Plastic materials in packaging and closures of packaging
Whether we want it or not plastic has been with us since the very beginning. We begin with pacifiers, baby milk bottles, nappies and most of all, toys changing with our age but making our life pleasant. It is difficult to find an everyday use item whose even a part contains no polymer material at least in the form of the glue. All our daily activities depend on plastic to a greater or lesser extent. If we want water to run from the tap or the opposite, stop it safely, polyvinylchloride pipes as well as synthetic India rubber gaskets play a vital role.
Detailed observation of elements of the world made by a human being will make us realise that plastic is omnipresent! Unfortunately, we are unable to eradicate it. Therefore, we had better get to know it, start to like it and learn how to use it! We had better understand the advantages it provides. However, when it is useless we should dispose of it safely or even better recycle it!
There is a wide range of plastic materials, from soft and flexible through hard and resilient to strong blows, up to aramides resistant to fire or shots of handheld firearm.
Differences in physical-chemical properties depend on, among other things, the composition of molecules (mer units) as well as the conditions of the polymerisation process (pressure, temperature and time), additives (e.g. antistatic agents, antioxidants, plasticisers, thermic stabilisers, boosters) as well as on the blend with other materials (metal, concrete, other plastic materials).
In the closures of packaging themselves and cosmetic packaging we have a few or more different polymer materials. Their characteristic features are used to the comfort and safety use of the final product.
Lotion pump, mist sprayer and airless packaging under scrutiny
Lotion pumps and mist sprayers are practical closures of bottles, which are used both in food products as well as in cosmetics. They are made of more than ten tiny elements, which when matched adequately dose liquids or semi-liquids.
Elements visible at first glance such as a head, closure and optionally occurring overcap as well as an actuator, by which the medium is finally dosed, are most often made of polypropylene, marked with PP symbol. Physical-chemical properties of the material make it perfectly suitable in the production of elements which come in contact with cosmetics or food. It is durable, odourless and, what is more, it does not corrode. However, after adding antioxidants and UV stabilisers, its resistance to oxygen or solar radiation is adequately high. Another advantage is its ease of colourisation and metal spraying. Polypropylene belongs to thermoplastics, which means that after heating it becomes liquid, making it prone to any shaping by pressing or injecting. However, this property is shown in the temperature over 100 degrees Celsius. In lower temperatures it is stable and fully resistant to acids, alkalis, salts or organic solvents.
In lotion pumps and mist sprayers we can also find polyethylene (PE). It is one of the most popular substances in the world of plastic materials. Different ways of obtaining it determine the properties of particular sorts of polyethylene. Its basic form, which is obtained in 30 atm conditions, is flexible, odourless, dust-free but above all, resistant to a number of exterior factors such as the influence of acids, alkalis, salts, mould, damp or scratches.
High pressure during the reaction allows to obtain LDPE of low density, which is transparent, soft and elastic. The piston, which is inside lotion pumps and mist sprayers, is made of high-pressure polyethylene, owing to which it does not crack or break under the influence of the spring. Tubes which are elements of dosing mechanisms are also made of LDPE, whose permanent features such as low barrier and chemical resistance comparable to PE, guarantee the reliability in the functioning of these elements. Polyethylene occurs in the foamed way making it soft, elastic, yet durable, tightening the whole closure system. To make lotion pumps and mist sprayers work properly they contain a spring made of stainless steel as well as a glass ball, the only two elements made of natural materials.
Cosmetic packaging of airless packaging type appears to be another example showing the necessity of the use of several kinds of plastic materials in a relatively small product to achieve the reliability of functioning as well as the effective look. Polyethylene and polypropylene find their use in analogical places to the above analysed mist sprayers and lotion pumps. Two differences are the most important: the airless packaging does not contain any tube, the bottle does not make the integral part of mist sprayers or lotion pumps whereas they do make it in airless packaging. The piston is the most crucial and characteristic part of that sort of packaging. Hidden in the inside the bottle, the most frequently made of LDPE, it is responsible for pushing the medium outside.
Depending on the visual effect we are willing to receive we choose the adequate material of the exterior of the bottle, and also the cap to maintain the style. It, in turn, leads to material novelties.
If it is to be shining and crystally transparent – then polymethyl methacrylate, also known as organic glass, plexiglas or acrylic glass will be applied. Besides permitting 90% of visible radiation it is highly resistant to the influence of acids, alkalis and low temperatures. Yet another advantage is that it does not yellow under the influence of UV radiation.
The only drawback of the PMMA is its susceptibility to scratches. Hence, AS- styrene copolymer and acrylonitryle is recommended as a substitute, whose greater resistance to mechanical damage completes the set of PMMA attributes. Both materials are equally suitable to colouring as well as may undergo processes such as hot stamping, uv plating or softtouch.
If the effect is to be moderate and the label is planned to take the majority of the packaging space, then the best material would be indefectible polyprophylen. Its features used in the elements of the mechanism which are, among other things, high resistance to the impact of acids, alkalis, salts and organic solvents will prove ideal in the bottle and the results of global migration tests will be more than satisfactory!
Another solution is the use of ABS which is acrylonitrile-butadiene-styrene terpolymer, whose features allow it to be used in the cosmetic industry. However, one should know that it is not a type of material resilient to the impact of organic solvents. Moreover, UV stabilisers should be added to preserve the colour.
The topic of airless packaging as a type of packaging, its characteristic features has been further discussed here.
The process of designing of the cap or the whole packaging seems to be mostly focused on the aesthetics as well as the size suitable to our product. In fact, it is a multidimensional process, which requires both watchfulness and time. After choosing the packaging it is necessary to carry out a set of tests on the final outcome, among others, migration testing, compatibility and stability testing as well as aging tests. Their positive results in lab conditions may be a guarantee of the problem-free effect of the product in the domestic conditions. The closure of the packaging must be adjusted to the density of the product for the comfort and effectiveness of dosing.
Planning the product and its packaging involves foreseeing various, seemingly unpredictable situations, for instance, a beach or a car parked in the sun, where cosmetics are exposed to extreme endurance tests. When choosing plastic materials and additives in the packaging it is vital to take into account such extreme situations as well as factors related to the everyday use.
Upgrading may be an example. Applying a layer of aluminium on the material may be a good idea. However, some examples of combining the product of low density and metal may be fatal. Pouring water even accidentally but gradually may cause stratifying of those two materials, which in turn, may lead to getting of the metal filings to the substance used and, as a consequence, to face or other body parts. Even if little amount of aluminium causes no harm to the consumer, the look of such packaging will discourage him or her from another purchase.
It is obviously difficult to predict many extreme situations or exclude their negative impact on our product but simulations in specialist laboratories allow to test the reaction of the product in the part of unconventional conditions.
Our sales managers are eager to advise. Additionally, if the situation requires specialist advice, our quality control department supports them with their knowledge and experience.
