One obvious way to increase strength is the addition of reinforcements, such as glass fibers. Please specify more closely the application you are interested in: product size, wall thickness, intended processing method (injection etc.), the temperature range you need for application, expected impact properties, chemical environment etc. These are the most basic criteria you have to consider when selecting a material. If the matrix material is decided, it is relatively easy to find a galss fiber reinforced version. Reinforcement does increase strength, but usually decreases elongation at break.

Thank You Gyorgy Banhegyi , I am interested in Solid polymer electrolytes for battery application of thickness varies around 150-200 micrometr with having high conductivity without sacrificing Mechanical Strength of SPEs. so I am interested to know ideal mechanical strength and conductivity for SPEs for practical application

thank you Pavel. but when fillers are doped in polymers litereature says mechanical strength increases .... this mean Fillers play role in Chemical Reaction of the Polymers?

The preparation conditions affect the mechanical strength as well. For example, if you prepare your polymer in an air-vaccumed environment, your polymer will have much less voids and therefore much more mechanical strength.

Thank you Pavel ... I went through my experimental results, according through your answer and correlated with my data... and now gaining the knowledge really what happens inside when particles are added into the polymer solution...