EVOH films are recognized for their very high gloss. 7 Indeed the EPVOH films exhibited 104 gloss units on average, almost equal to the highly glossy PET reference film and slightly higher than the PVOH film. LDPE on the other hand had low gloss (around 20). EPVOH composite films containing the hydrophobic modified Q-MMT showed high gloss over the entire range of loadings (23-86 gloss units for 12-3 pph Q-MMT, respectively) whereas the respective films containing C-MMT had a semi- glossy appearance (7-12 gloss units) and the Na-MMT films had a matte finish (3-4 gloss units). Gloss is a property that is controlled by the topmost surface properties. Incorporation of fillers may lead to a slight increase in the micro scale surface roughness which could partially explain the observed decrease in gloss compared to the unfilled film. The data may also give some information about the distribution of clay particles. The lower gloss obtained for composite films comprising C- MMT and Na-MMT indicate the location of clay particles near the topmost surface whereas that for the Q-MMT composite indicates the clay particles are below the topmost surface, which was evidenced also by FTIR analysis 29 of the films. This correlates with the contact angle measurements
Abstract: The effects of organically modified montmorillonite clay nanoparticles in neat vinyl ester resin were investi- gated. Organically modified MMT clay particles, Cloisite10A and Cloisite30B were dispersed into neat organic vinyl es- ter resin by using a ultrasonic method. Morphology of the dispersed clay particles in the nanocomposites formed during polymerization, was characterized by X-ray diffraction (XRD) spectroscopy and found that intercalated nanocomposites were formed. The thermal properties such as decomposition and glass transition temperatures, percent weight retention and tan δ were determined by thermo gravimetric analyzer (TGA) and dynamic mechanical thermal analyzer (DMTA). A decrease in glass transition temperature was found in both vinylester/Cliosite10A and vinylester/Cliosite30B nanocompo- sites. The tensile, flexural and impact properties of the nanocomposites were determined by universal testing machine (UTM) and Izod impact tester. Due to the incorporation of MMT nanoparticles in vinyl ester resin an improvement in mechanical properties was observed. The effect of water absorption on nanocomposites was investigated and a signifi- cant decrease in water absorption of the vinylester nanocomposites was found.
enhance the barrierproperties of the polymers. To improve the barrierproperties of polymers, generally nonporous nanomaterials have been added to the polymer matrix as a filler to block gas, vapor or water diffusion. Without the incorporation of some kind of the nanofillers, molecules will permeate through the polymer in a shortest pathway that is perpendicular to the polymer film orientation. But these nanofillers can increase the tortuosity, which ultimately results in an extended travelling pathway of the diffusing molecules through the polymer nanocomposites. 1 Nanomaterials were used as a filler
Received: 4 March 2020; Accepted: 17 March 2020; Published: 24 March 2020 Abstract: The design of new materials with antimicrobial properties has emerged in response to the need for preventing and controlling the growth of pathogenic microorganisms without the use of antibiotics. In this study, partially reduced graphene oxide decorated with silver nanoparticles (GO–AgNPs) was incorporated as a reinforcing filler with antibacterial properties to poly(vinyl alcohol) (PVA) for preparation of poly(vinyl alcohol)/graphene oxide-silver nanoparticles nanocomposites (PVA/GO–AgNPs). AgNPs, spherical in shape and with an average size of 3.1 nm, were uniformly anchored on the partially reduced GO surface. PVA/GO–AgNPs nanocomposites showed exfoliated structures with improved thermal stability, tensile properties and water resistance compared to neat PVA. The glass transition and crystallization temperatures of the polymer matrix increased with the incorporation of the hybrid. The nanocomposites displayed antibacterial activity against Staphylococcus aureus and Escherichia coli in a filler content- and time-dependent manner. S. aureus showed higher susceptibility to PVA/GO–AgNPs films than E. coli. Inhibitory activity was higher when bacterial cells were in contact with nanocomposite films than when in contact with leachates coming out of the films. GO–AgNPs based PVA nanocomposites could find application as wound dressings for wound healing and infection prevention.
The ability of the GRP and CGRP composites to retain its mechanical properties when kept under water, acid, and base medium was analyzed by keeping the impact samples in a corrosive medium for a period of 30 days. The effect of corrosive medium on impact strength of nanocomposites is shown in Fig. 4. The corrosive environment has considerable effect on the property deterioration. The impact strength of nanocomposites kept in water and acid medium decreases slightly. Impact strength decreases more in the nanocomposite samples kept in base medium. This studies confirms that, the nanocomposites have better ability to retain their properties after immersing in corrosive mediums. The nanocomposites retain more than 90 % of its impact strength when the samples are kept in the corrosive mediums except the alkali medium (1% NaOH solution). But the conventional GRP composites retain less than 90% of its value (Fig. 4).
In summary, single-layer coating of waterborne epoxy-amine resin and its bilayer composite coating with hydrophobic PE-alloy and lamellar graphene oxide functional fillers were thoroughly investigated for their anticorrosion performance under different environmental conditions. Anticorrosive coating system with hydrophobic surface and enhanced oxygen barrier property was obtained and characterized by increased water contact angle and decreased oxygen gas permeability. Electrochemical impedance spectroscopy study indicated increased coating impedance of the bilayer coating under both immersion and simulated splash environmental conditions. Water ingress at the metal/coating interface could be a major cause of coating delamination, however, our study indicated that oxygen content also plays a key role during this process, although the actual mechanism was still not fully understood. The future work will be on elucidating the mechanism and modeling of coating delamination coupled with corrosion propagation at a molecular level, which will provide fundamental guidance for the design of novel anticorrosive coatings.
Billovits and Durning [4.20] formulated a model of polymer/ penetrant diffusion accompanied by arbitrarily large polymer displacements. This model gives a general description of unsteady binary diffusion problems in a coordinate system fixed with respect to the reference configuration of one component. The model was found to accommodate two alternate macroscopic formalisms for interdiffusion; the usual engineering formulation which employs species continuity equations, equations of motion for the mixture and constitutive relations for the diffusion mass flux and total stress tensor and a method employing continuity equations, species equations of motion and constitutive relations for the species interaction forces and species partial stress tensors. 4.1.2 General diffusion experiments of water into polymeric materials Diffusion of small molecules into polymeric materials can alter the physical properties of such systems [4.21], The extent of these changes usually depends on the amount and properties of penetrant sorbed. Changes induced by polymer/ solvent interactions can occur on the chemical level (e.g. H/D exchange reactions), on the crystal level (changes in crystallinity of semicrystalline polymers) or on the supermolecular level [4.22].
casted onto the quartz electrodes, and then dried to obtain sensing films. The measured frequency shifts under exposure of different humidity levels showed that the whole sensors studied have high sensitivity, durability and repeatability, almost a full range of linear relative humidity response, fast response/recovery times and low hysteresis. Moreover, they have high selectivity towards humidity over the various polar and non-polar solvent vapors such as alcohol, ketone, ester, chlorinated and non- chlorinated hydrocarbons. These results promise that the EPSDA based organic-inorganic hybrid composites have superior properties for relative humidity measurements.
The need for the development of new materials with better properties is increasing day by day. Nanocomposites are obtained by mixing two different materials in certain proportions. The thermal and mechanical properties of composites are superior to pure polymer. The use of polymers in composites provides many advantages in terms of flexibility, lightness and easy workability. Polymer nanocomposites exhibit many different properties such as important mechanical resistance, water and oxygen barrier, dimensional stability, thermal stability, flame retardant, chemical resistance, optical, magnetic and electrical properties .