Rheological Behaviour, Mechanical Properties and Processability of Biodegradable Polymer Systems for Film Blowing
TL;DR: In this paper, a detailed investigation on the rheological, mechanical and processability behavior of some biodegradable polymers (originating from MaterBi® and Bioflex® commercial groups) was carried out, in order to assess their suitability to industrial-scale film blowing by direct comparison with a traditional non-biodegradability polymer (LDPE).
Abstract: Films for agricultural or packaging applications are typically made of low density polyethylene (LDPE). They are produced through the film blowing process, which requires the use of polymers with suitable rheological properties. Furthermore, the short shelf-life which is often related to many packed products leads to huge amounts of plastic-based wastes. This suggests the use of biodegradable and/or compostable polymers in replacement for traditional ones. To this regard, only few data exist on the rheological properties of biodegradable polymers undergoing film blowing processing. In this work, a detailed investigation on the rheological, mechanical and processability behaviour of some biodegradable polymers (originating from MaterBi® and Bioflex® commercial groups) was carried out, in order to assess their suitability to industrial-scale film blowing by direct comparison with a traditional non-biodegradable polymer (LDPE). Rheological tests under shear and non-isothermal elongational flow allowed to find out the two most suitable polymer grades. The film blowing production operations at different draw and blow-up ratios (from 2.5 to 3.5) showed that the two samples are suitable for industrial scale operations. Results from tensile and impact tests indicated that the two selected polymers exhibit significantly different mechanical properties (up to 10–15%).
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TL;DR: The results and data collected show that poly-lactic acid (PLA), poly-butylene adipate-co-terephthalate (PBAT) and poly-caprolactone (PCL) are the most used biodegradable polymers, but are prone to hydrolytic degradation during processing.
Abstract: The environmental performance of biodegradable materials has attracted attention from the academic and the industrial research over the recent years. Currently, degradation behavior and possible recyclability features, as well as actual recycling paths of such systems, are crucial to give them both durability and eco-sustainability. This paper presents a review of the degradation behaviour of biodegradable polymers and related composites, with particular concern for multi-layer films. The processing of biodegradable polymeric films and the manufacturing and properties of multilayer films based on biodegradable polymers will be discussed. The results and data collected show that: poly-lactic acid (PLA), poly-butylene adipate-co-terephthalate (PBAT) and poly-caprolactone (PCL) are the most used biodegradable polymers, but are prone to hydrolytic degradation during processing; environmental degradation is favored by enzymes, and can take place within weeks, while in water it can take from months to years; thermal degradation during recycling basically follows a hydrolytic path, due to moisture and high temperatures (β-scissions and transesterification) which may compromise processing and recycling; ultraviolet (UV) and thermal stabilization can be adequately performed using suitable stabilizers.
135 citations
TL;DR: In this paper, an efficient compatibilizer of PLA-g-GMA (PLA grafted with glycidyl methacrylate) was prepared by melt grafting and then introduced to compatiblize the two phases in PLA/PBAT blends.
55 citations
TL;DR: In vitro biocompatibility, investigated through the contact of flat die extruded films with cells, resulted improved with respect to low density polyethylene (LDPE), and the PLA-based materials were able to affect immunomodulatory behavior of cells and showed a slight indirect anti-microbial effect.
Abstract: Biodegradable polymers are promising materials for films and sheets used in many widely diffused applications like packaging, personal care products and sanitary products, where the synergy of high biocompatibility and reduced environmental impact can be particularly significant. Plasticized poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blend-based films, showing high cytocompatibility and improved flexibility than pure PLA, were prepared by laboratory extrusion and their processability was controlled by the use of a few percent of a commercial melt strength enhancer, based on acrylic copolymers and micro-calcium carbonate. The melt strength enhancer was also found effective in reducing the crystallinity of the films. The process was upscaled by producing flat die extruded films in which elongation at break and tear resistance were improved than pure PLA. The in vitro biocompatibility, investigated through the contact of flat die extruded films with cells, namely, keratinocytes and mesenchymal stromal cells, resulted improved with respect to low density polyethylene (LDPE). Moreover, the PLA-based materials were able to affect immunomodulatory behavior of cells and showed a slight indirect anti-microbial effect. These properties could be exploited in several applications, where the contact with skin and body is relevant.
37 citations
TL;DR: In this paper, the fracture surfaces of a light-conversion film were observed using a scanning electron microscope (SEM), and then, the fluorescence spectra and mechanical properties of the film were tested.
30 citations
TL;DR: The formulation of polymeric films endowed with the abilities of controlled release of antimicrobials and biodegradability is the latest trend of food packaging, and such ternary systems could be particularly suitable as green materials for food packaging applications, and for antimicrobial wrapping applications.
