How to Ensure Proper Drying of Medical-Grade Plastics

How to Ensure Proper Drying of Medical-Grade Plastics

Understanding Medical-Grade Plastics

Medical grade plastics are used by many medical articles in the manufacturing of MRI machine casing, plastic syringes, and prosthetics due to their unique merits. This, therefore, makes them excellent alternatives for manufacturing medical devices that come into direct contact with the human circulatory system, as they are very effective for biocompatibility. Additionally, this kind of plastic is highly plastic, moderately complex, highly accurate, and easy to mold by injection. Furthermore, it goes well with 3D printing technology, thus providing great convenience and innovation opportunities in the modern medicine manufacturing industry.

Types of plastics used in the medical industry

Many medical-grade plastics are suited for various applications in the medical industry:

The medical industry finds a lot of use for different types of plastics for medical grade:

  1. Thermoplastics are plastic polymers that become soft when heated and hard when cold.
  2. Thermosetting plastics are plastic polymers that become permanent solids when cured.
  3. Elastomers are viscoelastic polymers capable of returning to their original shape and size after being stretched.

However, thermoplastics have the largest market share. Here is a list of seven common thermoplastics used in manufacturing medical components: Seven Commonly Used Medical-Grade Plastics

Polyvinyl Chloride

  • Polystyrene (PS) and K Resin PS are the third most common plastics after PVC and PE, and they are often processed as single-component plastic. It is lightweight, transparent, easy to dye, has good molding properties, and is widely used in consumer plastics, electrical parts, optical instruments, and educational supplies. It is hard and brittle with a high thermal expansion coefficient, limiting its use in engineering applications. In recent decades, modified polystyrenes and copolymers based on styrene have been developed to overcome some of the limitations of PS. K Resin, a copolymer of styrene and butadiene, is an amorphous polymer that is transparent, odorless, non-toxic, with a density of about 1.01 g/cm3 (lower than PS and AS) and has better impact resistance and clarity (80-90%) with a thermal deformation temperature of 77°C. Its excellent flow properties and wide processing temperature range make it highly workable.

Polyethylene

  • Polyvinyl Chloride (PVC)PVC is one of the most produced plastics worldwide. The resin is typically a white or light yellow powder. PVC is amorphous, complex, and brittle in its pure form, seldom used without modification. Depending on the application, various additives can be incorporated, giving PVC diverse physical and mechanical properties. Various rigid, soft, and transparent products can be manufactured by adding appropriate plasticizers. Rigid PVC, which contains little or no plasticizer, possesses excellent tensile, bending, compressive, and impact resistance and can be used alone as a structural material. Soft PVC, containing more plasticizers, increases flexibility, elongation at break, and cold resistance but becomes more brittle, with reduced hardness and tensile strength. The density of pure PVC is about 1.4 g/cm3, whereas plasticized or filled PVC generally ranges from 1.15 to 2.00 g/cm3. Approximately 25% of medical plastic products are made from PVC due to its low cost, wide application range, and ease of processing. Medical applications for PVC include blood dialysis tubing, respiratory masks, and oxygen tubes.
  • Polyethylene (PE)Polyethylene is the highest-produced plastic in the industry, and it appears to be made of milky, odorless, tasteless, and glossy wax-like particles. It is inexpensive, versatile, and significantly used in manufacturing, agriculture, packaging, and daily goods. PE types include Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), and Ultra-High Molecular Weight Polyethylene (UHDPE). HDPE has fewer side chains, resulting in higher molecular weight, crystallinity, and density, contributing to its hardness and strength, making it commonly used for injection molded parts. LDPE has many side branches, giving it greater flexibility, impact resistance, and clarity. It is often used for film blowing and as a widely adopted substitute for PVC. HDPE is known for its high impact strength, low friction, stress cracking resistance, and good energy absorption properties, making it ideal for synthetic joints such as hips, knees, and shoulders.
  • Polypropylene (PP)PP is colorless, tasteless, non-toxic, more transparent, and lighter than polyethylene. It is a superior thermoplastic with low density (0.9 g/cm3), non-toxicity, easy processing, impact resistance, and flexural strength. It has extensive everyday uses, including woven bags, films, turnover boxes, wire shielding materials, toys, car bumpers, fibers, and washing machines. Medical-grade PP is valued for its high transparency, excellent barrier properties, and radiation resistance, making it widely used in medical equipment and packaging. Non-PVC materials based on PP are extensively used as alternatives to traditional PVC materials.

