There seems to be a character limit for iOS push notifications based on the type of notification. These values can be seen in a similar Stackoverflow question:
What is the maximum length of a Push Notification alert text?
Alerts: Prior to iOS 7 the alerts display limit was 107 characters. Bigger messages were truncated and you would get a "..."
at the end of the displayed message. With iOS 7 the limit seems to be
increased to 235 characters. If you go over 8 lines your message will
also get truncated.
Banners: Banners get truncated around 62 characters or 2 lines.
Notification Center: The messages in notification center get truncated around 110 characters or 4 lines.
Lock Screen: Same as notification center.
I would also recommend looking further into the Push Notification documentation provided by Apple:
Apple Push Notification Service