Bubbles on the back side (gel side) of FRP products

The mold contact surface (front side) of FRP laminated products is smooth but bubbles appear on the back side. This defect is usually discovered after demolding or during cross-section inspection, mostly concentrated in thick-wall areas or at the end of resin flow. Internal defects reduce the mechanical strength and compactness of the product, and have a particularly serious impact on products with pressure-bearing and sealing requirements.

(1) Process factor: volatiles in resin gathering at the surface during free curing of the back side; this factor affects the '2079851475616104453 and final quality of the product. (2) Gas removal aspect: back side not compacted for venting; gas retention forms internal defects affecting product compactness. (3) Material aspect: volatile content or moisture in raw materials exceeding standard, vaporizing at molding temperature to form bubble sources. (4) Process aspect: air entrainment during filling or pouring, with insufficient venting/degassing measures. (5) Mold aspect: unreasonable cavity venting structure design, gas cannot be effectively discharged.

(1) Material selection: use peel ply or easy-tear cloth on the back side for compaction; establish material selection evaluation standards and determine the optimal solution through comparative tests. (2) Process enhancement: cure the product under pressure/vacuum; increase vacuum degree and ensure sufficient processing time, and proceed to the next process after confirming that bubbles are completely eliminated. (3) Formulation adjustment: reduce volatiles in resin., adjust gradually and verify the effect, ensuring that other performance indicators of the product are not affected. (4) Preventive measures: establish standardized degassing and casting operating procedures, regularly train operators, and check the first piece of each shift to confirm there are no bubble defects.

The essence of this problem is that gas was not effectively removed during the lamination '2079851475616104453, requiring coordinated solutions from three aspects: degassing process, casting method, and venting design.