Lourdes Sanchez-Nacher

The effect of maleinized linseed oil (MLO) on mechanical performance of poly(lactic acid)-thermoplastic starch (PLA-TPS) blends

In this work, poly(lactic acid), PLA and thermoplastic starch, TPS blends (with a fixed content of 30wt.% TPS) were prepared by melt extrusion process to increase the low ductile properties of PLA. The TPS used contains an aliphatic/aromatic biodegradable polyester (AAPE) that provides good resistance to aging and moisture. This blend provides slightly improved ductile properties with an increase in elongation at break of 21.5% but phase separation is observed due to the lack of strong interactions between the two polymers. Small amounts of maleinized linseed oil (MLO) can positively contribute to improve the ductile properties of these blends by a combined plasticizing-compatibilizing effect. The elongation at break increases over 160% with the only addition of 6phr MLO. One of the evidence of the plasticizing-compatibilizing effect provided by MLO is the change in the glass transition temperature (Tg) with a decrease of about 10°C. Field emission scanning electron microscopy (FESEM) of PLA-TPS blends with varying amounts of maleinized linseed oil also suggests an increase in compatibility.

Mechanical and Thermal Properties of Polyvinyl Chloride Plasticized with Natural Fatty Acid Esters

From an industrial point of view, the use of new nontoxic and biodegradable plasticizers coming from natural resources is an interesting alternative to traditional plasticizers based on phthalates. In this study, two types of epoxidized fatty acids esters (EFAE) with different molecular weights have been used in order to produce flexible PVC with low toxicity. Different amounts of EFAE 201 and 401 have been considered in this study. Mechanical and thermal properties have been determined and morphology of fracture surface has been studied by scanning electron microscopy.

Optimization of atmospheric plasma treatment of LDPE films: influence on adhesive properties and ageing behavior

One of the major disadvantages of low density polyethylene (LDPE) films is their poor adhesive properties. Therefore, LDPE films have been treated with atmospheric pressure air plasma in order to improve their surface properties. So as to simulate the possible conditions in an industrial process, the samples have been treated with two different sample distances (6 and 10 mm), and treatment rates between 100 and 1000 mm s−1. The different sample distances are the distance of the sample from the plasma source. The variation of the surface properties and adhesion characteristics of the films were investigated for different aging times after plasma exposure (up to 21 days) using contact angle measurement, atomic force microscopy, weight loss measurements and shear test. Results show that the treatment increases the polar component () and these changes improve adhesive properties of the material. After the twenty-first day, the ageing process causes a decrease of wettability and adhesive properties of the LDPE films (up to 60%).

High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

Improvement of liquid absorption properties of nonwoven polypropylene substrates by low pressure plasma treatment with CH4-O2 mixture gas

The use of nonwoven textile substrates for filtration and absorption purposes is generalized due to the high surface area they can provide. Many of these applications require good wetting properties to increase efficiency. In this work, low pressure plasma treatment with a CH4-O2 mixture gas has been used to increase surface wettability and subsequent absorption properties on nonwoven polypropylene substrates. CH4 plasma treatment leads to a plasma polymerization process which results in hydrophobic surface finishing, but in combination with O2, it is possible to form a functionalized plasmapolymerized layer thus improving wetting properties. Changes in wetting properties have been studied by contact angle measurements showing that optimum wetting properties are obtained with exposure times to plasma treatment of about 10 min, and no significant changes are obtained for longer exposure times. Absorption efficiency has been followed by determining three different parameters by the guidelines of the UNE-EN-ISO 9073-6 standard: wetting time, liquid absorption capacity (LAC) and liquid propagation rate or absorption speed. All these properties are remarkably improved as the exposure time to CH4-O2 plasma increases; this improvement is remarkably high for relatively short exposure times (5–10 min) and no significant changes are obtained for long exposure times so that, it is possible to conclude that previous plasma treatment with exposure times in the 5–10 min range is an efficient method to improve overall absorption properties of nonwoven polypropylene substrates.

