Process for the preparation of a bonded structure, a bonded structure and use of said bonded structure for preparing an automotive part

A process for the preparation of a bonded structure comprising at least a first plastic part having a first bonding surface, said process comprising the steps of:

• a) treating at least part of a first bonding surface of said first plastic part with a flame of a propane gas, wherein, during treatment with a flame of the propane gas, a flame is produced by burning a mixture consisting of air and the propane gas, and optionally one or more of methane, ethane, butane, pentane, and hexane, wherein the gas-to-air ratio is chosen such that the propane gas to oxygen volume ratio is from 1:4.50 to less than 1:5.01 to obtain a first plastic part having a flame-treated first bonding surface,
• wherein the first plastic part comprises polypropylene and 0 to 5% of an additive wherein the polypropylene is not blended with another polymer, and
• b1) providing a second plastic part, wherein the second plastic part has a second bonding surface and
• c1) contacting said first and second bonding surfaces with a bonding agent together by contacting at least part of the flame-treated first bonding surface and at least part of said second bonding surface with said bonding agent.