Abstract: The formulation of polymeric films endowed with the abilities of controlled release of antimicrobials and biodegradability is the latest trend of food packaging. Biodegradable polymer (Bio-Flex®)-based nanocomposites containing carvacrol as an antimicrobial agent, and a nanoclay as a filler, were processed into blown films. The presence of such hybrid loading, while not affecting the overall filmability of the neat matrix, led to enhanced mechanical properties, with relative increments up to +70% and +200% in terms of elastic modulus and elongation at break. FTIR/ATR analysis and release tests pointed out that the presence of nanoclay allowed higher carvacrol loading efficiency, reasonably hindering its volatilization during processing. Furthermore, it also mitigated the burst delivery, thereby enabling a more controlled release of the antimicrobial agent. The results of mass loss tests indicated that all the formulations showed a rather fast degradation with mass losses ranging from 37.5% to 57.5% after 876 h. The presence of clay and carvacrol accelerated the mass loss rate of Bio-Flex®, especially when added simultaneously, thus indicating an increased biodegradability. Such ternary systems could be, therefore, particularly suitable as green materials for food packaging applications, and for antimicrobial wrapping applications.
26 citations
References
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TL;DR: The literature on the rheology of liquid crystals formed from rod-like molecules is reviewed in this article, where the types of polymers that form liquid crystal phases and the conditions for liquid crystal formation are summarized.
Abstract: The literature on the rheology of liquid crystals formed from rod‐like molecules is reviewed in this article. After a brief introduction to liquid crystals in general and their rheology in particular, the types of polymers that form liquid crystal phases and the conditions for liquid crystal formation are summarized. The framework for the discussion of the rheology of polymeric liquid crystals is based on the three‐region flow curve proposed by Onogi and Asada. The plateau viscosity region is the one best understood, with general agreement among various studies and with theory. The data for onset of shear thinning at high shear rates and for other viscoelastic phenomena are not consistent among different investigators. Many liquid crystal polymers have an initial shear thinning region and appear to have a yield stress. Rheo‐optical data suggest that this is the result of the domain texture which commonly exists in liquid crystal systems. In many cases, this behavior is confounded by chemical effects such as aggregation or crystallization, which give rise to sample history effects and which probably account for some of the discrepancies in the literature.
288 citations
TL;DR: In this paper, the phase morphology of PLA/PBAT blends was observed by scanning electronic microscopy (SEM) and the linear and non-linear shear rheological behaviors of PLA and PBAT melts were investigated by an advanced rheology expended system (ARES).
229 citations
TL;DR: In this paper, the nonlinear viscoelastic properties for a series of intercalated nanocomposites of an organically modified montmorillonite and a disordered styrene−isoprene diblock copolymer are reported.
Abstract: The nonlinear viscoelastic properties for a series of intercalated nanocomposites of an organically modified montmorillonite and a disordered styrene−isoprene diblock copolymer are reported. The li...
170 citations
"Rheological Behaviour, Mechanical P..." refers background in this paper
...This behaviour has been correlated with the presence of a convergent flow at the inlet of the capillary, which deforms the geometry of the dispersed phases, decreasing the viscosity of the melt [17, 29]....
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...It has been reported in some papers [14, 17, 29, 30] that the viscosity of complex polymer systems does not follow the Cox-Merz rule since the viscosity curve, measured as a function of the frequency, in a rotational rheometer does not lay over the flow curve measured in a capillary rheometer....
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TL;DR: In this article, the viscosities of two types of PLA resins (amorphous and semicrystalline) at 150 and 170°C and at various shear rates (30, 50, 70, 90, 110, 130, and 150 rpm screw speeds) were measured with a tube rheometer on an extruder.
159 citations
TL;DR: In this paper, a lactic acid oligomer (OLA) was used as a plasticizer for poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) blends.
Abstract: Blends of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) plasticized with a lactic acid oligomer (OLA) added at three different concentrations (15, 20 and 30 wt% by weight), were prepared by an optimized extrusion process to improve the processability and mechanical properties of these biopolymers for flexible film manufacturing. Mor- phological, chemical, thermal, mechanical, barrier and migration properties were investigated and formulations with desired performance in eco-friendly films were selected. The efficiency of OLA as plasticizer for PLA_PHB blends was demonstrated by the significant decrease of their glass transition temperatures and a considerable improvement of their duc- tile properties. The measured improvements in the barrier properties are related to the higher crystallinity of the plasticized PLA_PHB blends, while the overall migration test underlined that all the proposed formulations maintained migration lev- els below admitted levels. The PLA_PHB blend with 30 wt% OLA was selected as the optimum formulation for food pack- aging, since it offered the best compromise between ductility and oxygen and water vapor barrier properties with practically no migration.
158 citations