Blow-molded panel and manufacturing method for blow-molded panel

A method of manufacturing a blow-molded panel, comprising steps of:

• (a) heating a first polymer and a second polymer until said first and second polymers are in a fluid state;
• (b) extruding said first and second polymers to form first and second polymer layers respectively;
• (c) fusing said first and second polymer layers with each other in an overlapping manner to form a fused body;
• (c) blow molding said fused body to form first and second panel members which are spaced apart with each other to form a cavity between said first and second panel members, wherein each of said first and second panel members is constructed by said first and second polymer layers;
• (d) forming a plurality of supporting structures by concurrently stretching and recessing a plurality of different portions of said first polymer layer and a plurality of different portions of said second polymer layer of said second panel member into said cavity for ensuring no additional material of said second panel member being added to form said supporting structures, wherein said supporting structures are extended to bias against said first panel member so as to support said first panel member;
• (e) heating a third polymer until said third polymer is in a fluid state;
• (f) extruding said third polymer to form a third polymer layer, wherein said first, second and third polymers are extruded to form said first, second and third polymer layers at the same time;
• and
• (g) fusing said first, second and third polymer layers with each other in an overlapping manner to form said fused body at a position that said second polymer layer is sandwiched between said first polymer layer and said third polymer layer, wherein each of said first and second panel members is constructed by said first, second and third polymer layers, wherein a plurality of different portions of said third polymer layer of said second panel member are concurrently stretched and recessed along with said portions of said first polymer layer and said portions of said second polymer layer of said second panel member into said cavity to form said supporting structures respectively, such that each of said supporting structures is constructed by said first, second and third polymer layers, wherein said fused body is blow-molded to form said first and second panel members at a position that said cavity is formed between said third polymer layer of said first panel member and said third polymer layer of said second panel member, wherein said first polymer layer is made of high density polyethylene, said third polymer layer is made of a mixture of high density polyethylene and calcium carbonate or a mixture of high density polyethylene and glass fiber, and said second polymer layer is made of a mixture of metallocene polyethylene and calcium carbonate or a mixture of metallocene polyethylene plus glass fiber.