How can i divide mesh into single polygons(tris) and then just make them fly randomly out(making like breakup effect)

Use this script, it's one I found online and enhanced it to support different kinds of renderers. It's be wise to implement object pooling if it's used regularly during game play to avoid memory leaks.

Use it with

 StartCoroutine(objectToEplode.GetComponent<TriangleExplosion>().SplitMesh(true));

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 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 
 public class TriangleExplosion : MonoBehaviour {
 
     public IEnumerator SplitMesh (bool destroy)    {
 
         if(GetComponent<MeshFilter>() == null || GetComponent<SkinnedMeshRenderer>() == null) {
             yield return null;
         }
 
         if(GetComponent<Collider>()) {
             GetComponent<Collider>().enabled = false;
         }
 
         Mesh M = new Mesh();
         if(GetComponent<MeshFilter>()) {
             M = GetComponent<MeshFilter>().mesh;
         }
         else if(GetComponent<SkinnedMeshRenderer>()) {
             M = GetComponent<SkinnedMeshRenderer>().sharedMesh;
         }
 
         Material[] materials = new Material[0];
         if(GetComponent<MeshRenderer>()) {
             materials = GetComponent<MeshRenderer>().materials;
         }
         else if(GetComponent<SkinnedMeshRenderer>()) {
             materials = GetComponent<SkinnedMeshRenderer>().materials;
         }
 
         Vector3[] verts = M.vertices;
         Vector3[] normals = M.normals;
         Vector2[] uvs = M.uv;
         for (int submesh = 0; submesh < M.subMeshCount; submesh++) {
 
             int[] indices = M.GetTriangles(submesh);
 
             for (int i = 0; i < indices.Length; i += 3)    {
                 Vector3[] newVerts = new Vector3[3];
                 Vector3[] newNormals = new Vector3[3];
                 Vector2[] newUvs = new Vector2[3];
                 for (int n = 0; n < 3; n++)    {
                     int index = indices[i + n];
                     newVerts[n] = verts[index];
                     newUvs[n] = uvs[index];
                     newNormals[n] = normals[index];
                 }
 
                 Mesh mesh = new Mesh();
                 mesh.vertices = newVerts;
                 mesh.normals = newNormals;
                 mesh.uv = newUvs;
                 
                 mesh.triangles = new int[] { 0, 1, 2, 2, 1, 0 };
 
                 GameObject GO = new GameObject("Triangle " + (i / 3));
                 //GO.layer = LayerMask.NameToLayer("Particle");
                 GO.transform.position = transform.position;
                 GO.transform.rotation = transform.rotation;
                 GO.AddComponent<MeshRenderer>().material = materials[submesh];
                 GO.AddComponent<MeshFilter>().mesh = mesh;
                 GO.AddComponent<BoxCollider>();
                 Vector3 explosionPos = new Vector3(transform.position.x + Random.Range(-0.5f, 0.5f), transform.position.y + Random.Range(0f, 0.5f), transform.position.z + Random.Range(-0.5f, 0.5f));
                 GO.AddComponent<Rigidbody>().AddExplosionForce(Random.Range(300,500), explosionPos, 5);
                 Destroy(GO, 5 + Random.Range(0.0f, 5.0f));
             }
         }
 
         GetComponent<Renderer>().enabled = false;
         
         yield return new WaitForSeconds(1.0f);
         if(destroy == true) {
             Destroy(gameObject);
         }
 
     }
 
 
 }