Packaging film, bottles, rigid containers and closures can all be made from polyolefins, yet each requires materials with different properties. That is why, when selecting a resin for the production of food-contact packaging, it is not enough to simply decide between LDPE, HDPE and PP. You also need to take into account the processing technology, the parameters of the specific grade, the type of food being packaged, and the conditions under which the finished packaging will be used.
LDPE, HDPE and PP – how do they differ in packaging production?
LDPE (low-density polyethylene) is flexible and is widely used in the production of films and flexible packaging. When a product calls for a material that deforms easily and performs well in film extrusion processes, LDPE is one of the primary polymers to consider.
HDPE (high-density polyethylene) offers greater rigidity and mechanical strength than LDPE. It is used, among other things, in the production of bottles, containers and other rigid packaging manufactured by blow moulding or injection moulding.
PP (polypropylene) combines low weight, rigidity and relatively good resistance to elevated temperatures. It is used in applications such as containers, cups, caps and closures, as well as other packaging components.
In practice, then, the name of the polymer only defines the starting point. The next step is to select a grade suited to the production process and to the parameters of the finished product.
Not just the type of polymer. Why does the specific grade matter?
Two resins both designated as PP or HDPE will not necessarily behave identically on the production line. Individual grades differ in their processing parameters and may be intended for different moulding methods.
One of the parameters analysed when selecting a material is the melt flow rate, MFR/MFI, which describes the behaviour of the molten polymer under defined test conditions. Its appropriate range depends, among other things, on the processing technology and the design of the product. A material intended for blow moulding is expected to have different properties than a resin for injection moulding, and different again from one used in film production.
For this reason, purchasing a material solely on the basis of the designation “HDPE,” “LDPE” or “PP” may be insufficient. Before ordering, the technical data sheet of the specific grade should be compared against the requirements of the process.
What changes when packaging comes into contact with food?
In the case of food packaging, a second level of verification comes into play: the safety of the material under the intended conditions of food contact.
On the European Union market, the applicable rules include the general requirements of Regulation (EC) No 1935/2004 and, with regard to plastic materials and articles, also Commission Regulation (EU) No 10/2011. These regulations govern, among other things, the composition of materials and the migration of substances from the plastic into food.
The designation of the polymer type should therefore not be treated as automatic confirmation that a material is suitable for every food packaging application. Factors such as the type of food, the duration of contact and the temperature all matter. The compliance documentation should correspond to the material’s actual application.
How to select a resin for a specific type of packaging?
Before sending an enquiry to a supplier, it is worth preparing the basic parameters of the project. The more precisely the application is defined, the easier it is to narrow the choice down to the right materials. In practice, this information also forms the basis of the conversation with the raw material supplier, who can relate the technological requirements to the available grades and their documentation.
- Type of packaging – film, bottle, container, cup, closure or other component.
- Production technology – e.g. extrusion, injection moulding or blow moulding.
- Mechanical requirements – including the expected rigidity, flexibility and strength.
- Processing parameters – including the MFR/MFI range appropriate for the process and other properties specified in the technical data sheet.
- Food-contact conditions – the type of product and the duration and temperature of contact.
- Documentation – information that makes it possible to assess the compliance of a specific material with the requirements of a given application.
A specification prepared in this way makes it possible to compare not only the price of the raw material, but above all the materials that genuinely meet production requirements. This is also the model in which Nutri Partners operates, supplying raw materials to B2B customers and supporting them in areas such as sourcing, technical documentation and delivery logistics.
The price of the resin is not the only selection criterion
At high volumes, even a small difference in the price of a resin matters; however, replacing a proven grade with a cheaper equivalent may require a fresh assessment of its behaviour in the process and of the properties of the finished packaging. The repeatability of successive batches, material availability and the documentation accompanying deliveries are equally important.
For this reason, a manufacturer should take a broader view of resin procurement: as one element of the entire technological process and supply chain. What matters is not only the polymer itself, but also the availability of the right grade, the stability of supply and the ability to match the material to the actual requirements of production.
The https://nutripartners.co/product-category/industrial category includes LDPE, LLDPE, HDPE and PP, among others. When submitting a request for quotation, it is worth indicating not only the type of polymer sought, but also the processing technology, the intended application of the finished product and the key material requirements.
The packaging first, the resin second
When selecting a material, it is worth reversing the usual order. Rather than starting with the question “LDPE, HDPE or PP?”, you should first define the finished packaging, the way it will be produced and the conditions in which it will be used. Only on this basis can you choose the polymer family, identify the right grade and verify the documentation. This approach reduces the risk of purchasing a material that, while belonging to the right group of plastics, does not suit the specific process or application.
If you are looking for LDPE, HDPE, PP or other raw materials matched to a specific production process, take a look at the Nutri Partners offer and get in touch with the team, setting out your technical requirements and the material’s intended application.
