Polymer suppliers

This presentation discusses testing implications of the new directive to determine compliance for additives in food contact applications, the responsibilities of the converter and polymer supplier with reference to demonstrating... 

There has been a stream of new product and technology development by leading biodegradable polymer suppliers that have opened up new markets and potential applications. 

Table 4.2 shows the major biodegradable polymer suppliers by product type for 2005. 

The leading biodegradable polymer suppliers are Novamont, NatureWorks, BASF and Rodenburg Biopolymers, which together represent over 90% of the European market for biodegradable plastics. 

In addition to those standardized tests, two other test methods, monotonic creep and microhardness, have been developed by Hough and Wright [48]. In the monotonic creep test, the strain response to a constant stress rate is monitored. The deviation of the stress-strain characteristics in air and in the fluid of interest is taken to be the initiation of ESC. This method is shown to differentiate to a high resolution between polymers, and in the short term, the ESCR of polymer/fluid pairs that exhibit mild/weak interactions can be distinguished. The microhardness method, in which a pyramidal diamond indentor is pressed into the surface of the polymer component at a known load and for a known time, has the potential for mass screening of plastic/fluid compatibility, including extraction as well as absorption, and should be of interest to polymer suppliers. 

Although data sheets from polymer suppliers are a starting point for information on the properties of polymers, there is always a chance that materials may modify at least slightly during any conversion or treatment process. Such potential changes have to be checked by more and more sophisticated analytical methodology. This has to be supported by more in-depth knowledge of the polymers themselves. 

Appendices 8.11, 8.12 and 8.13 open up a relatively new topic where a possible technical gap between the information given in polymer supplier data sheets and the properties of the plastic used in the final pack can be identified. 

The three polychoroprene compounds came from the polymer supplier and were labelled general purpose (L), natural ageing (M) and heat ageing (N). 

The EDA approved PEN for food contact appiications in Aprii, 1996. PEN and PET can be blended together to make useful materials, and also PEN/PET copolymers can be produced. When PEN/PET blends are used, one is really making copolymers in the extruder. Analysis of the material that is extruded shows that transesterification reactions occur in the extruder, forming molecular bonds between PET and PEN molecules. Therefore, processing conditions are important to the quality of product one makes when using blends. Blends, as well as copolymers manufactured by polymer suppliers, can open up markets for this polyester that are not accessible to PEN alone because of its high price. While these materials have not yet been approved for food contact applications in the U.S., there appear to be no technical barriers to their approval. 

Testing to failure under service conditions is time consuming and costly and consequently most component manufacturers rely on information from polymer suppliers. This at best can only be a guide to component performance and the polymer technologist who wishes to know more about the environmental behaviour of his material must rely on lifetime prediction from accelerated tests. These are of two types, the... 

Comparative aging results, reported in Table I, were performed on many commercial and selected experimental polymers. These were in most cases used as recieved from the suppliers. A partial list of polymer suppliers includes Aldrich, Allied Colloids, American Cyanamid, Betz, CORT, Dow, DuPont, GAP, Hercules, Jetco, Kelco, Nalco, Pfizer, and Union Carbide. 

The major polymer suppliers in Europe and the US have been consolidating for many years. They have reduced e number of grades of polymer they offer, leaving independent compoimders to provide differentiation. BASF has announced a huge reduction in the number of ABS products it offers, while maintaining that the reduced range will still meet the needs of 80% of its customers. 

Even market leaders such as Clariant, Ciba Specialty Chemicals and Akzo Nobel have felt the need to cut costs, and in some cases jobs, in the early years of the present decade. A few companies have retreated from chemistry or plastics related markets altogether and tnmed to the life science and health sectors. Polymer suppliers have reduced the number of polymer grades they offer. The compounding industry too has been forced to rationalise, with several plant closures. 

For example, in profile foam operations, where higher density foams are desired, it is general practice to use chemical blowing agents (CBA). These materials, which decompose under polymer melt processing conditions to yield gases to expand the polymer, are usually dry-blended with the resin and then fed to the extruder. They can also be compounded directly into the resin by the polymer supplier and provided as a ready-to-use masterbatch. 

The toxic potential of thermodegradation and combustion products of plastics, when these materials are burned either deliberately or by accident, is also an important consideration in view of the widening use of plastics as structural and decorative lining material in buildings, vehicles, and aircraft. The polymer supplier must thoroughly disclose the toxic ingredients in a plastic formulation and any toxic products that may be released on burning. This is accomplished in the Materials Safety Data Sheet (MSDS), which must be made available on request. 

The prototype was made manually from acetal homopolymer sheet, with advice from the polymer supplier (Du Pont) on the most suitable grade for such a purpose. Its thickness was determined by the thickness of the sprocket teeth 3 mm sheet was used (approx 1/8 inch). The shape, as already stated, was drawn to fit the available space. In use, it will be strained by the rotation of the teeth (Fig. 6.2(b)) which push against the central section, the actual elastic strain occurring in the curved, spring-shaped ends. The critical design parameters were (a) the profile in the centre where the sprocket teeth contact the spring (b) the width of the spring section (dimension a-a. Fig. 6.2(b)). 

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