The material selection for lightweight PVC baseball needs to take into account both material properties and processing techniques. The following is a specific analysis:
Basic PVC material characteristics
PVC (polyvinyl chloride), as a non-crystalline thermoplastic, features flame retardancy, strong chemical stability, and resistance to acid and alkali corrosion. Its specific gravity is 1.45-1.5 grams per cubic centimeter, the molding shrinkage rate is 0.6-1.5%, the working temperature range is -15℃ to 60℃, and it features high strength, high rigidity and high hardness. However, pure PVC has problems such as low softening point and poor fluidity, and the goal of lightweight needs to be achieved through modification.
Lightweight modification direction
Blending modification
By adding low-density fillers (such as hollow glass microspheres, fumed silica) or elastomers (such as CPE, ACR), the density can be reduced while maintaining the rigidity of the material. For instance, adding 10%-20% hollow glass microspheres can reduce the density by 15%-20% while enhancing the impact resistance.
Foaming process
Microporous structures are formed in the PVC matrix by using chemical foaming agents (such as AC foaming agents) or physical foaming technologies (such as supercritical CO₂). When the foaming ratio is controlled at 1.5 to 3 times, the weight can be significantly reduced (the density drops to 0.6 to 1.0 grams per cubic centimeter), while maintaining good resilience and buffering performance.
Plasticizer optimization
Low-volatility and highly compatible plasticizers (such as DOP and DOTP) are selected to enhance flexibility while reducing material usage. The addition amount of plasticizer should be controlled within the range of 10% to 30% to avoid excessive softening that leads to a decrease in strength.
Processing technology adaptation
Mold design
Adopting a thin-walled design, the wall thickness of the baseball is controlled within the range of 1.5-2.5 millimeters, combined with a streamlined structure to reduce the amount of materials used. The mold needs to be equipped with reasonable exhaust grooves to avoid the formation of air hole defects during the foaming process.
Molding temperature control
The molding temperature is set at 160-180℃ to ensure the full plasticization of PVC while avoiding thermal decomposition. For the foaming process, it is necessary to precisely control the injection pressure and holding time to ensure the uniform distribution of cell structures.
Post-treatment process:
Internal stress is eliminated and dimensional stability is improved through heat setting treatment. For products with high surface hardness requirements, UV-cured coatings can be used to enhance wear resistance.
Key points of performance balance
Mechanical property guarantee:
Reinforcement is achieved through fiber reinforcement (such as glass fiber, carbon fiber) or nano-fillers (such as nano-calcium carbonate) to ensure that the tensile strength is no less than 30MPa and the impact strength is ≥5kJ/m², meeting the mechanical requirements for baseball hitting.
Balance between lightweight and durability
While reducing the density by 20% to 30%, the service life of traditional PVC products can be extended to over 80% through cross-linking modification or the addition of anti-aging agents (such as hindered amine light stabilizers).
Cost and process feasibility
The cost increase of the blending modification and foaming processes should be controlled within 15% to ensure that the products are competitive in the market. The use of expensive special additives or complex multi-step molding processes should be avoided.