At PMC Polymer Products, we actively pursue the development of flame retardant (FR) compounds and highly loaded FR concentrates for many resin systems. We do this in concert with our customers and raw materials suppliers – our Product Development Teams are constantly involved in hands-on working relationships, working together to create and deploy unique, customer-specific technology.
To assist our sales staff and customers in establishing exacting requirements for their FR product development projects, we created application worksheets. These worksheets ensure that everyone has the required information early in the development process so we can hit the ground running and meet otherwise impossible schedules.
Let me outline the key features of those worksheets for you.
Economic Considerations is the first item on the worksheet, and for a simple reason. The main issue for any product development manager is formulation cost. Price constraints will have a profound influence on the additives and resins selected for the formulation.
Next come the Basic Characteristics. Establishing the resin type and process information helps us focus in on the FR package we’ll use and the possible need for other additives. For each resin, there are several FR candidates, and subsequent questioning will narrow down the options even further.
My intent is not to discuss the numerous FR testing standards, but to point out what type of information might be required.
Let’s consider, for example, the most common FR test, UL-94. The basic test ratings for an FR-loaded product are V-o, V-1, and V-2. V-0 is the best rating; V-2 is lowest-acceptable rating. Materials that do not meet the V-2 minimum fail.
The main observations from the test are burn time, afterglow, dripping, and whether cotton ignition occurs for samples that drip. V-1 products exhibit longer flame or afterglow times than V-0. A V-2 rating has burn criteria similar to V-1 except that cotton ignition due to flaming drips is allowed. The key information required by the PDM is the deserved rating and minimum thickness. It is important to note that a UL-94 rating does not mean that a product is Underwriters Laboratories Certified. To obtain a “yellow card” for a product requires submission of test reports to UL for evaluation. UL Certification adds time and expense to development costs. And, in addition to minimum thickness and flammability ratings, it specifies product color.
So let’s go back to our worksheet and talk about basic packaging characteristics.
There has been considerable interest in non-halogenated products because of the safety and environmental concerns associated with halogenated products – notably for companies supplying European markets. The main issues associated with non-halogenated materials involve the nature of the FR additive; generally they concern combinations of higher loadings, higher costs, and more significant physical property degradation relative to halogenated materials. Additionally, many non-halogenated raw materials are not capable of being compounded into concentrates.
Molecules based on bromine, and to a lesser extent chlorine, are the workhorses of many FR formulations, and there are usually several different FR options for a given resin system. These choices can easily be narrowed down based on information supplied by the customer: FR rating, price, bloom, UV stability, and the desired physical properties of the final product. The choice might also depend on performance trade-offs, quality, chemical compatibility, availability, or customer preference.
Customer preferences regarding FR selection have usually indicated a desire to NOT have a particular FR in the formulation. The most common of these are the brominated diphenyloxides such as decabromodiphenyloxide and octabromodiphenyloxide. These are often referred to as deca, octa, BBDPE’s, BBDPO’s, DBBPE, DBBPO, ODBBPE, and a number of other descriptors. This group of FRs has gradually been phased out and should not currently cause any confusion.
Customers may still indicate that they want a non-deca product. This usually means that they want a brominated FR but not a diphenyloxide. People occasionally confuse non-deca with non-hal. It is important to remember is that not all non-deca formulations are non-halogenated, but all non-halogenated formulations are non-deca.
While we’re on the subject of FR additives, now is a good time to discuss additional additives that may be incorporated into the formulation to enhance appearance, processing, stability, or other physical properties. Such additives may include antioxidants, UV stabilizers, processing aids, impact modifiers, and pigments. PDMs also need to know if other materials might need to be added during processing. This knowledge helps the PDM determine whether the FR characteristics of the formulation need to be enhanced. Also, keep in mind that these other additives may be more effective if incorporated at the initial compounding stage.
Now, incorporating additives into plastics can affect the properties of the resin itself. The effects may be minimal or they may be significant. They may be positive, negative, or a combination of both.
Knowing the effects of the additives used, coupled with a detailed physical property profile, enables the PDM to select an appropriate base resin for formulation of the product.
Occasionally, it may not be possible to obtain all of the desired physical properties. In these instances, it may be necessary to determine whether trade-offs can be made. It would be beneficial to identify early in the process which factors are critical vs. which ones are merely desired.