The world of flexible plastic devices is vast and ever increasing. The choices for disposable medical devices utilizing some sort of cable assembly are numerous. These types of products need to be reliable, effective, quality-oriented and cost effective.
Fortunately, there are several material choices that are well suited to match these performance and quality objectives. From a plastic disposable standpoint, there is none more suitable for a wide variety of devices than PVC (polyvinyl chloride).
PVC has acquired a bad reputation for some compounds and formulations in the past. However when properly qualified by design, it is an excellent choice for most disposable and some reusable applications. The overall design dictates the risk level analysis and suitability for use.
The typical formulation of flexible PVC consists of rigid PVC resins combined with components that offer flexibility, which are called plasticizers. These main ingredients along with fillers, stabilizers, UV additives, and colorants, round out the main ingredients list. The plasticizer component is one of significant importance and fulfills a very wide option of hardness, from taffy-like softness to stiffness and abrasion-resistant durable cable. These characteristics can apply not only to the flexible conductors, but also to flexible and rigid over-molds on plugs and connectors. These plasticizers are usually expressed with common options as phthalate or non-phthalate formulations (typically pronounced commonly “ THa–LAte” ).
These compounds are qualified for use by several tests and measurements that are often needed for full product acceptance. The type of use, medical procedure exposure, and duration of use are of particular interest. Several PVC formulations today have restrictions in place to prevent inappropriate formulations from being qualified for certain products. Many legacy plasticizers were successfully qualified in the past (some with extensive qualification protocols) for heavily weighted performance and cost characteristics. New formulations are now being promoted with primary goals of human safety, fitness for use, longer term handling, low residues, non-migratory compounding, along with sterilization performance and cost.
Testing of compounds are typically in accordance with industry specifications such as biocompatibility and toxicity, among others (ISO 10993) and medical material grading and classification USP(United States Pharmacopeia) class levels (1 through 6) emphasizing exposure limits, handling and chemical safety for human exposure of various types and procedures. We have seen many qualifications specifying the exact type of plasticizer to be utilized, as well as back up testing on not only the plasticizer but additives and colorants.
In 2019 and beyond, the level and scope of qualifications and supporting test data or conformance testing is increasing. Identifying the tests and formulations is a smart strategy during start up, first article inspection, and validation, as well as some ongoing sampling. It is exactly this upfront work and documentation that pays dividends in the long run, answering questions that are not left to chance and providing a good baseline for future tests, inquiries and formulation comparisons.
So… What’s in your plastic? Better to find out in the qualification stage!
Bob Gray, CTO