FDM Part IV Styrenics Family

FDM Polymers — A Technical Reference ›

Part IV — Styrenics Family

The styren­ics: ABS, ASA, and HIPS - the orig­i­nal en­gi­neer­ing-ad­ja­cent com­mod­i­ty fil­a­ments, de­fined by styrene con­tent, en­clo­sure needs, and sol­vent-smooth­ing be­hav­ior.

10. Styrenics: ABS, ASA, HIPS

The styrenic fam­i­ly is built on poly­styrene chem­istry with var­i­ous copoly­mer ad­di­tions for tough­ness, weather­abil­i­ty, or sol­u­bil­i­ty. Its three FDM-rel­e­vant mem­bers — ABS, ASA, and HIPS — share a char­ac­ter­is­tic warp­ing be­hav­ior that de­fines how they are print­ed, but their solvent workflows differ: ABS and ASA are normally smoothed with acetone, while HIPS is primarily dissolved or finished with limonene and is easily over-etched by acetone. The fam­i­ly has been par­tial­ly dis­placed from desk­top FDM by PCTG and the poly­car­bon­ate blends for gen­er­al en­gi­neer­ing use, but it re­mains the most cost-ef­fec­tive en­closed-print ma­te­ri­al, the canon­i­cal choice for out­door ser­vice in the case of ASA, and the only wide­ly prac­ti­cal sol­u­ble-bath sup­port for the fam­i­ly in the case of HIPS. This chap­ter treats the shared chem­istry first, then each ma­te­ri­al in turn, then the process, post-pro­cess­ing, and se­lec­tion ques­tions com­mon to all three.

10.1 Styrenic chemistry: the shared backbone

All three ma­te­ri­als are amor­phous poly­mers built on a poly­styrene back­bone. Poly­styrene it­self is rigid, glossy, easy to process, and brit­tle; the styrenic en­gi­neer­ing fil­a­ments are all strate­gies for keep­ing the pro­cess­abil­i­ty and gloss while de­feat­ing the brit­tle­ness. Be­cause the back­bone is amor­phous, none of the three has a true melt­ing point — they soft­en pro­gres­sive­ly above a glass tran­si­tion near 100 °C rather than melt­ing sharply — and all three can be solvent-finished, but not with the same solvent: ABS and ASA are acetone-vapor materials, while HIPS is a limonene-soluble polystyrene-family support and finishing material.

ABS (acry­loni­trile-bu­ta­di­ene-styrene) is a ter­poly­mer: acry­loni­trile con­trib­utes rigid­i­ty and chem­i­cal re­sis­tance, bu­ta­di­ene con­trib­utes im­pact tough­ness as a dis­crete dis­persed rub­ber phase, and styrene con­trib­utes pro­cess­abil­i­ty and sur­face gloss. ASA (acrylic-styrene-acry­loni­trile) re­places ABS's bu­ta­di­ene with an acry­late elas­tomer. That sin­gle sub­sti­tu­tion is the whole point of ASA: bu­ta­di­ene's car­bon–car­bon dou­ble bonds are the site of UV photo-ox­i­da­tion, so an ABS part chalks, yel­lows, and em­brit­tles with­in months of out­door ex­po­sure, where­as the sat­u­rat­ed acry­late rub­ber in ASA has no such dou­ble bonds and sur­vives years of UV. HIPS (high-im­pact poly­styrene) is the sim­plest of the three: poly­styrene im­pact-mod­i­fied with a dis­crete polybu­ta­di­ene phase, with no acry­loni­trile. It is less rigid and less chem­i­cal­ly re­sis­tant than ABS, but its poly­styrene base makes it sol­u­ble in limonene — the prop­er­ty that gives HIPS its main role as a sol­u­ble sup­port ma­te­ri­al.

The shared amor­phous back­bone also ex­plains the fam­i­ly's defin­ing print dif­fi­cul­ty. An amor­phous poly­mer with a glass tran­si­tion near 100 °C con­tracts sub­stan­tial­ly as it cools from melt to room tem­per­a­ture, and be­cause the con­trac­tion is con­tin­u­ous rather than re­leased at a sharp crys­tal­liza­tion point, a styrenic part builds in­ter­nal stress layer by layer as it prints. That stress ex­press­es it­self as warp­ing and as in­ter­lay­er crack­ing — the larg­er the part and the cool­er its sur­round­ings, the worse both be­come. The en­tire styrenic print process is or­ga­nized around man­ag­ing that stress.

