The 18-year-old from Vancouver smashed his racket in frustration after his opponent claimed the title on a first match point. Peliwo had put the Belgian under pressure with three break points in the final game, but Coppejans managed the save them all — the third with an ace.
Second after sending a return long over the baseline, Peliwo reduced his racquet to graphite shards and then kicked his kit bag for good measure after grumpily offering a quick hand to the chair umpire.
"If I hadn't let my anger out there would have been something seriously wrong with me," said Peliwo. "This was the most disappointing day of my life.
"I'm not proud of breaking a racquet, but it happens sometimes. I got angry but I wasn't a sore loser. I told him he played a good match.
"It wasn't like I was an angry little kid on court, it was jut one moment. "I did find it impossible to smile for the (post-match) picture, though."
He also lost the Australian Open junior final five months ago but had vowed to make amends in Paris.
Peliwo finished with four aces and unable to convert on any of his four break chances. He lost his own serve three times on a frustrating overcast day.
Coppejans won the first set in 27 minutes with two breaks and went up another break in the third game of the second set.
Peliwo steadied until the frustrating final game which sealed his fate.
"I'm extremely disappointed, this was much worse than in Australia," said Peliwo. "There I put up a fight and played decent there. Here I was just really bad.
"My opponent played better than I've ever seen him play. I can't make excuses, he was better than me."