Abstract

Waste tire rubber (WTR) presents a persistent environmental challenge but also offers potential as a functional filler for polymer-based additive manufacturing. This study developed and characterized pellet-printable polylactic acid (PLA)/WTR composites for conventional and 4D printing. WTR powder was treated using a nominal 6 wt% sodium hydroxide solution and incorporated into PLA at 0, 1, 3, 5, and 7 wt%. The formulations were mechanically premixed, melt-compounded, pelletized, and processed by fused granulate fabrication under constant printing conditions. Optical microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile, compression, and impact testing were conducted. Shape-memory performance was evaluated by compressing grid-infilled specimens to 40% strain and thermally activating recovery in water at 70 °C. All formulations produced continuous extrudates, suitable pelletized feedstocks and complete printed structures, confirming the feasibility of the processing route. Increasing WTR content produced greater surface heterogeneity and reduced initial degradation temperatures, although all formulations remained thermally stable above the processing range. Mechanical performance generally declined with WTR loading. At 7 wt% WTR, ultimate tensile strength, tensile toughness, compressive modulus, and absorbed impact energy decreased by 28.3%, 39.1%, 36.1%, and 18.1%, respectively, relative to the processed PLA control. The 1 wt% formulation provided the strongest mechanical-property retention. Conversely, shape fixity increased from 91.56% to 97.02%, shape recovery from 91.41% to 99.04%, and overall shape-memory effect from 83.70% to 96.09%. The results demonstrate an application-dependent trade-off: 1 wt% WTR provided the strongest overall engineering balance, whereas 7 wt% maximized shape-memory performance and waste utilization at the greatest structural cost within the investigated range.

Publication Date

8-2026

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Advisor

Wael A. Samad

Advisor/Committee Member

Salman Pervaiz

Advisor/Committee Member

Umer Javed

Comments

This thesis has been embargoed. The full-text will be available on or around 8/13/2027.

Campus

RIT Dubai

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