preparation of rubber gypsum composite by using cold method moulding and radiation finishing process

Natural rubber latex (NRL) as a liquid rubber was mixed with anhydrous calcium sulphate (gypsum ) at room temperature using full hydrolyzed polyvinyl alcohol as a protective colloid for rubber part and cellulo sic stabilizer for gypsum part to stabilize and control the mixing process from the fast coagulation. the liquid mix ure was moulded in a 10 m3 cubic cavity to obtain rubber- gypsum blocks. the minimum amount of calcium sulphate which was required to induce moulding state of natural rubber latex was 3.97% of the total weight of formulation and 6.24% of rubber - gypsum total ratio. radiation finishing process was applied on the dried composite blocks for three different reasons. first was to sterilize the prepared mould, second was to activate the mould surface to be self adhesive product, the third was to obtain a soft rubber mould with 7% dioctyl phthalate as a plasticizer. the prepared rubber - gypsum moulds were passed through a serious of measurements such as setting time , weight loss, bulk density, abrasion surface ,hardness, scanning electron microscopy (sem), tensile strength, elongation at break, compression set and water absorption . the use of the prepared rubber gypsum moulds as wet moulding and dry articles via extrusion processes for auto motives and machines and also hygienic sterilized products as nontoxic rubber tools for kids and children