Physical properties-mechanical: specific essays on container for alimentary use

The plastic containers pose like one of the main options in the packaging of all type of products, since they present advantages like his low weight and his versatility, in addition to supposing a half option environingingmentally sustainable, since it exists a system of waste management (‘Green Point') designed specifically for the recovery of the waste of container and his back valorisation (by means of technicians like recycled mechanic, recycled chemist, etc.). These factors have done that the presence of plastic containers for foods follow an increasing tendency over time.

To guarantee the correct functionality of the plastic containers, these subject to distinct types of essays, adapted in each case to the multiple formats of container that employ for the distinct alimentary products: bottles, stock exchanges, tubs, sobres, trays, and a long etcetera that we can find in the linear of our usual supermarket.

Inside the indispensable verifications to guarantee this functionality, stands out the control of the physical properties-mechanical of the containers. These controls will be the attendants to guarantee that the container is able to resist the distinct mechanical efforts during his useful life, from the manufacture of the container until his final utilisation by part of the consumer, going through the stages of packaging of the product, packaging of the units of distribution, transport and storage.

In function of the concrete type of container, pose different controls of the mechanical properties. To way of example, go to pose diverse cases:

1. Stock exchange of an alone use of type T-shirt.
2. Reusable stock exchange.
3. Pack type tub or tray pelable.
4. Bottle.

The stock exchanges of an alone use have to fulfil some characteristics that come described by the norm JOINS 53257-2/1M:1997. This norm contemplates the properties to verify in said stock exchanges, together with the criteria of acceptance of the same. Some of the properties to verify are dimensions and mass, resistance to impact, effort and elongation to traction, resistance to the static load and adhesion of the inks. The dimensions that verify in a stock exchange type T-shirt are the reflected in the following drawing, with his corresponding table:

Fig.1: Diagram of dimensions of a stock exchange type T-shirt

The criteria to fulfil by this type of product come collected in the norm of product JOINS 53942:2012. This norm arises of the initiative of the manufacturers of plastic bags of Anaip (Spanish Association of Industrial of plastic), ranged with the increasing environingingmental awareness of the society, and following the marked guidelines by the Ministry of Environingingment in his National Plan Integrated of Management of Waste (Pnir). In this plan proposes the reuse and the promotion of the use of reusable articles, and includes an aim of reduction of consumption of the called stock exchanges of an alone use.

The properties and requirements proposed in the norm collect in the following table:

Properties and requirements proposed in the norm.

In this case, unlike the previous, does not exist a norm of specific product where describe the parameters to check and the requirements to fulfil. Therefore, the controls to realizar on this product will select of agreement to the function to fulfil by part of the container.

The main essays proposed for this type of products would be the following:

• Resistance to compressesion: To see the resistance of the container in apilamiento (p.And. During the storage and distribution). It determines according to norm JOINS-IN ISO 604:2003.
• Resistance to impact by free fall: To evaluate the resistance of the container when suffering a fall, for example from the linear of purchase.
• Resistance to the peeled: To determine the resistance of the sealed (opening ease of one covers, for example).
• Resistance to punción of the film (cover): to evaluate the resistance of covers it to possible perforaciones accidental. It determines according to norm JOINS IN 14477:2004.
• Detection of escapes: To evaluate possible defects of sealed or existent pores in the container. Can determine of different forms: according to ASTM F1929-2012 (method of penetration of solution colorante), ASTM F2095-2013 (by means of introduction of pressesure of air), ASTM F2096-2011 (entering pressesure of air in the container submerged in water to evaluate the generation of bubbles), etc.

To the equal that in the previous case, does not exist a specific norm that detail all the controls to realizar on this type of containers, although specific associations, like the PBI (plastic Bottle Institute) propose some methods of essay for these products (especially, for PET). In this case concrete, the product contained in the bottles also will condition the essays to realizar, since, for example, if the product contained is milk, will be critical to control the opacity of the container to avoid phenomena of degradation by effect of the light, whereas if the product is a drunk carbonatada, will be critical other variables, like the resistance to the internal pressesure of the container.

Of general way, some of the most common essays that realizar on bottle are the following:

• Resistance to compressesion (same utility and norm that in the case of the trays pelables, already mentioned).
• Resistance to impact by free fall.
• Dimensional control (especially in the zone of thread, to guarantee the correct adjust with the cap after the packaging).
• Forces of torque: To determine the resistance of closing/ opening of the cap. It determines according to the norm ASTM D 2063-2012.
• Resistance to the release of tensions by active environingingment (stress cracking): it determines mainly for bottles that contain chemical products, cleaning products, etc. Measures the resistance of the container to the simultaneous action of mechanical and dissolvent tensions. They exist diverse norms for his determination, being one of the most used the norm JOINS 53975:2007.

Aimplas Has of the necessary equipment for the realisation of the controls of pertinent quality especially type of containers, being the European laboratory with more essays accredited by Enac according to the ISO 17025 in plastic materials. Some of the necessary essays for these controls find inside the scope of accreditation, and have of the necessary technical capacities for the advice to companies about the most adapted essays in each concrete case, advice that covers from the study of the most adapted analyses in front of his needs, like the learning and assistance in the acquisition of equipment for the realisation of said essays, until the study of cause of problems in the containers, with the end to improve the quality of his products..