10.2 ABS

ABS is the orig­i­nal en­gi­neer­ing fil­a­ment and re­mains the ref­er­ence against which the fam­i­ly is judged. Its glass tran­si­tion near 105 °C, ten­sile strength of rough­ly 30–45 MPa, mod­u­lus near 2 GPa, and elon­ga­tion of 10–40 % de­scribe a stiff, mod­er­ate­ly tough ma­te­ri­al with us­able heat re­sis­tance well above PLA or PETG. Its head­line notched-Izod im­pact of rough­ly 15–25 kJ/m² re­flects the bu­ta­di­ene rub­ber phase doing its job.

The cost of that prop­er­ty set is print­abil­i­ty. ABS shrinks roughly 0.4–0.8 % linearly on cooling — modest, but accumulated layer by layer — and on parts larger than about 100 mm in any dimension the resulting warp is severe without an enclosure. The prac­ti­cal con­se­quence is that ABS is an en­closed-print­er ma­te­ri­al: a pas­sive en­clo­sure hold­ing the cham­ber at 40–50 °C is the re­al­is­tic min­i­mum, and prints will still lift at the cor­ners with­out good first-layer ad­he­sion and a brim. ABS also emits styrene and fine par­tic­u­late dur­ing print­ing; ven­ti­la­tion or fil­tra­tion is a mean­ing­ful con­sid­er­a­tion

rather than an op­tion­al one, and is treat­ed in the emis­sions ma­te­ri­al of Chap­ter 5. Where ABS earns its place is the com­bi­na­tion of low cost, ace­tone vapor smooth­ing, and mod­er­ate heat re­sis­tance — no other fil­a­ment fam­i­ly de­liv­ers all three at ABS's price.

10.3 ASA

ASA has a glass tran­si­tion near 100 °C and ten­sile and stiff­ness fig­ures close to ABS; me­chan­i­cal­ly the two are near-equiv­a­lent. The dif­fer­ence that mat­ters is en­vi­ron­men­tal. ASA's sat­u­rat­ed acry­late rub­ber phase gives it a large UV-sta­bil­i­ty ad­van­tage — out­door ser­vice life mea­sured in years rather than the months an ABS part lasts be­fore it chalks and em­brit­tles — which makes ASA the canon­i­cal en­gi­neer­ing fil­a­ment for parts that live out­doors. ASA prints slight­ly hot­ter than ABS, typ­i­cal­ly 250–270 °C at the noz­zle with a 95–110 °C bed and an en­closed cham­ber, and it re­sponds to ace­tone smooth­ing in the same way ABS does.

The fig­ures below are the au­thor's own cal­i­bra­tion val­ues for Prusa­ment ASA on a Core One with a 0.4 mm PCD (E3D Di­a­mond­back) noz­zle. The cal­i­bra­tion was in progress at the time of com­pi­la­tion: the noz­zle-tem­per­a­ture, vol­u­met­ric-flow, and ex­tru­sion-mul­ti­pli­er val­ues are set­tled, Z-shrink­age com­pen­sa­tion was in­ten­tion­al­ly skipped, and pres­sure-ad­vance and XY-shrink­age cal­i­bra­tion were still pend­ing. They are of­fered as a con­crete, re­pro­ducible start­ing point for one spe­cif­ic fil­a­ment-and-ma­chine com­bi­na­tion, not a uni­ver­sal ASA spec­i­fi­ca­tion — Ap­pen­dix B car­ries the full worked ex­am­ple.

Parameter	Prusament ASA (calibrated)	Notes
Nozzle temperature	260 °C	settled; within the 250–270 °C ASA range
Max volumetric flow	9.5 mm3/s	ceiling from the volumetric-flow calibration step
Extrusion multiplier	1.03	calibrated by single-wall measurement
Z-shrinkage compensation	intentionally skipped	not pursued for this profile
Pressure advance	calibration pending	to be tuned and stored in the filament profile
XY-shrinkage compensation	calibration pending	to be measured on the standard test artifact

_{Table 10.1 — In-progress cal­i­bra­tion pro­file for Prusa­ment ASA (Core One, 0.4 mm PCD noz­zle). The set­tled val­ues fol­low the stan­dard cal­i­bra­tion work­flow; the pend­ing rows are noted hon­est­ly rather than filled with datasheet fig­ures. Treat this as a worked ex­am­ple of the cal­i­bra­tion method ap­plied to one ASA spool, not a por­ta­ble spec­i­fi­ca­tion.}

10.4 HIPS

HIPS has a glass tran­si­tion near 90–100 °C, ten­sile strength around 34 MPa, and mod­u­lus near 1.9 GPa — soft­er and less rigid than ABS, and with­out ABS's acry­loni­trile-de­rived chem­i­cal re­sis­tance. As a build ma­te­ri­al it is used for lighter-weight cos­met­ic parts, but this is a minor role and HIPS as a stand­alone model ma­te­ri­al is un­com­mon. Its more im­por­tant use is as a sol­u­ble sup­port: HIPS dis­solves in limonene while ABS and ASA do not, so a HIPS sup­port struc­ture can be re­moved from an ABS or ASA print by a limonene bath that leaves the model un­touched. HIPS prints at rough­ly 230–250 °C noz­zle and 100–110 °C bed, with the same en­clo­sure and warp con­sid­er­a­tions as the rest of the fam­i­ly.

