Polylactic acid (PLA) is emerging as an eco-friendly option for injection molding manufacturers. As a biodegradable thermoplastic made from renewable plant sources like corn starch, PLA offers comparable properties to traditional petroleum-based plastics. This makes it well-suited for use in the injection molding process.
In this comprehensive guide, as a professional plastic injection molding manufacturer, we’ll explore everything you need to know about using PLA for injection molding in 2025 – from material properties to processing parameters and troubleshooting tips.
Can PLA Be Injection Molded?
The short answer is yes. PLA possesses key properties that enable it to be utilized as feedstock material in injection molding manufacturing.
With impressive biodegradability and mechanical performance rivalling conventional plastics, PLA enables the cost-effective mass production of eco-conscious products via injection molding technology. Parts fabricated from PLA boast outstanding strength, resilience and aesthetic appearance – on par with those derived from traditional polymers.
As companies become increasingly committed to enacting sustainable operating practices, PLA injection molding will likely emerge as the industry standard – delivering functional, mass-produced goods without compromising environmental ideals.
Key Properties and Parameters for PLA Injection Molding
If you’re considering incorporating PLA compounds into your injection molding feedstocks, awareness of the material’s key characteristics is essential for process optimization. Here’s what you need to know:
Thermal Profile
The thermal profile of PLA differs considerably from traditional injection molding plastics:
- Glass Transition (Tg): 60°C to 65°C
- Melting Temperature (Tm): 130°C to 180°C
- Melt Index: 6 g/10 min (at 210°C, 2.16 kg)
- Decomposition Temperature: 250°C
Accordingly, maintaining melt temperatures between 150°C and 160°C is ideal. Exceeding 180°C risks thermal degradation.
Crystallization
Unlike amorphous polymers, PLA is semi-crystalline, solidifying from molten feedstocks into either amorphous or crystalline morphologies.
Amorphous PLA offers transparency and gloss, but reduced heat resistance.
Crystalline PLA delivers enhanced temperature stability and stiffness, but is more opaque.
Using specialized nucleating agents and tweaking cooling parameters enables morphology control.
Chemical Resistance
PLA exhibits susceptibility to hydrolysis and UV degradation compared to incumbent polymers like ABS, PS and PP. Accordingly, certain chemical exposures can compromise mechanical performance.
Shrinkage
PLA shrinkage averages around 3% with proper processing. However, excessive orientation from high injection pressures or inadequately designed molds risks elevated shrinkage.
Step-by-Step PLA Injection Molding Process Overview
Executing PLA injection molding requires careful control of key parameters at each phase:
1. Drying
Like most hygroscopic resins, residual moisture compromises PLA’s properties. Granule drying for 2-3 hours at 80°C with desiccant air (≤0.025% humidity) is imperative.
2. Plasticization
Transitioning dried PLA granules into a homogeneous melt within the injection barrel requires temperatures around 160°C. Excessive heat risks degradation.
3. Injection
Medium injection pressures and speeds generally produce the best PLA part quality. Slower velocities improve melt flow and knit line strength.
4. Cooling
Effective PLA part cooling requires mold temperatures around 80-105°C to enable proper crystallization. Insufficient cooling causes sticking and deformation issues.
5. Ejection
Adequate mold residence times – dictated by part thickness – ensures sufficient crystallization for dimensionally stable PLA part ejection.
Let’s explore key troubleshooting tips for each phase:
Step-by-Step Troubleshooting Guide
Despite PLA’s processing similarities with widely adopted polymers, the material’s unique attributes can trigger manufacturing defects. Here are common issues and solutions:
Splay, Jetting and Poor Melt Flow
Causes: Excessive melt temperatures causing localized viscosity variations.
Solutions: Lower barrel temperatures to 160-170°C. Increase backpressure.
Flash Formation
Causes: Overly high injection fill velocities and pressures. Inadequate mold clamping.
Solutions: Reduce injection speed and pressure. Increase mold clamp tonnage.
Voids and Sink Marks
Causes: Premature freeze off inhibiting packout. Excess moisture outgassing.
Solutions: Increase melt and mold temperatures. Improve venting. Optimize cooling design.
Warpage and Distortion
Causes: Inadequate mold surface temperatures preventing proper PLA crystallization. Excess fill/pack velocity gradients.
Solutions: Ensure mold temperature exceeds 120°C. Lower injection speed and pressures.
As with any resin, modifying parameters based on continual testing is key to realizing PLA’s maximum injection molding potential. But broadly, these guidelines spotlight critical processing considerations.
The Future of PLA Injection Molding
Thanks to growing eco-consciousness amongst consumers and OEMs, PLA compounds are emerging as a popular sustainable alternative for injection molding applications across countless industries – from automotive and aerospace through to consumer goods and medical devices.
And as technologies and expertise continue maturing, expect PLA injection molding to capture increasing materials market share over the next decade.
In particular, advances in specialized performance grades will likely address current deficiencies in heat resistance, chemical stability and toughness – exponentially expanding PLA’s range of potential applications.
The bottom line? PLA injection molding is undoubtedly viable today. And it’s only becoming more competitive as technology progresses and environmental pressures mount.
Summary
With mechanics rivaling conventional polymers, unmatched sustainability credentials and constantly improving economics, PLA injection molding ushers an eco-friendly era for mass plastics manufacturing.
Carefully respecting PLA’s unique processing requirements enables fabricators to tap into the material’s immense potential – delivering high-performing and eco-friendly products at scale.
So if you’re weighing up sustainable feedstocks for your next injection molding application, PLA undoubtedly warrants consideration. The material’s properties certify compatibility with existing manufacturing infrastructure. And its environmental impact ensures future-readiness as markets increasingly demand greener solutions.
The time for PLA injection molding is now. And it represents a new paradigm for functional, mass-produced plastic goods that don’t cost the earth.
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