Mechanical and morphological characterization of novel vinyl plastisols with epoxidized linseed oil as natural‐based plasticizer

Poly(vinyl chloride) (PVC) is one of the most commonly used plastics in the current market due to its low cost and versatility in processing, combined with its satisfactory physical and chemical properties. However, there is an important problem associated to the use of plasticized PVC. This problem is regarding to the toxicity of the most common plasticized used like DOP, DEHP, DINP, due to its possible migration. This problem limits the use of the plasticized PVC in the industry. In this work we have used epoxidized linseed oil (ELO) as a non toxic plasticizer for PVC. This type of natural oil is characterized by acting as both plasticizer and stabilizer of PVC. With this purpose, ELO have been added to PVC. The processing conditions (temperature and time of curing) are vital to determine the final properties of the material. A study of the processing conditions shows the adequate temperature and time to achieve the optimum properties.

Improvement of the T‐peel Strength of Polypropylene Adhesion Joints by Surface Photografting Pre‐Treatment with Methyl Methacrylate

Although polypropylene is one of the most used polymers at industrial level due to good balanced properties, it presents some restrictions in applications that require good adhesion properties as well as coating and painting. These restrictions are related to its non polar nature which leads to low wetting properties. So that, in most cases, it is necessary a previous surface pre‐treatment in order to improve adhesion properties. These surface treatments could be physical or chemical. Among the wide variety of physical processes, plasma technologies are useful from both technical and environmental points of view. If we take into account economic considerations, chemical processes are interesting due to low cost equipment and procedures. In particular, we have used photografting of methyl methacrylate (MMA) monomer on polypropylene substrates with UV radiation and initiators. This process is useful to promote chemical modification of polypropylene surface by grafting MMA monomers into polypropylene polymer...

Disintegration in Compost Conditions and Water Uptake of Green Composites from Poly(Lactic Acid) and Hazelnut Shell Flour

Green composites of poly(lactic acid)-PLA and hazelnut shell flour (HSF) with and without epoxidized linseed oil (ELO) as plasticizer/compatibilizer were subjected to different aging conditions such as water uptake by immersion and disintegration in compost soil. The effect of the hydrolytic degradation was analyzed by measuring the weight gain as a function of the immersion time in water and calculating the corresponding diffusion coefficients. As expected, the water diffusion coefficient increases with HSF content while no remarkable change is obtained for plasticized compositions with ELO. Differential scanning calorimetry reveals a noticeable increase in crystallinity after the degradation process by water immersion. Degradation in controlled compost soil was followed thorough measurements of weight changes. In general, the weight change for a particular degradation time is lower as the HSF content increases. In addition, presence of ELO as plasticizer/compatibilizer delays the degradation process in compost soil. Scanning electron microscopy highlighted a noticeable deterioration of aged samples after 2 weeks with multiple crack formation and high surface abrasion due to microbial activity after 4 weeks.

Mechanical properties of green composites based on thermoplastic starch

The present work is focused on study of “green composites” elaborated from thermoplastic starch (TPS) as polymer matrix and a fiber from natural origin (rush) as reinforced fiber. The effect of the fiber content has been studied by means of the mechanical properties. The composite resulting presents a lack of interaction between matrix and fiber that represents a performance decrease. However the biodegradability behavior of the resulting composite raise this composite as useful an industrial level.

Improvement of adhesion properties of low density polyethylene (LDPE) substrate using atmospheric plasma

In this work we have used atmospheric plasma technology on polyethylene surface with different treatment conditions. These modify surface pre‐treatments on polyethylene, thus having a positive effect on overall surface activity of polymer surface and, consequently, adhesion properties can be remarkably improved. We have evaluated the influence of the nozzle/substrate distance and atmospheric plasma speed on wettability changes and adhesion properties. Wettability changes have been studied by contact angle measurements and subsequent surface energy calculation. Mechanical characterization of adhesion joints has been carried out in two different ways: peel and shear tensile test. The overall results show a remarkable increase in mechanical properties of adhesion joints for low nozzle/substrate distances and low speed. So plasma atmospheric technology is highly useful to increase adhesion properties of polypropylene.