Two cau­tions apply specif­i­cal­ly to HIPS. Limonene is a skin-sen­si­tiz­er and the bath process needs ap­pro­pri­ate han­dling and ven­ti­la­tion. And HIPS is more ag­gres­sive­ly at­tacked by ace­tone than ABS is — limonene smooth­ing works as a fin­ish­ing tech­nique for HIPS, but ace­tone, which smooths ABS clean­ly, will

over-etch a HIPS sur­face.

10.5 Property envelope

The three ma­te­ri­als are close enough me­chan­i­cal­ly that a side-by-side com­par­i­son is the clear­est way to see where they dif­fer. The fig­ures are rep­re­sen­ta­tive fil­a­ment-form ranges; as with every poly­mer in this vol­ume, brand-to-brand vari­a­tion is real and a spe­cif­ic spool should be cal­i­brat­ed rather than as­sumed from the table.

Property	ABS	ASA	HIPS
Glass transition (Tg)	~105 °C	~100 °C	~90–100 °C
Tensile strength	30–45 MPa	similar to ABS	~34 MPa
Modulus	~2 GPa	similar to ABS	~1.9 GPa
Elongation at break	10–40 %	similar to ABS	lower than ABS
Notched Izod impact	15–25 kJ/m2	similar to ABS	moderate
UV stability	poor (months outdoors)	excellent (years outdoors)	poor
Chemical resistance	moderate	moderate	lower (no acrylonitrile)
Solvent smoothing	acetone	acetone	limonene; acetone only with caution because it over-etches
Primary role	cost-driven engineering parts	outdoor service parts	soluble support

_{Table 10.2 — Styrenic prop­er­ty en­ve­lope. ABS and ASA are me­chan­i­cal­ly near-equiv­a­lent; the col­umns that ac­tu­al­ly sep­a­rate the fam­i­ly are UV sta­bil­i­ty and the choice of smooth­ing sol­vent. HIPS trades rigid­i­ty and chem­i­cal re­sis­tance for limonene sol­u­bil­i­ty, which is what makes it use­ful as a sup­port.}

10.6 Print process and calibration

The styrenic print process is, in essence, stress man­age­ment. The con­sol­i­dat­ed pa­ram­e­ters below are start­ing points; the rea­son­ing be­hind them is con­sis­tent across the fam­i­ly. Bed tem­per­a­ture is kept high to hold the first lay­ers above the point where they would begin to con­tract and lift. The cham­ber is en­closed so that the whole part cools slow­ly and even­ly, which lim­its the layer-to-layer stress that drives both warp­ing and in­ter­lay­er crack­ing. Part cool­ing is used spar­ing­ly or not at all — ag­gres­sive fan cool­ing freezes each layer be­fore it has bond­ed fully to the one below, weak­en­ing the part and wors­en­ing warp. A brim or raft is rou­tine on any­thing large. PEI grips all three ma­te­ri­als strong­ly, so ad­he­sion is rarely the fail­ure mode; warp-driv­en cor­ner lift is.

Parameter	ABS	ASA	HIPS
Nozzle temperature	240–260 °C	250–270 °C	230–250 °C
Bed temperature	95–110 °C	95–110 °C	100–110 °C
Chamber	enclosed, passive 40–50 °C	enclosed	enclosed
Part cooling	minimal to none	minimal to none	minimal to none
Bed surface	PEI; brim for large parts	PEI; brim for large parts	PEI
Shrinkage	~0.4–0.8 % (linear, bulk-material basis; converged in-print XY compensation runs lower, ~0.35–0.5 % — see §23.6)	similar to ABS	similar to ABS

_{Table 10.3 — Con­sol­i­dat­ed styrenic print pa­ram­e­ters. The ranges over­lap heav­i­ly be­cause the three ma­te­ri­als share a back­bone and a fail­ure mode; an en­clo­sure and re­strained part cool­ing mat­ter more than the exact tem­per­a­ture with­in these bands. Cal­i­brate the spe­cif­ic spool — the worked ASA ex­am­ple in Table 10.1 shows the method.}

10.7 Post-processing: solvent vapor smoothing

Sol­vent vapor smooth­ing is the styrenic fam­i­ly's sig­na­ture post-process and a gen­uine ad­van­tage over most other fil­a­ment fam­i­lies. Sus­pend­ing a part in the sol­vent vapor briefly liq­ue­fies the out­er­most sur­face layer; sur­face ten­sion then pulls that layer flat, eras­ing layer lines and pro­duc­ing a glossy, near-in­jec­tion-mould­ed fin­ish. The process also clos­es sur­face poros­i­ty, which im­proves the part's re­sis­tance to water ingress.

