Performance Issue with bulk Insert of Rows to Temp Table

I am trying to insert multiple rows to temp tables on postgreSQL database using psqlodbc lib (version 10.4). I am using bind variables to insert the rows to the table. When i gone through the logs i could see that it is getting inserted one at a time using the same plan instead of bulk insert of values. 

CREATE TEMPORARY TABLE  TEMP_uid_scratch2   ( auid VARCHAR(15) ) ;

Results shows linear increase in time as well

80 rows  - 16 ms

160 rows - 32 ms

32536 rows - 18 secs

I am using server side prepare by default. Is there any other way to improve this or any configurations setting to make it efficient to insert bulk rows instead of one row at a time?

Thanks,

Vikram Rakhe