Conventionally, linear low-density polyethylene (LLDPE) with a melt flow index (MFI) of 3–5 is most used in rotational moulding due to its flexibility and impact resistance. However, this material is not without its shortcomings. In some of the most demanding applications, LLDPE might not have sufficient strength to withstand the harshest environments.
The challenge
A polymer with low MFI indicates low flowability in the molten state, translating to harder processing. However, low MFI usually corresponds to higher molecular weight, which translates into more chain entanglement within the polymer. This results in material with good mechanical properties, such as strength, toughness, and impact resistance, but poor processability. This leaves a gap in material with good processability and elevated mechanical properties for demanding applications.
The solution
Hyperene HD6756 is a premium high-density polyethylene (HDPE) formulated with high MFI and elevated mechanical properties compared to LLDPE. This improves material processability, enabling it to cover complex geometries while maintaining consistent wall thickness and potentially reducing cycle time. In the case of kayaks, the elevated flexural modulus of Hyperene HD6756 enables it to withstand higher load capacity without bending. Increased impact strength allows kayaks to withstand collisions and drops without cracking. High tensile strength ensures structural integrity when the hull of the kayak flexes, preventing the ‘oil-canning’ phenomenon.
Integration of our UV stabiliser additive masterbatch in our formulation is one of the keys to the solution. It ensures kayaks are shielded from UV radiation exposure damage, allowing them to maintain structural integrity and vibrant colours over time.
Our thermal stabiliser additive masterbatch also contributes to the success of the solution. With thermal stabilisation, it prevents polymer degradation during processing, allowing a wider processing temperature range, further contributing to the ease of processability.
Our in-house custom colour masterbatch is an essential aspect of the solution. Not only do the bright colours bring fun, adventurous character to kayaks, they also serve as a safety feature, allowing them to be more visible to others, especially in low light, fog, or rough seas.
Our in-house custom colour masterbatch is an essential aspect of the solution. Not only do the bright colours bring fun, adventurous character to kayaks, they also serve as a safety feature, allowing them to be more visible to others, especially in low light, fog, or rough seas.
Hyperene HD6756, a high-MFI HDPE, bridges this gap by offering improved processability paired with higher flexural modulus, impact strength, and tensile strength, making it ideal for complex parts for the harshest environments. Integrated UV and thermal stabilisers enhance durability during outdoor use and processing, while custom colour masterbatches provide safety and aesthetic benefits.
Kayaks showcased in this case study are made with Hyperene HD6756 by Feelfree Kayak.
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