ADVERTISEMENT FEATURE
Halogen-free flame retardants for foamed PP parts and films
Unipetrol is developing a halogen-free flame retardant solution for expanded PP and thin polyolefin films
Automotive applications account for up to 10% of annual polymer consumption and demand from the sector is increasing, with one of the fastest growing areas being lightweight parts. These expanded foamed parts provide required mechanical and physical properties together with a weight reduction and material cost saving. However, such benefits must be delivered while maintaining low flammability. Total flame spread and even final
burning rate of a traditional compact plastic part can often be corrected by adjusting the wall thickness – increasing wall thickness decreases burning rate. In this way, the basic classification of burning rate according to international standards such as FMVSS 302, TL 1010 or ISO 3795 can be met in many polymeric parts without the addition of flame retardants. Expanded lightweight parts are typically produced with higher wall thicknesses, but most of their interior volume is “polymer-free”. An expanded lightweight part, therefore, displays flammability characteristics more like a thin sheet or film. Meeting the UL94 HF-1 classification for expanded foamed parts, which calls for near non-flammability and self-extinguishing properties without flammable liquid dripping, can represent a problematic issue. Self-extinguishing properties can
currently be achieved in PP using standard halogenated flame retardants in combination with antimony trioxide. The disadvantage is the growing concern over the accumulation of such additives in the environment and the inference of local toxicity. Therefore, the use of halogenated and antimony retardants is in decline and manufacturers are trying to replace them with lower environmental impact halogen-free additives.
A typical feature of many halogen-
free flame retardants (HFFRs) is their ability to release water molecules at the burning temperatures of plastics, which reduces the heat of exothermic reaction from the system. However, to achieve high efficiency, such HFFRs have to be dosed at large amounts. This can negatively influence mechanical and polymer melt flow properties. An alternative HFFR approach is based
on the formation of an intumescent carbonised layer on the surface of the product, which prevents oxygen diffusion to the combustion center. However, a high mass of polymer is required to form such a layer, so the effectiveness decreases in lightweight and thin applications such as films.
The eco challenge The challenge is to find suitable eco- friendly additives based entirely on halogen-free formulations with a balanced content of synergists. The resulting solution should meet the highest non-flammability class, but should not affect the mechanical, thermal or processing properties. Unipetrol RPA is developing new halogen-free and eco-friendly flame retardant formulations for lightweight
www.unipetrol.cz/en
products, polymeric foams and thin films based on PP and PE. In cooperation with leading Czech manufacturers, the company in developing a new solution that meets most of the required specifications (before validation and launch, however, it will be necessary to further reduce the amount of non- flammable drips). The synergistic additives used have high heat resistance, low extractability in water, and most of the organic solvents are soluble in the polymer during processing, which improves surface quality. Due to its low extractability and migration speed, the final product also meets strict criteria for migration limits and odour tests. From a flammability point of view, the
additive system is able to meet the highest non-flammability classifications for lightweight and thin film materials, including HF-1 and the VTM-0 standard horizontal burning rate test with a limit value of 80 - 100 mm/min. The innovative additives also aid the process of foaming and film stretching.
After completion of the development,
Unipetrol intends to supply the new material as a ready-made compound or in the form of a masterbatch with a dosage level of up to 30%.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70
