make very narrow welding zones as compared to other types of welding procedures according to the present invention the croconic acid derivative is preferably present admixed with the plastic material in certain applications it may however be advantageously to have the croconic acid derivative deposited on the surface between the parts to be joined by laser welding it is desirable to have the nir absorber evenly distributed in the plastic to ensure a smooth welding zone the even distribution may be achieved by preparing nir absorbers that are soluble in the type of plastic one wish to weld one strategy to achieve high solubility of organic absorbers in very non polar solvents and also to very non polar polymers such as polyethylene and polypropylene is to append long alkyl chains to the absorber several factors influence how weldable two plastics are one factor is the type of plastics examples of suitable plastic materials for the present invention includes abs acrylonitrile butadiene styrene copolymer asa acrylonitrile styrene acrylate copolymer mabs methyl methacrylate acrylonitrile butadiene styrene copolymer pa 6 polyamide 6 pa 6 6 polyamide 6 6 pa 12 polyamide 12 pbt polybutylene terephthalate pbt asa polybutylene terephthalate acrylonitrile styrene acrylate blends pc polycarbonate pc abs polycarbonate acrylonitrile butadiene styrene blends ldpe low density polyethylene hdpe high density polyethylene peek poly ether ketone pes polyethersulfone pet polyethylene terephthalate pmma poly methyl methacrylate pom polyoxy methylene pp.