All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
We have already issued Fatwa 83760 about the ruling of washing pure clothes with impure clothes in the washing machine, so please refer to it.
As regards your inquiry as to how many times the clothes should be washed, the answer is that we mentioned in the above Fatwa that if the water of the washing machine is a small quantity, and impure clothes were put in it, then this renders the water impure.
Since the clothes are impure, when they are put in a small quantity of water they render this water impure. So you should first remove the impurity from the clothes outside the washing machine and then there is no harm in washing them in the washing machine.
The jurists differed in relation to the number of times the clothes should be washed so that the impurity would be removed. Some of them are of the view that they should be washed seven times, and this is the view of the Hanbali school. Some others are of the view that they should be washed three times.
However, the correct opinion is that it is not a condition to wash the clothes a number of times; if the impurity is removed by even one washing, then that is sufficient. But if the impurity cannot be removed unless the clothes are washed two or three times, then it would be an obligation to wash them that many times so that the impurity will be removed. What is important is the removal of impurity and not the number of times the clothes are washed. The evidence for this is that Imaam Al-Bukhari reported that Asmaa' said: "A woman came to the Prophet and asked: "What should we do when our dress is stained by [the blood of our] menses? He replied: "She should rub it [rub the place of impurity] and rinse it with water and then pray in it." The Prophet did not mention any number of times that she should wash her clothes stained with the blood of her menses. If there is no smell or colour of the impurity, then it would be sufficient to just sprinkle water on it once.
As regards whether or not it is possible to purify the plastic utensils if they are touched with impurity, the jurists stated that if the impurity penetrates the crockery [like in the case of this impurity being a liquid that can infiltrate into the earthen vessels] then the utensil becomes impure and it is not possible to purify it. This is what Khaleel [from the Maaliki School] stated when mentioning the items that cannot be purified and he mentioned the earthenware that became impure by an impurity that easily penetrates the utensil, like intoxicants. However, if the impurity does not penetrate the utensil or that the impurity itself is not of the kind that can infiltrate into the utensil, then it can be purified by washing it.
Therefore, we say that it is known that liquids cannot penetrate plastic utensils, so it is very easy to purify them.
Allaah Knows best.