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Foaming polyolefins | technical paper compared to 20.3 kg/m3 with 2202UMS. Although it has

a lower density, the foam produced with 2202UMS shows higher compression stress. This compression stress is 5-20% higher, depending on the compression. Resilience: The resilience has been measured

according to ISO 7217 / ISO 3386-1. The product is compressed at 10, 25 and 70% of its original thickness. This test is repeated four times, and the difference between the original compression stress and the last compression stress is calculated. The lower the differ- ence, the better the resilience of the material. In Table 7, a regular foam with a density of 22 kg/m3

is compared to

foam produced with grade 2202UMS with a density of 20 kg/m3

. In this situation, the average resilience for the

product based on 2202UMS shows improved values after four compressions.

Evaluation, discussion and continuation Laboratory tests, with small output ranges of around 10kg/h, can be used to evaluate different materials with regard to the foaming process. Models can be estab- lished for density, number of waves and cell size. The analysis of the density shows that it depends

mainly on the nucleating agent and isobutene concen- tration. The choice of resin shows a lesser, but still significant influence. Low density values are achievable using 2202UMS. After some years of development and commercial

use, it has been show that Sabic’s LDPE UMS grades provide the PE foam industry with good opportunities to improve processes and products. The theoretical benefits of 2202UMS are demon-

strated in the design of experiments. These benefits correlate well with the results shown in practice. The grade can be used to increase production efficiency or improve product qualities. In some situations, it is possible to achieve both. Some of the advantages of the UMS grades that have

been demonstrated at different production sites in Europe are listed below. These are compared to the use of regular PE grades: l Lower product density l Increased line speed l Less web-breaks in case of physical foamed sheet l Better processing window l Lower average cell size (even with lower density) l More homogeneous cell structure l Better compression stress l Better resilience Currently, the PE foam industry is mainly using the

UMS grades to increase production efficiency. However, the grade can also be used to optimize product properties, for instance through controlling the thermal

Table 6: Compression stress Grade

2102TX00 2202UMS

Table 7: Resilience Grade


Regular after 4x compression 2202UMS

Stress@10% Stress@20% Stress@50% (N)

80 95

(N) 150 170

(N) 525 550

Stress@10% Stress@20% Stress@50% (Index)

100 32

100 2202UMS after 4x compression 38

(Index) 100 63

100 78

conductivity or fire behaviour of the foam. Improving product properties with lower product densities is a desirable goal for the foam industry. This DOE work is going to be expanded with research

into the influential factors of production with UMS grades and GMS. This will give a more complete model and will have a better fit with practice. Further develop- ments of UMS grades are a logical continuation of the achievements so far achieved.

Company and author notes Saudi Arabic Basic Industries Corporation (Sabic) is a global polyolefin producer with more than 40 years of LDPE foam experience. Its Global Foam Technology Centre is located in Geleen, the Netherlands. John Krist (above) is staff

scientist for Sabic Technology & Innovation, responsible for the company’s Global Foam Technology Centre. Emanuel van der Ven (below)

is responsible for technical marketing for foam, master- batches and geoliners at Sabic. The authors thank DSM

Resolve for help in analysis of the models and critical evalua- tion of the paper, the Sabic Foam Technology Centre and IKV laboratories for the foam trials. ❙


[1] New developments in high melt strength polyolefins for foaming; Blowing Agents and Foaming Processes 2008; Krist and Sengupta; 20-21 May 2008

[2] How to choose a Polyolefin grade for Physical Foaming, Important parameters for the Physical Foamability of Polyolefins; Blowing Agents and Foaming Processes 2005; Henk Ruinaard

January 2013 | COMPOUNDING WORLD 55

(Index) 100 96

100 97

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