Preparation Of Ammonia-Free Phenolic Molding Compounds

According to the requirements of ammonia-free phenolic molding compounds, the curing agent, phenolic resins, various packing ratio and composition are studied. The final products have been characterized.Hexamethylenetetramine is used for the curing agent of the phenolic molding compounds, but it is the main source of the ammonia in the phenolic molding compounds. The least addition amount of the hexamethylenetetramine was researched. If ammonia-free phenolic molding compounds contented the requirements of ammonia amount no more than 0.01%, the addition amount of the hexamethylenetetramine should be no more than 2%.For the basic resins of ammonia-free phenolic molding compounds, there are thermoplastic resin, liquid thermosetting resin and solid thermosetting resin. The amount of liquid thermosetting resin should be no more than 2% for the production. The greater proportion of thermosetting resin in the mixture system is, the faster the curing molding will be, and the worse the stability of the barrel will be. The proportion of the resins should be decided by the application of the production.The bind force has been increased after the filler and glass fiber have been pretreated with the silane coupling agent. It can significantly improve the mechanical strength of phenolic molding compounds, water anti-absorption, electrical properties and heat distortion temperature, but the appearances of thermal stability have a negative impact. Increasing the glass fiber additive quantity (≤50%) will improve the mechanical strength of ammonia-free phenolic molding compounds. The greater the amount of glass fiber is, the better the mechanical properties of materials will be.As the flame resistance of phenolic resin was relatively good, adding a small amount of flame retardant can achieve the desired flame retardance. The flame retardance of the mold compounds can reach 0.45mm in UL94V-0 level after adding 1.5% coated red phosphorus, or 0.5% MPP or MCA when the coated red phosphorus addition is 1%. Increasing the ratio of thermosetting resin and the amount of curing accelerator can improve the thermal rigidity and thermosetting. They will improve the solder resistance of ammonia-free phenolic molding compounds. Magnesium oxide and calcium hydroxide mixed system is better take into account the material properties and mechanical properties of solder resistance.