 

  • Acrylonitrile Butadiene Styrene
  • (ABS)ABS is known for its rigidity, hardness, impact resistance, chemical resistance, radiation resistance, and resistance to ethylene oxide sterilization. ABS is primarily used in medical settings for surgical tools, roller clamps, plastic syringes, tool cases, diagnostic devices, and hearing aid casings, particularly for large medical equipment housings.
  • Polycarbonate (PC)PC is known for its toughness, strength, rigidity, and resistance to steam sterilization. It is the material of choice for blood dialysis filters, surgical tool handles, and oxygen tanks used in cardiac surgeries to remove CO2 and increase oxygen levels. PC’s medical applications include needle-free injection systems, infusion devices, blood centrifuge bowls, and pistons. Due to its high transparency, PC is commonly used for prescription eyeglasses.A comprehensive traceability system will enable analysis and improvement whenever required. Equipment Maintenance
  • To prevent any amount of humidity from being reabsorbed, materials must be sealed immediately after drying is finished with them.Both dryers and testing apparatuses need regular calibration and maintenance measures taken on them at all times. Polytetrafluoroethylene (PTFE) Polytetrafluoroethylene resin is a white powder with a waxy, smooth, non-stick surface, making it one of the most important plastics. PTFE has exceptional properties not commonly found in other thermoplastics, earning it the nickname “King of Plastics.” It has the lowest coefficient of friction among plastics and exhibits good biocompatibility, making it suitable for manufacturing implantable medical devices such as artificial blood vessels.

Why moisture control is critical for medical-grade plastics

Preventing Hydrolytic Degradation

Moisture absorption during hot processing is a big issue for medical-grade plastics like Polycarbonate (PC) and Polyetheretherketone (PEEK). The hygroscopic attack causes deterioration in these materials’ mechanical properties and chemical resistance. Consequently, it compromises the final product, thus requiring strict humidity control to maintain its originality.

Guaranteeing Quality Production

Syringes, catheters, implants, and other medical plastic items must adhere to strict quality guidelines. Uncontrolled humidity can cause dimensional distortions, leading to weak products. Incongruent moisture content can also lead to poor biocompatibility and reduced product performance, which is unacceptable in medical applications.

Stopping Bacterial and Fungal Growth

Excessively humid conditions create good habitats for bacterial and fungal growth. Medical plastics must maintain high sterilization rates. Effective manipulation of the moisture content keeps the level of microbial contamination within acceptable boundaries, which preserves the sterility and safety of devices such as surgical instruments.

Optimizing the Processing Process

Moldability in molding processes like blow or injection molding improves with proper humidity control. Dehydration at appropriate levels prevents defects such as bubble formation or surface marks that will result in high-quality outputs.

Conclusion

Stringent humidity control is required for adequate medical-grade plastic products’ performance, dependability, and security. Therefore, they need professional drying equipment alongside accurate environmental control systems that ensure optimal humidity throughout production and storage environments.

Technologies used for dehumidifying plastics (e.g., desiccant dryers, refrigerated dryers)

Desiccant dryers can use desiccants like molecular sieves, which absorb water from the air.

They can achieve low dew points (-40°F or below) necessary for drying materials that attract moisture.

Different types include:

Twin tower/dual bed desiccant dryers (previous generation)

Rotary wheel Desiccant Dryer (more contemporary and efficient)

Desiccant Dryer

Hot Air Dryers  

Hot Air Dryer

Hot air removes surface moisture for non-hygroscopic resins such as polyethylene and polypropylene.

It is more straightforward than desiccant dryers but not as effective in cases with hygroscopic components.

Compressed Air Dryers

They use compressed air, which has been dehumidified during the compression process.

This method is simple and requires little maintenance, though its effectiveness is lower than that of desiccant driers, which may fail to reach the -40°F dew point.

Vacuum Dryers

Moisture removal is enhanced by combining heat and vacuum to remove water at high rates.

As opposed to other methods, it can be much faster and more energy efficient.

Infrared Dryers

Resin pellets are heated through infrared radiation, which causes the evaporation of moisture.

Drying Techniques for Medical Plastics

Syringe Production

Syringe Production: Moisture control during syringe production is vital; hence, the moisture content of raw materials like polypropylene must be regulated. The use of dehumidifying dryers can reduce the moisture content in those raw materials to avoid air bubbles and cracks that could occur during injection molding and thus maintain the transparency and strength of syringes.

Medicine Bottle Production

Medicine Bottle Production: The demand for transparent, non-impurity substances is high during medicine bottle production. Dehumidifying dryers help control the moisture content of raw materials to ensure that there are no water traces or bubble formation when producing, which improves the appearance and performance of bottles.

