Some help with ultrasonic welding of plastics - suitability guide
The process of ultrasonic welding of plastics is achieved by applying a vibrating metal tool (horn) at 90° to the stationery plastic parts which then vibrate. When combined with pressure, friction produces heat & melts the parts at the horn contact point. Once cooled down a solid homogeneous weld between the 2 parts is created.

To give you help with ultrasonic welding of plastics for your application, this ultrasonic welding guide lists the most common unfilled grades of plastic available & their suitability for each style of ultrasonic welding  As a rule, stiffer materials are easier to weld & those with higher melt temperatures need more energy. To weld different materials, they need similar molecular structures - crystalline ones are only weldable to themselves

MATERIAL TYPES, ABBREVIATIONS & STRUCTURES
CLOSE
WELDING
DISTANT
WELDING
INSERTING
SPOT
WELDING
STAKING
Acetal Co/Homopolymer
POM
C
Good
Fair
Good
Fair
Fair
Acrylic
PMMA
A
Good
Fair
Good
Good
Fair
Acrylic - Impact Modified
PMMA
A
Fair
Poor
Poor
Fair
Fair
Acrylonitrile Butadiene Styrene
ABS
A
V.Good
Good
V.Good
V.Good
V.Good
Cellulose Acetate...
CA/B/P
A
Poor
NS
V.Good
Poor
Good
Polyamide 6 & 66 (Nylon)
PA6 & 66
C
Good
Fair
Good
Fair
Fair
Polycarbonate
PC
A
Good
Fair
Good
Good
Fair
Polycarbonate/Abs
PC/ABS
A
Good
Fair
Good
Good
Good
Polyester - Thermoplastic
PBT/PET
C
Good
Fair
Good
Fair
Fair
Polyethylene - Low/High Density
LD/HDPE
C
Poor
Poor
Good
Good
Fair
Polyphenylene Oxide
PPO
A
V.Good
Good
V.Good
V.Good
V.Good
Polyphenylene Sulphide
PPS
C
Good
Fair
Good
Fair
Poor
Polypropylene
PP
C
Fair-Poor
Poor
Good
V.Good
V.Good
Polystyrene - General Purpose
GPPS
A
V.Good
V.Good
Good
Fair
Fair
Polystyrene - High Impact
HIPS
A
Good
Poor
Good
Fair
Fair
Polyvinyl Chloride - Flexible
PVC
A
Poor
NS
NS
Poor
NS
Styrene Acrylonitrile...
SAN/ASA
A
V.Good
V.Good
Good
Fair
Fair

A (Amorphous) = polymers with a random molecular chain structure. This & their wide softening temperature range enables them to soften gradually without solidifying quickly, thus making ultrasonic welding them easy.
C (Crystalline) = polymers with an orderly molecular chain structure. This & their sharp melting & solidification points makes them absorb vibrations when solid, thus making ultrasonic welding them more difficult.
Close Welding = ultrasonic welding where the horn is applied close to (<6.35mm) the assembly joint - good for welding materials whose low modulus of rigidity dampens vibrations a short distance away from the horn.
Distant Welding = ultrasonic welding where the horn is applied away from (>6.35mm) the assembly joint - good for welding materials whose high modulus of elasticity propagates vibrations without dampening them.
Inserting = ultrasonic embedding of metal components like inserts into preformed holes in the moulding - provides high strength & speed, no stress build up & reduced moulding cycles.
Spot Welding = ultrasonic assembly of parts without premade holes or energy directors - good for large parts
Staking = melting and reforming a post on the moulding to mechanically lock dissimilar materials in place - provides short cycles, good appearance & tight assemblies

For more help with plastics for your application view our ultrasonic welding diagrams or material selection
guides