ABS and ASA are smoothed with ace­tone, ap­plied as a con­trolled vapor rather than by im­mer­sion. The tech­nique is for­giv­ing on these two ma­te­ri­als: a short ex­po­sure pro­duces a light satin fin­ish, a longer one a high gloss, and the sur­face re­cov­ers its hard­ness once the resid­u­al sol­vent has fully evap­o­rat­ed, which takes time and should not be rushed. HIPS is smoothed with limonene in­stead — ace­tone at­tacks HIPS more ag­gres­sive­ly than it at­tacks ABS and tends to over-etch the sur­face. The trade-offs to weigh are that vapor smooth­ing slight­ly soft­ens fine de­tail and edges, that it mod­est­ly changes di­men­sions as the sur­face re­flows, and that both sol­vents de­mand ven­ti­la­tion and ap­pro­pri­ate han­dling — ace­tone for its flamma­bil­i­ty, limonene for its skin-sen­si­ti­za­tion po­ten­tial.

10.8 Multi-material: HIPS as breakaway support

On dual-ho­tend or IDEX hard­ware, HIPS pairs well with the poly­car­bon­ate blends as a break­away sup­port in­ter­face. The PC-to-HIPS ad­he­sion is in­ter­me­di­ate by na­ture — strong enough to hold the sup­port in place dur­ing the print, weak enough to re­lease clean­ly on cool-down with­out any dis­so­lu­tion step. A prac­ti­cal work­flow for PC Blend with HIPS break­away sup­port is a PEI or garo­lite plate pre­pared with Magi­goo PC, with HIPS used as both support body and interface at a tight but non-welded Z-gap tuned on the machine. Avoid PCTG as the PC interface: PC and copolyesters bond strongly enough that the interface can weld rather than release.

10.9 Brand landscape

ABS is a com­mod­i­ty fil­a­ment avail­able from es­sen­tial­ly every man­u­fac­tur­er, and the prac­ti­cal split is be­tween basic ABS and the im­pact-mod­i­fied or low-warp en­gi­neer­ing grades that sev­er­al ven­dors mar­ket under their own names — the lat­ter are eas­i­er to print and worth the pre­mi­um for larg­er parts. ASA has a small­er but well-es­tab­lished field: Form­Fu­tu­ra Apol­loX, Prusa­ment ASA, Fiber­l­ogy ASA, Poly­mak­er PolyLite ASA, and Over­ture ASA are rep­re­sen­ta­tive of the brand-lead­ing prod­ucts, and ASA is the grade where buy­ing a known fil­a­ment rather than the cheap­est avail­able spool most clear­ly pays off, be­cause out­door per­for­mance de­pends on the UV-sta­bi­liz­er pack­age. HIPS is wide­ly avail­able and in­ex­pen­sive; since its dom­i­nant use is as a sup­port ma­te­ri­al, spool-to-spool con­sis­ten­cy and clean limonene sol­u­bil­i­ty mat­ter more than me­chan­i­cal fig­ures when se­lect­ing it.

10.10 Application fit and current market position

Choose ABS when: the part is a cost-driv­en en­gi­neer­ing com­po­nent that needs mod­er­ate heat re­sis­tance or ace­tone vapor smooth­ing — under-hood au­to­mo­tive pro­to­typ­ing, elec­tron­ics en­clo­sures, and sim­i­lar — and an en­closed print­er is avail­able. Choose ASA when: the part will see out­door ser­vice — sprin­kler hous­ings, mark­er stakes, out­door elec­tron­ics en­clo­sures, gar­den equip­ment — where PCTG would weath­er and a poly­car­bon­ate blend would be overkill; ASA is the right an­swer for UV ex­po­sure. Choose HIPS when: a sol­u­ble or break­away sup­port is need­ed for an ABS or ASA print, or, less often, for a light cos­met­ic part. Choose some­thing else when: the part needs duc­til­i­ty, clar­i­ty, or food-con­tact com­pli­ance, or when no en­clo­sure is avail­able — PCTG is the eas­i­er en­gi­neer­ing fil­a­ment, and the poly­car­bon­ate blends cover the high­er-tem­per­a­ture and high­er-tough­ness cases. The styrenic fam­i­ly has been par­tial­ly dis­placed from desk­top FDM for gen­er­al en­gi­neer­ing use, but ABS on cost, ASA on out­door dura­bil­i­ty, and HIPS as a sup­port each re­tain a niche that the dis­plac­ing ma­te­ri­als do not fully cover.

---

← Contents · ‹ Part III — Polyester Family · Part V — Polyolefins ›