I. Moura

Evaluation of Properties and Biodeterioration Potential of Polyethylene and Aliphatic Polyester Blends

Abstract Blends of high density polyethylene (HDPE) and biodegradable polymers – polylactic acid, PLA, poly(∊-caprolactone), PCL and Mater-Bi® (thermoplastic starch (TPS) with PLA or PCL) – were prepared in a co-rotating twin-screw extruder, together with polyethylene modified with maleic anhydride (PE-g-MA) used as compatibiliser. The mechanical and rheological properties, morphology and potential for biodeterioration of polymeric materials were evaluated. Blends with PLA showed a reduced elongation at break but an increased Youngs modulus while the addition of PCL led to materials with a greater elongation at break and a lower Young modulus. The rheological results evidenced that HPDE and the blend with the highest TPS level exhibited the highest viscosity. The microbial growth test carried out to evaluate the potential for biodeterioration of the blends, using a pure culture of Pseudomonas fluorescens, indicated that HDPE/PCL had a lower resistance to bacterial attack than the blend of HDPE/PLA. This was verified by a higher cell number on its surface after 10 weeks of incubation. The addition of 30% starch to the HDPE/PLA blend enhanced its biodeterioration potential, the same was not observed in the case of the HDPE/PCL blend containing just 18% starch.

Synthesis and characterization of polystyrene-block-poly(vinylbenzoic acid): a promising compound for manipulating photoresponsive properties at the nanoscale

Using reversible addition-fragmentation chain transfer (RAFT) polymerization, the effect of PSt macroRAFT and 4VBA ratio on the synthesis of a carboxylic acid functional block copolymer (PSt-b-P4VBA) was studied. PSt macroRAFT polymer was initially prepared followed by the insertion of 4-vinylbenzoic acid (4VBA) monomer. The chemical structure of the diblock copolymer was confirmed by NMR and FTIR. The effect of PSt macroRAFT and 4VBA ratio on copolymerization yield and on molecular weight distribution was assessed by gel permeation chromatography. The rate of polymerization did not change as the 4VBA/PSt macroRAFT ratio increased, indicating an ideal amount of 4VBA insertion. An optimal ratio of [PSt macroRAFT]:[AIBN]:[4VBA] was 1.2:1:180. DSC and XRD confirmed the amorphous structure of homo and copolymer. Thermal stability was higher for PSt-b-P4VBA forming activated porous carbon char by dehydration, carbonization and oxidation. SEM and STEM observations showed a morphological evolution between PSt macroRAFT and the correspondent copolymer.

Morphology, optical, and electric properties of polymer-quantum dots nanocomposites: effect of polymeric matrix

ABSTRACTPolymer-CdTe quantum dots (QDs) nanocomposites were developed via solvent casting. Colloidal CdTe QDs, synthesized in aqueous solution, were transferred to organic media by exchanging of the original capping ligands by a long-chain thiol. Different commercial polymers (PMMA, OPS, PS, and PC), transparent in the visible spectral range, were chosen as matrices. Stock solutions of the polymers were prepared in suitable concentration (2 wt%) for the production of thin films with good quality, able to maximize the solubility of QDs, without phase separation. Studies on the morphological and optical properties were performed. The results showed that the polymer matrix has a considerable effect on QDs’ morphology, size, and electric conductivity. PMMA demonstrated to be the most promising embedding matrix, offering new possibilities for optoelectronic applications of polymer-QD nanocomposites.

Biodegradable polymernanocomposites for packaging applications

Abstract Biodegradable polymers have attracted a high interest in a wide range of applications, including packaging, due to the increasing social concerns. To meet the growing demand for sustainability and environmental safety, a number of studies using biodegradable polymers focused on the development of packaging products, is increasing in order to produce materials that could rapidly degrade and completely mineralize. Biodegradable polymers can be obtained from renewable resources (starch, chitin, cellulose, casein, zein, and soy protein), synthesized using fossil derivatives [poly(lactic acid) and poly(ɛ-caprolactone)] or produced by bacteria (polyhydroxyalkanoates). Unfortunately, the use of biopolymers as packaging materials has drawbacks, such as, poor mechanical, thermal, and barrier properties when compared to conventional nonbiodegradable materials. Due to this, many research efforts were made to improve properties of biopolymers, including the preparation of nanocomposite materials. This chapter presents examples of biodegradable polymers from different sources and the development of new materials, nanocomposites, for food-packaging applications.

Bioplastics from agro-wastes for food packaging applications

Abstract Bioplastics exhibit unique properties and can be produced from plants and crop wastes, among others, cellulose, proteins, and starch are some of the examples. Due to environmental concerns, it is of high priority to replace conventional plastics with bioplastics, and even better if they are directly synthesized from agro-wastes. Green chemistry methodology is applied to extract natural polymers, such as cellulose, from vegetable wastes. This chapter focuses on the preparation of new functional biopolymers for packaging based on extracted cellulose, which exhibits broadly tunable thermomechanical properties and biodegradation. Therefore, this contribution shows the potential of agro-wastes to produce new cellulose-based bioplastics for food packaging applications.