Inorganic Fillers

• Oxides - Glass (fibers, spheres, hollow spheres, and flakes), MgO, SiO2, Al2O3, and ZnO

• Hydroxides - Al (OH) 3 and Mg (OH) 2

• Salts - CaCO3, BaSO4, CaSO4, phosphates, and hydrotalcite

• Silicates - Talc, mica, kaolin, wollastonite, montmorillonite, feldspar, and asbestos

• Metals - Boron and steel

Organic Fillers

• Carbon, graphite - Carbon fibers, graphite fibers and flakes, carbon nanotubes, and carbon black

• Natural polymers - Cellulose fibers, wood flour and fibers, flax, cotton, sisal, and starch

• Synthetic polymers - Polyamide, polyester, aramid, and polyvinyl alcohol fibers

Fillers are employed to obtain any or combination of the following effects:

• Lower Cost

• Improve rigidity, stiffness or hardness

• Modify rheological properties (flow, thixotropy)

• Modify appearance (opacity, color, texture)

• Regulate shrinkage and thermal expansion

• To improve heat resistance

• To improve the electrical characteristics

• Increase strength and reduce creep

• Aid processability (lubrication, flow, mixing, dispersion etc.)

• Alter density and bulk

Radiopaque additives Devices like catheters, guide tubes, surgical tools, dental products, stents and balloons that are used inside the body, in many cases, need to be opaque to fluoroscopy or X-rays so that the surgeons are able to see the devices as it is guided through or placed in the body .Most plastics are transparent to X-rays and require additives that are radiopaque. The most common radiopaque additives are given below which render the plastic visible under X-rays and work as well as lead without any of the toxic side effects or disposal concerns.

1. Barium sulphate is the most commonly used radiopaque additive with a particle size ranging from 0.5 to 2.0 µm. It can be incorporated into a polymer at high loading level (approx 60%) without significant loss in physical properties of the polymer. It is also resistance to acids and alkalies and has very good weathering resistance.

2. Bismuth compounds are also used as radiopaque additives. They are denser than barium sulphate. The same level of radiopacity can be obtained with lower loading levels of the bismuth compounds compared to barium sulphate.

3. Tungsten has a specific gravity of 19, twice that of bismuth compounds. Low loading levels of tungsten are required to obtain the same level of radiopacity while still maintaining good physical and mechanical properties. Tungsten is used in thin walled applications (0.1-0.2 mm wall thickness)

4. Tantalum has been used as a radiopaque additive on bone cements.

Indian and International Survey

Customized polymers filled with required amount of barium sulphate are being manufactured out of India. There are many industries manufacturing barium sulphate in India but very few manufacturing barium sulphate filled thermoplastic polymers. So development of these types of polymers will help to develop a new area of business in Indian market. These types of customized polymers are already being used in the medical devices and so usage of them will be in demand.

Plastics in medical devices

• 20% of all plastics (Nylons, polyesters, PC , polyurethanes, Acrylics, Acetals) Surgicals instruments, balloons, blood set components, blood bowls, blood oxygenators, syringes, moving parts and components, catheters.

• 10% of all plastics (Polyimides, Polyetherimides,, Polyetherether ketones, polyphenylene sulfide, Flouropolymers, Liquid crystalline polymers, Biopolymers, Thermoset and adhesives) Surgical instruments, Surgical trays, Syringes, Implants, Dental implants, Bone implants, Moving part and components, High precision parts, Electronic components.

• 70% of all plastics (PE,PP,PS,PVC) Tubing, films, packaging, connectors, labware, IVbags, catheters, facemasks, drug delivery components, housings, membranes, sutures, syringes.

Advantages of using plastics in medical device

1. Design flexibility

2. Miniaturization of components

3. Light weight

4. Electrical insulation and conductivity

5. Thermal insulation and thermal conductivity

6. Color

7. Ability to be metalized

8. Transparency

9. Water resistance

10. Chemical and lipid resistance

11. No allergic-Fungus resistance

12. Mass produced and low cost to produce/economies of scale

13. Design freedom

14. Ease of processing and processing methods, processibility

15. Fillers and additives to tailor properties Bondability

16. Sterilization

17. Glass and metal replacement