The newest hypothesis, the Mixed Crystal Hypothesis according to Scholten , confines itself to the description of the acting mechanisms in a PE-X weld (Fig.
The Nexus-Hypothesis by Bonten  adds to the Mixed Crystal Hypothesis: Also "normal" thermoplastics, without crosslinkages, allow force transmission by mixed recrystallization of the molecular chains of both components in the weld joint after a short time.
However, their mixed crystals
have not been investigated.
NIST scientists are attempting to nullify the birefringence by using mixed crystals
of calcium fluoride and barium fluoride, a substance that exhibits opposite birefringence behavior.
The basic structure of the lamellar mixed crystals consists of apatitic lamellas sandwiching an OCP lamella (20).
Moriwaki, Growth and structure of lamellar mixed crystals of octacalcium phosphate and apatite in a model system of enamel formation, J.
NIST researchers are pursuing potential solutions to the problem involving mixed crystals
to compensate for the birefringence effect.