friction not working correctly in my 2d game - unity

I am developing a 2d game in unity, and I am trying to add friction to slow the player down when he is on the ground. I launch the player into the air with the rigidbody's add force. I have heard of physics materials, and am currently trying to use them. I am using the 2d version of them, I made one material which had high friction. I add the material to the floor, and then I play the game, and my character is still sliding on the floor. I thought the problem might be with the player not having a physics material, so I added one. It still didn't work.

• I tried doing different combinations with the different materials.

• I tried attaching a rigidbody, but kinematic to the floor.

• I tried looking it up, and couldn't find an answer.

Here is the code that moves the player:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Player : MonoBehaviour
{
    public bool isGrounded = true;
    public float fireForce;
    Rigidbody2D rb;

    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
        camera = camObj.GetComponent<Camera>();
    }
    void Update()
    {
        RotateToPoint();
        Fire();
    }
    void OnCollisionEnter2D(Collision2D obj)
    {
        if (obj.gameObject.tag == "surface")
        {
            isGrounded = true;
        }
    }
    void OnCollisionExit2D(Collision2D obj)
    {
        if (obj.gameObject.tag == "surface")
        {
            isGrounded = false;
        }
    }
    void Fire()
    {
        if (Input.GetKeyDown(KeyCode.Mouse0) && isGrounded)
        {
            rb.AddForce(transform.up * fireForce, ForceMode2D.Impulse);
        }
    }
}

I do not know if I am approaching the problem correctly. If I am not, does anyone know how to avoid slippery game objects. Any help would be appreciated.