I tried to heat two rice bags at the same time once and they melted together. I didn't think about the fact that they had used synthetic fabric! I'm so used to

I tried to heat two rice bags at the same time once and they melted together. I didn't think about the fact that they had used synthetic fabric! I'm so used to doubling the cooking time because our microwave is only 600 watts (compared to the usual 1000-1200 watts).