Polyamide, also referred to as nylon or PA for short, is a highly polar crystalline polymer that is reactive when certain circumstances are met. It readily establishes hydrogen bonds between molecules. It offers good molding processability, good corrosion resistance, and outstanding mechanical qualities such as wear resistance, oil resistance, and self-lubrication. However, PA has a high rate of water absorption due to its strong polarity, which has an impact on PA’s electrical characteristics and dimensional stability. Furthermore, PA’s low-temperature impact strength and heat resistance require improvement.
Because of its reactivity, PA is easily modified. Fiber reinforcement, inorganic filler, and other polymers or polyamides can be combined to create composite materials or alloys.
PA filling adjustment
Fibers and artificial or natural fillers are added to polyamide resin, which serves as the foundation material for PA filling modification. Fiber reinforcement, natural mineral reinforcement, and synthetic filler filling are the three general categories into which it can be separated:
(1) Fiber reinforcement can be made of asbestos, carbon, glass, etc.
(2) Calcium sulfate, calcium carbonate, kaolin, talc, zeolite, and other natural mineral reinforcement are used.
(3) Graphite, silicone powder, polytetrafluoroethylene, molybdenum disulfide, and other materials are used in synthetic filler filling.
When fiber and filler reinforced nylon are used simultaneously, the product is frequently more well-balanced and has more comprehensive qualities.
The fillers’ particle size, shape, aspect ratio, and surface treatment agent all affect how reinforced nylon resin is as a result of them. Common filler materials, such as plant fibers, inorganic natural minerals, and leftover industrial waste, can save costs while also improving It decreases impact, tensile strength, surface gloss, and processing fluidity while increasing the mechanical and physical qualities of composite materials.
qualities of fillers and their impact on resin qualities
(1) Particle shape
Larger longitudinal and transverse surface fillers, like fibrous, columnar, and flakes, improve the mechanical properties of PA but degrade processing performance. While powdered and amorphous spherical fillers can enhance processing efficiency, they will weaken the material’s mechanical qualities.
(2) Particle size
Particle size range for filler that works best is 0.1–10 mm. The mechanical qualities, dimensional stability, surface gloss, and feel of the product all benefit from small particle sizes; but, too small of a particle size will make dispersing them problematic.
The type of plastic and the processing equipment’s dispersion capabilities should be taken into consideration when choosing the filler’s particle size during real production.
(3) Surface area of particles
The surface area of fillers is connected to several of their activities. The adsorption of surfactants, dispersants, surface modifiers, and polar polymers, as well as the occurrence of chemical reactions on the filler’s surface, are generally facilitated by an increase in the filler’s surface area.
(4) Equipment wear brought on by packing
Fillers will raise melt viscosity and hasten equipment wear. As a result, the formula’s lubricant and stabilizer dosages need to be appropriately increased.
PA mixture adjustment
Blending modification is the process of adding additional polymers to an already-generated polymer mechanically in order to modify its characteristics. It should be highlighted that the intended modification effect in blending modification can only be realized when an incompletely compatible multiphase system is established and the two polymers can be equally dispersed with each other.
1.PA combined with standard plastics
The barrier qualities of PE against solvents like oxygen and hydrocarbons can be strengthened by blending PA with PE. However, there is little compatibility between PA and PE because of their dissimilar chemical structures. As a result, the PE molecular chain needs to include amide groups or terminals that can interact with PA. To improve the interfacial contact between PE and PA, the amine group functions as a polar group.
Combining PP and PA can increase air tightness and colorability. The compatibility of various polymers should be taken into consideration while modifying a blend. It is typically necessary to include a third component that has strong compatibility with both polymers when combining two polymers that are not compatible. The third element is referred to as a compatibilizer.
Because of their incredibly poor compatibility, nylon-6 and polypropylene cannot be mixed evenly with just mechanical force. At this point, the chemical interaction between maleic anhydride and the amide group of nylon-6 will significantly increase the compatibility of nylon-6 and polypropylene if a little amount of polypropylene grafted with maleic anhydride is introduced.
2. Blending PPO and PA
PPO, also known as polyphenylene ether, is a superior thermoplastic engineering plastic with favorable thermodynamic characteristics. PPO is capable of continuous operation at -160–190°C. PPO also boasts outstanding mechanical, physical, and dimensional stability qualities. significant melt viscosity, low fluidity, challenging molding and processing, and significant energy consumption are some of its drawbacks. As a result, it restricts PPO’s actual use and advancement.
PPO must be altered in order to increase its functionality and broaden its application areas. For PPO, the most significant modification measure at the moment is blending modification.
PPO/PS and PPO/HIPS alloys have low thermal deformation temperatures and inadequate oil and solvent resistance, despite having high tensile strength, flexural strength, notched impact strength, and other great qualities. Consequently, the development of incompatible systems like PPO/PA (polyamide) and PPO/PBT (polybutylene terephthalate) is unavoidable. Enhancing the compatibility of polymers is crucial.
While PA has excellent mechanical properties, wear resistance, solvent resistance, and electrical properties, it has poor dimensional stability, hygroscopicity, and thermal deformation resistance under high load. Polyphenylene ether, on the other hand, has excellent heat resistance, mechanical properties, electrical properties, dimensional stability, and water resistance, but poor oil resistance and solvent resistance. As a result, an alloy created by mixing these two resins can compensate for each of their drawbacks, although PA and PPO compatibility Due to the weak qualities, compatibilizers are required in order to enhance the blend system’s performance.
3. Polyamide modification with an antibacterial mix
To create antibacterial modified nylon 6 (PA6) slices, mix nylon 6 (PA6) slices with a chitosan-silver/titanium dioxide composite antibacterial agent in a proportionate amount, melt and combine using a conical twin-screw extruder, extrude, cool with cooling water, granulate, and dry.
There is no visible agglomeration, good dispersion, uniform size, and high compatibility in the antibacterially modified PA6 chip resin matrix. The anticipated outcome of the antibacterial change has been attained. The antibacterial modified PA6 slices have a more stable structure, a higher initial decomposition temperature, and better thermal stability as a result of the doping impact of the composite antibacterial agent.