Disposable Medical Device Production

Disposable Medical Device Production: Moreover, test tubes and droppers, among other disposable medical devices, cannot be produced without using dehumidifying dryers, which are critical in maintaining product accuracy and consistency, as well as ensuring these items meet strict criteria set by the health sector.

Key Factors in Effective Dehumidification and Drying

Temperature Control

Dehumidification and drying require temperature control. The proper temperatures enhance the evaporation of moisture, increasing drying rates.

Heating

Heating allows air to hold more water, hence reducing relative humidity (RH), which in turn promotes the evaporation of moisture from surfaces. For example, it’s most effective to maintain a temperature between 70 and 90 degrees Fahrenheit (21 and 32 degrees Celsius) during structural drying.

Cooling:

Air can be cooled to remove its humidity through a process known as condensation. Refrigerant dehumidifiers operate by cooling air below the dew point, resulting in water vapor condensing on the surface of the condenser and being expelled, thus reducing air’s humidity levels.

Time Management

Effective drying processes also require proper time management. Material and environmental factors determine how long it takes to dry.

Drying Time

Drying time should vary depending on the materials’ initial moisture content and the desired final moisture content. For example, hygroscopic resins such as nylon, ABS, and PET require longer drying times due to their higher initial moisture content.

Monitoring and Adjustment

To ensure that optimal drying results are achieved, you must monitor humidity levels and temperature throughout the drying process or do whatever might be necessary while monitoring them.

Material Handling and Storage Considerations

How materials are handled or stored determines how effective dehumidification and drying will be.

Material Classification:

Classify materials based on their ability to cause hygroscopy. Non-hygroscopic resins may only require superficial drying, whereas hygroscopic resins need to undergo thorough desiccation to eliminate internal moisture.

Storage Conditions:

It is important for storage environments to maintain low humidity levels alongside appropriate temperatures that may prevent the re-absorption of water during storage. Dry air storage is an example of a storage environment where plastic granules can’t become wet.

Packaging:

Material quality can also be protected through moisture-proof packaging, especially during storage and transportation.

Temperature control, time management, material handling, and storage are some of the things that should be given great consideration when it comes to effective dehumidification and drying. The efficiency of the whole drying process depends on proper temperature adjustments, accurate timings, and strict materials handling.

Quality control is necessary during drying to ensure that plastic products are of good quality and performance. Here are some important aspects of quality control in the drying process:

Testing for Initial Moisture Content

Before starting drying, it is necessary to test how dry or wet plastics are. Some of the standard testing methods include:

  • Loss on Drying Method: This approach finds moisture content by heating a sample and measuring weight loss.
  • Karl Fischer Titration: It’s an analytical chemical method for determining trace amounts of water.
  • Near-Infrared Spectroscopy: A quick, non-destructive technique suitable for online monitoring.
  • Moisture Analyzers: These are instruments specifically designed to measure the moisture content in plastic granules. 

Drying Parameter Control

  • Temperature Control: Different types of plastics should be dried at appropriate temperatures to avoid overheating and degradation.
  • Dew Point Control: Dry air used in the drying process usually has a low dew point, ranging from -20°C to -40°C.
  • Airflow Control: Adequate airflow helps effectively remove moisture from plastics during drying.
  • Drying Time Control: Drying periods may vary depending on initial moisture content and target humidity levels sought after

Continuous Monitoring

  • Use online moisture analyzers during the dying process to monitor changes in moisture content.
  • Carry out regular sampling tests to ensure that targeted moisture levels are achieved.

Post-Drying Handling

To prevent any amount of humidity from being reabsorbed, materials must be sealed immediately after drying is finished with them.

      • Details should be kept about parameters per batch, such as;
      • A comprehensive traceability system will enable analysis and improvement whenever required. Equipment Maintenance
      • Both dryers and testing apparatuses need regular calibration and maintenance measures taken on them at all times.

To prevent adulteration, the dryer equipment must be cleaned afterward.

 Future Outlook:    

With the healthcare sector ever-changing and the demand for plastic products on rise, dehumidifying dryers are set to have a wide-ranging future in this area of interest. In addition, dehumidifying dryers will continue to be indispensable in enhancing the quality of these products, increasing productivity, and minimizing manufacturing expenses as we move ahead.   Furthermore, through technological advancements, the performance and effectiveness of dehumidifying dryers shall also enhance satisfying the demand in medical plastics product manufacturing.

 

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