--- 物性 is defined as "property of matter" so I would surmise that 物性出し are the ingredients that bring out the "properties in the matter."

1) Moseying around I found "base material" as an alternative definition of 母材. It's in the below NEC Engineering Glossary Website
http://www.nec-eng.co.jp/pro/document/word/word/wrd_e_b.html
base material 基材, 母材

2) The below website describes what ingredients go into the manufacturing of rubber.
--- It has its core/base material followed by a series of additives that lend the rubber its particular qualities or properties, followed by the finishing additives.
--- From what I can gather, a large bulk of the ingredients are the property-giving/property-lending additives such as fillers, and plasticizers. The remaining additives are accelerators, activating agents, anti-degrading agents, other processing chemicals and pigments.

http://www.ndsseals.com/rubber-ingredients.html
“A rubber compound is obtained by mixing a base polymer or crude mixture with a series of additives. The choice of the base polymer and the additives is closely linked to the type of properties to be achieved.” The resulting product is a non vulcanized compound. The quantity of additives used varies for 20 to 130% as a percentage on the weight. The additives include fillers, plasticizers, etc.... with the last ingredients being separated by an extra space as activators, "pigments, etc.

Fillers
There are two types of fillers, reinforcing and non reinforcing fillers. Carbon black is commonly used as a reinforcing filler. This is also the reason why most rubbers are black. Calcium carbonate is an example of a non reinforcing filler.
Plasticizers
Besides fillers, plasticizers play the biggest quantitative role in building a rubber compound. The reasons for the use of plasticizers are:
Improvement of flow of the rubber during processing, improved filler dispersion, influence on the physical properties of the vulcanizate at low temperatures. Mineral oils and paraffins are widely used as a plasticizer.

Vulcanization chemicals
Vulcanization is the conversion of rubber molecules into a network by formation of crosslinks. Vulcanizing agents are necessary for the crosslink formation. These vulcanizing agents are mostly sulphur or peroxide and sometimes other special vulcanizing agents or high energy radiation. Since vulcanization is the process of converting the gum-elastic raw material into the rubber-elastic end product, the ultimate properties like hardness and elasticity depend on the course of the vulcanization.

Accelerators
Accelerating agents increase the rate of the crosslinking reaction and lower the sulpher content necessary to achieve optimum vulcanizate properties.




Activators
Like zinc-oxide and stearic acid. They activate the vulcanisation process and help the accelerators to achieve their full potential.

Anti degrading agents
These agents increase the resistance to attacks of ozone, UV light and oxygen.

Process aids
Chemicals which improve the processability.

Pigments
Organic and inorganic pigments are used to colour rubber compounds. The colour pigments are also considered inactive fillers. Only silica’s have a reinforcing effect. Silicone can be coloured easily without loss of properties.


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Note added at 11 hrs (2011-01-11 03:18:56 GMT)
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Also, under "Vulcanization chemicals" it says "the ultimate properties like hardness and elasticity depend on the course of the vulcanization." - So, I would think that this is another one of those property-lending additives....I believe that the "other compounds" or "other additives" are pigments and those chemicals that help maintain the the rubber's properties.