Materials Testing: Are You Stressed Out? - Bioscience Labs
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Materials Testing: Are You Stressed Out?

Posted On: Nov 19, 2015

Materials testing is defined as the measurement of the characteristics and behavior of substances under various stressful and non-stressful conditions. The data obtained is often used in specifying the suitability of materials for various applications. Most materials are at some point tested for their ability to perform their intended task. From concrete and steel used in buildings, to bandages, medical devices and the packaging they come in – all are tested during some stage of design, development or production.

Materials testing breaks down into five major categories:

  1. Mechanical testing: Static Tension, Compression, Shear Strength, Tensile Strength and Fatigue testing are all examples of mechanical properties testing.
  2. Testing for thermal properties: Thermal Conductivity and Thermal Expansion testing are used to evaluate how heat interacts with materials.
  3. Testing for electrical properties: Electrical Conductivity is often tested in conjunction with heat stress.
  4. Testing for resistance to corrosion, radiation, and biological deterioration: Biological deterioration is a fairly new area of focus and is of particular interest to the world of antimicrobial products. Molds such as Aspergilla and Penicillium are known to cause biological deterioration of many materials.
  5. Non-destructive testing: Because strength testing results in the destruction of the test material, other non-destructive testing methods have been developed to assess certain properties without destroying the material. These include liquid tests to detect fractures, X-ray or Gamma ray which can give a 3D view of flaws, Ultrasonic inspection and Infrared technologies that are used to detect material continuity.

Standard test methods to guide the above categorical testing have been established by such national and international bodies as the International Organization for Standardization (ISO) and ASTM International (formerly the American Society for Testing and Materials). While most of us who reside in the world of antimicrobials are extremely familiar with both ISO and ASTM methods, neither organization is limited to our industry. There is a method for almost every test that can be performed in a laboratory and there are many methods that have crossover functions.

This crossing over between industries is very apparent when you look at the medical field. Medical devices and wound care products are subject to materials testing and many will require antimicrobial testing as well. The 510(k) submission process relies heavily on testing of these products for both antimicrobial efficacy and material properties. Manufacturers will navigate this complicated process by devising a “Testing Plan” that will outline what tests are needed to satisfy the FDA’s intent and most of time, if not in all cases, the Plan will include both types of testing for medical devices, including wound care products.

Another area where the world of antimicrobial testing and materials testing meet is in the area of packaging. Sterile packaging is often integral to the integrity of certain medical devices and wound dressings. ISO 11607 addresses the properties of sterile packaging. While ISO 11607-1 outlines requirements and testing methods used for packaging intended to maintain the sterility of terminally sterilized medical devices until the point of use, ISO 11607-2 is the related standard used to validate the packaging process. This includes forming, sealing, and assembly of preformed sterile barrier systems, and packaging systems. Along with the above mentioned ISO standards, sterilized medical device packaging should also be tested according to ASTM Method F88, Seal Strength Testing for Flexible Barrier Materials.

A few examples of other packaging testing methods that are of particular importance to medical devices and wound care products are:

ASTM D4332, Standard Practice for Conditioning Containers, Packages, or Packaging Components for Testing, is the standard test to measure your adhesive products against temperature and humidity.

ASTM D3330, Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape, is the standard commonly used to measure the bonding strength of tape.

ASTM D5035, Standard Test Method for Breaking Force and Elongation of Textile Fabrics (Strip Method), is used commonly when determining the breaking force and elongation of most textile fabrics.

ASTM F2256, Standard Test Method for Strength Properties of Tissue Adhesives in T-Peel by Tension Loading, is the most often chosen method for evaluating tissue adhesives intended for use as surgical adhesives or sealants, or both, on soft tissue.

These are but a few examples of ASTM methods available for Materials Testing.

A practice that is becoming more and more common with sterile packaging is to add an antimicrobial agent to the packaging process to maintain sterility after the product is packaged and opened again for use in situ. If the use of an antimicrobial agent is employed by the manufacturer, then microbiological testing is also a part of the testing plan. Bacteriostatic and bactericidal efficacy is validated using such methods as AATCC 147, Kirby-Bauer test and AATCC 100 in the in vitro laboratory setting. Other testing methods commonly used for validation are ASTM G21, ISO 20743 and ISO 22196.

From suture materials and wound dressings, to dental implants and sterile packaging, materials testing is a significant portion of the evaluation process required for those products categorized as “Medical Devices.” There may be a significant advantage to combining the laboratory evaluations of these products to include both antimicrobial and physical properties. It could result in a savings of both time and money as you develop your testing plan.

Written By: Leta Eng- Sales Executive